KTH ROYAL INSTITUTE OF TECHNOLOGY Master Thesis in Production Engineering and Management Additive Manufacturing and Production of Metallic Parts in Automotive Industry A Case Study on Technical, Economic and Environmental Sustainability Aspects In collaboration with Alexandros Beiker Kair Konstantinos Sofos KTH supervisor: Amir Rashid Industrial supervisor: Pau Mallol Abstract Additive Manufacturing (AM) comprises a family of different technologies that build up parts by adding materials layer by layer at a time based on a digital 3D solid model. After thirty years of development, AM has become a mainstream manufacturing process with more materials and new technologies involved in this process. Undoubtedly, the most dramatic and challenging development of group of technologies has been the printing of metals. Nowadays, the use of AM for the production of parts for final products continues to grow. Organizations around the world are successfully applying the technology to the production of finished goods. AM allows design optimization and produces customized parts on-demand with almost similar material properties with the conventional manufactured parts. It does not require the use of coolants, fixtures, cutting tools and other assisting resources. The advantages of AM over conventional manufacturing can change the world of industry and lead to a new industrial revolution. In this research after reviewing mostly the different technologies and materials used in metallic AM, the application of them in a component of a passenger car engine is described. A criticality analysis is carried out in order to decide which AM development of the parts that compose the final product is more significant for the efficiency of the overall product. Based on that development a sustainability analysis is performed consisting of the analysis of the environmental impacts, the production cost analysis and the societal impact. But what has been derived from the analysis is that despite the lower environmental impact compared with the casting as a conventional method of forming of metals, AM is costly for the production of a small number of industrial products and its societal impact needs further investigation. In fact, the cost depends on the production volume, the batch size as well as the high price of the material powders and the building rates of the machines. In the future, with more advanced machines and cheaper material input the cost of metallic AM is going to drop dramatically. In spite of all the progress, the application of metallic AM is still not widespread. Since the materials as well as its technologies are still evolving, a better and more promising future is foreseen for metallic AM. Keywords: Additive Manufacturing, Direct Digital Manufacturing, Mass Production, Automotive, Internal Combustion Engine, Turbocharger, Development, Sustainability Analysis, Lifecycle Assessment 2 Sammanfattning Additive Manufacturing (AM) består av en familj av olika teknologier som bygger upp komponenter genom att lägga till material lager efter lager ett lager i taget baserat på en digital 3D solid modell. Efter trettio år av utveckling, har AM blivit en mainstream tillverkningsprocess med fler material och nya teknologier involverade i denna process. Utan tvekan har den mest dramatiska och utmanande utvecklingen inom denna grupp av teknologier varit tryckningen av metaller. Nuförtiden fortsätter användningen av AM för tillverkning av delar till slutprodukter att växa. Företag runtom i världen använder tekniken framgångsrikt för produktionen av färdiga varor. AM tillåter designoptimering och tillverkar kundanpassade delar on-demand med nästan samma materialegenskaper som konventionellt tillverkade delar. Det behövs inte användning av kylmedel, fixturer, skärverktyg och andra källor. Fördelarna med AM jämfört med konventionell tillverkning kan förändra den industriella världen och leda till en ny industriell revolution. Efter att mestadels ha gått igenom de olika tekniker och material som används i metallisk AM, beskrivs i denna forskning applikationen av dem i en komponent av motorn till en personbil. En kritikalitet analys görs för att bestämma vilken AM utveckling av de delar som utgör den slutgiltiga produkten som är viktigast för effektiviteten av den totala produktionen. Baserat på denna utveckling utförs en hållbarhetsanalys som består av en analys av miljöpåverkan, produktionskostnad och de samhälleliga effekterna. Men det som har härletts från analysen är att trots den lägre miljöpåverkan i jämförelse med gjutning som en konventionell metod för formning av metaller, är AM kostsamt för produktionen av ett fåtal industriella produkter och dess samhälleliga effekter behöver studeras ytterligare. I själva verket beror kostnaden på produktionsvolymen, satsstorleken samt det höga priset på materialpulvren och byggnadstakten av maskinerna. I framtiden, med mer avancerade maskiner och billigare material kommer kostnaden för metallisk AM att sjunka dramatiskt. Trots alla utveckling, är applikationen av metallisk AM fortfarande inte utbredd. Eftersom materialen samt dess teknik fortfarande är under utveckling förutses en bättre och mer lovande framtid för metallisk AM. Nyckelord: Additive Manufacturing, Direct Digital Manufacturing, massproduktion, bilindustrin, förbränningsmotor, Turbocharger, utveckling, hållbarhetsanalys, livscykelanalys. 3 Acknowledgments We would like to offer our special thanks to Mr. Amir Rashid and Mr. Pau Mallol who inspired us with the concept and guided us in order to complete this thesis research. We also appreciate all other people who helped us in this research path including Mr. Andreas Cronhjort, Mr. Diego Irving and Mr. Ioannis Giannatsis. Alexandros Beiker Kair wishes also to acknowledge and thank the Alexander S. Onassis Public Benefit Foundation in Greece for supporting him with a scholarship. Stockholm, June 2014 Alexandros Beiker Kair Konstantinos Sofos 4 Dedication We sincerely dedicate this thesis to our families and friends for their support. 5 List of Tables Table 1: EOSINT M 280 specifications. .................................................................................................. 21 Table 2: Renishaw AM250 specifications .............................................................................................. 22 Table 3: Arcam QA2X specifications. ..................................................................................................... 24 Table 4: MAGIC machine specifications ................................................................................................ 26 Table 6: Specifications of LaserCUSING® M2 ........................................................................................ 29 Table 7: Specifications of DPM machine M-print by ExOne.................................................................. 30 Table 8: The main components of a turbocharger. ............................................................................... 49 Table 9: Characteristics of conventional metal casting methods and AM. ........................................... 71 Table 10: Results from the survey. ........................................................................................................ 76 Table 11: Criteria value scale................................................................................................................. 77 Table 12: Ranking the need for improvement ...................................................................................... 78 Table 13: Ranking the statements of development .............................................................................. 79 Table 14: Overall selection development matrix. ................................................................................. 81 Table 15: The Eco-indicator values of the materials that were chosen for the materials used for the manufacture of the components of the turbocharger.......................................................................... 88 Table 16: The EI (in mPts) for each phase for both of manufacturing scenarios of the turbocharger. 90 Table 17: Forecast of the costs that consist the total manufacturing cost of the production of a turbocharger by AM250 with Stainless Steel 316L. .............................................................................. 95 Table 18: AM costs (SEK/cm3) ............................................................................................................... 97 Table 19: Forecast of the costs that make up the total production cost of AM250 machine that uses Stainless Steel 316L as material powder. .............................................................................................. 98 Table 20: Changes in parameters that affect the AM costs. ................................................................. 99 6 List of Figures Figure 1: MakerBot mixtape printed using FDM. .................................................................................. 17 Figure 2: How DMLS works. .................................................................................................................. 20 Figure 3: A pump manufactured by SLM ............................................................................................... 22 Figure 4: How EBM works. .................................................................................................................... 23 Figure 5: How EBDM works ................................................................................................................... 24 Figure 6: A sample of titanium parts created with Sciaky's direct manufacturing technology, which combines an electron beam welding gun with wirefeed additive layering. ......................................... 25 Figure 7: How LPF works. ..................................................................................................................... 26 Figure 8: Knee prosthesis printed by BeAM on a MAGIC machine ....................................................... 26 Figure 9: Manifold printed by BeAM on a MAGIC machine. ................................................................. 26 Figure 10: How IFF works ..................................................................................................................... 27 Figure 11: How UAM works .................................................................................................................. 28 Figure 12: Metal part produced by UAM technology. .......................................................................... 28 Figure 13: Complex geometry achieved through AM production © Pinoko ........................................ 42 Figure 14: Examples of direct metal laser sintering (DMLS) © Econolyst ............................................. 42 Figure 15: Turbocharger used for a Diesel engine by Garrett (Model No. GT 1749V) .......................... 48 Figure 16: Operation of the turbocharger system. ............................................................................... 48 Figure 17: Apparatus of the low-pressure casting method................................................................... 51 Figure 18: Apparatus of the vacuum casting method ........................................................................... 51 Figure 19: Impellers for superchargers from titanium aluminide alloys are at the same time extremely light, corrosion resistant and of high-strength...................................................................................... 55 Figure 20: An illustration showing the dimensions of a large size turbocharger series by MTU a brand of Rolls-Royce Power Systems AG. ....................................................................................................... 59 Figure 21: A comparative chart of the Ultimate Tensile Strength (UTS) of the metal alloys that have been manufactured by both Conventional Manufacturing (CM) and Additive Manufacturing (AM) and are applicable to the production of the turbocharger. ......................................................................... 62 Figure 22: High-performance turbocharger with water-cooled casing and compressor impeller developed by MTU Friedrichshafen GmbH .......................................................................................... 63 Figure 23: Turbocharger with variable turbine geometry (VTG)........................................................... 64 Figure 24: Turbocharger design with twin-entry turbines by BorgWarner .......................................... 64 Figure 25: Lists of the parameters of the objective, the criteria and the alternatives used for the criticality analysis. ................................................................................................................................. 71 7 Figure 26: Sustainability as the intersection of its three key parts, and examples of features at the intersection of any two parts. ............................................................................................................... 82 Figure 27: Triple Bottom Line graphic ................................................................................................... 83 Figure 28: General Life-Cycle Stages of a Product or System................................................................ 84 Figure 29: Original Scenario; process tree of a turbocharger with amounts and assumptions. Conventional manufacturing (casting) is used for the production of each component. The white boxes are not included in the analysis............................................................................................................. 87 Figure 30: Development Scenario; process tree of a turbocharger with amounts and assumptions. AM (SLM technology) is used for the production of the center housing. The white boxes are not included in the analysis. ....................................................................................................................................... 87 Figure 31: The share of total manufacturing cost in 2014, 2018 and 2023. ......................................... 96 8 List of Acronyms 3DP ABS AM ASTM BE CAD CNC CTE DDM DLP DMD DMLS DPM DSI EBDM EBM ECR EI FDM HAP hcp HIP ICE IFF LC LC LCA LENS Three Dimensional Printing Acrylonitrile/ Butadiene/Styrene Additive Manufacturing American Society for Testing and Materials Elongation at break Computer Aided Design Computer Numerical Control Coefficient of Thermal Expansion Direct Digital Manufacturing Digital Light Processing Direct Metal Deposition Direct Metal Laser Sintering Digital Part Materialization Delta Services Industriels Electron Beam Direct Manufacturing Electron Beam Melting Energy Consumption Rate Environmental Impact Fused Deposition Modeling Hazardous Air Pollutants hexagonal close packed microstructure Hot Isostatic Pressing Internal Combustion Engine Ion Fusion Forming Laser Consolidation Life Cycle Life Cycle Assessment Laser Engineered Net Shaping LPF MarM MFS MHI MMC MOC NOH PC PE PMMA POM PP PPSF Pt ROI RP RPM SLA SLM SLS STL TC TBL UAM UC UTS UV VTG YTS Laser Powder Forming Martin – Marietta Machines From Solid Mitsubishi Heavy Industries Metal Matrix Composite Manufacturing Overhead Cost National reuse of waste research programme Polycarbonate Polyethylene Poly(methyl methacrylate) Precision Optimal Manufacturing Polypropylene Polyphenylsulfone Point (environmental impact) Return on Investment Rapid Prototyping Rounds Per Minute Stereolithography Apparatus Selective Laser Melting Selective Laser Sintering STereoLithography (file format) Thermal Conductivity Triple Bottom Line Ultrasonic Additive Manufacturing Ultrasonic Consolidation Ultimate Tensile Strength Ultraviolet Variable Turbine Geometry Yield Tensile Strength 9 Introduction Table of Contents ABSTRACT .................................................................................. 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SAMMANFATTNING ..................................................................................................................... 3 ACKNOWLEDGMENTS................................................................................................................... 4 DEDICATION ................................................................................................................................. 5 LIST OF TABLES ............................................................................................................................. 6 LIST OF FIGURES ........................................................................................................................... 7 LIST OF ACRONYMS ...................................................................................................................... 9 TABLE OF CONTENTS .................................................................................................................. 10 1 2 INTRODUCTION................................................................................................................... 12 1.1 DEFINITION OF CONCEPT ............................................................................................................. 12 1.2 PROBLEM DEFINITION ................................................................................................................. 14 1.3 RESEARCH SCOPE AND BOUNDARIES .............................................................................................. 14 1.4 RESEARCH METHODOLOGY .......................................................................................................... 15 BACKGROUND .................................................................................................................... 16 2.1 OVERVIEW OF PLASTIC TECHNOLOGIES .......................................................................................... 16 2.1.1 Stereolithography Apparatus (SLA) ................................................................................... 16 2.1.2 Fused Deposition Modeling (FDM) .................................................................................... 16 2.1.3 Binder Jetting ..................................................................................................................... 17 2.1.4 PolyJet Printing .................................................................................................................. 18 2.1.5 Selective Laser Sintering (SLS)............................................................................................ 18 2.1.6 Digital Light Processing (DLP) ............................................................................................ 19 2.2 METALLIC TECHNOLOGIES ........................................................................................................... 20 2.2.1 Direct Metal Laser Sintering (DMLS) ................................................................................. 20 2.2.2 Selective Laser Melting (SLM) ............................................................................................ 21 2.2.3 Electron Beam Melting (EBM) ........................................................................................... 23 2.2.4 Electron Beam Direct Manufacturing (EBDM)................................................................... 24 2.2.5 Laser Powder Forming (LPF) .............................................................................................. 25 2.2.6 Ion Fusion Formation (IFF) ................................................................................................. 27 2.2.7 Ultrasonic Additive Manufacturing (UAM)........................................................................ 27 2.2.8 LaserCUSING® .................................................................................................................... 29 2.2.9 Digital Part Materialization (DPM) .................................................................................... 29 2.3 OVERVIEW OF METALLIC MATERIALS OF AM ................................................................................... 31 2.3.1 Pure metals powder........................................................................................................... 31 2.3.2 Alloys powder .................................................................................................................... 32 10 Introduction 2.3.3 Metal matrix composites (MMC)....................................................................................... 34 3 CAPABILITIES AND OPPORTUNITIES ..................................................................................... 35 3.1 INDUSTRIES AND MARKETS .......................................................................................................... 35 3.2 DIRECT DIGITAL MANUFACTURING (DDM) .................................................................................... 38 3.3 DRIVERS FOR DDM IN AUTOMOTIVE INDUSTRY ............................................................................... 39 3.3.1 Mass production stability .................................................................................................. 39 3.3.2 Product variation ............................................................................................................... 40 3.3.3 Design Freedom ................................................................................................................. 41 3.3.4 Process Improvements ....................................................................................................... 42 3.3.5 Environmental Impact ....................................................................................................... 43 4 APPLICATION CASE – TURBOCHARGER................................................................................. 45 4.1 AREA OF INTERNAL COMBUSTION ENGINE (ICE) ............................................................................. 45 4.2 OVERVIEW OF TURBOCHARGER..................................................................................................... 45 4.3 MOTIVATION............................................................................................................................. 46 4.4 DESCRIPTION AND OPERATION ..................................................................................................... 47 4.4.1 Turbocharger Structure ..................................................................................................... 47 4.4.2 Operation principle ............................................................................................................ 48 4.5 TECHNICAL POINTS ..................................................................................................................... 49 4.5.1 Key components ................................................................................................................ 49 4.6 CRITICALITY ANALYSIS ................................................................................................................. 57 4.6.1 Objective ............................................................................................................................ 57 4.6.2 Criteria ............................................................................................................................... 57 4.6.3 Alternative AM Developments........................................................................................... 71 4.6.4 Method .............................................................................................................................. 76 4.7 SUSTAINABILITY ANALYSIS ........................................................................................................... 82 4.7.1 Life Cycle Assessment (LCA) ............................................................................................... 84 4.7.2 Manufacturing Cost Analysis ............................................................................................. 91 4.7.3 Production Cost Analysis ................................................................................................... 96 4.7.4 Societal Impact .................................................................................................................. 99 5 CONCLUSIONS AND DISCUSSION ........................................................................................102 6 FURTHER RESEARCH ...........................................................................................................105 REFERENCES ..............................................................................................................................106 APPENDICES ..............................................................................................................................111 11 Introduction 1 Introduction 1.1 Definition of Concept Additive Manufacturing (AM) is defined as the manufacturing process to build three dimensional objects by adding layer-upon-layer of material. The process starts with a computer-aided-design (CAD) file that includes information about how the finished product is supposed to look. [1] The material can be plastic, metal, concrete or even human tissue. AM is achieved using an additive process, where successive layers of material are laid down in different shapes. It is also considered different from traditional machining techniques that mostly depend on the removal of material by subtractive processes like milling or lathing. All AM technologies involve a series of steps that move from the virtual three dimensional geometric representations to the physical resultant part. Due to variety of the product demands and the level of complexity, AM involves in process development in different ways and different degrees. Furthermore, in the early stages of product development of small and relatively simple products AM is used for a simple fabrication of visualization model while in later stages the larger and more complex parts require certain technology and possible post processing activities for the final form of the product. Regardless the case, the construction process of all AM technologies follows to some degree at least the same principle generic process sequence. According to Gibson (2010) eight key steps can be defined as the generic process of AM: Conceptualization and CAD Conversion to STL Transfer and manipulation of STL file on AM machine Machine setup Build Part removal Post processing of part Application All AM parts must begin from virtual model designed on software describing the external geometry in detail. The output of the first step should be an STL file format given information of the external surface and the basic calculations of the slices of the part. At the next stage the part is transferred to an AM process software where is been manipulated accordingly to the AM technology restrictions and a machine code sequence is generated. As following, the products are carried out layer by layer 12 Introduction and according to the occasion some finishing operation is needed. The total procedure is indeed not necessarily a “rapid” process however AM involves to reduction of the development product time and thought the flexibility to decrease the number of required steps, it success a more economic but richer in variation of products and materials production. Nowadays Rapid Prototyping (RP) comprises AM and other non-additive methods for manufacturing physical objects at usually high speed and mostly for test purposes and not as a final part. Although, the American Society for Testing and Materials (ASTM) is standardizing the AM field by creating a new 3D generic file format for it called (*.amf) to substitute STL and others (IGS, STEP etc.). Consequently, new parameters are provided so that new AM machines can come to light and exploit their multiple capabilities. Nevertheless, AM is a very large division of RP and since RP was synonym of additive or layered manufacturing, nowadays they are still used as synonyms of each other in practice. The AM is also popularized with the term 3D printing, to make it more familiar and reachable to the public. In this thesis the term AM is used. The AM is not a new technology. It emerged with the invention of the first system, the stereolithography or SLA. It is a method that involves the use of a pool of a photopolymer resin where the successive layers are solidified and bonded to the previous ones by a UV laser that cures the liquid resin according to the required part geometry to produce 3D parts and it was developed by Charles Hull in 1984. The idea was patented in 1986. Then the invention of Selective Laser Sintering or SLS followed in 1987, a process that involves the melting powder substances to create an object via laser (again, find a more concise way of explaining SLS please). Later, the invention of "Three Dimensional Printing" (3DP) came out in 1993 by the Massachusetts Institute of Technology and the Z402 printer was introduced by Z Corp in 1996. During the next years several systems launched and the term “3D printing” was popularized. Today the AM has gained and earned its momentum. It can replace the traditional ways of manufacturing to meet the actual requirements of the industries. In addition, AM is available, nowadays, even for the households with the prosumer (producerconsumer) AM machines. Just in 2012, the AM has become more affordable and available for office, residential and academic purposes due to MakerBot together with RepRap that stormed the market. [2], [3] Moreover, AM can be applied in numerous fields. One of the applications of the AM products is the creation of moulds for sand casting made by SLS technology, that they can be used for casting patterns in the lost wax method or even as medical models for the visualization process to plan a surgery. Therefore some other most current and interesting applications in medical and dental fields can be the hearing aid shells, the dental aligners, or the orthopedical and craniomaxillofacial 13 Introduction implants. Furthermore, there are more applications in the aeronautical industry, the artistic and design field or in the academic level and research. Hot topics on AM are the biomaterials (tissue and organ printing), the new design principles and software, the adaptation of available materials and the addition of new materials for AM, the new, faster and less costly processes and the fact that bigger and metallic machines are about to be launched. [2] Some can be wondering if there is a demand for AM from the industry. The AM technology has already been tried back in the 90s and RP is still used when it is needed. The materials are not so good compared to conventional manufacturing but in some cases the rough surfaces and pores in metallic AM are actually very beneficial for prostheses. AM is slow for real manufacturing, more expensive and the technologies are not that precise with the production of poor surfaces, but if one needs a product that requires customization then the AM is the only way to produce it with an affordable cost comparing to conventional machining. On the other hand, AM today offers the freedom to create new geometries, materials with excellent properties and a variable composition, as well as the recycling of the material. As a result, a lot of research is being focused on AM since all the above characteristics, including the intense customer demands, force the companies to look for better responsiveness through better methods and improvements. AM is advantageous for customer-based production which is the key for a company in this competitive market. [2] 1.2 Problem Definition Today, the development of AM is focused on the production of complex shaped functional metallic components in order to serve more complex and demanding fields such as the aerospace, defense, automotive and biomedicine. The technologies for metallic AM use mostly a laser as the energy source, with the result of a non-equilibrium physical and chemical metallurgical nature that is dependent on the material and the process. The present review defines the capabilities and opportunities of metallic AM and investigates how AM evolves and benefits the mass productions in terms of sustainability and product development. 