Multidisciplinary Design Project Mega scale 3D Printing

Multidisciplinary Design Project Mega scale 3D Printing
Multidisciplinary Design Project
Mega scale 3D Printing
James Airey, Simon Nicholls, Hinde Taleb,
Samuel Thorley, Samuel Tomlinson, Deep Upendra Hiralal
Master of Engineering
From the
University of Surrey
January 2012
Supervised by: Neil A. Downie,
Anil Fernando, Ignazio Cavarretta
MDDP – Megascale 3D Printing
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EXECUTIVE SUMMARY
The construction industry has the highest fatality and injury rate of any field of work, and yet
no significant progress has been achieved in this matter. Can 3D printing be adapted into the construction industry? There are two potential markets to enter when considering 3D printing in the
construction industry which are; the mass production of simple structures or the production of
complex bespoke designs that potentially can’t be achieved with conventional methods. The proposed solution contained in this report is based on the mass production market, as to try and
maximize the amount of profit gained. The printing therefore will be based around simple structures and the aim is to construct these in as little time as possible, thus automating the
construction industry.
The solution proposed is to carry out this idea with a large scale 3D concrete printer incorporating robotics to partially automate construction methods. It utilises a method known as contour
crafting that involves additive printing and a robotic technology to install reinforcements and
utilities. To adapt this method to the design, a concrete extrusion nozzle and a robotic arm have
been attached to a printer gantry.
The printer gantry is designed to traverse on rails allowing it to move in all three axes. This
permits it to print in any direction with no restrictions other than the size itself. Attached to the
printer head at the top of the gantry is an innovative nozzle containing a plate that allows for a
variable sized nozzle; this nozzle is responsible for the extrusion of different concrete mixes. This
facilitates the printing techniques applied which involve different concrete setting times, in this
way eliminating a lot of the concrete construction formwork as well as accelerating the whole
construction process.
Electronic and software specifications facilitate not only the general running of the printer but
also a focus has been placed on creating a safe working environment. This is achieved through the
implementation of various sensors and control systems that are beneficial over conventional systems and create a more autonomous process. Proposed designs for a structure are firstly created in
conventional CAD programs and are then exported as an STL file. This can then be opened in the
printer front end software which will convert it into instructions that the printer firmware can understand. The software controlling the printer will then use these instructions combined with the
sensor array to print an accurate structure.
The proposed design can build the main structure of a house in approximately a third of the
time conventional methods would take. It makes contracted construction labour completely rei
Nicholls, Taleb, Thorley, Tomlinson, Airey, Hiralal
MDDP – Megascale 3D Printing
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dundant, except for erection of formwork for certain elements of the structure and the finishing
aesthetics of it.
As seen in the finance section of this report, this brings overall costs down due to a faster construction time and less reliance on human labour, making this proposed method of construction a
more profitable business. For the purposes of comparison, a complete business has been modeled
for both the printed and conventional methods, and a five year financial forecast has been made
for each. This included the theoretical purchase of a real plot of land based in Brightlingsea, Essex
and a design showing the layout of the proposed houses. The finance section of this report concludes that while both the printed and conventional methods are profitable, the printed method is
more so and presents a more investible option.
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TABLE OF CONTENTS
Executive Summary .............................................................................................................. i
Table of Contents................................................................................................................. iii
List of Figures ...................................................................................................................... x
Abbreviations .................................................................................................................... xiv
1 Introduction ..................................................................................................................... 1
1.1 Project Brief ............................................................................................................ 1
1.2 Aims ........................................................................................................................ 1
2 3D printing technology ................................................................................................... 2
2.1 Printing with a Liquid .............................................................................................. 2
2.2 Printing with a Solid ................................................................................................ 2
2.3 Printing with Powder or Sand.................................................................................. 3
2.3.1 Printing Using Sand............................................................................................ 3
2.4 Method Decision ..................................................................................................... 4
3 Materials .......................................................................................................................... 4
3.1 Material Considerations........................................................................................... 4
3.1.1 Plastic ................................................................................................................. 4
3.1.2 Sand .................................................................................................................... 5
3.1.3 Metal................................................................................................................... 6
3.1.4 Concrete ............................................................................................................. 7
3.2 Concrete................................................................................................................... 7
3.2.1 Introduction ........................................................................................................ 7
3.2.2 Proposed Mix Designs........................................................................................ 8
3.2.3 Setting Time ..................................................................................................... 10
3.2.1 Influence of Temperature on Setting Time ........................................................ 11
3.2.2 Initial and Final Set Calculations ..................................................................... 12
3.2.3 Admixtures ....................................................................................................... 14
3.2.4 Pumping Concrete ............................................................................................ 17
3.2.5 Concrete Mixing ............................................................................................... 18
3.2.6 Mixing Arrangements ....................................................................................... 19
3.2.7 Concrete Fluid Mechanics ................................................................................ 22
3.2.8 Hydration Chemistry ........................................................................................ 24
3.2.9 Drying Shrinkage ............................................................................................. 26
3.2.10Cement ............................................................................................................. 27
3.3 Emergency Shutdown Procedure ........................................................................... 27
3.4 Internal Piping and Wiring .................................................................................... 28
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3.4.1 PVC Conduit and Piping .................................................................................. 29
3.4.2 Installation ........................................................................................................ 29
3.5 Support Materials .................................................................................................. 29
3.5.1 Wax ................................................................................................................... 30
3.5.2 Sand .................................................................................................................. 31
3.5.3 Paste ................................................................................................................. 31
3.5.4 Water-Soluble Material..................................................................................... 32
3.5.5 Comparison of Support Materials .................................................................... 32
3.5.6 Use of Sand as a Support Material ................................................................... 34
3.5.7 Conventional Methods ..................................................................................... 35
3.5.7.1 Slabs and Ceilings .................................................................................... 36
3.5.7.2 Windows and Doors.................................................................................. 37
4 Building Structure ......................................................................................................... 38
4.1 Introduction ........................................................................................................... 38
4.2 Design with Codes ................................................................................................. 39
4.3 Reinforcements Methods ....................................................................................... 40
4.3.1 Steel Reinforcement ......................................................................................... 40
4.3.2 Alternatives to Steel Reinforcement (Fibre-Reinforcement Polymers) ........... 41
4.3.3 Installing Reinforcement using 3D Printer ....................................................... 41
4.4 Foundations ........................................................................................................... 43
4.4.1 Types of Foundations ....................................................................................... 43
4.4.1.1 Slab Foundations ...................................................................................... 43
4.4.1.2 Crawl Space Foundation ........................................................................... 43
4.4.1.3 Basement Foundation ............................................................................... 44
4.4.2 Foundations for Printers ................................................................................... 44
4.5 Printing Aspects and Difficulties ........................................................................... 45
4.5.1 Walls and Slabs ................................................................................................ 45
4.5.1.1 Printing the Building Walls....................................................................... 45
4.5.1.2 Printing the Building Slab ........................................................................ 46
4.5.1.3 Connections between Walls and Slabs ...................................................... 47
4.5.2 Printing the foundations ................................................................................... 48
4.5.2.1 Connections with Foundations ................................................................. 48
4.5.3 Roof .................................................................................................................. 49
4.5.3.1 Printing difficulties with roof ................................................................... 49
4.5.3.2 Connections with roof .............................................................................. 50
4.6 Engineering Drawings ........................................................................................... 51
4.6.1 Estimation of Concrete Required ..................................................................... 52
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5 Printer design ................................................................................................................ 53
5.1 Nozzle Design ....................................................................................................... 53
5.1.1 Nozzle Requirements ....................................................................................... 53
5.1.2 Initial Design .................................................................................................... 53
5.1.3 Nozzle Disc Design .......................................................................................... 55
5.1.4 Connection Between the Nozzle and Valve ...................................................... 57
5.1.5 Connection Between the Nozzle and Carriage ................................................. 59
5.1.6 Nozzle Motors .................................................................................................. 61
5.1.7 Valves ............................................................................................................... 62
5.2 Use of Robotics in the 3D Printer.......................................................................... 63
5.2.1 Basic Requirements .......................................................................................... 63
5.2.2 Robotic Arm Selection ..................................................................................... 64
5.2.3 Part Selection.................................................................................................... 66
5.3 Printer Structure..................................................................................................... 69
5.3.1 X Axis ............................................................................................................... 73
5.3.2 Y Axis ............................................................................................................... 75
5.3.3 Z Axis ............................................................................................................... 76
5.3.4 Cable and Piping Management ......................................................................... 77
5.3.5 Printer Structure Discussion ............................................................................. 77
6 Printer Structure Analysis ............................................................................................. 79
6.1 Stress Analysis ....................................................................................................... 79
6.1.1 Carriages........................................................................................................... 79
6.1.2 V Bearings ........................................................................................................ 83
6.1.3 Bearing Blocks ................................................................................................. 84
6.1.4 V-Slides ............................................................................................................ 86
6.1.5 Beams ............................................................................................................... 87
6.1.6 Pinions .............................................................................................................. 89
6.2 Beam Vibrational Analysis .................................................................................... 91
6.3 Beam Deflection Analysis ..................................................................................... 93
6.4 Fatigue Analysis .................................................................................................... 94
6.5 Part Life Analysis .................................................................................................. 95
6.6 Analysis Conclusion .............................................................................................. 97
7 Protection and Transportation of Printer ....................................................................... 97
7.1 Environmental Protection ...................................................................................... 97
7.2 Printer Assembly and Transportation .................................................................... 98
8 Electronics ..................................................................................................................... 99
8.1 Motors ................................................................................................................... 99
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8.1.1 Motor requirements .......................................................................................... 99
8.1.2 Parameters ...................................................................................................... 100
8.1.2.1 X-Axis – Nozzle & Robotic Arm Motion............................................... 101
8.1.2.2 Z-Axis – Vertical Motion ........................................................................ 102
8.1.2.3 Y-Axis – Horizontal Motion ................................................................... 102
8.1.3 AC vs DC ....................................................................................................... 103
8.1.4 Servomotors ................................................................................................... 103
8.1.5 Motor choice .................................................................................................. 104
8.1.6 X-Axis – Nozzle & Robotic Arm Motion: ..................................................... 104
8.2 Sensors................................................................................................................. 104
8.2.1 Equipment safety ............................................................................................ 105
8.2.2 Precision ......................................................................................................... 105
8.2.3 Motion detectors ............................................................................................. 105
8.2.4 Position sensor................................................................................................ 106
8.2.5 Temperature sensors ....................................................................................... 106
8.2.6 Flow sensors ................................................................................................... 108
8.2.7 Accelerometer ................................................................................................ 109
8.2.1 Current Sensor ................................................................................................. 110
8.2.2 Sensor Selection .............................................................................................. 110
8.3 Electronic Systems Diagram ................................................................................ 110
8.3.1 Motor Control .................................................................................................. 110
8.3.2 Sensors ............................................................................................................ 111
8.3.3 Nozzle.............................................................................................................. 111
8.3.4 Robotic Arm .................................................................................................... 111
8.3.5 Motion Sensing ............................................................................................... 111
8.3.6 Master MCU .................................................................................................... 111
8.4 Power .................................................................................................................... 113
9 Software ....................................................................................................................... 113
9.1 STL File ................................................................................................................ 114
9.1.1 STL FORMAT ................................................................................................. 114
9.1.2 Colour in Binary STL ...................................................................................... 114
9.2 G-Code ................................................................................................................. 115
9.2.1 High Level Block Diagram ............................................................................. 116
9.3 CAD...................................................................................................................... 116
9.4 G-Code Converter ................................................................................................ 116
9.5 Printer Front End Software ................................................................................... 117
9.6 Printer Firmware ................................................................................................... 118
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9.6.1 Movement........................................................................................................ 118
9.6.1.1 Rapid Motion ........................................................................................... 119
9.6.1.2 Linear Interpolation ................................................................................. 119
9.6.1.3 Circular Interpolation ............................................................................. 120
9.6.2 Sensor Software.............................................................................................. 121
9.6.3 Machine Vision............................................................................................... 122
9.6.3.1 Motion Detection .................................................................................... 125
9.7 Fail Safe ............................................................................................................... 127
9.8 Pausing the Print .................................................................................................. 128
9.9 Class Diagram ..................................................................................................... 128
10 Building Finish ............................................................................................................ 130
10.1 Insulation ............................................................................................................. 130
11 Sustainability ............................................................................................................... 131
11.1 Concrete............................................................................................................... 131
11.2 Roof ..................................................................................................................... 132
11.3 Printer Structure................................................................................................... 132
12 Legal Considerations ................................................................................................... 133
12.1 Building Regulations and Planning Permission .................................................. 133
12.2 Contracts .............................................................................................................. 134
13 Finance ........................................................................................................................ 134
13.1 Land Planning...................................................................................................... 134
13.2 3D Printer Method ............................................................................................... 137
13.2.1Profit and Loss Account ................................................................................. 137
13.2.1Cash Flow Statement ...................................................................................... 139
13.3 Conventional Method .......................................................................................... 141
13.3.1Profit and loss account ................................................................................... 141
13.3.1Cash Flow Statement ...................................................................................... 142
13.4 Financial Comparison .......................................................................................... 143
14 Risk assessment ........................................................................................................... 144
14.1 HAZOP Analysis ................................................................................................. 144
14.2 Failure Mode Effects Analysis ............................................................................ 146
14.3 Site Health and Safety Analysis .......................................................................... 146
15 Project management .................................................................................................... 147
16 Future Development .................................................................................................... 149
16.1 Part Automatic Assembly .................................................................................... 149
16.2 Removal of Labour .............................................................................................. 149
16.3 Alternative Material............................................................................................. 150
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17 Conclusion................................................................................................................... 150
18 Bibliography ................................................................................................................ 152
19 APPENDIX 1 – Part Specification.............................................................................. 160
19.1 X Axis .................................................................................................................. 160
19.1.1X001 X Axis Beam........................................................................................ 160
19.1.2X002 V Slide with Gearing Teeth ................................................................. 160
19.1.3X003 V Slide without Gearing Teeth ............................................................ 161
19.1.4X004 Carriage Plate ...................................................................................... 161
19.1.5X005 Robotic Arm Motor .............................................................................. 162
19.1.6X006 Nozzle Motor ........................................................................................ 163
19.1.7X006 Drive Flange & Pinion......................................................................... 164
19.1.8X007 Buffer ................................................................................................... 164
19.1.9X008 Bearings .............................................................................................. 165
19.2 Y Axis .................................................................................................................. 165
19.2.1Y001 Flat Track with Teeth ............................................................................ 165
19.2.2Y002 Flat Track without Teeth ...................................................................... 166
19.2.3Y003 Carriage Plate ...................................................................................... 166
19.2.4Y004 Motor .................................................................................................... 166
19.2.5Y005 Bearing Block (Right Side) ................................................................. 167
19.2.6Y006 Bearing Block (Left Side) ................................................................... 167
19.2.7Y007 Drive Flange with Pinion..................................................................... 167
19.2.8Y008 Mounting Plate ..................................................................................... 167
19.3 Z Axis .................................................................................................................. 167
19.3.1Z001 Y Axis Bar ............................................................................................. 167
19.3.2Z002 V Slide with Gearing Teeth .................................................................. 168
19.3.3Z003 V Slide without Gearing Teeth ............................................................. 168
19.3.4Z004 Carriage Plate ....................................................................................... 168
19.3.5Z005 Motor ................................................................................................... 168
19.3.6Z006 Drive Flange with Pinion ..................................................................... 168
19.3.7Z007 Buffer ................................................................................................... 168
19.3.8Z007 Bearings ............................................................................................... 168
20 Appendix 2 – C++ code Linear INterpolation ............................................................ 169
21 Appendix 3 – Additional Calculations ........................................................................ 170
21.1 Estimation of Concrete Required ........................................................................ 170
21.1.1Exterior Walls ................................................................................................. 170
21.1.2Interior Walls .................................................................................................. 171
21.1.3First Floor Slab ............................................................................................... 172
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21.1.4Roof ................................................................................................................ 172
21.1.5Foundations .................................................................................................... 173
21.1.6TOTAL SLOW SETTING CONCRETE VOLUME...................................... 173
21.1.7TOTAL FAST SETTING CONCRETE VOLUME ....................................... 173
21.2 Concrete Mixing Calculations ............................................................................. 174
22 Appendix 4 – Concrete Fluid Mechanics ................................................................... 175
22.1 Fast Setting Mix Calculations ............................................................................. 175
22.2 Slow Setting Mix Calculations ............................................................................ 176
23 Appendix 5 – Additional Drawings ............................................................................. 178
23.1 Reinforcement Drawings ..................................................................................... 178
23.1.1Reinforcement Parts ....................................................................................... 178
23.1.2Reinforcement Corner Layout ........................................................................ 179
23.1.3Reinforcement Slab or Foundation Layout .................................................... 180
24 Appendix 6 – Finance sheets....................................................................................... 181
24.1 Printed Method Profit and Loss Year One ........................................................... 181
24.2 Printed Method Profit and Loss Year Two........................................................... 182
24.3 Printed Method Profit and Loss Year Three ........................................................ 183
24.4 Printed Method Profit and Loss Year Four .......................................................... 184
24.5 Printed Method Profit and Loss Year Five .......................................................... 185
24.6 Printed Method Salaries and Contractor Wages .................................................. 186
24.7 Printed Method Five Year Cash Flow Statement ................................................. 188
24.8 Conventional Method Profit and Loss Year One ................................................. 189
24.9 Conventional Method Profit and Loss Year Two ................................................. 190
24.10
Conventional Method Profit and Loss Year Three ........................................ 191
24.11Conventional Method Profit and Loss Year Four ................................................ 192
24.12
Conventional Method Profit and Loss Year Five........................................... 193
24.13
Conventional Method Salaries and Contractor Wages .................................. 194
24.14
Conventional Method Five Year Cash Flow Statement ................................. 196
25 Appendix 7 – Materials Lists ...................................................................................... 197
26 Appendix 8 – Risk Assessment Tables ........................................................................ 200
26.1 HAZOP Tables..................................................................................................... 200
26.2 Failure Mode Effects Analysis ............................................................................ 204
26.2.1FMEA Ratings ................................................................................................ 204
26.2.1.1 Occurrence Rating .................................................................................. 204
26.2.1.2 Severity Rating ....................................................................................... 204
26.2.1.3 Detection Rating ..................................................................................... 205
26.2.2FMEA Tables .................................................................................................. 206
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26.3 Site Health and Safety Analysis .......................................................................... 212
27 Appendix 9 – Project Management ............................................................................. 215
27.1 Initial Gantt Chart ................................................................................................ 215
27.2 Final Task List ..................................................................................................... 216
28 APPendix 10 – Floor plans ......................................................................................... 219
LIST OF FIGURES
Figure 1 – Contour Crafting Process (Khoshnevis B. , 2004) .......................................................... 3
Figure 2 - Effect of Temperature on Initial and Final Setting Times of the 20% Class F Fly Ash
Concrete Mix (Wade, Nixon, Anton K. Schindler, & and Robert W. Barnes, 2010). ............. 12
Figure 3 - Dual Piston Pump Ball Valve and Surge Chamber Arrangement (Schwing). ................ 18
Figure 4 - Process Flow Diagram ................................................................................................... 21
Figure 5 - Rate of Hydration as a Function of Time According to Isothermal ............................... 25
Figure 6 - Formwork for Slabs and Ceiling .................................................................................... 36
Figure 7 - Typical Window Frame or Buck (ARXX ICF, 2012) .................................................... 38
Figure 8 - Reinforcements for Slab ................................................................................................ 41
Figure 9 - Types of Foundations (Basement Insulation, 2011) ....................................................... 44
Figure 10 - Foundation for Printer.................................................................................................. 44
Figure 11 - Exterior Wall Layout .................................................................................................... 45
Figure 12 - Top View of Wall Opening .......................................................................................... 46
Figure 13 - 3D View of Wall Opening, with and without Beam .................................................... 46
Figure 14 - Top View of Slab Reinforcement Layout .................................................................... 47
Figure 15 - Side View of Slab to Wall Connection ......................................................................... 48
Figure 16 - Walls to Foundation Connection (CCANZ, 2012)....................................................... 49
Figure 17 - Flat Roof Layout .......................................................................................................... 50
Figure 18 - Roof Connection Details (ARXX, 2012) ..................................................................... 50
Figure 19 - Salt container with various dispensing options ............................................................ 54
Figure 20 - Preliminary Design for Nozzle Array Setup ................................................................ 54
Figure 21 - Drawing of Nozzle ....................................................................................................... 55
Figure 22 - Cross-Sectional View of Connection Between Nozzle and Valve ............................... 57
Figure 23 - Force Diagram of Nozzle ............................................................................................. 58
Figure 24 - Forces Acting on Bearing ............................................................................................ 59
Figure 25 - Layout of Screw-Driven Linear System ...................................................................... 60
Figure 26 - Drawing of Nozzle Movement Mechanism ................................................................. 61
Figure 27 - Positions of a Three-Way Ball Valve (Wikipedia, 2010) ............................................. 62
Figure 28 - Layout of Components on Main Carriage ................................................................... 63
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Figure 29 Axis of movement of typical robotic arm (Global Robots Ltd, 2011) ........................... 64
Figure 30 - Working Range of ABB IRB 140 (ABB, 2012)........................................................... 64
Figure 31 - MIG Welding Layout (Weldguru, 2013) ...................................................................... 66
Figure 32 - Average Sized UK House Dimensions ........................................................................ 69
Figure 33 - Comparison of Initial Printer Design Concepts ........................................................... 70
Figure 34 - Illustration of the Mass Producing Capabilities of the Printer. .................................... 71
Figure 35 - Axes of Printer ............................................................................................................. 71
Figure 36 - Initial Concept Design of Proposed Solution............................................................... 72
Figure 37 - X-Axis System ............................................................................................................. 73
Figure 38- Comparison Between Flat and V-Shaped Bearings ...................................................... 74
Figure 39 - Y-Axis System. ............................................................................................................ 75
Figure 40 - Z-Axis System. ............................................................................................................ 77
Figure 41 - Complete Printer Structure Drawing ........................................................................... 78
Figure 42 - Forces and Moments on the Carriage (Hepcomotion) ................................................. 80
Figure 43 - Carriage Holding Robotic Arm for Ms Calculation. .................................................... 81
Figure 44 – Moment (M) Calculation for Z004 Carriage ............................................................... 82
Figure 45 - Loads on Bearings (Hepcomotion) .............................................................................. 83
Figure 46 - Loads on bearing blocks (Hepcomotion) ..................................................................... 85
Figure 47 - Loads on v-slides (Hepcomotion). ............................................................................... 86
Figure 48 – Stress Analysis Results for X001 Beam using ANSYS .............................................. 88
Figure 49 - Stress Analysis Results for Z001 Beam using ANSYS ............................................... 89
Figure 50 - Stress Analysis Results for Z-Axis Pinions using ANSYS .......................................... 90
Figure 51 - Simplified diagram of the HB33 bar supplied by HepcoMotion. ................................ 91
Figure 52 - Diagram Used for Deflection Analysis to Show Built in Set-Up of HB33 Beam
Supplied by Hepcomotion. ..................................................................................................... 93
Figure 53 - Loadings Which Could Cause Fatigue Cracks (Non Destructuve Testing Resource
Centre, 2013) .......................................................................................................................... 95
Figure 54 – Environmental Containment Project - North East, United States (Big Top
Manufacturing, 2012) ............................................................................................................. 98
Figure 55 - Graph Showing Motor Torque - Speed Relationships (Magnetic Spa, 2012) ............ 100
Figure 56 - Servomechanism Diagram ......................................................................................... 103
Figure 57: Dynamic Winding and Case Temperature of a Motor (Motors Drives) ...................... 107
Figure 58 - Electronic Systems Diagram ...................................................................................... 112
Figure 59 - High Level Software Block Diagram ........................................................................ 116
Figure 60 - Example of the printer software user interface. ......................................................... 117
Figure 61 - Example of Linear Interpolation ................................................................................ 120
Figure 62 - Example of Circular Interpolation ............................................................................. 121
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Figure 63 - Different Types of Lighting Conditions for Machine Vision ..................................... 123
Figure 64 Steps for Visual Information Processing (Cho, 2006) .................................................. 124
Figure 65 - Motion Detection Example (Reference Frame) ......................................................... 126
Figure 66 - Motion Detection Example (No Reference Frame) ................................................... 126
Figure 67 - Motion Detection Canny Edge Detection Example ................................................... 127
Figure 68 - Class Diagram ............................................................................................................ 129
Figure 69 - Lot 2, Robinson Road, Brightlingsea, Essex. ............................................................ 135
Figure 70 - Master Plan of the First Three Years for Lot 2, Robinson Road, Brightlingsea, Essex.
.............................................................................................................................................. 135
Figure 71 – Comparison of EBIT for Printed and Conventional Methods ................................... 143
Figure 72 – Extrapolation of EBIT for Printed and Conventional Methods ................................ 143
Figure 73 –Comparison of NPV for Printed and Conventional Methods..................................... 144
Figure 74 - Severity Ratings for Risk Assessment ....................................................................... 147
Figure 75 - Final Gantt Chart Depicting Work Carried Out ......................................................... 148
Figure 76 – Hydraulic Telescopic Axis (House Printing Animation, 2011) ................................. 149
Figure 77 - Reinforcement Node in Walls .................................................................................... 178
Figure 78 - Reinforcement Staple................................................................................................. 178
Figure 79 - Reinforcement Connector for Slabs ........................................................................... 179
Figure 80 - Reinforcement Corner Layout ................................................................................... 179
Figure 81 - Reinforcement Slab or Foundation Layout ................................................................ 180
Figure 82 - House Bottom Floor Plan .......................................................................................... 219
Figure 83 - House Second Floor Plan........................................................................................... 220
Figure 84 - House Elevations ....................................................................................................... 221
Figure 85 - 3D Drawing of House ................................................................................................ 222
LIST OF TABLES
Table 1 - The Composition of the Denser HPC in Terms of Weight Percentage (T.T. Le, 2011) ..... 9
Table 2 - The Composition of the Less Dense HPC in Terms of Weight Percentage ..................... 10
Table 3 - Setting Times at Various Temperatures ........................................................................... 12
Table 4 - Physical Properties of Silica Fume (Khan, 2011). ........................................................... 15
Table 5 - Chemical composition of cement CEM I 52,5 and fly ash (T.T. Le, 2011). .................... 16
Table 6 - X-Axis Parts List. ............................................................................................................ 73
Table 7 - Y-Axis Parts List.............................................................................................................. 75
Table 8- Z-Axis Parts List .............................................................................................................. 76
Table 9 - Carriage specification for AURD12833W (Hepcomotion), Maximum Loads and
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Moments. ................................................................................................................................ 79
Table 10 - Loads and moments applied to all carriages used for the printer. ................................. 82
Table 11 - Bearing specification for HJ128 (Hepcomotion), Maximum Loads and Basic Life. .... 83
Table 12 - Loads Applied to all Bearings Used for the Printer. ...................................................... 84
Table 13 – Bearing Block Specification for MHD89B (Hepcomotion), Maximum Loads. ........... 85
Table 14 - V-slide specification for HSS33 (Hepcomotion), maximum loads. .............................. 86
Table 15 - Loads applied to all v-slide systems used for the printer. .............................................. 87
Table 16 - Life of each carriage and v-bearing system. .................................................................. 97
Table 17 - Motor Parameter Definitions ....................................................................................... 100
Table 18 - Motor Requirements .................................................................................................... 101
Table 19 – Comparison of Types of Motor ................................................................................... 104
Table 20 - Chosen Motor Parameters ........................................................................................... 104
Table 21- Specifications of Flow Sensors .................................................................................... 109
Table 22 - Selected Sensors and Prices ........................................................................................ 110
Table 23- Calculated Values for Linear Interpolation Example ................................................... 120
Table 24 – 3D Printer Employee List for Year 1, Including Yearly Salaries ................................ 137
Table 25 – 3D Printer Contractor List for Year 1, Including Daily Salary ................................... 138
Table 26 – Houses Built, Sold and Unsold Per Year .................................................................... 139
Table 27 – 3D Printer Cash Flow Statement for 5 Years .............................................................. 140
Table 28 – Conventional Methods Employee List for Year 1, Including Yearly Salaries ............ 141
Table 29 – Conventional Methods Contractor List for Year 1, Including Daily Salary ............... 141
Table 30 - Conventional Method 5 Year Cash Flow Statement .................................................... 142
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ABBREVIATIONS
AC
Alternating Current
BPM
Ballistic Particle Manufacture
CAD
Computer Aided Design
DC
Direct Current
DMA
Differential Motion Analysis
EBIT
Earnings Before Income Tax
EPS
Expanded Polystyrene
EXS
Extruded Polystyrene
FDM
Fused Deposition Modelling
FMEA
Failure Mode Effects Analysis
FRP
Fibre Reinforced Polymers
GMAW
Gas Metal Arc Welding
HAZOP
Hazard and Operability
HBV
Hydraulic Ball Valve
HCN
Hydrogen Cyanide
HPC
High Performance Concrete
IR
Infra-Red
LED
Light Emitting Diodes
LF
Load Factor
LOM
Layered Object Manufacturing
LTP
Liquid Thermal Polymerization
MCU
Micro Controller Unit
MIG
Metal Inert Gas
NPV
Net Present Value
PPE
Personal Protective Equipment
PVA
Poly-Vinyl Alcohol
PVC
Poly-Vinyl Chloride
PWM
Pulse Width Modulation
STL
Stereolithography
SLS
Selective Laser Sintering
VIP
Vacuum Insulation Pannels
W/C
Water-Cement
3D
Three Dimensional
xiv
MDDP – Megascale 3D Printing
Group 2
1 INTRODUCTION
1.1
Project Brief
The brief of this project is to produce an innovative method of 3D printing which would allow
the manufacture of a building that has been designed using only a Computer Aided Design (CAD)
model. In recent years additive manufacturing has made more complex designs possible and
adapting this technology to run on a larger scale could provide an alternative to conventional
building methods at relatively low cost. So far ceramics, metals, polymers, certain plastics and
concrete have been successfully printed and one of the challenges of this project is incorporating
various different materials into the construction process. The printer itself is the main component
of the research and will need to be designed as fully as possible to ensure it has the functionality
necessary to print the most intricate of designs whilst maintaining satisfactory mechanical properties.
1.2
Aims
In this project, a large-scale 3D printer must be designed and constructed. This printer will be
able to construct a building in a more efficient manner than current construction methods. The aim
is to provide a process that is cheaper and faster and that gives more options to new building designs. The financial side of the project will have to be monitored closely and it will have to be
determined whether the proposed additive manufacturing method is cost effective when compared
with traditional building methods. This report will focus mostly on mass construction housing but
it can be adapted to other types of construction. In theory the printer will be able to print a row of
houses during the same print in a relatively short period of time.
One of the main challenges in printing on a large scale is ensuring the project provides a fully
automated process that is producing the desired structure based on the CAD model. The printer
itself must be automated and it is necessary to ensure that a system is in place to supply the chosen design materials to the printer head at the desired rate. It is also important to consider the
logistics of installing the internal features necessary within structure. Plumbing and electrical wiring will both need to be included in the design and fitted automatically as fitting them manually
during the printing process could prove to be hazardous.
The sustainability of the process is also something that is extremely important. Any potential
material must have had its sustainability considered as well as any financial ramifications.
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,
MDDP – Megascale 3D Printing
Group 2
2 3D PRINTING TECHNOLOGY
3D printing is a technology that is gaining huge popularity in the modern world. It is currently
used for relatively small-scale products or prototyping. A major advantage of 3D printing is that it
can construct a complete object in which previous methods would have used pieces joined
together. This creates a resulting object that is stronger.
3D printing can be split into three different categories: Printing with liquid, printing with solid
and printing with powder or sand.
Printing with a Liquid
2.1
When using a liquid for printing, the liquid is stored in a big vat and a movable platform just
below the surface is used. The object is created layer by layer by solidifying the liquid using rays
of light. The platform is lowered after a layer is created and the process is repeated until the object
is complete. 3D printing techniques using liquid include:
-
Stereolithography (SL) - Uses a photosensitive monomer resin that, when exposed to
ultraviolet light, turns into a solid through the creation of polymers in the material (D.T.
Pham, 1998).
-
Liquid Thermal Polymerization (LTP) - Similar to Stereolithography but it uses an
Infra-Red (IR) laser to polymerize thermo-setting plastics. The main issue with LTP is
that the shape of the object might change after cooling down (D.T. Pham, 1998).
2.2
Printing with a Solid
3D Printing using a solid material can be done in various ways. A frequently used method is
Fused Deposition Modelling (FDM). The respective material is heated to just above its melting
point by a heating element (liquefier) contained in an extrusion head and is deposited in semiliquid form, layer by layer onto a build platform. A support material can also be used which has a
separate nozzle to print a removable material in order to support overhangs and particularly thin
sections of the model. This support material is removed after completion, leaving the intended 3D
model behind (Cooper, 2001).
Another method similar to FDM is called Ballistic Particle Manufacture (BPM) where the
object is created by shooting droplets of molten material, with a nozzle or a jet, onto a fixed
surface. The nozzle only moves horizontally; it is the support that is lowered each time a layer is
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MDDP – Megascale 3D Printing
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produced. The droplets then bind together when cooling (D.T. Pham, 1998).
With the Layered Object Manufacturing (LOM) process, an object is made from sheets of a
specific material. The sheet of material is loaded on to a platform and then bound to a substrate
using a heated roller. A laser is then used to cut the cross section of the layer and the material that
is not required is removed (D.T. Pham, 1998).
Contour crafting is the method that is the most construction oriented. It uses the conventional
construction tools (trowels) to shape the different layers. As shown in Figure 1, a nozzle extrudes
the material and two trowels shape the layer. A property of the nozzle is that it can build with two
different materials at the same time (Khoshnevis B. , 2004).
Figure 1 – Contour Crafting Process (Khoshnevis B. , 2004)
Contour crafting creates a lot of possibilities in construction. It can be arranged to add
reinforcement simultaneously to printing the structure. Subsequently, gaps can be created to insert
the electrical system or plumbing with a robotic arm.
2.3
Printing with Powder or Sand
3D printing can be achieved using powders which can be used to print metal objects. The
process is lengthy in comparison to most other processes and contains many steps in production.
An example of printing with a powder is Selective Laser Sintering (SLS).
SLS creates an object from a polymer powder. The powder is preheated and a laser beam then
heats the powder further until it reaches its melting point so that the powder can then be bound
into the desired shape (D.T. Pham, 1998). Once the layer is complete the support holding the
object is then lowered and a roller is used to level the powder in order for the next layer to be
printed.
2.3.1
Printing Using Sand
Using sand to create objects is a fairly common occurrence in industry with sand moulds being
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created for use in the casting process. Some of these moulds use materials such as resins or
organic binders to harden the sand into a fixed shape. These are typically known as ‘dry sand
moulds’ or ‘no-bake moulds’. This method has already been utilised in large scale 3D printing in
the form of ‘D-Shape’. D-Shape is already being marketed as a 3D printer capable of printing
buildings with many claimed advantages (D Shape - The Technology).
2.4
Method Decision
The decision behind the method of 3D printing is an important one as it defines the outline
of the whole design project. The method above that most closely resembles the chosen method of
3D printing is contour crafting.
The reasons against using a powder based printing method is the complexity of the process and
as it is time consuming it does not fit into a mass production product. Using a liquid based
solution does not present itself well for being scaled up to such a large size as for the construction
of a building due to the need for very large vats of the polymer liquid (D.T. Pham, 1998).
The decision to use a form of contour crafting was therefore chosen due to its simplistic
nature, theoretical compatibility with many materials and the strong links to.
3 MATERIALS
This section of the report will discuss the reasons behind the selection of a suitable material for
the structure to be printed. Many of the materials considered are either proven in the 3D printing
industry or the construction industry but not both. This means that finding a material that most
suits both applications will be critical to the success of this project.
3.1
Material Considerations
The materials considered for the material of the structure were; concrete, plastic, metal and
sand. The arguments for and against each proposed idea will be covered in this section in detail.
The chosen material will then be covered in more detail following these decisions.
3.1.1
Plastic
Plastic is an obvious option for 3D printing, methods such as fused deposition modelling and
selective laser sintering produce plastic models and so research was done into the feasibility of
building a structure from plastic.
When building structures from plastic the emphasis is usually on recycling previously used
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plastic such as bottles and re using them for a building. An interesting company called Miniwiz
has invented a method that takes plastic bottles and re-engineers them into durable plastic bricks
called Polli-bricks. These bricks can withstand earthquake tremors, strong winds and are
extremely good insulators due to the large pocket of air within (Miniwiz). While not completely
transparent the bricks also allow a good proportion of light in which will also save energy through
a smaller reliance on artificial light. The process behind creating Polli-bricks however, is very
intensive and requires engineers to check each one in order to assess their build quality and
suitability. The process for creating them is also very long and has many steps, and is a further
argument that the bricks themselves would not be suitable for a printing process. The positive
argument here however is that the use of recycled plastic to build structures is an extremely
environmentally friendly method.
A major downside to potentially using plastic to build a structure is the fact that many plastics
react to various products that can be found around the home; for example bleach. This could
damage the material which is a huge safety concern when the structure is built entirely from
plastic.
Using plastic as the material also has the potential to be extremely expensive. Evidence was
found that a 1kg spool of ABS plastic (a commonly used plastic for 3D printing) costs £34 (ABS).
This spool is 3mm in diameter and the practicalities of building a structure from this will prove to
be very difficult as well as expensive.
As well as expense, there would be a large amount of pressure on how environmentally
friendly the process was if the material used was plastic. As previously mentioned, many of the
structures built from plastic make use of recycled plastic, which of course is environmentally
friendly. If the 3D printing of structures was to gain popularity however, the demand for recycled
plastic could outweigh the supply. This would mean using non recycled plastic which has several
downsides in terms of the environmental impact.
Plastic therefore is a good option for printing as the material has been used for many years
previously; however there are several issues raised when considering whether it is suitable for
building a large structure, and therefore it will not be considered for this project.
3.1.2
Sand
The use of sand has already been proven in a structural sense as sand structures have been used
for centuries. Sand has also been used in early development work for printing with an example
being the company D-Shape. D–Shape use a process that lays down a layer of sand and then
sprays the layer with a magnesium based binder which sticks the next layer down on top of the
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first. This process continues until the object is completed (D Shape - The Technology). This
process is cheap as a fairly large sculpture was created for £60 and therefore entire structures
shouldn’t cost much more than this. The strength of the structure however and it’s suitability in
construction is questionable. The creator of D-Shape claims “The binder transforms any kind of
sand into a marble-like material and with a resistance and traction much superior to Portland
Cement, so much so that there is no need to use iron to reinforce the structure” (D Shape - The
Technology). However, there was very little evidence found to support these claims. The process
is also fairly slow as it takes weeks to produce a small structure, which includes finishing the
structure by hand. The printer designed in this project should be as autonomous as possible in
order to fit within the mass production market chosen, and due to the already patented design of
the sand printer, it could be an expensive option.
While sand can be printed using a relatively easy method, the group were sceptical about the
claims made about the strength of the material created and whether it would be suitable for a large
scale building. Added to this, sand is not a popular option for conventional buildings and there are
also patents surrounding the design of the sand printer suggesting that this could turn into an
expensive option if licensed. Sand therefore will not be considered any further in this project.
3.1.3
Metal
Metal is not a good choice for either structural or printing reasons in reference to producing
large structures. The main method of printing metals, as discussed previously uses a powder as a
material with the process being very time consuming and containing many steps. This is not ideal
when scaling a printer to such a large size as one of the main objectives is to create a more time
efficient way of building structures. In addition to this the complex method behind printing metals
does not lend itself well when thinking in terms of printing large structures, such as a house. The
powder used (different metal compounds) is also very costly and when visiting 3T, a company
who print metal objects, it was quoted that a small tub of the metal compound costs approximately
£2500 (3T). If this was to be scaled up in order to print a building the costs for the powder alone
would far outreach that of the total cost using conventional methods to produce a building.
In terms of structure, building a house out of metal is also not ideal. One reason for this is the
noise pollution for example the noise produced when raining on a metal surface. Another more
major reason would be the large cost behind producing a structure completely out of metal and the
complexity behind the construction of a metal building. It is for these reasons therefore that metal
will not be considered for this project.
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3.1.4
Group 2
Concrete
Structurally concrete is the material of choice as it is already widely used in construction and
there are ample amounts of highly developed technologies for this material.
The use of concrete for the project therefore is subject to how well it can be printed by a large
scale 3D printer. There is already research and development behind printing with concrete
including Loughborough University who have written a paper on the process with exciting results
(Lim, et al.). The method most suited to the project as previously discussed is contour crafting.
Contour crafting can be used with concrete and a series of trowels that can then shape the
extruded concrete to the desired shape. To be able to achieve this, a high powered pump will be
required of which initial research showed that they were readily available.
Concrete has been chosen therefore due to its dominance in the construction industry and due
to the fact that the concept of printing concrete has already been proven. This makes it the
material of choice as it satisfies the questions; can the material be printed and does it perform well
structurally?
3.2
Concrete
3.2.1
Introduction
This particular material was chosen as the main material of construction for the project. It has
been proven in the construction industry and dates way back to the roman era. High performance
concrete (HPC) is known for its relatively high compressive strength and a much lower tensile
strength, for this reason reinforcements are necessary within the structure (Shah & Ahmad, 1994).
Steel reinforcements are most common and have been favoured for this project due to its superior
strength in tension. Alternative support materials are available however, such as fibre-reinforced
concrete.
The nature of this project presents some fresh challenges to those of conventional building
projects that use concrete. The mix design is always of great importance, however, when printing
with HPC the mix design is even more significant. In this instance the concrete has to pass
through either a 3 or 7cm nozzle; this differs from conventional methods where concrete is poured
into place. Firstly, the sand particles used in the concrete mixture must be small enough to ensure
that the concrete can pass through the nozzle without causing a blockage. Secondly, the mix
design has to provide sufficient workability in order for the concrete mix to be pumped up to the
top of the printer structure and then pass through the intricate pipework within the printer head. As
well as this, the concrete has to have a reasonably quick setting time and needs to show sufficient
buildability. If the concrete mix is more viscous it may set quickly but it will be difficult to pump
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MDDP – Megascale 3D Printing
Group 2
up from ground level to the printer head. On the other hand if the mix is less viscous it will be
easier to pump but it will more than likely have a longer setting time.
An issue to consider on the subject of setting concrete is the time required for a full layer to be
printed. Previous studies (T.T. Le, 2011) have shown that leaving 30 minutes between layers
provides significantly lower tensile bond strength than a printing gap of 15 minutes; this is
understandable as a reduced printing gap allows for greater adhesion between layers of concrete.
Another factor to consider in the design process is that when using HPC as a material it is
necessary to use support materials when printing horizontally or on a slope. However, providing
the mix design is optimised bearing in mind buildability and workability then the concrete will be
self-supporting when printing vertically.
3.2.2
Proposed Mix Designs
Mix design is one of the key aspects of this project as it directly effects concrete setting time
and therefore printing time. It is also vital that the mix design meets the structural mechanical
property requirements in its hardened state as varying the mix design will alter the compressive
and tensile strength of the structure. The mix design (w/b ratio in particular) is also the main
influence on the workability and ultimately the pumpability of fresh concrete. Another important
issue to consider with this project is that two separate mix designs are required with different
setting times. This is necessary as special arrangements have to be made in order for the steel
reinforcements to be laid within the structure. Given that there will be two different setting times
and the less viscous (higher w/c ratio) concrete will be printed after 7 layers (21cm) of the more
viscous concrete it is vital to ensure there is sufficient time for the two different types of concrete
to bond cohesively before either mix reaches initial set.
1) Denser HPC Mix Design

3:2 sand-binder ratio (sand aggregate contains no particles larger in diameter than 2mm)

Binder: 70% cement, 20% fly ash and 10% silica fume

1.2kg/m3 micro polypropylene fibres (12/0.18mm in length/diameter)

0.26 water-binder (w/b) ratio

1% polycarboxylate-based superplasticiser and 0.5% retarder (amino-tris, citric acid and
formaldehyde)
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Table 1 - The Composition of the Denser HPC in Terms of Weight Percentage (T.T. Le, 2011)
Component
Sand
Cement CEM I 52,5
Class F Fly Ash
Silica Fume
Water
Polypropylene
Superplasticiser
Retarder
Composition (wt. %)
53.5
25.0
7.1
3.6
9.3
0.05
1.0
0.5
The w/b ratio appears a little low (0.26) as does the w/c ratio (0.37) and if ignored this may
cause workability and pumpability issues as there is a general rule in concrete pumping that w/c
ratios lower than 0.4 should not be used when pumping is necessary. This is why a
superplasticiser is used in the mix design as this component has been proven to reduce the w/c
ratio significantly whilst maintaining flow properties therefore the workability is maintained. The
retarder is another admixture included in the design as this provides the fresh concrete with a
sufficient ‘open time’ (up to 100 minutes) and allows a constant flow to be achieved during
printing i.e. the retarder prevents the concrete from setting during printing (T.T. Le, 2011).
The sand aggregate used contains no particles larger than 2mm in diameter to reduce the
probability of any blockages occurring in the piping, and particularly the nozzle, as this would
require the process to temporarily shut down. A relatively small amount of micro polypropylene
fibres are also present in mix design to decrease the chance of plastic shrinkage occurring after the
concrete has been printed. These fibres have also been proven to provide fresh concrete with
greater workability and pumpability including pipes and hoses of smaller dimensions.
2) Less Dense HPC Mix Design

3:2 sand-binder ratio (sand aggregate contains no particles larger in diameter than 2mm).

Binder: 70% cement, 20% fly ash and 10% silica fume.

1.2kg/m3 micro polypropylene fibres (12/0.18mm in length/diameter).

0.35 water-binder (w/b) ratio.