1.3 Research Scope and boundaries The research scope of this project is to investigate the influence of AM in the large scale productions in terms of technical, environmental and economic aspects. Metallic AM includes pioneer technologies and the limited source of information imposed boundaries on the scope of the research and states new demands for a state-of-the art case study. Therefore the scale of the research is 14 Introduction limited to the study of a device of a passenger car engine and a life cycle method which is restricted to reference data for the calculation of the environmental impact. 1.4 Research Methodology The presented research is conducted as: First a brief overview of plastic AM technologies as well as a more detailed investigation of the metallic AM technologies and metallic materials is carried out. The aim is to define the different metallic technologies and their specifications. Later on the capabilities of AM in different industrial applications and opportunities for the optimization of mass produced automotive components are introduced. The next chapter describes the application case of metallic AM. The investigation is carried out on a case study of a device of the internal combustion engine of a passenger car and a criticality analysis is carried out to decide which AM development of the component is more beneficial to the overall efficiency of the production of the device. In other words, the investigation follows a comparative method between zero point scenario (conventional production) and alternative developments (AM production). This chapter includes also a sustainability analysis of that development describing the environmental, economic and societal impacts. Finally conclusions are provided about the results of the sustainability analysis for the AM development of one of the components of the automotive device suggesting future research that will improve the capabilities of metallic AM. 15 Background 2 Background In this chapter an overview of the plastic AM technologies as well as a more detailed description of the metallic AM technologies are separately represented, including an outline of the most significant materials used in the latest technologies. 2.1 Overview of Plastic technologies 2.1.1 Stereolithography Apparatus (SLA) Stereolithography Apparatus (SLA), first of the AM technologies, is a liquid based process for making models. The models are built in layers within a reservoir of liquid thermosetting photosensitive polymer by selective curing via an ultraviolet (UV) laser beam. The laser beam continuously traces and selectively hardens the thin layer of polymer according to the current layer being built. Once tracing of the layer is complete, the platform that the model is built on moves down precisely one layer. Liquid resin is then dispensed over the model and tracing of the next layer begins. The layer thickness ranges from 50 μm to 150 μm. Supporting ribs for overhangs and undercuts are built up along with the model and later removed by secondary operations. When the model is complete the platform rises out of the polymer reservoir. Once the excess polymer drains away the model is removed for post-processing such as removal of supports. Additional curing and surface finishing is also needed. The SL machines can produce models as large as 650x750x550 mm. Additionally, multiple smaller models for model components can be nested together for simultaneous building. Models made by SLA can be extremely precise with thin (min 50 μm) and sharp features and smooth finishes (average Ra=8 μm). Substantial post-processing may be required however to separate the model from its supports. Depending on the application of the SLA technology, a variety of photosensitive thermosets is available but different chemically resins have been developed to simulate as close as possible common engineering materials such as PP (polypropylene), ABS (Acrylonitrile/Butadiene/Styrene), PC (polycarbonate), PE (polyethylene), PMMA (poly(methyl methacrylate)), nanoparticle resins, high temperature and composite, tough and durable, clear plastics. [4], [5] 2.1.2 Fused Deposition Modeling (FDM) Fused Deposition Modeling (FDM) involves feeding a thermoplastic filament (typical thickness 1.75 – 3 mm) into a heated extrusion nozzle that moves in the X and Y axes that form the horizontal plane 16 Background by convention. So the direction of Z axis is the vertical plane where the building of the part is done. The heated extrusion head melts and deposits the thermoplastic material on a table that moves on the z axis building the model. The molten thermoplastic is channeled through an extrusion nozzle which reduces it to a fine bead or deposition onto a substrate material. After depositing each bead, the model is built up layer by layer. Layer thickness of industrial machines is typically between 125 μm to 330 μm. As it is deposited the molten thermoplastic material is just slightly above its melting point so that solidification can occur immediately after extrusion as the material welds to previous layers. Additionally, post-processing techniques are required for support removal. Figure 1: MakerBot mixtape printed using FDM. 1 In FDM technology there is a wide range of materials that is used such as ABS, ABSi (Methyl methacrylate/Acrylonitrile/Butadiene/Styrene/Copolymer) that is beneficial for monitoring material flow and light transmission, ABS-ESD7 (Acrylonitrile Butadiene Styrene – Electrostatic Dissipative) that will not produce a static shock or cause other materials like powders, dust and fine particles to stick to it, ABS-M30 that gives stronger, smoother and with better feature detail parts, biocompatible ABS-M30i, PC, PC/ABC, ULTEM (lightweight and flame-retardant thermoplastic) and PPSF (Polyphenylsulfone). [6], [7] 2.1.3 Binder Jetting Binder jetting (also known as Inkjet Powder Printing) involves building a model in a container filled with powder of either starch or plaster material. For each layer, a roller will spread and compress a measured amount of material powder over the building table. A multichannel jetting head applies a small amount of liquid adhesive to bond the particles of powered material together and form the two dimensional cross section of the object for that layer. Upon application of the binder, a new layer is swept over the prior layer with the application of more binder and this process repeats until the model is complete. The layer thickness can vary from 90 to 100 μm. Additionally, there is no need 1 http://www.raeng.org.uk/news/publications/list/reports/Additive_Manufacturing.pdf 17 Background for support since the model is supported by loose powder and the great advantage of this technology is the speed fabrication as well as the low material cost. Engineers have developed a wide range of materials for this process. The different combinations available for pairing powder material with binder agents allows for a wide range of material properties. The composites used in Binder Jetting exhibit characteristics ranging from rigid to elastic and smooth to porus. Metals can be printed with this process, but while Binder Jetting cannot produce fully dense metal parts, the process is often used to create the structure for intricate metallic objects that are later fired to absorb metal into their porous structures. [8] 2.1.4 PolyJet Printing PolyJet printing is similar to inkjet document printing, but instead of jetting drops of ink onto paper, PolyJet 3D Printers jet layers of liquid photopolymer onto a build tray and instantly cures them with UV light. The head moves around the print area jetting photopolymer and UV light surrounding the head pass over the material after it is jetted onto the build area and cures it, solidifying it in place. Repeating this process builds up the object one layer at a time. Models are ready to handle and use right out of the 3D printer, with no post-curing needed. Materials that can be used by this technology are high-performance composites, elastomeric, transparent and opaque plastics, ABS-like, PP-like, rubber-like, temperature resistant material and bio-compatible polymers. [9] 2.1.5 Selective Laser Sintering (SLS) Selective laser sintering (SLS) technology begins by slicing 3D CAD data into thin cross sections or layers. The data is then transferred to SLS additive manufacturing equipment. The machine then begins to create the first layer. After a roller spreads a thin layer of powder material across the powder bed, a CO2 laser traces the cross section of the material. As the laser scans the surface the material is heated and fused together. Once a single layer is complete, the powder bed is lowered to make space for the next layer. More material is introduced from the powder cartridge and rolled out smooth while unused material is recycled. The process is then repeated building layer upon layer until the part is complete. As SLS parts are built, they are covered by unsintered powder that provides supplemental strength and eliminates the need for support structures. 18 Background Materials used in SLS technology include polymers such as polyamide (PA) (neat, glass-filled, or combined with other fillers such as carbon fiber) or polystyrene (PS); metals including steel, titanium, alloy mixtures; composites and green sand. [10] 2.1.6 Digital Light Processing (DLP) A Digital Micromirror Device (DMD) projects a light pattern of each cross-sectional slice of the object through an imaging lens and onto the photopolymer resin. The projected UV light causes the resin to harden and form the corresponding layer which fuses it to the adjacent layer of the model. Compared with Stereolithography (SLA), DLP can have relatively faster build speeds. This is because a single layer is created in one digital image, as opposed to SLA’s laser process which must scan the vat with a single point. SLA can be compared to drawing the layer one motion at a time while DLP is more close to a stamping process. When the process is complete, post processing processes are required such as the wash away of the remaining resin solution, the removal of the supports by snapping or cutting. Sanding or filing away what’s left behind by the supports is usually left until later, after the model has had a chance to fully harden, which can be expedited with a short time under UV lamps. Parts produced by DLP can be water resistant, flexible, durable, stiff, clear, thermal resistant and high impact resistant. The photopolymers have been designed to mimic ABS, polypropylene, and wax, making them useful for everything. However, prints using photopolymer can become brittle with increased exposure to light over time. [11] 19 Background 2.2 Metallic Technologies 2.2.1 Direct Metal Laser Sintering (DMLS) Direct Metal Laser Sintering also known as DMLS is an additive manufacturing technology that creates metal parts directly from 3D CAD data without the use of tooling. DMLS utilizes a variety of metal and alloy materials to create strong durable parts and prototypes. DMLS is a great choice for functional metal prototypes, high temperature applications and end-use parts. The process begins with the same way as the other layer additive manufacturing technologies. The 3D CAD model of the metal part is divided into 2D cross sections. Then the information is transferred to the DMLS machine. A recoater/roller dispatches material powder from the powder supply to create a uniform layer over the base bed. A laser then draws a 2D section on the surface of the material through heating and fusing it. Once a single layer is complete the base bed is lowered in a distance that is equal to the size of the thickness of a single layer. The raw material is again spread evenly on the previous sintered layer. The DMLS machine continues to sinter layer upon layer as a result the building of the part from the bottom up. During the build process, support structures are added to give supplemental strength to find features and overhanging surfaces. The completed part is then removed from the base bed and treated with a heat treating process to be further hardened. Any support structures are also removed at this time. Figure 2: How DMLS works. [12] DMLS parts can be used in highly cosmetic applications with post processing techniques such as surface treatment and hand polishing actions that are available through many providers. Typical uses for DMLS include tools, small integrated structures, surgical implants and aerospace parts. 20 Background The range of alloy powders now available for DMLS included stainless steels, cobalt-chrome, cobalt and nickel-base superalloys (IN 625, IN 718), maraging steels, dental alloys, Ti and Ti alloys (EOS Ti64), Al and EOS AlSi10Mg [13]. The following table indicates some of the specifications of the DMLS machine EOSINT M 280 provided by EOS [14]. DMLS technology Building Volume 250mm x 250mm x 325mm Build Rate 2 – 8 mm /s Laser Power 200 W or 400 W Scan Speed Up to 7.0 m/s Layer Thickness 20 – 60 μm Accuracy +/- 50 μm Power Supply 32 A Power Consumption Max 8.5 kW/ typical 3.2 kW Price 422 k€ 3 2 Table 1: EOSINT M 280 specifications. 2.2.2 Selective Laser Melting (SLM) Selective laser melting (SLM) is an additive manufacturing process that uses 3D CAD data the energy of a high powered laser beam (usually an ytterbium fiber laser) to create three-dimensional metal parts by fusing fine metallic powders together. The process starts with the introduction of a 3D model into software that slices the file into to 2D cross sections and sends it to the printer. The energy of a high power CO2 laser is used to fuse particles of metallic powder together. The same idea of AM happens also in this process. The recoater or roller sweeps a layer of the fine material powder and makes it ready for the laser to fuse them according to the 2D cross section under a controlled inert environment. With each successive layer scan, the platform bed is lowered incrementally. This process is repeated one slice at a time until the part built height is completed. Part support is accomplished by the unsintered powder that surrounds the parts during processing. Complete mechanical assemblies can be made mechanically functional simply by removing the unsintered powder. The result is a wide range of durable, high precision and functional end-use parts and prototypes. The main advantage of the SLM process is the possibility to build thin wall parts to a high resolution which extends its manufacturing capabilities. However many processing issues arise due to the use of 2 TCT 3D printing additive manufacturing product development. (2013). Buyers' Guide. TCT MAG 21 Background a high power laser to fuse the material from a powder bed. High heat input often causes an increase in material vaporization and spatter generation during processing. Surface roughness is another SLM issue that is influenced by particle melting; melt pool stability and re-solidifying mechanisms. [15]. 3 Figure 3: A pump manufactured by SLM Material powders used in SLM include; stainless steel powder of size 25-50 μm (named as CL20ES supplied by Concept Laser GmbH) that is recommended for the production of acid- and corrosionresistant parts or tool components for preproduction tools; tool steel powder of size 20-50 μm (named CL50WS and supplied by Concept Laser GmbH) which is recommended for the production of parts with characteristics similar to hot-work steel 1.2343 as well as tool components of plastic injection moulds; stainless steel powder of average size 25 μm (named as EOS Stainless Steel 17-4PH and supplied by EOS GmbH); Ti-6Al-4V and Ti-6Al-7Nb powder of size 25-45 μm (obtained from Concept Laser GmbH and its trade name is CL 40Ti); Co-Cr-Mo powder of average size of 50 μm; Cobalt chrome (ASTM75); Aluminum Al-Si-12; Inconel 718 and 625. [16] The Table 2 includes specifications of the SLM machine AM250 provided by Renishaw. [17] SLM technology Building Volume 250 x 250 x 300 mm Build Rate 1 – 6 mm /s Laser Power 200 or 400 W Scan Speed Up to 2.0 m/s Layer Thickness 20 – 100 μm Accuracy +/- 50 μm Power Supply 230 V 1 PH, 16 A Price 750 k€ 3 4 Table 2: Renishaw AM250 specifications 3 4 http://www.raeng.org.uk/news/publications/list/reports/Additive_Manufacturing.pdf http://businessjournaldaily.com/awards-events/namii-open-house-shows-potential-3-d-printing-2013-10-4 22 Background 2.2.3 Electron Beam Melting (EBM) Electron beam melting (EBM) is a type of additive manufacturing for metal parts. It is similar to Selective Laser Melting (SLM) with the main difference being that EBM melts the metal powder with the use of an electron beam in a high vacuum. When a layer is finished, the powder platform moves down, and an automated powder arm adds a new layer of material which is melted to form the next section of the model. Repeating this process builds up the object one layer at a time. When printing is completed, the build chamber, including the model and excess material inside, is left to cool. The leftover material is then recovered and recycled, leaving the final model behind. EBM takes place at such a high temperature that it produces parts that are practically free from residual stress and distortion at a micro level, eliminating the need for heat treatment post-processing. However, due to high temperatures in the build chamber, the object can be subject to some thermal stress or warping as it cools. Unlike some metal sintering techniques, the parts are fully dense, void-free, and extremely strong. Figure 4: How EBM works. [18] EBM printers can use various forms of titanium in addition to cobalt chrome. Due to the vacuum environment at high temperature, EBM can produce objects comparable to wrought material with better mechanical properties than cast titanium and cobalt chrome. Organizations can take advantage of this technology to produce both prototype and manufacture high-quality objects with great durability. Biocompatible implants have also been built by EBM. [18] The table below shows some specifications of the EBM machine QA2X provided by Arcam. [19] 23 Background EBM technology Building Volume 200 x 200 x 380 mm Build Rate 45 – 66 mm /s Laser Power 50 – 3000 W Scan Speed Up to 2.0 m/s Layer Thickness 50 μm Accuracy +/- 0.2mm Power Supply 3 x 400 V, 32 A, 7 kW Price 975 k€ 3 5 Table 3: Arcam QA2X specifications. 2.2.4 Electron Beam Direct Manufacturing (EBDM) Direct manufacturing is a process used exclusively by Sickay, Inc. in 2009 that melts metal wire as feedstock used to form an object within a vacuum chamber. During the EBDM process the energy from an electron beam gun is used to melt a metallic material that is usually wire. The electron beam head is controlled by a computer to melt the material and build up the object on a movable table. An advantage of this process is the fact that the electron beam is an efficient power source that can be precisely focused and deflected using electromagnetic coils and with the combination of the contamination-free environment of the vacuum chamber there is no need for additional inert gases (commonly used with laser and arc based processes). EBDM can produce very large end-use objects quickly. However, EBDM is not as precise as other processes since the parts produced have a very coarse surface that requires extensive machining after building is complete. Figure 5: How EBDM works Sciaky’s EBDM process has a standard build envelope of 48.3 cm x 10.2 cm x 10.2 cm (L x W x H), allowing manufacturers to produce very large parts and structures, with virtually no waste. A wide 5 http://www.aniwaa.com/product/arcam-a2x/ 24 Background variety of materials are available for use. Materials include titanium, tantalum, stainless steel, inconel, aluminum alloys, nickel-based alloys, titanium aluminides, and Metal Matrix Composites (MMCs) (including titanium matrix composites). There is now growing interest in strong steels such as Vascomax and 15-5 PH. [20] Figure 6: A sample of titanium parts created with Sciaky's direct manufacturing technology, which combines an electron 6 beam welding gun with wirefeed additive layering. 2.2.5 Laser Powder Forming (LPF) Laser Powder Forming can be used to repair or add volume to pre-existing metal objects, as well as manufacture new objects. LPF systems are marketed under the proprietary monikers Direct Metal Deposition (DMD), Laser-Engineered Net Shaping (LENS), and Laser consolidation (LC). In 1998, Optomec commercialized its LENS metal powder system. In 2002 Precision Optical Manufacturing (POM) announced the DMD technology. The power of a laser is used to melt the surface of the target area while a stream of powdered metal is delivered onto the small targeted area creating a melt pool. The computer controls the deposition mechanism and guides the melt pool to deposit a strip of material, building the object. The part is built up by repeating this process one layer at a time. The atmosphere is tightly controlled for LPF, allowing for high-quality, fully-dense builds. The material can be deposited in a variety of angles to produce complex geometries since the laser head can be manipulated by a multi axis joint and the object is built upon a rotary build platform. Compared to processes that use powder beds, such as Selective Laser Melting (SLM), objects created with LPF can be substantially larger. 6 http://www.sciaky.com/additive_manufacturing.html 25 Background Figure 7: How LPF works. [21] A wide variety of materials can be used such as nickel, iron, cobalt, and titanium based alloys, as well as refractory metals and cermets (ceramic-metal composites). Composite materials may include a nickel/cobalt matrix filled with tungsten carbide or titanium carbide particles. LPF can produce parts with as good or better mechanical properties than cast or wrought materials. Metals can also be heat-treated to improve its ductility and strength according to application. [21] The table below shows some specifications of the MAGIC machine provided by BeAM. [22] LPF technology Building Volume 1500 x 800 x 800 mm Build Rate 8 – 50 mm /s Laser Power 750 – 4000 W Layer Thickness 200 μm Accuracy +/- 0.1-0.5 mm Power Supply 400V (10%) / 50Hz Three-phase + Ground / 25A Price 550 k€ 3 Table 4: MAGIC machine specifications Figure 8: Knee prosthesis printed by BeAM on a MAGIC machine 26 Figure 9: Manifold printed by BeAM on a MAGIC machine. Background 2.2.6 Ion Fusion Formation (IFF) Ion Fusion Formation is a process used exclusively by Honeywell Aerospace that melts metal wire or powder with a plasma welding torch to form an object. Plasma of heated argon ions forces metal from a wire or powder feedstock onto the object. The deposition mechanism, controlled by a computer, creates a melt pool while feeding the material into it. The material is deposited only where it is needed to form a layer of the object. One layer is formed while the melt pool cools and hardens. The part is built up by repeating this process one layer at a time. The result is a minimal distortion and a very fine microstructure due to the high cooling rate of the metallic structure. Therefore, the deposits have improved mechanical and physical properties compared to milled objects from raw material. IFF is a relatively cheap but slow process compared with Laser Powder Forming (LPF) and Electron Beam Direct Manufacturing (EBDM). Figure 10: How IFF works [23] IFF uses tool steel alloys, nickel superalloys, and other materials that come in either a wire or powdered form. The parts which are produced consistently have excellent mechanical characteristics, but those produced from wire material must be processed further because of the rough surface it leaves behind. [23] 2.2.7 Ultrasonic Additive Manufacturing (UAM) Ultrasonic Additive Manufacturing (also known as Ultrasonic Consolidation, UC) works by using a delicate welding process to lock strips of metal together, building up an object by one sheet of material. UAM sticks strips of metal using ultrasonic welding (a solid state welding process that applies high-frequency ultrasonic acoustic vibrations locally to workpieces being held together under pressure to create a solid-state weld), meaning a bond is created without melting the material. The use of low temperatures avoids brittleness found between layers of traditionally welded metals, and 27 Background allows for metallic bonds between different metals. Moreover, a CNC mill completes the cross section by removing the excess material. Then the object is built one layer at a time by repeating the same process. UAM is ideal for special applications such as high-value end-use components due to its ability to create structures with multiple combinations of metals with tight bonds. The layer thickness for this process is defined by the material feedstock and can be as thin as 200 μm. SonicLayer™ 4000 is a fully automated UAM machine with a building envelope 1016 x 609.6 x 609.6 mm and power supply 4.5 or 9 kW. Figure 11: How UAM works [24] UAM uses metallic materials including nickel, titanium, copper, molybdenum, tantalum, silver, stainless steel and a variety of aluminum alloys. A big advantage of this process is its ability to interchange materials during the printing process. UAM can also create “smart structures” where additional components become part of the finished object. It is possible, for example, to embed electronics into a sealed internal cavity during the printing process. [24] Figure 12: Metal part produced by UAM technology. 