1% polycarboxylate-based superplasticiser and 0.3% retarder (amino-tris, citric acid and
formaldehyde).
Thorley
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MDDP – Megascale 3D Printing
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Table 2 - The Composition of the Less Dense HPC in Terms of Weight Percentage
Component
Sand
Cement CEM I 52,5
Class F Fly Ash
Silica Fume
Water
Polypropylene
Superplasticiser
Retarder
Composition (wt. %)
51.9
24.2
6.9
3.5
12.1
0.05
1.0
0.3
The mix design for the less dense HPC is made up of the same components as the denser HPC
however this mixture contains a higher w/b ratio of 0.35. The reason for this change is that this
mix needs to pumped and printed at a quicker rate therefore greater workability is required and
one way of providing this is to increase the w/b ratio. However one of the main concerns with
increasing the w/b ratio is that the setting time will inevitably increase, so to counteract this the
amount of retarder in the mix has been reduced from 0.5 to 0.3 wt. %.
3.2.3
Setting Time
It is vital for this project that two appropriate setting times are achieved and this is dependent
upon various factors including; mix design, ambient temperature, ground temperature, weather
conditions, accelerators and retarders. There are two types of setting times that are used regularly
industrially, these being the initial and final setting times. The definitions of these two setting
times are very loosely defined and there are dozens of tests available to measure each value.
Experimental methods based on penetrative resistance such as ASTM C403 (Schindler, 2004) will
be used to determine each mix designs initial set and final setting times before the mix designs are
confirmed.
There are also experimental methods available that are used to determine workability; the
slump test is commonly used to measure fresh concrete’s workability. This test involves filling a
cone-shaped metal mould with fresh concrete then removing the mould and measuring to what
extent the concrete slumps downwards. Water-cement (w/c) ratio is the main influence in the
workability of fresh concrete and in order for the fresh HPC used in this project to be pumped to
the top of the printer structure the mix design has to provide a sufficiently workable mixture. In
general practise a minimum w/c ratio of 0.4 is defined as the cut-off point at which concrete can
be pumped, however, there are admixtures that provide concrete mixtures with w/c ratios below
0.4 the workability to be pumped successfully (as discussed earlier in the Proposed Mix Designs
section).
The issue in this design project is that due to its unique nature and specific structural
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requirements very distinctive mix designs will be required and it is not possible to undergo the
necessary experimental work that is needed to determine a concrete’s initial and final setting
times. There are mathematical models available to help calculate initial and final setting times
(Schindler, 2004) however these require the use of hydration parameters that are calculated
experimentally in laboratories and in the field. These hydration parameters differ with every mix
design and as the mix designs in this project will be unlike conventional concrete mixtures it will
be necessary to compromise and use the hydration parameters of a similar mixture in the
calculations. Once the initial and final setting times have been determined, further calculations
will be needed in order to account for the presence of any accelerators or retarders present in the
fresh concrete mixture.
3.2.1
Influence of Temperature on Setting Time
Ambient temperature plays a crucial role and is one of the most significant influences in
determining initial and final setting times of a concrete mixture. High ambient temperatures are
something to be wary of as these lead to increased evaporation of water from within the concrete
mixture and therefore lower workability. Higher temperatures also increase the rate of hydration,
which reduces setting time so it is wise to perform slump tests onsite or at least in an environment
of the same temperature to ensure the mix design selected provides a workable mix of fresh
concrete with appropriate setting times.
Experimental work has been conducted in order to try and better understand the influence that
varying temperature will have on setting concrete (Wade, Nixon, Anton K. Schindler, & and
Robert W. Barnes, 2010). A total of nine different mix designs were analysed all with varying fly
ash, cement and water contents. It is important to consider that the mix designs in this
investigation are not a form of HPC and therefore have higher w/c ratios (ranging from 0.41 to
0.81). None of the mixtures contain silica fume however one of the mix designs is relatively
similar in that it contains 20% class F fly ash along with 80% cement and a w/c ratio of 0.51
meaning this mix design will be the focus of the study. In the investigation three different batches
of each mix design were prepared, each with a different temperature. There was a hot, cold and
control batch that yielded fresh concrete temperatures of approximately 40, 14 and 22°C
respectively.
The results for the mix design containing 20% class F fly ash are shown below in both table
and graph form and as expected the hot batch showed the quickest initial and final setting times,
followed by the control batch and then the cold batch.
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Group 2
Table 3 - Setting Times at Various Temperatures
Mix Type
Batch Conditions
Cement (80%) and
Class F fly ash
(20%)
Hot (40°C)
Control (22°C)
Cold (14°C)
Setting Time (hrs)
Initial
Final
4.01
4.91
6.10
7.70
7.68
9.92
Figure 2 - Effect of Temperature on Initial and Final Setting Times of the 20% Class F Fly Ash
Concrete Mix (Wade, Nixon, Anton K. Schindler, & and Robert W. Barnes, 2010).
The lines of best fit can be used to provide a rough estimate of initial and final setting times at
a particular temperature although it is important to remember the setting times will more than
likely be lesser than those displayed in this data due to differing w/c ratios as mentioned
previously. For this project in particular, printing should only be undertaken if ambient
temperature is above, and predicted to remain above freezing. In the event that temperature drops
below freezing then printing would have to be suspended or alternative methods of heating the
structure would have to be considered.
A maximum printing temperature of 35°C should also be set as operating above this
temperature would be detrimental to concrete properties. Higher temperatures lead to increased
amounts of evaporation and water loss from within the concrete and this is something that should
be particularly avoided when dealing with lower w/c ratios. One potential solution to combat
excessive water loss of this nature is to spray the surface of the setting concrete with water
throughout the setting process.
3.2.2
Initial and Final Set Calculations
The following equations are taken from an ASTM standard test method known as ‘ASTM C
403’ and gives a rough indication of the initial and final setting times that can be expected
(Schindler, 2004).
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MDDP – Megascale 3D Printing
Initial set: 𝑡 = 𝜏 ∙ (−𝑙𝑛 [
Group 2
∙
⁄
])
⁄
Final set: 𝑡 = 𝜏 ∙ (−𝑙𝑛 [
∙
⁄
])
⁄
ti = time at which initial set is reached (hours),
tf = time at which final set is reached (hours),
w/b = water-binder ratio,
τ, αu and β = hydration parameters.
As discussed previously, the hydration parameters have to be taken from literature from
experimental work that has been carried out on a similar mixture. As the mix designs used in this
process are innovative and different to conventional concrete mixtures it is impossible to find any
parameters that currently exist for HPC mix designs of this nature. Instead hydration parameters
for a concrete mixture with a w/b ratio of 0.39 where the binder contains 80% cement and 20% fly
ash will be used instead. Obviously the correct w/b ratio can be used in the calculations but the
hydration parameters will not be as accurate. It is also important to keep in mind that the
hydration parameters used in these equations were calculated based on an assumed ambient
temperature of 21.1°C. The ambient temperature will obviously vary for this particular project
depending on the site location and the time of year. The effect of temperature was discussed in
great detail previously in the report.
1) Denser HPC Mix Design
Initial set: 𝑡 = 15 5 ∙ (−𝑙𝑛 [
∙
])
Final set: 𝑡 = 15 5 ∙ (−𝑙𝑛 [
∙
])
Initial set: 𝑡 = 15 5 ∙ (−𝑙𝑛 [
∙
])
Final set: 𝑡 = 15 5 ∙ (−𝑙𝑛 [
∙
])
⁄
⁄
= 5 2 ℎ𝑟𝑠
= 6 6 ℎ𝑟𝑠
2) Less Dense HPC Mix Design
⁄
⁄
= 5 8 ℎ𝑟𝑠
= 7 5 ℎ𝑟𝑠
The setting times for the less dense mixture are greater than the denser mixture, which is to be
expected, although it may appear that both mixtures produce setting times that are longer than
expected, however this is not a major cause for concern for the following reasons:

This equation does not take into consideration the silica fume that is present in both
mix designs (10% of the binder). Silica fume is known to reduce setting times particularly when a form of superplasticiser is also included in the mix design (Rao, 2003).

If the hydration parameters had been calculated based on the correct mix designs, par13
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MDDP – Megascale 3D Printing
Group 2
ticularly the w/b ratio, then much lower setting times would be delivered.

An assumption should be made that the retarder does not alter the relevant setting
times to any great extent as this admixture merely provides enough open time for the
fresh concrete to be mixed sufficiently, pumped and printed. Once the concrete has
been printed, it is then safe to assume that it will begin setting.
To summarise, the actual setting times would have to be calculated using experimental
methods as well as the mathematical models shown above. There are a wide range of methods
available to analyse a mixtures setting time however the ASTM C403 method is most commonly
used. This test involves forcing needles into a sample of concrete to gauge the extent to which the
concrete has set in terms of penetrative resistance. A resistance of 3.4 MPa is said to represent the
initial set stage, this value was chosen as at this resistance the concrete can no longer be vibrated.
Final set is said to have been reached at a penetrative resistance of 27.6 MPa when the
compressive strength is approximately 0.6 MPa.
Once the actual setting times have been calculated using the ASTM C403 method it should be
expected that the initial and final setting times would be much shorter due to the reasons
discussed earlier. If the experimental work showed that the mix designs had to be changed in any
way then these alterations could be made and the mix design fine-tuned before the process was
underway.
3.2.3
Admixtures
Admixtures are considered to be extra components within the mix design to go along with the
cement, water and aggregate as these are essential constituents. The sole reason for the addition of
these variable components is to alter the concrete properties; admixtures are capable of altering
setting time, compressive strength, workability, buildability, pumpability, curing temperature
range and even colour.
Accelerators: As the name suggests this is a form of admixture that is used primarily to
reduce setting time, however, they do have other useful functions as well such as increased
workability and compressive strength. Some accelerators also lead to a significant increase in the
development of early compressive strength which is especially useful in this particular process as
numerous layers of concrete have to be piled on top of each other. One of the main disadvantages
to using accelerators is that they tend to lead to an increased amount of plastic shrinkage however
other admixtures such as superplasticisers can be used to counteract this effect (T.T. Le, 2011).
Retarders: Simply speaking this type of admixtures has the opposite influence of an
accelerator in that it is used to delay the setting time of a concrete mixture. The retarder achieves
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this as it is chemically designed to temporarily prevent hydration reactions occurring in the
concrete mix. Retarders are useful on projects where quick setting needs to be avoided e.g. in
countries with warmer climates where the retarder is necessary to prevent the high ambient
temperature causing concrete to set too soon. It is also useful on projects where there is a
significant delay between mixing and pouring which is the case, to some extent, on this project as
the freshly mixed concrete needs to be pumped up to the top of the structure for printing.
Superplasticisers: The inclusion of this admixture in a concrete mix design allows the use of
less water without altering the workability or pumpability of the concrete (T.T. Le, 2011). This has
obvious benefits for this 3D printing process as it allows lower w/b ratios to be used (0.26 and
0.35) which in turn will provide a reducing setting time and ensures the process is less time
consuming as printing can be done quickly.
Those are the three main groups of admixtures available for the alteration of concrete
properties. Both a retarder and a superplasticiser can be found in both mix designs for this process
in the form of a polycarboxylate-based superplasticiser and an amino-tris, citric acid and
formaldehyde retarder. However these two admixtures are only present in relatively small
quantities when compared with the two admixtures; silica fume and fly ash which represent 10
and 20% of the binder mix respectively.
Silica Fume: This fine powder is produced as waste by-product in the production of silicon
and silicon alloys and can be found in most HPC mix designs (Khan, 2011). Silica fume is mainly
silicon dioxide (SiO2) and exists mainly as pure silica in non-crystalline form; however, there are
also traces of magnesium and iron that are a part of its composition. This additive is commonly
used in HPC as it encompasses the ability to not only provide the concrete with a higher
compressive strength (above 100 MPa) but also with a reduced setting time. As previously
discussed it is difficult to determine the setting time of concrete without the use of experimental
methods but experimental data has shown that the inclusion of 30% silica fume in a binder mix
can reduce the initial set time to as low as 30 minutes (Rao, 2003).
Table 4 - Physical Properties of Silica Fume (Khan, 2011).
Physical Property
Particle size (typical)
Bulk density as-produced
Bulk density (densified)
Specific gravity
Surface area (BET)
Value
<1µm
130-430 kg/m3
480-720 kg/m3
2.22
13,000-30,000 m2/kg
The chemistry behind the silica fume is too complex to discuss in detail so put simply it is the
high surface area of the silica fume powder that causes it to be highly reactive and its presence
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increases the rate at which the hydration of C3S, C2S, C3A and C4AF (compounds found in
cement) occurs. There are plenty of other reasons why silica fume is used in concrete, e.g. high
early compressive strength, high tensile strength, increases durability, toughness and abrasion
resistance, high electrical resistivity and increased bond strength. These are all useful; however,
another advantage to using silica fume is that it reduces the concretes permeability to chloride
ions and water intrusion. This is of particular importance in this project as steel reinforcements are
being used within the walls of the structure and exposure to water and chloride ions will cause
steel to corrode (J.M.R. Dotto, 2004). Any significant amount of corrosion could have dangerous
consequences for a structure therefore the use of silica fume is justified purely from that
standpoint alone.
Research has shown that there is an overall decrease in water requirements when high
concentrations of silica fume are added to a concrete mix provided that sufficient superplasticiser
is also used (Sellevold, 1983). The addition of silica fume (>5%) without the addition of a
superplasticiser will lead to the decreased workability and greatly increases water demand. The
superplasticiser disperses the cement and silica fume particles in the mixture and reduces the
contact points between different grains which means that less water is required to gain a specific
consistency.
Fly Ash: Produced as a by-product in the combustion of pulverised coal in power generation
stations, fly ash acts as somewhat of a cement substitute and is applicable to most types of
concrete, not just HPC. The use of coal based power has boomed since the oil crisis of the 1970s
so there is no shortage of fly ash available for use in concrete mixtures, in fact fly ash features in
over 50% of ready mixed cements (Xuiping Feng, 2011).
Table 5 - Chemical composition of cement CEM I 52,5 and fly ash (T.T. Le, 2011).
SiO2
Chemical Composition (wt. %)
Cement CEM I 52,5 Fly Ash
19.24-21.5
45-51
Al2O3
4.1-4.9
27-32
Fe2O3
CaO
MgO
SO3
2.7-2.9
61.9-64.0
1.1-1.2
3.0-3.2
07-Nov
01-May
01-Apr
0.3-1.3
K 2O
0.6-0.7
01-May
Na2O
0.2
0.8-1.7
Component
TiO2
Cl
0.04/0.05
Loss of ignition 2.3-4.1
0.8-1.1
0.05-0.15
-
There are a variety of advantages to using fly ash in a concrete mix design. Firstly, similar to
silica fume, the use of fly ash reduces the permeability of the concrete to water and other
corrosive chemicals therefore the chances of the structures steel reinforcements being corroded
are greatly decreased. Provided the concrete is cured properly the presence of fly ash decreases
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the size of the pores in the concrete, this also reduces permeability and perhaps more importantly
increases the strength of the mixture. The fine particles in fly ash (and silica fume) help to reduce
bleeding and segregation in the concrete and provide fresh concrete that displays better
pumpability as well as workability which in turn permits the printing of more intricate designs.
Since fly ash improves the workability of fresh concrete it also permits the usage of a lower w/b
ratio.
3.2.4
Pumping Concrete
An automated process such as this requires a constant steady supply of fresh concrete to the
printer head. As it would be impractical to mix all the individual components of the concrete
mixture on top of the printer, it is necessary to pump the freshly mixed concrete up from ground
level. Although 3D building printing is a new and innovative process, the pumping of concrete has
been used in industry for over 80 years therefore the necessary technology already exists. This
project differentiates itself from most conventional concrete building projects in that the concrete
is placed at a much slower rate via the use of a small nozzle. This ultimately means that the pump
will be delivering much lower flow-rates (0.324 and 2.42m3/hr) than the average industrial
concrete pump.
The primary concern when pumping concrete is the mix design as this is the main factor in
determining the concrete’s workability. If the concrete is too viscous it will be difficult to pump
and there is a high risk of blockages occurring. An increased w/c ratio improves a concrete mix’s
pumpability however the addition of water also increases setting times so a superplasticiser is
used to allow for a low w/c ratio whilst maintaining pumpability.
The concrete pumps that are already in use in industry fall into one of two groups; line and
boom pumps:

Line pumps are usually mounted onto a small trailer and reinforced rubber hoses are
manually attached, which the freshly mixed concrete is pumped through. This type of
pump is used for smaller projects however there are line pumps available that are capable
of pumping up to 112m3/h.

Boom pumps are larger pumps that are mounted onto the back of a truck with a robotic
arm that is attached. The fresh concrete is pumped along this robotic arm to its desired
location. Commonly used boom pumps can pump up to 148m3/h and have a robotic arm
reach of 47 and 43 metres high and wide respectively.
Both line and boom pumps are a form of piston pump, which is a type of positive displacement
pump. The basic principle of this kind of pump is that it traps a certain amount of fluid and then
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forces that pocket of fluid into a discharge pipe. Piston pumps do however result in an intermittent
flow, which is not usually an issue in conventional construction projects; however, a constant
steady flow is required for printing concrete. In order to ensure steady flow a piece of equipment
known as a hydraulic ball valve pump is used. This equipment basically consists of two separate
piston pumps that pump concrete alternately to ensure a smooth flow to the printer head. Schwing
Inc. have developed a line pump that acts as a dual action pump and incorporates a surge chamber
where the two lines merge into one to ensure smooth flow. The surge chamber holds an excess of
concrete so that any lapse in flow-rate can be compensated for as the fresh concrete passes the
surge chamber. This pump is known as The Hydraulic Ball Valve (HBV) 160.
Piston pump
Surge chamber
Ball valve
Figure 3 - Dual Piston Pump Ball Valve and Surge Chamber Arrangement (Schwing).
In all projects that require concrete to be pumped it is common that prior to any pumping the
pipes running from the pump will be treated with a primer. This primer is mixed with water and
run through the pipes to ensure the pipe surface is slick and friction between concrete and pipe
surface is kept to a minimum. This will inevitably affect the friction factor that will be discussed
later in the report in the fluid mechanics section.
3.2.5
Concrete Mixing
High performance concrete has been successfully mixed in both transit and central mixers in
the past however HPC mixes can often be sticky and prove difficult to mix so every precaution
should be taken to ensure an efficient mixing setup is implemented. Particular care must be taken
in this process as undensified silica fume constitutes 10% of the binder used in the concrete mix
design and this is known to cause “balling” during mixing. Balling is effectively the clumping
together of solid components during mixing that leads to ineffective mixing that can be
detrimental to concrete properties after setting (Ferraris, 2001).
Whenever a unique HPC mix design is being used the mix design and the mixing procedure
itself will need to be optimised. Both transit and central mixers have been used industrially
however a transit mixer is not appropriate for this process as the build is on a relatively small
scale and there is no need to transport concrete great distances. Therefore a central mixer will be
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used in this process and the constituents of the mix design will be added gradually via an
automated process. The solid components of the mix design will be fed into the mixer using screw
feeders to control the feed-rate and a flow control valve will be used to control the flow of water
into the mixer.
Due to the relatively low w/c in HPC it is especially important that optimum mixing is
achieved. A recent study (Jiong Hu, 2005) suggested including moisture sensors in the mixer to
ensure moisture was consistent through the mixture. Monitoring moisture content would also have
the added benefit of notifying the operator if the w/c ratio within the mixture was incorrect; then
appropriate action could be taken to correct the error.
3.2.6
Mixing Arrangements
Two different mix designs are being used in this project; therefore two separate mixing
arrangements are necessary. Just over three times more slow setting (less dense) HPC is required
than the fast setting HPC so naturally the volume of each of the mixers and all the relevant storage
tanks will have to reflect this difference. However, ignoring the scale, the two mixing
arrangements will be virtually identical as the two mix designs are very similar and can therefore
be mixed in the same fashion. For each mix design, five different storage tanks will be used. Sand
aggregate, binder mix (silica fume, fly ash and cement combined), polypropylene, superplasticiser
and retarder tanks will be used to hold the individual components before printing begins. The
feed-rates of each individual component in the mix designs are shown in Appendix 3 (21.2).
The feed-rates of each individual component in the mix designs are shown in Appendix 3
(21.2).
When the process is ready to begin, the materials start being fed into each of the mixers at the
specified feed-rates and the mixers are left for an hour to allow the appropriate amount of
concrete to accumulate. In an hour 0.324m3/hr and 2.42m3/hr of fresh concrete will build up in the
fast and slow setting mixers respectively. These two values were chosen as they match the
necessary volumetric flow-rate meaning each mixer has an overall residence time of 1 hour.
Residence times in excess of 1 hour should be avoided as hydration begins once the cement mixes
with water so printing the concrete quickly will ultimately benefit its mechanical properties.
Despite the benefits of printing quickly, it is important to provide a residence time that allows for
sufficient mixing to occur. After this initial hour the printing sequence will begin with the fast and
slow setting concrete both being pumped periodically. Whenever a particular mix is not being
used i.e. no concrete is being pumped from the mixer; material will automatically stop being fed
into the mixer so the volume of concrete in the mixer remains constant. When one mix of concrete
is not being pumped a certain amount of concrete will be left in the piping however this should
not be a problem as the use of retarder provides the concrete with sufficient ‘open time’ before it
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begins to set. The controls scheme for the entire mixing system is shown in Figure 4.
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Plant Item No.
T 101 / T 201
Description
Material of Construction
Capacity [m3]
Operating Flow/Feed-rate [kg/hr]
Residence Time [s]
Operating Temp [ᵒC]
Operating Pressure [barg]
Binder mix tank
T 102 / T 202
T 103 / T 203
T 104 / T 204
Sand aggregate tank Propylene fibres tank Superplasticiser tank
Carbon steel
Carbon steel
PVC
PVC
T 105 / T 205
M 101 / M 201
Retarder tank
Continuous mixer
P 101 / P 201
Line pump
PVC
Carbon steel
Carbon steel
30.0 / 30.0
25.0 / 25.0
0.1 / 0.5
1.0 / 2.5
0.5 / 1.0
0.65 / 4.8
35.0 / 35.0 (per hr)
271.8 / 1884.0
407.4 / 2826.0
0.38 / 2.72
7.61 / 54.45
3.81 / 16.34
761.4 / 5445.0
761.4 / 5445.0
-
-
-
-
-
3600
-
≈ ambient
≈ ambient
≈ ambient
≈ ambient
≈ ambient
≈ 16°C
≈ ambient
≈0
≈0
≈0
≈0
≈0
≈0
8.8 / 11.6
Mains Water 16 oC, 2.4 barg
T 102
T 101
Legend:
LC
Level controller
FC
Flow controller
MS
Moisture sensor
PC
Pressure controller
FRC
Flow ratio controller
FCV = Flow control valve
SF = Screw feeder
BV = Ball valve
T 105
T 104
T 103
Process Notes:
SF 103
SF 102
SF 101
The same PFD and control scheme is used for
each of the two mixing/pumping
arrangements.
FC
FCV 101
FCV 103
FCV 102
M 101
The capacity and operating values are given
for both the fast and slow setting concrete
mixers in the form of FS/SS.
MS
FC
LC
FCV 104
The fast setting mixing arrangement is
known as ‘Area 100’ and the slow setting
arrangement as ‘Area 200’.
Drawn By: Sam Thorley
Date: 09/01/2013
BV 101
FRC
P 101
Process Section: Concrete mixer and
pumping arrangement (Area 100).
Rubber Pipe to
Printer Head
University of Surrey
Multi Disciplinary Design Project
BV 102
Process Flow Diagram
Project Name: 3D Building Printing
Figure 4 - Process Flow Diagram
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3.2.7
Group 2
Concrete Fluid Mechanics
It is the intention of the group to mix the concrete at ground level as this is the most practical
option however this means once it has been mixed the fresh concrete will have to be pumped up to the
printer head. Pumping concrete provides a unique scenario to most other fluids as concrete is viscous,
abrasive and begins to set if it is left stationary for too long. The following procedure (Thorpe) allows
for all the details of the concrete’s fluid mechanics to be determined. A few different calculations need
to be carried out in order to determine the fresh concrete’s velocity, Reynolds number, friction factor
and ultimately the pump demand necessary to supply the freshly mixed concrete to the printer head.
Firstly, the mean velocity of the concrete must be calculated. This is done using the volumetric flowrate that is already known and the cross-sectional area of the pipe.
Mean velocity:
𝑈 =
Once the mean velocity is known it is then used to help calculate the flow’s Reynolds number.
This is a dimensionless value that is effectively a ratio between the inertial and viscous forces in a
particular stream. Once the Reynolds number has been determined it is possible to then define
whether the flow is laminar or turbulent. It is said that when the Reynolds number is relatively low (<
2000) the flow is laminar and when it is high (> 2400) the flow is turbulent. When the Reynolds
number of a flow happens to fall between 2000 and 2400 the flow is said to be transient i.e. the flow
is varying between laminar and turbulent. More viscous fluids tend to provide a lower Reynolds
number so it is expected that the flow of concrete will be laminar.
Reynolds: 𝑅𝑒 =
The viscosities used (300 and 400Pa.s) were based on concrete mixtures that have been used in
previous experimental work (S.E. Chidiac, 2009). Particularly high viscosity values were chosen to
ensure that the concrete pumpability was not underestimated. The fasting setting mix density
(2350kg/m3) was taken from a Loughborough University study (T.T. Le, 2011). The density for the
less viscous mix was estimated to be (2250kg/m3). The Reynolds number can then be used to help
calculate the friction factor as there are two different friction factor equations; one for laminar and
one for turbulent flow.
Friction factor: 𝐶 =
(When Re < 2000)
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𝐶 = 0 079𝑅𝑒
(When Re > 2400)
One thing that is important to bear in mind when using the above Cf equations is the fact that these
relationships are based on the assumption that the pipe in question is smooth and in reality this is
rarely the case. The piping used in this case is composed of rubber which has an average inside
roughness (e) of 0.006-0.07mm (Thorpe) in order to determine whether or not the pipe is ‘fully rough’
the viscous sub-layer has to be determined using the following relationships.
Shear stress: 𝜏 = 𝐶
𝜌𝑈
and 𝜏 = −𝜇
Integration and rearrangement then allows for the viscous sub-layer (δ) to be determined.
Viscous sub-layer: 𝛿 = −𝜇
If it is determined that the pipe inside roughness is greater than the viscous sub-layer (e>δ) then
the pipe is deemed ‘fully rough, which means that Cf is independent of Re.
Then the pressure at which the concrete must be pumped at in order to reach the printer head at the
necessary flow-rate can be calculated. The pump demand is calculated using the Bernoulli equation in
a form that accounts for the change in elevation that the concrete is to undergo as well as any losses in
momentum that are caused by valves, bends in the pipe etc. The ‘x’ in the final term of the equation is
determined by how many 90° bends, valves and junctions are present in the piping and the x value is
multiplied by the pipe diameter (D) in order to try and accommodate for any losses in momentum.
For example in a pipe containing a standard 90° bend and a T-junction, x values of 35 and 75
multiples of D are used respectively.
Pump demand: ∆𝑃 = 𝜌𝑈
𝐶
+ 𝜌𝑔(𝑧
− 𝑧 ) + 𝜌𝑈
𝐶
(
)
Now that the demand has been determined the pump power can be calculated given that the pump
efficiency is known.
Pump power: 𝑃 = 𝑄∆𝑃
The equations above were applied to both concrete mixes and their appropriate pump and piping
setup and resulting values are shown below. The detailed calculations are included in Appendix 4.
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Table 7 - Resultant Values Obtained from the Fluid Mechanics Calculations in Appendix 4
System Parameters
Volumetric flow-rate (m3/hr)
Velocity (m/s)
Reynolds number
Friction factor
Shear stress (Pa)
Viscous sub-layer (mm)
Pressure drop (bar)
Pump demand (bar)
Pump power (kW)
3.2.8
Fast Setting
Concrete Mix
0.324
0.011
0.0065
2461.5
345.0
13
3.5
8.8
0.079
Slow Setting
Concrete Mix
2.420
0.038
0.043
374.3
608.1
19
4.1
11.6
0.779
Hydration Chemistry
Simply put Portland cement is a mixture of numerous different compounds that all react with
water to form new hydrated compounds and this in turn causes the gradual setting and hardening of
the concrete. In order to make an informed choice of cement mix it is important to first gain a good
understanding of the various reactions that are occurring and the differing properties of the products.
All of the compounds in Portland cement are anhydrous however the addition of water causes
these compounds to decompose. This causes the formation of supersaturated and unstable solutions
initially; however, these gradually deposit their excess solids and reach equilibrium with the hydrated
products. The nature of the hydration reactions that occur when water is mixed with cement can be
better demonstrated if we consider the example of 3CaO.SiO2, which is commonly abbreviated to as
C3S.
𝐶 𝑆 + 3𝐻 𝑂 → 3𝐶𝑎
+ 𝐻 𝑆𝑖𝑂
+ 4𝑂𝐻 (Jeffrey W. Bullard, 2010)
The hydration process is highly complex with many different reactions occurring simultaneously
particularly with the inclusion of various admixtures, however this reaction can be used to help
analyse the process of hydration. The process can be broken down into four different stages; initial
reaction, slowing of reaction, acceleration stage and deceleration phase. Although it is difficult
practically to pinpoint the exact stage of transition from one stage to another, each of the processes
can be seen clearly in the calorimetry plot shown in Figure 5.
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Figure 5 - Rate of Hydration as a Function of Time According to Isothermal
This initial reaction continues to occur even after the solution has been saturated with calcium
hydroxide [Ca(OH)2], or lime as it’s also known, and the excess is deposited in the form of calcium
hydroxide crystals. The crystals remain in contact with the saturated solution until they come into
contact with water; they then undergo hydrolysis, which liberates some more lime into the solution. A
compound known as calcium silicate hydrate, or C-S-H as it is commonly abbreviated to, is also a
product of the initial reaction and it is thought that the build-up of a thin metastable layer of C-S-H
makes it difficult for water to access the site of the reaction (Jeffrey W. Bullard, 2010). It is thought
that this thin layer reaches equilibrium with the rest of the solution at the end of the initial reaction
stage thus introducing the second stage where there is an evident slowing in the rate of reaction.
The next stage of the hydration process is known as the acceleration stage where the rate of
hydration begins to increase. The time that elapses before the concrete reaches this stage can be
altered by the addition of chemical retarders, which are present in both mix designs within this
process, however eventually every mixture will begin to see a dramatic increase in the rate of
hydration. The exact moment at which the acceleration stage begins is hard to identify exactly
however it is understood that the increased hydration is related to acceleration in the rate of
nucleation and growth of a stable form of C-S-H, which is thought to form after the metastable layer;
however, this has been doubted in the past. Some believe the stable C-S-H that forms is due to the
conversion of the metastable C-S-H layer sometime after the metastable layer has been formed. The
reason this claim has been somewhat disputed is due to the fact that in some cases stable C-S-H layers
have been known to form earlier without the existence of another hydrate layer (Lea, 1970).
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Deceleration stage of the hydration process is the longest of the four stages by some distance as
some concretes continue hydration and strength development for weeks after the maximum hydration
rate has been reached. It is generally accepted that during this stage hydration is controlled by
diffusion however there are other factors involved i.e. lack of water and reduce surface area for
reaction as all the smaller particles have been consumed leaving only larger particles.
3.2.9
Drying Shrinkage
Shrinkage is the term used to describe the loss in volume that concrete experiences during the
curing process and unless properly managed, it can lead to cracking and ultimately a loss in strength.
All concrete shrinks whilst setting, however different measures can be taken in terms of mix design
and setting conditions in order to lessen the extent of the shrinkage. The loss in volume can be
attributed to the evaporation of water from the surface of the concrete therefore it is understandable
that generally speaking the greater the water content of the concrete mixture, the greater the degree of
shrinkage (Khan, 2011). Both mix designs in this process contain a relatively small amount of water
compared with conventional concrete mix designs; however, there other measures that can be taken to
help control shrinkage.
If neglected, shrinkage could prove to be a serious problem, especially for this type of process.
This is the case because the majority of the structure is printed without formwork and is intended to
be self-supporting thus meaning there is a greater percentage of surface area that is exposed. Needless
to say, a greater amount of exposed surface area will lead to a greater degree of evaporation and water
loss from within the concrete. A measure taken to try and negate any significant shrinkage is the
addition of micro polypropylene fibres to both mixes as these are known to provide concrete with
greater cohesion.
A lot of research has been done to investigate the implications of including silica fume in a
concrete mix design in terms of drying shrinkage. Experimental work has concluded that the presence
of silica fume in setting concrete generally leads to increased amounts of shrinkage (Khan, 2011).
Numerous experiments have been conducted where concrete mixes containing varying amounts of
silica fume and different w/c ratios were tested and concrete without any silica fume whatsoever
unanimously showed the least shrinkage. The important role that w/c ratio plays in controlling
shrinkage should also not be ignored. Mixes with lower w/c ratios tend to show a greater amount of
shrinkage as most of the water present is used in one of the various hydration reactions that occur,
which causes fine capillaries to form due to the demand for more water. The surface tension within
these capillaries leads to the occurrence of autogenous shrinkage and ultimately an overall loss of
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volume. It is for this reason that lower w/c ratios are usually avoided, however in this case the project
demands concrete with a lower water content therefore other measures have to be taken to try and
control the shrinkage i.e. the micro polypropylene fibres that were mentioned previously.
3.2.10 Cement
Ferrocrete (CEM I 52,5) is a type of Portland cement that is particularly well suited to this process
due to its ability to show high early strength in a wide range of different mix designs. High early
strength is of great importance when in this process because the concrete needs to be self-supporting
(with the exception of ceilings and floors) immediately after it leaves the nozzle. Another major
advantage to using this type of cement is that it permits normal concrete production and curing in cold
ambient conditions (Lafarge, 2011). This trait allows the process to run in certain conditions that other
cements would not be able to handle however ultimately there will still be a minimum temperature
that if exceeded will mean suspending printing. The dependence of setting time and other concrete
properties on temperature has already been discussed.
3.3
Emergency Shutdown Procedure
After completing the Hazard and Operability (HAZOP) study it became apparent that some form
of equipment failure could lead to temporary shutdown of the process. A plan has to be developed to
deal with the possibility of a serious failure occurring during the printing process. Printing could be
stopped for a variety of reasons such as pump failure; pipe rupture etc. so a contingency has to be in
place that is capable of saving any work that has already been done. It would be ideal to simply stop
printing, carry out any necessary repairs and then resume printing however this is not feasible as the
concrete that has already been printed will eventually set. This is a problem as concrete needs time to
form cohesive bonds when setting, so any sort of delay between printing layers will mean the two
layers in question will not bond sufficiently and this will have a detrimental effect on the structures
mechanical properties.
A solution to the problem is to use a sprayed form of the retarder that already exists in the mix
design. By spraying the retarder evenly onto the exposed surface of the structure’s freshest layer of
concrete, the setting time will be delayed by up to 100 minutes (T.T. Le, 2011). If a longer delay is
required for more serious repairs then a more concentrated mix of retarder can be used. The aminotris, citric acid and formaldehyde retarder will be kept in a separate spray canister on-site and in the
event that the printer is shut down, site engineers in Personal Protective Equipment (PPE) clothing
will use the cherry picker on-site to cover the entire top layer of fresh concrete with sprayed retarder.
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The overall emergency procedure is as follows:
1. The concrete pumps are stopped and the printer nozzle prevents any further concrete being
placed whilst all inputs into the concrete mixers are stopped in order to ensure a constant
concrete volume in each mixer (both mixers continue to rotate in order to avoid the concrete
setting prematurely).
2. The printer head is moved away from the top of the structure in order to clear space for the
treatment of the concrete.
3. Once it has been deemed safe, two site engineers wearing PPE clothing enter the cordoned
off area around the printer with the spray canister containing the retarder.
4. The engineers enter the cherry picker platform. One engineer takes control of the cherry
picker whilst the other begins spraying the retarder onto the top of the exposed surface of the
freshest layer of printed concrete.
5. Once finished, the two engineers return the cherry picker to its original position and then
repair work can begin on the damaged part of the process as other site engineers enter the
printer area.
6. As repair work is being conducted, any concrete that remains in the rubber piping is cleared
and disposed of appropriately.
7. Once the repair work is complete, all engineers leave the site and sufficient time is allowed
to elapse until the sprayed retarder is estimated to no longer be delaying the setting of the
concrete.
8. The printer head is then returned to the position it was in when the process was halted.
9. The pumping of concrete to the printer head and addition of feed materials to the mixers then
resumes and printing continues as usual.
3.4
Internal Piping and Wiring
One of the practical disadvantages to using concrete as a primary material in construction is the
fact that it can be difficult to install the necessary piping and wiring within the walls of the structure
that are necessary for the buildings plumbing and electrical requirements. The following section
discusses the materials and practicalities involved in installing these utilities.
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3.4.1
Group 2
PVC Conduit and Piping
A Poly Vinyl Chloride (PVC) conduit provides a way in which piping and electrical wire can be
protected once installed within the structure. The main reason for using the conduit is that practically
speaking it makes it much easier to conduct repairs, for instance if some electrical wiring needed
replacing it could be pulled out through the conduit and it would save breaking through large amounts
of concrete to remove all of the wiring. In terms of piping the conduit also reduces the chance of a
pipe rupture occurring as the piping encased in the conduit has room to expand and contract, which is
particularly important in water pipes that will be dealing with a range of temperatures. If the piping
was simply surrounded by concrete there would no room for expansion and a pipe rupture would be
more likely.
There will be 4cm wide gap incorporated into the design of the walls so that the structure is
printed with sufficient space left for the piping to be put in place. However, inevitably piping will
have to run through the flooring/foundations and in this instance the conduit and piping will have to
be put in place before the floor is printed. The piping to be used will also be PVC, which has
overtaken copper as the most popular choice of piping material due to its greater longevity (copper
was known to wither and leak) and lower thermal conductivity. The thermal conductivities of PVC
and copper are 0.19 W/m/K and 389.15 W/m/K (Toolbox) respectively meaning PVC is a better
insulator and will suffer less from thermal expansion.
3.4.2
Installation
The robotic arm used on the project to help install the steel reinforcements is also used to help
install the PVC piping and conduit. The piping used has an outside diameter of 32mm and utilises
straight coupling fittings i.e. separate pipes can simply slot together to provide a water tight fit. This is
especially useful as it minimises the work the robotic arm has to do and hence decreases the chance of
it making an error. The conduit is lowered into place by the robotic arm however it does not have to
be connected in water tight fashion as the piping does, as it is only there to protect piping and wiring
(PVC Pipe - Design and Installation - Manual of Water Supply Practices, M23 (2nd Edition), 2002)
3.5
Support Materials
A major requirement of 3D printing is the need for a solution to the problem of printing an
overhang. When printing, a pre-set layer is always required beneath the subsequent layer. In the case
of features such as overhangs, this pre-set layer is not part of the building structure; therefore an
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additional support material would be required.
This support material will need to fulfil the following requirements (Kwon, 2002):






Should have a high strength to withstand the forces applied when the primary materials are
printed above. This will include the extrusion pressure.
Curing time of the support materials should be as quick as possible and, as a minimum, faster
than the primary materials so subsequent layers are not delayed.
Should be easily removable from the primary material.
Should be recyclable (beneficial from an economical and environmental approach).
Should be simple to control in order to prepare it for printing a layer above.
Should be as cheap as possible.
A variety of possible support materials are available and an analysis of a few of these possibilities
in relation to contour crafting is required. Further study and a decision will be made based on this
initial analysis.
3.5.1
Wax
The wax must be heated to above 90°C pre-print to completely liquefy it (Torresola, 1998). Once
in the correct state, the wax can be applied in the printing process and will take 20-30 minutes to
completely solidify. Using wax as a support material would give the following advantages and
disadvantages (Kwon, 2002):
Advantages:


Time to cure is fast.
Can withstand the pressures that would be applied by the primary material.
Disadvantages:








Difficult to remove from the primary material once it is no longer required.
Difficult to recycle.
Difficult to control (with regards to the application of the material).
Material requires pre-processing before printing.
Difficult to acquire large amount of material.
Expensive to buy; $1000 for 1 tonne (at the time of writing) (Wuhan Hangyu International
Import And Export Co., Ltd. , 2012)
Material requires printing.
Flat surface requires either manual preparation or an additional piece of apparatus for
preparation.
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3.5.2
Group 2
Sand
Sand would provide a simple solution to filling the room with no pre-processing of the material
required. Once a room is filled, a flat top-surface should be achieved by smoothing over. Using sand
as a support material would give the following advantages and disadvantages:
Advantages:







Easy to control (with regards to applying).
Simple to remove from the primary material.
Can be recycled.
Material requires no pre-processing before printing.
Easy to acquire a large amount of material.
Relatively cheap; £12 for 1 tonne (at the time of writing (Mone Bros, 2012) ).
Does not require printing.
Disadvantages:



Not strong enough to hold the pressure during printing, therefore indenting will occur.
Approximation of the quantity of sand required is difficult.
Flat surface requires either manual preparation or an additional piece of apparatus for
preparation.
3.5.3
Paste
Paste would require pre-processing as initially it would be in an almost plastic state. Softer paste
could be acquired by mixing with an agent such as Isopropyl alcohol (Kwon, 2002). Using paste as a
support material would give the following advantages and disadvantages:
Advantages:


Can withstand the pressures that would be applied by the primary material.
Post-curing, paste displays no surface cracks.
Disadvantages:






Slow curing time.
Difficult to control (with regards to the application of the material).
Approximation of the quantity of paste required is difficult.
Difficult to remove from the primary material once it is no longer required.
Difficult to recycle.
Material requires pre-processing before printing.
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

Group 2
Flat surface requires either manual preparation or an additional piece of apparatus for
preparation.
Difficult to acquire large amount of material.
3.5.4
Water-Soluble Material
A material such as the Poly-Vinyl Alcohol (PVA) thermoplastic could be used as it can be
completely dissolved in water. This material requires submersion in water for 24 hours for complete
dissolution, however warm water could reduce this time (Fenlon, 2012). Using a water-soluble
material as a support material would give the following advantages and disadvantages:
Advantages:





Can withstand the pressures that would be applied by the primary material.
Material requires no pre-processing before printing.
Simple to remove from the primary material on a small scale.
Easy to acquire a large quantity.
Easy to control (with regards to the application of the material).
Disadvantages:






Expensive to buy; $89.50 for 1Kg (at the time of writing (Inventables, 2012)).
Slow removal time.
Requires printing.
Cannot be recycled.
Requires correct disposal methods of the water post-dissolution.
Extrusion temperature of 180 – 200°C (MakerBot Industries, 2012).
3.5.5
Comparison of Support Materials
Prior to selecting the support material for this project, a comparison must be made between the key
characteristics of each. As mentioned previously, the support material has particular requirements that
must be fulfilled. Any material considered must fulfil all of these necessities and must be scrutinised
for use with a large-scale printer.
When considering a water-soluble material, a key feature is the removal of such material. As
previously mentioned, the typical way for performing this task is the complete submersion of the
printed object. This would be impossible for a building so an alternative would need to be found. A
potential solution to this could be through the use of a high powered water jet, however it is unclear
what effect this method would have on the time taken for complete dissolution of the material; from
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engineering judgement, it could be assumed that this would greatly increase this time. In addition, the
water jet would either need to be operated manually or an additional nozzle would be required on the
printer; these would both increase the cost of printing.
Another consideration for a water-soluble material would be the cost. As these are specialised
materials and are currently only used small-scale, the cost of filling a building would be exceptionally
high. In addition, a continuous cost would be encountered as these materials completely dissolve and
are therefore not recyclable; for every printing project this material would need to be re-purchased.
There are many similarities between paste and wax. Both are difficult, if not impossible to recycle,
both would prove challenging to remove once no longer required and both would incur a large cost to
purchase the vast quantity of material required. These negative arguments could deem these two
materials not applicable.
Wax is relatively easy to acquire in bulk, however paste with the appropriate material properties is
not so readily available. An estimation of the cost of such paste would almost certainly be greater than
wax; this is based on the cost of all the pastes that were available for purchase from bulk retailers.
These two points could render paste an unsatisfactory support material choice.
The major issue that would occur with using sand as the support material is the displacement of
the sand when printing. This would cause indenting and uneven layers and would not produce a flat
surface. A potential solution for this would be to use sand in conjunction with another material; an
assumption is that the secondary support material would provide a thin flat surface to print upon.
Despite this major issue, sand would provide complete recyclability of the support material and
ease of removal. As it can be completely re-used, no continuous cost of support material would be
incurred. In addition the initial cost is relatively low.
From initial analysis, sand has been established as the most cost effective material to be used.
Furthermore, sand is the only material considered that could be deemed completely recyclable and
would provide the simplest solution to remove once no longer required. Further analysis is essential
in order to confirm that the use of sand is viable for the application in this project. In addition, a
solution must be found to the major issue of indenting while printing which was identified previously.
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3.5.6
Group 2
Use of Sand as a Support Material
A combination of sand and wax as support materials seems to be a good starting point for printing
a building. However, despite this combination being proven to work well when used on small scale
contour crafting, this does not guarantee that it will work when scaled up to building-scale printing.
There are several other limitations of this method that were not considered but will have to be
remedied if this is to be a viable method on a large scale.
The first limitation is the fact that the tests were all conducted on a closed chamber, this meant
there was nowhere for the sand to escape to. This will pose a problem in building construction
because a closed chamber will never occur; there will always have to be gaps for doorways and
windows. These gaps must then be plugged somehow to prevent the sand from escaping. This
material must also be capable of being the support for the tops of the door and window frames for
when they are printed.
The mass and volume of the sand required may cause additional problems, both in the printing
process and the transportation of the sand. If the printer is to be printing an average sized house which
can be taken to have a floor space of 80m2 and if the average room height can be taken to be 2.35m
(Roys, 2008), this means a house will have a volume of 188m3. If sand can be taken to have a density
of 1602kg/m3 (Walker, 2011), then this means 301 Tonnes of sand is required for one house-sized
building. This mass and volume will impose many difficulties on printing.
This large amount of sand will provide great forces and pressure on the foundations, therefore the
pressure applied will need to be calculated.
With the assumption that in this situation sand would act as a fluid, the following equations can be
used:
𝑃
Equation 1
=𝑃
𝑷
Equation 2
+𝑃
= 𝝆𝒈𝒉
Where, as previously mentioned, we take the average building height (h) to be 2.35m and the
density of sand (ρSand) to be 1602kg/m3. In addition the acceleration due to gravity (g) is assumed to
be 9.81m/s2 and we take the atmospheric pressure (PAtmosphere) to be 1.01×105 Pa (Engineering
Toolbox, 2012).
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Combining Equation 1 and Equation 2, and inserting the values provided gives the total pressure
shown below:
𝑃
= (1 01 × 10 ) + (1602 × 9 81 × 2 35) = 137 𝑘𝑃𝑎
This calculated pressure was found to be too high and therefore sand is not a viable choice of
support material and a different option must be considered.
As previously mentioned, sand was superlative to the other possibilities for support materials.
Wax, paste and a water-soluble material all have a very high cost, therefore it can be concluded that
for this application of 3D printing, a non-autonomous solution will be required.
3.5.7
Conventional Methods
In some of the cases when constructing slabs, ceilings or the roof, support materials will be
needed. It would be ideal to print these directly as with the walls but temporary support is needed. A
possible option is to simply use the conventional method when dealing with construction using
concrete. This involves using formwork and falsework.

Formwork is a temporary or permanent structure used to hold in place wet poured concrete.

Falsework is a temporary structure that supports a temporary structure until it can self-support
itself.
The idea is to have formwork that can give enough strength and rigidity to hold the concrete when
poured. Formwork and falsework can be of a variety of different materials including mainly wood or
steel forms. Nowadays there are various methods of setting up these support structures relatively
quickly and easily, however they will not be discussed because they will be the same as the methods
used by conventional methods when constructing with concrete.
Formwork is the most expensive component when building concrete structures, even more than
the concrete or steel used itself. Costs for concrete formwork varies; however, an average cost of
formwork including temporary material, labour and equipment required for erecting and for removing
forms at the end comes to approximately £35/m2..This cost will increase the overall cost of the project
however it is also included in conventional methods of constructing houses and therefore will cancel
out.
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The amount of formwork that will be necessary is dependent on the loading it has to support. This
includes the magnitudes of both live and dead loads. Live loads will include labour, materials or
equipment. Dead loads include the weight of freshly poured concrete which is more than dry
concrete, steel reinforcement’s weights and the self-weight of the formwork itself. Finally to mention
impact loads need to be considered. It is not the same to lay concrete gently from a low height than
dropping it from 2 meters high. However in the case of the printer it will gently pour concrete layer
by layer.
3.5.7.1
Slabs and Ceilings
Once the first floor walls have been layered out, formwork for the slab on the first floor will be
necessary. A typical illustration can be seen below:
Figure 6 - Formwork for Slabs and Ceiling
The main parts of the illustration are:

The decking is directly where the concrete will be poured onto. It is usually made out of solid
plywood panels or alternatively you can now get sheets of plywood. Alternative steel panels
can be used which provide extra resistance to the vertical pressure of the concrete.

Joists are directly underneath the decking providing support to it. They can be in various
forms, whether metal beams or trusses or simply members of wood/lumber material. The
thickness and span of joists depends on the loading applied to the form.

Stringers lie under joists providing them support. They are of wood material and again their
specifications of thickness and depth depend on the joists.

Finally shores are the members that give support to the joists and stringers. They are either
single wood posts or steel joists. Alternatively they can be steel frames with bracings to give
extra support.
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When the formwork is being set up, the printer must not be in use anywhere near the materials,
labour or equipment being used for health and safety reasons. It can however be printing in a
restricted perimeter, for example the storage room in the garden, to optimise the overall construction
time of the house. Last but not least it is crucial to ensure that no equipment or labour are present on
the decking when concrete is being laid by the printer as it might lead to undesirable results
(Oberlender & Peurifoy, 2010).
3.5.7.2
Windows and Doors
Current conventional methods of concrete construction involve support material in the form of
panels for the walls that can leave openings in them by erecting them in a certain manner, and once
the concrete is poured and set, and the panels are removed, the openings will have been formed. In the
case of having a 3D printer these supporting form panels are not used and therefore alternative
solutions need to be considered to leave openings in the concrete walls. An opening is a gap left in the
wall so that is enclosed by concrete on all sides. In order to achieve these openings, frames or window
bucks of similar dimensions to the manufactured windows and doors can be installed during the
printing of the walls. These bucks and frames are typically made out of lumber, vinyl or metal and
can be permanently installed or removed and re-used. The bucks are required as they will support the
concrete’s pressure in the wall from above and the sides maintaining the opening. Sometimes it may
be necessary to include cross bracings too for additional support against the concrete.
There are two possible methods that may be adapted for this situation:

Method 1 - Method 1 would involve installing frames on the walls using the robotic
arm. However, if the frame is ready-made then it might be too heavy for the robotic
arm to pick up. Alternatively if the frame needs to be fixed up on the site itself then
the robotic arm has the characteristics to carry this task out. Figure 7 shows an
illustration of a typical wooden window buck.

Method 2 - Involves printing out the bottom and the sides of the wall where the
opening is to be created and placing a pre-fabricated beam above, to close up the
opening. Then once the whole house has been printed the window and doors can be
installed as normal. A figure illustrating and explaining this method can be seen in
section 4.5.1.
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Figure 7 - Typical Window Frame or Buck (ARXX ICF, 2012)
4 BUILDING STRUCTURE
4.1
Introduction
The purpose of the 3D printer is for it to print a building, either a very complex structure or a
simple one-storey house. In this case it has been selected to print a typical two-storey concrete house
with three bedrooms. The reason behind this selection is the idea of mass-production previously
suggested. These types of houses are typical in the UK as well as all around the world and therefore
once a main design is done it can be altered rapidly and the next house can be ready to print. As
expected, not every task will be possible to be carried out by the 3D printer and specific tasks such as
erecting support materials and insulation will be done using conventional methods.
Engineering drawings have been prepared for one of these typical houses including floor plans,
elevations and section drawings. They have been prepared to scale and with accuracy for the software
to be able to read it and process it into the printer adequately. The actual design of the different
members forming the house has not been done but typical section sizes have been selected for the
slabs, walls and foundations. Section 4.2 will briefly discuss how the design of these elements would
have been carried out using the design codes such as the Eurocodes. In relation to this, specifications
of reinforcements required have not been included in the engineering drawings as they would require
designing the members and working out how much reinforcement it required, however a method of
installation of reinforcement for the different sections of the house has been explained in Section 4.5.
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The area of the house occupying land is 9.45m by 9.45m. This area is acceptable as the span in
between the printer is 11m hence this leaves some space on either side between the walls of the house
and the printer’s structure. The height of the house (without roof) is approximately 5m excluding the
foundations. This again is acceptable as the nozzle of the printer can be elevated up to approximately
8 meters. Typical dimensions of existing houses have been adapted into the drawings such as floor
heights, staircases, window sizes and door sizes.
This section of the report will explain printing techniques for different members of the house,
difficulties with solutions that may arise when printing these members as well as some detailing of the
members.
4.2
Design with Codes
As mentioned in the introduction the section sizes of foundations, walls or slabs has not been
designed according to any design codes as it would become off-topic from the main purpose of the
project. This section will explain briefly the steps that would have been carried out if the concrete
members were designed according to the Eurocodes, BS-Codes and the UK National Annex.
The main structural member of the house where all the loads will be distributed to is the
foundation. Foundations can be designed following Eurocode 7 and some geotechnical knowledge. In
order to design the foundations, the first step is to obtain a ground investigation report with all the soil
parameters and conditions. There are different methods of designing the foundations however the
principal idea involves working out the bearing capacity pressures and comparing them to see if they
can withstand the loads of the structure. The codes go through designing for punching shear and
reinforcement to resist bending moments in foundations (The Concrete and Cement Centre, 2006).
Designing walls is done using the same procedure as for columns however the main difference is
that bending on walls will be on the about the weak axis and fire and reinforcement requirements are
slightly different. The section sizes for the wall can be selected via trial and error methods that
involve carrying out checks to see if the wall is structurally safe to carry the loads. Some of the steps
that need to be carried out involve working out the ultimate axial load on the wall, determination of
the effective length, slenderness checks, working out moments and using the different figures on
Eurocode 2 to work out the area of reinforcements needed. Further along, the codes define the
equations to work out the minimum and maximum reinforcement requirements and the spacing
requirements (The Concrete and Cement Centre, 2006).
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The slab thickness selected for our building design is of 200mm. This is a typical thickness that
appears in various tables in Eurocode 2. The process involved to design a concrete slab is as follows.
The first step is to determine the actions and loadings applied to the slab. Then the concrete durability
and strengths are assessed. Calculations are then carried out to work out the minimum cover for
durability, fire and bond requirements. The next important step is analysing the structure to obtain the
shear forces and moments. Finally design for flexural reinforcement is carried out and then various
checks on deflection, punching shear and spacings of reinforcement bars are done (The Concrete and
Cement Centre, 2006).
4.3
Reinforcements Methods
The structure we will be designing will mainly be of concrete. Concrete is a material that is strong
in compression but weak in tension, therefore it can be defined as a brittle material. Cracking occurs
in concrete because of three main reasons, either its maximum tension stress is reached due to
external loadings on the concrete member, or due to shrinkage or temperature changes. This suggests
concrete is not a very good material to use on its own because as soon as a crack forms it will
propagate throughout the member causing it to fail. In order to prevent this and improve concrete’s
properties, reinforcement is needed. Reinforcement is usually in the form of steel or plastic.
This section will briefly mention the different reinforcement types explaining the conventional
method of installing them and then suggest potential methods of installing it using an automated
system which will be connected to the 3D printer (Mc Graw Hill, 2012).
4.3.1
Steel Reinforcement
The most common way of reinforcing concrete is using steel. The two main types of steel
reinforcement are either steel bar known as ‘rebar’ or steel wire meshes. Rebar is used in cases where
the concrete is going to subjected to high loads such as the foundations or walls whereas steel wire
meshes are for usually slabs carrying lower loads. On construction sites rebar or steel wire is placed
in a grid pattern with specified spacings given by the structural engineer and manually tied up
together with wire. Before the concrete is poured for slabs, concrete blocks known as chairs are
placed holding the reinforcement at the desired height. Regarding the reinforcement in the walls, it is
installed similarly and before the formwork is placed in position for the concrete to be poured (BR,
2010).
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Figure 8 - Reinforcements for Slab
4.3.2
Alternatives to Steel Reinforcement (Fibre-Reinforcement Polymers)
Fibre Reinforced Polymers (FRP) are composite materials made with a polymer matrix and
reinforced with fibers such as glass, carbon or aramid. FRP can be found in many forms to be used for
concrete reinforcement, such as deformed bars, wires, sheets or tapes. FRPs differ from steel in
various ways: it is ¼ the weight of steel, it is less fire resistant and they can be affected by moisture.
FRPs are made from different materials and therefore can vary in properties making it a harder
decision to select the correct type for the purpose. FRPs have a brittle behaviour so once the ultimate
tensile strength is reached it will fail whereas steel follows the same linear stress-strain curve until
yield and then maintains the same stress to failure so has a ductile behaviour. Ideally a safety margin
needs to be left between the ultimate strength and the loads (Burgoyne, 2009).
4.3.3
Installing Reinforcement using 3D Printer
The most likely and common reinforcement type to use is steel. The problem arises on how to
install the reinforcement using the 3D printing technology. The whole idea of 3D printing is to
improve architectural designs, to reduce labour work and decrease construction timings. Rather than
using conventional methods it has been suggested to use a robotic system which will later be
explained in detail how it will carry out specific movements and tasks to complete its task. As
mentioned earlier, the reinforcement amounts and details will be provided by a structural engineer.
The diagrams below suggest a possible solution on how to install reinforcement in the walls
(Khoshnevis B. , 2010).
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Reinforcement on Walls
There are two main components to the procedure. The
first one is a steel rebar screwed into a steel connector
and the second one is a steel piece which staples into the
steel connector. The steel “staple” act as reinforcement in
the horizontal direction as well as holding the vertical
rebar in position.
The robotic arm will place the reinforcement along
the wall according to the reinforcement details and
concrete will be layered on top. Concrete layers will be
printed out in layers and similarly the reinforcement will
be installed in layers too. As can be seen in the diagram
labelled 3312, the top of the rebar in the vertical
direction can be screwed to the next component.
Eventually building up layer by layer of concrete the
reinforcement will be layered up as well all along both
directions of the walls. In order to carry out this
procedure details on the components will be necessary.
Examples of them may be observed in the appendix.
Reinforcement on slabs
When printing out the slabs, reinforcement will be
added using the same process as with the wall. The
steel rebar in form of “staples” will be connected in
all four directions forming a grid pattern according to
the detailed drawings of reinforcement provided by
the structural engineer.
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Reinforcement in slabs is usually placed at
approximately half way through its thickness. The
reinforcement will need to be added beforehand and
connected to the walls so that it is held in place and
then the concrete will be poured. This will be
explained in the Printing Difficulties Section.
The concrete is poured and reinforcement will be
still
sticking
out
in
case
another
layer
of
reinforcement is required. If it isn’t required then the
vertical rebars will not be placed.
Foundations
4.4
4.4.1
4.4.1.1
Types of Foundations
Slab Foundations
A slab foundation is simply concrete poured onto the ground directly, forming a slab. This type of
foundation is the cheapest as little labour and low levels of excavation works is usually required. The
slab is made thicker under the areas where the external walls and internal walls are going to be built
on top to carry more loads. This can act as the ground level floor at the same time. A disadvantage of
slab foundations is when accessing plumbing, drainage or heating system for maintenance as they will
be buried beneath the foundations and this may become complex and expensive (Raised Floor Living,
2012).
4.4.1.2
Crawl Space Foundation
A crawl space foundation involves footings and walls to be poured giving enough space room for
people to access the level underneath the house. In comparison to slab foundation they are deeper and
hence require more excavation. Crawl space foundations are common in areas with ground conditions
where there is heavy clay present. Another major advantage of crawl space foundations is that
installation and maintenance of plumbing, heating or cooling systems is easy and simple (Recampus,
2012).
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4.4.1.3
Group 2
Basement Foundation
Basement foundations are similar to crawl space foundations, however, they have more headroom,
so basically acts as a floor beneath ground level. It consists of having higher or taller walls connected
to the piers. These types of foundation have to be constructed in areas where the upper layer of soil is
organic material or has a low bearing capacity, and requires a lot of excavations.
Figure 9 - Types of Foundations (Basement Insulation, 2011)
4.4.2
Foundations for Printers
Underground conditions with very low bearing capacity, if the total weight of the printer cannot be
held by the ground, then relative excavations need to be made and foundations strong enough for the
printer to be held in place need to be constructed. The type of foundation necessary for a dynamic
structure such as a printer is dependent on various factors such as site conditions, its anticipated loads
including its self-weight and weight of the concrete when in operation, erection requirements which
may add load when erecting or simply operational requirements which may increase loading into the
ground. Because the whole structure of the printer will be moving along the rails in the Y directions
foundations would have to be constructed all along beneath the rails. The Figure 10 shows the
foundations that could be built. Ideally the block type foundation should be built along the y direction
with the rails sitting on the pier and directly transferring all the loads into the pier and down to
concrete footings. Constructing foundations for the printer should be done manually before
transporting the printer into the site (Golod & Lee, 2004).
Figure 10 - Foundation for Printer
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4.5
Group 2
Printing Aspects and Difficulties
4.5.1
4.5.1.1
Walls and Slabs
Printing the Building Walls
The structure of the wall will be of two different setting concrete times. The technique to be used
involves printing out the exterior walls as follows. Widths of 3cm thickness of fast setting concrete
will be printed out leaving a space of 8cm where slow setting concrete can then be simply poured in.
Figure 11 shows the typical layout of the exterior walls of the house. The sections in dark grey of
300mm are the fast setting concrete which will act as supports to the slow setting concrete that will be
poured in between them; represented by the lighter grey colour of 800mm. The section of 400mm
represented in white will be a hollow section where piping and electrical wires will be installed and
insulation in the form of foam will be sprayed in.
Figure 11 - Exterior Wall Layout
In order to carry this out, seven layers of fast setting concrete will be printed around the whole
perimeter and then slow setting concrete will be poured up to the height that the next reinforcement is
needed. The nozzle will be programmed so that an exact volume of concrete is gently poured in exact
positions to prevent overflow of concrete. After this the nozzle will go printing out layers of fast
setting concrete and of slow setting concrete. Hence the sequence will eventually be:
Print Fast Setting Concrete Layer -> Print Slow Setting Concrete Layer -> Add Reinforcement
Similarly the interior walls will be the same however they will be 8cm thick. Hence they will have
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3cm of fast setting concrete of each side and 2cm of slow setting concrete in between.
A matter of consideration however arises when two walls meet. When this occurs the walls need to
be closed down with the faster setting concrete in one direction, either horizontally or vertically, to
prevent the poured slow setting concrete running down in both vertical and horizontal directions.
Wall openings need to be considered on how they will be achieved. In section 3.5 (Support
Materials) it was suggested to print out the bottom and the sides of the opening and then placing a
beam above it to complete the opening. In order to achieve printing the sides of the wall without the
concrete spilling over a similar technique to the one described above needs to be adapted. This means
that the edges on the sides of the openings will have a faster setting concrete of 3cm thickness and
then concrete will be poured in as normal. This layout of the wall openings can be observed in Figure
12and Figure 13. Once an opening has been made the same wall printing process may be adapted.
Figure 12 - Top View of Wall Opening
Figure 13 - 3D View of Wall Opening, with and without Beam
4.5.1.2
Printing the Building Slab
Some printing difficulties may arise when printing the slab on top of the walls because of
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reinforcement coming into the way of the nozzle. Figure 14 shows a typical top view layout of the
wall to slab connections. Reinforcement in the walls as can be seen in the side view will be at the
mid-point of the wall and similarly looking at the top view the connected reinforcement from the slab
will not reach the edge of the wall. As shown in Figure 14 the distance from the reinforcements to the
walls will be a minimum of 3cm at least.
Figure 14 - Top View of Slab Reinforcement Layout
As can be seen in the nozzle design, the faster setting concrete will be printed by a 3cm nozzle.
This means that 3cm layers of concrete can be layered around the whole perimeter up to the height of
the slab. Once the fast setting concrete layers have been layered around the whole area, the larger
nozzle can be used to pour the concrete to form the slab.
Another difficulty when printing off the slab will be the reinforcement setting up. Reinforcements
from the slab will be connected with the reinforcements of the wall via the connectors half way
through the floor slab. However, the reinforcement mesh might not be kept horizontally straight at
certain areas, especially in the centre. In order to overcome this concrete chairs can be used. Concrete
chairs are simply concrete blocks that are placed below the mesh to hold it place.
4.5.1.3
Connections between Walls and Slabs
In order to connect the concrete walls and slabs there needs to be some type of connection
between them so that the slab is supported by the walls. This is obtained by connecting the
reinforcements between the slab and the wall which are tied up together. In order to carry out this
process we would first build up the height of the ground floor walls to 2.4m. These walls will have
reinforcements coming up vertically to connect to the wall of the first floor. In between the ground
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level walls and the first floor walls, the concrete floor slab will be laid. As can be seen in Figure 15
the reinforcements between the slabs are connected. This can be obtained by having a connector of 4
on the wall as shown in Figure 15 allowing the reinforcement of the slab to be easily joined up rigidly
enough with the reinforcements of the wall. Alternatively they can be tied up using conventional
methods involving using ties.
Figure 15 - Side View of Slab to Wall Connection
4.5.2
Printing the foundations
The printing techniques adopted for each of these types of foundations will be different. The most
preferable type of foundation to be built would be the slab on grade. This would require high bearing
capacity ground such as bedrock or gravel requiring no excavations to be done. The nozzle can access
up to ground level and therefore can create a perimeter of concrete wall using the faster setting
concrete up to the desired height and then concrete can be poured out the nozzle to fill up the space.
On the other hand with crawlspace or basement foundations difficulties will arise when footings and
concrete wall foundations need to be constructed below ground level. The beam where the nozzle is
attached to is restricted and cannot go below ground level because the rails they are connected to are
at ground level. To overcome this there are two possible options. Firstly conventional formwork could
be set up and if height is not too high then concrete could be poured from a height and this would stop
having to use additional labour and concrete pumps. Alternatively the printer could be set up on the
site below ground level, meaning excavating and constructing temporary foundations for the printer
beforehand. This would allow the nozzle to reach low levels of ground and therefore foundations can
be printed. The only disadvantage with this idea is that the overall height of the house may be
restricted or the printer would have to be made taller.
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4.5.2.1
Group 2
Connections with Foundations
The foundations will be connected to the exterior walls via reinforcements going all the way up.
Similarly the ground level floor slab should connect horizontal reinforcements with vertical
reinforcements coming up from the foundations. This will however depend on the types of
foundations and if they will be printed or done manually. The main difficulty will arise on how to
connect the first layer of reinforcements of the walls with the ones coming out from the foundations
as circled in Figure 16. Before the walls start to be printed the ground will be flat and appropriate
reinforcement will be sticking out from beneath it from the foundations. In order to adapt the
reinforcement installing technique suggested, it is crucial to ensure that they are vertically straight and
in the correct positions so that the robotic arm can be instructed accordingly and so the reinforcement
can be carried on built along the walls.
Figure 16 - Walls to Foundation Connection (CCANZ, 2012)
4.5.3
4.5.3.1
Roof
Printing difficulties with roof
There are two main options when deciding on the type of roof to be constructed, flat or truss roofs.
The decision will be a choice by the client; however there are limitations towards how much of the
construction of it can be done using the 3D printing technology. Naturally as we are using a concrete
printer, printing out a typical truss roof with tiles will not be possible. Therefore a typical truss roof
would have to be done manually. On the other hand there is an option of printing out a flat roof
however it would require addition labour work in addition to needing additional support materials.
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Flat roofs are made up of four main layers including a decking, vapour control layer, insulation
and a waterproofing layer. Using the 3D printing technology the decking could be printed out using
similar supporting material as for ceilings and slabs however the remaining layers would have to be
done manually (Sig Roofing, 2012).
Figure 17 - Flat Roof Layout
4.5.3.2
Connections with roof
There are various options available on the type of roof available, but generally a typical truss roof
will be constructed in the UK, rather than a flat roof. Consideration has to be taken into account on
how the roof will be connected to the ceiling and exterior walls where it will distribute loadings (dead
and live loads). Connections between a trust roof and the walls can be obtained by installing a plate
on sill gasket, which is simply a horizontal wooden or metal member that closes the wall up. This is
anchored into the concrete in the walls and therefore would have to be installed when the concrete is
still wet. This means when reaching the top of the walls some space where slow setting concrete will
be filled into must be left in order to fix this plate in between. The rafters of the roof would then be
connected to theses plates all around the walls by bolts or other appropriate connections designed by
the structural engineer.
Figure 18 - Roof Connection Details (ARXX, 2012)
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4.6
Group 2
Engineering Drawings
The engineering drawings have been done using AUTOCAD 2010 version. AUTOCAD is
recognised world-wide and used by major engineering and design companies. Its principal functions
involve 2D and 3D CAD designing, drafting, modelling and architectural drawings. For this particular
project the drawings that have been produced are basic engineering drawings of a typical house with
its dimensions and principal materials; however they can be made more complex by adding
reinforcement details, piping or electrical detailing. The accuracy and detailing is crucial in these
engineering drawings to provide exact directions and instructions to the printer as they will be
converted into STL file format; this involves cutting the drawings up into layers and instructing the
printer in what order to print things. Nowadays most design software including AUTOCAD allows
converting files into STL format.
The drawings produced are in mm units to provide a greater accuracy. Both floor plans and
elevation sections have been produced to provide detailing of heights and lengths. In addition cross
section drawings would be necessary to show some of the interior detailing of the house such as the
staircase or slab thicknesses. The scale is provided on each of the drawing sheets. The floor plans for
example are on a scale of 1:100, which means 1 unit on the drawing represents 100 units in real life.
In this scenario the units are in mm and hence 1mm on the paper represents 100mm in real life. It
should be noted when measuring printed copies the scale may slightly be affected due to margins or
borders.
The following drawings have been produced for the house design and are included in Appendix
10:
Sheet 1 – Bottom Floor Plan – Scale 1:100
Sheet 2 – Top Floor Plan – Scale 1:100
Sheet 3 – Elevations (Northern, Eastern, Western and Southern) – Scale 1:150
Sheet 4 – 3D of House
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4.6.1
Group 2
Estimation of Concrete Required
Using the engineering drawings produced the total volume of concrete required for the house
could be worked out in order to calculate costs and quantities for the concrete mixes. As two different
types of concrete were being used, with different setting speeds, the amount of each one required had
to be calculated separately as they would require to be made of different constituents and hence have
different prices. Full calculations can be observed in Appendix 3, which show exactly how the areas
and volumes of each member of the house are calculated.
During the calculations for the volumes of concrete required for the exterior walls, careful
consideration had to be made to prevent repeating areas such as corners. In addition, the openings on
the walls had to be subtracted. In order to do this the areas and heights of the window and door
openings were calculated using standard sizes used in AUTOCAD and hence that volume was
subtracted from the wall volumes. The strategy applied to work out the fast setting and slow setting
concrete separately was to work out the total volume first and then multiply it respectively with the
fraction each type occupied. Similarly, for the interior walls calculations were split by floors for
simplification.
In the same way, when estimating the volume of concrete required for the first floor slab, the area
where the slow setting concrete was going to be poured in was estimated first, and then the faster
setting concrete surrounding that was going to be layered around the whole area was estimated
second. Consideration to the staircase area was taken and was subtracted appropriately from the area
where the concrete was going to be poured. Both concrete areas were then multiplied out respectively
by the slab height (200mm).
In the case where the foundations concrete volumes were calculated, assumptions had to be made
as it is uncertain of what type of foundations will be required. For the estimation it was therefore
assumed to be a slab on grade foundation type of 400mm thickness. Similarly for the roof, it was
assumed that a flat concrete roof would be constructed of approximately 200mm thickness; this can
however not be needed if a typical v shape roof is constructed as a smaller thickness of concrete
would be required for the ceiling.
Summing up the total volumes required came out to approximately:

Slow Setting Concrete = 84.1 m3

Fast Setting Concrete = 23.7 m3
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5 PRINTER DESIGN
5.1
Nozzle Design
5.1.1
Nozzle Requirements
Due to the design of the building to be printed there must be two types of concrete. These will be
pumped using separate pumps and pipes to the nozzle array which will control which concrete is to be
printed and release the concrete through a nozzle with an appropriate diameter. To make the control
systems controlling the nozzle simpler, both of the concretes will flow out of the same adjustable
nozzle rather than two separate nozzles. This is because of two reasons, first is to save the control
system from having to deal with two different nozzle positions and the second is so that each concrete
can be printed with a different diameter if the design requires it rather than limiting each one to a
single diameter.
This means that the nozzle array must incorporate a set of valves suitable for use with concrete and
allowing only one of the concrete types to flow at a time, or neither of them. At the same time as this
valve or directly after it will be necessary to combine the two flows into a single pipe prior to
reaching the nozzle. This must be designed so that concrete will enter this section of piping in an
energy efficient manner so as to not waste energy used by the pumps.
5.1.2
Initial Design
Rather than have an adjustable nozzle like those seen in some jet planes, a simpler alternative will
be utilised. This decision has been made so as to keep the design as simple as possible while still
fulfilling the needs within the printing application. The design is somewhat based on a feature seen in
some food containers to allow different pouring options as seen in Figure 19. By having the various
nozzle options on a rotatable disc it becomes relatively simple to automate the changing of nozzle
diameter to pre-set incremental diameters.
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Figure 19 - Salt container with various dispensing options
Due to the vastly different fields for the designs, the concrete nozzle will need many additional
features in comparison to the food dispenser such as a seal of a high enough standard for the task and
to have enough strength to withstand the pressure put upon it by the concrete.
Motor/s
Valve Array
Nozzle
Figure 20 - Preliminary Design for Nozzle
Array Setup
The basic design for the nozzle as seen in Figure 20 has the entire weight of the nozzle disc being
supported by whatever motor setup is decided upon for raising and rotating the disc. This is ideal for
control of the disc, to rotate it so the correct nozzle is underneath the valve array, but this will not
provide very good support for forces that are applied near its edges such as the pressure imposed upon
it by the concrete extrusion. To prevent the problem of potential deformation of the disc and to create
a good seal between the nozzle section and the valve array, an electromagnet encircling the exit of the
nozzle array to attract the disc to it could be introduced.
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5.1.3
Group 2
Nozzle Disc Design
Figure 21 - Drawing of Nozzle
The bulk of the nozzle disc is to be constructed from aluminium due to its low density of
2700kg/m3 (Engineering Toolbox, 2012) and is possible due to the lack of load bearing features of the
disc. Since the force imposed by the extruding concrete on the nozzle is borne by the electromagnets
the disc only needs to support its own weight which is why it can have a thickness of 2mm rather than
a uniform 5cm thickness to correspond with the nozzle length. The fact that the whole disc is made up
of aluminium means that the electromagnets will have no direct affect, this is a major problem but it
is easily countered. Thin plates of steel must be attached to the aluminium disc so that they are
directly underneath the electromagnets when the nozzle is aligned with the valves, this will add
minimal weight to the nozzle but provide all necessary support.
The disc can be shown to be strong enough to support its own weight by using Equation 3 and
Equation 4. These are used to calculate the maximum stress and deflection in a circular plate with
simply supported edges and a central loading. This is not exactly the same situation as will occur on
the nozzle disc, but it is a close enough approximation as the entire weight will be supported by the
central column and the disc is reasonably symmetrical and so should deform close to equally in all
directions. This load that will be applied will be equal to the nozzle’s weight which can be
approximated as a 540mm diameter with 2mm thickness aluminium disc, two 5cm long aluminium
cylinders with outer diameter 86mm and inner diameter of 80mm, and four steel discs with diameter
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90mm and 2mm thickness. This load using a density of 2700kg/m3 for aluminium and 7850kg/m3 for
steel equates to 18.1N (from a total mass of 1.845kg). Using a Poisson’s ratio of 0.33 (Engineering
Toolbox, 2012), a Young’s modulus of 69GPa (Engineering Toolbox, 2012) and a central loading
radius of 0.5cm (half of the 1cm diameter of the supporting cylinder) the maximum stress can be
calculated to be 4.57MPa and the maximum deflection to be 1.27mm. These fall well within
acceptable parameters with 4.57MPa being considerably lower than aluminium’s yield strength of
95MPa (Engineering Toolbox, 2012).
𝜎
Equation 3 - Maximum Stress in a Flat Cir-
3(1 + 𝜐)
1
𝑎 1−𝜐𝑟
=
𝑃(
+ 𝑙𝑛 −
)
2𝜋ℎ
𝜐+1
𝑟
1+𝜐 ℎ
cular Plate with Simply Supported Edges and
Central Loading
𝑤
Equation 4 - Maximum Deflection in a Flat
3(1 − 𝜐)(3 + 𝜐)𝑃𝑎
=
4𝜋𝐸ℎ
Circular plate with Simply Supported Edges and
Central Loading (Boresi & Schmidt, 2003)
Where υ is the Poisson’s ratio, h is the plate thickness, r0 is the radius of the central loaded area, P
is the central loading, a is the plate radius, and E is the Young’s modulus.
The 3mm thickness of the nozzle can also be justified via Equation 5 which gives the hoop stress
in a cylinder. This is used because there is no simple way of evaluating the stresses in a nozzle and the
closest match is a cylinder. This equation is based upon the thin walled assumption which usually
states that the wall thickness should be less than one tenth of the cylinder radius; this is fulfilled by
the 3mm thickness against the 40mm radius. Using these dimensions and a concrete pressure of 7.3
bar a hoop stress of 9.73MPa is obtained which is well below aluminium’s yield strength. The thin
walled assumption is sometimes stated to have the thickness as less than one twentieth of the radius
which the nozzle does not conform to. This means the thick walled equation in Equation 6 must be
used with an external pressure of 0 bar (atmospheric pressure), an internal radius of 40mm, and an
outside radius of 43mm. The maximum stress will occur at the inside of the nozzle, so the radius at
which the calculation is applied is also 40mm. This gives a stress of 10.11MPa, slightly larger than
that obtained using the thin walled assumption but still well below the yield strength of aluminium.
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𝜎 =
𝜎
=
𝑝𝑖 𝑟𝑖 2 − 𝑝 𝑟
𝑟 2 − 𝑟𝑖 2
5.1.4
2
+
𝑝𝑟
𝑡
𝑟𝑖 2 𝑟 2
(𝑝 − 𝑝 )
𝑟2 (𝑟 2 − 𝑟𝑖 2 ) 𝑖
Group 2
Equation 5 - Hoop Stress in a Thin-Walled
Cylinder (Smith, 1998)
Equation 6 - Hoop Stress in a Thick-Walled
Cylinder (Boresi & Schmidt, 2003)
Connection Between the Nozzle and Valve
Concrete
Electromagnet
Valve Exit
Flow
Seal
Nozzle Disc
Figure 22 - Cross-Sectional View of Connection Between Nozzle and Valve
In order to create an effective seal between the valve and the nozzle several measures have been
taken as seen in Figure 22. The shape of the connection is designed so that the two parts will always
line up exactly; this is achieved by the protrusion around the nozzle being sloped to force the two into
the correct position when they are pushed together. It is also sloped in this manner (lower on the
inside of the nozzle and higher on the outside) so that any concrete that goes past the joint will have
to go around a 135° bend and then go against gravity to escape. In addition there are electromagnets
connected to the outside of the valve and facing downwards. These are to be turned on when the valve
and nozzle are connected to attract the steel plates on the nozzle and hold the two rigidly together.
These electromagnets will have to bear all the weight that the concrete imposes on the nozzle when it
is extruded as the thin nozzle plate is incapable or resisting the large forces that will be imposed. To
calculate what strength of electromagnet is required for this task, Equation 7 -Equation 10 must be
used to find the vertical force that the concrete imposes on the nozzle as displayed in Figure 23
.
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p 1 A1
Wconcrete
p2A2
Fz
Figure 23 - Force Diagram of Nozzle
∑𝐹
= ∆𝑚 𝑚𝑒𝑛𝑡𝑢𝑚
𝑄=𝑣 𝐴 =𝑣 𝐴
𝑝 𝐴 +𝑊
− 𝐹 − 𝑝 𝐴 = 𝑚̇(𝑣 − 𝑣 )
𝐹 =𝑝 𝐴 +𝑊
− 𝜌𝑄(𝑣 − 𝑣 )
Equation 7 - Momentum Equation of Nozzle
Equation 8 - Continuity Equation
Equation 9 - Components of Momentum Equation
Equation 10 - Rearranged Components of Momentum
Equation
(San
Jose
State
University
Engineering
Department, 2012)
Where q is the flow rate, v is the velocity, A is the cross sectional area, p is the pressure, W is the
force imposed by the weight of the concrete, 𝑚̇ is the mass flow rate, p is pressure, F is force, and ρ is
the density.
These equations are used with the concrete having a gauge pressure of 7.3bar (and therefore a p 2
of 0), a flow rate of 90cm3/s (calculated from a 3x3cm section being printed at 10cm/s), a density of
2350kg/m3 and the force due to the weight of concrete to be 16N (assuming the weight to be
approximated as that of a 14cm long cylinder with an 8cm diameter). This all results in a vertical
force of 3672N which can then be countered by two electromagnets, each of 9cm diameter and 4cm
thickness and between them capable of holding 5770N (Solentec Ltd., 2005). Other options could
have been chosen but these magnets provided the best fit with the already designed disc.
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5.1.5
Group 2
Connection Between the Nozzle and Carriage
The nozzle disc will need to be supported from above as the disc itself is below the carriage. This
means a mechanism which will support the vertical load of the hanging nozzle whilst allowing for its
rotation, as shown in Figure 24, is needed.
Rotational
Movement
Vertical
Gear
Bearing
Shaft
Nozzle
Figure 24 - Forces Acting on Bearing
This can be achieved by a thrust bearing which are bearings designed to be capable of
withstanding axial loads, though they are in turn weak against radial loading. A bearing that fits all the
requirements for this bearing is the NSK Single-Direction Thrust Ball Bearing 51200 (NSK, 2012).
This has an inner diameter of 10mm, an outer diameter of 26mm, a thickness of 11mm and a weight
of 0.028kg to 0.0036 depending on the seating of the bearing. It can also withstand loads in excess of
12,000N and speeds of up to 630 or 940rads-1 depending on lubrication, both of which are well in
excess of the loads and speeds it will experience in this application.
In order to provide the rotational movement of the disc a gear must be mounted above the bearing
which will then connect to a motor. This gearing could either be a spur or a bevel gear depending on
the orientation of the motor which is in turn be decided by the location of other components on the
carriage. Both have a high efficiency (MEADinfo, 2012) and are commonly available in a variety of
sizes (HPC Gears, 2012) so there is no obvious merit to having one over the other. Due to the bearing
and motor being mounted on a square carriage, it makes most sense to vertically orientate the motor
and use spur gears. The gears to be used will have an outer diameter 30mm and an inner diameter of
10mm to coincide with the sizes of the bearing and the shaft from the nozzle disc.
There are two means of separating the nozzle from the valves in order for the nozzle-in-use to be
changed; first of which is moving the valve upwards away from the vertically fixed nozzle disc, and
second is to have a fixed valve and move the nozzle disc downwards in order to allow for its rotation.
Either is feasible and each has its detrimental factors: a movable nozzle is difficult because there are
several moving components, all of which would have to be moved together, and a movable valve will
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be a much greater weight and so require a stronger means of movement. Due to the much larger
forces involved in moving the valve it would be easier to have the nozzle and associated parts moving
vertically.
To produce this vertical motion a system similar to that used in the overall printer structure should
be used, but since the size of the necessary movement is so small there are few systems that would
not have a far greater range of motion than necessary. The simplest and easiest design for use in this
small-scale application is that of a rail-mounted, screw-driven carriage system as illustrated in Figure
25:
Motor
Screw
Carriage
Rails
Figure 25 - Layout of Screw-Driven Linear System
With this design it is possible to have the rails and screw only a few centimetres longer than the
carriage to minimise excess materials and therefore weight. The bearing and motor to provide the
disc’s motion are fixed rigidly to the carriage which would reside at its highest point during printing
and would lower several centimetres to its lowest position when the nozzle is being changed.
This kind of system could be purchased from Rexroth (Rexroth Linear Motion Slides, 2012). From
here various carriage sizes can be chosen, and one a few centimetres longer than the motor would be
the optimum to accommodate the bearing, it’s mounting, and the gears. The carriage has a length of
85mm and the rail length is calculated by adding the desired movement plus 3mm to the carriage
length giving a rail length of 155mm if 67mm of movement is needed. This amount of movement is
due to the minimum travel distance required by the system to ensure even distribution of lubrication.
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This linear motion slide is capable of withstanding a moment of 62Nm which is easily enough to
support the nozzle array. The total mass of the nozzle array is 3.407kg, this is positioned on average at
roughly a 1cm perpendicular distance which means the moment it causes is 0.33Nm, well within the
slides specifications.
145.5mm
Motors
24mm
7mm
40mm
155mm
12mm
85mm
Bearing
Spur Gears
14mm
Shaft Connected to
85mm
Nozzle Disc
Figure 26 - Drawing of Nozzle Movement Mechanism
5.1.6
Nozzle Motors
Appropriate motors must be chosen in order to rotate and lower the nozzle. The requirements are
not large and so small dc motors will be capable of meeting the specifications. Since precise
movement is required so that the nozzle and valve exit line up exactly, a stepper motor would be
ideal. A stepper motor that fits the requirements for this application is the SY28STH45-0674A high
torque hybrid stepper motor by Nanotec (nanotec, 2013). It is 44.5mm long with a 20mm long shaft
with a diameter of 5mm, it also has cross sectional dimensions of 28.2x28.2mm.
The total mass to be lifted as part of the linear motion system is 3.802kg which is 37.3N. The
motor that Rexroth pairs with this linear motion system is an IndraDyn S Servo Motor MSM 031B0300 capable of providing a stall torque of 0.64Nm (Rexroth, 2012). It also has a brake built in to the
motor which is capable of providing a 1.27Nm braking torque which will be useful for keeping the
nozzle in place vertically. This must be capable of competing against a frictional torque of 0.06Nm
that is inherent in the system in addition to lifting the 37.3N so it has an effective torque of 0.58Nm.
Using Equation 11 it can be found that the required torque is 0.0165N when using a lead of 0.0025m
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and an efficiency of 90% so this motor is easily capable of lifting this load.
𝑇=
𝐹 × 𝑙
2 × 𝜋 × 𝜂
Equation 11 – Torque of a Preloaded Ball
Screw (NSK, 2013)
Where T is the applied torque, F is the axial force, l is the screw lead, and η is the efficiency.
5.1.7
Valves
The valve is required to combine two pipe flows into a single exit pipe with a choice of which if
either is allowed through. The best way of achieving this is with an L-shaped three-way ball valve (as
shown in Figure 27) as it can allow any of the three desired states of flow with no possibility of both
concrete flows being allowed to combine as a T-shaped one would allow. An automated valve that can
fulfil this need with an appropriate valve inlet and exit sizing is the 3-way flanged ball valve with
NEMA K4 weatherproof actuator by Assured Automation (Assured Automation, 2013). This is
capable of working with a 10.4bar pressure differential which exceeds the pressure that the concrete
will be pumped. The valve then connects to the nozzle disc via an aluminium tube shaped as in Figure
22 and with the electromagnets attached; this protrudes 5cm below the main carriage to allow space
for the electromagnets. The overall positioning of the valve and other components of the nozzle
system is shown in Figure 28.
Figure 27 - Positions of a Three-Way Ball Valve (Wikipedia, 2010)
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Main Carriage
Linear
Motion
System
Valve
Figure 28 - Layout of Components on Main Carriage
Use of Robotics in the 3D Printer
5.2
5.2.1
Basic Requirements
The task of the robotic arm is primarily to install the rebar within the walls (and potentially
foundations) of the building. This requires two main actions; placing the rebar components at the
correct location in the concrete, and also screwing the vertical sections of the rebar together. These
actions are not particularly complicated and so specialised robotic arms will not be necessary and
existing technology can be used.
There are several restrictions in place that will dictate which robotic arm would need to be used:

First is the capability to lift and work with the weight of objects required in the building’s
construction. Any arm will have a dictated maximum handling capacity which must exceed
the expected weight for the rebar and any other components that it may be required to place.

Second is the need to have as light a robotic arm as possible. The arm will need to be moved
back and forth from the edge of the building (where the rebar will be) to the wall where the
rebar is being placed a great number of times. The heavier the arm, the more power will be
required for this task. The motor will also need to be supported by the crossbar/gantry of the
printer and by the supporting side arms – the heavier the arm is the stronger (and heavier)
these components will need to be, and the more power will be required to move the printer as
a whole.