28 Background 2.2.8 LaserCUSING® The term LaserCUSING® is made up of the letter C from CONCEPT Laser and the word FUSING (complete melting). The process is similar to SLM technology where the metal powder is dispatched on the surface of the build table and the laser fuses the cross section of the required layer. Then the process repeats until the part is complete one layer at a time. The special thing about the LaserCUSING® machines is the stochastic exposure strategy in line with the "island principle". The segments of each individual layer are called "islands" which are worked in succession in order to reduce significantly the stresses within the component. As a result, solid and large-volume components can be generated with low warping. The LaserCUSING ® layer construction process allows the production of both mould inserts with close-contour cooling and direct components for the jewelers, medical, dental, automotive and aerospace sectors. LaserCUSING® uses materials which are 100% compatible for re-use in subsequent construction processes. No fresh material has to be mixed. Typical layer thicknesses for all materials are 20-100 µm. The range of the materials used includes high-grade steels, hot-work steels, stainless hot-work steels, aluminum alloys, nickel-base alloys, titanium alloys, pure titanium, cobalt-chromium alloys, bronze alloys and precious-metal alloys. [25] The table that follows includes some of the specifications of a LaserCUSING® machine M2 cusing provided by ConceptLaser: [26] LaserCUSING® technology Building Volume 250 x 250 x 280 mm Build Rate 5.5 mm /s Laser Power 200 W Scan Speed 7.0 m/s Layer Thickness 20 – 80 μm Accuracy +/- 0.05 mm Power Supply 400VAC, 3phase, 22.1 kW Price 435 k€ 3 7 Table 5: Specifications of LaserCUSING® M2 2.2.9 Digital Part Materialization (DPM) Extrude Hone (currently known as ExOne) became the exclusive licensee in 1996 of the Digital Part Materialization technology developed at Massachusetts Institute of Technology (MIT) for metal parts 7 TCT 3D printing additive manufacturing product development. (2013). Buyers' Guide. TCT MAG 29 Background and tooling. Similar to the previous technologies, DPM utilizes a layering technique to create items one layer at a time from powdered material. The process begins with a CAD file that is sliced into very thin layers (0.1 – 0.15 mm). First, a layer of powdered metal is spread in the build box and a print head moves across the layer, depositing liquid binder according to the design for that layer. Then the layer dries and the build box is lowered slightly and a new layer of powdered material is spread. The part is complete by repeating this process until all layers have been made. The build box now contains a fully printed and bound part, surrounded by loose powder (which acts as a support). The part is considered in a “green state” at this point and very fragile. After printing, the build box containing the completed piece is removed from the machine and placed into an oven for curing of the binder to produce green strength for handling. Depending on the mass of the component(s), the curing operation takes 6-12 hours. During the next step, loose metal powder is vacuumed out of the build box. Air is used to dislodge any loose powder from the part. The excess metal powder is recycled. The part is fragile, but can be handled. The printed part is now depowdered and goes into a furnace for sintering. The part is placed in a graphite crucible, surrounded by support media, and placed in a vacuum furnace for one 24-36 hour cycle of sintering, infiltrating and annealing. Sintering is performed at about 1100°C to burn off the binder and metallurgically bond the metal particles. After sintering the component is approximately 60% dense. As a result, the metal parts are now strong and can be handled but still contain tiny internal gaps. For that reason, infiltration (a second thermal process) is required to bring parts up to full density. The final step is to gradually cool the furnace to anneal the part. Annealing lowers the tensile and yield strength, making the part less brittle for post machining such as milling, drilling and tapping operations. Finally, the thermallyprocessed metal parts are near 100% density and can be used functionally A variety of finishing options are also available, including protective coats and plating. Table 6 includes some of the specifications of a DPM machine M-Print provided by ExOne: [27] DPM technology Building Volume 800 x 500 x 400 mm Build Rate 2000 mm /s Laser Power 200 W Scan Speed 7.0 m/s Layer Thickness 25 – 50 μm Accuracy +/- 0.07 mm Power Supply 400V/2phase/6.3 kW max Price 200 k€ 3 8 Table 6: Specifications of DPM machine M-print by ExOne 8 http://www.aniwaa.com/product/exone-m-print/ 30 Background DPM uses a variety of metals such as 316 stainless steel infiltrated with bronze, 420 stainless steel infiltrated with bronze (annealed & non-annealed), bronze, iron infiltrated with bronze, bonded tungsten. [28] 2.3 Overview of metallic materials of AM 2.3.1 Pure metals powder Pure metals that have been applied for various AM technologies are titanium (Ti), tantalum (Ta), copper (Cu) and gold (Au). AM processes do not focus on pure metal powders comparing to the focus on alloys, because of the relatively weak nature of pure metals and the unsuccessful attempts to process pure metals with partial melting mechanisms. For example, the weak mechanical properties and poor anti-corrosion capabilities of pure metals are restrains for AM. Another example is the process of Ti through a partial melting mechanism like SLS that creates heterogeneous microstructure with regions of cores of unmelted grains, the melted surface of grains and the residual pores. However, the interaction between powder particles and laser beam can vary according to the scan speed in order to produce different porous structures. The advance of SLM, today, is advantageous for nonferrous pure metal components. Moreover, the high cost of titanium powder ($200 - $400 per kg) has forced the studies in AM to turn to the use of plastics for the production of parts. Rotherham based company Metalysis have developed a new way of producing low-cost titanium powder that makes the use of additively manufactured Ti alloy parts more affordable by the automotive, aerospace and defense industries. This new process could reduce the price of Ti by as much as 75%, making Ti almost cheap as specialty steels. The Department of Materials at the University of Sheffield uses a Renishaw 3D printer to demonstrate the production of titanium components using AM. The traditional way to produce Ti powder involves taking the metal sponge, which is then processed, melted into bar form and finally atomized into powder. A process that is costly and labor-intensive. Metalysis creates powdered titanium from rutile sand, naturally occurring titanium present in beach sands, using electrolysis, which is cost-effective. The use of this inexpensive and plentiful feedstock for titanium manufacture will dramatically reduce the cost of titanium production, allowing the increase of metallic AM especially in automotive industries. [29] 31 Background 2.3.2 Alloys powder 2.3.2.1 Ti- based alloys Ti based alloys processed by AM, typically Ti-6Al-4V, have exceptional mechanical and chemical features. The tensile strength of SLM manufactured parts can be higher than the one of parts produced by conventional machining. The reason for that is the unique hexagonal-close-packed (hcp) microstructure of Ti-6Al-4V. The ductility, however, is lower because of post processing heat treatment, but it can be improved by stabilizing the microstructures through variation of SLM conditions. Ti-6Al-4V is the most common Ti alloy in the industry. It is an α + β alloy that can be heat treatable to achieve increases in strength. It offers light weight, high strength, corrosion resistance, and formability that made it ideal for aerospace applications. Many properties of Ti-6Al-4V are restricted by the microstructure of α phase and other properties, such as fatigue response, can be dependent on the β phase, such as morphology, crystallographic structure, grain size, that are controlled by phenomena in solidification. As a result, the properties of Ti-6Al-4V are greatly affected by the process of solidification. During AM technologies there are many variables that influence the mechanical properties of the final part by affecting characteristics such as porosity, surface finish, residual stresses, microstructure and texture. The variables can be characteristics of the laser like its type, size, power, spot size and shape, speed or others like the layer thickness, powder shape, size distribution, powder velocity, powder feed rate, etc. [30] 2.3.2.2 Ni- based alloys Ni based superalloys (Inconel , Rene alloys etc.) are developed for high performance parts in jet engines and gas turbines because of an improved balance of creep, damage tolerance, tensile properties and corrosion/oxidation resistance. Rene alloys contain a total amount of 6 wt% of Al and Ti elements. Inconel alloys are Nb modified Ni based superalloys. Nevertheless, there is the possibility of the creation of cracks in the final part with the use of Ni alloys in AM. It is not difficult to eliminate all kind of cracks only by adjusting the processing parameters, so post processing steps are required to improve the mechanical properties of the component. [31] Inconel 718 is a NickelChromium alloy being precipitation hardenable and having high creep-rupture strength at high temperatures to about 700°C. Inconel 718 is one of the materials used by the SLM technology. The yield and tensile strength of the SLM material are a bit lower; 950 MPa comparing to 1030 MPa of the conventional machining and 1200 MPa comparing to 1230 MPa of the conventional machining respectively. On the other hand the elongation of 24% compared to 12% for conventional steel gives a much better resistance against cracks and fraction. Components produced by SLM® in inconel 32 Background alloys have excellent creep rupture strength at temperatures to 700°C and combine corrosion resistance and high strength with outstanding weldability. [32] 2.3.2.3 Fe- based alloys The use of Fe based alloys is not a significant part of AM. According to research, a part produced through AM processed steels cannot reach a full density. For that reason, the fully dense components are the target of AM of steels. The main disadvantage of AM of steels is the chemical properties of the main elements in steels. Both the main component Fe and the alloying element Cr are very active to oxygen, an element that cannot be fully avoided during the powder handling and the AM conditions. Consequently, the contamination layer of oxide that exists on steel metal surfaces during the processes can reduce the mechanical properties of the product. Additionally, the carbon content of AM processed tool steels and high speed steels has an unfavorable effect. According to research, when the carbon content increases the thickness of the carbon layer separated on the melt surface increases as well causing the same degradation as the oxide layer. AM processed high carbon steels can also be very brittle due to the development of carbides at grain boundaries. The increase of the heat flow in the powder being treated can dissipate the carbides, as well as, the optimization of laser type and a thin powder thickness (<100 μm for SLM) can offer homogenous result. [31] 2.3.2.4 Al-based alloys Al based alloys require more power for melting due to the high thermal conductivity of Al. The oxidation is another boundary due to the high vulnerability of Al based alloys to it. The adherent thin oxide film on molten Al reduces wettability. Oxide can also be trapped into the molten pool and create regions of weakness in the part. In addition, some technologies like SLM depend on the thin powder layer thickness which is not easy to be achieved due to the light poor ability to flow of Al powders. So that makes Al unsuitable for some powder deposition technologies. Although, SLM has recently been qualified for prototypes processed with Al-10Si-Mg alloy powder. According to research, it is found that Al-10Si-Mg products manufactured by SLM have the same mechanical properties as the ones manufactured by conventional machining, as well as, the accuracy of SLM processed Al-10Si-Mg thin wall parts can be increased with preheating. [31] 33 Background 2.3.2.5 Cu-based alloys Copper alloys are metal alloys that have copper as their principal component with great resistance against corrosion. The best known traditional types are bronze whose major addition is tin, and brass, using zinc. Bronze is much harder than plain copper. It is softer and weaker than steel but resists corrosion and metal fatigue and is a better heat conductor than steel. Brasses are usually yellow in color. The content of zinc varies between few to about 40% and if it is kept under 15%, it does not decrease corrosion resistance of copper. The cost of Cu-based alloys is generally higher than that of steels but lower than that of nickel-base alloys. These alloys have not been thoroughly investigated by AM technologies yet except for some results using DMD technology that resulted in Cu-based parts with almost the same mechanical properties as the one manufactured by conventional manufacturing. [31] 2.3.3 Metal matrix composites (MMC) Metal matrix composites consist mostly of metallic matrix and ceramics reinforcements that add more stiffness and strength. Nowadays, there is an increasing interest in MMCs powders for AM in order to achieve unique properties which are not usually available with single metal or alloy. When the ceramic reinforcing particles are added exteriorly into the metal matrix the MMC is called ex situ. Cemented carbide (WC-Co) is the most beneficial MMC for metallic AM. WC-Co is ideal for components that must withstand all forms of wear (including sliding abrasion, erosion, corrosion/wear and metal-to-metal galling) and exhibit a high degree of toughness [33]. The only obstacle to achieve full density MMCs components is the problem in gas entrapment and micro cracks due to weak interfaces that MMCs may have. A solution for this problem is to encapsulate the ceramic particles with a metal coating, in order to modify interfacial structure and promote wettability. In situ MMCs are made with chemical reactions between the elements. They are thermodynamically stable and less vulnerable to degradation in elevated temperature applications. Moreover, the ceramic/metal interfaces within in situ MMCs are generally cleaner and more compatible, yielding stronger interfacial bonding and elevated mechanical properties of the final products. In situ AM processed MMCs parts represent an important direction in AM research fields to fulfill the future demand. [31] A table with the most interesting materials produced by AM processes with their significant properties is presented in the Appendix 2 34 Capabilities and Opportunities 3 Capabilities and Opportunities 3.1 Industries and Markets In the recent years, substantial improvements in AM have enabled more and more applications and fields to use AM as a viable manufacturing method for industries. It started simply as a prototyping production, mould making and casting patterns application or complexly as a medical modeling creation for medical and surgery reasons. It used to be the solution only in highly specialized fields (usually early adopters due to the high profit margin and need of high customization). The main recent improvements have been in terms of production costs, material properties, part quality and accuracy. Considered as flexible and cost effective solution for the production of industrial demanding and complex products, AM is suitable for numerous industrial applications [34]. 25,00% 20,30% 20,00% 19,50% 15,10% 15,00% 12,10% 10,80% 10,00% 8,00% 6,00% 5,30% 5,00% 3,00% 0,00% Chart 1: The distribution of AM applications within different sectors. 9 Aerospace The aerospace industry is a key growth market for AM. Engine and turbine parts as well as cabin interior components with complex design can easily be manufactured thought a more cost effective AM production. The technology has the potential to make aerospace parts lighter, performing better and costing less compared to those manufactured by conventional techniques. 9 TCT Magazine 35 Capabilities and Opportunities An area that has recently adopted AM in final functional parts is aeronautics. GE aviation is currently designing a new aircraft engine which will include a number of additively manufactured critical metallic parts to save weight and optimize its design, reliability and overall costs. Boeing, however, has been using AM for over a decade to produce ducts and electronics covers and is today using AM for over 20.000 different parts in more than 10 military and commercial aircrafts [35]. A late adopter of AM for end-use components is the space industry. This market has been slowly entering the new paradigm of using AM for end-use parts with accelerating pace. Additively manufactured satellite parts start to be a viable option while NASA has funded the first 3D printer designed for the use at the International Space Station (ISS), which is planned to be launched in 2014. NASA and ESA are also developing specifically engineered 3D printers for building on-site space structures. Automotive Automotive manufacturers in large mass productions struggle with the needs of sustainable energy efficiency, reduction of emissions and production cost, the continuing demand for innovation as much the product customization. AM technologies, offering series of solutions such as maximum design freedom, lightweight components, individualized production and tooling free manufacturing can be applied profitably in automotive. Rapid prototyping as an application of AM also increases the efficiency of research and development. Through that the innovation of new vehicles can easily achieved, enabling the development to run faster and release the new versions quicker to the market. Recently the focus of AM components production is not only the geometrical product representation, which is originally the aim of rapid prototyping, but their functional ability and direct installation to the end-use product – vehicle. Consumer Products In the area of consumer products AM breaks down the boundaries imposed by early manufacturing methods. After years of progress and development AM is exploited in numerous fields of general public products such as jewelry, paramedic products, smart phone cases, radio controlled vehicles, shoes manufacturers and even fashion designers. Conventionally the large quantity productions are no flexible to changes in the design and the individual customer directions are not swift implemented. The conventional manufacturers face major challenges such as the demands for individual products, the high raw material pricing and the need for decentralized production, while AM creates a totally different picture. Consumers can set 36 Capabilities and Opportunities their own individual order which is produced directly, flexibly, economically and involving fewer raw materials through AM technologies. Large companies as Amazon, UPS, Wal-Mart, McDonalds or Tesco are already offering 3D Printing services or studying/adopting new business models to include AM in their current business infrastructure. Considering the principle that AM based on an entire digital process and meeting the challenges of consumer production industry, it could be applied in future concepts of direct manufacturing such as products to be configured online and manufactured directly in the store. Medical Medical is the sector that tailor made products are most needed, since every patient is a unique case and its care must fit perfectly. Therefore for this single unit production of medical products such as medical instruments and devices or even artificial implants the quality standards are significantly high. Moreover the cost and the time of production should be reasonable in order to be accessed from everyone. AM suiting perfectly in the area of medical applications, applies a fast, flexible and cost effective method for the production of medical products. It has the advantage of design freedom and implementation of unique features in addition to simultaneously production of individual parts resulting to a profit income. To give an example, several hundred individual dental crowns can be produced in a single operation [34]. Industry One of the most technically demanding, costly and time consuming aspects of production development in industry is the manufacturing of specialized tooling. Especially in tooling AM provides several advantages compared with the conventional processes. The restricted shape of tooling can be easily approached in building with geometrical freedom. Every individual custom tool can be produced by AM quickly without extreme cost charging or development in process planning. AM advantages against conventional processes are superior for more complex design with inner efficient cooling channels that needed for higher productivity of the tool. Furthermore the most composite geometries demand series of different conventional processes, while AM produces in one single build reducing the fixed and labor costs. Thus those achievements make AM one of the most convenient ways of tool manufacturing. 37 Capabilities and Opportunities Academic Sector The most important focus of academic sector is the research and development. In order to represent the stages of product and be able to act for changes and development, most of the institutes they use prototypes. Those models have been used for visualization of a certain concept and they need to be manufactured in a limited time and cost in order to contribute in a positive way to the product development. Therefore that was the primary sector of AM application, the Rapid Prototyping. The way to manufacturing directly from a CAD file without spending waste, time and labor is more competent than the traditional other ways (conventional manufacturing, craft work). In addition, during the recent years the increase of number of materials used leads to more realistic models. Prototypes developed by AM can be reverences for investigation of properties and mechanical or thermal behavior. Consequently that will influence the value of research results which will derive from a quicker and cheaper procedure, expanding the impact to a higher level. 3.2 Direct Digital Manufacturing (DDM) Direct Digital Manufacturing (DDM) which is also known as “Rapid Manufacturing” is the usage of AM technologies for the entire production or manufacturing of end-use components. However the use of DDM started as an extension of rapid prototyping, there are numerous more requirements and considerations when dealing with mass production manufacturing. DDM offers much more than an acceleration of the manufacturing process. An emphasis on “rapid” can lead to oversight of numerous advantages delivered throughout the manufacturing process [36]. The value of AM in DDM DDM is referred to AM and is considered as the opposite term of subtractive manufacturing. So it is first important to clarify what is subtractive manufacturing. From the early years of engineering, the manufacturing techniques were following the basic principle of applying the process of reduction to inputs such as a metal sheet. The aim is to succeed the final shape by removing material from the input sets of casting, lathing, milling, drilling and other conventional processes. DDM is not a simple revision of existing subtractive manufacturing methods but is another more rapid method that uses another form of input set, such as the raw material in a form of powder, and another series of instructions on how to manufacture by adding material instead, in order to build the final shape gradually. With the new ways of thinking, the new processes, the modified work flows and innovative procedures, DDM provide solutions to designers, engineers and manufacturers for cases that were previously impractical and impossible. 38 Capabilities and Opportunities However DDM is not a global replacement for manufacturing processes that are performing as needed expected or desired. In addition, since the economics of AM technologies do not enable economically competitive high volume production for most geometries and applications, DDM is often most economical for low-volume production applications [37]. Rather, DDM is an alternative that should be considered when the limitations and constraints of existing manufacturing methods impact the ability to manufacture a desired product practically, efficiently or affordably [36]. 3.3 Drivers for DDM in automotive industry DDM creates those opportunities for manufacturers in a diverse range of industries to realize significant benefits. In this research those opportunities are explored through an investigation of DDM, along with the advantages of AM in a mass production demanding industry as the Automotive. It is important to identify how the unique capabilities of AM technologies may lead to DDM applications in automotive industry. The drivers that enable DDM applications include: 3.3.1 Mass production stability Behind the economic concept of Adam Smith, the production of scale was a key factor after the industrial revolution. The development of new production lines times larger than the small sized local firms, the innovations of more efficient processes, the more specialized workforce and distribution of them in definite tasks had a result the reduction of the cost per unit. Products such as cars and clothes that originally are extremely expensive due to the high fixed cost were afterwards affordable from every customer. Until the late 1970s the higher productions achieved lower cost of production and as a result lower prices; hence the middle size companies became larger and more competitive gaining more market share. At the same time local firms, incapable to increase their production volumes and to follow the rhythm remained uncompetitive and mostly got disappeared [38]. Based in simple economic tails the cost of production is parted from the fixed cost and the variable cost. Fixed cost is originally independent of the production output and includes the buildings, the rent, the machinery, etc. Variable cost is more relative to the capital and labor includes wages, materials used, utilities etc. As the production increases the fixed cost can be shared more across the number of units, having as a result the cost of production per unit to follow a forward-falling curve. On the other hand in AM production, the fact that for the same result less processes needed implies to significantly less fixed costs comparing to the conventional production line. Therefore the graph of the production cost per unit will follow a straighter – with a minor downwards trend – line. 39 Capabilities and Opportunities 12 Cost per Unit 10 8 6 4 2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Units Conventional Manufacturing Additive Manufacturing Graph 1: Economy of scale – comparing AM with conventional manufacturing. Comparing those two curves and considering the starting point of both productions, the inference is that AM would benefit more small to middle size productions, achieving cost values less than the more demanding conventional productions. 3.3.2 Product variation The economies of scale benefit a production in large number of units but transform them in inflexible mass productions. Every mass production appears a tradeoff between the cost per unit and variation. Traditional calculation of manufacturing cost of a certain unit includes a change-over cost from one unit to the other to set up the machine. Thus, the equation of the total cost is: According to this calculation it implies that the more variation in production drives to the higher total cost. Since in economy of scale the lower total cost depends on spreading the cost over the large number of units production, there are two ways to control this. One way is to eliminate the Number of sets ups by producing in larger production in batches or sizes, but increasing the inventory same time. The other is to decrease the Number of variable products by making fewer rages of final products. Henry Ford summarized this dilemma and cost down the production of the cars by setting the number of variable products = 1 and he stated the following: "The customer can have any color he wants as long as it is black". Over the years of attempts in productions, a lot of improvements have been achieved. Especially firms such Volkswagen and Scania achieved to optimize the costs by applying methods of platforms 40 Capabilities and Opportunities and modularization. However those improvements the tradeoff between cost per unit and variation still remain. According to EOS “Economies of scale are fading. Global markets are facing ever shortening product life cycles. At the same time, product variety is on the rise. Manufacturing methods based on economies of scale are no longer in the position to meet these challenges” [34]. From the other hand AM is the unique technology that doesn’t effect this tradeoff. AM production is able to give totally different products from the fist to the second build. The reason is that there is of difference on change-over and no need of different set ups in a production. The AM machine is controlled from a computer which just sends the orders and monitors according to CAD files. Cost 4500 4000 3500 3000 2500 2000 1500 1000 500 0 3 4 5 6 7 Variation Conventional Manufacturing Additive Manufacturing Graph 2: The correlation of cost and variation. Comparing the two curves, obviously the contribution of AM in higher variation compared with conventional manufacturing is significant. 3.3.3 Design Freedom Conventional manufacturing has limitations in production of different geometries. Some designs are impossible to be manufactured due to access limitations of tooling in techniques of machining for removing material and structures limitation of casting molds. Complex shape products usually are extreme time consuming in process planning and operation, as much as they demand specialized equipment and tooling. Therefore those productions are extremely costly. 41 Capabilities and Opportunities Opposite, AM by adding material becomes simple to manufacture complex parts without tradeoff between complexity and cost. The times for process planning, different setups and processes are combined in one single process time. AM can find easily application where there is no either way to produce individual and complex components because of their geometry. Figure 14: Examples of direct metal laser sintering (DMLS) © Econolyst Figure 13: Complex geometry achieved through AM production © Pinoko Furthermore, another important capability of AM is appeared in the inner structure of a part. Tubes in complex shapes, cells and lower solidity can easily achieved though building layer – by – layer. Numbers of applications are benefited from this. Inner tubes are crucial element for inject molding in lubrication and reduction of heat. Cells increase the isolation and adjustable solidity reduces product weight. Structures with inner lower density are also fundamental improvement for the production, decreasing the raw material needed and the final cost relatively. 3.3.4 Process Improvements A conventional production line is highly demanding management over supply chain and logistics. Industrial lines are very precise in lead times, process times, volumes and inventories in order to achieve the right materials to be available at the right place the right time. AM however provides the opportunity to cope with time and space through a more distributed manufacturing. The orders can be sent as files electronically wherever the AM machine is located and the entire product can be manufactured directly, the right product at the right time without the complexity of supply chain and inventory procedures. The possibility will let the manufacturer to make the product more near to customer, so that the packaging, transportation, and lead time will be decreased thanks to the decentralization of the production system [39]. In widely distributed productions usually the investment cost is higher than 42 Capabilities and Opportunities the centralized due to the multi times more distributed tooling and other sub – equipment. However AM production is free of sub – equipment and extra tooling therefore is get befitted more by limited Cost investment and transportation cost. 4500 4000 3500 3000 2500 2000 1500 1000 500 0 3 4 5 6 7 Distance Conventional Manufacturing Additive Manufacturing Graph 3: The correlation of cost and distance In addition, considering that every new development, new versions and new products that enters in the market should be developed according to a new process plan, that development requires specialized machines, new customized tooling, operation training and in general a large investment cost. In that case AM benefits the production providing an economical solution without any special changes and same time making the production more flexible in new developments and more competitive [39]. 3.3.5 Environmental Impact Originally conventional production systems are more energy consuming in total than an AM system. The manufacturing of a product requires a production system consisted from milling machines, heavy presses, melting machines. For the same production, AM requires a single machine using just a laser beam device. This difference in the total energy consumption in large unit production can be vital in the environmental footprint of an industrial line. Another environmental factor is the waste. By definition, conventional production is more or less subtractive techniques that remove material which often becomes useless. This waste is cost effect for an industry but it is eventually also a drag on the environment. AM having better environmental standing by applying a totally opposite concept, uses as much material as needed with less if any production of waste [39]. Furthermore the capability of AM to adjust the solidity of the parts 43 Capabilities and Opportunities according to the products functional demands, adds flexibility to production for reduction the material used and therefore effect positively to the environment. The successful decentralized production system as is discussed previously, it can be a critical method to reduce the environmental impact switching simultaneously from conventional to AM production. The possibility to set the production location close to the material resource or to customer without need for significant investment cost is definitely an opportunity to reduce the distances and the transportation emissions respectively. 44 Application Case – Turbocharger 4 Application Case – Turbocharger 4.1 Area of Internal Combustion Engine (ICE) The Internal Combustion Engine (ICE) has been a primary power source for automobile over the past century. In a variety of different structures the compartment of the ICE is the area of the group of several devices where the reactants of combustion (the oxidizer and the fuel) as well as the products of combustion serve as the working fluids of the entire engine. The efficiency of the cooperation of ICE devices is achieved from the energy offered to the engine from the heat load released during the combustion of the reacted working fluids. The energy that released from the combustion becomes useful work. The hot gaseous products of the combustion move over a distance several components such as pistons, impellers and nozzles, transforming the chemical energy into mechanical energy. The compartment of the ICE is of key importance within this research, as most of the components are placed under extremely high thermal and pressure stress and they consist also the higher cost of an overall passenger vehicle. The majority of the components of an ICE are produced according to state of the art design providing high power –to-weight ratios together with excellent fuel energy density. Under full load, every ICE component should meet the requirements of extreme thermal and mechanical properties. 4.2 Overview of turbocharger Turbocharger (Turbo) originated from the word turbulence. It is a device based on a turbine operation that produces more power for an engine and increases the efficiency. The scope of application of a turbocharger as a sub component is to interfere in the air circulation towards and from the engine block and by changing the pressure to success more powerful combustion. A turbocharged engine compared to a naturally aspirated engine has the advantage to recover the waste energy from the exhaust and feed in it back boosting the final horsepower without significantly increasing its weight. The turbocharger was invented by Swiss engineer Alfred Büchi, the head of diesel engine research at Gebrüder Sulzer engine manufacturing company in Winterthur in 1902 [40]. At the early years, turbochargers found application in aircraft engines but in a primary version mechanically driven by engine and not by exhaust loads, known as superchargers. Later on, more advanced turbochargers were equipped in marine engines and other aviation technologies. Nowadays turbochargers are used 45 Application Case – Turbocharger in several areas from vehicles and trains till aircraft as part of the main engine. The most common application is in automotive industry for diesel internal combustion engines. 4.3 Motivation According to the definition problem of this thesis, the project consists of an investigation of possible application of metallic AM in large scale production industries in terms of sustainability and life cycle product improvements. One significant challenge with several developing possibilities is the automotive industry. Within the project thesis, the investigation focuses on an automotive engine since it is a source of a large range of critical metallic parts demanding for light weight and optimization in design, reliability and decrease overall costs. One engine component that seems to be ideal and valuable for this development and research is the turbocharger device. Of course that selection is not random but there are several features added in turbochargers that lead to. Size Most common turbocharger designs equipped in diesel engines for passenger cars are produced in dimensions of an average middle sized engine part. Almost all middle sized parts have tolerances and upper limit sizes that are easily approachable from most of metallic AM technologies. Also the possibility to fabricate a multi pieces device as turbocharger through AM, as much as possible consolidated is an extra opportunity. Shape and complexity Turbocharger, due to its specific operation, is exposed to extreme conditions of high temperature and pressures. Turbochargers are relatively limited in terms of design structure due to the boundaries in the traditional ways of production. On the other hand AM technologies take advantage of maximum freedom of design, they can hint improvements in performance of turbocharger with a more suitable and complex structure. Low emissions The turbocharger is a type of force induction system. It affects positively the combustion by increasing the horsepower without influencing the fuel consumption. It is a significant advantage. Furthermore, turbocharger fabricated with light weight alloy materials by AM technologies and may improve the ratio of power to weight, achieving the overall targeted car performance using less fuel, and proportionately producing fewer emissions. 46 Application Case – Turbocharger Recovery energy waste Turbocharger may also increase the fuel efficiency without increasing the power. They can achieve that by recovering wasted energy from the exhaust gases and send it back to the engine. By compressing the air flow to the combustion higher efficiency is succeeded (Carnot cycle). In these points there are opportunities provided by AM in terms of new structures and more complex surfaces in order to achieve higher compressing levels or more efficient waste energy recovering systems. Production process As it has been mentioned, devices such as turbocharger with high level of complexity due to large number of spare parts definitely require numerous processes and assemblies for their production. The development of these devices through alternative production ways, such as AM technologies, aims to reduce the steps and the number of processes to produce products with the same or higher performance. Benefited from the capabilities of AM technologies comparing to traditional ways, such as casting in case of the turbocharger the production can be optimized in time and overall cost. 4.4 Description and Operation 4.4.1 Turbocharger Structure The control of turbochargers is very complex and their structure has been changed extremely the recent years and the applications increased. Turbochargers’ performance is affected from their size [41]. Large turbochargers remove more heat and simultaneously pressure to spin the turbine but in low RPM. Smaller structures spin faster but missing performance at higher acceleration of compressor [42]. Modern turbochargers vary in geometry accordingly the use that they addressed to. The investigation of this project thesis is referred to a turbocharger of a passenger car, manufactured by Garrett. 47 Application Case – Turbocharger Figure 15: Turbocharger used for a Diesel engine by Garrett (Model No. GT 1749V) 4.4.2 Operation principle The turbocharger is bolted to the exhaust manifold of the engine. The exhaust from the cylinders passes through the turbine blades and spins the turbine. The more exhaust that goes through the blades the faster the turbine spins. The turbine is connected by a middle shaft to the secondary part, the compressor. The compressor is a type of centrifugal pump which pull air in the center and flings it outwards though a centrifugal tube. The compressor, located between the air filter and the intake manifold, increase the pressure the air driven to the engine combustion. 10 Figure 16: Operation of the turbocharger system. 10 www.zageturbo.com 48 Application Case – Turbocharger The ambient air passes through an air filter (not shown) (1) and then it is compressed which raises the air’s density (2). Many turbocharged engines have a charge air cooler (aka intercooler) (3) that cools the compressed air to further increase its density. After passing through the intake manifold (4), the air enters the engine’s cylinders, whose volume is fixed. Since the air is at elevated density, each cylinder can draw in an increased mass flow rate of air. After the fuel is burned in the cylinder it is exhausted during the cylinder’s exhaust stroke into the exhaust manifold (5). Then the turbine receives the high temperature exhaust gas produced by the combustion (6). The turbine creates backpressure on the engine which means engine exhaust pressure is higher than atmospheric pressure. A pressure and temperature drop occurs (expansion) across the turbine (7), which utilizes the exhaust gas’ energy to provide the power necessary to drive the compressor. 4.5 Technical Points 4.5.1 Key components The following table includes the main components of a turbocharger: Table 7: The main components of a turbocharger. 49 Application Case – Turbocharger Compressor Housing The compressor increases the pressure of intake air entering the combustion chamber. The compressor is made up of an impeller, and housing. Compressor housings are mostly made of cast aluminum. The manufacturing process for compressor housings is usually the sand casting process. Core is made by filling a mold of the interior geometry of the housing with sand and either compressing or heating it to cure it into shape. The core is placed in sand mold for the turbo. The cope and the drag of mold are pressed together closing the mold. Then molten aluminum is poured into the mold and let cool until the aluminum solidifies. The mold is opened and the sand is broken apart to remove the cast turbo. Further machining is also necessary to finish the detailed geometry. Compressor Impeller The compressor is ingesting air at slightly more than ambient temperature. With inlet ambient air and pressure ratio 4:1 at 80% adiabatic efficiency, the compressor outlet temperature can exceed 200 °C. A compressor impeller operates often at over 100,000 RPM and is subjected to high centrifugal loads. Because of the centrifugal forces, stresses are generated in the impeller according to its mass and the rotational speed. Due to the complex geometry of the impeller blades, unique challenges in the selection of material and manufacturing processes are created. Cast impellers are almost exclusively produced using an aluminum casting alloy. To balance strength and ease of casting, the material used for the compressor wheel is normally an Al-Si-Cu-Mg alloy. Alloying elements are added to improve the properties of aluminum and avoid plastic deformation because pure aluminum is ductile and soft. Figure 17 shows the apparatus for the low-pressure casting process. Air pressure is applied to the surface of the melt that is contained and heated in a sealed vessel in the lower portion of the plaster casting mold, forcing the melt through a stalk connected to the mold and inserted into the melt so that it flows up into the mold. Compared to gravity casting, the pressure method has the effect of reducing shrinkage cavities and other internal voids. [43] 50 Application Case – Turbocharger Figure 17: Apparatus of the low-pressure casting method Figure 18 shows the vacuum casting method for producing aluminum impellers. This vacuum casting process utilizes a foamed plaster mould produced from a rubber pattern. This method enables the casting of thin sections by drawing a vacuum through the mould. The casting is produced by lowering the pressure in the mould cavity, which in turn induces the molten aluminum to fill the mould cavity under atmospheric pressure. One of the drawbacks of cast impellers is that the casting process can lead to the formation of casting defects, which can reduce the durability of the impeller. Figure 18: Apparatus of the vacuum casting method Cast aluminum cannot normally achieve the same durability as wrought aluminum for turbocharger impellers. So another process of producing impellers is the machining from solid. Nowadays a large percentage of compressor impellers are Machined-From-Solid (MFS) and are produced using stateof-the-art high speed five axis milling machines. However, for all aluminum alloys there are limits imposed on the temperature of operation due to temperature related material effects, notably softening, ageing and creep. When extreme temperatures and stresses are applied, especially those generated at the highest compressor ratios, the use of aluminum cannot be used as an impeller material. If the compressor outlet temperature guideline for aluminum impellers is exceeded, or if the required fatigue life is 51 Application Case – Turbocharger greater than that of MFS aluminum impeller, then titanium impeller is preferred. Titanium impellers are made using the investment casting process. A wax pattern of the impeller is made using a steel tool and assembled on a casting tree with other waxes. The wax assembly is first coated with a proprietary ceramic face coat and subsequently with a coarse ceramic back-up coat to create a shell mould. The shell is dried and the wax melted out before the titanium is cast in a vacuum arc or induction skull re-melt furnace. The principles of the two furnace types are the same: a titanium electrode is melted under a vacuum, by striking an arc between the electrode and a cooled copper crucible and then poured into the mould.[44] Most common aluminum alloys for compressor impellers are Al C354 with Hot Isostatic Pressing (HIP) or Al C355 without HIP, Al 7075 alloy, Al 201 and titanium alloy TiAl6V4 is used also by BorgWarner since 2001. HIP is a manufacturing process used to eliminate internal micro porosity in metal castings and other materials and also enables the densification of metals in the solid state in order to result in superior material properties. [45] Bearing System The bearing system which supports and positions the rotor assembly (turbine, shaft and compressor) resides in the turbocharger center housing. The bearings are subjected to rotating loads and substantial thrust loads in either direction, depending on operating conditions. The bearing system also has an influence on critical rotor speeds, vibration and shaft instability. Challenge is also presented to the bearing system due to the temperature of the contact with the turbine. If the engine is shut down immediately following a run at high power output, the turbine and turbine housing temperatures are toward their upper limits, and suddenly all gas flow through the turbine stops and all oil flow through the center housing stops. All that heat must go somewhere, and an easy path is into the center housing. The resulting temperatures can easily “cook” the oil to a solid with potentially disastrous results on the next run. The centrifugal force at very high speeds can cause steel balls to take off during acceleration. In order to avoid that problem, some manufacturers have replaced the brass bearings with ceramic bearings that are stronger with less friction, as well as more heat resistant. [46] 52 Application Case – Turbocharger Garrett uses an integrated dual ball bearing cartridge which contains an angular-contact ball bearing at each end, providing a huge bi-directional thrust capacity, and which adds bending stiffness to the shaft system, helping to prevent critical speed issues. Borg-Warner is developing a two-ball-bearing system which is expected to be fully ceramic. [46] The fully floating design of bearing system consists of two bushes, one at either end of the bearing housing through which the shaft passes, unusually these bushes themselves are allowed to rotate in their housing, creating in effect a 'bearing within a bearing'. Manufactured from aluminum, or more likely from leaded bronze, these bearings are loosely restrained axially using a pair of 'snap' rings, on either side, and rotate along with the shaft according to the friction balance within the system. [47] Bearing System Material Production Process Al Leaded bronze (CuSn alloy) Machining Brass (CuZn alloy) Center Housing The greatest temperature gradient in the turbocharger arises between the turbine housing and the bearing housing. In automotive applications the interior design of the center housing consists of channels that lubricate the bearings by constantly supplying them with pressurized engine oil. The center housing is also water-cooled by having an entry and exit point for coolant. These kind of water-cooled models use the coolant to keep the lubricating oil cooler in order to avoid potential oil cooking due to the extreme heat in the turbine. Bearing housings or center housings are usually made of cast iron or stainless steel. Iron is suitable for the turbocharger center housing because of the high temperatures that it is exposed due to the turbine housing. Aluminum replaces sometimes the traditional heavy iron housings. Exile Turbo Systems has lightened the bearing housing in that way. Exile uses also a separate cast-iron shroud installed between the aluminum center-section and exhaust housing that protects the lightweight aluminum from excessive exhaust-side heat transfer. This housing also has water-cooling provisions. [48] 53 Application Case – Turbocharger Turbine Impeller and Shaft The turbine is driven by exhaust gasses that can exceed 1000 C and which are very corrosive. The turbine impeller opera tes in a continuous, high-velocity jet of the exhaust gasses. The temperature at the tips of the turbine rotor can approach exhaust gas temperatures. The rotor system operates in excess of 100,000 RPM, and some approach 150,000 RPM imposing huge tensile loads from the centrifugal forces, as well as bending and vibratory loads. [46] Turbine wheels are generally melted from high-strength nickel base alloys. Their manufacturing process is a high strength investment casting process that, from melting to casting, takes place in a vacuum. Inconel 713C is a standard material for turbine wheels. This nickel-based heat-resistant alloy is a material that manufacturing engineers dislike. It is designed to withstand high temperatures, with an inevitable trade-off in machineability. Other common nickel-based alloys used for turbine impellers are Inconel 718 and Inconel 706. However, Inconel 713C does not meet the criteria for anti-creep characteristics at 1,050°C, so Mitsubishi Heavy Industries (MHI) has decided to use MarM (developed by Martin-Marietta in the seventies for gas turbine engine blades, discs and burner cans) for passenger car turbochargers [51]. Honeywell uses a superalloy material known as MarM–247. This material is a nickel-based alloy containing significant amounts of chrome, aluminum and molybdenum. In order to achieve optimal properties in components cast from Mar-M-247, the Grainex process was developed. This process uses traditional investment casting techniques, with the additional process of mold agitation during freezing to produce homogeneous grain inoculation, resulting in outstanding uniformity of grain structure and material properties. The part is hot isostatic pressured at 1185 °C and 170 bar for four hours to minimize porosity, then solution treated for two hours at the same temperature, followed by 20 hours of aging at 870 °C. That produces a room temperature ultimate tensile strength (UTS) of approximately 965 MPa, which increases with temperature up to 760 °C. [46] MarM is a heatresistant alloy with greater strength at high temperature. Since MarM is more difficult to cast and more likely to have casting defects than Inconel, MarM needs a hot isostatic pressing (HIP) process to remove casting defects and to homogenize the material structure. Before using MarM in mass- 54 Application Case – Turbocharger produced vehicles, tensile and creep tests have been made in order to conclude that the creep life of the MarM turbine wheel is about three times as long comparing to the Inconel turbine. Today, in the area of light-weight materials for elevated temperatures intermetallic γ-titanium aluminides (γ-TiAl) are aimed to replace conventionally used alloys. They offer outstanding thermophysical properties which make them superior on a density related basis to the currently used nickelbased superalloys. Impellers for superchargers (Figure 19) from titanium aluminide alloys are at the same time extremely light, corrosion resistant and of high-strength. [52] Figure 19: Impellers for superchargers from titanium aluminide alloys are at the same time extremely light, corrosion resistant and of high-strength Ceramic turbine impellers are being developed as well in order to take advantage of their light weight and the high heat resistance. Although the cost of production of ceramic impellers is very high and the shape is still not optimized. The turbine impeller is connected by a shaft to the compressor impeller. The shaft is usually made of steel by machining process. A common steel alloy for the manufacture of the shaft is steel 4140. In order to assemble the steel shaft with the turbine impeller friction welding is used. Friction welding was developed in the 1980s as a relatively low cost and reliable welding process, which proved ideal for attaching a turbocharger’s comparatively soft steel shaft to the much harder turbine wheel investment casting. During the process, friction between a rotating and a stationary component causes the two metals to become red hot and pressure is applied to forge the parts together. 55 Application Case – Turbocharger Turbine Housing There is an array of turbine housing materials to meet customer exhaust gas temperature requirements, including ductile cast iron with an allowable temperature of 700 C and austenitic stainless cast steel that resists temperatures exceeding 1,000 C. There are two types of cast steel, the ferritic and austenitic cast steel types, whose properties differ significantly. The advantages of ferritic types of cast steel are the low alloying costs, low thermal expansion and good casting properties. The ferritic types have reduced creep strength over time for the same temperature when compared to the austenitic types. They are more brittle due to their carbide content. The austenitic cast steel types have higher creep strength, good resistance to cyclic thermal stress, are easy to cast and are usually easy to weld. Many turbine housings of recent gasoline engine turbochargers are made of austenitic stainless cast steel. Turbine housings made of heat-resistant austenitic cast steel with a high nickel and chromium content for applications at 1050 C is already being used today by BorgWarner Turbo Systems for mass-production customer engines. [47] 56 Application Case – Turbocharger 4.6 Criticality Analysis The decision making process is not able to result in a rational outcome if it is executed through subjective and one-dimensional analysis of the data. The complexity and significance of the decisions to be made creates an even greater complication to the whole thing. The criticality analysis, as a method of decision making is a part of the Operational Research that flourishes during the last decades, because it can reach the decision through a multi-dimensional and objective analysis of the factors that affect it. Although there are still some difficulties during the part of the criticality analysis when one should decide on the criteria of the analysis that discourages some decision makers from adopting this method. It is actually quite difficult to compose and evaluate all the necessary criteria for obtaining a rational decision. This is a problem that needs to be solved by today’s researchers in this field. The main characteristic of the criticality analysis is not just the connection of the alternatives/criteria that will affect the decision but mainly adapting of all these criteria to the system of values and preferences of the decision maker. This feature is very important because through the decision making process the decision maker is obliged to play a passive role by accepting the application of the results of mathematical models. So the criticality analysis contributes to the identification of the key features of the under-consideration problem, and the special nature of the available solutions, as well. The steps of a criticality analysis include the definition of the objective, the description of the criteria and the choice of the right alternative at the end. 4.6.1 Objective The objective of this analysis is the selection of the most critical component of the turbocharger developed by AM technologies. In other words, the result indicates the component whose development contributes more to the efficiency of the turbocharger. The final product, a combination of conventional and AM manufactured components when needed, is an improved turbocharger from the aspect of defined criteria of production and end use product. 