Third is the minimum speed the arm will have to be capable of working at. Due to the nature
of concrete it becomes much weaker if previous layers are allowed to set before subsequent
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layers are put down. This means the placement of all rebar must be done within a certain time
to allow the printer to continue the printing of the concrete before the previous concrete sets.
5.2.2
Robotic Arm Selection
Figure 29 Axis of movement of typical robotic arm (Global Robots Ltd, 2011)
Units in mm
Figure 30 - Working Range of ABB IRB 140 (ABB, 2012)
After researching possible robotic arms which fit within the specifications previously mentioned,
one that seems to fit is the ABB IRB 140 (ABB, 2012). This robot is lightweight, weighing in at 98kg
and is capable of working with payloads up to 6kg. This should easily be capable of handling rebar, as
a common rebar size of a 20mm diameter, a 20cm length and a density of 7850kg/m3 weighs in at
roughly 0.5kg using Equation 12. This means that rebar of length up to 2.4m could potentially be
handled by the robotic arm, though using slightly smaller lengths would be more practical so as to not
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accidently exceed the arm’s limits. Other part placement that the arm would be useful for would be
the placement of lintels to the specified thickness. If the specified thickness for the lintel exceeds the
arm’s weight limit then it can be split in to multiple parts which can be placed next to each other or on
top of each other. The material could also be altered between wood, aluminium, titanium or steel, with
densities of 750 (Engineering Toolbox, 2012), 2700, 4500, 7850kg/m3 (Engineering Toolbox, 2012)
respectively, depending on what will suit the purpose. A typical exterior solid wall lintel made of
stainless steel and with a breadth of 20cm weighs in at 9.3kg/m (Catnic, 2012) so with the use of less
dense materials a lintel for a standard exterior doorway should be feasible.
𝑀𝑎𝑠𝑠 = 𝜋 × 𝑟𝑎𝑑𝑖𝑢𝑠 × 𝑙𝑒𝑛𝑔𝑡ℎ × 𝑑𝑒𝑛𝑠𝑖𝑡𝑦
Equation 12 - Mass of a
Cylinder
𝑀𝑎𝑠𝑠 = 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 × 𝑏𝑟𝑒𝑎𝑑𝑡ℎ × 𝑙𝑒𝑛𝑔𝑡ℎ × 𝑑𝑒𝑛𝑠𝑖𝑡𝑦
Equation 13 - Mass of a Beam
As with virtually all industrial robots it has 6 axis of movement so will be capable of any
movement required of it. The maximum reach is 0.81m which should be sufficient for any tasks that it
will be performing – any further reach would be achieved by movement of the printer. It can work at
high speeds and great precision with maximum velocities and accelerations of 2.5 ms-1 and 20ms-2
respectively, and a position repeatability of ±0.03mm. These are speeds which are easily fast enough
and precise enough to stay within time constraints and to place all parts within a tolerable distance of
their desired position. The robot has a typical power consumption of 0.4kW and can run off mains
voltages which means it will be very easy and cheap to run.
In order to secure the rebar together it is necessary to either weld it together or screw it in,
depending on the rebar required for a building. So in addition to being capable of gripping the rebar,
the robotic arm must have welding facilities and an unlimited working range in that axis. The IRB
140 is capable of this unlimited working range and works at a rotational speed of 450°/s so installing
the rebar should only take a few seconds depending on the thread length. There are several welding
methods which could potentially be employed by the robotic arm. The most common type used in
robotic welding is Gas Metal Arc Welding (GMAW) often known as Metal Inert Gas (MIG) welding
(Robot Welding, 2001). Spot welding is an alternative but this is primarily used for welding plates
together as it works through very high pressures and current which requires a welding gun of
considerable size with a small gun weighing 50kg – well in excess of the IRB 140s maximum
capabilities (Yaskawa America Inc., 2013).
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Figure 31 - MIG Welding Layout (Weldguru, 2013)
MIG welding uses an extruded consumable wire electrode which when placed between metals
forms an arc which in turn heats up and melts the pieces together. This is all done in the presence of
inert (such as helium) or semi-inert gases (such as carbon dioxide) to shield the weld from the
atmosphere and prevent contaminants from entering the weld and weakening it (Weldguru, 2013).
This method requires that a constant feed of wire electrode and gas be fed to the robotic arm in order
to be able to weld. This is easily achieved by a wire feeder often capable of feeding 20-30kg of wire,
or about 810-1215m of 2mm diameter steel wire (the wire is not pure steel but is a very high
percentage of standard MIG welding wire (Unibraze, 2013).
The weight of the welder will retract from the amount of rebar that the robotic arm can carry as the
robot must support it. The arm itself will only have to support roughly 2kg of the MIG welder’s
weight meaning a 1/3 reduction in carrying capacity. This is a slight detriment to the arm’s
capabilities but the increased speed of part securing with welding means that the printing process time
will be reduced.
5.2.3
Part Selection
The use of this robotic arm will present some issues which revolve around problems with the arm
grabbing the correct part for placement. This falls into two main categories: first making sure the
correct part is selected, and secondly getting the part to the arm on the gantry.
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Selecting the correct part can be done in a variety of ways, but with three main techniques, all with
their pros and cons. Having the parts placed manually in pre-assigned positions is the simplest way of
achieving this task but it has many faults. Without technology on the robotic arm itself to identify
each part, any part that has been placed in the wrong position will lead to incorrect placement of rebar
and potentially cause complete failure in the construction of the building. The arm will also not be
able to detect the orientation and positioning of the parts and so may fail to grab the part at all or
place it on the building incorrectly which could lead to similar failures as described previously.
Barcodes on all of the components will allow for quick and easy identification of parts so that the
wrong part will never be used in the building but all the other problems that the manual method
suffered from will carry over to this method also.
Machine vision which can identify shapes, sizes and orientation would likely solve all the
problems previously mentioned as the arm will be able to detect the part, check its position and
orientation so it can be picked up correctly, and also compare the positions of the building and parts
so that they are placed correctly. This method is not a complete solution, however, first is the
drastically increased price of implementing this system in comparison with the other methods, and
also the issues corresponding with getting the components to the arm in the first place still need a
solution.
The simplest solution to get the parts to the robotic arm is to move the gantry outside the printing
area and lower it to ground level for the arm to identify and grab the parts. This requires no extra
design beyond that which has already been done but is far from an ideal solution. The time taken to
do this for every part will be excessive and the power requirements will be huge in comparison to
normal usage as the entire printer structure will need to be constantly moved back and forth. Based on
printer speeds of 1ms-1 in all directions it will take 30 seconds on average (based on an average of 5m
movement in each axis) to move one piece of rebar. This doesn’t include actually fixing the rebar in
place or having to accelerate and decelerate to its peak velocity. This means it takes considerably
longer than desired to place the rebar if printing is to be considered a fast construction method for
mass production.
A solution to this could be a conveyer belt or a similar device running along the length of the rails
that the printer operates on. If parts that are needed for construction are to be placed on this conveyer
belt then it removes the need for the entire printer to be moved back and forth continually. There are
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three main issues to overcome with this method: the gantry cannot lower to the level of the conveyer
belt due to the printed building obstructing the way, the parts will need to be placed on the conveyer
belt in the right order, and an appropriate control system will be needed to make sure the conveyer
belt moves the parts so that they are under the gantry at the correct time. If this conveyer belt
mechanism is adopted then two of the three issues are relatively easy to overcome. Placing the parts
in the right order and controlling the conveyer belt should be a simple application of additional
control systems. The parts could be listed in the correct order by software at the same time as the path
of the printer being calculated. Positioning parts at the correct location using the conveyer belt could
be done simply by knowing when the part was put on the belt and by knowing the speed of its
movement.
An alternative to using a conveyer belt would be to use a scissor lift or cherry picker crane. These
are both established for lifting significant weights up to large heights (easily in excess of the 8m
required for this application). These could be mounted on rails parallel to the printer rails for the
printer arm to reach out of the printing area and grab, or they could be fixed at one end of the printing
area for the printer to move to. The scissor lift will be a poor choice for mounting on a rail as the
robotic arm will not be able to reach far beyond the printer structure. Methods could be used to limit
the problems with this lack of reach such as a special spring powered container that will mean all
parts will be pushed to the edge closest to the printing area. Rails would be an ideal choice for use
with the cherry picker as it could reach in to the printing area when it is needed, eliminating the
problem of the robotic arm only having an 81cm reach (which will not extend much beyond the
printing area).
Having the scissor lift fixed at one end of the printing area will eliminate the problem that a railmounted solution had in terms of arm reach but instead means that more printer movement is
required. Moving the printer up and down vertically (potentially the most energy-dense and timeconsuming activity) would be eliminated meaning faster printing and lower energy costs, but moving
the whole printer structure would be required which isn’t a desirable method, but may be necessary.
Placing the cherry picker at the end of the printing area would have a similar effect to placing the
scissor lift there except that it will most likely mean a lot of the cranes movement functionality would
become redundant. Rather than using all of its degrees of movement it would primarily just move up
and down and maybe occasionally venture into the printing area to slightly reduce the amount of
printer structure movement which is a waste of the additional movement that it is capable of.
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Which of these two options would be chosen, if any, depends on the speed requirements of the
placement of rebar and other parts so that they coincide with concrete setting times. The benefits of
implementing each of the two in comparison to their energy consumption and capital costs will also
need to be considered. A scissor lift with a range of motion that would be desirable for this printing
application would be one such as the Skyjack SJIII 3220 DC Electric Scissor Lift (SkyJack, 2010)
and a suitable cherry picker may be the Hinowa Gold Lift 14.70 Tracked Aerial Platform (Hinowa,
2012). The cherry picker costs more than the scissor lift but not so excessively that the cost outweighs
its benefits (MachineryZone, 2013).
This crane will have applications other than in assisting with part selection, it can help fulfil their
original role and be used as an aerial work platform. When any manual work needs to be done on the
building such as construction of ceilings it can be used to assist. Additionally, if any onsite
maintenance of the printer or protective canopy is required, then it may allow the maintenance to take
place without the printer or canopy having to be deconstructed in their entirety first.
5.3
Printer Structure
The design of the printer changed considerably throughout the lifetime of the project. This was
also one of the most challenging aspects in terms of engineering solutions to difficult problems due to
the physical size of the machine. To select dimensions for the machine, the group first needed to
decide the maximum sized building that the printer should be able to print. The idea to target the mass
production market meant that the average house size for new build houses in the UK was chosen as
the maximum build size. A rough estimate for the average house size for the UK is shown below in
Figure 32:
7m
9.5m
9.5m
Figure 32 - Average Sized UK House Dimensions
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The print area of the printer therefore must be able to print an average house with the dimensions:
9.5m X 9.5 m X 7 m. The decision was made to make the printer 11m X 11m X 8m in size in order to
have a suitable print area size.
After the dimensions were chosen a basic outline of how the printer should look was chosen and
then the relevant axes (X, Y, Z) were separated in order to efficiently design the printer. The rest of
this section will contain the steps taken in order to get to an overall design of the printer. The design
of each axis will then follow.
An idea of the overall printer structure needed to be decided before proceeding to design each
separate part of the printer. The design needed to be suitable for mass producing houses and therefore
the time to build a structure as well as the cost are the most important factors to consider when
designing the printer.
The decision was made to be able to create whole structures as opposed to building the structure in
parts and assembling it on site. This was due to not only wanting to be incredibly efficient in terms of
time to build, but also in order to design a completely new machine. There are many building
companies that pre manufacture parts before building the structure, which means that the time to
build itself is very fast; a house can be mostly built in one day in some cases. Our design however,
will not need the lengthy amount of time needed to pre manufacture the parts, it will be able to print
the building as soon as it is on site and constructed.
Contained within the inception report were two ideas for the design of the printer which are shown
below in Figure 33:
Figure 33 - Comparison of Initial Printer Design Concepts
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The image on the left shows a printer which can move along rails on the floor, with the nozzle
moving within a goal post shaped structure. The image on the right shows a fixed structure for all
axis, in which a cage like structure is built to house the nozzle and there is no freedom in any axis as
they are all fixed.
The decision was made to proceed with the goal post idea (left image). This is because the
structure can have any size of rails in order to move on. It will almost certainly add to the power
requirements as a very large structure is being moved however it was decided that the ability to print a
row of houses outweighs this. An illustration of how the printer can mass produce rows of houses is
shown below in Figure 34:
Figure 34 - Illustration of the Mass Producing Capabilities of the Printer.
For the purposes of this structure the direction of each axis is shown in Figure 35:
z
y
x
Figure 35 - Axes of Printer
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This meant that a basic idea was known about the parts to each axis on the structure which were:



X Axis – Needs to be able to move the weight of the nozzle and robotic arm left and right.
Y Axis – A rail like system in which the whole structure of the printer can move.
Z Axis – Needs to move the weight of the nozzle, robotic arm and the support beam up and
down.
This design moves in the Y direction on rails as discussed previously. An attempt to try and save
on power requirements brought about the idea to have telescopic arms for the print head and robotic
arm. This meant that the whole beam whould not need to be moved, when just using the print head or
vice versa with just the robotic arm. It was then decided that having a 8m long telescopic arm would
be unstable and could present many problems when printing. The decision was therefore made to
have the whole beam move in the Z direction and the ”goalpost” design below in Figure 36 was then
designed:
Figure 36 - Initial Concept Design of Proposed Solution
Once this design had been decided on, the separate axes could be worked on and are all described
in detail including the selected parts, in the next section of this report.
While researching for suitable linear guidance systems, a company named HepcoMotion was found
who supply complete linear motion systems for three axes of motion, which are predominately used
in factories for controlling robotic arms. It was decided that further research into their products was
required as these systems seemed ideal for this application. The parts for the majority of the printer
therefore were selected from the HepcoMotion catalogue with the full parts list of the printer structure
contained in Appendix 7.
HepcoMotion also supply motors for their systems in addition to the mechanical parts that have been
selected. The motors however, are not suitable for this application as a large power is required to
move such large masses and so they have been sourced from another supplier. The motors selected for
each axis will be discussed in detail in the electronics section of this report.
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5.3.1
Group 2
X Axis
The X axis consists of the movement of the Nozzle and Robot arm. The parts list for this axis can
be seen in Table 6 below, taken from the full parts list contained in Appendix 7
Table 6 - X-Axis Parts List.
Part
Number
Part Name
X001
X Axis Beam
X002
V Slide with Gearing Teeth
X003
V Slide without Gearing Teeth
X004
Carriage Plate
X005
Gears and Motor
X006
Drive Flange with Pinion
X007
Buffer
X008
Bearings
The first part of the axis is the main beam (X001) across the top of the structure that will hold both
the robotic arm and the print head. The robotic arm and print head are mounted onto carriage plates
(X004) via bolting. This carriage plate has the ability to move in the X-axis along the beam, via a rack
and pinion system. The pinion is attached to the motor (X005) through a hole in the carriage which
forms the rack and pinion system along with the V-Slide with gearing teeth (X002). The linear
guidance is provided by bearings (X008) which move along V-Slides (X002 & X003). There is also a
buffer (X007) included at each end of the axis in order to protect the carriages. This can be seen
below in Figure 37:
Bearings
Robotic
Arm
V-Slide with Teeth
Motor for Carriage.
V-Slide without Teeth
Nozzle
Figure 37 - X-Axis System
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When deciding on dimensions for specific parts of this axis, the first consideration taken into
account was the length of the beam. As previously mentioned, the print space required for this axis
was 11m in order to allow the printer to print an average sized UK house. The beam with the largest
cross sectional area supplied by the manufacturer was therefore chosen. It was initially anticipated
that the total mass (due to nozzle, robotic arm, concrete, etc.) that the beam would have to support
was very large, therefore this decision was made in order to reduce beam deformation and deflection.
Each carriage plate was required to have a motor in addition to either the robotic arm or nozzle
mounted to it. This meant a carriage of suitable dimensions had to be selected as it was anticipated
that the mounting face for the nozzle and robotic arm would be large.
A decision had to be made in regards to the type of bearing selected as there were two types
supplied by the manufacturer. The first was a flat bearing and the second v-shaped. An example of
both can be seen in Figure 38 below:
Figure 38- Comparison Between Flat and V-Shaped Bearings
The decision was made to use the v-shaped bearing as the robotic arm and nozzle would extrude
from the carriage creating a large moment acting about the centre of the bearings. This moment
appears as a horizontal force and therefore the v-shape will support this force more effectively than
the flat bearing, as it is held onto the v-slide.
Due to the anticipation of the mass of the nozzle and robotic arm being large, the pinion was
selected with a large number of teeth. The force applied to individual teeth due to this large mass
would be reduced in comparison to that of a pinion with a fewer number of teeth.
The specifications for each part used for this axis can be seen in Appendix 7.
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5.3.2
Group 2
Y Axis
The y-axis consists of moving the whole structure, therefore creating a difficult engineering
problem due to the accuracy required. The parts list for this axis can be seen in Table 7 below, taken
from the full parts list contained in Appendix 7:
Table 7 - Y-Axis Parts List
Part
Number
Part Name
Y001
Flat Track with Teeth
Y002
Flat track without Teeth
Y003
Carriage Plate
Y004
Gears and Motor
Y005
Bearing Block
Y006
Bearing Block
Y007
Drive Flange with Pinion
Y008
Mounting Plate
The whole structure is mounted to two carriage plates (Y003) via bolting. These carriage plates are
then able to run along the flat tracks (Y001 and Y002) which are mounted to a plate (Y008). The rack
and pinion system is comprised of the flat track with teeth (Y001) and the pinion; this pinion is fixed
to the drive flange (Y007) and is controlled by the motor (Y004). The linear guidance is provided by
the bearing blocks (Y005 & Y006) which surround the flat tracks. The bearing blocks are also bolted
to the carriage along with the motor.
Figure 39 below illustrates this design:
Mounting Plate
Gears and Motor
Carriage Plate
Bearing Block
Flat Track without Teeth
Flat Track with Teeth
Figure 39 - Y-Axis System.
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The only consideration needed for the mounting plate was the dimensions, ensuring enough length
was given for the specified print area and the width was large enough to mount the carriage to.
Similarly to the carriage used in the X-axis, the carriage used in this axis required dimensions that
allow the mounting of a suitable motor and the Z-axis beam.
For this system, a different linear guidance was chosen from the manufacturer in order to support
the mass of the whole structure. This system uses bearing blocks in comparison to the more
conventional bearings used in the other axes. These bearing blocks, designed by the manufacturer in
conjunction with the flat tracks, can withstand much greater forces than typical bearings.
5.3.3
Z Axis
The Z axis consists of the two side beams of the printer structure that support the X-axis and allow
it to move up and down. The parts list for this axis can be seen in Table 8 below:
Table 8- Z-Axis Parts List
Part
Number
Part Name
Z001
Z Axis Beam
Z002
V Slide with Gearing Teeth
Z003
V Slide without Gearing Teeth
Z004
Carriage Plate
Z005
Gears and Motor
Z006
Drive Flange with Pinion
Z007
Buffer
Z008
Bearings
The Z-axis is identical to the X-axis in structural design, however the orientation is different and
the load is now being lifted vertically. Due to the increased mass being lifted, a larger power motor
will be needed in comparison to the X-axis. The X-axis beam (X001) is bolted to the two parallel
carriage plates (Z004) which are then mounted either side to the two Z-axis beams (Z001) in order to
create the goal post structure previously mentioned. The v-slides (Z002 and Z003) and bearings
(Z008) used are the same as the X-axis as is the drive flange and pinion (Z006) used in order to create
the rack and pinion system. A buffer (Z007) has also been included to cushion the carriage once
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again.
Figure 40 below shows the design:
V-Slide with Teeth
Gears and Motor
Carriage Plate
V-Slide without Teeth
Bearings
Figure 40 - Z-Axis System.
The carriage plates for this axis were chosen based on the fact that they had to be large enough in
order for a suitable motor and beam to be mounted on to them. It was found that the carriages would
be a suitable size for all axes and therefore the same carriage has been selected for each.
The same considerations were taken into account for this axis in relation to the X-axis in regards to
the majority of the part selection as apart from the motor they are identical designs. This includes the
decisions behind the bearing, v-slide and pinion selection.
5.3.4
Cable and Piping Management
The cables and piping for the concrete cannot be left to hang freely during printing as they may get
caught on something causing them to rupture or snap. This is a scenario which will need considerable
repair work and potentially ruin the building that is being printed if it is the concrete tubing that
ruptures. To prevent this occurrence, flexible cable trays such as the Gleason Reel Powertrak
(Gleason Reel, 2013) should be used. These keep the cables contained within them, and allow motion
in only one axis so that they can follow the motion of one axis of the printer while not swaying to the
side.
5.3.5
Printer Structure Discussion
The parts that have been selected for the structure of the printer were thoroughly checked with one
another to ensure compatibility. Basic dimensions were known prior to selection enabling assisting
with this decision.
Structure analysis was then performed in order to verify the choices behind the printer structure.
A full diagram can be seen below in Figure 41.
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Figure 41 - Complete Printer Structure Drawing
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6 PRINTER STRUCTURE ANALYSIS
In order to verify the printer design, it is necessary to analyse the structure. This will include
analysis of stress, vibration, beam deflection, fatigue and part life analysis and will be carried out
using hand calculations, part specifications and the computational program ANSYS. Each individual
part of the printer will need to be accurately assessed to prove that they are structurally sound and will
not experience any failure during operation.
6.1
Stress Analysis
It is essential that the printer can withstand all internal and external forces that may be applied
during operation. Much of this analysis can be performed simply by comparing forces with those
given in manufacturer specifications, however ANSYS may be required for certain parts.
In addition, the values for any calculations involving the selected motors can be found in
Section 8.1 of this report.
6.1.1
Carriages
All six carriages require analysis and this will be performed by comparing forces and moments
applied during operation with the maximum values specified by the manufacturer. In addition, the
same product has been selected for each carriage; therefore the method for calculation provided can
be repeated for each carriage. Table 9 below shows the maximum forces and moments that can be
applied to the carriage selected and this can be used in conjunction with Figure 42 to define the
direction of each (Hepcomotion, 2012).
Table 9 - Carriage specification for AURD12833W (Hepcomotion), Maximum Loads and Moments.
Carriage
Part
Number
Dry System
L1 (max)
N
AU… 12833W…
40000
L2 (max)
Ms (max)
Mv (max)
M (max)
N
Nm
Nm
Nm
60000
6530
16650
11100
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Figure 42 - Forces and Moments on the Carriage (Hepcomotion)
Firstly, the carriages on the x-axis will be considered (X004). The carriage supporting the robotic
arm has the moment Ms acting upon it. The forces due to the masses can be calculated using Equation
14 below.
𝐹 = 𝑚𝑎
Equation 14
Where F is the force applied due to the mass, m is the mass of the fixed system and a is the
acceleration due to gravity.
The mass of the robotic arm is 98kg and the mass of the motors is 4.1kg. Taking a to be 9.81m/s2,
the force applied from the robotic arm and from the motor can be calculated to be 961.38N and
40.22N respectively. Subsequently, the moment applied to the carriage can be calculated using
Equation 15 below.
𝑀 = 𝐹𝑑
Equation 15
Where M is the moment and d is the perpendicular distance from the axis of rotation to the where
the force is applied.
The centre of gravity of the robotic arm can be estimated to be 355mm from the base. The distance
from the centre of the bearing to the outer edge of the carriage is 58mm. Therefore the value of d for
the robotic arm is 0.413m. In addition, the centre of gravity of the motor is 25mm from the base.
Therefore the value of d for the gearbox and motor is 0.083m. A visual set-up for these figures can be
seen in Figure 43 below.
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Figure 43 - Carriage Holding Robotic Arm for Ms Calculation.
Applying these values provided to Equation 15, the value of Ms can be calculated to be 140.82Nm.
Furthermore it is necessary to calculate the value of Mv for the same carriage. The forces acting
upon the carriage will be the same as previously calculated, however the distances will change as this
moment acts in a different plane. The value of d for the robotic arm is 0.2m from the centre of the
carriage and for the motor the value is 0.29m. Substituting these values into Equation 15 gives the
value of Mv to be 180.61Nm.
The force L1 for this carriage can be assumed to be negligible as there is no force that directly acts
through this axis. In addition, the moment M can also be assumed to be equal to zero as no moment
would occur due to the orientation of this carriage.
The force L2 can be calculated by assuming that the mass of the parts fixed to the carriage (X005
and BPP001), the drive flange assembly (X007) and carriage itself (X004), act through the radius of
the bearings. This mass is 170.7kg which equates to a force L2 of 1674.57N.
Comparing these calculated values to the maximum specified in Table 9, it can be seen that this
particular carriage will not fail under this application.
Table 10 below shows the forces and moments that will be applied to each carriage during
operation. All calculations were carried out using the same method as above. An assumption that has
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been made for simplicity in these calculations is that the forces and moments applied to the two Y003
carriages are equal as they are both supporting the same mass.
Table 10 - Loads and moments applied to all carriages used for the printer.
Part
Number
Specific Use
L1 (N)
L2 (N)
Ms (Nm)
Mv (Nm)
M (Nm)
Supporting Robotic Arm
Negligible
1674.57
140.82
180.61
0
Supporting Nozzle
Negligible
1644.16
199.01
3.62
0
9809.46
Negligible
Negligible
0
2837.48
9809.46
Negligible
Negligible
0
2837.48
Negligible
Negligible
0
Negligible
0
Negligible
Negligible
0
Negligible
0
X004
Supporting X-Axis and
Z-Axis (Right)
Supporting X-Axis and
Z-Axis (Left)
Supporting
X-Axis
(Right)
Y003
Z004
Supporting X-Axis (Left)
In addition to what has been mentioned previously, it is necessary that the values calculated for the
Z004 carriages are explained. The values of L1 and L2 are assumed to be negligible as there is no
force that directly acts through these axes as they are both perpendicular to the applied force. The
moment Ms can be assumed to be equal to zero as no moment would occur due to the orientation of
this carriage. For the calculation of the moment Mv, it has been assumed that both the beam and the
motor are fixed centrally to this carriage and therefore the values of d required to calculate this
moment are approximately equal to zero; this signifies that this moment is negligible. The moment M
for the Z004 carriages can be calculated as shown in Figure 44.
A
∑R = ∑F
B
5.5m
RA + RB = F
RA
where
RA = RB
RA = RB = 581.89N
RB
Taking Moments About A:
F = 1163.78N
∑M = (1163.78 × 5.5) – (581.89 × 11) = 0
11m
Figure 44 – Moment (M) Calculation for Z004 Carriage
Comparing Table 10 to Table 9, it can be seen that no force or moment that will be applied to a
carriage during operation of the printer will exceed the maximum specified. Therefore no carriage
will experience failure.
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6.1.2
Group 2
V Bearings
The forces applied to the bearings also require comparison with the maximum specified. The
bearings that are operational in this printer are part numbers X009 and Z008. Table 11 shows the
maximum forces that can be applied axially and radially to the bearing selected and a value for the
basic life of the bearings. Figure 45 shows a basic diagram of the direction of the forces
(Hepcomotion, 2012).
Table 11 - Bearing specification for HJ128 (Hepcomotion), Maximum Loads and Basic Life.
V Bearings
…HJ128…
Dry
LA (max)
LR (max)
Basic Life
N
N
km
10000
30000
500
Figure 45 - Loads on Bearings (Hepcomotion)
In order to carry out this analysis, some assumptions must be made. The first is that rather than
applying moments to the bearings, a point load will be applied through the radius of the bearing
instead. Due to the system being in vertical equilibrium, this assumption is valid.
The second assumption to be made is that the force applied is equally split between two bearings.
Despite four bearings being attached to the carriage, the uppermost two can be assumed to carry the
entire load and the lowermost two can be assumed to carry no load. In reality, each bearing attached
to the carriage would experience different forces, however it can be assumed that the difference
between the two upper bearings would be negligible for this calculation.
Initially, the bearings attached to the carriage supporting the robotic arm (X004) will be
considered. As previously mentioned, the mass of the robotic arm is 98kg and the mass of the motor
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is 4.1kg. In addition, the mass of the carriage plate and drive flange with pinion are 60kg and 8.6kg
respectively. This gives a total mass of 170.7N and by using Equation 14, the radial force (LR) applied
can be calculated to be 1674.57N. Taking into account the second assumption, the radial force on
each individual bearing is 837.29N.
For the bearings attached to this carriage, the axial force (La) is assumed to be negligible as there
is no force that directly acts through this axis. Therefore, comparing the radial force calculated to the
maximum specified in Table 11, it can be seen that these four bearings will not fail for this
application.
Table 12 below shows the forces applied to all the bearings used in the printer structure. All
calculations were carried out using the same method as above.
Table 12 - Loads Applied to all Bearings Used for the Printer.
Part
Number
Specific Use
LA (N)
LR (N)
Supporting Robotic Arm
Negligible
837.29
Supporting Nozzle
Negligible
822.08
Supporting
(Right)
Negligible
0
Negligible
0
X008
Z008
X-Axis
Supporting X-Axis (Left)
When observing the orientation of the Z008 bearings, it can be seen that the load LR is assumed to
be equal to zero as the pinion would have to withstand the force and not the bearing. In addition, the
load LA can be assumed to be negligible as there is no force that directly acts through this axis.
Table 12 can be compared with the manufacturer specifications in Table 11 to confirm that no
bearing will encounter failure during this application.
6.1.3
Bearing Blocks
The bearing blocks (Y005 and Y006) will be analysed in this section; these bearing blocks act as
the movement for the y-axis and will be need to hold the majority of the mass of the entire structure.
The forces applied will be compared with the manufacturer specifications shown in Table 13 below.
This can be used in conjunction with Figure 46 to show the position at which the loads take effect
(Hepcomotion, 2012).
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Table 13 – Bearing Block Specification for MHD89B (Hepcomotion), Maximum Loads.
Bearing Blocks
MHD89B…
Static Load
L1A (max)
L2 & L1B (max)
N
N
70000
21000
Figure 46 - Loads on bearing blocks (Hepcomotion)
Two assumptions will need to be made in order to carry out the analysis of the bearing blocks. The
first is that the load applied, due to the mass of the x-axis and z-axis, will be equally distributed
between the two carriages at the base of the structure. The second assumption is that the load on each
carriage will be equally split between the four bearing blocks fixed to it; the difference between the
loads on each bearing block will be small therefore this difference can be assumed to be negligible.
The mass of x-axis and z-axis is 3459.82kg and the mass of the two motors is 270kg, therefore,
using Equation 14, the force applied due to this mass can be calculated to be 3729.82N. Taking into
account both assumptions made, the load on each bearing block due to this mass (L1A) can be
assumed to be 466.23N.
In addition, it can be assumed that the load L2 is negligible as the load applied can be assumed to
act directly over the bearing blocks so there is no moment applied to create a horizontal force.
Furthermore, the load L1B can be assumed to be equal to L1A due to Newton’s Third Law of Motion.
Comparing this value with the maximum value specified by the manufacturer in Table 13, it can be
established that the bearing blocks will not experience failure when used for this printer.
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6.1.4
Group 2
V-Slides
The v-slides will be analysed in this section. These v-slides are bolted to the beam and are used for
the x-axis and z-axis. The forces applied will be compared with the manufacturer specifications
shown in Table 14. This can be used in conjunction with Figure 47 to show the position at which the
loads take effect (Hepcomotion, 2012).
Table 14 - V-slide specification for HSS33 (Hepcomotion), maximum loads.
V-Slides
…HSS33…
System Load
L1 (max)
L2 (max)
N
N
40000
60000
Figure 47 - Loads on v-slides (Hepcomotion).
Initially the v-slides supporting the carriage holding the robotic arm (X002 and X003) will be
considered. A similar assumption to one that was made in the v-bearing analysis is that in order to
calculate L2, a point load will be applied through the radius of the bearing instead of a moment. Due
to the system being in vertical equilibrium, this assumption is valid.
As previously mentioned, the total mass of parts supported by this system is 170.7kg and by using
Equation 14, the force L2 can be calculated to be 1674.57N. In addition to this, the load L1 can be
assumed to be negligible as there is no force that directly acts through this axis.
Table 15 below shows the forces applied to all the v-slides used in the printer structure. All
calculations were carried out using the same method as above.
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Table 15 - Loads applied to all v-slide systems used for the printer.
Part Number
Specific Use
L1 (N)
L2 (N)
Supporting Robotic Arm
Negligible
1674.57
Supporting Nozzle
Negligible
1644.16
Supporting X-Axis (Right)
Negligible
0
Supporting X-Axis (Left)
Negligible
0
X002 and X003
Z002 and Z003
Due to the orientation of the Z002 and Z003 v-slides, it can be seen that the load L2 is assumed to
be equal to zero as no force acts through this axis. In addition, the load LA can be assumed to be
negligible as there is no force that directly acts through this axis.
Table 15 can be compared with the manufacturer specifications in Table 14 to confirm that no vslide will encounter failure during this application.
6.1.5
Beams
In order to verify the use of the selected beams, it is necessary to use the program ANSYS in order
to prove that each beam will not fail under this application. Each beam will be modelled in the CAD
program Solid Edge and then the necessary forces will be applied in ANSYS in order to determine the
stresses that will act upon all parts of the beams.
The first beam to examine will be the part X001. The beam that was used in ANSYS had a
simplified rectangular cross-sectional area. This was due to the version of the software that the group
had access to not allowing the use of a beam with such a complex cross-sectional area. The beam
used instead can be seen in Figure 51. It was assumed that this would not significantly affect the
results obtained.
It can be assumed that the maximum stresses will occur when the force of the robotic arm and
nozzle act directly in the centre of the beam. Therefore a force of 3554.16N (calculated from the total
mass of the carriages, motors, pinions, nozzle and robotic arm, etc.) can be applied to the beam. In
addition, the beam is fixed at both ends. Figure 48 below shows the results given by ANSYS.
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Figure 48 – Stress Analysis Results for X001 Beam using ANSYS
It can be seen that the maximum stress that occurs along the beam is 3.79MPa and this acts at the
ends where the beam is fixed to the carriages.
The manufacturer of this beam states that this beam is made of a ‘high strength aluminium alloy’
(Hepcomotion, 2012), however the specific alloy is not given. Therefore, for the purpose of
verification of this part, it will be assumed that this alloy is 6082 as this alloy is of medium strength
(AALCO, 2012).
Due to this assumption, the yield strength of this material is 250MPa (Matweb, 2012). This is the
point where the beam will begin to deform and any deformation is unacceptable. Comparing this to
the value calculated by ANSYS, it can be seen that this beam (X001) will not fail under this
application as the maximum stress that will be experienced by the beam does not exceed the yield
strength of the material.
The other beams to be considered are the Z001 beams. In order to calculate the stresses applied to
these beams, it will be assumed that the carriages supporting the robotic arm and nozzle will be
positioned centrally and therefore the force applied to each beam will be equally split between them
(as they are both supporting the mass). In addition, it will be assumed that the force acts directly upon
the end of the beam; this is for simplicity when using ANSYS. This scenario will result in an overestimate of the maximum buckling conditions that would be experienced by the beam and therefore,
this assumption is acceptable.
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The force applied to each beam is 11416.68N which is calculated from the total mass of all x-axis
parts. In addition, the beam is fixed at the base. Figure 49 below shows the results given by ANSYS.
Figure 49 - Stress Analysis Results for Z001 Beam using ANSYS
It can be seen that the maximum stress that occurs along the beam is 1.19MPa and this acts on the
face that the force is applied to. This beam is made of the same aluminium alloy as the X001 beam,
therefore the alloy can be assumed once again to be 6082 with a yield strength of 250MPa.
Comparing the yield strength of the material to the maximum stress that occurs under this application,
this beam will not fail.
The final beam Y008 that has the flat tracks mounted to it is supported along its entire length by
the ground and therefore no deformation will occur.
6.1.6
Pinions
In this section the pinions will be analysed to ensure that they will not fail under this application.
This analysis will be carried out using hand calculations and the use of ANSYS.
The z-axis pinions will have to withstand the majority of the force applied due to the total mass of
the x-axis and the z-axis carriages (Z004), drive flanges (Z006), motors (Z005) and bearings (Z008).
An assumption to be made is that this force is equally split between the two pinions, as this analysis
will take place with the force due to the mass of the robotic arm and nozzle carriages acting centrally.
In order to verify this choice of pinion, analysis of the teeth is required to check that they will not
fail. This will be performed using ANSYS. An assumption, required for simplicity when using the
computer program and for verification of the teeth, is that the force applied to the pinion acts through
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a single tooth. In reality, this force would be split between several teeth, therefore reducing the force
applied to individual teeth. However if a single tooth can withstand the total force, then no teeth will
fail. Consequently the pinion will not fail during this application.
The mass that both pinions will be supporting is 1784.98kg. Therefore, after taking into account
the first assumption, the force applied to each pinion is 17510.65N. Figure 50 below shows the results
given in ANSYS when this force is applied to a single pinion tooth.
Figure 50 - Stress Analysis Results for Z-Axis Pinions using ANSYS
It can be seen that the maximum stress that will be experienced by this tooth is 151MPa.
The manufacturer of these pinions states that they are made of ‘high grade case hardened steel’
(Hepcomotion, 2012); the yield strength of this material is 613MPa (Engineer's Handbook, 2006). As
the value of maximum stress given by ANSYS is smaller than the yield strength of the material, it can
be deduced that this pinion will not fail under this application.
This pinion would also experience a force due to the acceleration, however this calculation is not
required to be performed as the maximum acceleration of this motor is less than the acceleration due
to gravity. Therefore a smaller force would be used than in the previous calculation.
In addition to these pinions, verification of the x-axis pinions is required as well. The maximum
force applied on the pinions in the x-axis will correspond to the acceleration of the carriage using
Equation 14. For the x-axis, the nozzle carriage will be analysed. The greatest acceleration that this
carriage will experience is 10m/s2. The total mass of the parts for this system which require moving
by the motor is 191kg (mass of carriage, nozzle, motor, drive flange and bearings). This equates to a
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force of 1910N. The same pinion is used for this system as with the z-axis system and therefore, as
this force is much smaller than the force used previously, it can be said that this pinion will not fail
under this application.
The robotic arm carriage would have a maximum acceleration of 1m/s2 and therefore, similarly to
the nozzle carriage, the force calculated for this system would not exceed the force applied to the zaxis bearing. This pinion will not fail under this application.
This situation is identical for the Y-axis pinions. The force that would be applied is 4973.78 and
this is smaller than the value used in the z-axis, therefore this pinion will not fail under this
application.
6.2
Beam Vibrational Analysis
It is necessary to calculate the natural frequencies of the printer in order to confirm the choice of
operating frequencies for the motors. Initially we can calculate this for the part X001. The bar
supplied by HepcoMotion is not regular in shape however, so a simplified rectangular cross-section
based on the dimensions of the product can be used for this purpose. It was assumed that this
assumption would not significantly alter the determined frequencies. This is shown in Figure 51
below where t is the wall thickness.
t = 0.01m
d = 0.3m
L = 11m
b = 0.2m
Figure 51 - Simplified diagram of the HB33 bar supplied by HepcoMotion.
The bar is made of a high strength aluminium alloy with the Young’s Modulus (E) equal to 66GPa
(HepcoMotion, 2012) and the density (ρ) equal to 2770kg/m3 (EngineeringToolbox, 2011). In
addition, the bar is considered to be fixed at both ends.
Using the dimensions provided in Figure 51 the cross sectional area (A) can be calculated to be
9.6×10-3m2. The moment of inertia (I) is also required and can be calculated using Equation 16.
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Equation 16
𝐼=
𝑏𝑑
12
Using the values provided in Figure 51, the moment of inertia (I) can be calculated to be
1.207×10-4m2. Subsequently, Equation 17, Equation 18 and Equation 19 (Gruber, 2011) shown below
can be combined to give Equation 20.
Equation 17
𝑐=√
Equation 18
𝛽 𝐿=
𝐸𝐼
𝜌𝐴
(2𝑛 + 1)𝜋
2
𝜔 = 𝑐𝛽
Equation 19
Equation 20
𝜔 =√
𝐸𝐼 (2𝑛 + 1)𝜋
(
)
𝜌𝐴
2𝐿
Where ωn is the natural frequency and n is a constant related to the natural frequency required
during the calculation.
Inputting the values already obtained into Equation 20 and taking n to be equal to 1 (in order to
find the first natural frequency of the bar), the first natural frequency of the bar (ω1) can be calculated
to be 15.99Hz. Subsequently, and by using the same method as above, the second and third natural
frequencies of this bar can be found to be 44.41Hz and 87.04Hz respectively. This can be repeated
many more times to find other values for the natural frequencies of the bar.
Following this, it is vital that this calculation is repeated for the other beams in the printer
structure. The part Z001 has the same breadth, depth and wall thickness and is made of the same
material as X001, however the length is 8m. This means that the values of E, I, ρ and A are kept the
same. Using these values and changing the value of L gives the first three natural frequencies of the
two beams to be 30.22Hz, 83.96Hz and 164.56Hz.
These calculations are a necessity when confirming the choice of operating speeds of the motors.
If a motor runs at the same frequency as the natural frequency of a beam then the phenomenon of
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resonance will occur. Therefore a motor can pass through these frequencies, however operation at
these frequencies should be avoided.
6.3
Beam Deflection Analysis
The maximum deflection that will be experienced by the X001 must be calculated. This can be
executed using energy analysis of beams. Figure 52 below shows the set-up of the HB33 beam
supplied by Hepcomotion. For this application the beam is built-in at both ends.
Figure 52 - Diagram Used for Deflection Analysis to Show Built in Set-Up of HB33 Beam Supplied by
Hepcomotion.
This is where L is the beam length, w is the beam deflection, F is the force applied by the weight
of the nozzle and robotic arm and x is the axis.
Initially, a trial function for this arrangement is required; this can be seen in Equation 21 below
where k is a constant.
Equation 21
𝑤(𝑥) = 𝑘 (1 − cos
2𝜋𝑥
)
𝐿
The maximum deflection that will be experienced by the beam will occur at the midpoint; when
x=L/2. Therefore substituting this into Equation 21 gives:
Equation 22
𝑤 ( ) =2k
This trial function shown in Equation 21 is then differentiated twice and used for calculating the
strain energy of the beam (U) using Equation 23 (Crocombe, 2012).
Equation 23
𝑈=
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𝐸𝐼
𝑑 𝑤
∫ (
)
2
𝑑𝑥
𝑑𝑥
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Following this, the potential energy of the beam (V) is calculated using Equation 24 (Crocombe,
2012).
𝐿
𝑉 = −𝐹𝑤 ( ) = −2𝐹𝑘
2
Equation 24
Subsequently, the total energy is calculated by adding the strain energy (U) and the potential
energy (V) together. This value is then differentiated with respect to the constant (k), put equal to zero
and rearranged to give an equation in terms of k. Substituting this equation into Equation 22 gives the
maximum deflection of the beam to be as shown by Equation 25.
𝐿
𝐹𝐿
𝑤( ) =
2
2𝐸𝐼𝜋
Equation 25
The beam being analysed for deflection is the same as shown in Figure 51, therefore L is 11m, E
is 66GPa and I is 1.207×10-4. The force (F) being applied is the maximum force due to the mass of
the robotic arm, nozzle, carriages, motors, etc. when acting through the centre of the beam. This force
can be calculated using Equation 14, to be 3072.49N using the values of weight provided in the
materials list in Appendix 7. Substituting these values into Equation 25 gives the maximum deflection
of this beam to be 2.63mm.
It can be assumed that this deflection will not significantly affect the printing of the building. As
this deflection will only affect the height between the nozzle and the printing surface, a change in
2.63mm will not impede the laying of the concrete. This is less than 10% of the desired printing
height of the nozzle, therefore this is acceptable.
6.4
Fatigue Analysis
In order for fatigue cracks to occur a cyclic loading condition must occur. This loading must first
of all have a minimum range between its maximum and minimum stresses and also its absolute
maximum (either tension or compression) must be at least a certain magnitude. If the first two
conditions are met then a large enough number of cycles are needed for a crack to be initiated and
propagated until the critical failure of the member. Figure 53 shows various loading conditions which
could lead to fatigue cracks.
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Figure 53 - Loadings Which Could Cause Fatigue Cracks (Non Destructuve Testing Resource Centre,
2013)
There are other considerations besides whether the absolute stresses are of a fixed magnitude; if
there are large stress concentrators or corrosion or temperature then that magnitude will decrease
making cracks more likely to initiate.
For some materials there is a stress amplitude for which fatigue will never occur if it is below that
limit, this is called the fatigue limit (Department of Materials Science and Engineering - University of
Arizona, 2013). The fatigue limit varies from material to material but for aluminium alloys with a
strength of less than 280MPa (the aluminium alloy used in the printer has a strength of 250MPa) then
the fatigue limit is 38% of the tensile strength based on a 5 x 108 cycle life (Beardmore, 2010). This
puts the fatigue limit for the aluminium used in the printer at 95MPa.
In the case of the printer, the stresses experienced in the main members are 3.79MPa in X001 and
1.19MPa for Z001. This is well below the fatigue limit of the aluminium in both cases and so unless
there is already existent cracks in the beams then fatigue should not occur.
6.5
Part Life Analysis
Part life analysis must be carried out to assist with the sustainability of this project. The
manufacturer of the selected parts, HepcoMotion, provides load life calculations for the carriage and
v-bearing systems. These can be used to calculate the life of each system.
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Initially, the load factor (LF) must be calculated using Equation 26.
Equation 26
𝐿 𝑎𝑑 𝐹𝑎𝑐𝑡 𝑟 (𝐿𝐹) =
𝐿
𝐿
𝑀
𝑀
𝑀
+
+
+
+
𝐿 (𝑚𝑎𝑥) 𝐿 (𝑚𝑎𝑥) 𝑀 (𝑚𝑎𝑥) 𝑀 (𝑚𝑎𝑥) 𝑀(𝑚𝑎𝑥)
All values required for this calculation can be found in Table 9 and Table 10.
Following this, the life of the system must be calculated using Equation 27 below.
Equation 27
𝐿𝑖𝑓𝑒 (𝑘𝑚) =
𝐵𝑎𝑠𝑖𝑐 𝐿𝑖𝑓𝑒
(0 04 + 0 96𝐿𝐹)
Where the basic life relates to the v-bearings; this value can be seen in Table 11. Once the value
for the life of the system (km) is obtained, a value of how long the time will last in terms of time can
be determined using an estimation of the distance travelled by the system in a week.
The first carriage and bearing system that will be analysed are the x-axis parts X004 and X009.
For this example the focus will be on the carriage supporting the robotic arm. From the values given
in Table 9 and Table 10, the load factor can be calculated using Equation 26 to be 0.0603. This value
can then be used in Equation 27 to calculate the life of this system. The resulting value is
52180.84km.
It can be estimated that this system will travel at 0.5m/s for 116hours/week (assuming that the
printer runs for 24 hours a day and will approximately 70% of the time). Using these two values, it
can be calculated that this system will travel a value of 208.8km/week. Taking the value of
52180.84km for the life (km) and dividing this by the value of 208.8km/week for the distance
travelled by the system in a week, gives the life of this system to be 249.91 weeks; this equated to
4.81 years when printing every day of the year.
This method was repeated for the load lives of the other carriage and v-bearing systems. The
results of these calculations can be seen in Table 16 below.
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MDDP – Megascale 3D Printing
Group 2
Table 16 - Life of each carriage and v-bearing system.
Part
Number
Specific Use
Life of System (years)
X004
/ X008
Supporting Robotic Arm
4.81
Supporting Nozzle
35.74
Z004
/ Z008
Supporting X-Axis (Right)
Negligible
Supporting X-Axis (Left)
Negligible
The Z004/Z008 systems are negligible as when taking the values from Table 10 to use in Equation
26, it can be seen that the results for the load factor would be extremely small and in turn, the life
(km) would be extremely large. Due to this, it can be assumed that the resulting life of the z-axis
carriage and bearing systems would be negligible as this value would be very large.
6.6
Analysis Conclusion
It can be seen that all calculated values are much less than the maximum specified by the
manufacturer. Due to this, it could be suggested that smaller parts should be selected from the
manufacturer to optimise the structure and reduce the overall cost of the printer. However, the reasons
behind selecting such parts were based on the dimensions of the carriages. These carriages were
required to be large enough to attach with ease other parts such as the nozzle and robotic arm.
Reducing the dimensions of these carriages would make the attachment process much more complex
and perhaps impossible.
Another point to consider is that ANSYS is not 100% accurate. However, this inaccuracy is very
small and therefore can be ignored. All values for maximum stress calculated by ANSYS are much
lower than the individual yield strengths of the materials, therefore the results obtained are verified
for use.
7 PROTECTION AND TRANSPORTATION OF PRINTER
7.1
Environmental Protection
Excess water could be a major problem for printing, both for maintaining the strength and setting
time of the concrete and also for the strength and lifetime of the printer. The setting time of the
concrete is at least partially dependent on its water content and with incorrect setting times it may be
that the structural strength may deteriorate. Also, due to how the printing is done, when the 3cm parts
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of the wall are printed, rain could start to fill up the subsequent enclosed section and ruin the wall.
Since several components of the printer will be constructed from steel it is also a risk that these
components could begin to rust and cause the printer to lose performance or even break.
One way of reducing the risk of rust is to apply a surface coating to the steel components so that
the steel itself is protected from the elements. Galvanised steel has a coating of zinc applied to it,
usually in a hot dip bath, which protects it from corrosion as the steel itself is no longer in contact
with the atmosphere. This coating should then protect the steel from corrosion for between 40 and 70
years in an external UK environment. (Medway Galvanising Company, 2011).
To both protect the printer and the printing area, a temporary canopy could be erected such as in
Figure 54. This particular enclosure measures up as 18m wide, 9.75m central height and 49m long.
These are not the desired measurements for this project but the shape and proportions are of a similar
nature and show that a contained canopy of the magnitude this project requires is perfectly feasible.
Having an enclosed structure such as this will completely protect the printer from the elements but
will affect the ambient conditions inside. This could be detrimental to the printing and printer if
humidity becomes too high so an air conditioning unit may be advisable.
Figure 54 – Environmental Containment Project - North East, United States (Big Top Manufacturing,
2012)
7.2
Printer Assembly and Transportation
The printer was designed in a way to enable simple assembly. The majority of parts are bolted to
one another and therefore this can be performed on site. Despite this being a potentially time
consuming solution, it was decided that this would be the simplest option.
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The mounting plates (Y008) for the printer will be required to be placed into the pre-dug tracks
either side of the printing area. From this, initial fixing of relevant parts can take place. Following
this, a crane would be required to lift the two z-axis beams (Z001) into place for further bolting to
take place. Subsequently, the crane would also be required to hoist the x axis beam (X001) into place
so that bolting can take place to the carriage plate on the z-axis (Z004). This bolting would be
performed by a contractor using a cherry picker.
Deconstruction of the printer post-print would require the same approach using the same
equipment. It can also be assumed that the same number of contractors would be required and the
time taken would also be the same.
Due to the length of the beams, it would be necessary for an arctic lorry to be used for
transportation. It can be assumed that the crane would be required to lift the beams into the lorry.. An
additional contractor would be required to drive the lorry from storage to site.
As this printer was designed for the mass-production market, it can be assumed that any site
chosen would be suitable for the printing of numerous houses. Therefore, once transportation to the
site has occurred, the arctic lorry would not be required again until the completion of all the houses on
the site. This greatly reduces transportation costs and therefore a lorry could be hired instead of
purchased. The cost of hiring an arctic lorry for four days is £200 (Nation Wide Hire UK, 2012),
therefore this value can be used in the finance section of this report.
8 ELECTRONICS
Motors
8.1
8.1.1
Motor requirements
The role of the motors is to transform electrical energy into mechanical energy. In the case of the
3D printer, 6 motors will be required:
-
2 for the X-direction: one for the nozzle and one for the robotic arm;
-
2 for the Z-direction: one on each side of the horizontal bar of the printer;
-
2 for the Y-direction: one on each rail.
The reason behind two motors for the Z and Y-directions is to divide the work between the two
motors and to provide smoother movement.
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The motors in each dimension will have different requirements depending on the weight of the
part of the printer it is responsible for moving, which includes; the precision, speed and acceleration
needed in each direction.
8.1.2
Parameters
Figure 55 - Graph Showing Motor Torque - Speed Relationships (Magnetic Spa, 2012)
Table 17 - Motor Parameter Definitions
Continuous torque that can be supplied by the motor while
running at a speed near zero.
Continuous torque that can be supplied by the motor while
Nominal Torque Tn
running at nominal speed.
Max Torque Tp
Acceleration torque that can be supplied by the motor.
Nominal speed value. Speed at which the maximum torque
Nominal Speed Nn
is guaranteed to be above Tn0.
Power Pn
Power value referencing nominal speed and torque.
Since losses increase with the motor speed, the continuous
Area 1
torque decreases as demonstrated in Figure 39.
Considers the range at which the maximum torque can be
Area 2
supplied. This depends on the maximum voltage that can be
supplied by the converter.
Stall Torque Tn0
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Table 18 below summarises the requirement for each motors:
Table 18 - Motor Requirements
Power Required
(Nm)
Angular Velocity, ω
(m/s 2 ) (N)
Angular Velocity, ω
(s)
Torque, τ
(m)
Maximum Force
Required at Pinion
(kg) (m/s) (m/s)
TimeTravelled
Before
Reaching
Steady
Velocity, Tacc
Acceleration
Non-Printing Speed
Vd
X (Nozzle)
Printing Speed Vp
(m)
Mass
Radius
Axis
Distance
Travelled
Before
Reaching
Steady
Velocity,
Dacc
(rad/s) (rpm) (kW)
0.07 300 0.1
1
0.001
0.01
10
3059
198.83 15.38
146.9 3.06
X (Robotic Arm) 0.07 200 0.1
1
0.01
0.1
1
239
15.55
15.38
146.9 0.24
Y
0.07 4000 0.1
1
0.1
0.2
2.5
10785 701.01 15.38
146.9 10.8
Z
0.07 1800 0.05 1
0.001
0.1
0.1
17838 1159.5 15.38
146.9 17.8
To decide on a motor, some values such as the torque needed at the pinion and the velocity
need to be decided. Then, the motor will be chosen so that its parameters match with the values
wanted.
8.1.2.1
X-Axis – Nozzle & Robotic Arm Motion
The nozzle assembly including carriage and motors can be taken to be 300kg. This 300kg is
required to move at a constant speed of 0.1ms-1 when printing concrete and have increased velocities
for other movement such as moving between printing areas. The accelerations required will be high as
the printing velocities and traversing velocities should be reached quickly to ensure uniform concrete
extrusion and to minimise printing time respectively. This means a maximum speed in the range of
1ms-1 and accelerations of 10ms-2 (1g) would be desired. The coefficient of friction for the rails the
carriage traverses along is 0.02 (Hepcomotion, 2012) and resistive forces due to air resistance will be
neglected due to the low speed of operation.
Using Equation 28 with ‘R’ as 2943N and ‘a’ as 10ms-2, the force required to achieve this
acceleration is 3059N.
𝐹 = 𝑚𝑎 + 𝜇𝑅
Equation 28 - Force Equation for X axis
The rack and pinion system which provides the linear motion of the carriage has a pinion
with a radius of 0.065m. This means using Equation 29 the required torque at the pinion is 195Nm.
This torque corresponds to a speed of around 15.38rads-1 (using Equation 30).
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Equation 29 - Relationship Between Torque
𝑇 = 𝐹𝑑
𝜔
𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑇𝑟𝑎𝑣𝑒𝑙𝑙𝑒𝑑 = 2𝜋𝑟 ×
= 𝑟𝜔
2𝜋
and Force
Equation 30 - Relationship Between Pinion
Rotation and Linear Displacement
The same constant speed of 0.1m.s-1 is required for the mechanical arm, as placing
reinforcement will take some time. A higher velocity (1 m.s-1) can be achieved when the mechanical
is not carrying anything. Since the mechanical arm has to carry objects, the acceleration will have to
be lower than for the nozzle for stability issues. From Equation 28, using the same ‘R’ and with an
acceleration of 1 ms-2, the force required to achieve this acceleration is 239N.
8.1.2.2
Z-Axis – Vertical Motion
The mass of the printer gantry is 1515kg but the calculations on its up and down movement
will vary based on the mass of the motors chosen to fulfil the task. If the mass of the motors as a
preliminary estimate is assumed to be 300kg (and so a total mass of 1815kg) then some rough
requirements can be stated. The accelerations and speeds required can be much lower than those of
the other axis as under normal operating conditions, rapid vertical movement will not be needed – the
normal movement being 3cm intervals every hour or so. Using Equation 31, to achieve an
acceleration of 2.5ms-2 a force of roughly 17838N, or a torque at the pinion of 1159.47Nm, using
Equation 29, is required. This will be split between 2 motors (one at each end of the gantry) so each
will need to provide 580Nm at the pinion and weigh 150kg to fit the previous assumptions.
𝐹 = 𝑚𝑎 + 𝑚𝑔
8.1.2.3
Equation 31 - Force Equation for Z Axis
Y-Axis – Horizontal Motion
Moving the whole structure is what will require the most power. The printer weights around
4tones and is required to move up to 1m.s-1 with an acceleration of 2.5m.s-2. The whole printer will
have to move at 0.1m.s-1 most of the time to keep up with the nozzle. So, using Equation 31, the force
required at the pinion 10785N or a torque of 701.01Nm is required. The same way as the Z direction,
this torque will be distributed over two motors. This means that each motors need to have a torque of
350Nm.
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8.1.3
Group 2
AC vs DC
There are two big categories of motors: AC motors and DC motors. Overall, AC motors are
more reliable and more resistant than DC motors. Less maintenance is required and that makes them
cheaper. However, DC motors are easier to control in terms of speed and torque.
DC motors are presumably more efficient in low speed application and for heavy loads as
they are more stable. This is why DC permanent magnet have been chosen to meet the high torque
requirements for moving such a large object.
8.1.4
Servomotors
The 3D printer application requires position and speed control of the motors. There are two
kinds of motors that allow this kind of control: stepper motors and servomotors. Stepper motors are
very precise compared to servomotors. They count the number of steps needed to get to the correct
position. However, they are not powerful enough. Also, another important drawback of stepper motor
is that they cannot correct their position.
Servomotors are motors specially designed for all kinds of automated manufacturing and robotics.
They are able to control their angular positions with an inbuilt position sensor. The actual position of
the motor is compared to the position desired. If the two values differ, an error signal is sent to the
controller
and
correction
is
made
until
the
no
error
signal
is
received.
Figure 56 - Servomechanism Diagram
The reason to use servomotors instead of a simple motor and a position sensor attached to it is
for accuracy and speed. Servomotors might be a little more expensive than a simple motor with a
sensor; however, error in position is corrected faster and more accurately. Also, the control of the
overall structure position and movement is made easier. Table 19 below shows comparisons between
each type of motor (National Instruments, 2012):
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Table 19 – Comparison of Types of Motor
Motor Type
Advantages
Disadvantages
Stepper Motors
Inexpensive, can be run
open loop, good low-end
torque, clean rooms.
Brushed DC
Servo Motors
Inexpensive, moderate
speed, good high-end
torque, simple drives.
Applications
Noisy and resonant, poor highspeed torque, not for hot
environments, not for variable
loads.
Maintenance required, no clean
rooms, brush sparking causes
EMI and danger in explosive
environments
Maintenance-free, long
Brushless Servo lifetime, no sparking, high Expensive and complicated
Motors
speeds, clean rooms, quiet, drives.
run cool.
8.1.5
Positioning, micromovement.
Velocity control, high-speed
position control.
Robotics, pick-and-place, hightorque applications.
Motor choice
The motors chosen for this project are taken from the company Magnetic Spa (Magnetic Spa, 2012)
and are all permanent magnet ac motors. The chosen motor parameters are shown below in Table 20:
Table 20 - Chosen Motor Parameters
Motor
Code Pn (kW) Tn0 (Nm) Tn (Nm) Tp N(m) J (Kgcm2)
HTQ 240 S TENV
HTQ 300 S TEWC
HTQ 120 M TENV
HTQ 300 M TEWC
AD
AH
4A
AF
8.1.6
2.7
13
0.31
17
52
290
7.3
580
43
275
6.6
548
200
500
24
1000
465
1580
27
2920
Nn
RPM(rads -1)
600
450
450
300
Nmax@Tp RPM
-1
(rads )
280
360
220
230
No. poles W (kg) Printer Part
20
20
14
20
45
135
4.1
230
Nozzle
Y Axis
Arm
Z Axis
X-Axis – Nozzle & Robotic Arm Motion:
This is four times greater than the stall torque Tn0 of the HTQ 240 S TENV motors so a gear ratio
of 4:1 would be implemented between the motor and the pinion to achieve the desired torque with
near zero velocity. This also means that when the motor is running at its nominal velocity of 62.8rads 1
, the gearing translates this to 15.7rads-1 or 1.02ms-1(using Equation 30). This means this motor is
almost perfect for our requirements when running under continuous conditions and ignoring the peak
torques and speeds that it is capable of (this also means the motor is slightly overpowered for this
application but additional cooling of the motor can be ignored and the lifetime should be extended)
8.2
Sensors
Sensors are a very important area when designing such a large machine. They will be used in
many different areas of the printing process, each of them for different reasons and applications. The
sensors will enable the printing process to be conducted in a safe manner and to ensure that the final
product is accurate.
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8.2.1
Group 2
Equipment safety
Another element of the printing process is the printer itself. Checks have to be made to ensure
that the machine is working correctly. The printer temperature, the input current are two examples of
what will be needed to be monitored and corrected if needed.
8.2.2
Precision
The aim is to build a house fit to live in. Therefore, the printing should be as precise as
possible for the safety of the future inhabitant. This implies a close monitoring of the position of the
printer, the concrete flow, and the timing of the printing process.
All of this information will be recorded and analysed. If needed, corrections will be made in
time, or the printer will be stopped until the problem is fixed.
8.2.3
Motion detectors
The monitoring system has to make sure that the staff present on the printing site are safe. For that,
a safety area will have to be determined using motion detectors. In the case of a person present in the
risk area while the printer is working, the printing will have to be stopped until the safety zone is
clear.
They are typically four types of sensors:

Infrared - Detects body heat.

Ultrasonic - Uses ultrasonic waves and their reflection to detect moving objects.

Microwave - Same principle as the ultrasonic sensors but using microwaves.

Tomographic - Radio nodes are place around the area to supervise, and the sensors look at
the disturbances of the radio waves. One advantage of this technique is that it can sense a
moving object through obstructions such as objects or walls.
While all these methods are effective, they require a reference point in order to detect any motion.
The infrared sensor needs a reference temperature and the other three need a reference point in space.
On the printing site however, these references will be difficult to obtain. This is due to the strong
temperature differences within the printer for example the motor and nozzle, which will interfere with
an infrared sensor. In addition to this if a different sensor was selected, due to the fact that the printer
will be moving, the sensor won’t be able to distinguish between the movement of the printer or nozzle
and a human.
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Due to these reasons a more appropriate solution is to use computer vision.
Software and
hardware are really advanced and the hardware relatively cheap. On the market today, there are
systems that answer to our problem: Kinect (Microsoft), Xtion PRO LIVE (Asus) or LEAP
(LEAPmotion). They can be used to detect a body in the field of view of the camera. These solutions
require being associated with a program that gives and analyses the data we require of which will be
explained in detail in the software section of this report.
For the purposes of this design the Kinect was chosen as there are numerous existing open source
projects of which already cover motion detection, and the Kinect is a popular choice amongst
developers.
8.2.4
Position sensor
The position of the nozzle will have to be monitored at all times. This will be enabled by the
servomotors that can control their position by themselves. Then a microprocessor will register the
motors states and combine them to decide if the nozzle is at the correct position and moving at the
right speed.
As well as a basic position obtained from the servo motors, an additional positional sensor is
needed, in order to obtain the motor’s relative position and to assist in the calibration of the motors
before each print. The sensor chosen for positional sensing is the E40H8-100-3-N-24 produced by
AUTONICS.
8.2.5
Temperature sensors
Temperature sensors are useful to protect motors from overheating, which can damage the motor
potentially causing it to malfunction.
Servomotors, such as the one used, can come equipped with a temperature control process, which
shuts down the motor automatically in case of overheating. This emergency shutdown is not desired
for the 3D building printer as it has multiple motors. The printer motors therefore, will have
additional temperature sensors attached to them, of which are connected to a common processor. This
processor can then stop the whole system if one of the motor starts to overheat as opposed to just one.
It is important to note that the sensor doesn’t measure the motor’s temperature but the temperature
of the environment in which it is placed. In fact, it measures the motor’s case temperature due to the
heat dissipated by the motor. A threshold temperature therefore will need to be calculated in order to
allow for this difference between the case temperature and the temperature of the motor itself.
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Figure 57 below shows a comparison between the temperature of the motor’s windings and the
case of the motor.
Figure 57: Dynamic Winding and Case Temperature of a Motor (Motors Drives)
Using this, the temperature error can be calculated and applied to the temperature recorded at the
sensor attached to the motor’s casing.
The motors used for the printer will work in an intermittent manner with a stop and start period.
The increase in temperature is not linear and it can be seen from the graph above that when the motor
is first turned on the gradient of the temperature curve is large and then begins to fall. This all needs
to be taken into account when calculating the error as mentioned above.
To ensure efficiency and minimize power usage, the motors will need to operate at maximum
torque for as long as possible at which the windings will increase in temperature significantly.
All these factors complicate the temperature monitoring of the different motors of the printer, with
the need of regular calibrations of the sensors.
The printer has several motors, so identifiable sensors have to be used. The temperature chosen is
the DS18B20 1-Wire digital temperature sensor from Maxim IC (Maxim IC - DS18B20). This sensor
has a unique 64 bit serial number which enables the program to identify each of them. A single data
bus is then needed to differentiate the sensors. Multiple sensors can then be used on the same system
with each of them having a different temperature limit for the motor it is related to. This sensor is fast
and very precise (+/-0.5°C).
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8.2.6
Group 2
Flow sensors
The flow sensor is an essential element for the quality and the robustness of the finished printed
structure. Errors in the concrete flow while printing might not present obvious errors at first that can
be fixed by someone on site. This could create potential problems with the structure in the future. It is
for these reasons therefore that a suitable flow sensor be selected for the printer.
Several parameters of the material must be taken into account for a flow sensor. Depending on the
fluid, some sensors are more suited to the respective application than others. In the case of a large
scale 3D building printer, the following parameters need to be defined:
-
Fluid physical parameters:
o
Fluid viscosity
o
Electrical conductivity
o
Thermic conductivity
o
Sonic conductivity
-
Chemical and physical parameter of the fluid: Fluid acidity, sand can damage the sensor
-
Required measure performances: The desired measurement accuracy and precision must be
defined to choose an effective sensor. In our case accuracy is important for safety reasons.
-
Financial elements: The purchase price for the sensor varies due to the features it contains.
Maintenance price should also be taken account in addition to this. It is beneficial to buy a
more expensive sensor that will last longer and that is more reliable. Especially in this case,
where errors may not be noticed at first and have important consequences later.
The desired measurement accuracy and precision must be defined to choose an effective sensor.
Table 21 shows various types of flow sensors with their specifications.
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Table 21- Specifications of Flow Sensors
03-Jan
↗↗
0,5 to 5 %
10-Jan
Electromagnetic ++ +
0,5 to 1%
10-Jan
Vortex
0,75 to 1,5%
10-Jan
Ultrason
(Doppler)
+
+
1 to 5%
10/1 to
40/1
Coriolis
0,2 to 0,4 %
25-Jan
Thermic
1%
10-Jan
-20 to
30 D
500°C
0,05 to
5 to
-200 to
1,2 m
10 D
+200°C
0,004 to
0,12 m
↗↗↗
-
0,002 to
2,6 m
0
5D
+180°C
0,3 m
25 D
+400°C
-↗
0,025 to
5 to
-200 to
4m
20 D
+200°C
↗
0,001 to
0,12 m
0
150 bar
++
+
-
-
-
-
250 bar
++
++ +
300 bar
+
+
+
300 bar
+
-
-
400 bar
+++ ++ +
400 bar
+
450 bar
-200 to
0,003 to
++ ++
40 to
15 to
0,15 m
-
+400°C
0,015 to
0
150 bar
-260 to
-30 to
-240 to
+200°C
-20 to
+180°C
+
Looking at the specification for each type of sensors, electromagnetic or Doppler are the best fitted
to control the concrete flow. Ultrasonic sensors are cheaper in every way: purchase, installation and
maintenance prices. It is however less precise than an electromagnetic sensor but it is enough for the
project. The sensor chosen is the ultrasonic flow meter PCE-TDS 100HS.
8.2.7
Accelerometer
Due to the heavy weight of the X axis which carries both the robotic arm and nozzle a safety feature
will be implemented in order to prevent the large weight from free falling and causing potential
damage to the printer and surrounding area.
To implement this fail safe an accelerometer will be attached to the respective axis in order to
measure the levels of acceleration of the axis. As the X-axis only needs to move relatively slowly in
order to complete a print, the threshold for acceleration will be fairly low and easy to identify. If the
pinion system were to fail for example the axis would accelerate at a very fast pace. Once this
threshold has been reached a catch will lock into place in order to stop the falling bar from causing
any damage.
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Maintenance Price
0,7 to 1,5 %
10 to
1m
Installation Price
Venturi
0,025 to
Purchase Price
↗↗↗
Max Pressure
03-Jan
Temperatures
0,7 to 2%
Upstream Length
Orifice
Target meter
Allowed Diameter
Head Loss
Rangeability
Precision
Conductive fluid
Viscous fluid
Type of Sensor
↗↗↗
+
MDDP – Megascale 3D Printing
Group 2
For this project the accelerometer chosen is the LIS302DL made by ST (ST LIS302DL
Accelerometer Datasheet). The accelerometer will be attached via serial port to a microprocessor that
will be part of the nozzle's main circuit board.
8.2.1
Current Sensor
In order to ensure safe running of the printer, enough power needs to be given to each motors.
Simple current meters can be used to check that. A current meter will be attached to each motor. The
sensor chosen is the DHR 300 C420 from LEM.
8.2.2
Sensor Selection
Table 22 - Selected Sensors and Prices
Sensor type
Sensor name
Company
Price
Motion
Kinect
Microsoft
£90
Position
E40H8-100-3-N-24
AUTONICS
£154.37
Temperature
DS18B20 1
Maxim IC
$ 5,99
Global Water
$3,311
FM500
Flow
Flow Meter
Current
DHR 300 C420
Accelerometer
8.3
Ultrasonic
LIS302DL
LEM
£186.92
ST
£3.06
Electronic Systems Diagram
8.3.1
Motor Control
Each motor will get their instructions from the respective ATmega328 Micro Controller Unit
(MCU) of which the motors are connected via digital in and out. These selected motors are
servomotors and can correct their position by themselves, position sensors are also used to calibrate
the printer and check for any other errors. The motor's positions will have to be recorded at all times
so that calibration is not needed after a power cut for example. If anything goes wrong (overheating,
power cut, security problem etc.) then all the motors will have to be stopped at the same time. This is
why the connection between the motors and the MCU is a two way connection.
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8.3.2
Group 2
Sensors
The sensors check if the printing process is going smoothly. If any problem occurs, it is reported
to the master MCU, which will decide on the relevant action to take. Stopping the printing process
isn’t always going to be needed.
8.3.3
Nozzle
The systems diagram for the nozzle also contains an ATmega32 micro control unit which
controls three motors and a relay circuit for the electromagnet. The motors are for controlling the
valve, switching the nozzle size and lifting the nozzle plate and will be digitally controlled by the
MCU. The electromagnet will require a relay circuit in order to turn the electromagnet on and off.
This circuit will be digitally controlled by the MCU also.
8.3.4
Robotic Arm
The robotic arm controller will be purchased separately along with the arm itself. This is b cause
the control of the robotic arm will already have been implemented and to implement it ourselves
would be a huge task.
8.3.5
Motion Sensing
Motion sensing is performed using computer vision. The video from the Kinect is analysed on
the laptop and different shapes are found using background removal techniques explained in the
software section of this report. The image with the extracted features are then compared to images in
a database. If the shapes are highly similar, it means that a person is present on the printing site and is
at risk. Therefore, the printing process is stopped until the person is safe.
8.3.6
Master MCU
The master MCU is the head of the printing process. It controls and records everything from the
sensors to the house design. If the printing process has to be stopped, it has to make sure that all the
data is saved to start the printing where it was left. In addition to this when the printing process
starts again, some potential measures might have to be taken. For example, if the concrete has
settled, then the printing cannot start right away as the next layer won’t fix as well. If there is an
error, the slave MCUs can send an interrupt to the master MCU in order for it to stop the printing
process.
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Figure 58 - Electronic Systems Diagram
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8.4
Group 2
Power
To evaluate the amount of power needed to print a house, the power requirement for each element
needs to be known. This estimation however is difficult and so the largest estimation will be taken to
allow for an error margin.
If all the motors are running at full torque at the same time, a total of 63.01 kW is needed to power
printer. This is a maximum and will never be reached as all the motors will never be working at full
torque at the same time. Calculating the value for full power however will give an error margin that
will allow for any other devices to be used such as lighting.
The Department of Energy and Climate Change gives the prices for different form of energy and
use. The price estimation is based on this information and, for industrial use of electricity, the average
price is 7.30p/kWh (Department of Energy and Climate Change, 2012).
The group has estimated that it will take 8 days to build a house without interruption. Based on
these figures, 12096kwh is required to build one house. Then, the power price for a house is £883.
In case of a prolonged power cut, a second generator might be needed so that the printing is not
delayed for too long. The purchase price of a generator capable of powering the whole printer is
around £8,000 to £10,000 (FW Power, 2012).
It is a better solution to hire the generator. This will spare capital immobilisation and maintenance
fees. The generator would be hired in case the power will be out for a long time or not enough power
can be delivered otherwise. Typically, to hire a generator for 60 hours, it is £174.90 and for unlimited
time around £314 (Stuart Power, 2012).
9 SOFTWARE
The software behind this project and the specifications for it are important for several reasons. One
of the most important being that it will be controlling very heavy machinery which needs monitoring
for safety and accuracy reasons. The printer proposed in this project is similar in some senses to many
other printers in the industry today only on a very large scale. This suggests that existing software
could be adapted to meet our needs. The rest of the decisions behind the software and a high level
design for the project is outlined in this section. Before this however, an explanation behind the STL
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file format and GCode are first included as these are both important to the understanding of the
software section of this project.
9.1
STL File
The STL file format was created by 3D systems for use with their Stereolithography CAD
software and is now the default format of choice for many other, if not all rapid prototyping
techniques (Chua, Leong, & Lim, 2010) . An STL file can be produced as an output from a model
using most CAD programs.
The file contains an unordered list of triangular facets that represent the outside surface of the
model using Cartesian coordinates in three dimensions (IANCU, IANCU, & STĂNCIOIU, 2010).
9.1.1
STL FORMAT
STL comes in two formats, either ASCII or Binary, with the ASCII format being very large in size.
Both formats list a number of triangles via their vertexes that correspond to the desired object, with
the ASCII format being readable by humans. The software implemented for the printer must be able
to cope with both formats of STL in order to obtain maximum compatibility. Below is an example of
a Binary STL file:
UINT8[80]
- Header
UINT32
- Number of triangles
for each triangle
REAL32[3]
- Normal vector
REAL32[3]
- Vertex 1
REAL32[3]
- Vertex 2
REAL32[3]
- Vertex 3
UINT16
- Attribute byte count
end
(IANCU, IANCU, & STĂNCIOIU, 2010)
9.1.2
Colour in Binary STL
There at least two ways of adding colour information to a Binary STL file. The first used in the
CAD programs VisCAM or SolidView uses two bytes at the end of each triangle description called
'attribute byte count'. A 15 bit RGB colour is stored and therefore each triangle has a colour. Another
method used by the STL editing software Magics, uses the 80 byte header at the start of the binary file
to describe the colour of the whole object. (IANCU, IANCU, & STĂNCIOIU, 2010). The colour and
the finish of the building will be discussed in detail later in this report, but it should be noted that
colour information can be stored in the STL file itself.
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9.2
Group 2
G-Code
GCode is a programming language that tells a machine what to do in terms of co-ordinates and
positioning and other instructions relating to the machine. The printer's firmware must be able to
understand specific GCode instructions in order for it to be able to print. An example of some GCode
taken from an already available commercial 3D printer called RepRap is shown below
(G-code, 2012):
N3 T0*57
N4 G92 E0*67
N5 G28*22
N6 G1 F1500.0*82
N7 G1 X2.0 Y2.0 F3000.0*85
N8 G1 X3.0 Y3.0*33
The table below shows an explanation of each of the GCodes the RepRap printer uses in the code
above:
Letter
Meaning
Gnn
Standard GCode command, eg: move to a point.
Tnn
Select tool nnn.
Ennn
Length of extrudate in mm.
Fnnn
Feedrate in mm per minute. (Speed of print head).
Xnnn
X coordinate (usually to move to).
Ynnn
Y coordinate (usually to move to).
Znnn
Z coordinate (usually to move to).
Nnnn
Line number. Used to repeat transmissions in case of comms error.
These GCode instructions are fairly standard and will be used for the operation of the printer.
Other instructions however will need to be added in order to be able to operate a large scale printer,
printing concrete. At current the length of extrudate is in terms of millimetres which will most likely
be changed to meters to fit the scale of a building. The same can be said for the feed rate which will
be changed to meters per minute as opposed to millimetres.
The tool selection feature Fnn will be used when changing between control of the print head and
robotic arm.
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9.2.1
Group 2
High Level Block Diagram
The software behind conventional 3D printing has four parts starting from CAD and ending in the
finished model. These steps are shown in the diagram below:
Figure 59 - High Level Software Block Diagram
1. CAD - A model is made in CAD and outputted as an STL file.
2. G-Code Convertor - Takes an STL file and outputs GCode, instructions the printer
understands.
3. Printer Front End Software - Controls the printer itself and displays current actions,
position etc.
4. Printer Firmware - Installed on the printer's microprocessor, is responsible for handling the
G-Code instructions from the PC.
Numbers 1-3 will be run on a laptop or PC whereas number 4 will be the software running the
printer itself. For simplicity the GCode convertor will be integrated with the printer front end
software, they will however be described as separate entities.
9.3
CAD
The CAD software will be the choice of the model designer and therefore will not need to be
designed as part of this project. Added to this the majority of CAD programs are able to export their
files as an STL file, which would be compatible with the rest of the printer software.
9.4
G-Code Converter
The GCode convertor will need to convert the STL file received from the CAD software and
convert it into GCode which the printer will understand. The majority of the functionality will be
hidden from view as there is minimum input needed from a user. The program will identify any areas
of which it believes will not be suitable for printing using algorithms to calculate the likely success of
a print. These algorithms will look for any potential gaps in the surfaces and will feature some kind of
stress checking analysis in order to report whether the structure will stand and can be built. If the
program finds an error in the model it will provide several warnings to the user before making sure
they would like to commence with printing.
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There will be predefined GCode list of which the converter will have to understand how to
assemble each layer and convert this movement into the relevant GCode instructions.
9.5
Printer Front End Software
The printer front end software will relay the G Code instructions to the printer in order for it to
print a structure. It will also be the main component of the software section as it will contain the user
interface in order for the user to interact with the printer.
An example of what the user interface will look like is seen below in Figure 60:
Figure 60 - Example of the printer software user interface.
The user interface will have an animation to show the progress of the current print job and it will
also list the G Code that is being run by the printer as seen in the top of Figure 60 on the left hand
side. There will also be indications of the state of the flow of concrete and temperatures of the nozzle
in order for a user to be able to stop the machine if there is an error.
To load an STL file ready for printing the user clicks on browse to search for an appropriate file as
shown below and once the user selects an appropriate STL file the software will then convert the file
into relevant GCode for printing.
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If there are any errors the user will be informed and a detailed report of what needs to be changed
within the model will be given. The user can still continue if they wish to do so, the software however
will give prior warning before printing that there is an error within the file and a successful print may
not be achieved.
9.6
Printer Firmware
The firmware for the printer is a collection of hardware and software that runs the printer's functions.
The hardware will contain an array of processors that will handle both sensors and the printer
movement itself. The hardware for the printer firmware is covered in detail in the electronics section
of this report.
The printer firmware will contain software that will not only control the movement of the printer but
it will also handle all of the sensory inputs in order to be able to control a safe and accurate print job.
9.6.1
Movement
The printer firmware will handle the G Code received from the front end software on the computer
and will then translate that into printer movements and instructions. As previously discussed there
will be 6 motors that need controlling in real time. These motors are controlled by using a Pulse
Width Modulation Signal (PWM) of which the software will need to control in order to maintain a
correct speed when controlling the motors.
The movement of the printer will be handled by the AtMega328 micro controller unit. The code
for the movement of the printer should be written in C++ to ensure that it is not only efficient code
but also has the benefit of abstraction. The processor selected can handle up to 6 PWM inputs, of
which an instruction from the processor for a motor to move will have to be converted into a PWM
signal.
There are three basic movements that the printer will need to handle (CNC Basics):
1. Rapid Motion - Used to move the printer as fast as possible when in-between printing, and
for certain jobs for example: the robotic arm picking up a piece of rebar.
2. Straight Line Motion (Linear Interpolation) - Used for linear movements, will be used
heavily for mass produced buildings.
3. Circular Motion (Circular Interpolation) - Used for circular shapes for example a rounded
wall or pillar.
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9.6.1.1
Group 2
Rapid Motion
Rapid motion will be used in many situations for example: parking the printer, using the robotic
arm to transport rebar and in-between printing. This form of motion is needed in order to reduce the
time in which the printer is not productive. Not all axes will have the same speed however and one
axis might reach its destination quicker than the other two. The printer therefore will need to avoid
any possible obstacles in its way. An algorithm will need to be produced in order for the printer to
know what it has already printed so that when it is under rapid motion it knows of all the possible
obstacles. The G Code used for rapid motion is G00 of which an end point is given alongside this.
9.6.1.2
Linear Interpolation
The software for the printer will need to interpolate between points in order to move the print head
and robotic arm using all three axes. This is due to the GCode sent to the printer only describing
which point the printer needs to go to. The printer firmware will need to interpolate between points
using a suitable algorithm.
Interpolation is defined as a method of creating new data points within a range of known points.
When using this within the printer to synchronise the movement of all axis a flow rate must also be
known. The firmware will use linear interpolation in order to achieve a straight line by calculating
small axis movements in order to keep the printer travelling along the straight line with an appropriate
flow rate of concrete. The number of points calculated will depend on the resolution of the printer
itself and how accurate it needs to be.
Given two points and a resolution (number of steps in between), the points that create a straight
line can be calculated using the following equation:
𝑌 =
(𝑋 − 𝑋 )(𝑌 − 𝑌 )
+𝑌
(𝑋 − 𝑋 )
Where the first point is (X1, Y1) the second point is (X3, Y3) and X2 is calculated using the
number of steps in between the two points (the point to perform the interpolation) . Y2 is then the
missing value that is calculated to get the new point. Taking the following values, Y2 can be
calculated:
X1
Y1
X2
Y2
X3
Y3
1
1
2
?
3
3
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𝑌 =
(𝑋 − 𝑋 )(𝑌 − 𝑌 )
+𝑌
(𝑋 − 𝑋 )
Group 2
𝑌 =
(2 − 1)(3 − 1)
+1
(3 − 1)
𝑌 = 2
Contained in Appendix 2 is an implementation of linear interpolation written in C++ that takes two
points and a resolution and will calculate the relevant points in-between. Setting point 1 as (1, 1) and
point 2 as (25, 25) with a resolution of 10 gives the following values show in Table 23:
Table 23- Calculated Values for Linear Interpolation Example
Figure 61 - Example of Linear Interpolation
To achieve linear interpolation in 3D (trilinear interpolation), 2D linear interpolation needs to be
calculated three times, one for each axis.
The G Code associated with straight line motion is G01. As previously discussed the G01
command will contain the point for each axis that the printer needs to end up at.
9.6.1.3
Circular Interpolation
While the printer will be mainly printer straight walls based on a mass produced selling point, the
need for circular walls is also evident and needs to be implemented. This means that a circular
interpolation algorithm will need to be implemented in the printer firmware in order for it to be able
to print circular shapes.
Circular interpolation requires an endpoint and feed rate as mentioned in linear interpolation,
however it also needs a radius and a direction of movement. Given two data points and a radius the
printer firmware must be able to calculate a number of suitable points for each axis in order to create
a circle.
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An example of circular interpolation can be seen below in Figure 62:
Figure 62 - Example of Circular Interpolation
The graph shows and example of moving from point (2,7) to the point (7,1) through a circular
motion with a radius of 5. The circular line in this example is made up of many small straight lines of
which circular interpolation is needed to calculate the numerous points for each axis that make up the
shape. The G Code associated with circular motion are G02 for clockwise motion and G03 for
counter clockwise motion.
9.6.2
Sensor Software
The printer will contain an array of sensors in order to make the structure accurate and print area
safe as it will be a very large and potentially dangerous machine if there was an error. The included
sensors are covered in the sensor section of this report in section 8.2. The following sensors will be
used:

Accelerometer

Temperature

Current

Flow

Positional
The accelerometer will need to be monitored by the software at all times in order to detect whether
there is a problem with the cross beam falling at an abnormal acceleration. If it detects an error an
interrupt signal needs to be sent in order for the main processor to react and use the safety latches
contained in the respective axis's rack and pinion system in order to catch the falling bar.
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The temperature sensor selected uses a digital output and therefore monitoring the temperature
will be simple, and detecting an abnormally low or high temperature should result in the printer being
automatically shut down by the software.
The current sensors connected to each motor will also need to be monitored constantly to ensure
the safe use of the printer. Hitting a threshold will immediately stop the printing process.
The processor controlling the printer will need to be connected to the pump of the printer in order
to be able to affect the flow rate of the pump if the flow sensor detects an error.
The final sensor is the positional sensors for the entire printer. These sensors are needed as
although servo motors provide position sensing, they will need to be calibrated at the start of each
print in order for the printer to provide an accurate print. In order to do this the software must have a
calibration function in which the external positional sensors will locate each axis, the nozzle and
robotic arm and then use these positions to adjust the readings from the servo motors in order for a
more accurate reading of position. After the calibration the servo motors can be relied on for position
sensing and control.
9.6.3
Machine Vision
Machine vision is going to be an important part of the operation of the printer, but it is a highly
complex task with various considerations to be taken into account in order to create an effective
automated system. There are two main aspects – seeing and perceiving (Davies, 2002) – seeing in this
case is achieved by various pieces of hardware and the images they take are passed on to the
perception stage of machine vision, which is achieved by software, where the interpretation of these
images occurs. The hardware used will usually fall down to a light source, a camera (and lens) and a
vision processor. Various light sources could be used for the application and it is important to choose
correctly based on the conditions of work. These could fall to using ambient lighting, direct-lighting,
back-lighting or strobe lighting as well as many others. There are also many considerations to take in
to account with the camera and lens – the frame rate, field and depth of view, stability and many more
(Hall, Gaily, Cao, & Guda, 2000). Since the use of machine vision for the 3D printer is to identify,
correctly orientate parts, and then place the parts appropriately, hardware to make these tasks easier
would be chosen. It should be noted that the machine vision system cannot make its own decisions; it
can merely compare against pre-set images and relationships and adjust its behaviour accordingly.
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Figure 63 - Different Types of Lighting Conditions for Machine Vision
Particularly since the printer will be working at night, ambient light cannot be relied upon to give
adequate illumination. This must be considered in detail as lighting is potentially the most important
part in creating an effective machine vision system as demonstrated by Batchelor and Whelan saying
“If it matters that we use the Sobel edge detector rather than the Roberts operator, then there is
something wrong, probably the lighting” (Dickerson, 2000). Figure 63 shows a variety of lighting
techniques for use in machine vision applications. The objective of lighting is often to create a high
contrast image, often with a fast exposure time. These high contrast images can highlight physical
edges in the field of vision or shadows depending on the desired output of the machine vision.
Lighting can be split into two broad categories: backlit objects, or otherwise. Backlighting means that
the camera will capture the outline of the component rather than the component itself. This is good
because it doesn’t need to take the optical properties of the component into account, but it
unfortunately cannot be used for the majority of tasks that will involve the robotic arm in the printing
activity. This is because these tasks revolve around placing components on a concrete wall which
itself can be back lit but will obscure details such as rebar position and only show the outline of the
wall.
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Non-backlit lighting has various forms, such as the frontal directional and oblique illumination
shown in Figure 63 alongside some types of backlighting. These rely on the reflection properties of
the material to be effective, particularly as a lot of lighting techniques rely on light approaching the
object from specific angles to achieve the desired result.
The type of light itself should also be considered. Strobe lights are highly practical in machine
vision applications as it provides lighting for a sufficient amount of time if the strobing is in sync with
the camera while providing greater light intensity for less power than a conventional light as it is only
on for a fraction of the time. Light Emitting Diodes (LEDs) are often used in this application also, as
they have a very long life if they aren’t overheated and can be turned on and off very quickly,
however they must be setup correctly and in groups to achieve uniform (un-patterned) illumination.
Since the printer will often be working in an enclosed area for weather protection, artificial
lighting will need to be relied on for most of the time. Due to the lack of personnel who will be
viewing the printing area it may be beneficial to use a strobe light in conjunction with machine vision.
This will provide intense light for the cameras but with lower power consumption and with no human
interaction needed, the lack of visibility it gives will not impede the printing process. Additional
lighting will be needed when human intervention is needed in the printing process, such as the
construction of roofing, which would be in the form of normal fluorescent lighting. This is chosen
instead of incandescent as it provides the same light intensity with a lower power requirement and
longer lifetime (US Department of Energy, 2012).
Figure 64 Steps for Visual Information Processing (Cho, 2006)
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The software stage of machine vision operation falls loosely into four ordered stages - preprocessing, intermediate processing, feature extraction, and scene understanding (Cho, 2006). The
point of all these steps is to extract and analyse high level information such as points, edges, surfaces
and regions from an image. This means correcting all the faults with the original image which may
hinder this such as noise, blurs, low contrast and geometric distortion caused by the lens. Different
information can be obtained by using different methods, and so choosing which features are most
appropriate for the application will narrow down which processing methods should be utilised.
Once the image has been analysed and features have been recognised and compared with
information stored by the software it must then be acted upon. In the case of the printer this will mean
one of several possible tasks. First of these tasks is finding the exact location of the rebar or other part
to be picked up, this is necessary as its location will not be exact enough to give the arm a coordinate.
Second is the comparison of the position of the ends of the parts with reference points on the building
– for example the pieces of rebar must match up with each other exactly or the arm will not be able to
install them.
The necessities of the machine vision in the printing process are to identify parts, place them in the
correct place with the correct orientation, and to locate the joins between pieces of rebar and weld
them together. To achieve this, a high contrast image showing all the distinct edges of the parts would
be desired, this is both for shape identification purposes and also to detect the join between rebar so
the welding occurs in the correct location. It will also need some kind of depth recognition so it can
place the rebar correctly rather than dropping it from a height or trying to push it too far in to the
concrete. The weld position and relative heights of the rebar are a less important issue as some of this
height should be calculated by sensors dictating the robot’s absolute position. This means that
directional front illumination should suit all the described needs, the side lighting emphasises
shadows so that depth can be determined but it should also give a good enough outline of the shapes
given the simple design of all the components to be installed.
9.6.3.1
Motion Detection
As previously discussed motion detection is needed in order to provide a safety feature, in which
no one is allowed to enter the printing area once the printing has commenced. In order to achieve this
machine vision will be used as the printer will be moving throughout the process and so a
conventional motion detector would not be suitable.
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Differential Motion Analysis (DMA) will be used to detect any motion in the printing area. There
are two ways to use DMA of which the first works by subtracting a reference image from a test image
in order to extract objects in the test image (Lee D. , Zhan, Thomas, & Schoenberger, 2004). Figure
65 below shows the basic subtraction of a reference image on the left from a test image in the centre,
and the output on the right.
Figure 65 - Motion Detection Example (Reference Frame)
Using this first method it is much easier to pick out the object as long as the light conditions are
similar in both the reference image and the test image. This means that there needs to be a selection of
reference images in different light conditions and the software will need to auto calibrate in order to
know which reference image to use (Lee D. , Zhan, Thomas, & Schoenberger, 2004).
The second method uses two sequential frames and subtracts them in order to extract the moving
object from the image. This eliminates any potential problems with differing light conditions and
picture intensities. It does however provide a less clear object, which can make the rest of the process
of motion detection more difficult (Lee D. , Zhan, Thomas, & Schoenberger, 2004). Figure 66 below
shows this process:
Figure 66 - Motion Detection Example (No Reference Frame)
This second process will be used for object detection in the project as it would not be time
efficient to set up a camera to take pictures at various light levels throughout a day, as the buildings
must be constructed as quickly as possible. If the second method is used, there would be no time
delay added for this sensor between setting up the printer and printing.
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Once the background has been removed, the image is then binarized using a suitable threshold and
a median filter is then applied as well as morphology techniques in order to improve the motion
detection. A Canny Edge detector is used to extract the objects contours (Lee D.-J. , Zhan, Thomas, &
Schoenberger, 2004). This process can be seen in Figure 67 below with the left image being the
binarized image, the middle being the tidied image and the right image being the result of edge
detection:
Figure 67 - Motion Detection Canny Edge Detection Example
Once a basic shape has been discovered and the object has been extracted from the image, it needs
to be compared with a database of stored images to determine what the object is. If the object is found
to be a human the software will then need to react by sending an interrupt to the relevant processor to
stop the whole machine and save its state.
9.7
Fail Safe
Due to the printer’s large size the software running the machine will need to be able to react as
quickly as possible in the event of an error or a potential safety concern. In the previous section,
outlined are the sensors and the reasons for their inclusion. Aside from the obvious positional sensors,
the majority of the other sensors are used purely to ensure the safe operation of the printer. This
means that the software will need to cause an interrupt when an error has occurred in order for the
processor to abandon its current thread and run relevant code that deals with the error.
The software controlling the sensors will contain thresholds as it is not convenient to stop the
printer in all cases of a sensor reading an incorrect level. An example could be that the current
supplied to one of the motors is slightly higher than its adjacent motor, if the difference is below the
threshold than the control system would simply rectify the issue. If the difference in current is above
the threshold however this could become a potentially dangerous issue and the interrupt to the
relevant processor would be sent in order for the program to take action and stop the printer.
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9.8
Group 2
Pausing the Print
There are many situations in which the software must save its state in order to pause a print job for
example; when constructing the form work for the second floor, or the event of an error (as above).
This means that the software running the printer will have to save its current state in order to not only
cause any potential damage to the printed building but also to be able to continue from where the
printer had to stop.
9.9
Class Diagram
Contained in Figure 68 is an estimation for the class diagram, showing the various classes
involved in the printer software.
The following main classes have been implemented for use in the firmware software:

Printer Class - Contains variables and members used for printing. Dependent on the
majority of the other classes in order to be able to print.