4.6.2 Criteria The criteria chosen derived from Design, Engineering and Production aspects and they are divided in three groups accordingly. Each group of criteria describes the importance of the characteristics of design, production and performance of a turbocharger device. Design aspect: size, variety of material properties, design optimization 57 Application Case – Turbocharger Engineering aspect: life, functional limits, efficiency Production aspect: process consolidation, production cost, recyclability Some criteria may also belong or interact in more than one aspect. Furthermore, the improvement of one criterion in our case can possibly affect any other from the same or another group. For instance the design optimization could affect positively the functional limits but increase the production cost. Size The size is another criterion that has to be met by the conventional production processes as well as by the additive manufacturing technologies. An average turbocharger for a car engine has a small size. For example a medium size turbocharger includes a compressor and a turbine wheel whose diameter can be about 50 mm and 45 mm respectively with a pressure ratio 4:1. One of the smallest turbocharger has been manufactured by Garrett with a compressor wheel of 32 mm and a turbine wheel of 30mm diameter size [53]. These dimensions can even reach the 270 mm for compressor wheels and 245 mm for turbine wheels in case of a large sized turbocharger [54]. The dimensions of the components of the turbocharger can be reached by any casting technique that is used for the conventional manufacturing. The achievable dimensional tolerances on investment casting are dependent on the casting material, the dimensions and shape of the casting and the validity of the accuracy grade. Moreover the accuracy of the casting process depends on the experience. During the solidification and cooling of cast metals, a contraction of the volume naturally takes place as a result of shrinkage. Other factors can result from the shrinkage of the lost pattern and the expansion of moulds during heating that can influence the production of instrument castings. During the manufacture of injection moulds, these influencing factors are taken into consideration in the shrinkage allowance which is based on experience values. 58 Application Case – Turbocharger Figure 20: An illustration showing the dimensions of a large size turbocharger series by MTU a brand of Rolls-Royce Power Systems AG. [54] On the other hand the current metallic additive manufacturing technologies can equally produce this kind of sized parts with good tolerance limits. For example the building volume of SLM machine is 250 x 250 x 300 mm. An issue of the AM techniques is surface roughness and accuracy that is not sufficient for part production unless some kind of post-processing is added to the manufacturing process that will result in an increase in lead time and cost. But hybrid machines can solve the problem, for example a hybrid machine like Matsuura LUMEX Avance-25 which is able to combine metal sintering with subtractive milling process after every single layer if needed. This machine will benefit of machining accuracy and surface roughness. Variety of Material properties It would be a mistake to assume that the parts produced by conventional methods and the ones produced by AM have identical properties. Even for conventional manufacturing the parts produced by different techniques have different properties, such as the cast Ti6Al4V which has different properties comparing to wrought Ti6Al4V. So it is logical that AM parts will differ from conventional parts in corresponding material. In general the differences are usually predictable but sometimes they may be unexpected. It is worth mentioning whether the difference in a property is an improvement or a disadvantage depends on the application. One example is that the parts made by laser-based methods have usually finer grain size of the internal metallic structure than conventionally produced parts with same material. This is happening because of the laser scanning. The removal of heat is instantaneous once the laser spot has moved on so the material re-solidifies rapidly and the heat is conducted fast out of the melted zone to the 59 Application Case – Turbocharger surrounding area that is either solid metal or powder bed. Also the resulting structure of the final part is not as expected. Since the building of the part is done layer-by-layer, “lines” are expected to be seen in the resulting structure. Although Ti6Al4V laser sintered parts have a dendritic structure. The crystals are oriented perpendicular to the applied layer and their height is greater than the layer thickness. This can be explained by the laser energy of each vector re-melting part of the previously solidified layer below and then re-crystallization causing the crystal to grow through the layers. [55] Another example is the difference in mechanical properties of some materials produced by AM. A common material for the turbine impellers is Inconel 713C produced by investment casting process. However, this alloy lacks in its mechanical properties comparing to other available Ni-based superalloys; the ultimate tensile strength (UTS) is 758 MPa, the yield tensile strength (YTS) is 689 MPa and the elongation break (BE) is only 3 %. The turbine impellers are also produced by Inconel 718. According to Melotte Direct Digital Manufacturing, test parts made of Inconel 718 have been produced using the SLM technology. Their results showed that the yield and tensile strength of the SLM material are a bit lower comparing to the conventional material; the YTS of Inconel 718 made by SLM is 950 MPa that is smaller than the 1030 MPa of the conventional mechanical data. The same happens with the UTS (1200 MPa of SLM part; 1230 MPa of conventional part). On the other hand the elongation of 24 % compared to 12 % for conventional Inconel 718 gives a much better resistance against cracks and fraction, fact that can benefit the production of turbine blades by the SLM technology. Turbines produced by SLM Inconel alloys may also have excellent creep rupture strength and combine corrosion resistance and high strength with outstanding weldability including resistance to post-weld cracking [32]. The same Ni-based alloy has been produced by the LPF technology with a bit higher UTS (1240 MPa) and higher YTS (1133 MPa) which can give a better resistance to the stress loads imposed on the turbine impellers. Another Ni-based superalloy that can replace the Inconel alloys used nowadays by traditional manufacturing is the Rene88DT which is produced by LPF technology with outstanding mechanical results. After the final part is heat treated with HIP, its UTS can reach 1440 MPa and its YTS 1030 MPa (same as the YTS of Inconel 718). Rene88DT can provide exceptional resistance to higher loads at elevated temperatures [31]. The turbine housing and the center housing are made of Fe-based materials in order to withstand the extremely hot environment. More specifically, the turbine housing is commonly made of stainless steel which can deal with the elevated temperatures due to its low thermal property values (thermal conductivity and CTE – coefficient of thermal expansion) and especially its high melting point (>1400 ° C). Nevertheless, stainless steel (such as stainless steel 316) has been produced by the SLM and the LENS technologies resulting in higher mechanical properties values which can benefit both the turbine and the center housing. Stainless steel 17-4 has been developed by EOS GmbH which has 60 Application Case – Turbocharger showed great results in stress resistance (UTS 1000 MPa) produced by the DMLS technology. The shaft can also benefit from this type of stainless steel since it is subjected to high RPMs and temperatures. Parts with Al-based alloys have also been produced by SLM parts resulting in greater mechanical properties (see AlSi10Mg developed by EOS GmbH). These alloys can be used by the compressor impellers and housing. The bearing systems are commonly made of Cu-based alloys like leaded bronze or brass. The mechanical properties of leaded bronze are UTS=262 MPa, YTS=131 MPa and BE=18 %. Efforts have been made for the production of these metallic alloys by AM technologies. However, there is not adequate available information about the properties of Cu-based alloys manufactured by AM. According to literature Cu30Ni which is a Cu-based alloy produced by DMD technology gives sufficient mechanical properties; close to the conventional machined value for UTS (240 MPa), higher YTS value (317 MPa) and lower BE value (14 %). All of the parts of the turbocharger and especially the impellers that are subjected to high stress loads can take advantage of the Ti-based alloys. Ti6Al4V (or Ti64 called by EOS GmbH) is commonly used today by AM and due to the lower cost of titanium powder. Parts made of such alloy have been produced by different laser-based AM technologies such as SLM, LENS, LC and DMD with excellent results. In most of the cases the mechanical properties of Ti6Al4V are almost the same or even better comparing to the values of the same cast material. As a result the combination of great mechanical properties, high melting point, low thermal properties and the low cost of titanium powder make this Ti-based alloy an excellent candidate for the manufacturing of all of the parts of the turbocharger. For example, in case of the center housing the Ti6Al4V alloy can replace the aforementioned Febased alloys which are heavy and the components made of them add extra weight to the whole engine system. The center housing can take advantage of the freedom of design of AM combined with the thermal and mechanical properties of the Ti6Al4V as well as its lower weight (the density of Ti6Al4V alloy is 4.43 g/cm3; much lower comparing to 7.24 g/cm3 of cast iron). Lighter center housing can result in less weight in the engine and less weight load in the car (mostly for the racing cars) which means less fuel consumption together with less cost and more environmental friendly engines. The SLM technology has also achieved results with almost 100% density. 61 Application Case – Turbocharger 1400 1200 UTS (MPa) 1000 800 CM 600 AM 400 200 0 Inconel 718 Inconel 625 Stainless Steel 316 Ti6Al4V Figure 21: A comparative chart of the Ultimate Tensile Strength (UTS) of the metal alloys that have been manufactured by both Conventional Manufacturing (CM) and Additive Manufacturing (AM) and are applicable to the production of the turbocharger. For more detailed values of the properties of the materials mentioned above see Appendix 1and Appendix 2. Design optimization The major advantage of AM is the freedom of design since it offers the production of parts with unlimited geometry complexity. Today all the design constraints derived from all the production steps must be taken into consideration while designing a product. Manufacturing requirements and constraints are limits to the designers because they have to design the required product in a way that it won’t be hard to manufacture. With AM the only limitation is the designers’ imagination and the design tools. In addition, AM makes it possible to create features which are not possible by conventional method. A good example is the manufacturing of the center housing of the turbocharger. The most complex design part of the turbocharger belongs to the center housing. Because of the existence of cooling and lubrication channels the interior design of this housing is too complex for conventional methods. In fact AM can improve the cooling and lubrication system of the turbocharger by creating more complex channels inside the center housing part extracting more heat. This can be beneficial for the whole turbocharger efficiency. When traditional methods are applied such as sand casting, design limitations cannot be avoided. In order to get rid of the trapped sand, extra channels are needed. The process itself has design restrictions; the creation of thin sections is impossible, the design of the 62 Application Case – Turbocharger product is based on a pattern placed in sand to create the mold, the mold must also include extra channels in order to be filled with melted metal which is extra material used. An example of the freedom of design offered by AM for the turbocharger is the creation of a highperformance turbocharger with water-cooled casing and compressor impeller developed by MTU Friedrichshafen GmbH. The turbocharger is imposed to high thermal loads in operation. In order to decrease the surface temperature, MTU uses turbine and compressor housings with channels that enable water cooling, which simultaneously relieves some of the load on the intercooler. The size of the intercooler needed can be decreased and therefore the weight imposed on the car is decreased. This very complex design can be manufactured easier and with less cost and lead time by AM technologies.[54] Figure 22: High-performance turbocharger with water-cooled casing and compressor impeller developed by MTU Friedrichshafen GmbH [54]. Another example of design freedom is the creation of a turbocharger with variable turbine geometry (Figure 23). The power delivery and efficiency of the turbocharger can be improved with variable geometry of the turbine blades designed and manufactured by AM technologies. The exhaust passes over adjustable guides to the turbine blades so that the turbine spins quickly at low engine speeds and subsequently allows high exhaust gas flow rates. [54] 63 Application Case – Turbocharger Figure 23: Turbocharger with variable turbine geometry (VTG) Moreover, in order to cope with future tougher emissions standards a two stage turbocharging system is going to be needed. It is a system that ensures a constantly high rate of intake air delivery to the engine at all operating points and even under extreme ambient conditions. It involves precompression of the intake air by low-pressure turbochargers followed by further compression in high-pressure turbochargers. This system can be produced and designed by AM technologies with less leads time and cost comparing to current conventional manufacturing methods. [54] The turbine is not subjected to constant exhaust pressure. In diesel engines a turbocharger with twin-entry turbines can optimize the exhaust gas pulsations since higher turbine pressure ratio is reached in shorter time. Consequently a higher mass flow passes through the turbine with the result of the increased efficiency of the turbocharger. At low engine speeds the utilization of the exhaust gas energy and the engine’s boost pressure characteristics are improved. This is an example of design of turbocharger with twin-entry turbines designed by BorgWarner. This kind of design for the turbocharger can be manufactured easier by AM with less cost and lead time comparing to the conventional manufacturing that will need additional tooling, labor and time. [56] Figure 24: Turbocharger design with twin-entry turbines by BorgWarner [56]. 64 Application Case – Turbocharger AM makes possible the construction and manufacture of highly stable lightweight structures that cannot be produced using conventional production processes. Today it is necessary to consume as less resources as possible. The prices of resources are increasing every day as well as the raw material availability is decreasing. Products should use the absolutely essential resources in order to perform their function. This is an important issue of the product developers. AM offers maximum construction freedom to the developers and all kinds of detailed and complex lightweight structures can be manufactured. During the construction process the removal of unnecessary material is possible, thing that cannot be achieved when conventional manufacturing methods are applied. An example is the manufacturing of the center housing of the turbocharger. When traditional methods are applied such as sand casting, superfluous material cannot be avoided because of design limitations. The interior design of the center housing is very complex due to the existence of cooling and lubrication channels. For this complex design extra material may be used that is inevitable by the casting technique. In AM, material is only applied in those places where it is required for functional reasons. This results in extremely light weight and highly stable components. Life (Durability) While the car’s engine spins at between 2,000 RPM and 3,000 RPM at highway speeds, a turbocharger spins at as much as 100,000 RPM along with the fact that hot engine exhaust gasses flow through the turbocharger. Turbochargers are expected to last for the life of a vehicle. The major causes of turbocharger failures are attributed to lack of lube oil, restricted oil drainage, abnormally high exhaust temperatures or extreme mechanical conditions. Oil not only lubricates the turbocharger's spinning shaft and bearings, it also carries away heat. When oil flow stops or is reduced, heat is immediately transferred from the hot turbine wheel to the bearings, which are also heating up because of the increased friction due to the lack of oil. This combination causes the turbocharger shaft temperature to increase rapidly. If oil flow does not increase and the process continues, bearings will fail. Once the bearings fail (which can happen in just seconds) seals, shaft, turbine and compressor wheels can also be damaged resulting in reducing the life expectancy of the turbocharger. The principle causes of bearing lubrication problems, except for the human factor (improper machine start-up and shutdown procedure), can be low oil pressure due to a bent, plugged or undersized oil lube supply line, plugged or restricted oil galleries in the turbocharger. Restricted oil drainage is another fact for reducing the life of a turbocharger. The lubricating oil carries away heat generated by friction of the bearings and from the hot exhaust gases. If drainage back to the oil tank is blocked or slowed down, the bearings will overheat with damage that will 65 Application Case – Turbocharger ultimately lead to failure. This can be caused by a blocked drain tube or a restrictive design of drainage system. Abnormally high exhaust temperatures can cause cooking of oil which can lead to bearing failure. Extreme over-temperature operation can case wheel burst. Over-temperature is caused by either restricted air flow or overpowering the engine. In either case the engine has more fuel than available air for proper combustion, which leads to elevated exhaust temperatures. The restricted air flow can be caused by damaged or pure design of inlet piping, clogged air filters, excessive exhaust restriction, or operation at extreme altitudes. Overpowering is usually due to improper fuel delivery. Oil contamination can cause damage and reduce the durability of a turbocharger. It can be caused by worn or damaged oil filters or even by not changing the lube oil properly. Recycling and cleaning of the oil must be easily and frequently achieved by complex and accessible oil channels between the bearing system and the bearing housing. [53] A compressor’s mechanical performance is rated on whether or not it can deliver the expected service life. The stress on the compressor’s blades is proportional to the square of tip speed. [58] So if the compressor is required to run faster by applying extreme mechanical conditions, such as high altitudes, then development of designs with adequate life and robustness are essential in order to avoid damage of the turbocharger. AM technologies can minimize all the above mentioned causes of reduced turbocharger durability. For example, a different design of oil channels inside the center housing can improve the oil supply to the bearing system and help the lubrication of the bearings. Almost any complex design in any part of the turbocharger is easily achieved through layer-by-layer construction technologies. Either a more efficient lubricating system design or impellers design affect significantly the life of the turbocharger. Functional limits In general a turbocharger resides in a very hostile environment. The turbine wheel is driven by exhaust gasses that can exceed 1025°C. The rotor system on many turbochargers operates in excess of 100,000 RPM, and some approach 150,000 RPM. [46] That imposes huge tensile loads from the centrifugal forces, as well as bending and vibratory loads. This is the reason that nickel-based superalloys are required for this kind of environment. Those alloys can retain high strength values at these high temperatures with outstanding mechanical properties. They can withstand the high temperature of the exhaust gases with melting points between 1260°C and 1370°C and also act as heat insulators with low thermal conductivity values. 66 Application Case – Turbocharger The compressor side of a turbocharger faces its own challenges. The compressor is ingesting air at ambient temperature and with a 4:1 pressure ratio at 80% adiabatic efficiency (the ratio of the work input required to raise the temperature of the gas to the specified value to the actual work input), the compressor release temperature can exceed 205°C. [46] A compressor wheel is also subjected to tensile loads due to high centrifugal loads. High pressure ratios apply bending loads to the blades. Changing between pressure ratios of 1.0 (no boost) to 4.0 (max boost) and back applies large fatigue loads to the wheel. Most production compressor wheels are aluminum investment castings with high values of thermal conductivity, melting point that is above the compressed gas temperature and mechanical properties that can withstand the fatigue loads. So the temperature of the turbo environment also introduces a challenge to the center housing. If the engine is shut down immediately, the turbine and turbine housing temperatures are toward their upper limits, and suddenly all gas flow through the turbine stops and all oil flow through the center housing stops. All that heat must go somewhere, and an easy path is into the center housing. As a result the highest temperature gradient arises between the turbine housing and the center housing. [46] For the above reasons cast iron or stainless steel are used for the center housing because of their good mechanical properties (ultimate tensile strength ~500 MPa) and their low thermal conductivity (e.g. 16.9 W/mK of stainless steel) that can play the role of a heat insulator. Efficiency The purpose of a turbocharger is to force extra air into the combustion chamber of an engine so as to increase the engine’s efficiency and power. This improvement is achieved because the turbine can take advantage of the high energy from the exhaust gases and transfer that energy to the compressor which then forces more air, and proportionately more fuel, into the combustion chamber than atmospheric pressure alone. Also the European Commission policies demand reduced carbon dioxide (CO2) emissions from passenger cars. Cars are responsible for around 12 % of total EU emissions of CO2 which is the main greenhouse gas. European Union legislation sets mandatory emission reduction targets for new cars. This legislation is the basis of the EU's strategy to improve the fuel economy of cars sold on the European market. According to the European Commission for Climate Action: “The average to be achieved by all new cars is 130 g/km of CO2 by 2015 — with the target phased in from 2012 — and 95 g/km by 2021, phased in from 2020. The 2015 and 2021 targets represent reductions of 18 % and 40 % respectively compared with the 2007 average of 158.7 g/km. In terms of fuel consumption, the 2015 target is 67 Application Case – Turbocharger approximately equivalent to 5.6 l/100 km of petrol or 4.9 l/100 km of diesel. The 2021 target equates to approximately 4.1 l/100 km of petrol or 3.6 l/100 km of diesel”. [59] It is known that the operational performance of a car engine is influenced a lot by the turbocharger efficiency. For example, a turbocharger efficiency increase by 1 % under constant engine power can result in supercharged air pressure increase by 1 – 2 %, exhaust gas temperature decrease by 2 4 %, fuel consumption decrease by 0.6 – 0.8 % and CO2 emission decrease by 5 – 8 %. The turbocharger’s RPM influences significantly its overall efficiency. The current turbocharger average RPM is around 110,000 while the maximum turbocharger efficiency is around 160,000 RPM design which means that the turbocharger’s efficiency is less by approximately 32 % compared to the maximum efficiency. A more efficient design can help the increase of the RPM. For example by reducing the existing nozzle ring area of some turbochargers, it is possible to increase turbocharger RPM, boost pressure, air flow to the cylinders and turbocharger efficiency simultaneously. This should result in reduced exhaust gas temperature and fuel consumption. M.A. Turbo/Engine Ltd. in cooperation with Vicmar Engineering Ltd. has already introduced the turbo nozzle ring modification to engines worldwide with satisfactory results. The fuel consumption was decreased by maximum 5 % and fuel temperature was also decreased by maximum 15 %. The reduced fuel consumption and the reduced fuel temperature mean that the CO2 emissions will be reduced significantly. Due to reduced exhaust gas temperature the lifetime of the turbocharger should be longer with less maintenance costs. The thermal stresses can also be decreased due to reduced gas temperature which means that there is no possible danger to the ordinary turbocharger operation. However, this modification of an existing nozzle ring area or even the addition of the nozzle ring to a turbocharger can increase its production cost. [60] Process consolidation Many manufacturing processes force the use of numerous processes because they do not have capacity for certain types of complexity. On the other hand, AM gives the opportunity to dispose of post processes which aim to either subtract or add material. Process consolidation reduces assembly and subtractive processes, tooling, inventory, waste and inspection costs. With AM’s high flexibility in geometric complexity design, any shape is possible in one single built which means less labor, less cycle time and more production flexibility. Part consolidation, a district characteristic of AM, finds application on the process consolidation of the production of the turbocharger. The original design of the turbocharger consists of multiple parts. With AM the production of all these parts can be achieved even in one single built. The product can be produced as it’s assembled so the production of sub products is not needed. Parts 68 Application Case – Turbocharger can be combined into a single part; a part that would not be possible to make with conventional manufacturing techniques. A good example is the development as a single part of the shaft and the turbine impeller which are two components that are made separately and then assembled together by conventional manufacturing. The number of parts in the bill of materials can be noticeably reduced. AM eliminates also the need of material removal processes. A higher level of synthesis is achieved in a single unit process. For instance in the conventional machining, removal of material is required for the complex design of the center housing while layer-by-layer fabrication can provide simplified lower-cost manufacturing in one single process. Holes, cavities and other subtractive features are formed during the single AM process of construction of the component. Tooling for the production of each of the parts, inspection, human hands or extra technology needed is eliminated by AM. In this way the cost and the lead time are extensively reduced. Production cost Some of the parts of the turbocharger such as the housings are manufactured using the sand casting process. This is a metal casting process characterized by using sand as the mold material. Sand casting is relatively cheap. One piece products of complex shape can be made at moderate cost and in large quantities. However the sand casting process is not as accurate as other casting processes like investment casting, either dimensionally or in terms of surface finish; secondary machining often is required. High porosity is possible with a resulting of poor material strength. Moreover the most common method of producing compressor impellers is the plaster mold casting. Plaster mold casting is a metalworking casting process similar to sand casting except the molding material is plaster instead of sand. This process is used when an excellent surface finish and good dimensional accuracy is required. Because the plaster has a low thermal conductivity and heat capacity the metal cools more slowly than in sand mold, which allows the metal to fill thin crosssections; the minimum possible cross-section is 0.6 mm. This results in a near net shape casting, which can be a cost advantage on complex parts. Nevertheless this process can only be used with lower melting temperature non-ferrous materials as in this case of the aluminum compressor impellers (maximum working temperature of plaster is 1,200 °C). Long cooling times are needed and strict monitoring as well as skilled labor is essential for the reason that the plaster is not as stable as the sand. Those factors increase the production cost of the plaster mold casting process used for the compressor impellers. 69 Application Case – Turbocharger On the other hand the turbine impellers require better accuracy than the housings so a high strength investment casting process that takes place in vacuum is used. Investment casting is an industrial process based on and also called lost-wax casting. It is generally more expensive per unit than die casting or sand casting, but has lower equipment costs. It can produce complicated shapes such as the turbine blades that would be difficult or impossible with other casting techniques. Accuracy and surface finish are so good that sometimes additional machining is unnecessary. Investment casting is also very useful when dealing with difficult materials like the nickel-based superalloys. For the case of the turbine impellers vacuum investment casting uses gas pressure and a vacuum to improve the quality of the casting and minimize porosity. In this way the process becomes more complex overall involving many steps, increasing cost and manufacturing time. Highly skilled labor is required making the process even more expensive. Mould materials are costly and even though the wax is reusable, the investment is not. Long lead time is also possible which means more production cost. Because of the above reasons the production of the turbine impellers is the most expensive. [61] Recyclability In general, the metal casting methods that are commonly used for the production of the turbocharger parts have serious environmental impacts. Some of these issues are emission of harmful and poisonous gases, dust and particles and generation of waste pollutants. Hazardous Air Pollutants (HAP) include gases that are generated when molds containing carbon materials are subjected to high temperatures as happens in the pouring of cast metals. A lot of sand is reused by the sand casting method used for the production of the housings. However, heat and mechanical abrasion eventually make the sand unsuitable for use in casting molds, and a portion of the sand is continuously removed and replaced with virgin sand. It is estimated that only 15% of the annually generated sand is recycled and reused. [62] Investment casting or lost wax casting process uses wax to make patterns for the manufacture of the impellers. At the end of the process, the wax is collected for reuse. The collected wax is filtered and tested for proper properties but it is a usable product after excess water is removed from the autoclave processing. The structural and chemical integrity of the pattern wax are consistent even after repetitive reuse. [63] AM includes environmental friendly ways of manufacturing that produce less waste and result in less packaging and transportation. Parts can be manufactured in distributed workhouses with AM saving in transport from distant factories. It is obvious that the additive methods of AM produce much less waste comparing to the subtractive methods. Many AM technologies are more than 95% material 70 Application Case – Turbocharger efficient in terms of reusability and recyclability. However, there are some methods that require support material which generates waste. Moreover the production by AM technologies can be widely distributed. The customer can order a product and the manufacturer can produce the same product in multiple locations. This fact increases the cost of having same tooling and machines in different locations for conventional manufacturing. But this extra cost does not apply to AM because tooling in not required. As mentioned previously, an optimized product may be a lighter product or a better featured product which results in decrease of energy and less natural resources consumption. Conventional metal casting methods AM HAP emission Less waste Generation of dust and particles Less packaging and transportation Generation of waste pollutants Needs supports (waste) Natural resources consumed Less natural resources consumed 15% of annually generated sand is reused 95% of the material powder is reused Table 8: Characteristics of conventional metal casting methods and AM. 4.6.3 Alternative AM Developments It is time to pick the most critical alternative according to the above criteria. However, criteria such as variety of material properties and process customization have not been taken into consideration. This analysis includes seven criteria and six alternatives as it is shown in Figure 25: Objective • Select critical part of turbocharger Criteria • Size •Design Optimization Alternatives •Turbine Impeller & Shaft •Life •Compressor Impeller •Functional Limits •Center Housing •Efficiency •Bearing System •Process Consolidation •Turbine Housing •Production Cost •Compressor Housing •Recyclability Figure 25: Lists of the parameters of the objective, the criteria and the alternatives used for the criticality analysis. 71 Application Case – Turbocharger Turbine impeller and shaft For the turbine impeller there is higher need for improvement concerning the criteria of functional limits, production cost, process consolidation and design optimization. According to literature for the development of this part with AM the technology and the material used are: LPF technology Inconel 718 This material powder is also used for the conventional manufacturing of the turbine impellers. This technology gives better mechanical properties and the LPF machine is cheaper than the SLM machine. The statements for development of the turbine impeller and shaft with AM are: An optimized design by AM can respond to extreme conditions, avoiding any possible damage and increasing the life of the turbocharger. The higher mechanical properties of Inconel 718 produced by the LPF machine can improve the resistance of the turbine impellers. A different design of the impellers produced by AM can increase the RPM and improve the efficiency of the turbocharger. AM can reduce the production cost of the turbine impellers by reducing the lead time and even using cheaper equipment compared with the expensive and complicated vacuum investment casting. The welding process of the turbine impeller and the shaft can be subtracted with AM. The freedom of design of AM can optimize the performance of the turbine impellers with a more complex design of the impellers. Compressor Impeller For the compressor impeller there is a higher need for improvement of its design. Most of the rest of the criteria need to be improved as well. The following technology and material are chosen for the development of the compressor impeller with AM: SLM technology AlSi10Mg (EOS GmbH) This Al based alloy gives almost similar or even higher mechanical values compared with cast Al based alloys used for the production of the compressor impellers. (Appendix 1 and Appendix 2) 72 Application Case – Turbocharger The statements for development of the compressor impellers with AM are: An optimized design by AM can respond to extreme conditions, avoiding possible damage and increasing the life of the turbocharger. The higher mechanical properties of AlSi10Mg by SLM machine can improve the resistance of the compressor impeller against the tensile loads imposed by the high centrifugal loads and the bending loads caused by high pressure ratios. A different design of the impellers produced by AM can increase the pressure ratio and improve the efficiency of the turbocharger. AM can reduce the production cost with less lead time, less tools and cheaper equipment comparing to the investment casting. The freedom of design of AM can optimize the performance of the compressor impellers with a more complex design of the impellers. Center housing Improvement of the center housing is needed concerning all the criteria. The technology chosen and the material that replaces the cast iron are: SLM technology Stainless steel 316L The stainless steel 316L produced by SLM technology has great results in stress resistance (UTS = 826 MPa). (Appendix 2) The statements of development for the center housing are: AM offers a more optimized design to the center housing in order to avoid damage caused by a weak lubrication or cooling channel system and reduce maintenance costs. As a result, the life of the turbocharger is increased. The great mechanical properties of stainless steel 316 improves the resistance of the center housing and can isolate heat due to its low thermal properties in case of a sudden shut down of the engine or even a failure that will force all the heat and stresses to the center housing. Concerning the need for increased efficiency of the turbocharger, AM can improve the lubrication and cooling of the shaft and bearings with an optimized design of the interior of the center housing in order to increase the RPM. AM can reduce the production cost with reduced lead time, less tools, less processes and less human hands. 73 Application Case – Turbocharger A center housing manufactured by AM needs less post processes than the one manufactured by sand casting. The freedom of design of AM can optimize the internal structure of the center housing and increase its performance. A center housing produced by AM is “greener” since the sand casting process produces a big amount of sand that is not recycled. SLM technology can create a component of center housing with around 50 % solidity reference compared to the original part created by sand casting. The material that is added in places of the component that are not functional can be avoided. For conventional manufacturing this thing can be very difficult or even impossible compared to the SLM technology that can avoid fusing material at the non-functional places. Bearing system The bearings can be manufactured by AM using the following technology and material: DMD technology Cu30Ni There is not adequate information about Cu-based alloys developed by AM. Although the Cu30Ni produced by DMD technology gives satisfactory mechanical properties close to the conventionally machined Cu-based alloys. (Appendix 1, Appendix 2) The statements of the development of the bearing system are: ΑΜ can offer a more optimized design to help the lubrication of the system and increase the life of the turbocharger by avoiding potential damage. However, the production of the bearings with the expensive DMD machine comparing to the cheaper traditional machining with a five axis machine can increase the total fixed production cost. Turbine Housing Need for improvement for the turbine housing is focused on the functional limits, the efficiency of the turbocharger, the design optimization and especially the recyclability. According to the literature the following technology and material are chosen for the development of the turbine housing with AM that can replace the sand casting with cast stainless steel: DMLS technology Stainless steel 17-4 (EOS GmbH) 74 Application Case – Turbocharger The stainless steel 17-4 developed by EOS GmbH has great results in stress resistance (UTS = 1000 MPa) and can deal with the high temperature of exhaust gases inside the turbine housing with its low thermal properties values. (Appendix 1, Appendix 2) The statements of development are the following: An optimized design by AM can respond to extreme conditions and increase the life of the turbocharger. The higher mechanical properties of stainless steel 17-4 can be beneficial in case of higher demands for mechanical resistance of the turbine housing. An optimized design by AM can increase the air flow input of the turbine housing resulting in increased RPM and greater performance of the turbocharger. A DMD machine can increase the production cost of this component compared with the cheaper sand casting method. The freedom of design of AM can optimize the design of the turbine housing resulting to optimized performance. The DMD technology is more environmental friendly compared with the sand casting process. Compressor Housing For the compressor housing, improvement is needed concerning its design, efficiency and recyclability. According to the literature the following technology and material are chosen for the development of the compressor impeller with AM: SLM technology AlSi10Mg (EOS GmbH) This Al based alloy gives similar or even higher mechanical values compared with cast Al based alloys used for the production of the compressor housings. (Appendix 1 and Appendix 2) The statements for development of the compressor housing with AM are: An optimized design by AM can respond to extreme conditions and increase the life of the turbocharger. The high mechanical properties of AlSi10Mg can resistance of the compressor housing in case of higher demands for mechanical. An optimized design of compressor housing by AM can increase the pressure ratio of the compressor resulting in higher performance of the turbocharger. 75 Application Case – Turbocharger An SLM machine can increase the production cost of this component comparing to the cheaper sand casting method. The freedom of design of AM can optimize the design of the compressor housing resulting in optimized performance. The SLM technology is more environmental friendly comparing to the sand casting process. 4.6.4 Method The three primary core steps involved in the criticality analysis for the development of the turbocharger components through AM production are: Identifying value of criteria A technical survey addressed to specialists (population > 30) in Production Engineering field was the main source of gathering the assets of an ICE device and quantifying the importance of improvement for each one. Each of the Criteria (i) is characterized as Low (0), Average (1.5) and High (3) importance for the contribution to the efficient production of a turbocharger. “From the production aspect, how would you evaluate the importance of the following criteria for the improvement of the Turbocharger?” Criteria Low Average High Size 27.3% 40.9% 31.8% Design optimization 13.6% 63.6% 22.8% Life 4.5% 50.0% 45.5% Functional limits 0.0% 59.1% 40.9% Efficiency 4.5% 18.2% 77.3% Process consolidation 13.6% 45.5% 40.9% Production cost 9.1% 18.2% 72.7% Recyclability 18.2% 54.5% 27.3% Table 9: Results from the survey. The survey results generate the mean value in a scale [0, 3]. Normalizing the mean values of each criterion in an overall Value (Vi) scale [0, 1], the Max value is set as 1 and the Min value as 0. Normalization “0 1” is a feature scaling used to bring all values into the range [0, 1] according to the following equation: 76 Application Case – Turbocharger The results of the values (Vi) are presented in the Table 10. Survey Mean Value (SMVi) Value (Vi) Size Design optimization Life Functional limits Efficiency Process consolidation Production cost Recyclability 2.05 2.09 2.41 2.41 2.73 2.27 2.64 2.09 0 0.06 0.53 0.53 1 0.32 0.87 0.06 Table 10: Criteria value scale. Rating the need of improvement Literature on the lifespan, failure causes, production and operation efficiency of every turbocharger component (j), was the main source to identify points which require further improvement. According to every criterion the need of component improvement is characterized as high (10), low (5) and neutral (0) important. The final value-added ranking of the need of the improvement (aij) is generated by multiplying the criteria’s value (vi) by the ranking of the need of the improvement. The sum of value-added ranking for each turbocharger component (j) is divided by the overall turbocharger sum generating a percentage factor (αj) which indicates the contribution need of improvement of the sub system (component) to the entire system (turbocharger). The results are presented in the Table 11. Rating the development of AM production The research investigates the development of each turbocharger component (j) developed by AM technologies. In other words, the aim is to quantify the results of AM components production compared with the overall efficiency. The investigation is based on estimations from literature and case studies of AM. The principal aforementioned statements in every turbocharger component AM development alternative related to each criterion (i) are ranked in a scale (–2, –1, 0, 1, 2). The negative ranking indicates an inferior result of component development, the positive the superior results and zero is the non development either positive or negative. The final value-added ranking of AM development statement (bij) is generated by multiplying the criteria’s value (vi) by the ranking of the AM development statement. The percentage factor (βj) which indicates the contribution development of the subsystem (component) to the entire system (turbocharger) is calculated and is presented in Table 12. 77 Application Case – Turbocharger Table 11: Ranking the need for improvement Design optimization Value [0,1] 0.32 0.87 0.06 High Low High Low High High Low 10 5 10 5 10 10 5 0.59 2.65 5.29 5.00 3.24 8.68 0.29 High Low Low Low Low Low Low 10 5 5 5 5 5 5 Value added Ranking 0.59 2.65 2.65 5.00 1.62 4.34 0.29 Need for Improvement High High Low High Low High High 10 10 5 10 5 10 10 0.59 5.29 2.65 10.00 1.62 8.68 0.59 Neutral High Low Low Low Low Neutral 0 10 5 5 5 5 0 Value added Ranking 0.00 5.29 2.65 5.00 1.62 4.34 0.00 Need for Improvement Low Neutral Low Low Neutral Low High 5 0 5 5 0 5 10 Value added Ranking 0.29 0.00 2.65 5.00 0.00 4.34 0.59 Need for Improvement Low Neutral Neutral Low Neutral Low High 5 0 0 5 0 5 10 0.29 0.00 0.00 5.00 0.00 4.34 0.59 Value added Ranking Need for Improvement Ranking (0,5,10) Ranking (0,5,10) Value added Ranking Need for Improvement Ranking (0,5,10) Ranking (0,5,10) Compressor housing Ranking (0,5,10) Value added Ranking Turbocharger System 78 cost Recyclability 1.00 Ranking (0,5,10) Turbine housing consolidation Production 0.53 & shaft Bearing system Process 0.53 Need for Improvement Center housing limits Efficiency 0.06 Turbine impeller Compressor impeller Functional Life Overall Ranking Sum Need Contribution Factor (αj ) 25.74 23% 17.13 15% 29.41 26% 18.90 17% 12.87 11% 10.22 9% 114.26 100% Application Case – Turbocharger Table 12: Ranking the statements of development Design optimization Value [0,1] Turbine impeller & shaft Compressor impeller Center housing Bearing system Turbine housing Compressor housing Turbocharger System 79 Development 0.06 Optimize performance Functional limits Life Efficiency 1.00 Process consolidation Production cost 0.32 Subtract welding assembly 0.87 0.06 Reduce lead time No improvements Recyclability 0.53 Respond to extreme conditions 0.53 Higher mechanical properties 1 1 1 2 2 0 Increase RPM Rating (–2, –1, 0, 1, 2) 1 Value added Ranking 0.06 0.53 0.53 1.00 0.65 1.74 0.00 Optimize performance Respond to extreme conditions Higher mechanical properties Increase pressure ratio No improvements Reduce lead time No improvements Rating (–2, –1, 0, 1, 2) 1 1 1 1 0 1 0 Value added Ranking 0.06 0.53 0.53 1.00 0.00 0.87 0.00 Optimize internal structure Avoid damage/Reduce maintenance Higher mechanical properties Improve lubrication/cooling system Subtract post processes Reduce lead time Recycled powder Rating (–2, –1, 0, 1, 2) 2 2 1 2 1 1 2 Value added Ranking 0.12 1.06 0.53 2.00 0.32 0.87 0.12 No improvements Improve lubrication No improvements Reduce friction No improvements Increase Total Cost No improvements Rating (–2, –1, 0, 1, 2) 0 2 0 1 0 -2 0 Value added Ranking 0.00 1.06 0.00 1.00 0.00 -1.74 0.00 Optimize performance Respond to extreme conditions Respond to higher demands Increase air flow No improvements Increase Total Cost Recycled powder Rating (–2, –1, 0, 1, 2) 1 1 1 1 0 -1 2 Value added Ranking 0.06 0.53 0.53 1.00 0.00 -0.87 0.12 Optimize performance Respond to extreme conditions Respond to higher demands Increase pressure ratio No improvements Increase Total Cost Recycled powder Rating (–2, –1, 0, 1, 2) 1 1 1 1 0 -1 2 Value added Ranking 0.06 0.53 0.53 1.00 0.00 -0.87 0.12 Development Development Development Development Development Overall Ranking Sum Development contribution factor (βj) 4.50 29% 2.99 19% 5.01 32% 0.32 2% 1.37 9% 1.37 9% 15.56 100% Application Case – Turbocharger The final results of criticality analysis are summarized in a final table which indicates the objective of the analysis, the most critical turbocharger component developed by AM technologies. The final table is a third ranking system that provides the feasibility of the turbocharger components AM development related from one side to the need for improvement and from the other side from the contribution to the overall turbocharger system. Therefore the rank (Xij) of a turbocharger component (j) related to a criterion (i) has the following equation: Xij = Nij + Cij (1) Where Nij is the feasibility of the turbocharger component (j) development related to the need of improvement and Cij is the feasibility of the turbocharger component (j) development related to contribution to the overall turbocharger system. The feasibility related to the need of the improvement is given by the equation: Nij = Bij × Aij × αj (2) Bij is the value-added rank of AM development statement for a turbocharger component (j), Aij is value-added rank of the need for the improvement for a turbocharger component (j) and αj is the overall turbocharger system factor of the need for the improvement. The feasibility related to the contribution to the overall turbocharger system is given by the equitation: Cij = Bij × βj (3) βj is the overall turbocharger system factor of the development of a turbocharger component (j). Every rank Bij which is referred to a certain subsystem (turbocharger component) should be affected from the contribution to the entire system (turbocharger). From eqs. (2) and eq. (3) the (1) is re-written as following: Xij = Bij × Aij × αj + Bij × βj (4) Xij = (Aij × αj + βj) × Bij (5) Therefore: Finally the max of sums (Wj) of the ranks Xij of every component indicates the most critical turbocharger component (j) which contributes most in the efficient production of the turbocharger system. In other words it points out the development of the manufacturing process through the use of AM technologies for a certain component as the most effective comparing to the others. 80 Application Case – Turbocharger Criteria Turbine impeller & shaft Compressor impeller Center housing Bearing system Turbine housing Compressor housing Design optimization 0.02 0.02 0.06 0.00 0.01 0.01 Life 0.47 0.42 1.78 0.95 0.05 0.05 Functional limits 0.78 0.73 0.53 0.00 0.20 0.05 Efficiency 1.42 1.32 5.79 0.85 0.65 0.54 Process consolidation 0.66 0.00 0.24 0.00 0.00 0.00 Production cost 3.89 1.86 2.22 -1.28 -0.50 -0.41 Recyclability 0.00 0.00 0.06 0.00 0.02 0.02 Sum (Wj) 7.24 4.35 10.68 0.52 0.43 0.24 Table 13: Overall selection development matrix. According to the results from the Table 13 the most critical component for the development of the turbocharger with AM is the center housing. Based on the above and the AM development statements, the development of the center housing manufactured by the SLM technology (AM250 machine by Renishaw) with stainless steel 316L as material powder is more critical to the development of the turbocharger’s production and can increase the life of the turbocharger, offer higher resistance to mechanical loads, isolate heat in case of failure, increase the efficiency of the turbocharger, reduce the waste in production, optimize the design, use less resources and reduce the impact on the environment. 81 Application Case – Turbocharger 4.7 Sustainability Analysis Sustainable development is an important issue for human development and a significant prerequisite for human activity. The sustainable development includes the view that social, economic and environmental matters should be addressed simultaneously and holistically in this process (Figure 26). Sustainability is addressed to many fields including manufacturing. According to the World Commission on Environment and Development (WCED) the sustainable development is defined as a development that “meets the needs of the present without compromising the ability of future generations to meet their own needs”. Protection of environment and natural resources Environmental Incentives and taxes/penalties to promote efficiency, environmental stewardship Sustainability Social Economic Business ethics, fair trade, social responsibility, worker protections Figure 26: Sustainability as the intersection of its three key parts, and examples of features at the intersection of any two parts. Sustainable manufacturing is the link between manufacturing and its operations to the natural environment. Nowadays manufacturing organizations consider profitability, productivity, progress and environmental stewardship. Environmental stewardship is the responsible use and protection of the natural environment through conservation and sustainable practices. The US Department of Commerce defines the sustainable manufacturing as “the creation of manufactured products that use processes that minimize negative environmental impacts, conserve energy and natural resources, are safe for employees, communities, and consumers and are economically sound” [64]. 