Sensor Class - The various sensors for example accelerometer and temperature sensors
each have a class which inherits from the abstract sensor class.

Nozzle Class - Contains members and variables used in controlling nozzle specific items
such as valve control and the nozzle plate. Also "has a" valve and motor class.

Robotic Arm Class - Contains members and variables associated with controlling the
robotic arm. Many of these may have to be implemented from the company that produces
the robotic arm. Inherits the motor class.

Z and Y Axis Classes - Both contain members and variables that control the respective
axes. Also inherit a motor class with a "has a" relationship.
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Figure 68 - Class Diagram
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10 BUILDING FINISH
10.1 Insulation
Insulating material in construction is used to regulate the temperature inside the building. It is also
used to reduce the energy consummation generated by heating or air conditioning and to keep the
building at a relatively stable temperature. The temperature inside a building changes due heat flow
from conduction, convection and radiation. The aim of insolating a building is to reduce the heat flow
to a minimum (Oak Ridge National Laboratory, 2012).
The evaluation of insulation material is made from 4 different figures (Al-Homoud, 2005), (Jelle,
2011) :
1.
K-Value: The thermal conductivity measured in W/m-K. That is “the time rate of
steady state heat flow (W) through a unit area of 1m thick homogeneous material in
a direction perpendicular to isothermal planes, induced by a unit (1K) temperature
difference across the sample.”
2.
R-Value: The thermal resistance measured in m2 -K/W. It is the resistance the
material against heat flow.
3.
C-Value: The thermal conductance measured in W/m2-K. “It is similar to thermal
conductivity except it refers to a particular thickness of material” It doesn’t take into
account the inside and outside air films resistances.
4.
U-Value or the Overall Heat Transfer Coefficient measured in W/m2-K.
Mineral wool can be used to insulate a building. It can be glass wool or rock wool. Light wools are
used to insulate the walls and heavier wools for roofs or floors. The wool can be cut and perforated to
fit the building shape when being put in place. The conductivity of wool is around 30/40 mW/(mK).
Polystyrene can also be used as an insulation material. It can be seen in two forms:
1. Expanded Polystyrene (EPS): small spheres of polystyrene with an expansion agent. It is in
the shape of a board.
2. Extruded Polystyrene (XPS): the polystyrene is melted and mixed with an expansion gas. The
board is created by extruding the polystyrene through a nozzle, and with the effect of the
expansion gas, it expands. The final material can be cut to fit the building shape.
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In both cases, the conductivity is between 30 and 40 mW/(mK).
Spray foam is one of the most effective conventional ways to insulate a house. It is generally
Polyurethane foam that is used. The foam is disposed in the middle of the two concrete parts of the
wall and expands itself to fill the whole space. While Polyurethane foam is an effective method of
insulation, it can become harmful in the case of fire. When burned, polyurethane releases dangerous
gases: Hydrogen Cyanide (HCN) and isocyanates.
A current state of the art technology is Vacuum Insulation Pannels (VIP). They have a low thermal
conductivity of around 20 mW/(mK). In addition to its high price, several problems arise from using
VIPs however as because VIPs come in panels, they cannot be cut onsite to fit the shape of the
building. The thermal conductivity also increases a lot when the panel is degraded.
11 SUSTAINABILITY
11.1 Concrete
Concrete was chosen for the material in this project due to it already being proven in the
construction industry and the already available research in its use in 3D printing. The decision was
made as the material most closely answered the questions of can it be printed and is it a good material
in which to build a structure from?
Concrete houses provide many benefits in terms of sustainability for the building itself. The main
ones being (Benefits to Concrete Homes n.d.) :

Lower energy bills – Concrete homes require around 44% less energy to heat compared
with that of a wood frame house.

More comfort and less noise – An absence of cold drafts and lower noise pollution.

More resistive to pests – Concrete is less attractive to common house pests.

More resistive to organic material – Concrete has no organic material so it doesn’t support
the growth of mould, mildew and fungus etc.

Strength – A concrete home provides the highest energy efficiency and structural integrity
of any construction method (Concrete Homes n.d.).
In contrast to this however, the transportation and production of concrete is very energy intensive
and contributes to a large amount of the world’s greenhouse gas emissions. Concrete is also said to be
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only second to water in the world’s most used material (Jeffries, 2009).
If the process of printing structures was to increase in popularity, the concrete demand would
increase by a very large amount putting strain on the sustainability of the process behind production
and development. There are measures being taken to improve the process and to reduce the amount of
greenhouse gasses produced. Suitable investment should be made by the company behind the 3D
printer if concrete is to be continued to use in order to aid the research into the reduction of harmful
gasses into the atmosphere and to maintain a responsible business.
11.2 Roof
The roof protects the rest of the house from the weather such as rain and snow. It also has an
important part in the insulation. Roofs come in different shapes and forms. They can be flat, inclined
or curved. Different support structures can be used for example; trusses, beams and slabs as well as
different coverings (tiles, slates etc.) (Atcheson, 1995).
Special roofs can also be used to create a more sustainable building. An example being: the
installation of solar panels which make the house partly independent for electricity. Another example
is to use an eco-friendly material to cover the roof such as plantations, called a green roof.
A green roof improves the insulation in regards to the cold of the winter and the warmth of the
summer.
It acts like a natural air conditioning system, reducing the energy consumption of a
conventional house. A green roof is also beneficial in noise isolation and prolongs the life of the roof.
If used extensively in an area, green roofs can also reduce air pollution.
Heat insulation is made possible as the vegetation protects the roof from extreme variation of
temperatures. The gap can drop from 100°C difference to a 15°C difference. This implies a longer
lifespan for the roof as it is protected from important temperature variations (Gedge & Firth, 2004).
There are two kinds of green roofs available; extensive and intensive. The roof that could
potentially be used for the project is an extensive roof. The reason to build an extensive green roof is
that it is cheaper and easier to build than an intensive green roof. It comes from the fact that an
intensive green roof is thicker and so more expensive as it can support more types of plantation like
trees (Gedge & Firth, 2004).
11.3 Printer Structure
It was assumed that the part within the printer structure that was most likely to fail or exceed the
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expected lifetime in the shortest period of time would be the bearings. Therefore, part life analysis of
this part was carried out and the results can be seen in Section 6.5 of this report.
It can be seen from Table 16 that the bearings connected to the robotic arm will fail first within a
time of 4.81 years. This was based on the estimates of printer usage. As this length of time
approaches, it is advisable that these bearings are replaced or receive maintenance to ascertain their
condition.
The printer is therefore assumed to require general maintenance on an infrequent basis until four
years of use has occurred.
12 LEGAL CONSIDERATIONS
12.1 Building Regulations and Planning Permission
Any construction project comes with various legal considerations that must be accounted for; these
include contractual, environmental, labour, financial and political factors. However before any
building work can begin building regulations and planning permission as well as other legislation has
to be considered.
Building Regulations: These regulations define procedures that are necessary to ensure any
building work that is done is carried out safely. They also specify exactly what is expected of a
building in terms of technical performance and what qualifies as ‘building work’ in terms of heating,
plumbing etc. as anything that qualifies as building work can be subject to scrutiny according to the
building regulations. Another important aspect of these building regulations is the need for the
building to comply with health and safety standards as well as energy conversion guidelines
(GOV.UK).
Planning Permission: The majority of construction projects require planning permission before
they can go ahead; the only exceptions are for some sites that are on industrial sites or in warehouses.
Planning permission is granted by the local planning authority in question and it is a good idea to
informally discuss the plans with a local planning officer before jumping into formal application
process. Planning authorities will base their decision on size, layout, external appearance and site
location. They would also consider any necessary landscaping, infrastructure available (road access
and water supply), the purpose of the project as well as its effect on the local community. The
application process usually takes around 8 weeks and in the event of a refusal or the setting of new
stipulations it is possible to appeal the decision.
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12.2 Contracts
Before construction begins on a project it is important that the owner and contractor involved
include all the details within a written agreement. A more detailed the agreement will decrease the
chance of a dispute in the event that something goes wrong further down the line. It is also strongly
recommended that both parties seek legal advice when putting a contract together and ambiguous
language should be avoided within the agreement as in the event of a dispute the law will generally
rule against the party who wrote the disputed content. Disputes can be minimised by dealing with
trustworthy parties however sometimes a dispute will inevitably arise and in this instance it is
important to approach it with a calm and reasoned approach instead of looking to blame somebody
else. Poor handling of a dispute could lead to losing a long term or future customer (Ganaway, 2006).
13 FINANCE
This section of the report will contain an in-depth financial analysis comparing both the conventional
method for building houses and the proposed 3D printing method. In keeping with the selected
market of mass production, the idea is to produce many houses for as little money as possible. The
report will contain a five year forecast for profit and loss as well as a cash flow statement and detailed
salaries.
It was assumed that for both methods, the company would not only build the houses but also sell
them; therefore the entire income was based on the sale of those houses. This was in keeping with the
mass production market as it was thought that the building of bespoke houses would not generate a
large enough income. Due to the fact that the printer can only print the shell of the house, the printer
must complete this in as quick a time as possible in order for it to be comparable and possibly more
profitable than conventional methods.
There are many overlaps between the two methods; for example the finish (piping, wiring and
aesthetics etc.) of the house for both methods will be almost identical. The main start-up costs for
each business will largely be the same also. The main differences therefore will be in the employees
as the conventional method will use more building contractors. Both methods will produce the same
amount of houses in order to be able to compare the increased cost of the extra contractors that
conventional methods need; this value was estimated to be 45 houses, based on using a single printer.
13.1 Land Planning
In order to assist with finance, it was necessary to decide upon an area of land to purchase in order
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to begin mass production printing. The purchase of land would be a significant expense and therefore
a suitable location at a low cost must be decided upon.
An 81 acre lot in Brightlingsea, Essex was found at a cost of £400,000 (UK Land and Farms,
2012). In comparison to other areas of land found, this was the area that offered the best cost to size
ratio. Figure 69 below shows this area of land highlighted in red. When selecting this land, it was
assumed that the land was suitable for construction.
Figure 69 - Lot 2, Robinson Road, Brightlingsea, Essex.
A key aspect to the financial analysis of this project is the number of houses printed per year. This
could be used in conjunction with the land selected in order to estimate the number of houses that
could be printed within the 81 acres and furthermore, the length of time before additional land must
be purchased. In order to make this estimate, a map of the existing housing was downloaded (EDiNA,
2012) and the program Photoshop was used to plan the housing. Figure 70 below shows a master plan
for the first three years on the land chosen.
Figure 70 - Master Plan of the First Three Years for Lot 2, Robinson Road, Brightlingsea, Essex.
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This master plan shows the three years distinguished by different colours; year one is orange, year
two is purple and year three is grey. It was estimated that 45 housing frames would be printed per
year for the first two years and therefore 45 houses were modelled for each in Figure 70. Following
this, it was estimated that a second printer would be purchased in the third year and therefore 90
houses have been modelled for this year.
The layout in the master plan was produced by replicating existing housing configurations and
road sizes from the local town and placing them on site. It was completed this way to allow for the
new development to be as realistic as possible without the assistance of a planner or architect which
would reduce cost further.
The site is restricted by lakes that are already situated on the land; however this would only reduce
the number of houses by approximately 30. In addition, this would potentially add value to the houses
that would be built on this land.
A number of considerations were taken into account when master planning this land:

If houses are designed to be parallel to each another, the printer would operate with a reduced
down time in between printing each house. This would lead to a greater number of houses
printed yearly.

It is advisable not to plan for houses to face directly towards the south due to solar gain
(Baker Associates, Terence O'Rourke et al., 2007).

A basic design for a detached house is included within this report, however when creating the
master plan, semi-detached houses and terraced houses were included for a more realistic
estimation. It can be assumed that the same housing plan would not be used for every house.
Comparing Figure 69 and Figure 70, it can be seen that after the third year of construction, the
purchased land would have been completely built on. Therefore, at the start of the fourth year,
additional land would be required.
A benefit of initially purchasing this land is that a larger lot is available next to the first (UK Land
and Farms, 2012). This would give many further benefits; for example, the two printers would not
require transportation which would reduce costs.
In addition to selecting the land, other costs involved with the purchase of land have also been
included in the financial forecast. These include:
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
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Planning Permission - A quote was given from Essex County Council of £17,325 for the
first year based upon the construction of 45 houses (Planning Portal, 2012).

Stamp Duty Land Tax - The thresholds were obtained from the government website and a
value of £12,000 was found (HM Revenue & Customs, 2012).