82 Application Case – Turbocharger Companies have developed and applied various approaches for integrating sustainability into industrial operations. One of them is the “triple bottom line” method which is invented by John Elkington during the mid-1990s. The Triple Bottom Line (TBL) is a framework that incorporates three dimensions of performance: social, environmental and financial and is adopted by many businesses. The TBL is also called the 3Ps: planet, profit, people and they are referred as the “three pillars of sustainability” [65]. Planet refers to sustainable environmental practices such as the waste management, the resource consumption, the land use etc. “Cradle-to-grave” analysis is in the thoughts of TBL manufacturing businesses and is performed through a life cycle assessment of products to determine what the true environmental impact is from the production, use and disposal of a product. Profit is the economic value of the TBL. This refers to the internal profit made by the company. People refer to things like fair trade, employee welfare, safety hazards, labor exploitation etc. The ways that the company’s choice will affect the employees, consumers and the community that they exist. Figure 27: Triple Bottom Line graphic 83 Application Case – Turbocharger 4.7.1 Life Cycle Assessment (LCA) Life Cycle Assessment (LCA), also known as Life Cycle Analysis is a technique to assess environmental impacts associated with all the stages of a product's life from raw material extraction through materials processing, manufacture, use, and disposal or recycling (cradle-to-grave analysis). Primary Resource Acquisition End-ofLife/Recycling Raw Material Processing Use Manufacturing Figure 28: General Life-Cycle Stages of a Product or System According to ISO 14040.2: “Life Cycle Assessment (LCA) is a technique for assessing the potential environmental aspects and potential aspects associated with a product (or service), by: compiling an inventory of relevant inputs and outputs, evaluating the potential environmental impacts associated with those inputs and outputs, interpreting the results of the inventory and impact phases in relation to the objectives of the study.” There are many software tools that can be used to calculate the environmental impact of the stages of a product. Some of most known software is SimaPRO, Gabi, OpenLCA etc. However, the use of the conventional manufacturing database is not free and no database for AM processes exists yet. The LCAs are also too time-consuming and complex with results of discreet effect scores that are difficult to interpret. This is why the National Reuse of Waste Research Programme (NOH) carried out and financed the Eco-indicator project. The Eco-indicator values are intended to be applied by designers and product managers for the assessment of environmental aspects of product systems. The Standard Eco-indicators are numbers that express the total environmental load of a product or a process. These indicators are found in the “Eco-indicator 99 Manual for Designers, a damage oriented method for life cycle impact 84 Application Case – Turbocharger assessment”, published by Ministry of Housing, Spatial Planning and the Environment, in Netherlands, in October 2000. The Eco-indicator methodology conforms well to the ISO 14042 standard on life cycle impact assessment. Every product damages the environment to some extent from the extraction of raw material to the manufacture of the product, the distribution, the use and its disposal. The Eco-indicators of the most common processes of the abovementioned have been calculated and they are numbers which indicate the environmental impact of these processes based on data from a life cycle assessment. The higher the indicator is, the greater the environmental impact. The term “environment” in the Eco-indicator 99 is defined with three types of damage categories; the human health that includes the number and duration of diseases and life years lost due to premature death from environmental causes such as climate change, ozone depletion, radiation, carcinogenic effects; the ecosystem quality that includes the effect on species diversity such as ecotoxicity, acidification, eutrophication and land-use; and the resources that include the surplus energy needed in future to extract lower quality mineral and fossil resources. Still, there are damage categories like the damage to material welfare or the damage to cultural heritage that are not included in the Eco-indicator values. The standard Eco-indicator values are regarded as dimensionless figures. As a name the Eco-indicator point (Pt) is used. The unit millipoint (mPt) is used (so 100 mPt = 0.1 Pt). The scale is chosen in such way that a value of 1 Pt is representative for one thousandth (1 kPt) of the yearly environmental load of one average European inhabitant [66]. Standard Eco-indicator 99 values are available for: The production processes of different materials that include all the processes from the extraction of the raw material up to and the last production stage resulting to a final product material. These indicators are based on 1 kg material. The treatment processes that include the emissions from the process itself and emissions from the necessary energy generation processes. These indicators are based on 1 kg material. The transport processes which include the impact of emissions caused by the extraction and production of fuel and the generation of energy from fuel during the transportation. These indicators are based on 1 tkm. The energy indicators take account of the extraction and production of fuels and the energy conversion and electricity generation. The electricity indicators are based on 1 kWh. 85 Application Case – Turbocharger The indicators for the disposal or recycling scenario are based on waste handling in Europe. Scenarios are provided for different materials for the incineration, landfill disposal, recycling of products, household waste and municipal waste. These indicators are based on 1 kg material. Some disposal scenarios contain negative figures because in some cases the energy and material flows can be recycled and reused and are regarded as an environmental profit. For the purposes of this study, the method of Eco-indicator 99 has been used in order to estimate the Environmental Impact (EI) of the manufacturing of a turbocharger with conventional technologies (original scenario) and the EI of the same turbocharger with the only difference that its center housing is manufactured by AM using Stainless Steel 316L and the AM250 machine by Renishaw (development scenario). The purpose is to compare the EI of these two turbochargers. The process tree of the original scenario is illustrated in Figure 29.The amounts of the materials are also included in the process tree. The process of each material includes all processes from the extraction of the raw material up to and the last production stage of the product. The white blocks in the figure have been disregarded in the Eco-indicator calculation. The packaging and transportation have been omitted. All of the components of the turbocharger are produced by conventional manufacturing processes. Another process tree is illustrated in Figure 30 which includes the development scenario. 86 Application Case – Turbocharger Inconel 0,07 kg Steel 4140 0,06 kg Al C355 0,03 kg Machining Cast Iron 1,22 kg Brass 0,05 kg Machining Machining Cast SS 2,05 kg Cast Al 0,52 kg Welding Assembly/ Transport Packaging Use Incineration Steel 22 % Landfill Steel 78 % Fuel Oil Incineration Al 22 % Landfill Al 78 % Figure 29: Original Scenario; process tree of a turbocharger with amounts and assumptions. Conventional manufacturing (casting) is used for the production of each component. The white boxes are not included in the analysis Inconel 0.07 kg Steel 4140 0.06 kg Al C355 0.03 kg Machining SS 316L 0.51 kg Brass 0.05 kg SLM AM250 Machining Cast SS 2.05 kg Cast Al 0.52 kg Welding Assembly/ Transport Packaging Fuel Oil Use Incineration Steel 22 % Landfill Steel 78 % Incineration Al 22 % Landfill Al 78 % Figure 30: Development Scenario; process tree of a turbocharger with amounts and assumptions. AM (SLM technology) is used for the production of the center housing. The white boxes are not included in the analysis. 87 Application Case – Turbocharger The amounts of the materials are derived from the design specifications using the CAD model of each component. SolidEdge software has a wide library of materials and its properties. However, some properties of the alloys used did not agree with the values derived from the literature or they were not even included in the library. So some configurations of existing materials and creation of new materials have been made in the library of materials of SoliEdge in order to apply each material to each component respectively. Then the software calculates the volume of each component and through the density of the material, the mass of each component is calculated. Weighing of real turbocharger components has been performed so as to validate that the values for the mass of the software are close to the realistic ones. The Eco-indicators of the production of the components are based to mPts per 1 kg so the mPts of each process is calculated by multiplying the indicator by the mass of each material. The Eco-indicator 99 includes only indicator values for the production of commonly used metallic materials. For that reason it has been assumed that the alloys used for the production of the turbocharger have the same indicator values with the base metallic materials (Table 14). For the center housing manufactured by sand casting, calculation of the scrap material for the holes was needed in order to be added to the final mass of the material needed for this process. With the help of SoliEdge the volume of the holes is calculated and consequently the mass of the scrap (for details see Appendix 3) Material Inconel 713C Steel 4140 Aluminum C355 Cast iron Brass Austenitic stainless cast steel Cast aluminum Stainless steel 316L (powder) Material in Eco-indicator Indicator (mPts/kg) Nickel 5200 Steel low alloy 110 Aluminum 780 Cast iron 240 Copper 1400 Cast iron 240 Aluminum 780 Steel 86 Table 14: The Eco-indicator values of the materials that were chosen for the materials used for the manufacture of the components of the turbocharger For the use of the turbocharger, fuel oil is needed. The maximum oil consumption of the turbocharger on 100% load is 0.4 g/h according to Delta Services Industriels (DSI) [67]. It is assumed that the life of the turbocharger is 15 years. Along with the “Statistiska centralbyrån – Statistics Sweden” the average speed of a passengers car is 50 km/h and the average distance per year is 15000 km. As a result the oil consumption is calculated to 0.12 kg/year and 1.8 kg for 15 years. 88 Application Case – Turbocharger Assumptions are also made about the disposal scenarios. The turbocharger is disassembled and the components are either incinerated or land filled. According to Eco-indicator Manual the common scenario for disposal in Europe is 22% incineration and 78% landfill for the metals. The manual includes only values of indicators for the disposal of steel and aluminum. Data is missing for the disposal of the rest of the materials. The second life cycle scenario is the same except for the fact that the SLM machine AM250 by Renishaw is used for the manufacture of the center housing instead of sand casting. The “cast iron” process and the “machining” process are replaced by the “Stainless Steel 316L” process (the production of powder material that is needed for the SLM machine) and the “SLM250” process that represents the production of the final component by SLM. The mass input for both processes is half of the material input for sand casting since SLM can produce a 50% less dense part with just the necessary functions. However, the Eco-indicator manual does not contain any indicators for any AM technologies so the Eco-indictor of the AM250 machine must be calculated. A study performed at Loughborough University on the AM250 SLM machine by Renishaw (the study uses the former name MTT SLM 250 of the same machine) using the Stainless Steel 316L powder calculates the power consumption of the machine. The study focuses on the electrical consumption of the machine during the process. The average energy consumed per kg is calculated to 31 kWh [68]. Moreover, the EI of the AM250 machine is evaluated according to the following equation: Where ECR is the Energy Consumption Rate or massive energy use during the process such as: And (=10 mPts/kWh) is the indicator which allows to convert a massive energy (ECR) to an environmental impact per kg express in mPts/kg. In the above equation, power consume by the laser during manufacturing (in W), kg/h), represents the electric represents the process productivity (in represents the quantity of powder fused per hour (in cm3/h) and is the density of 3 the material (in kg/cm ) [69]. Consequently, since the ECR is 31 kWh/kg, the EI of the AM250 machine using Stainless Steel 316L as a powder material is calculated to 310 mPts/kg. This value is used as the Eco-indicator of the “SLM 250” process. 89 Application Case – Turbocharger The table can now be filled in for each phase in the life cycle and the relevant Eco-indictor values can be recorded. The score is then calculated for each process and recorded in the “result” column. The results of the EI of each phase are added and result in the total EI of the life cycle of the turbocharger. The Table 15 shows the EI (mPts) calculated for every phase of the life cycle of the turbocharger together with the sum of them compared with the EI. The fully completed forms of both life cycles of the turbocharger can be found in the Appendix 4 and Appendix 5. Phase Original Scenario Development Scenario Production 1698.045 1575.513 Use 324.000 324.000 Disposal -32.319 -28.524 1989.726 1870.989 Total Table 15: The EI (in mPts) for each phase for both of manufacturing scenarios of the turbocharger. The phase of the production of each component has obviously the greatest impact on the environment. The development of the turbocharger with the production of the center housing by SLM technology reduces the EI from 1989.726 mPts to 1870.898 mPts. So the EI of the small change in the production of just the manufacture of the center housing with AM contributes to about 6 % less impact on the environment. It is significant that there are material production processes in the life cycle of the turbocharger that contribute a lot to the total EI of the production phase. For instance, for the production process of the Inconel 713C, even though a small amount of material is used (0.07 kg) the EI is high (374.400 mPts) because of the high value of the Eco-indicator (5200 mPts/kg). The production of the Austenitic Cast Stainless Steel needs a big amount of material (2.05 kg) that contributes to a high EI value (492.480 mPts) of the production phase of the turbocharger. The production of the components that use the abovementioned material by an AM technology which less EI is more advantageous for the environment. A comparative Chart 2 illustrates the EI of the total life cycle of the turbocharger for both scenarios and the EI of just the phase of the production of the components of the turbocharger for both scenarios. 90 Application Case – Turbocharger Environmental Impact of TC 2500 2000 Center Housing Conventional Production 1000 Center Housing AM Production mPts 1500 500 0 Total EI EI of the production phase Chart 2: A comparative graph of the EI for the total LC and the EI of the production phase for both ways of production of the turbocharger For a mass production the difference on the environmental impact between the AM and the conventional manufacturing is more significant. For example, a middle size mass production that is able to produce around 15,000 turbochargers, the switch from conventional production to AM just for the center housing can achieve less environmental impact equal to around 1780 Pts or 1.78 kPts equal to the yearly environmental load of almost two average European inhabitants. It is a slight difference that comes from just the change of the manufacturing way of one single component of the turbocharger. 4.7.2 Manufacturing Cost Analysis An analysis on cost of production is performed. The goal is to exploit the different parameters that generate the total cost of a part. But before that the estimation of the manufacturing cost that contains only the cost for the material the machine and the labor hands used for the manufacture of the center housing. AM eliminates the tooling cost and reduces the number of work stations and as a result the labors. On the other hand variables that are needed by some AM technologies, such as support, are added to the production cost. Though, technologies that use a powder bed, such as SLM, do not need support since the surrounding powder plays this role. In order to estimate a simple cost of manufacturing of the center housing using AM250 as SLM machine and Stainless Steel 316L as powder material, the upcoming formula is used. In the formula: 91 Application Case – Turbocharger 5 % of the powder material which is not fused is considered as scrap. The rest of the powder material (95%) is reused for the production of the next part. The labor cost is assumed to be 150 SEK per hour. 30 % of the annual production time is estimated to be the period of maintenance. The solidity of the part to be manufactured is estimated to be 50 % less compared with the 100 % dense part produced by sand casting. (??) The investment which is the machine cost is considered to be returned in eight years, in other words the Return of Investment (ROI). The part volume is calculated to be 127.334 cm3 with the help of SolidEdge software. The build area envelope of the machine is The build rate of the machine is 20 cm3/h. The electricity consumption of the machine is 31 kWh/kg. The price of the AM250 machine is 512,500 € or 4,587,564 SEK.11 The price of the Stainless Steel 316L is 89 €/kg or 797 SEK/kg.11 The density of Stainless Steel 316L is 0.008 kg/cm3. cm. In which: MOC represents the Manufacturing Overhead Cost and is assumed to be the depreciation cost of the machine. Depreciation cost is used to account the loss of value of the machine over time. The batch size is first estimated as 1 unit and it also assumed that in case of the solidity of 50 % the machine needs half the cycle time compared with the time needed to produce a fully dense part. 11 All calculations are made in SEK with the currency of 1 SEK = 8.97 €. 92 Application Case – Turbocharger Moreover, in order to decide the number of machines needed, the annual capability of each machine in parts must be calculated: It is assumed that the machine is operating 365 days per year and 24 hours per day except for the time needed for maintenance. The AM250 machine is capable of producing 1926 units per year. Consequently, when the annual capability of one machine is exceeded then a new machine is introduced to the cost calculations. The detailed tables are found in the Appendix 6. For the production of one unit the cost is extremely high and reaches the 574,349 SEK. Due to the high depreciation cost (573,000 SEK). As a more realistic scenario, it is assumed that the annual volume of the production is 15,400 units with eight machines operating simultaneously. In that case the following changes are observed in the different kind of costs: The depreciation cost drops rapidly to 298 SEK per unit for the production of 15,400 units due to the increased number of produced units. Whenever a new machine is introduced to the production the depreciation cost increases because of the addition of the price of purchase of the new machine until the production volume increases as well and the depreciation cost decrease again. The material cost per unit is the same, although discount on the price of the material is more possible when a lot of amounts of material powder are ordered. The labor cost per unit decreases as well due to the increased number of machines. However for a bigger volume of production either more labor hands may be needed or automated systems may be invented to remove the excess powder which is going to increase or decrease the labor cost respectively. The total manufacturing cost per unit drops to 783 SEK with fluctuations due to the depreciation cost. 93 Application Case – Turbocharger Graph 4: The correlation of the costs per unit with the number of units produced The Chart 3 illustrates the share of the total manufacturing cost (in SEK/unit) between the labor cost, the MOC and the cost of material. The latest is the most costly since the purchase of the material powder is very expensive nowadays and this cost stays the same regardless the production of more units when the labor cost and the MOC decrease. Total Manufacturing Cost (SEK/Unit) Labour Cost 11% MOC 7% Material Cost 82% Chart 3: Share of the total manufacturing cost. In order to estimate a future potential of AM, changes have been made in key parameters of the AM cost analysis and the total manufacturing cost per unit is calculated. The forecast of the years 2018 and 2013 is that large increase in build rates and decrease in powder prices are expected to occur. The build rate is expected to be increased from 20 cm3/h today (2014) to 40 cm3/h in 2018 and 80 cm3/h in 2023 due to the following advances: The introduction of two or more laser systems is most likely to occur in the future since nowadays the application of energy (laser power) per focus point is limited. 94 Application Case – Turbocharger The layer structure is going to be optimized with different layer thicknesses. The power dispensing process is going to be optimized in ways that the powder is going to be dispensed from both directions. The processes of powder dispensing and metal fusing are going to be done in parallel. More chamber systems are going to be introduced and the continuous production will be possible. The material cost is going to be reduced because of the decrease of the price of metallic material powder. It is assumed that the price is going to decrease from 798 SEK/kg of today (2014) to 632 SEK/kg in 2018 or 271 SEK/kg in 2023. The following reasons justify the reduction of the powder material price: The metal powder producers will sell to end customers directly due to increasing market volume because right now the price set by the AM providers does not reflect the production costs. The cost of production of metallic powder will decrease with the increasing volume. The AM material consumption is expected to increase from 900 tons to 9,000 tons by 2023 [70]. The Table 16 shows the reduction of total manufacturing cost per unit along with the material cost, the MOC and the labor cost for the production of 15,400 units. The material cost decreases due to the reduction of the material powder price. The MOC decreases due to the increased build rate which increases the annual machine capability and reduces the number of machines needed. The labor cost is reduced for low number of units because of the batch cycle time that is also decreased but the number of machines needed is less which makes the labor cost per unit remain the same for the production of 15,400 units. The total manufacturing cost per unit is reduced by almost 64% from 2014 to 2023. Year Material Cost (SEK/Unit) MOC (SEK/Unit) Labor Cost (SEK/Unit) Total Manufacturing Cost (SEK/Unit) 2014 426 298 60 783 2018 338 149 60 546 2023 145 74 60 279 Table 16: Forecast of the costs that consist the total manufacturing cost of the production of a turbocharger by AM250 with Stainless Steel 316L. 95 Application Case – Turbocharger The Figure 31 illustrates also the change in the share of the pie of total manufacturing cost. The piece of the labor cost increases in the pie that represents the total manufacturing cost and the piece of the material cost and MOC decrease from 2014 to 2023. 2014 2018 Labor Cost 8% Labor Cost 11% Material Cost 54% MOC 38% Material Cost 62% MOC 27% 2023 Labor Cost 21% Material Cost 52% MOC 27% Figure 31: The share of total manufacturing cost in 2014, 2018 and 2023. 4.7.3 Production Cost Analysis Furthermore the total production cost is calculated for the machine AM250 that uses SLM technology and Stainless Steel 316L as powder material. A forecast of the production cost is also estimated for the years 2018 and 2023. The production cost consists of the direct and indirect costs. Direct costs are the costs that are easily and directly traced to the product. For example the cost of the material that is part of the product and the cost of energy used by the machine attributed to the built of the product are direct costs. Manufacturing overhead costs consist of only indirect costs which are costs that are not directly accountable to a cost of product. This is the cost that the industry does not dedicate to the 96 Application Case – Turbocharger production of just the center housing but this cost is indirectly traced to it. Indirect costs are the machine costs, the labor costs and the production overhead costs. The machine cost consist of the cost of purchase of the machine, the annual maintenance cost, the annual cost of machine consumables (spare parts) and the purchase of wires in case of erosion. The labor cost includes the cost of the technicians, the monitoring costs and the cost attributed to postprocessing. The production overhead cost is the sum of the rent for the area per year and the administration overhead cost (front office salaries, office supplies, administration telephones, administration travel and entertainment etc). The aforementioned costs are summarized in the Table 17. New parameters are introduced for the calculation of the overall production cost such as the energy consumption per 1 kg, the set-up time per built (0.5 h per built), the machine utilization that is estimated to be 83%, the percentage of administrative overhead cost that is estimated as 25% of the overall indirect cost, the yearly cost of rent of the area occupied by a machine [70]. The more detailed table is found in the Appendix 9. Type of Cost SEK/cm Material 3.34 Energy 1.00 Direct 4.34 Machine 3.63 Labor 0.77 Production Overhead 1.62 Indirect 6.05 Overall Production 10.39 3 3 Table 17: AM costs (SEK/cm ) The overall production cost of AM is high at 10.39 SEK/cm3 and for the production of one unit of center housing the cost is 1323 SEK. For the massive production of center housings the production cost per unit will decrease. As shown in the Chart 5Chart 4 a big part (60%) of the indirect cost is the machine cost due to the high purchase price of the machine. The cost of the material is also a big part (42%) of the overall cost since the material powder is quite expensive today. 97 Application Case – Turbocharger Overall Production Cost Direct Cost (material) 42% Indirect Costs Production Overhead Cost 27% Indirect Cost 58% Chart 4: The percentages of the two main costs that share the overall production cost. Machine Costs 60% Labor Costs 13% Chart 5: The costs (in %) that make up the indirect cost. A forecast of the production cost has been estimated as well for the years 2018 and 2023. The same parameters that changed for the forecast of the manufacturing cost have been also modified for the forecast of the production cost. The build rate is estimated to increase and the material price is reduced due to the aforementioned reasons. In this case the percentage share of monitoring is also reduced from 2014 to 2018 because of advanced technological tools that will reduce the need of monitoring or even eliminate it in 2023. As a result (Table 18) the direct cost is reduced due to the material price and the indirect cost is also decreased because of the share of monitoring and the build rate. The overall production cost is then reduced significantly to 3.08 SEK/cm3 in 2023. For more details of the forecast of the overall production cost see Appendix 9. Year Direct Cost 3 (SEK/cm ) Indirect Cost 3 (SEK/cm ) Total Production Cost 3 (SEK/cm ) 2014 4.34 6.05 10.39 2018 3.15 2.65 5.80 2023 1.39 1.69 3.08 Table 18: Forecast of the costs that make up the total production cost of AM250 machine that uses Stainless Steel 316L as material powder. In 2023 the two main types of costs, direct and indirect, are estimated to share almost the half of the total production cost each. The total cost of production drops from 10.39 SEK/cm 3 to 3.08 SEK/cm3 which indicates that the reduction is estimated to be about 71%. The cost of production by metallic AM technologies is going to be almost the one third of the current cost. It is also worth mentioning that even in four-year time the overall cost is expected to be reduced by 44%. AM will not be characterized as an expensive way of manufacturing anymore and it will affect the industrial world extensively. 98 Application Case – Turbocharger 10.39 SEK/cm3 42% -44% 5.80 SEK/cm3 Direct Cost -47% Indirect Cost 3.08 SEK/cm3 54% 58% 45% 46% 2014 55% 2018 2023 3 Chart 6: Forecast metallic AM costs [SEK/cm ] Prerequisites 2014 2018 Build speed 20.00 h/cm 40.00 h/cm Machine price 4.6 MSEK 4.6 MSEK 4.6 MSEK Powder price 798 SEK/kg 632 SEK/kg 271 SEK/kg 5% 2% 0% 3 Share of monitoring 2023 3 3 80.00 h/cm Table 19: Changes in parameters that affect the AM costs. There are more changes that are expected to happen in the future and affect the cost of AM but they are not taken into consideration for this study. For instance: The prices of the machine may be increased because of the advancing technological improvements that will take place. The labor costs may be reduced due to the more reliable systems that will need less monitoring and maintenance. The introduction of automated systems for the removal of excess powder may also decrease the labor hands. The chamber volume may also increase and bigger turbocharger sizes will be possible to be manufactured. The post processing time is also going to be reduced because of advances in the roughness or accuracy of the metallic AM technologies. 