Land Registry Fee - A value of £270 was obtained from the official land registry website
(Land Registry, 2012).
After deciding upon the land, an average house price for the local town was found by looking at
similar three bedroom houses in Brightlingsea, Essex. The average price was then increased slightly
to accommodate for the designed house for this project being larger than average for a three bedroom
house. This value was decided to be £200,000.
13.2 3D Printer Method
A key difference between the printer and conventional methods that was taken in to account whilst
forecasting the finance, was the assumption that the printer would be in operation for 24 hours a day
as the design has incorporated the safe running of the printer overnight which is a major benefit over
conventional methods. It was assumed for simplicity that there was no additional pay for night shift
workers as the majority of the workers were on a salary anyway.
13.2.1 Profit and Loss Account
In year one it was assumed that one printer would be purchased and based on earlier calculations, the
printer would be able to print 45 houses in one year. In order to print this number of houses, an
employee list for the first year was required. This can be seen below in Table 24:
Table 24 – 3D Printer Employee List for Year 1, Including Yearly Salaries
Year One Salaries **
Position
Site Manager
Safety Inspector
Operating Engineer
Secutiry Guards
Office Engineer (Civil & Mechincal 2 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
CEO
Accountant
Plumber
Electrician
TOTAL
Location
On site
N/A
On site
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Salary
3
1
6
3
4
1
1
1
1
1
1
1
1
1
1
27
Total
£45,000
£25,000
£30,000
£15,000
£30,000
£45,000
£15,000
£22,000
£22,000
£28,000
26000
£60,000
£50,000
£27,000
£29,000
£135,000
£25,000
£180,000
£45,000
£120,000
£45,000
£15,000
£22,000
£22,000
£28,000
26000
£60,000
£50,000
£27,000
£29,000
£829,000
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All the salary estimates for Years 1 to 5 can be seen in Appendix 6.
Six operating Engineers were chosen to ensure that at least two would be on site at any time and to
enable the printer to run for 24 hours a day. This is the same for the site manager and security guards,
of which there should be at least one of each of these members of staff on site at one time. Similarly
to conventional methods security guards were chosen to ensure the safety of the perimeter and
potential criminal activity. A plumber and electrician were employed on a permanent basis as there
would be work for both of them all year round.
The rest of the staff employed were predominantly office based, in which the project manager and
office Engineers would be responsible for the running of the building project. The estate agent
employed would sell the houses printed, in order to create a business that not only builds the houses
but also sells them, for maximum profit. In addition, the architect is employed to design houses for
future projects.
In addition to the salaried employees for the printing method, contractors will also need to be
employed in order to complete the foundations and roof, and supply formwork for the second floor as
well as finishing the building. Table 25 below shows an estimate of the number of contractors needed:
Table 25 – 3D Printer Contractor List for Year 1, Including Daily Salary
Production Wages*
Position
Builder
Location
On site
Number
Salary (Daily)
Total
16 £
80.00
£467,200
It was estimated that it would take 4 builders one month to perform the additional requirements to
complete the house. This means therefore, that 16 builders are required in order to be able to complete
the 45 printed structures estimated for year one. It is assumed for simplicity that the contractors will
work for 365 days a year for both methods.
All of the salaries listed are based on an average salary for that specific role in the South East of
England and it is assumed that no extra pay will be given for unsociable hours.
In order to estimate the cost of materials required for this method, a measure of how much
concrete was needed for one house was obtained to be 107.8 m3 of which the calculation for this
value can be seen in Appendix 3. Taking a rough value of £100 per cubic meter gave a total cost of
concrete for one house to be £10,780. The value for material cost was then estimated to be £50,000 in
total for a single house to account for the cost of the roof, plumbing, electrics and foundations etc.
The estimate of this material cost is also used in the conventional method as they would be a similar
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value and it is more likely that the difference in labour costs would be the deciding factor as to which
method is preferable.
Overheads for the printing method contain usual costs when starting a business including;
purchase of laptops, mobile phone contracts, furnishings, office rent, etc. The values for these costs
were found mostly through research on the internet as well as local advertising.
Once year one had been completed the profit and loss accounts for a further four years were
estimated and these can be seen in Appendix 6.
It was decided on to invest in a new printer in years three and five, purchasing them with the
remaining cash from previous years. It was also taken into account that all the houses would not be
sold in one year and therefore it was estimated that half of the houses produced each year would be
sold. Table 26 below shows the number of houses built, sold and the remaining unsold houses per
year.
Table 26 – Houses Built, Sold and Unsold Per Year
Year
Number of Houses Built Number of Houses Sold Number of Houses Unsold
1
2
3
4
5
45
45
90
90
135
23
45
67
90
113
22
22
45
45
67
Depreciation was estimated at 10% per year and is based on the loss in value of the assets; this
includes the printer and land purchased.
13.2.1 Cash Flow Statement
A cash flow statement was then forecasted for five years in order to obtain a Net Present Value
(NPV) of the proposed business. The cash flow statement contains a loan of £1 Million which is
completely repaid in the first year; an interest amount of 10% however is incurred on the loan.
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The cash flow statement for the five years is shown below in Table 27:
Table 27 – 3D Printer Cash Flow Statement for 5 Years
Cash Flow Statment
Cash flows from operating activities
Year 1
Year 2
Year 3
Year 4
Year 5
Sales
Cash Sales
Sales on Credit
Total Sales
Direct Cost of Sales
Personnel in Cost of Sales
Total Cost of Sales
Gross Margin
Operating Expenses
Wages and Salaries
Depreciation
Other Operating Expenses
EBIT
Interest (a)
Taxes
Net Cash Flow Operations
Cash flows from investing activities
Purchase of equipment
Net cash flow investments
Cash flows from financing activities
Dividends paid
Loan
Loan Repayment
£
£
£
£
£
£
£
4,600,000.00
4,600,000.00
2,679,795.00
467,200.00
3,146,995.00
1,453,005.00
£
£
£
£
£
£
£
9,000,000.00
9,000,000.00
2,267,325.00
467,200.00
2,734,525.00
6,265,475.00
£
£
£
£
£
£
£
13,600,000.00
13,600,000.00
4,534,850.00
1,280,000.00
5,814,850.00
7,785,150.00
£ 18,000,000.00
£
£ 18,000,000.00
£ 6,796,920.00
£ 934,400.00
£ 7,731,320.00
£ 10,268,680.00
£ 22,800,000.00
£
£ 22,800,000.00
£ 6,750,200.00
£ 1,401,600.00
£ 8,151,800.00
£ 14,648,200.00
£
£
£
£
£
£
£
829,000.00
47,000.00
68,367.33
508,637.67
100,000.00
122,073.04
286,564.63
£
£
£
£
£
£
£
851,000.00
47,000.00
62,668.30
5,304,806.70
1,273,153.61
4,031,653.09
£
£
£
£
£
£
£
1,280,000.00
54,000.00
69,219.18
6,381,930.82
1,531,663.40
4,850,267.43
£
£
£
£
£
£
£
£ 1,884,000.00
£ 286,000.00
£
64,817.52
£ 12,413,382.48
£
£ 2,979,211.79
£ 9,434,170.68
£
£
70,000.00
70,000.00
£
£
£
£
70,000.00
70,000.00
£
£
£
£
£
1,000,000.00
1,000,000.00
£
£
£
403,165.31
-
£
£
£
485,026.74
-
£
£
£
Net increase in cash
Cash beggining of year
Cash end of year
£
£
£
216,564.63
216,564.63
£
£
£
3,628,487.78
216,564.63
3,845,052.41
£
£
£
4,295,240.68
3,628,487.78
7,923,728.46
Discount Rate
NPV
£
50%
5,080,431.89
-
1,302,000.00
279,000.00
69,765.93
8,617,914.07
2,068,299.38
6,549,614.69
654,961.47
-
£ 5,894,653.22
£ 4,295,240.68
£ 10,189,893.90
£ 1,760,000.00
£ 1,760,000.00
£
£
£
943,417.07
-
£ 6,730,753.61
£ 5,894,653.22
£ 12,625,406.84
Assume a 1 Million loan that is paid back in the first year with 10% interest rate
Due to the large profit acquired starting in year 2, shareholders received 10% of the Earnings
Before Income Tax (EBIT) shown as ‘dividends paid’ in the cash flow statement.
A discount rate of 40% was found for similar construction companies that had just started
business, however the rate was increased slightly to accommodate for a potentially high risk new
business due to the nature of the this project. The discount rate for the printing method therefore was
estimated at 50%.
Using this discount rate a value for the NPV of the company can then be calculated. The NPV
measures the value of money today versus the value of money in the future, taking into account
inflation and returns (Inventables, 2012). The higher the NPV value the better, with the larger NPV
value being the more investible option. The calculated NPV for the printed method was £5,080,432.
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13.3 Conventional Method
13.3.1 Profit and loss account
Much of the profit and loss account for conventional methods is the same as the printer method
however there are some major exceptions. The main difference between the two methods is that,
instead of purchasing a printer in order to print the basic structure of the house, more building
contractors are needed. However some salaried workers are not required in the conventional method,
as there is no need to employ Engineers to operate the printer. Table 28 below shows the employee
list in the first year for the conventional method. The further four year salary projections are available
in Appendix 6:
Table 28 – Conventional Methods Employee List for Year 1, Including Yearly Salaries
Year One Salaries **
Position
Site Manager
Safety Inspector
Secutiry Guards
Office Engineer (Civil & Mechincal 1 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
CEO
Accountant
Plumber
Electrician
TOTAL
Location
On site
N/A
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On site
On site
Number
3
1
3
2
1
1
1
1
1
1
1
1
1
1
19
Salary
£
£
£
£
£
£
£
£
£
£
£
£
£
£
45,000.00
25,000.00
15,000.00
30,000.00
45,000.00
15,000.00
22,000.00
22,000.00
28,000.00
26,000.00
60,000.00
50,000.00
27,000.00
29,000.00
Total
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
135,000.00
25,000.00
45,000.00
60,000.00
45,000.00
15,000.00
22,000.00
22,000.00
28,000.00
26,000.00
60,000.00
50,000.00
27,000.00
29,000.00
589,000.00
For the conventional method, more building contractors are needed and an estimate of the first year
contractors is shown in Table 29 below:
Table 29 – Conventional Methods Contractor List for Year 1, Including Daily Salary
Production Wages*
Position
Builder
Location
On site
Number
Salary (daily)
Total
48 £
80.00 £
1,401,600.00
This estimation is based on 4 builders being able to complete a house in 3 months, therefore 48 are
needed in order to complete the 45 houses produced in order to match the printed method and produce
a fair comparison. As before, all salaries and pay rates are based on an average for the respective
position in the South East of England.
Comparing the two methods in this way reduces errors in the estimation of values, as the difference
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between the methods is simply the amount of labour the printer can replace.
13.3.1 Cash Flow Statement
A cash flow statement was also made for the conventional method to allow an NPV to be calculated
and compared against the printed method. The cash flow statement can be seen in Table 30 below:
Table 30 - Conventional Method 5 Year Cash Flow Statement
Cash Flow Statment
Year 1
Cash flows from operating activities
Year 2
Year 3
Year 4
Year 5
Sales
Cash Sales
Sales on Credit
Total Sales
Direct Cost of Sales
Personnel in Cost of Sales
Total Cost of Sales
Gross Margin
Operating Expenses
Wages and Salaries
Depreciation
Other Operating Expenses
EBIT
Interest
Taxes
Net Cash Flow Operations
Cash flows from investing activities
Purchase of equipment
Net cash flow investments
Cash flows from financing activities
Dividends paid
Loans
Loan Repayment
£
£
£
£
£
£
£
4,600,000.00
4,600,000.00
2,319,595.00
1,401,600.00
3,721,195.00
878,805.00
£ 9,000,000.00
£
£ 9,000,000.00
£ 2,267,325.00
£ 1,401,600.00
£ 3,668,925.00
£ 5,331,075.00
£ 13,600,000.00
£
£ 13,600,000.00
£ 4,534,650.00
£ 2,803,200.00
£ 7,337,850.00
£ 6,262,150.00
£ 18,000,000.00
£
£ 18,000,000.00
£ 9,046,920.00
£ 2,803,200.00
£ 11,850,120.00
£ 6,149,880.00
£ 22,800,000.00
£
£ 22,800,000.00
£ 5,700,000.00
£ 4,204,800.00
£ 9,904,800.00
£ 12,895,200.00
£
£
£
-£
£
-£
-£
589,000.00
40,000.00
308,367.33
58,562.33
100,000.00
14,054.96
144,507.37
£ 582,000.00
£
40,000.00
£ 331,668.30
£ 4,377,406.70
£
20,000.00
£ 1,050,577.61
£ 3,306,829.09
£
868,000.00
£
40,000.00
£
481,219.18
£ 4,872,930.82
£
£ 1,169,503.40
£ 3,703,427.43
£
890,000.00
£
265,000.00
£
481,765.93
£ 4,513,114.07
£
£ 1,083,147.38
£ 3,429,966.69
£ 1,266,000.00
£
265,000.00
£
682,817.52
£ 10,681,382.48
£
£ 2,563,531.79
£ 8,117,850.68
£
£
£
£
£
£
£ 1,760,000.00
£ 1,760,000.00
£
£
-
-
£
£ 1,000,000.00
£
800,000.00
£
£
£
Net increase in cash
Cash beggining of year
Cash end of year
£
£
£
£ 2,776,146.18
£
55,492.63
£ 2,831,638.81
Discount Rate
NPV
40%
£ 4,505,487.90
55,492.63
55,492.63
330,682.91
200,000.00
£
£
£
370,342.74
-
£ 3,333,084.68
£ 2,776,146.18
£ 6,109,230.86
£
£
£
342,996.67
-
£ 3,086,970.02
£ 3,333,084.68
£ 6,420,054.70
£
£
£
811,785.07
-
£ 5,546,065.61
£ 3,086,970.02
£ 8,633,035.64
Assume £1000000 loan in first year and interest rate of 10%
Similarly to the printed method, a loan of £1 Million was taken out in the first year in order to start
the business. This could not be paid back in the first year and so only £800,000 was paid back,
meaning interest on the loans was incurred in Years 1 and 2 with Year 2 being the year in which the
loan was re paid fully.
In the case of the conventional method the discount rate was taken as the same as construction
companies who had just started business, and represents a figure that is lower than the printed method
as it is a more common business and so provides less risk. The discount rate for this method is
estimated at 40%. Using this discount rate an NPV value of $4,505,488 was calculated and will be
used to compare both methods in the comparison section of this finance report.
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13.4 Financial Comparison
In this section a comparison between the financial forecasts of each method will be carried out. The
first major comparison between methods is the EBIT, with Figure 71 below showing the EBIT for
both methods across the five year forecast:
Figure 71 – Comparison of EBIT for Printed and Conventional Methods
It is clear to see that based on the estimations made; the printed method shows a much greater
performance in terms of EBIT every year. The drop in Year 4 can be accounted for by the purchase of
extra land for a large sum. It should also be noted that for the conventional method, the EBIT in year
one is a negative number, whereas for the printed method the EBIT in Year 1 is positive. Comparing
EBIT therefore suggests that the printed method is a more sound investment option.
It was noted that if the graph were to be extrapolated, the conventional EBIT value could potentially
become larger than the printed EBIT. A trend line therefore was added and extrapolated to predict the
values for a further 5 years. This can be seen in Figure 72 below:
Figure 72 – Extrapolation of EBIT for Printed and Conventional Methods
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When predicating a further 5 years, the printed method has an increasingly higher EBIT than the
conventional method, providing more evidence that the printed method provides more financial gain
as a business opportunity.
The next value for comparing both of the method’s investibility is the NPV. The project with the
highest NPV will be the one that brings more value, with a positive NPV being an investible option.
Figure 73 below shows the comparison between NPVs:
Figure 73 –Comparison of NPV for Printed and Conventional Methods
The printed method therefore has a larger NPV than the conventional method with the values being
£5,080,432 and £4,505,488 respectively. While these NPVs are close and both positive, meaning both
are good investment choices, due to the printed method’s NPV being approximately 11% higher, the
printed method is again the method of choice.
14 RISK ASSESSMENT
When trying to design such a large machine it is important to consider the different risks that could
occur. This section of the report aims to highlight any potential risks and their severity.
14.1 HAZOP Analysis
A Hazard and Operability Analysis (HAZOP) is a procedure that is used throughout the process
industry to systematically address any potential fault that would cause a plant or process to either
functionally incorrectly or not at all. A HAZOP analysis assumes that any problems or discrepancies
in the running of the process are caused as the process deviates from its specified operating
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conditions. Any fluctuation in the operating conditions of the process can be accounted for by using
an agreed list of “guide words”. These words describe any change in conditions e.g. MORE, LESS or
NO flow in a pipe used to transport fresh concrete.
One of the main issues to consider when mixing and pumping HPC mixtures is that they are
known for displaying poor workability/pumpability due to low w/b ratios. Adding superplasticiser to
the mix design does help improve workability however the mixtures viscosity should still be major
concern. Every possible precaution should be taken to try and negate any problems that limited
workability presents. For instance in the mixer it is vital that the feed-rates of all the constituents are
accurate particularly the water flow-rate into the mixer, if the w/b ratio was allowed to increase it
would be a relatively easy issue to correct as the automated control scheme would reduce the water
flow-rate into the mixer thus correcting the problem. However if the w/b ratio was to drop below the
desired value there could be more serious consequences as ‘balling’ could begin to occur in the
mixture, which is a term used to describe the clumping together of solids in the mix that could
potentially lead to blockage. Balling is particularly common in mixes that incorporate silica fume,
which is further reason to ensure w/b ratios are strictly controlled.
The HAZOP study emphasised the importance of controlling the w/b ratio during the mixing
stage, which led to a slight change in the mixing control scheme. It was deemed necessary to
incorporate a moisture sensor on one of the mixing blades so that the water content of the fresh
concrete could be monitored and controlled. The sensor would play a key role in the automated
control scheme as if the water content was to drop, the feed-rate of all solid and liquid materials
would be checked to see what had caused the fluctuation in concrete composition. The feed-rates
would then be adjusted as necessary to correct the error and the w/b ratio would be returned to its
original value.
Another significant point that the HAZOP analysis emphasised is the importance of having spare
parts of all key pieces of equipment that are used in the process. Spare piston pumps and control
valves of identical specification should be available on-site so that in the event of a pump or valve
failure the process can be halted and the spare pump or valve can be installed quickly. In the event of
a piping rupture or leak the process would inevitably have to be stopped and the piping replaced. The
piping from the pump to the printer head is flexible reinforced rubber piping so replacing it will be
relatively straightforward (provided a cherry picker is available on-site) however the concrete in the
damaged piping will have to be disposed of.
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14.2 Failure Mode Effects Analysis
Failure Mode Effects Analysis (FMEA) is a vital task to perform before any manufacturing of a
product should begin. It is used to identify causes of failure of parts/ products and can rank failure
modes in order of importance. The failure modes with the highest overall ratings can subsequently be
analysed and the chance of failure can be reduced if not eliminated.
A full FMEA table for this project can be seen in Appendix 8. The ratings given to each failure
mode relate to the Occurrence (O), Severity (S) and Detection (D). These values range from best to
worst and are assigned values of 1 to 10 respectively. Full descriptions of each of these values can be
seen in Appendix 8. Subsequently, the Overall Rating (R) can be calculated by multiplying the three
previous ratings together.
After examining the FMEA sheets in Appendix 8, it can be seen that a failure mode with a high
overall rating is fatigue on the X-axis beam (X001). This failure mode was given a rating of 1 for
occurrence as fatigue happens over a long period of time. A severity rating of 9 was given as if fatigue
occurs, the beam will fracture and eventually break, potentially causing harm to an individual. A
detection rating of 8 was given as fatigue is very difficult to see until more visible cracks appear, at
which time fatigue would have already occurred. These values give an overall rating of 72.
Following this failure mode being identified, steps can be taken in order to reduce or eliminate the
effect of it. Section 6.4 of this report shows the fatigue analysis that took place subsequently to the
FMEA analysis. This analysis resulted in the cyclic loads that the printer experiences being below the
fatigue level and therefore fatigue should not occur unless there are pre-existing cracks. Furthermore,
this risk was reduced/eliminated.
14.3 Site Health and Safety Analysis
Risks Assessments are an obligation for any construction project for Health and Safety purposes.
The main purpose of carrying out a risk assessment is to identify any hazards or risks that may occur
during the project beforehand and have actions or control measures ready to deal eliminate or reduce
these risks. The type of risks and hazards that are identified in these types or risk assessments involve
activities that may affect labour, pedestrians or any general activity during the project.
A Risk Assessment has been prepared for this project and can be seen in Appendix 8. It is in form
of table and lists up every activity with possible risks or hazards involved with them. It then explains
the control measure and who is responsible for it and who is monitoring the activity. The risks are
rated with Risk Ratings (RR) that is calculated by multiplying the Severity Rating (S) and the
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Likelihood of Occurrence (L) that are rated with a number from 1 to 5. Similarly the control measures
are rated with Residual Risk (RR) that is again calculated similarly. The residual risk rating is
different measures the risk of a certain hazard after taking a control measure over it, hence it should
be equal or less to the risk rating. Figure 74 shows the ratings and if the hazards are acceptable or
unacceptable for the project.
Figure 74 - Severity Ratings for Risk Assessment
As can be observed in the site health and safety analysis tables in Appendix 8, the most
considerable activity with risk involved labour or pedestrians interfering with the printer while on use.
The risk rating of it has been reduced from 12 to 6 by simply ensuring that labour is well informed
about timings when they should and should not access the perimeter where the printing works is
taking place. Similarly signage and banks men should ensure that pedestrians are not accessing
unauthorised areas. Summarising all of the activities are in the safe acceptable situation however all
labour involved during the construction should be aware of all possible risks and site supervisors
should keep emphasizing them and monitoring these at all time.
15 PROJECT MANAGEMENT
Each member of the team was allocated tasks at the beginning of the project. Tasks related to their
area of studies were preferred but the group was keen on broadening their knowledge in other areas in
order to have a good overall understanding of the project. This was beneficial in terms of team work
and meant that everyone in the group had some input in the majority of the project. This ensured good
work cohesion, making the design consistent and also meant when possible, team members were able
to help each other. The previous Gantt chart showing an initial work schedule for the project can be
seen in Appendix 9.
This initial project plan was followed, however some of the tasks were delayed because of a lack
of information, or had to be reviewed because an improvement on the initial decision made was
necessary. An example of this being: in the case of the nozzle design, additional time was needed due
to the unexpected innovation and complexity behind this part. This is why task rearrangement was
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needed throughout the project. Due to the time constraint some tasks had to be cancelled completely,
such as the CAD for the printer and the Matlab simulations. In addition to this, the complexity of the
designed printer parts meant that when using the CAD software available, a large amount of memory
was required and it was found that University of Surrey’s computers were not able to process these
complex parts. Figure 75 shows how the project actually ran and a task list accompanying the chart is
contained in Appendix 9:
Figure 75 - Final Gantt Chart Depicting Work Carried Out
To make sure the project continued at a fast rate, separate deliverables were set by the group and
were updated on the Gantt chart. This was to ensure that everyone got all the information they needed
in the required time and that no large set backs were incurred.
In addition to using a Gantt chart for the purposes of project management, it was found that having
at least one meeting a week in addition to the meeting with supervisors, was necessary to ensure
maximum productivity. This was to make sure that everyone was up to date with the project’s current
state and to put any potential new ideas together. Communication outside of meetings was also
essential and was conducted via email and work was also shared over a common source cloud
infrastructure on the internet. A version control system was also used in order to keep track of the
latest report version.
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16 FUTURE DEVELOPMENT
This section will discuss any future developments that the group would have liked to implement
into the design of the printer if more time was available. This includes any additional research into
issues that could arise if the printer were to be constructed and potential improvements to the design
and implementation of selected methods.
16.1 Part Automatic Assembly
An initial idea was to have the Y-axis of the printer (vertical axis) on hydraulic rams that could
simply be transported and then lift the X-axis (cross beam) into place, preferably without the need for
a crane. This would greatly simplify the construction phase of the printer and potentially reduce
assembly costs. It would also allow for a quicker construction time and if the axes were telescopic,
transportation could also be made easier also.
Figure 76 below, taken from an animation from the company Contour Crafting, shows the idea of
the hydraulic telescopic axis mentioned above.
Figure 76 – Hydraulic Telescopic Axis (House Printing Animation, 2011)
16.2 Removal of Labour
The initial idea for the construction of the structure was to use a combination of sand and wax in
order to support the building of the second floor. This innovative idea however was not achievable
due to the enormous weight placed on the foundations and outer walls. Given additional time, the idea
of completely removing any contracted labour, aside from those monitoring the printer, should be
researched to try and find a viable solution to support materials without the need for manual labour.
This is in fitting with the mass production market design and the idea that the maximum profit can be
achieved by eliminating any manual labour. This would revolutionise the whole construction industry,
which has relied on manual labour for centuries.
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16.3 Alternative Material
As discussed in the sustainability section of this report, concrete provides an energy efficient and
quiet home. Therefore concrete houses have some factors that are advantageous to that of
conventional houses. The production and transportation of concrete however, is very energy intensive
and produces many greenhouse gasses.
Concrete was chosen as the material of choice due to its ability to be printed and its obvious use in
the construction industry. Other materials that are more efficiently produced however could be
researched more, with the possibility of even finding a material that could be used for construction
that has not been considered previously due to limitations in conventional building methods. One
material to consider would be recycled plastic, as the idea of using plastic in the construction industry
is beginning to be heavily researched by some companies. It would also be easy to potentially change
the material which this printer uses, as it would just be a case of replacing the pumps and tubing, and
adjusting the software settings slightly to accommodate for the new properties of the material.
17 CONCLUSION
The main question and aim of this Project was if a 3D printing could be scaled up to such a level
in order to print a structure. The simple answer to this is yes. As presented in the report the proposed
solution not only fulfils this aim but also improves various aspects of the construction field. The overall construction time and labour dependency is reduced and therefore the construction industry itself
could potentially become much safer and the overall costing and construction equipment or materials
is reduced too. The time it takes to build the main structure of the building is reduced by approximately a third.
If it were to be entered into the market, the 3D printer proposed in this report would have no competitors, therefore providing many engineering challenges to design an innovative and feasible
solution. The proposed printer has the potential to solve the different problems occurring in the construction field and answers today’s need for new accommodation. The technology used already exists
and is proven to work in different fields. This means that similar results to conventional construction
methods can be obtained and as calculated, this would be more profitable when undertaking mass
production projects.
Furthermore, if the printer designed was to be manufactured and deployed into a competitive market, there are also additional advantages that would set this printer above rivals.
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The first would be the unique nozzle disc designed. This disc can be rotated to enable printing using different nozzle diameters. Similarly to a multi-head drill, this nozzle disc can be replaced by
others of different dimensions. This would give this printer a competitive advantage as a flexibility is
achieved with regards to the size and shape of the extruding concrete, allowing for more complex and
innovative designs to be printed.
The second competitive advantage is the fact that there is no limit to dimensions in the y-axis. This
enables varied housing design; for example, the opportunity to build semi-detached and terraced
houses. In addition, the upper limits to the other axis could also be altered. The beams for the printer
structure are bolted and therefore they could be removed and replaced by longer beams; this is
providing that the stress analysis on the new parts proves that they will not fail under this application.
The only limitation imposed to the type of house to build is the inclination of the land. If it is too inclined, then it is impossible for the printer to work.
Moreover, the incorporation of the robotic arm into the 3d printer allows for a great deal of flexibility in what can be achieved by the printer. Particularly with machine vision, it can perform tasks
such as part identification and locating which would normally require human intervention into the
printing process. This greatly increases the amount of automation possible. It is thought that if the
need for formwork were to be eliminated, the robotic arm would provide an even greater benefit.
Although a lot of the conventional methods of construction with concrete have been eliminated,
some limitations to the solution proposed still exist. The main limitation applies when constructing
floor slabs above ground level, as temporary formwork still needs to be erected in order for printing
of concrete to be carried forward. Additionally when constructing houses, the roof cannot be printed
unless they are flat and again supported with temporary formwork. It can therefore be concluded that
the biggest limitation of the solution proposed is the fact that it can only print over a flat surfaces ideally horizontally straight or with very little inclination.
As mentioned in the beginning the focus of the structure to be printed was to incorporate the idea
of mass production rather than printing more bespoke complicated buildings or statues. From the results obtained from the business plan comparing the 3D printer proposed solution to conventional
construction methods, it was found that the printing method has a higher net present value over the
conventional method, making it a better investment option.
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19 APPENDIX 1 – PART SPECIFICATION
All measurements of length are given in mm unless specified.
19.1 X Axis
19.1.1 X001 X Axis Beam
Note: Length L = 11m
19.1.2 X002 V Slide with Gearing Teeth
Part
Number
SS/PHSS
33
A
B
C
D
E
F
G
H
J
K
L
57.2
33
58
58
120
26
20
14
21.1
30
10800 12.5
160
M
N
P
Weight
(kg/m)
16
4
12.3
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19.1.3 X003 V Slide without Gearing Teeth
Refer to Appendix 1.1.2.
19.1.4 X004 Carriage Plate
Part
A
Number
AURD1283
580
3W5S
B
C
D
E
F
30
436
440
520 310
G
H
J
K
L
M
28
58
50
14
680
M12x
270.5 186.5 290
20
161
N
O
P
R
S
Weight
(kg)
140
100
48.2
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19.1.5 X005 Robotic Arm Motor
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19.1.6 X006 Nozzle Motor
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19.1.7 X006 Drive Flange & Pinion
Part
Number
Rack
No. of
A
Module Teeth
HDF 50S
5.0S
24
B
C
D
E
F
G
H
J
K
L
M
220 130 130 120 92
13
12
8
100 M12 24
8
M1
M2
N
O
P
Q
R
S
T
U
V
W
X
X1
Y
Z
Weight
(kg)
11
17
5
25
19
M8
120
40
145
30
10
60
150
142
8
3
8.6
19.1.8 X007 Buffer
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Part
A
B
B1 C
Number
BU33W 294 226 110 40
Group 2
D
E
F
F1 G
82
98
57 40 4
H
J
Weight
(kg)
1.03
K
L
244 20
10
270
M
N
P
R
ΦS
ΦU
8
-
-
-
14
19.1.9 X008 Bearings
Part Number ΦB C
D
ΦE F
G
H
BHJR128CNS17 96
28
25
50
M24 54 56 17 -
40
3
J
K
19.2 Y Axis
19.2.1 Y001 Flat Track with Teeth
Note length L = 2m.
165
L
Weight
(kg)
3
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19.2.2 Y002 Flat Track without Teeth
Note length L = 2m.
19.2.3 Y003 Carriage Plate
Refer to Appendix 18.1.4.
19.2.4 Y004 Motor
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19.2.5 Y005 Bearing Block (Right Side)
Refer to Appendix 18.2.6.
19.2.6 Y006 Bearing Block (Left Side)
19.2.7 Y007 Drive Flange with Pinion
Refer to Appendix 18.1.7.
19.2.8 Y008 Mounting Plate
19.3 Z Axis
19.3.1 Z001 Y Axis Bar
Refer to Appendix 18.1.1.
Note length L = 8m.
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19.3.2 Z002 V Slide with Gearing Teeth
Refer to Appendix 18.1.2.
Note length L = 7.8m.
19.3.3 Z003 V Slide without Gearing Teeth
Refer to Appendix 18.1.3.
Note length L = 7.8m.
19.3.4 Z004 Carriage Plate
Refer to Appendix 18.1.4.
19.3.5 Z005 Motor
Refer to Appendix 18.2.4
19.3.6 Z006 Drive Flange with Pinion
Refer to Appendix 18.1.7.
19.3.7 Z007 Buffer
Refer to Appendix 18.1.8.
19.3.8 Z007 Bearings
Refer to Appendix 18.1.9.
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20 APPENDIX 2 – C++ CODE LINEAR INTERPOLATION
#include <iostream>
#include <vector>
using namespace std;
void Interpolate(double point1[], double point2[], int resolution){
int size = ((resolution*2)+4);
double points[size-1];
points[0] = point1[0];
points[1] = point1[1];
float step = (point2[0] - point1[0] ) / (resolution+1);
float pointX = point1[0];
float pointY = 0.0;
for(int i = 2; i<=resolution*2; i+=2){
pointX = pointX + step;
pointY = (((pointX - point1[0])*(point2[1] - point1[1])/(point2[0] - point1[0]))+ point1[1]);
points[i] = pointX;
points[i+1] = pointY;
}
points[size-2] = point2[0];
points[size-1] = point2[1];
for(int i = 0; i<=size-1; i+=2){
cout<< points[i] <<" "<< points[i+1]<<endl;
}
}
int main() {
double first[] = {1.0,1.0};
double second [] = {25.0,25.0};
int resolution = 10;
double points[(resolution*2)+4];
Interpolate(first, second, resolution);
return 0;
}
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21 APPENDIX 3 – ADDITIONAL CALCULATIONS
21.1 Estimation of Concrete Required
21.1.1 Exterior Walls
Wall height per floor = 2400 mm
Fast Setting Concrete Width = 30 mm + 30 mm + 30 mm = 90 mm
Slow Setting Concrete Width = 80 mm
Fast Setting Concrete Area = [90 mm x 9420 mm x 2] + [90 mm x 9000 mm x 2]
= 3315600 mm2
Fast Setting Concrete Volume = [(Fast Setting Concrete Area x Wall Height) x 2]
= [(3315600 mm2 x 2400 mm) x 2]
= 1.591488 x 1010 mm3
Slow Setting Concrete Area = [80 mm x 9420 mm x 2] + [80 mm x 9000 mm x 2]
= 2947200 mm2
Slow Setting Concrete Volume = [(Fast Setting Concrete Area x Wall Height) x 2]
= [(2947200 mm2 x 2400 mm) x 2]
= 1.414656 x 1010 mm3
Area of Window = 914.4 mm x 170 mm = 155448 mm2
Volume of Window = 914.4mm x 155448mm =142141651.2 mm3
Total Volume of Windows = Volume of Window x Number of Windows
Total Volume of Windows = 142141651.2 mm3 x 13 = 1847841466 mm3
Area of Door = 1016 mm x 170 mm = 172720mm2
Volume of Door = 1828.8 mm x 172720 = 315870336mm3
Total Volume of Doors = Volume of Door x Number of Doors
Total Volume of Doors = 315870336mm3 x 2 = 631740672mm3
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Slow Setting Concrete Volume = 1.414656 x 1010 mm3 – (8/17 x 631740672mm3) – (8/17 x
1847841466 mm3) = 1.297969782 x 1010 mm3
Fast Setting Concrete Volume = 1.591488 x 1010 mm3 – (9/17 x 631740672mm3) – (9/17 x
1847841466 mm3) = 1.460216004 x1010 mm3
21.1.2 Interior Walls
Wall height per floor = 2400 mm
(BOTTOM LEVEL)
Total Wall Length = 4000 mm + 1000 mm + 5000 mm + 5160 mm + 3840 mm = 19000 mm
Fast Setting Concrete Volume = 19000 mm x 60 mm x 2400 mm = 2736000000 mm3
Slow Setting Concrete Volume = 19000 mm x 20 mm x 2400 mm = 912000000 mm3
Number of Doors = 3
Volume of Door = 315870336mm3
Total Volume of Doors = Volume of Door x Number of Doors
Total Volume of Doors = 315870336mm3 x 3 = 947611008 mm3
Subtract Doors from volume:
Fast St. Concrete Volume = 2736000000 mm3 – (3/4 x 947611008 mm3) = 2025291744 mm3
Slow St. Concrete Volume = 912000000 mm3 – (1/4 x 947611008 mm3) = 675097248 mm3
(TOP LEVEL)
Total Wall Length = 5080 mm+ 2500 mm + 6420 mm + 3840 mm + 4920 mm = 22760 mm
Fast Setting Concrete Volume = 22760 mm x 60 mm x 2400 mm = 3277440000 mm3
Slow Setting Concrete Volume = 22760 mm x 20 mm x 2400 mm = 1092480000 mm3
Number of Doors = 4
Volume of Door = 315870336mm3
Total Volume of Doors = Volume of Door x Number of Doors
Total Volume of Doors = 315870336mm3 x 4 = 1263481344mm3
Subtract Doors from volume:
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Fast St. Concrete Volume = 3277440000 mm3 – (3/4 x 1263481344mm3) = 2329828992 mm3
Slow St. Concrete Volume = 1092480000 mm3 – (1/4 x 1263481344mm3) = 776609664 mm3
21.1.3 First Floor Slab
Slab Thickness = 200 mm
First Floor Slow Setting Concrete Area = 9360 mm x 9360 mm = 87609600 mm2
First Floor Slow Setting Concrete Volume = First Floor Concrete Area x Slab Thickness
= 87609600 mm2 x 200 mm
= 1.752192 x 1010 mm3
Area of StairCase = 2400 mm x 900 mm = 2160000 mm2
Volume of StairCase = 2160000 mm2 x 200 mm = 432000000 mm3
Total First Floor Slow Setting Concrete Volume = 1.752192 x 1010 mm3 - 432000000 mm3
= 1.708992 x 1010 mm3
First Floor Fast Setting Concrete Area = [(30 mm x 9420 mm) x 2] + [(30 mm x 9360 mm) x 2]
= 11226800 mm2
First Floor Fast Setting Concrete Volume = First Floor Concrete Area x Slab Thickness
= 11226800 mm2 x 200mm
= 225360000 mm3
21.1.4 Roof
Slab Thickness = 200 mm
Roof Slow Setting Concrete Area = 9360 mm x 9360 mm = 87609600 mm2
Roof Slow Setting Concrete Volume = Roof Concrete Area x Slab Thickness
= 87609600 mm2 x 200 mm
= 1.752192 x 1010 mm3
Roof Fast Setting Concrete Area = [(30 mm x 9420 mm) x 2] + [(30 mm x 9360 mm) x 2]
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= 11226800 mm2
Roof Fast Setting Concrete Volume = Roof Concrete Area x Slab Thickness
= 11226800 mm2 x 200mm
= 225360000 mm3
21.1.5 Foundations
Assumption: Slab Thickness of 400 mm
Fast Setting Concrete Area = [(30 mm x 9420 mm) x 2] + [(30 mm x 9360 mm) x 2]
= 11226800 mm2
Fast Setting Concrete Volume = First Floor Concrete Area x Slab Thickness
= 11226800 mm2 x 400mm
= 4490720000mm3
Slow Setting Concrete Area = 9360 mm x 9360 mm = 87609600 mm2
Slow Setting Concrete Volume = First Floor Concrete Area x Slab Thickness
= 87609600 mm2 x 400 mm
= 3.504384 x 1010 mm3
21.1.6 TOTAL SLOW SETTING CONCRETE VOLUME
1.297969782 x 1010 mm3 + 675097248 mm3 + 776609664 mm3 + 1.708992 x 1010 mm3 + 1.752192
x 1010 mm3 + 3.504384 x 1010 mm3
= 8.408636473 x 1010 mm3 or 84.1 m3
21.1.7 TOTAL FAST SETTING CONCRETE VOLUME
1.460216004 x1010 mm3 + 2025291744 mm3 + 2329828992 mm3 + 225360000 mm3 +225360000
mm3 + 4490720000mm3
= 2.369589678 x 1010 mm3 or 23.7 m3
173
MDDP – Megascale 3D Printing
Group 2
21.2 Concrete Mixing Calculations
174
MDDP – Megascale 3D Printing
Group 2
22 APPENDIX 4 – CONCRETE FLUID MECHANICS
22.1 Fast Setting Mix Calculations
Known/Estimated
Value
System Parameters
Volumetric flow-rate (Q)
0.324 m3/hr
Internal Pipe Diameter (D)
0.1 m
Density (ρ)
2350 kg/m3
Viscosity (µ)
400 Pa.s
Length (L)
25 m
Gravitational force (g)
9.81 m/s2
Elevation (h)
10 m
Multiple of D* (x)
(4 x 35) + 75 =215
Table x: The values required to complete the necessary fluid mechanics calculations
*The value for x is derived from the number of 90° bends and T-junctions/surge chambers in the
pipeline. (Ref 19)
Mean Velocity:
𝑈 =
4𝑄
4 × (0 324)
=
= 41 25 𝑚⁄ℎ𝑟 𝑟 0 011 𝑚⁄𝑠
𝜋𝐷
𝜋0 1
Reynolds Number:
𝑅𝑒 =
𝜌𝑈 𝐷 2350 × 0 011 × 0 1
=
= 0 0065
𝜇
400
Friction Factor:
𝐶 =
16
= 2461 5
0 0065
Shear Stress (τw) and Viscous Sub-layer (δ)
𝜏 =𝐶
1
𝜌𝑈
2
𝜏 = −𝜇
= 2461 5 × 0 5 × 2350 × 0 011 = ± 345 0 𝑃𝑎
𝜕𝑈
𝜕𝑦
After integration and rearrangement;
175
MDDP – Megascale 3D Printing
𝛿=𝜇
Group 2
𝑈
0 011
= 400
= 0 013 𝑚 𝑟 13 𝑚𝑚
𝜏
345
Pressure Drop:
∆𝑃 =
1
𝜌𝑈
2
𝐶
4𝐿
4 × 25
= 0 5 × 2350 × 0 011 × 2461 5 ×
= 349,964 𝑃𝑎
𝐷
01
𝑟 3 5 𝑏𝑎𝑟
Pump Demand:
∆𝑃 =
1
𝜌𝑈
2
𝐶
4𝐿
1
+ 𝜌𝑔ℎ + 𝜌𝑈
𝐷
2
𝐶
4(𝑥𝐷)
𝐷
∆𝑃 = 349,964 + (2350 × 9 81 × 10) + 0 5 × 2350 × 0 011 × 2461 5 ×
∆𝑃 = 881,468 𝑃𝑎
4 × 215 × 0 1
01
𝑟 8 8 𝑏𝑎𝑟
Pump Power:
𝑃 = 𝑄∆𝑃 =
0 324
× 881,468 = 79 3 𝑊
3600
22.2 Slow Setting Mix Calculations
Known/Estimated
Value
System Parameters
Volumetric flow-rate (Q)
2.42 m3/hr
Internal Pipe Diameter (D)
0.15 m
Density (ρ)
2250 kg/m3
Viscosity (µ)
300 Pa.s
Length (L)
25 m
Gravitational force (g)
9.81 m/s2
Elevation (h)
10 m
Multiple of D* (x)
(4 x 35) + 75 =215
Table x: The values required to complete the necessary fluid mechanics calculations
Mean Velocity:
𝑈 =
4𝑄
4 × (2 42)
=
= 136 94 𝑚⁄ℎ𝑟 𝑟 0 038 𝑚⁄𝑠
𝜋𝐷
𝜋0 15
176
MDDP – Megascale 3D Printing
Group 2
Reynolds Number:
𝜌𝑈 𝐷 2250 × 0 038 × 0 15
=
= 0 043
𝜇
300
𝑅𝑒 =
Friction Factor:
𝐶 =
16
= 374 3
0 043
Shear Stress (τw) and Viscous Sub-layer (δ)
𝜏 =𝐶
1
𝜌𝑈
2
𝜏 = −𝜇
= 374 3 × 0 5 × 2250 × 0 038 = ± 608 1 𝑃𝑎
𝜕𝑈
𝜕𝑦
After integration and rearrangement;
𝛿=𝜇
𝑈
0 038
= 300
= 0 019 𝑚 𝑟 19 𝑚𝑚
𝜏
608 1
Pressure Drop:
∆𝑃 =
1
𝜌𝑈
2
𝐶
4𝐿
4 × 25
= 0 5 × 2250 × 0 038 × 374 3 ×
= 405,367 𝑃𝑎
𝐷
0 15
𝑟 4 1 𝑏𝑎𝑟
Pump Demand:
1
∆𝑃 = 405,367 𝑃𝑎 + 𝜌𝑔ℎ + 𝜌𝑈
2
𝐶
4(𝑥𝐷)
𝐷
∆𝑃 = 405,367 + (2350 × 9 81 × 10) + 0 5 × 2250 × 0 038 × 374 3 ×
∆𝑃 = 1,158,825 𝑃𝑎
𝑟 11 6 𝑏𝑎𝑟
Pump Power:
𝑃 = 𝑄∆𝑃 =
2 42
× 1,158,825 = 779 𝑊
3600
𝑟 0 78 𝑘𝑊
177
4 × 215 × 0 15
0 15
MDDP – Megascale 3D Printing
Group 2
23 APPENDIX 5 – ADDITIONAL DRAWINGS
23.1 Reinforcement Drawings
23.1.1 Reinforcement Parts
Figure 77 - Reinforcement Node in Walls
Figure 78 - Reinforcement Staple
178
MDDP – Megascale 3D Printing
Group 2
Figure 79 - Reinforcement Connector for Slabs
23.1.2 Reinforcement Corner Layout
Figure 80 - Reinforcement Corner Layout
179
MDDP – Megascale 3D Printing
Group 2
23.1.3 Reinforcement Slab or Foundation Layout
Figure 81 - Reinforcement Slab or Foundation Layout
180
MDDP – Megascale 3D Printing
Group 2
24 APPENDIX 6 – FINANCE SHEETS
24.1 Printed Method Profit and Loss Year One
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation ( b)
Production Wages*
Purchase of Printer
Purchase of Land (c )
Planning Permission (d )
Transportation of Printer
Stamp Duty for Land (e )
Land Registry Fee
Gross Profit
Overheads
Rent (f )
Utility Bills
Internet (g)
Mobile Phone Bills (h )
Council Tax (i)
Business Insurance (k)
Office maintenance (including cleaning)
Legal Fees (l )
Office Supplies
Employee Travel
Year 1
£
£
4,600,000.00
4,600,000.00
£
£
£
£
£
£
£
£
£
£
2,250,000.00
47,000.00
467,200.00
70,000.00
400,000.00
17,325.00
200.00
12,000.00
270.00
1,336,005.00
Computers (m)
Furnishing
Software
Business Licence, Fees and Permits
Photocopier
Landline Phone
Salaries**
Total Overhead
Operating Income
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
12,000.00
800.00
480.00
7,920.00
2,495.33
20,000.00
600.00
2,000.00
300.00
10,000.00
2,700.00
3,500.00
1,500.00
3,000.00
500.00
500.00
72.00
829,000.00
897,367.33
438,637.67
Other Expenses
Loan repayment
EBIT
Income Tax
£
£
£
438,637.67
105,273.04
Net Profit
£
333,364.63
Local Authority Search Fees (Annually)
(a) - Based on 23 houses sold at £200,000 each. - Search in colchester Essex 3 bed
house on zoopla
(b) - Depretiation taken at 10%
(c ) - Land purchased in Essex, 81 acres £400000 http://www.uklanddirectory.org.uk/land-for-sale.asp?id=11154
(d) - Quote from essex county council based on the erection of 45 houses. http://www.planningportal.gov.uk/PpFormServer/genpub/en/StandaloneFeeC
alcFormServlet
(e ) - Stamp duty thresholds from http://www.hmrc.gov.uk/sdlt/intro/ratesthresholds.htm
(f ) - Based on a £1000 a month office in Guildford advertised on GumTree
(g ) - Based on £40 a month contract
(h) - 22 £30 a month contracts
(i) - Based on band F guildford council tax
(j) - Contents, buildings, public liability and employment liability insurance
(k) - Charging lawyer
(m) - 10 computers at £350
Total Concrete = 84.1 + 23.7 m3 = 107.8 m3
100 pounds per cubic meter – 107.8 * 100 = £10780
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
Based on land bought in the south east.
45 houses built 23 sold
181
MDDP – Megascale 3D Printing
Group 2
24.2 Printed Method Profit and Loss Year Two
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation
Production Wages*
Planning Permission
Gross Profit
Overheads
Rent
Utility Bills
Internet
Mobile Phone Bills (b)
Council Tax
Business Insurance
Office maintenance (including cleaning)
Legal Fees
Office Supplies
Employee Travel
Year 2
Local Authority Search Fees (Annually)
Computers (c )
Furnishing
Software
Landline Phone
Salaries**
Total Overhead
Operating Income
Other Expenses
Loan repayment
EBIT
Income Tax
Net Profit
(a) - Based on 45 houses sold at £200,000 each. - Search in colchester
Essex 3 bed house on zoopla
(b) - 24 £30 a month contracts
(c) - 2 new computers at £350 each
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
Inflation at 2.7% taken December 2012
45 houses built 22 left unsold
182
£
£
9,000,000.00
9,000,000.00
£
£
£
£
£
2,250,000.00
47,000.00
467,200.00
17,325.00
6,218,475.00
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
12,324.00
821.60
492.96
8,133.84
2,562.70
20,540.00
616.20
2,054.00
308.10
10,270.00
2,772.90
700.00
500.00
500.00
72.00
851,000.00
913,668.30
5,304,806.70
£
£
£
5,304,806.70
1,273,153.61
4,031,653.09
MDDP – Megascale 3D Printing
Group 2
24.3 Printed Method Profit and Loss Year Three
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation
Purchase of Printer
Transportation of Printer
Production Wages*
Planning Permission
Gross Profit
Overheads
Rent
Utility Bills
Internet
Mobile Phone Bills (b)
Council Tax
Business Insurance
Office maintenance (including cleaning)
Legal Fees
Office Supplies
Employee Travel
Year 3
Local Authority Search Fees (Annually)
Computers ( c)
Furnishing
Software
Landline Phone
Salaries**
Total Overhead
Operating Income
Other Expenses
Loan repayment
EBIT
Income Tax
Net Profit
£
£
13,600,000.00
13,600,000.00
£
£
£
£
£
£
£
4,500,000.00
54,000.00
70,000.00
200.00
1,280,000.00
34,650.00
7,661,150.00
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
12,693.72
846.25
507.75
11,170.47
2,639.59
21,156.20
634.69
2,115.62
317.34
10,578.10
2,856.09
2,599.21
515.00
515.00
74.16
1,280,000.00
1,349,219.18
6,311,930.82
£
£
£
6,311,930.82
1,514,863.40
4,797,067.43
(a) - Based on 68 houses sold at £200,000 each. - Search in colchester
Essex 3 bed house on zoopla
(b) - 31 £30 a month contracts
( c)- 7 new computers at £350 each
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
inflation predicted as 3%
90 houses built
22 houses remian from year two sold in addition to half of the 90 maximum built in year 3.
45 houses remain unsold
183
MDDP – Megascale 3D Printing
Group 2
24.4 Printed Method Profit and Loss Year Four
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation
Production Wages*
Planning Permission
Purchase of Land (b )
Stamp Duty for Land
Land Registry Fee
Gross Profit
Overheads
Rent
Utility Bills
Internet
Mobile Phone Bills (c )
Council Tax
Business Insurance
Office maintenance (including cleaning)
Legal Fees
Office Supplies
Employee Travel
Year 4
Local Authority Search Fees (Annually)
Computers (d)
Furnishing
Software
Landline Phone
Salaries**
Total Overhead
Operating Income
Other Expenses
Loan repayment
EBIT
Income Tax
Net Profit
(a) - Based on 90 houses sold at £200,000 each. - Search in colchester
Essex 3 bed house on zoopla
(b) - Land purchased in Essex, 377 acres £2.25 million http://www.uklandandfarms.co.uk/search/detail.aspx?PropertyRef=67
313_BED120322
(b ) - 34 £30 a month contracts
(d)- 3 new computers at £350 each
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
Based on land bought in the south east.
90 houses built
90 houses sold
45 houses left unsold
184
£
£
18,000,000.00
18,000,000.00
£
£
£
£
£
£
£
£
4,500,000.00
279,000.00
934,400.00
34,650.00
2,250,000.00
12,000.00
270.00
9,989,680.00
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
13,074.53
871.64
522.98
11,505.59
2,718.77
21,790.89
653.73
2,179.09
326.86
10,895.44
2,941.77
1,147.36
530.45
530.45
76.38
1,302,000.00
1,371,765.93
8,617,914.07
£
£
8,617,914.07
2,068,299.38
£
6,549,614.69
MDDP – Megascale 3D Printing
Group 2
24.5 Printed Method Profit and Loss Year Five
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation
Production Wages*
Planning Permission
Purchase of Printer
Transportation of Printer
Gross Profit
Overheads
Purchase Office (b )
Utility Bills
Internet
Mobile Phone Bills ( c)
Council Tax
Business Insurance
Office maintenance (including cleaning)
Legal Fees (k)
Office Supplies
Employee Travel
Year 5
Local Authority Search Fees (Annually)
Computers (d )
Furnishing
Software
Photocopier
Landline Phone
Salaries**
Total Overhead
Operating Income
Other Income (Expenses)
Loan repayment
EBIT
Income Tax
Net Profit
(a) - Based on 45 houses sold at £200,000 each. - Search in colchester
Essex 3 bed house on zoopla
£
£
22,800,000.00
22,800,000.00
£
£
£
£
£
£
£
6,750,000.00
286,000.00
1,401,600.00
51,975.00
70,000.00
200.00
14,292,200.00
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
1,690,000.00
897.78
538.67
17,776.13
2,800.34
22,444.61
673.34
2,244.46
336.67
11,222.31
3,030.02
1,181.78
546.36
546.36
500.00
78.68
1,884,000.00
3,638,817.52
10,653,382.48
£
£
£
500,000.00
10,153,382.48
2,436,811.79
£
7,716,570.68
(b) - Purchase office - http://www.primelocation.com/forsale/details/20916114?search_identifier=faa627fa57dfaa32d87f6e041aa
40c18
(c) - 46 £30 a month contracts
(d) - 12 computers at £350
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
Build 135 houses
Sell 23 * 3 (69) houses from each pritner in addition to the 45 remaining from previous year.
69 houses remain un sold
Relocated and bought office in London
185
MDDP – Megascale 3D Printing
Group 2
24.6 Printed Method Salaries and Contractor Wages
Year One Salaries **
Position
Site Manager
Safety Inspector
Operating Engineer
Secutiry Guards
Office Engineer (Civil & Mechincal 2 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
CEO
Accountant
Plumber
Electrician
TOTAL
Location
On site
N/A
On site
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Production Wages*
Position
Builder
4 Builders one month to complete house
Location
On site
Number
Year 2 Salaries **
Position
Site Manager
Safety Inspector
Operating Engineer
Secutiry Guards
Office Engineer (Civil & Mechincal 2 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
Accountant
CEO
Plumber
Electrician
TOTAL
Production Wages*
Position
Builder
Salary
3
1
6
3
4
1
1
1
1
1
1
1
1
1
1
27
£135,000
£25,000
£180,000
£45,000
£120,000
£45,000
£15,000
£22,000
£22,000
£28,000
26000
£60,000
£50,000
£27,000
£29,000
£829,000
Salary (Daily)
Total
16 £
80.00
Location
On site
N/A
On site
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Location
On site
Number
186
Total
£45,000
£25,000
£30,000
£15,000
£30,000
£45,000
£15,000
£22,000
£22,000
£28,000
26000
£60,000
£50,000
£27,000
£29,000
Salary
3
1
6
3
4
1
1
1
2
1
1
1
1
1
1
28
£467,200
Total
£45,000
£25,000
£30,000
£15,000
£30,000
£45,000
£15,000
£22,000
£22,000
£28,000
26000
£50,000
£60,000
£27,000
£29,000
£135,000
£25,000
£180,000
£45,000
£120,000
£45,000
£15,000
£22,000
£44,000
£28,000
26000
£50,000
£60,000
£27,000
£29,000
£851,000
Salary (hourly)
Total
16 £
80.00 £
467,200.00
MDDP – Megascale 3D Printing
Year Three Salaries **
Position
Site Manager
Safety Inspector
Operating Engineer
Secutiry Guards
Office Engineer (Civil & Mechincal 2 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
Accountant
CEO
Plumber
Electrician
TOTAL
Production Wages*
Position
Builder
Year Four Salaries **
Position
Site Manager
Safety Inspector
Operating Engineer
Secutiry Guards
Office Engineer (Civil & Mechincal 2 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
Accountant
CEO
Plumber
Electrician
TOTAL
Production Wages*
Position
Builder
Group 2
Location
On site
N/A
On site
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Location
On site
Number
Salary
6
1
6
6
8
2
1
1
2
2
1
1
1
2
2
42
£270,000
£25,000
£180,000
£90,000
£240,000
£90,000
£15,000
£22,000
£44,000
£56,000
26000
£50,000
£60,000
£54,000
£58,000
£1,280,000
Salary (hourly)
Total
32 £
80.00 £
Location
On site
N/A
On site
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Location
On Site
Number
187
Total
£45,000
£25,000
£30,000
£15,000
£30,000
£45,000
£15,000
£22,000
£22,000
£28,000
26000
£50,000
£60,000
£27,000
£29,000
Salary
6
1
6
6
8
2
1
1
3
2
1
1
1
2
2
43
934,400.00
Total
£45,000
£25,000
£30,000
£15,000
£30,000
£45,000
£15,000
£22,000
£22,000
£28,000
26000
£50,000
£60,000
£27,000
£29,000
£270,000
£25,000
£180,000
£90,000
£240,000
£90,000
£15,000
£22,000
£66,000
£56,000
26000
£50,000
£60,000
£54,000
£58,000
£1,302,000
Salary (hourly)
Total
32 £
80.00 £
934,400.00
MDDP – Megascale 3D Printing
Group 2
Year Five Salaries **
Position
Site Manager
Safety Inspector
Operating Engineer
Secutiry Guards
Office Engineer (Civil & Mechincal 2 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
Accountant
CEO
Plumber
Electrician
TOTAL
Production Wages*
Position
Builder
Location
On site
N/A
On site
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Location
On site
Number
Salary
Total
9
1
9
9
12
3
2
1
4
3
2
1
1
3
3
63
£45,000
£25,000
£30,000
£15,000
£30,000
£45,000
£15,000
£22,000
£22,000
£28,000
26000
£50,000
£60,000
£27,000
£29,000
£405,000
£25,000
£270,000
£135,000
£360,000
£135,000
£30,000
£22,000
£88,000
£84,000
52000
£50,000
£60,000
£81,000
£87,000
£1,884,000
Salary (hourly)
Total
48 £
80.00
Assumptions
No extra pay for un sociable hours
24.7 Printed Method Five Year Cash Flow Statement
Cash Flow Statment
Cash flows from operating activities
Year 1
Year 2
Year 3
Year 4
Year 5
Sales
Cash Sales
Sales on Credit
Total Sales
Direct Cost of Sales
Personnel in Cost of Sales
Total Cost of Sales
Gross Margin
Operating Expenses
Wages and Salaries
Depreciation
Other Operating Expenses
EBIT
Interest (a)
Taxes
Net Cash Flow Operations
Cash flows from investing activities
Purchase of equipment
Net cash flow investments
Cash flows from financing activities
Dividends paid
Loan
Loan Repayment
£
£
£
£
£
£
£
4,600,000.00
4,600,000.00
2,679,795.00
467,200.00
3,146,995.00
1,453,005.00
£
£
£
£
£
£
£
9,000,000.00
9,000,000.00
2,267,325.00
467,200.00
2,734,525.00
6,265,475.00
£
£
£
£
£
£
£
13,600,000.00
13,600,000.00
4,534,850.00
1,280,000.00
5,814,850.00
7,785,150.00
£
£
£
£
£
£
£
829,000.00
54,000.00
68,367.33
501,637.67
100,000.00
120,393.04
281,244.63
£
£
£
£
£
£
£
851,000.00
47,000.00
62,668.30
5,304,806.70
1,273,153.61
4,031,653.09
£
£
£
£
£
£
£
1,280,000.00
54,000.00
69,219.18
6,381,930.82
1,531,663.40
4,850,267.43
£
£
70,000.00 £
70,000.00 £
£
£
£
Net increase in cash
Cash beggining of year
Cash end of year
£
£
£
Discount Rate
NPV
£
-
£ 18,000,000.00
£
£ 18,000,000.00
£ 6,796,920.00
£ 934,400.00
£ 7,731,320.00
£ 10,268,680.00
£ 22,800,000.00
£
£ 22,800,000.00
£ 6,750,200.00
£ 1,401,600.00
£ 8,151,800.00
£ 14,648,200.00
£
£
£
£
£
£
£
£ 1,884,000.00
£ 286,000.00
£
64,817.52
£ 12,413,382.48
£
£ 2,979,211.79
£ 9,434,170.68
1,302,000.00
279,000.00
69,765.93
8,617,914.07
2,068,299.38
6,549,614.69
£
£
70,000.00 £
70,000.00 £
-
£
1,000,000.00 £
1,000,000.00 £
403,165.31 £
£
£
485,026.74 £
£
£
654,961.47 £
£
£
211,244.63 £
£
211,244.63 £
3,628,487.78 £
211,244.63 £
3,839,732.41 £
50%
5,076,885.23
Assume a 1 Million loan that is paid back in the first year with 10% interest rate
188
£ 1,760,000.00
£ 1,760,000.00
943,417.07
-
4,295,240.68 £ 5,894,653.22 £ 6,730,753.61
3,628,487.78 £ 4,295,240.68 £ 5,894,653.22
7,923,728.46 £ 10,189,893.90 £ 12,625,406.84
£1,401,600
MDDP – Megascale 3D Printing
Group 2
24.8 Conventional Method Profit and Loss Year One
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation
Production Wages*
Purchase of Land (b)
Planning Permission (c )
Stamp Duty for Land (d )
Land Registry Fee
Gross Profit
Overheads
Rent (e)
Utility Bills
Internet (f )
Mobile Phone Bills (g)
Council Tax (h)
Business Insurance (i)
Office maintenance (including cleaning)
Legal Fees (j)
Office Supplies
Employee Travel
Year 1
Local Authority Search Fees (Annually)
Computers (k)
Furnishing
Software
Business Licence, Fees and Permits
Photocopier
Landline Phone
Salaries**
Total Overhead
Operating Income
Other Expenses
Loan repayment
EBIT
Income Tax
Net Profit
£
£
4,600,000.00
4,600,000.00
£
£
£
£
£
£
£
£
2,250,000.00
40,000.00
1,401,600.00
400,000.00
17,325.00
12,000.00
270.00
478,805.00
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
-£
12,000.00
800.00
480.00
7,920.00
2,495.33
20,000.00
600.00
2,000.00
300.00
10,000.00
2,700.00
3,500.00
1,500.00
3,000.00
500.00
500.00
72.00
589,000.00
657,367.33
178,562.33
£
-£
-£
178,562.33
42,854.96
-£
135,707.37
(a) - Based on 23 houses sold at £200,000 each. - Search in colchester Essex 3 bed
house on zoopla
(b) - Land purchased in Essex, 81 acres £400000 http://www.uklanddirectory.org.uk/land-for-sale.asp?id=11154
(c) - Quote from essex county council based on the erection of 45 houses. http://www.planningportal.gov.uk/PpFormServer/genpub/en/StandaloneFeeC
alcFormServlet
(d) - Stamp duty thresholds from http://www.hmrc.gov.uk/sdlt/intro/ratesthresholds.htm
(e) - Based on a £1000 a month office in Guildford advertised on GumTree
(f ) - Based on £40 a month contract
(g) - 22 £30 a month contracts
(h ) - Based on band F guildford council tax
(i) - Contents, buildings, public liability and employment liability insurance
(j) - Charging lawyer
(k) - 10 computers at £350
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
Based on land bought in the south east.
45 houses built 23 sold
189
MDDP – Megascale 3D Printing
Group 2
24.9 Conventional Method Profit and Loss Year Two
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation
Production Wages*
Planning Permission
Gross Profit
Overheads
Rent
Utility Bills
Internet
Mobile Phone Bills (b )
Council Tax
Business Insurance
Office maintenance (including cleaning)
Legal Fees
Office Supplies
Employee Travel
Year 2
Local Authority Search Fees (Annually)
Computers (c )
Furnishing
Software
Landline Phone
Salaries**
Total Overhead
Operating Income
Other Expenses
Loan repayment
EBIT
Income Tax
Net Profit
(a) - Based on 45 houses sold at £200,000 each. - Search in colchester
Essex 3 bed house on zoopla
(b) - 24 £30 a month contracts
( c) - 2 new computers at £350 each
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
Inflation at 2.7% taken December 2012
45 houses built 22 left unsold
190
£
£
9,000,000.00
9,000,000.00
£
£
£
£
£
2,250,000.00
40,000.00
1,401,600.00
17,325.00
5,291,075.00
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
12,324.00
821.60
492.96
8,640.00
2,562.70
20,540.00
616.20
2,054.00
308.10
10,270.00
2,772.90
700.00
500.00
500.00
72.00
582,000.00
645,174.46
4,645,900.54
£
£
£
4,645,900.54
1,115,016.13
3,530,884.41
MDDP – Megascale 3D Printing
Group 2
24.10 Conventional Method Profit and Loss Year Three
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation
Production Wages*
Planning Permission
Gross Profit
Overheads
Rent
Utility Bills
Internet
Mobile Phone Bills (b)
Council Tax
Business Insurance
Office maintenance (including cleaning)
Legal Fees
Office Supplies
Employee Travel
Year 3
Local Authority Search Fees (Annually)
Computers (c)
Furnishing
Software
Landline Phone
Salaries**
Total Overhead
Operating Income
Other Expenses
Loan repayment
EBIT
Income Tax
Net Profit
£
£
13,600,000.00
13,600,000.00
£
£
£
£
£
4,500,000.00
40,000.00
2,803,200.00
34,650.00
6,222,150.00
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
12,693.72
846.25
507.75
11,160.00
2,639.59
21,156.20
634.69
2,115.62
317.34
10,578.10
2,856.09
2,599.21
515.00
515.00
74.16
868,000.00
937,208.70
5,284,941.30
£
£
£
5,284,941.30
1,268,385.91
4,016,555.39
(a) - Based on 68 houses sold at £200,000 each. - Search in colchester
Essex 3 bed house on zoopla
(b) - 31 £30 a month contracts
(c)- 7 new computers at £350 each
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
inflation predicted as 3%
90 houses built
22 houses remian from year two sold in addition to half of the 90 maximum built in year 3.
45 houses remain unsold
191
MDDP – Megascale 3D Printing
Group 2
24.11 Conventional Method Profit and Loss Year Four
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation
Production Wages*
Planning Permission
Purchase of Land (b)
Stamp Duty for Land
Land Registry Fee
Gross Profit
Overheads
Rent
Utility Bills
Internet
Mobile Phone Bills (c )
Council Tax
Business Insurance
Office maintenance (including cleaning)
Legal Fees
Office Supplies
Employee Travel
Year 4
£
£
18,000,000.00
18,000,000.00
£
£
£
£
£
£
£
£
6,750,000.00
265,000.00
2,803,200.00
34,650.00
2,250,000.00
12,000.00
270.00
5,884,880.00
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
13,074.53
871.64
522.98
12,240.00
2,718.77
21,790.89
653.73
2,179.09
326.86
10,895.44
2,941.77
1,147.36
530.45
530.45
76.38
890,000.00
960,500.35
4,924,379.65
£
4,924,379.65
Income Tax
£
1,181,851.12
Net Profit
£
3,742,528.54
Local Authority Search Fees (Annually)
Computers (d )
Furnishing
Software
Landline Phone
Salaries**
Total Overhead
Operating Income
Other Expenses
Loan repayment
EBIT
(a) - Based on 90 houses sold at £200,000 each. - Search in colchester
Essex 3 bed house on zoopla
(b) - Land purchased in Essex, 377 acres £2.25 million http://www.uklandandfarms.co.uk/search/detail.aspx?PropertyRef=67
313_BED120322
(c ) - 34 £30 a month contracts
( d)- 3 new computers at £350 each
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
Based on land bought in the south east.
90 houses built
90 houses sold
45 houses left unsold
192
MDDP – Megascale 3D Printing
Group 2
24.12 Conventional Method Profit and Loss Year Five
Profit and Loss
Operating Revenue
Product Sales (a)
Total Operating Revenue
Operating Expenses
Cost of Materials
Depreciation
Production Wages*
Planning Permission
Gross Profit
Overheads
Purchase Office ( b)
Utility Bills
Internet
Mobile Phone Bills (c )
Council Tax
Business Insurance
Office maintenance (including cleaning)
Legal Fees
Office Supplies
Employee Travel
Year 5
Local Authority Search Fees (Annually)
Computers (d)
Furnishing
Software
Photocopier
Landline Phone
Salaries**
Total Overhead
Operating Income
Other Income (Expenses)
Loan repayment
EBIT
Income Tax
Net Profit
£
£
22,800,000.00
22,800,000.00
£
£
£
£
£
5,700,000.00
265,000.00
4,204,800.00
51,975.00
12,630,200.00
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
1,690,000.00
897.78
538.67
16,560.00
2,800.34
22,444.61
673.34
2,244.46
336.67
11,222.31
3,030.02
1,181.78
546.36
546.36
500.00
78.68
1,266,000.00
3,019,601.39
9,610,598.61
£
£
£
£
500,000.00
9,110,598.61
2,186,543.67
6,924,054.94
(a) - Based on 45 houses sold at £200,000 each. - Search in colchester
Essex 3 bed house on zoopla
(b) - Purchase office - http://www.primelocation.com/forsale/details/20916114?search_identifier=faa627fa57dfaa32d87f6e041aa
40c18
(c ) - 46 £30 a month contracts
(d) - 12 computers at £350
Assumptions:
Wages do not increase with inflation.
Based on houses built in the south east.
Build 135 houses
Sell 23 * 3 (69) houses from each pritner in addition to the 45 remaining from previous year.
69 houses remain un sold
Relocated and bought office in London
193
MDDP – Megascale 3D Printing
Group 2
24.13 Conventional Method Salaries and Contractor Wages
Year One Salaries **
Position
Site Manager
Safety Inspector
Secutiry Guards
Office Engineer (Civil & Mechincal 1 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
CEO
Accountant
Plumber
Electrician
TOTAL
Location
On site
N/A
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On site
On site
Number
Production Wages*
Position
Builder
4 buider build a house per 3 months
Location
On site
Number
Year 2 Salaries **
Position
Site Manager
Safety Inspector
Secutiry Guards
Office Engineer (Civil & Mechincal 1 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
Accountant
CEO
Plumber
Electrician
TOTAL
Production Wages*
Position
Builder
Total
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
135,000.00
25,000.00
45,000.00
60,000.00
45,000.00
15,000.00
22,000.00
22,000.00
28,000.00
26,000.00
60,000.00
50,000.00
27,000.00
29,000.00
589,000.00
Salary (daily)
Total
48 £
80.00 £
1,401,600.00
3
1
3
2
1
1
1
1
1
1
1
1
1
1
19
Salary
£
£
£
£
£
£
£
£
£
£
£
£
£
£
Location
On site
N/A
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Location
On site
Number
£
45,000.00
25,000.00
15,000.00
30,000.00
45,000.00
15,000.00
22,000.00
22,000.00
28,000.00
26,000.00
60,000.00
50,000.00
27,000.00
29,000.00
3
1
3
2
1
1
1
2
1
1
1
1
1
1
20
194
Salary
£ 45,000.00
£ 25,000.00
£ 15,000.00
£ 30,000.00
£ 45,000.00
£ 15,000.00
£ 22,000.00
£ 22,000.00
£ 28,000.00
£ 26,000.00
£ 50,000.00
£ 60,000.00
£ 27,000.00
£ 29,000.00
Total
£ 135,000.00
£ 25,000.00
£ 45,000.00
£ 60,000.00
£ 45,000.00
£ 15,000.00
£ 22,000.00
£ 44,000.00
£ 28,000.00
£ 26,000.00
£ 50,000.00
£ 60,000.00
£ 27,000.00
£ 29,000.00
£ 582,000.00
Salary (daily)Total
48.00 £
80.00 £ 1,401,600.00
MDDP – Megascale 3D Printing
Year Three Salaries **
Position
Site Manager
Safety Inspector
Secutiry Guards
Office Engineer (Civil & Mechincal 2 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
Accountant
CEO
Plumber
Electrician
TOTAL
Production Wages*
Position
Builder
Year Four Salaries **
Position
Site Manager
Safety Inspector
Secutiry Guards
Office Engineer (Civil & Mechincal 2 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
Accountant
CEO
Plumber
Electrician
TOTAL
Production Wages*
Position
Builder
Group 2
Location
On site
N/A
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Location
On site
Number
Total
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
270,000.00
25,000.00
90,000.00
120,000.00
90,000.00
15,000.00
22,000.00
44,000.00
56,000.00
26,000.00
50,000.00
60,000.00
54,000.00
58,000.00
868,000.00
Salary (hourly)
Total
96 £
80.00 £
2,803,200.00
6
1
6
4
2
1
1
2
2
1
1
1
2
2
32
Salary
£
£
£
£
£
£
£
£
£
£
£
£
£
£
Location
On site
N/A
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Location
On site
Number
45,000.00
25,000.00
15,000.00
30,000.00
45,000.00
15,000.00
22,000.00
22,000.00
28,000.00
26,000.00
50,000.00
60,000.00
27,000.00
29,000.00
6
1
6
4
2
1
1
3
2
1
1
1
2
2
33
195
Salary
£ 45,000.00
£ 25,000.00
£ 15,000.00
£ 30,000.00
£ 45,000.00
£ 15,000.00
£ 22,000.00
£ 22,000.00
£ 28,000.00
£ 26,000.00
£ 50,000.00
£ 60,000.00
£ 27,000.00
£ 29,000.00
Total
£ 270,000.00
£ 25,000.00
£ 90,000.00
£ 120,000.00
£ 90,000.00
£ 15,000.00
£ 22,000.00
£ 66,000.00
£ 56,000.00
£ 26,000.00
£ 50,000.00
£ 60,000.00
£ 54,000.00
£ 58,000.00
£ 890,000.00
Salary (daily)Total
96 £
80.00 £ 2,803,200.00
MDDP – Megascale 3D Printing
Group 2
Year Five Salaries **
Position
Site Manager
Safety Inspector
Secutiry Guards
Office Engineer (Civil & Mechincal 3 Each)
Project Manager
Receptionist
Sales Rep
Estate Agent
Architect
Marketer
Accountant
CEO
Plumber
Electrician
TOTAL
Location
On site
N/A
On site
Office
Office
Office
Office
Office
Office
Office
Office
Office
On Site
On Site
Number
Total
£
£
£
£
£
£
£
£
£
£
£
£
£
£
£
405,000.00
25,000.00
135,000.00
180,000.00
135,000.00
30,000.00
22,000.00
88,000.00
84,000.00
52,000.00
50,000.00
60,000.00
81,000.00
87,000.00
1,266,000.00
Production Wages*
Position
Builder
Location
Number
Salary (Daily)
Total
144 £
80.00 £
4,204,800.00
9
1
9
6
3
2
1
4
3
2
1
1
3
3
48
Salary
£
£
£
£
£
£
£
£
£
£
£
£
£
£
45,000.00
25,000.00
15,000.00
30,000.00
45,000.00
15,000.00
22,000.00
22,000.00
28,000.00
26,000.00
50,000.00
60,000.00
27,000.00
29,000.00
Assumptions
No extra pay for un sociable hours
Holidays Excluded
24.14 Conventional Method Five Year Cash Flow Statement
Cash Flow Statment
Year 1
Cash flows from operating activities
Year 2
Year 3
Year 4
Year 5
Sales
Cash Sales
Sales on Credit
Total Sales
Direct Cost of Sales
Personnel in Cost of Sales
Total Cost of Sales
Gross Margin
Operating Expenses
Wages and Salaries
Depreciation
Other Operating Expenses
EBIT
Interest
Taxes
Net Cash Flow Operations
Cash flows from investing activities
Purchase of equipment
Net cash flow investments
Cash flows from financing activities
Dividends paid
Loans
Loan Repayment
£
£
£
£
£
£
£
4,600,000.00
4,600,000.00
2,319,595.00
1,401,600.00
3,721,195.00
878,805.00
£ 9,000,000.00
£
£ 9,000,000.00
£ 2,267,325.00
£ 1,401,600.00
£ 3,668,925.00
£ 5,331,075.00
£ 13,600,000.00
£
£ 13,600,000.00
£ 4,534,650.00
£ 2,803,200.00
£ 7,337,850.00
£ 6,262,150.00
£
£
£
-£
£
-£
-£
589,000.00
40,000.00
308,367.33
58,562.33
100,000.00
14,054.96
144,507.37
£ 582,000.00
£ 40,000.00
£ 331,668.30
£ 4,377,406.70
£ 20,000.00
£ 1,050,577.61
£ 3,306,829.09
£ 868,000.00 £ 890,000.00 £ 1,266,000.00
£
40,000.00 £ 265,000.00 £ 265,000.00
£ 481,219.18 £ 481,765.93 £ 682,817.52
£ 4,872,930.82 £ 4,513,114.07 £ 10,681,382.48
£
£
£
£ 1,169,503.40 £ 1,083,147.38 £ 2,563,531.79
£ 3,703,427.43 £ 3,429,966.69 £ 8,117,850.68
£
£
£
£
£
£
-
-
0 £ 330,682.91 £
£ 1,000,000.00 £
£
£ 800,000.00 £ 200,000.00 £
Net increase in cash
Cash beggining of year
Cash end of year
£
£
£
Discount Rate
NPV
40%
£ 4,505,487.90
-
£ 18,000,000.00
£
£ 18,000,000.00
£ 9,046,920.00
£ 2,803,200.00
£ 11,850,120.00
£ 6,149,880.00
£
£
370,342.74 £
£
£
-
£ 22,800,000.00
£
£ 22,800,000.00
£ 5,700,000.00
£ 4,204,800.00
£ 9,904,800.00
£ 12,895,200.00
£ 1,760,000.00
£ 1,760,000.00
342,996.67 £
£
£
811,785.07
-
55,492.63 £ 2,776,146.18 £ 3,333,084.68 £ 3,086,970.02 £ 5,546,065.61
£ 55,492.63 £ 2,776,146.18 £ 3,333,084.68 £ 3,086,970.02
55,492.63 £ 2,831,638.81 £ 6,109,230.86 £ 6,420,054.70 £ 8,633,035.64
Assume £1000000 loan in first year and interest rate of 10%
196
MDDP – Megascale 3D Printing
Group 2
25 APPENDIX 7 – MATERIALS LISTS
Description
Procureme
Cost
nt Type
Weight of Parts
(incl. quantity) Manufacturer
(kg)
Manufacturer Part Manufacturer
Number
Part Name
System Assigned Revision
Phase
X001
X Axis Beam
X Axis
A
Beam supporting
Confirmed robotic arm and print
head.
1 Bought In
N/A
418.00
418.00 HepcoMotion
HB33L11000T
Construction
Beam
Aluminium Allow
X002
V Slide with Teeth
X Axis
A
Confirmed
Track for bearings to
run along
2 Bought In
N/A
132.84
265.68 HepcoMotion
PHSS33L10800R
V Slide
Stainless Steel
Slightly less than 11m to
allow room for buffer.
X003
V Slide without Teeth
X Axis
A
Confirmed
Track for bearings to
run along
2 Bought In
N/A
132.84
265.68 HepcoMotion
PHSS33L10800
V Slide
Stainless Steel
Slightly less than 11m to
allow room for buffer.
X004
Carriage Plate
X Axis
A
Confirmed
2 Bought In
N/A
60.00
120.00 HepcoMotion
AURD12833W5S
Magnetic Spa
4.10
Servomotors
Magnetic Spa
45.00
Servomotors
HTQ 120 M TENV
4A
HTQ 240 S TENV
AD
SSHDF50S24
Rack driven carriage
plate.
Motor for Robotic
Confirmed
Arm
Quantity
Individual Part
Weight (kg)
Part Number Part Name
Motor
X Axis
A
X006
Motor
X Axis
A
Confirmed Motor for Nozzle
1 Bought In
X007
Drive flange with
pinion.
X Axis
A
Confirmed
Drive flange with
pinion.
2 Bought In
N/A
8.60
17.20 HepcoMotion
X008
Buffer
X Axis
A
Confirmed Buffer unit
4 Bought In
N/A
1.03
4.12 HepcoMotion
X009
Bearings
X Axis
A
Confirmed Bearings for Carriage
8 Bought In
N/A
3.00
24.00 HepcoMotion
10 Bought In
N/A
56.46
564.60 HepcoMotion
MHDT401002000R5 Flat Track
Steel
10 Bought In
N/A
56.46
564.60 HepcoMotion
MHDT401002000
Steel
2 Bought In
N/A
60.00
120.00 HepcoMotion
AURD12833W5S
HTQ 300 S TEWC
AH
MHD89BRENL
Y001
Flat Track with teeth.
Y Axis
A
Y002
Flat track without teeth. Y Axis
A
Confirmed
Track for printer to run
along.
Y003
Carriage Plate
A
Confirmed
Rack driven carriage
plate.
Y Axis
4.10
45.00
BU33W
Buffer Unit
BHJR128CNS17
Bearings
Y004
Motor
Y Axis
A
Confirmed Motor
2 Bought In
Y005
Bearing block
Y Axis
A
Confirmed Bearings for Carriage
4 Bought In
N/A
14.00
Magnetic Spa
270.00
Servomotors
56.00 HepcoMotion
Y006
Bearing block
Drive flange with
pinion.
Y Axis
A
4 Bought In
N/A
14.00
56.00 HepcoMotion
MHD89BLENL
Y Axis
A
2 Bought In
N/A
8.60
17.20 HepcoMotion
SSHDF50S24
Y008
Mounting Plate
Y Axis
A
Z001
Z Axis Beam
Z Axis
A
Z002
V Slide with Teeth
Z Axis
A
Z003
V Slide without Teeth
Z Axis
A
Z004
Carriage Plate
Z Axis
A
Confirmed Bearings for Carriage
Drive flange with
Confirmed
pinion.
Mounting Plate for
Confirmed
Flat Tracks
Beam supporting X
Confirmed
axis.
Track for bearings to
Confirmed
run along
Track for bearings to
Confirmed
run along
Rack driven carriage
Confirmed
plate.
Y007
Z005
Motor
Z006
Drive flange with
pinion.
Z007
Buffer
Z008
Bearings
Z Axis
135.00
2 Bought In
Flat Track
Rack Driven
Carriage Plate
HTQ Series
Torque Motor
Bearing Blocks
Bearing Blocks
Drive Flange
Assembly
Various
0.31kW
Various
2.7kW
Stainless Steel
Aluminium with
rubber ends.
Steel
Tracks at 2m in length, 5
tracks per side.
Attachable.
Tracks at 2m in length, 5
tracks per side.
Attachable.
Stainless Steel
Various
13kW
Steel
Right handed.
Steel
Left handed.
Stainless Steel
0.00
2 Bought In
N/A
304.00
608.00 HepcoMotion
HB33L8000T
Construction
Beam
Aluminium Allow
4 Bought In
N/A
132.84
531.36 HepcoMotion
PHSS33L7800R
V Slide
Stainless Steel
4 Bought In
N/A
132.84
531.36 HepcoMotion
PHSS33L7800
V Slide
Stainless Steel
2 Bought In
N/A
60.00
120.00 HepcoMotion
AURD12833W5S
230.00
Magnetic Spa
460.00
Servomotors
A
Confirmed Motor
2 Bought In
Z Axis
A
Drive flange with
Confirmed
pinion.
2 Bought In
N/A
8.60
17.20 HepcoMotion
Z Axis
A
Confirmed Buffer unit
4 Bought In
N/A
1.03
4.12 HepcoMotion
Z Axis
A
Confirmed Bearings for Carriage
8 Bought In
N/A
3.00
24.00 HepcoMotion
Total Cost
Notes
Stainless Steel
X005
Track for printer to run
Confirmed
along.
1 Bought In
Rack Driven
Carriage Plate
HTQ Series
Torque Motor
HTQ Series
Torque Motor
Drive Flange
Assembly
Material Type
£45,000
197
Rack Driven
Carriage Plate
HTQ 300 M TEWC HTQ Series
AF
Torque Motor
Drive Flange
SSHDF50S24
Assembly
BU33W
Buffer Unit
BHJR128CNS17
Bearings
Stainless Steel
Various
Stainless Steel
Aluminium with
rubber ends.
Steel
17kW
MDDP – Megascale 3D Printing
BPP001
BPP002
Robotic Arm
Cherry Picker
Building Part
Placement
Building Part
Placement
Group 2
A
Confirmed Robotic Arm
1 Bought In
£15,000.00
98
A
Cherry Picker crane to
Confirmed assist with
construction
1 Bought In
£25,000.00
1700
1700 Hinowa
2.149
2.149
Total Cost
N001
Nozzle Disc
Nozzle
A
N002
Steel Nozzle Discs
Nozzle
A
N003
Spur Gear
Nozzle
A
N004
Bearing
Nozzle
A
N005
Screw Driven Carriage
Nozzle
A
N006
Screw Driven Linear
Motion System
Nozzle
A
N007
N008
Motor to Drive Screw
Nozzle
Driven Carriage
Motor to Rotate Nozzle
Nozzle
Disc
Aluminium disc with
Confirmed nozzles and shaft
included
Flat steel plates to
Confirmed attach to the nozzole
disc
Confirmed Gear
1
£30.00
£5.00
0.1
£12.44
0.045
Confirmed Thrust bearing
Carriage to mount
Confirmed
nozzle disc on
System to move
Confirmed carriage vertically up
and down
1 Bought In
£7.76
0.028
A
A
Electromagnet
Nozzle
A
N010
Valve
Nozzle
A
N011
Tube between Valve
and Nozzle
Nozzle
A
IRB140
Industrial Robot
Various
Gold Lift 14.70
Various
£16,700.00
2 Bought In
N009
98 ABB
4
Aluminium
0.4
Steel
0.09 HPC Gears
G 1.5-18
0.028 NSK
Steel
51200
Steel
1 Bought In
0.54
0.54 Rexroth
SGK 12-85
Aluminium
1 Bought In
1.25
1.25 Rexroth
SGK 12-85
Aluminium
Confirmed Motor
1 Bought In
1.3
1.3 IndraDyn
MSM 031B-0300
Steel
Confirmed Motor
1 Bought In
£28.00
0.2
0.2 Nanotec
ST2818M1006
Steel
2 Bought In
£150.00
1.5
3 Solentec
SM9040
Steel
1 Bought In
£2,900.00
45
45
JMPF150CFAK4A
Carbon Steel
£5.00
0.21
0.21
JMPF150CFAK4A
Carbon Steel
Electromagnets to
Confirmed support nozzle disc
when in operation
Valve to control
Confirmed different concrete
flows
Tube to connect valve
Confirmed
to nozzle
1 Bought In
Assured
Automation
1 Bought In
£3,138.20
£90.00
Microsoft
Total Cost
E001
Motion detector
Electronics
A
Confirmed Kinect
E002
Position sensor
Electronics
A
Confirmed
Incremental Position
Sensor
3 Bought In
£4,663.11
Autonics
E003
Temperature sensor
Electronics
A
Confirmed
Digital Temperature
Sensor
6 Bought In
£11.19
Maxim IC
Electromagnetic
Sensor
£2,061.76 3.1 kg
E004
Flow sensor
Electronics
A
Confirmed
2 Bought In
E005
Current sensor
Electronics
A
Confirmed Current Sensor
1 Bought In
£186.92
E006
Accelerometer
Electronics
A
Confirmed Accelerometer
1 Bought In
E006
Generator
Electronics
A
Confirmed Power Generator
1 Hired
Global Water
FM500
LEM
DHR 300 C420
£3.06
ST
LIS302DL
£314.00
Stuart Power ltd
£7,326.98
Total Cost
198
3.1 kg
Rotary
E40H8-100-3-N- EncoderR,
24
Incremental
E40 series
Programmable
Resolution 1DS18B20
Wire Digital
Thermometer
NEMA 4X
(IP66), powder
Ultrasonic flow coated
meters
aluminum,
stainless steel
hardware
AC/DC curent
transducer
MEMS motion
sensor
MDDP – Megascale 3D Printing
Group 2
T 101
FS Binder Tank
Concrete Mixing A
T 102
FS Sand Tank
Concrete Mixing A
T 105
FS Polypropylene
Tank
FS Superplasticiser
Tank
FS Retarder Tank
M 101
FS Continuous Mixer
Concrete Mixing A
P 101
FS Line Pump
Concrete
Pumping
T 201
SS Binder Tank
Concrete Mixing A
T 202
SS Sand Tank
Concrete Mixing A
T 103
T 104
Concrete Mixing A
Concrete Mixing A
Concrete Mixing A
A
T 205
SS Polypropylene
Tank
SS Superplasticiser
Tank
SS Retarder Tank
M 201
SS Continuous Mixer
Concrete Mixing A
P 201
SS Line Pump
Concrete
Pumping
T 203
T 204
Concrete Mixing A
Concrete Mixing A
Concrete Mixing A
A
Confirmed Stores the binder mix
Stores the sand
Confirmed
aggregate
Stores the
Confirmed
polypropylene fibres
Stores the
Confirmed
superplasticiser
Confirmed Stores the binder mix
Mixes the concrete
Confirmed
constituents
Confirmed
Pumps the fresh
concrete to the printer
Confirmed Stores the binder mix
Stores the sand
Confirmed
aggregate
Stores the
Confirmed
polypropylene fibres
Stores the
Confirmed
superplasticiser
Confirmed Stores the binder mix
Mixes the concrete
Confirmed
constituents
Confirmed
Pumps the fresh
concrete to the printer
1 Bought in
£24,000.00 N/A
N/A
Carbon steel
1 Bought in
£21,500.00 N/A
N/A
Carbon steel
1 Bought in
£650.00 N/A
N/A
PVC
1 Bought in
£2,000.00 N/A
N/A
PVC
1 Bought in
£950.00 N/A
N/A
PVC
1 Bought in
£2,700.00 N/A
N/A
Carbon steel
1 Bought in
£1,300.00 N/A
N/A
Carbon steel
1 Bought in
£24,000.00 N/A
N/A
Carbon steel
1 Bought in
£21,500.00 N/A
N/A
Carbon steel
1 Bought in
£950.00 N/A
N/A
PVC
1 Bought in
£3,350.00 N/A
N/A
PVC
1 Bought in
£1,900.00 N/A
N/A
PVC
1 Bought in
£3,200.00 N/A
N/A
Carbon steel
1 Bought in
£3,800.00 N/A
N/A
Carbon steel
Total Cost
£58,700.00
199
0.079kW
Will need refilling
during the print
0.78kW
MDDP – Megascale 3D Printing
Group 2
26 APPENDIX 8 – RISK ASSESSMENT TABLES
26.1 HAZOP Tables
Line/Equipment: Concrete Pump and Piping Network
PROPERTY
FLOW
GUIDE
WORD
NO
MORE
CAUSE(S)
CONSEQUENCE(S)