4.7.4 Societal Impact Besides the environmental and economic impact, issues related to the societal impact of AM have also been discussed. Despite the fact that someone could claim that AM eliminates the human labor, it also enhances the desirability of jobs in manufacturing and creates more job positions by distributing the production to more workshops. However, this information is scattered with different 99 Application Case – Turbocharger focuses. So the objective is to gather, analyze and summarize information related to the societal impact of AM. Impact on manufacturing supply chain In the supply chain of conventional manufacturing, the materials flow from suppliers through numerous stages to the customer. The information flows backward. AM reduces the stages in the traditional supply chain by reducing the components of the products and moves the manufacture near the customer (distributed manufacture). As a result the effect is the reduction of warehousing, transportation and packaging. AM needs only 3D data and raw materials in order to produce a complex part so the setup time, changeover time and number of assemblies are significantly reduced. This results in reduction of material distribution and inventory holding for work in progress. It is also possible to implement Just in Time (JIT) manufacture at the workshop reducing non-value added processes resulting in lean supply chain. The manufacture of the product can be implemented when the order is placed to avoid stock. The production can be located next to the customer whose demands are met by customized products. Consequently, the supply chain is simplified to increase cost efficiency and responsiveness in customer demand fulfillment. With the personal AM machine, the customer can obtain desirable products with low cost whenever they want and without leaving their home [71]. Potential health and occupational hazards The conventional manufacturing processes such as casting and machining generate various emissions, fluid spills, noise and wasted chip material which are potential health and occupational hazards. One of the most health risks is the oil mist generated by traditional manufacture resulted from metalworking fluid that can even cause diseases such as dermatitis, bronchitis, bronchial asthma and lung fibrosis. Another workplace hazard is the noise that can lead to hearing difficulties or even hearing loss. These problems can be avoided with AM but some others may be created. Further investigation is needed about the toxicological hazards that may occur due to the use and disposal of materials used in AM. New materials such as epoxy resins, cyanocrylates, polycarbonates, acrylates, elastomers and polyamides (nylons) have been introduced for AM during the last decades. The human exposure on these materials and potential health effects must be investigated. Potential health effects may occur due to inhaling the vapors or if the materials accidently spill on the skin. Since the majority of the chemicals are long chain molecules, the materials remain in the environment for long time before being biodegraded. These investigations may also be the key for the widely acceptance of AM by the industry. 100 Application Case – Turbocharger Most of the materials used by AM are not dangerous for the human health. Nonetheless the operators must be educated in handling of high-intensity laser beams. Safety equipment like gloves, goggles and masks must be provided in the workshop. AM processes will become safer for the operators while new technological and safety features are developed and implemented in AM machines [71]. Impact on population health and wellbeing Another worth mentioning societal impact of AM is the impact on population health and wellbeing. After World War II people had easy access to vaccines and medicines and advances in surgical procedures have occurred resulting in the reduction of mortality rate and the increase of life expectancy. Governments around the world spend a great budget for the care of an increasing aging population. So delivering high quality and economically healthcare to improve people’s wellbeing is an important societal challenge nowadays. A key solution to that issue is the personalized care that addresses the needs of the patients in an economical way. AM offers customized products according to individual needs which can play a significant role in personalized healthcare. AM has already been used to produce customized surgical implants and assistive devices to improve the healthcare and wellbeing of the population. AM technologies can be used to produce customized surgical implants. Using computer tomography the specific data of the patient are scanned and then a solid model of the required implant for the patient is obtained using the appropriate materials. This way reduces also the lead time by shortening the design and delivery cycle times. AM can also be used to manufacture customized and light safety equipment such as helmets and protective garments. The safety equipment produced by AM provides excellent protection without sacrificing the comfort of the user. For example garments can be reduced to one piece that can fit the body perfectly without the need for joints. The create of systems for the design, production and supply of individualized medical and consumer products has been undertaken by the CUSTOM-FIT European initiative using AM technologies. This is expected to have a major positive impact in the quality of life of European citizens [71]. 101 Conclusions and discussion 5 Conclusions and discussion Additive Manufacturing (AM) comprises technologies that create objects sequentially adding layers over each other. The technologies are grouped according to the material that they use. During the last few years there have been improvements in the metallic technologies along with the metallic materials used. Analysis over different technologies and machines of metallic AM has shown that the technologies are not only different in terms of processes and machines, but also in terms of material, post processing and the desired accuracy. So one should carefully decide which technology should be chosen for each product type. During the recent years the substantial improvements in terms of production cost, materials properties, part quality and accuracy of technologies, made AM a more competitive manufacturing way over different industrial applications. Benefited from flexible and low cost manufacturing solutions, AM production has been applied in several markets and industries such as: Aerospace Automotive Customer products Medical Industry Academic sector One of the most critical aspects of the industrial application of AM is the DDM and is the single attempt of AM to be adjusted as a mass productive manufacturing way for end-use products. Setting as a reference, the automotive industry, an investigation indicates number of opportunities of possible application of AM in that high level demanding large production. Mostly economical potentials are driven from the need of variation and decentralization, the high cost of conventional production investment, design freedom, process and environmental output improvements. The automotive industry has been chosen for this analysis as an industrial field that can integrate the metallic AM for mass production and create functional products. The turbocharger is chosen as a DDM case. It is a device which is a component of the internal combustion engine of a passenger car. The turbocharger is a great candidate from the automotive industry to be studied due to its small size that is approachable from most of metallic AM technologies and its complex design which is limited due to the boundaries of conventional manufacturing. The freedom of design of AM can provide opportunities in terms of new structures and more complex surfaces in order to achieve 102 Conclusions and discussion more efficient waste energy recovery systems for the turbocharger and reduce the number of production processes needed. The six more significant components of the turbocharger are described in this research; the compressor housing, the compressor impeller, the bearing system, the center housing, the assembly of turbine impeller and shaft and the turbine housing. A brief description of the materials and various processes used to manufacture these parts is carried out in order to understand the technical needs of the components of a turbocharger. A criticality analysis is used in order to select the most critical component of the turbocharger whose development contributes more to the efficiency of the turbocharger. Design, engineering and production criteria such as the size, the design optimization, the life, the functional limits, the efficiency, the process consolidation, the production cost the recyclability are taken into consideration and result in the center housing. The production of the center housing with AM can reduce the maintenance costs and extend the life of the turbocharger, offer great stress resistance against high forces with almost similar mechanical properties of materials compared with the conventional manufacturing. An optimized design of the interior of the center housing that is easily achieved by AM offers improvements in the lubrication and cooling system increasing the efficiency of the turbocharger and the production costs can be reduced as well with less tools, less main and post operations and less monitoring with AM. One of the development statements of the center housing with AM is the production with the absolutely necessary functional parts resulting in a center housing that uses much less material. The machine chosen for this development is the AM250 by Renishaw which uses SLM technology together with stainless steel 316L as material input due to its high mechanical properties. It is worth mentioning that during the research of the metallic material properties for the study of AM, it was unforeseen that parts produced with metallic AM technologies have almost the same or sometimes superior mechanical properties with the conventional manufactured parts. Many advances have been made in the field of metallic materials for the use in AM. Furthermore, an analysis of the sustainability potential of the development of the critical component with AM is carried out. The results indicate that the SLM technology has less environmental impact in comparison with the sand casting method. However, the analysis is based only on literature and estimations have been made due to limitations. There is not any available software that uses database for the environmental impact of any AM technologies. The access was also limited to any LCA software that could calculate the environmental impact of conventional methods (sand casting). Besides these barriers the calculation and the comparison of the environmental impact of both ways of manufacturing was carried out following the Eco-indicator 99 method. For AM the impact of the production phase is based on the electrical energy which is used by the machine and estimations 103 Conclusions and discussion have been made for the impact that occurs due to the conversion of the metallic bulk material to metallic powder. LCA attributed about 6 % less environmental impact to the use of AM for the production of the center housing. One might say that the reduction of the impact is not that significant but if it is only the change of manufacturing of just one component that makes the difference. The development of more components and even the manufacturing of the whole turbocharger with AM may result in much more significant reduction in the environmental impact of its life cycle. In addition, the production cost of the aforementioned development has been estimated. High material and machine prices and low built rates produce expensive products compared with the conventional manufacturing costs. While lack of information of costs of sand casting did not make possible the comparison of costs between AM and conventional manufacturing, forecast of the production cost of AM has been carried out. It is noteworthy that even in 4-year time the cost of AM is estimated to decrease significantly and in about a decade AM will not be characterized as costly way of manufacturing anymore and the industrial world will be affected extensively. The societal impact of AM is analyzed as well in more general terms. AM is undoubtedly affecting the manufacturing supply chain by eliminating inventories and reducing warehousing, transportation and packaging. The production is moved closer to the customer and AM is ready to fulfill his demands in faster and more efficient way with more customized products. However, potential health and occupational hazards should be further investigated in order to proceed to the widely acceptance of AM by the industrial world and the society. Advances and contributions of AM in medical consumer products have a positive impact on the population healthcare and the human wellbeing resulting in better quality of life of citizens. Finally, it is worth mentioning that this report contains a comparison between an emerging family of technologies (AM) and a technology which has been used for many years for the production of metallic products. Because of the above, the results are conservative and are limited to the information that is available. 104 Further Research 6 Further Research The conclusions of this research were based on limited data available. The environmental and economic scale for the production of large quantities needs to be investigated more precisely. More accurate cost analysis and estimation of the environmental impact over different parts and machines is suggested in order to lead to the investigation of different AM development alternatives. The involvement of automotive industries would provide this research with more accurate input data. 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Int J Adv Manuf Technol. 67, p1191-1203. 110 Appendices Appendix 1: Properties of materials used for the production of the turbocharger with conventional manufacturing. .................................................................................................................................... 112 Appendix 2: Properties of metallic materials produced by AM. ......................................................... 114 Appendix 3: Calculation of machining holes of the center housing .................................................... 116 Appendix 4: Eco-indicator 99 method for the calculation of the EI of the production of the turbocharger with conventional manufacturing methods.................................................................. 117 Appendix 5: Eco-indicator 99 method for the calculation of the EI of the production of the turbocharger with the center housing manufactured by SLM and Stainless Steel 316L. ................... 118 Appendix 6: Calculation of the manufacturing cost for the production of the center housing with SLM (AM250 machine) and stainless steel 316L. (Year 2014) .................................................................... 119 Appendix 7: Forecast - Calculation of the manufacturing cost for the production of the center housing with SLM (AM250 machine) and stainless steel 316L. (Year 2018) .................................................... 120 Appendix 8: Forecast - Calculation of the manufacturing cost for the production of the center housing with SLM (AM250 machine) and stainless steel 316L. (Year 2023) .................................................... 121 Appendix 9: Calculation of the total production cost of the manufacturing of the center housing with SLM (AM250 machine) and stainless steel 316L in 2014 and forecast for years 2018 and 2023. ...... 122 111 Appendix 1: Properties of materials used for the production of the turbocharger with conventional manufacturing. Material Density (g/cm3) Thermal Properties Mechanical Properties Al - Al 7075 based 2.81 TC 173 W/mK; CTE 25.2 μm/m°C; MP 477 - 635.0 °C UTS 228 MPa; YTS 103 MPa; BE 10% Al C355 2.71 TC 151 W/mK; CTE 24.7 μm/m°C; MP 546 - 621 °C UTS 248 MPa; YTS 172 MPa; BE 2.5% Al C354 T61 cast 2.71 TC 126 W/mK; CTE 22.9 μm/m°C; MP 538 - 596.1 °C UTS 331 MPa; YTS 255 MPa; BE 3% Al 201 T7 cast 2.80 TC 121 W/mK; CTE 24.7 μm/m°C; MP 571 - 649 °C UTS 414 MPa; YTS 345 MPa; BE 3% Cast Al 2.77 TC 210 W/mK; CTE 25.5 μm/m°C; MP 660 °C UTS >= 150 MPa 4.43 TC 6.7 W/mK; CTE 8.6 μm/m°C; MP 1604 - 1660 °C UTS 1035 MPa YTS 890 MPa BE 10% 3.91 MP 1460 °C UTS 450 - 800 MPa; YTS 400 - 650 MPa; BE 4% 7.91 TC 9.8 W/mK; CTE 10.7 μm/m°C; MP 1260-1288 °C UTS 758 MPa; YTS 689 MPa; BE 3% Inconel 718 8.19 TC 13 W/mK; CTE 13.0 μm/m°C; MP 1260 – 1336 °C UTS 1230 MPa; YTS 1030 MPa; BE 12% Inconel 706 8.05 TC 12.5 W/mK; CTE 16.4 μm/m°C; MP 1334 – 1371 °C UTS 757 MPa; YTS 383 MPa; BE 47% Inconel 625 N/A N/A UTS 689 MPa; YTS 414 MPa; BE 30% Mar-M-24712 8.53 N/A UTS 965 MPa; YTS 815 MPa 7.24 TC 26.6 W/mK; UTS 503 MPa; Ti - Ti-6Al-4V cast based γ – TiAl Ni - Inconel 713C based 13 Fe - Cast iron 12 http://www.secotools.com/en-US/Global/Industry-Solutions/Aerospace-Solutions/AS-Material-main/Heat-resistantsuper-alloys/Inconel-71873/ 13 Average values 112 CTE 12.7 μm/m°C; MP 1120 – 1310 °C YTS 428 MPa; BE 8% 7.80 TC 16.9 W/mK; CTE 16.9 μm/m°C; MP 1440 °C UTS 572 MPa; YTS 323 MPa; BE 23% Stainless cast steel CF8C N/A N/A UTS 485 MPa; YTS 205 MPa; BE 30% Stainless Steel 316 7.99 TC 16.2 W/mK; CTE 16.0 μm/m°C; MP 1371 – 1399 °C UTS 579 MPa; YTS 290 MPa; BE 50% AISI 4140 Steel 7.85 TC 33.0 W/mK; CTE 13.7 μm/m°C; MP 1416 °C UTS 655 MPa; YTS 415 MPa; BE 25% 14 Cu - Leaded bronze based 8.91 TC 69.6 W/mK; CTE 18.0 μm/m°C; MP 826-988 °C UTS 262 MPa; YTS 131 MPa; BE 18% Brass 13 8.52 TC 124 W/mK; CTE 20.1 μm/m°C; MP 917 °C UTS 438 MPa; YTS 260 MPa; BE 32% based Cast Stainless steel 13 14 http://www.concast.com/c92200.php 113 Appendix 2: Properties of metallic materials produced by AM. Material Process15 Powder Characteristics Mechanical Properties spherical shape (25-45 μm) Ti6Al4V DMD spherical shape (-100+325 mesh) UTS 1163 MPa; YTS 1105 MPa (as deposited) 17 Ti6Al4V LPF spherical shape (25-45 μm) UTS 1211; YTS 1100; BE 13.0% 17 Ti6Al4V LENS N/A UTS 955 MPa; YTS 848 MPa; BE 15% 17 Ti6Al4V LC N/A UTS 1157 MPa; YTS 1062 MPa; BE 6% 17 Ti6Al4V EBM UTS 1020 MPa YTS 950 MPa BE 14% 18 Al - AlSi10Mg SLM based (EOS SLM 17 N/A ~ 100% density; UTS 355 MPa (horizontal); YTS 250 MPa; TC 113 W/mK ; CTE 20.9 µm/m°C; MP 557-596 °C 17 near spherical shape; (mean particle size 50μm) 89% density; TC 180 W/mK; 17 GmbH, Germany ) Al 6061 TC 6.7 W/mK; CTE 8.6 µm/m°C; MP 1604 1660 °C Ref. SLM Ti - Ti6Al4V based ~ 100% density UTS >1000 MPa; BE 12%; Thermal Properties16 CTE 23.6 µm/m°C; MP 582 651.7°C Ni - Inconel based 718 LPF Gas atomized; spherical shape (44 – 150 μm) UTS 1240 MPa; YTS 1133 MPa (heat treated); 15 TC 13 W/mK; CTE 13 µm/m°C; 17 SLM, Selective Laser Melting; DMD, Direct Metal Deposition; LPF, Laser Powder Forming. Values of thermal properties of same materials produced by conventional manufacturing techniques. 17 D. D. Gu, W. Meiners, K. Wissenbach, R. Poprawe. (2012). Laser additive manufacturing of metallic components: materials, processes and mechanisms. International Materials Reviews. 57 (3), p133-164. 18 Nannan GUO, Ming C. LEU. (2013). Additive manufacturing: technology, applications and research needs. Front. Mech. Eng. 8 (3), p215-243. 16 114 BE 11% MP 1260 - 1336 °C Inconel 718 SLM N/A UTS 1200 MPa; YTS 950 MPa; BE 24% 19 Inconel 718 EBM N/A UTS 1238 MPa; YTS 1154 MPa; BE 7% 18 Inconel 625 SLM UTS 682 MPa; YTS 410 MPa; BE 30% 17 Inconel 625 LENS N/A UTS 930 MPa; YTS 579 MPa; BE 38% 17 Rene 88DT LPF Spherical shape (44 – 150 μm) UTS 1400-1440 MPa; YTS 1010-1030 MPa; BE 17.5% (HIP) 17 Fe - Stainless based Steel 316 SLM Spherical shape (53-173 μm) UTS 826 MPa; YTS 419 MPa Stainless Steel 316 LENS N/A UTS 661 MPa; YTS 276 MPa; BE 67% N/A UTS 1000 MPa; YTS 950 MPa; BE 25% Spherical shape; (-100/+325 mesh) UTS 240 MPa; YTS 317 MPa; BE 14% EOS DMLS stainless steel 17-4 Cu - Cu30Ni based DMD 19 TC 16 W/mK CTE 16 µm/m°C; MP 1371 1399 °C 17 TC 12.9 W/mK; Melotte, Direct Digital Manufacturing. (2011). Inconel, SLM Materials. http://www.materialsource.com/sites/default/files/slm_materials_inconel_0.pdf. Last accessed 8th Apr 2014. 115 17 17 17 Available: Appendix 3: Calculation of machining holes of the center housing No Diameter Distance Volume 1 9 3.5 222.6603793 mm3 2 3 12.12 85.67123166 mm3 3 17 1.5 340.4701038 mm3 4 53 14.85 32761.8241 mm3 5 12 13.04 1474.789255 mm3 6 14 13 2001.19452 mm3 7 5 6 117.8097245 mm3 8 4 14 175.9291886 mm3 9 5.5 17.09 406.029252 mm3 10 5.5 17.09 406.029252 mm3 11 5.5 17.09 406.029252 mm3 12 5.5 17.09 406.029252 mm3 13 4.5 10 159.0431281 mm3 14 16 7.5 1507.964474 mm3 40471.47311 mm3 Density Cast Iron 7240 Kg/m3 Total Scrap Weight 0.293 Kg Center Housing Weight: 0.922 kg Cast iron Weight : 1.215 kg Total Scrap Volume: 116 Appendix 4: Eco-indicator 99 method for the calculation of the EI of the production of the turbocharger with conventional manufacturing methods Product or Component Date Notes and Conclusions Center Housing Project Conventional Production 23-05-14 Author Turbocharger A. Kair & K. Sofos Analyst of a Turbocharger device of an passenger's car Internal Combustion Engine (ICE). Assumption: 15 years use Production (Materials, processing, transport and extra energy) Material or Process Amount Inconel 713C Steel 4140 Milling, Turning, Drilling Friction Welding Aluminum C355 Cast iron Milling, Turning, Drilling Brass Milling, Turning, Drilling Austenitic stainless cast steel Cast aluminum Total Unit 0.0720 kg 0.0610 kg 0.0007 dm3 2.1786 per 7 mm 0.0260 kg 1.2150 kg 0.0405 dm3 0.0506 kg 0.0005 dm3 2.0520 kg 0.5160 kg mPt Indicator 5200 110 800 2.7 780 240 800 1400 800 240 780 Result 374.400 6.710 0.561 5.882 20.280 291.600 32.377 70.840 0.435 492.480 402.480 1698.045 Use (Transport, energy and any auxiliary materials) Process Amount Fuel Oil Total 1.8000 Unit kg mPt Indicator 180 Result 324.000 324.000 Disposal (Disposal processes per type of material) Material and type of processing Incineration Steel (22% in Europe) Incineration Aluminum (22% in Europe) Landfill Steel (78% in Europe) Landfill Aluminum (78% in Europe) Total Amount 0.73216 0.11924 2.59584 0.42276 Total (all Phases) Unit kg kg kg kg mPt mPt 117 Indicator -32 -110 1.4 1.4 Result -23.429 -13.116 3.634 0.592 -32.319 1989.726 Appendix 5: Eco-indicator 99 method for the calculation of the EI of the production of the turbocharger with the center housing manufactured by SLM and Stainless Steel 316L. Product or Component Date Notes and Conclusions Center Housing AM Production 23-05-14 Project Turbocharger Author A. Kair & K. Sofos Analyst of a Turbocharger device of an passenger's car Internal Combustion Engine (ICE). Assumption: 15 years use Production (Materials, processing, transport and extra energy) Material or Process Inconel 713C Steel 4140 Milling, Turning, Drilling Friction Welding Aluminum C355 Stainless steel 316 L (Powder) SLM 250 (50% Solidity) Brass Milling, Turning, Drilling Austenitic stainless cast steel Cast aluminum Total Amount Unit 0.0720 kg 0.0610 kg 0.0007 dm3 2.1786 per 7 mm 0.0260 kg 0.5087 kg 0.5087 kg 0.0506 kg 0.0005 dm3 2.0520 kg 0.5160 kg mPt Indicator 5200 110 800 2.7 780 86 310 1400 800 240 780 Result 374.400 6.710 0.561 5.882 20.280 43.748 157.697 70.840 0.435 492.480 402.480 1575.513 Amount Indicator Result Use (Transport, energy and any auxiliary materials) Process Fuel Oil Total 1.8000 Unit kg mPt 180 324.000 324.000 Disposal (Disposal processes per type of material) Material and type of processing Amount Incineration Steel Incineration Aluminum Landfill Steel Landfill Aluminum Total 0.5768 0.1192 1.7554 0.4228 Total (all Phases) Unit kg kg kg kg mPt mPt 118 Indicator -32 -110 1.4 1.4 Result -18.457 -13.116 2.458 0.592 -28.524 1870.989 Appendix 6: Calculation of the manufacturing cost for the production of the center housing with SLM (AM250 machine) and stainless steel 316L. (Year 2014) Center Housing Component Part Price 784 SEK/part X= 10.6 cm Part Y= Dimensions Z= 10.6 cm 4.8 cm Part Volume 127.3 cm3 AM 250 Machine Price Key Assumptions 4,587,564 X= Build Area Y= Dimensions Z= Built Area Volume Build Rate Electricity Consumption SEK 25 cm Powder Scrap % 30 cm Solidity 50% Build Tray Volume Annual Maintenance Annual Machine Capability Return of Investment (ROI) Hourly Labour Cost 3000 cm3 30% 1926 parts 8 Years 150 SEK 18,750 cm3 20 cm3/h 31 KWh/kg 798 SEK/kg 6.3760 SEK/cm3 0.0080 kg/cm3 Material Price Density Units Number of Machines 1 1,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 15,400 4 4,138 6,208 5,518 6,897 6,208 7,242 6,621 7,449 6,897 7,587 7,094 7,686 7,242 7,759 7,966 1 1 2 3 3 4 4 5 5 6 6 7 7 8 8 8 Manufacturing Overhead Cost (MOH) Material Cost Labor Cost (SEK/Unit) Depreciation Cost Depreciation Cost (SEK/Unit) (SEK/Unit) (SEK/cm3) 426 426 426 426 426 426 426 426 426 426 426 426 426 426 426 426 573,446 573 382 430 344 382 328 358 319 344 313 335 309 328 306 298 119 1 parts Batch Cycle Time Stainless steel 316 Yearly Working Hours Batch Size 25 cm 4,503 5 3 3 3 3 3 3 3 2.7 2.5 2.6 2.4 2.6 2.4 2.3 478 478 239 159 159 119 119 96 96 80 80 68 68 60 60 59.68781 Total Manufacturing Cost (SEK/Unit) 574,349 1,477 1,047 1,015 929 928 873 880 840 850 819 829 803 814 792 784 3.18 hours 5% Appendix 7: Forecast - Calculation of the manufacturing cost for the production of the center housing with SLM (AM250 machine) and stainless steel 316L. (Year 2018) Center Housing Component Part Price 546 SEK/part X= 10.6 cm Part Y= Dimensions Z= 10.6 cm AM 250 Machine Price Build Area Dimensions 4.8 cm Part Volume 127.3 cm3 Key Assumptions 4,587,564 SEK Batch Cycle Time Y= 25 cm Powder Scrap % 30 cm Solidity 50% Build Tray Volume Annual Maintenance Annual Machine Capability Return of Investment (ROI) Hourly Labour Cost 3000 cm3 30% 3853 parts 8 Years 150 SEK Z= Built Area Volume Build Rate Electricity Consumption 18,750 cm3 40 cm3/h 31 KWh/kg 632 SEK/kg 5.0497 SEK/cm3 0.0080 kg/cm3 Material Price Density Manufacturing Overhead Cost (MOH) Units Number of Machines 1 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 15,400 2 2,069 4,138 6,208 4,138 5,173 6,208 7,242 5,518 6,208 6,897 7,587 6,208 6,725 7,242 7,759 7,966 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 4 Material Cost (SEK/Unit) 338 338 338 338 338 338 338 338 338 338 338 338 338 338 338 338 338 1 parts 25 cm Stainless steel 316 Yearly Working Hours Batch Size X= Depreciation Cost (SEK/Unit) 573,446 573 287 191 287 229 191 164 215 191 172 156 191 176 164 153 149 120 Labor Cost Depreciation Cost (SEK/Unit) (SEK/cm3) 4,503 5 2 2 2 2 2 1 2 2 1.4 1.2 1.5 1.4 1.3 1.2 1.2 239 239 239 239 119 119 119 119 80 80 80 80 60 60 60 60 59.6878 Total Manufacturing Cost (SEK/Unit) 574,022 1,150 863 767 744 686 648 621 632 608 589 574 588 574 561 550 546 1.59 hours 5% Appendix 8: Forecast - Calculation of the manufacturing cost for the production of the center housing with SLM (AM250 machine) and stainless steel 316L. (Year 2023) Center Housing Component Part Price 279 SEK/part X= 10.6 cm Part Y= Dimensions Z= 10.6 cm 4.8 cm Part Volume 127.3 cm3 AM 250 Machine Price Key Assumptions 4,587,564 X= Build Area Y= Dimensions Z= Built Area Volume Build Rate Electricity Consumption SEK Batch Size 1 parts 25 cm Batch Cycle Time 0.80 hours 25 cm Powder Scrap % 30 cm Solidity 50% 18,750 cm3 80 cm3/h 31 KWh/kg Build Tray Volume Annual Maintenance Annual Machine Capability Return of Investment (ROI) 3000 cm3 30% 7705 parts 8 Years 271 SEK/kg 2.1653 SEK/cm3 0.0080 kg/cm3 Hourly Labour Cost 5% Stainless steel 316 Material Price Density Units 1 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 15,400 Yearly Working Number of Hours Machines 1 1,035 2,069 3,104 4,138 5,173 6,208 7,242 4,138 4,656 5,173 5,690 6,208 6,725 7,242 7,759 7,966 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 Manufacturing Overhead Cost (MOH) Material Cost Labor Cost Depreciation Cost Depreciation Cost (SEK/Unit) (SEK/Unit) (SEK/Unit) (SEK/cm3) 145 145 145 145 145 145 145 145 145 145 145 145 145 145 145 145 145 573,446 573 287 191 143 115 96 82 143 127 115 104 96 88 82 76 74 4,503 5 2 2 1 1 1 1 1 1 0.9 0.8 0.8 0.7 0.6 0.6 0.6 121 119 119 119 119 119 119 119 119 60 60 60 60 60 60 60 60 59.68781 Total Manufactruring Cost (SEK/Unit) 573,710 838 551 455 407 379 360 346 348 332 319 309 300 293 286 281 279 150 SEK Appendix 9: Calculation of the total production cost of the manufacturing of the center housing with SLM (AM250 machine) and stainless steel 316L in 2014 and forecast for years 2018 and 2023. 2014 Direct Cost Cost of 316L Stainless Steel Powder Cost of energy 42% 798.00 SEK/kg 1.05 SEK/kWh 4.34 SEK/cm3 58% 6.05 SEK/cm3 Indirect Cost Machine Costs AM machine purchase Maintenance cost p.a. Operating time Machine consumables p.a. Wire erosion machine purchase Labor Costs Technician hourly rate Set-up time per build Share of monitoring Troubleshouting p.a. Post-processing per built Machine Parameters Machine utilization Chamber volume Net utilization of part volume Build rates Energy consumption Additional Parameters Metal Density for 316LL stainless steel powder Support structure Production Overhead Cost Yearly rent for area 28m2 Administration overhead Overall Cost 4,587,564 SEK 216,923 SEK 8 years 27,115 SEK 578,463 SEK 150.00 SEK 0.50 hours 5.00% 440.00 hours 0.10 h/kg 3.35 1.00 3.63 2.34 0.88 0.11 0.29 0.77 0.62 0.03 0.12 2018 54% 632.00 SEK/kg 1.05 SEK/kWh 46% 4,587,564 SEK 216,923 SEK 8 years 27,115 SEK 578,463 SEK 150.00 SEK 0.50 hours 2.00% 440.00 hours 0.10 h/kg 2023 3.15 SEK/cm3 2.65 0.50 45% 271.00 SEK/kg 1.05 SEK/kWh 1.39 SEK/cm3 55% 1.69 SEK/cm3 2.65 SEK/cm3 1.82 1.17 0.44 0.06 0.15 0.75 0.62 0.01 0.12 4,587,564 SEK 216,923 SEK 8 years 27,115 SEK 578,463 SEK 150.00 SEK 0.50 hours 0.00% 440.00 hours 0.10 h/kg 83.00% 18,750.00 cm3 0.68% 20.00 cm3/h 31.00 kWh/kg 83.00% 18,750.00 cm3 0.68% 40.00 cm3/h 31.00 kWh/kg 83.00% 18,750.00 cm3 0.68% 80.00 cm3/h 31.00 kWh/kg 0.0080 kg/cm3 0.00 0.0080 kg/cm3 0.00 0.0080 kg/cm3 0.00 32,900.00 SEK 25.00% 1.65 0.13 1.51 32,900.00 SEK 25.00% 10.39 SEK/cm3 0.08 0.07 0.02 5.80 SEK/cm3 122 32,900.00 SEK 25.00% 1.14 0.25 0.91 0.58 0.22 0.03 0.07 0.74 0.62 0.00 0.12 0.04 0.03 0.01 3.08 SEK/cm3 123
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