Pipe blockage
Pump damage
Pipe rupture
Double valve failure
Power failure
Concrete set in pipe



Pump malfunction
Programming error




LESS






Pump malfunction
Programming error
Pipe leak/rupture
Pipe partially blocked
Faulty ball valve i.e.
only one ball valve is
operational
thus
halving the flow-rate
Faulty surge chamber




Printer head does
not receive any
concrete
Concrete build-up in
the
mixer
thus
increasing residence
time
Printer head receives
excessive amounts
of concrete
Malformed structure
Decreased concrete
residence time in the
mixer
Printer head receives
insufficient concrete
Flow of concrete is
intermittent
Malformed structure
Concrete build-up in
the mixture thus
increasing residence
time
200
EXISTING
SAFEGUARD(S)
 Use of primer to reduce
friction on pipe surface
 Spare pump on-site
 Spare valve on-site
 Alternative power supply
 Ensure sufficient flowrate to prevent concrete
setting in pipe
 High level alarm in
concrete mixer
 Pressure indicators in
piping system
 High level indicators
monitoring the structure
 Low level alarm in
concrete mixer






Pressure indicators in
piping system
Use of primer to reduce
friction on pipe surface
Spare pump on-site
Spare valve on-site
Use of primer to reduce
friction on pipe surface
High level alarm in
concrete mixer
ACTION(S)






Stop process and refit pipe
Switch to spare pump
Replace valve
Repair generator
Clear pipe of set concrete
Stop feed of materials into
the concrete mixers

Correct
flow-rate
by
adjusting pump speed
Stop printing if necessary
Manually correct structure
Correct programming error
Restore normal mixer volume
by increased feed-rates of
materials
Correct
flow-rate
by
adjusting pump speed
Correct programming error
Stop printing and clear/refit
pipe
Manually correct structure
Replace valve
Stop feed of materials into
the concrete mixers until
normal volume is restored










ACTION
BY
 Site
engineer




Site
engineer
Software
engineer
Site
engineer
Software
engineer
MDDP – Megascale 3D Printing
Group 2
Line/Equipment: Concrete Pump and Piping Network
PROPERTY
PRESSURE
GUIDE
WORD
MORE
CAUSE(S)
CONSEQUENCE(S)




Pump malfunction
Programming error
Pipe blockage



Printer
head
receives
excessive
amounts
of
concrete
Malformed structure due to
excessive
amount
of
concrete
Decreased
concrete
residence time in the mixer
Potential pipe rupture
EXISTING
SAFEGUARD(S)
 Pressure indicators in
piping system
 High level indicators
monitoring the structure
 Low level alarm in
concrete mixer will
detect fall in concrete
volume
ACTION(S)
ACTION BY








LESS





Pump failure
Pump damage
Power failure
Faulty ball valve i.e.
only one ball valve
is operational thus
halving the flow-rate
Faulty
surge
chamber





Printer
head
receives
insufficient concrete
Flow of concrete is
intermittent
Malformed structure due to
insufficient concrete
Printer head does not
receive any concrete
Concrete build-up in the
mixer therefore increased
residence time
201





Pressure indicators in
piping system
Spare pump on-site
Spare valve on-site
Use of primer to reduce
friction on pipe surface
High level alarm in
concrete mixer will
detect
increased
concrete volume






Stop process if necessary
Correct flow-rate by
adjusting pump speed
Stop printing if necessary
Manually
correct
structure
Correct
programming
error
Clear pipe blockage and
repair pipe if necessary
Adjust feed-rates to the
mixer
Correct flow-rate by
adjusting pump speed
Correct
programming
error
Stop
printing
and
clear/refit pipe
Manually
correct
structure
Replace valve
Adjust feed-rates to the
mixer



Site
engineer
Software
engineer
Site
engineer
Software
engineer
MDDP – Megascale 3D Printing
Group 2
Line/Equipment: Water Feed to Concrete Mixers
PROPERTY
FLOW
GUIDE
WORD
NO
CAUSE(S)
CONSEQUENCE(S)





Programming error
Pipe rupture
Flow control valve
malfunction
Utility malfunction



MORE


Programming error
Flow control valve
malfunction



LESS




Programming error
Pipe leak/rupture
Flow control valve
malfunction
Utility malfunction




Concrete
in
mixer
gradually becomes less
workable.
Gradual drop in level of
concrete in mixer
Could lead to pipe
blockage/pump damage
if ignored
Decrease in concrete
setting time
Concrete
in
mixer
gradually becomes more
workable.
Gradual increase in
level of concrete in
mixer
Increase in concrete
setting time
Concrete
in
mixer
gradually becomes less
workable.
Gradual drop in level of
concrete in mixer
Could lead to pipe
blockage/pump damage
if ignored
Decrease in concrete
setting time
202
EXISTING
SAFEGUARD(S)
 Moisture sensor in mixer
monitoring w/b ratio
 Low level alarm in
concrete mixer will detect
fall in concrete volume
 Spare piping and control
valve on-site to replace
faulty equipment in the
event of a failure






Moisture sensor in mixer
monitoring w/b ratio
High level alarm in
concrete mixer will detect
rise in concrete volume
Spare control valve onsite
Moisture sensor in mixer
monitoring w/b ratio
Low level alarm in
concrete mixer will detect
fall in concrete volume
Spare piping and control
valve on-site to replace
faulty equipment in the
event of a failure
ACTION(S)
ACTION BY


Correct programming error
Stop feeding solid materials
into mixer temporarily until
water flow and the correct
w/b ratio are restored
Stop
pumping/printing
concrete temporarily
Replace faulty valve and/or
damaged piping

Correct programming error
Stop water flow into mixer
temporarily until sufficient
solid material has been
added to restore correct w/b
ratio
Stop
pumping/printing
concrete temporarily
Replace faulty valve
Correct programming error
Stop feeding solid materials
into mixer temporarily until
water flow and the correct
w/b ratio are restored
Stop
pumping/printing
concrete temporarily
Replace faulty valve and/or
damaged piping















Site
engineer
Software
engineer
Site
engineer
Software
engineer
Site
engineer
Software
engineer
MDDP – Megascale 3D Printing
Group 2
Line/Equipment: Amount of Concrete in Mixers
PROPERTY
VOLUME
GUIDE
WORD
MORE
CAUSE(S)
CONSEQUENCE(S)





LESS




Increased feed-rate of
water, sand, binder
and/or admixtures
Pump
malfunction
decreasing
pump
speed
Faulty ball valve(s)
Concrete blockage at
mixer exit
Programming error
Decreased feed-rate of
water, sand, binder
and/or admixtures
Pump
malfunction
increasing pump speed
Programming error






Increased concrete volume
means an increase in concrete
residence time
Increased residence time
leads more hydration in
concrete before printing
Greater hydration causes
decreased workability
Increases risk of pipe
blockage
Decreased concrete volume
means a lower concrete
residence time
Lower residence time means
less hydration in concrete
before printing
Less
hydration
causes
increased setting times and
decreased buildability
203
EXISTING
SAFEGUARD(S)
 High level alarm alerts
the control scheme of
the increased concrete
volume in mixer
 Spare pump, ball
valve(s) and piping
on-site to replace
faulty equipment


Low level alarm alerts
the control scheme of
the decreased concrete
volume in mixer
Spare pump on-site to
replace faulty pump
ACTION(S)
ACTION BY

Temporarily
stop
feeding materials into
the mixer until normal
volume is retained
Stop pumping/printing
so faulty equipment can
be replaced
Correct programming
error

Temporarily
stop
pumping/printing
but
continue feeding in
materials until normal
concrete volume is
retained in mixer
Stop pumping/printing
so faulty pump can be
replaced if necessary
Correct programming
error








Site
engineer
Software
engineer
Site
engineer
Software
engineer
MDDP – Megascale 3D Printing
Group 2
26.2 Failure Mode Effects Analysis
26.2.1 FMEA Ratings
26.2.1.1 Occurrence Rating
Value Assigned
Occurrence of Failure
1
2
3
4
5
6
7
8
9
10
1 in 1500000
1 in 150000
1 in 15000
1 in 2000
1 in 400
1 in 80
1 in 20
1 in 8
1 in 3
1 in 2
26.2.1.2 Severity Rating
Value Assigned
Severity of Failure
1
2
3
4
5
6
7
8
9
10
No effect
Defect noticed by discriminating customers
Defect noticed by average customers
Defect noticed by most customers
Secondary functionality operable at reduced performance level
Secondary functionality unavailable
Primary functionality operable at reduced performance level
Primary functionality unavailable
Failure would endanger customer, machine or operator with a warning
Failure would endanger customer, machine or operator without warning
204
MDDP – Megascale 3D Printing
Group 2
26.2.1.3 Detection Rating
Value Assigned
Severity of Failure
1
2
3
4
5
6
7
8
9
10
Current controls certain to detect/ prevent failure mode
Current controls almost certain to detect/ prevent failure mode
Very high likelihood current controls detect/ prevent the failure mode
High likelihood current controls will detect/ prevent failure mode
Moderately high likelihood current controls will detect/ prevent failure mode
Low likelihood current controls will detect/ prevent failure mode
Very low likelihood current controls will detect/ prevent failure mode
Remote likelihood current controls will detect/ prevent failure mode
Very remote likelihood current controls will detect/ prevent failure mode
Current controls will not detect/ prevent failure mode
205
MDDP – Megascale 3D Printing
Group 2
26.2.2 FMEA Tables
Product: 3D Printer
Component Name: N/A
Component Number: N/A
Revision Number: 1
Effect on Purchasing: Yes/No
Part
Part
Function
Number
X-Axis Beam
X001
Supports robotic arm
and nozzle
V-Slide with
Teeth
X002
V-Slide without X003
Teeth
Carriage Plate
X004
Motors
X005 /
X006
Possible Failure Mode
Effects of Failure
Failure Cause
Action to Reduce or Eliminate Risk
Fatigue
Corrosion
Beam fractures
Weakened beam
Stop use once expected lifetime is reached
Apply effective weather protection
1
1
9
8
8
3
72
24
Motor operates at resonance
frequency of beam
Incorrect mounting to carriage
Beam fracture
Over-use
Inadequate weather
protection
Resonance
2
9
3
54
Beam falls
Human error
Perform vibrational analysis to deduce
frequncies which the motor should not run at
Perform checks after assembly
1
10
1
10
Carriages will not
move
Weakened teeth
Over-use
Lubricate
1
8
7
56
Apply effective weather protection
1
6
3
18
Perform checks after assembly
None
None
Apply effective weather protection
1
1
1
1
7
8
8
6
1
3
1
3
7
24
8
18
None
Apply effective weather protection
1
1
8
8
1
3
8
24
Stop use once expected lifetime is reached
Perform load analysis
Provide temperature control
Current check
Perform altitude analysis
Provide temperature control
Current check (under-voltage will increase
current)
Voltage check
Electronic filter
Seal motor
Temperature Control
1
2
1
1
1
1
1
7
6
6
6
6
6
6
8
5
1
5
1
1
5
56
60
6
30
6
6
30
1
1
1
1
6
6
5
5
5
6
1
1
30
36
5
5
1
6
4
24
1
1
6
6
1
3
6
18
Ensure motor is lubricated correctly
1
6
3
18
Ensure motor is lubricated correctly
1
6
4
24
Track for bearings and Wear of teeth
pinion to run along
Corrosion
Track for bearings to
run along
Developer: MDDP 3D Printing Group 2
Report Number: 1
Sheet of Sheets: 1 of 6
Revision Number: 1
Last Updated: 06/01/13
O
S
D
R
Incorrect fixing to beam
Incorrect dimensions of teeth
Misallignment to beam
Corrosion
Misallignment to beam
Rack driven carriage
Corrosion
plate for robotic arm
and nozzle mounting Fatigue
Motor to move robotic Heat
arm and nozzle
carriages
Power supply anomalies
Humidity
Contamination
Improper lubrication
Inadequate weather
protection
Slide detaches
Human error
No movement
Manufacturer error
No movement
Manufacturer error
Weakened slide
Inadequate weather
protection
No movement
Manufacturer error
Weakened carriage Inadequate weather
protection
Carriage fracture
Over-use
Electrical insulation Mechanical overloading
deteriorates
High ambient temperature
Circuit failure
Low or unbalanced voltages
High altitude operation
Inadequate ventilation
Overheating
Run Incorrect voltage
at incorrect speeds
Voltage Unbalance
Harmonics
Short Circuit
Water contamination
Corrosion of bearings
Corrosion
Overheating
Short Circuit
Reaction between
Seal motor
contaminate and motor
parts
Obstruction of ventilation
Temperature sensor
Contaminate bridges circuit Seal motor
Potential for gears to Over lubrication
slip
Create large friction Under lubrication
between parts
206
MDDP – Megascale 3D Printing
Product: 3D Printer
Component Name: N/A
Component Number: N/A
Revision Number: 1
Effect on Purchasing: Yes/No
Part
Part
Function
Number
Drive Flange
X007
Move carriage
with Pinion
Group 2
Possible Failure Mode
Effects of Failure
Failure Cause
Action to Reduce or Eliminate Risk
Corrosion
Drive flange or pinion
fracture
Carriages will not
move
No movement
Rubber deteriorates
Inadequate weather
protection
Over-use
Apply effective weather protection
1
8
3
24
Lubricate
1
8
7
56
Manufacturer error
Inadequate weather
protection
Inadequate weather
protection
Over-use
Excessive force
Over-use
None
Apply effective weather protection
1
1
8
3
3
2
24
6
Apply effective weather protection
1
8
3
24
Stop use once expected lifetime is reached
Never exceed predicted loadings
Lubricate
1
1
1
7
7
8
7
4
7
49
28
56
Apply effective weather protection
1
6
3
18
Perform checks after assembly
None
None
Apply effective weather protection
1
1
1
1
7
8
8
6
1
3
1
3
7
24
8
18
None
Apply effective weather protection
1
1
8
8
1
3
8
24
Stop use once expected lifetime is reached
Perform load analysis
Provide temperature control
Current check
Perform altitude analysis
Provide temperature control
Current check (under-voltage will increase
current)
Voltage check
Electronic filter
Seal motor
Temperature Control
1
2
1
1
1
1
1
7
6
6
6
6
6
6
8
5
1
5
1
1
5
56
60
6
30
6
6
30
1
1
1
1
6
6
5
5
5
6
1
1
30
36
5
5
1
6
4
24
1
1
6
6
1
3
6
18
Wear of teeth
Buffer
X008
Bearings
X009
Flat Track with Y001
teeth.
Incorrect dimensions of teeth
Prevent carriage
Corrosion
hitting end of beam
Allows smooth
Corrosion
movement of carriage
Fatigue
Ball bearings break
Track for bearings
Wear of teeth
blocks to run along
Corrosion
Flat track
Y002
without teeth.
Track for bearings
blocks to run along
Carriage Plate
Y003
Rack driven carriage
plate for Z001 beam
Motor
Y004
Motor to move X-axis
and Z-axis
Developer: MDDP 3D Printing Group 2
Report Number: 1
Sheet of Sheets: 2 of 6
Revision Number: 1
Last Updated: 06/01/13
O
S
D
R
Incorrect fixing to beam
Incorrect dimensions of teeth
Misallignment to beam
Corrosion
Misallignment to beam
Corrosion
Fatigue
Heat
Power supply anomalies
Humidity
Contamination
Weakened bearings
Bearing fracture
No movement
Carriages will not
move
Weakened teeth
Inadequate weather
protection
Slide detaches
Human error
No movement
Manufacturer error
No movement
Manufacturer error
Weakened slide
Inadequate weather
protection
No movement
Manufacturer error
Weakened carriage Inadequate weather
protection
Carriage fracture
Over-use
Electrical insulation Mechanical overloading
deteriorates
High ambient temperature
Circuit failure
Low or unbalanced voltages
High altitude operation
Inadequate ventilation
Overheating
Run Incorrect voltage
at incorrect speeds
Voltage Unbalance
Harmonics
Short Circuit
Water contamination
Corrosion of bearings
Corrosion
Overheating
Short Circuit
Reaction between
Seal motor
contaminate and motor
parts
Obstruction of ventilation
Temperature sensor
Contaminate bridges circuit Seal motor
207
MDDP – Megascale 3D Printing
Product: 3D Printer
Component Name: N/A
Component Number: N/A
Revision Number: 1
Effect on Purchasing: Yes/No
Part
Part
Function
Number
Bearing block
Drive flange
with pinion.
Y005 /
Y006
Y007
Group 2
Possible Failure Mode
Effects of Failure
Improper lubrication
Potential for gears to Over lubrication
slip
Create large friction Under lubrication
between parts
Weakened bearings Inadequate weather
protection
Bearing fracture
Over-use
No movement
Excessive force
Drive flange or pinion Inadequate weather
fracture
protection
Carriages will not
Over-use
move
No movement
Manufacturer error
Beam fractures
Over-use
Weakened beam
Inadequate weather
protection
Beam fracture
Resonance
Allows smooth
Corrosion
movement of carriage
Fatigue
Ball bearings break
Move carriage
Corrosion
Wear of teeth
Mounting Plate Y008
Z-Axis Beam
V-Slide with
Teeth
Z001
Z002
Incorrect dimensions of teeth
Supports X-axis and Z- Fatigue
axis
Corrosion
Supports X-axis
Motor operates at resonance
frequency of beam
Incorrect mounting to carriage
Track for bearings and Wear of teeth
pinion to run along
Corrosion
V-Slide without Z003
Teeth
Track for bearings to
run along
Carriage Plate
Rack driven carriage
plate for X001 beam
Z004
Motor operates at resonance
frequency of beam
Incorrect mounting to carriage
Fatigue
Corrosion
Failure Cause
Beam falls
Beam fractures
Weakened beam
Human error
Over-use
Inadequate weather
protection
Resonance
Beam fracture
Beam falls
Carriages will not
move
Weakened teeth
Human error
Over-use
Incorrect fixing to beam
Incorrect dimensions of teeth
Misallignment to beam
Corrosion
Slide detaches
No movement
No movement
Weakened slide
Misallignment to beam
Corrosion
No movement
Weakened carriage
Fatigue
Carriage fracture
Inadequate weather
protection
Human error
Manufacturer error
Manufacturer error
Inadequate weather
protection
Manufacturer error
Inadequate weather
protection
Over-use
208
Action to Reduce or Eliminate Risk
Developer: MDDP 3D Printing Group 2
Report Number: 1
Sheet of Sheets: 3 of 6
Revision Number: 1
Last Updated: 06/01/13
O
S
D
R
Ensure motor is lubricated correctly
1
6
3
18
Ensure motor is lubricated correctly
1
6
4
24
Apply effective weather protection
1
8
3
24
Stop use once expected lifetime is reached
Never exceed predicted loadings
Apply effective weather protection
1
1
1
7
7
8
7
4
3
49
28
24
Lubricate
1
8
7
56
None
Stop use once expected lifetime is reached
Apply effective weather protection
1
1
1
8
9
8
3
8
3
24
72
24
Perform vibrational analysis to deduce
frequncies which the motor should not run at
Perform checks after assembly
Stop use once expected lifetime is reached
Apply effective weather protection
2
9
3
54
1
1
1
10
9
8
1
8
3
10
72
24
Perform vibrational analysis to deduce
frequncies which the motor should not run at
Perform checks after assembly
Lubricate
2
9
3
54
1
1
10
8
1
7
10
56
Apply effective weather protection
1
6
3
18
Perform checks after assembly
None
None
Apply effective weather protection
1
1
1
1
7
8
8
6
1
3
1
3
7
24
8
18
None
Apply effective weather protection
1
1
8
8
1
3
8
24
Stop use once expected lifetime is reached
1
7
8
56
MDDP – Megascale 3D Printing
Product: 3D Printer
Component Name: N/A
Component Number: N/A
Revision Number: 1
Effect on Purchasing: Yes/No
Part
Part
Function
Number
Motor
Z005
Motor to move X-axis
Group 2
Possible Failure Mode
Effects of Failure
Heat
Electrical insulation
deteriorates
Circuit failure
Power supply anomalies
Humidity
Contamination
Improper lubrication
Drive Flange
with Pinion
Z006
Move carriage
Corrosion
Wear of teeth
Buffer
Z007
Bearings
Z008
Nozzle Disc
N001
Incorrect dimensions of teeth
Prevent carriage
Corrosion
hitting end of beam
Allows smooth
Corrosion
movement of carriage
Fatigue
Ball bearings break
Rotates to change
Corrosion
nozzle
Fatigue
Nozzle blockage
Failure Cause
Mechanical overloading
High ambient temperature
Low or unbalanced voltages
High altitude operation
Inadequate ventilation
Overheating
Run Incorrect voltage
at incorrect speeds
Voltage Unbalance
Harmonics
Short Circuit
Water contamination
Corrosion of bearings
Action to Reduce or Eliminate Risk
Perform load analysis
Provide temperature control
Current check
Perform altitude analysis
Provide temperature control
Current check (under-voltage will increase
current)
Voltage check
Electronic filter
Seal motor
Temperature Control
Developer: MDDP 3D Printing Group 2
Report Number: 1
Sheet of Sheets: 4 of 6
Revision Number: 1
Last Updated: 06/01/13
O
S
D
R
2
1
1
1
1
1
6
6
6
6
6
6
5
1
5
1
1
5
60
6
30
6
6
30
1
1
1
1
6
6
5
5
5
6
1
1
30
36
5
5
Corrosion
Overheating
Short Circuit
Reaction between
Seal motor
contaminate and motor
Obstruction of ventilation Temperature sensor
Contaminate bridges circuit Seal motor
1
6
4
24
1
1
6
6
1
3
6
18
Potential for gears to
slip
Create large friction
between parts
Drive flange or pinion
fracture
Carriages will not
move
No movement
Rubber deteriorates
Over lubrication
Ensure motor is lubricated correctly
1
6
3
18
Under lubrication
Ensure motor is lubricated correctly
1
6
4
24
Inadequate weather
protection
Over-use
Apply effective weather protection
1
8
3
24
Lubricate
1
8
7
56
Manufacturer error
Inadequate weather
protection
Inadequate weather
protection
Over-use
Excessive force
Inadequate weather
protection
Over-use
Concrete sets too quickly
Contaminants in concrete
None
Apply effective weather protection
1
1
8
3
3
2
24
6
Apply effective weather protection
1
8
3
24
Stop use once expected lifetime is reached
Never exceed predicted loadings
Apply effective weather protection
1
1
1
7
7
6
7
4
1
49
28
6
Stop use once expected lifetime is reached
Print at correct speed
Provide protection
1
1
1
6
6
6
4
1
3
24
6
18
Weakened bearings
Bearing fracture
No movement
Weakened disc
Disc fracture
No concrete flow
209
MDDP – Megascale 3D Printing
Product: 3D Printer
Component Name: N/A
Component Number: N/A
Revision Number: 1
Effect on Purchasing: Yes/No
Part
Part
Function
Number
Steel Nozzle
N002
Attach nozzle disc to
Discs
electromagnet
Group 2
Possible Failure Mode
Effects of Failure
Corrosion
Weakened discs
Detach from N001
Spur Gear
Bearing
N003
N004
Translate motion from Corrosion
motor to nozzle disc
Wear of teeth
Incorrect dimensions of teeth
Rotates nozzle disc
Corrosion
Fatigue
Ball bearings break
Screw Driven
Carriage
N005
Carriage to mount
nozzle disc on
Screw Driven
Linear Motion
System
N006
System to move
carriage vertically up
and down
Motor
N007
Motor to Drive Screw
Driven Carriage
Corrosion
Fatigue
Wear of screw
Corrosion
Fatigue
Heat
Power supply anomalies
Humidity
Contamination
Improper lubrication
Failure Cause
Action to Reduce or Eliminate Risk
Developer: MDDP 3D Printing Group 2
Report Number: 1
Sheet of Sheets: 5 of 6
Revision Number: 1
Last Updated: 06/01/13
O
S
D
R
Inadequate weather
protection
Weakened fastening Excessive force
Apply effective weather protection
1
6
1
6
Check fastening before print
1
7
3
21
Gear failure
Inadequate weather
protection
Over-use
Manufacturer error
Inadequate weather
protection
Over-use
Excessive force
Apply effective weather protection
1
6
2
12
Lubricate
None
Apply effective weather protection
1
1
1
5
6
8
2
2
3
10
12
24
Stop use once expected lifetime is reached
Never exceed predicted loadings
1
1
7
7
7
4
49
28
Inadequate weather
protection
Over-use
Over-use
Apply effective weather protection
1
8
3
24
Stop use once expected lifetime is reached
Lubricate
1
1
7
5
8
2
56
10
Apply effective weather protection
1
8
3
24
Stop use once expected lifetime is reached
Perform load analysis
Provide temperature control
Current check
Perform altitude analysis
Provide temperature control
Current check (under-voltage will increase
current)
Voltage check
Electronic filter
Seal motor
Temperature Control
1
2
1
1
1
1
1
7
6
6
6
6
6
6
8
5
1
5
1
1
5
56
60
6
30
6
6
30
1
1
1
1
6
6
5
5
5
6
1
1
30
36
5
5
1
6
4
24
1
1
6
6
1
3
6
18
Ensure motor is lubricated correctly
1
6
3
18
Ensure motor is lubricated correctly
1
6
4
24
N001 will not rotate
No movement
Weakened bearings
Bearing fracture
No rotational
movement
Weakened carriage
Carriage fracture
No vertical
movement
Weakened carriage
Inadequate weather
protection
Carriage fracture
Over-use
Electrical insulation Mechanical overloading
deteriorates
High ambient temperature
Circuit failure
Low or unbalanced voltages
High altitude operation
Inadequate ventilation
Overheating
Run Incorrect voltage
at incorrect speeds
Voltage Unbalance
Harmonics
Short Circuit
Water contamination
Corrosion of bearings
Corrosion
Overheating
Short Circuit
Reaction between
Seal motor
contaminate and motor
Obstruction of ventilation
Temperature sensor
Contaminate bridges circuit Seal motor
Potential for gears to Over lubrication
slip
Create large friction Under lubrication
between parts
210
MDDP – Megascale 3D Printing
Product: 3D Printer
Component Name: N/A
Component Number: N/A
Revision Number: 1
Effect on Purchasing: Yes/No
Part
Part
Function
Number
Motor
N008
Motor to Rotate
Nozzle Disc
Group 2
Possible Failure Mode
Effects of Failure
Failure Cause
Heat
Electrical insulation
deteriorates
Circuit failure
Mechanical overloading
Perform load analysis
High ambient temperature Provide temperature control
Low or unbalanced voltages Current check
Power supply anomalies
Humidity
Contamination
Improper lubrication
Electromagnet N009
Valve
Tube
N010
N011
Electromagnets to
support nozzle disc
when in operation
Demagnetisation
Valve to control
different concrete
flows
Blockage
Fails to select correct concrete
flow
Tube to connect valve Blockage
to nozzle
Action to Reduce or Eliminate Risk
Developer: MDDP 3D Printing Group 2
Report Number: 1
Sheet of Sheets: 6 of 6
Revision Number: 1
Last Updated: 06/01/13
O
S
D
R
2
1
1
6
6
6
5
1
5
60
6
30
High altitude operation
Inadequate ventilation
Overheating
Run Incorrect voltage
at incorrect speeds
Voltage Unbalance
Harmonics
Short Circuit
Water contamination
Corrosion of bearings
Corrosion
Reaction between
Overheating
contaminate and motor
Short Circuit
Obstruction of ventilation
Contaminate bridges circuit
Perform altitude analysis
Provide temperature control
Current check (under-voltage will increase
current)
Voltage check
Electronic filter
Seal motor
Temperature Control
Seal motor
1
1
1
6
6
6
1
1
5
6
6
30
1
1
1
1
1
6
6
5
5
6
5
6
1
1
4
30
36
5
5
24
Temperature sensor
Seal motor
1
1
6
6
1
3
6
18
Potential for gears to Over lubrication
slip
Create large friction Under lubrication
between parts
N001 is not
Incorrect voltage
supported
Voltage Unbalance
Harmonics
No concrete flow
Concrete sets too quickly
Contaminants in concrete
Incorrect concrete
Motor failure
flow
No concrete flow
Concrete sets too quickly
Contaminants in concrete
Ensure motor is lubricated correctly
1
6
3
18
Ensure motor is lubricated correctly
1
6
4
24
Current check (under-voltage will increase
current)
Voltage check
Electronic filter
Print at correct speed
Provide protection
Implement adequate control techniques
1
6
5
30
1
1
1
1
2
6
6
6
6
5
5
6
1
3
4
30
36
6
18
40
Print at correct speed
Provide protection
1
1
6
6
1
3
6
18
211
MDDP – Megascale 3D Printing
Group 2
26.3 Site Health and Safety Analysis
212
MDDP – Megascale 3D Printing
Group 2
213
MDDP – Megascale 3D Printing
Group 2
214
MDDP – Megascale 3D Printing
Group 2
27 APPENDIX 9 – PROJECT MANAGEMENT
27.1 Initial Gantt Chart
215
MDDP – Megascale 3D Printing
Group 2
27.2 Final Task List
Task
#
Task Name
Duration
Predecessors
Resource Names
1
A.1 - Research on Existing Printing
Techniques
6 days
Hinde Taleb, James
Airey, Sam Thorley, Deep Upendra,
Sam Tomlinson,
Simon Nicholls
2
A.2 - Available Materials - Pros and Cons
6 days
Simon Nicholls,
Sam Thorley, Deep
Upendra
3
A.3 - Basic Idea of Cost
2 days
Hinde Taleb
4
A.4 - Initial Project
Management
4 days
Sam Tomlinson,
James Airey
5
A.5 - Inception Report
Checking
1 day
1,2,3,4
6
B.1 - Primary Material
Research
7 days
1,2,4
Sam Thorley, Hinde Taleb, Simon
Nicholls
7
B.2 - Secondary Material Research
4 days
1,2,4
Sam Thorley, Hinde Taleb, Simon
Nicholls
8
B.3 - Support Materials
Research
10 days
1,2,4
James Airey, Sam
Tomlinson, Deep
Upendra
9
C.1 - Dimensions
1 day
22,4
Deep Upendra
10
C.2 - Printer Transportation and Assembly
1 day
4
Sam Tomlinson
11
C.4 - Motors and Cabling
10 days
9,17,18,4
12
13
C.5 - Pumps and Pipes
C.6 - CAD for Printer
12 days
0 days
6,7,8,9,17,4
4,19
14
C.7 - Printer analysis
21 days
13,4
15
C.8 - Parts List
1 day
Simon Nicholls
James Airey, Hinde
Taleb
Sam Thorley
Sam Tomlinson
James Airey, Sam
Tomlinson
Sam Tomlinson,
James Airey, Hinde
11,12,19,30,31,4 Taleb, Deep Upendra, Sam Thorley,
Simon Nicholls
216
MDDP – Megascale 3D Printing
Group 2
16
C.9 -Engineering Drawings
7 days
13,4
Deep Upendra
17
18
C.10 - Power Analysis
C.11 - Nozzle Design
5 days
21 days
4
6,7,8
Hinde Taleb
James Airey
19
C.12 - Printer Structure
Design
14 days
1
20
C.13 - Concrete Mixture
20 days
Design
Sam Thorley
21
C.13 - Robotics
5 days
James Airey
22
D.1 - Foundations, reinforcement methods
10 days
4
Deep Upendra
23
D.2 - CAD for Building
5 days
22,25,4
Deep Upendra
24
D.3 - Estimation of
Concrete Required
3 days
25
D.4 - Wiring, Plumbing,
Insulation, etc
8 days
4
26
D.5 - Sustainabililty
5 days
23,28,4
Simon Nicholls,
Hinde Taleb
27
E.1 - Inherent Printing
Dificulties and Solutions
13 days
6,7,8,4
Deep Upendra
28
E.2 - Raw Material
Transportation, Storage
and Preparation
2 days
6,7,8,4
Sam Thorley
11,23,4
James Airey
29
30
E.5 - MATLAB Simula0 days
tion
F.1 - Software to Con25 days
trol Printer
Sam Tomlinson,
Simon Nicholls
Deep Upendra
Sam Thorley, Hinde Taleb
4
Hinde Taleb, Simon Nicholls
31
F.3 - Sensors for Feedback
10 days
4
Hinde Taleb, Simon Nicholls
32
G - Building Finish
0 days
4
Simon Nicholls
33
H.1 - Risk Assessment
HAZOP and FMEA
6 days
4
Deep Upendra,
Sam Thorley, Sam
Tomlinson
34
I.1 - Comparison Between Conventional
Methods and Printing,
Finance
6 days
3,4
Simon Nicholls,
Sam Tomlinson
15,4
James Airey, Sam
Tomlinson, Deep
Upendra, Hinde
Taleb, Sam Thorley, Simon
Nicholls
35
I.3 - Cost of Printer
2.5 days
217
MDDP – Megascale 3D Printing
Group 2
Simon Nicholls,
Sam Tomlinson
Deep Upendra,
Hinde Taleb, James
Airey, Sam Thorley, Sam
Tomlinson, Simon
Nicholls
Hinde Taleb, James
Airey
Deep Upendra,
Hinde Taleb, James
Airey, Sam Thorley, Sam
Tomlinson, Simon
Nicholls
36
I.4 - Cost to Print
2.5 days
10,28,4
37
J.1 - Final Report Writing
5 days
1,2,3,4
38
J.4 - Final Project Management
2 days
39
J.2 - Final Report
Checking
5 days
40
J.3 - Executive Summary
2 days
Hinde Taleb
13.33
days
Deep Upendra,
Hinde Taleb, James
Airey, Sam Thorley, Sam
Tomlinson, Simon
Nicholls
41
K - Poster and Presentation Preparation
37
4,39
218
MDDP – Megascale 3D Printing
Group 2
28 APPENDIX 10 – FLOOR PLANS
Figure 82 - House Bottom Floor Plan
219
MDDP – Megascale 3D Printing
Group 2
Figure 83 - House Second Floor Plan
220
MDDP – Megascale 3D Printing
Group 2
Figure 84 - House Elevations
221
MDDP – Megascale 3D Printing
Group 2
Figure 85 - 3D Drawing of House
222
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