engineering – materials and technology

Coimisiún na Scrúduithe Stáit
State Examinations Commission
LEAVING CERTIFICATE 2011
MARKING SCHEME
ENGINEERING – MATERIALS
AND TECHNOLOGY
ORDINARY LEVEL
LEAVING CERTIFICATE 2011
MARKING SCHEME
Written Examination and Practical Examination
ENGINEERING –
MATERIALS AND TECHNOLOGY
ORDINARY LEVEL
1
LEAVING CERTIFICATE
ENGINEERING - Materials and Technology
(Ordinary Level – 200 marks)
Written Examination Marking Scheme 2011
Answer Question 1, Sections A and B and Three other questions.
Question
Question 1:
1:
Total
Total -- 65
65 Marks.
Marks.
Section
Section A
A –– 30
30 Marks
Marks
Any
six
@
5
marks
Any six @ 5 marks each
each.
Two
Two part
part answers
answers 33 ++ 22
Section
Section B
B –– 35
35 Marks
Marks
Any
three
parts
Any three parts @
@ 12
12 ++ 12
12 ++ 11
11 Marks
Marks
Two
Two part
part answers
answers 66 ++ 66 or
or 66 ++ 55
Question 2 Total - 45 Marks.
Question 3 Total - 45 Marks.
Question 4 Total - 45 Marks.
(a) Three parts @ 5each (15)
(a) Two parts @ 8 each
(16)
(a) Three parts @ 5 each
(b) Three parts @ 5 each (15)
(b) Two parts @ 5 each
(10)
(b) Three parts @ 4 each
(12)
(c) Three parts @ 3 each (9)
(c) Two parts @ 5 each
(10)
(c) Three parts @ 4 each
(12)
(d) Two parts @ 3 each (6)
(d) Two parts 5 & 4
OR
(d) Two parts 5 & 4
(9)
(d) Two parts @ 3 each
(6)
Question 5 Total - 45 Marks.
(15)
(9)
Question 7 Total - 45 Marks.
Question 6 Total - 45 Marks.
(a) Two parts @ 2 marks
Two parts @ 5 marks
Two parts @ 2 marks (18)
(a) Three parts @ 5 each
(15)
(a) Two parts @ 5 each
(b) Three parts @ 5 each
(15)
(b) Four parts @ 5 each (20)
(b) Two parts @ 3 each
(6)
(15)
(c) Three parts @ 5 each
(15)
(c) Three parts @ 5 each
OR
(c) Three parts @ 5 each
(c) Three parts @ 5 each
OR
(c) Three parts @ 5 each
(d) Two parts @ 3 each
(6)
(15)
2
(10)
(15)
(15)
Sample Answers and Marking Scheme
Note: The solutions presented are examples only.
All other valid solutions are acceptable and are marked accordingly.
Question 1
(65 Marks)
Marks
SECTION A - 30 MARKS
6 parts @ 5 marks each
For two part answers award 3 + 2
SECTION B - 35 MARKS
2 parts @ 12 marks each
1 part @ 11 marks
Award 6 + 6 or 6 + 5 as Appropriate
MARKS
SECTION A – 30 MARKS
(a)
(i) To highlight the need to wear protective goggles when working on a centre lathe.
3 + 2 Marks
(ii) To ensure eyes are protected when using a pillar drilling machine.
(b)
The alloy produced from copper and zinc is brass.
(c)
A countersinking drill is used to enlarge the mouths of holes to accommodate the
heads of countersunk screws or rivets.
(d)
An acme thread is used on a lathe leadscrew to provide automatic power feed to the
carriage when screw cutting.
(e) The toggle switch can be used to turn a control circuit for a DC motor on or off.
(f)
Galvanised iron is the term given to steel when coated with zinc.
(g) (i) Computer Aided Manufacturing can be used to produce high quality design
products.
5 Marks
5 Marks
5 Marks
5 Marks
5 Marks
3 +2 Marks
(ii) Computer Aided Manufacture supports the development and production of better
and more complex design ideas.
(h) (i) The gear mechanism shown is a worm and wheel mechanism.
3+2 Marks
(ii) A worm and wheel mechanism can be used to provide a large reduction in output
speed.
3
SECTION B – 35 MARKS
(i) Any one
Good clear description
Award 12 (11) Marks
Total (12, 11) Marks
Ratchet and pawl mechanism
A ratchet and pawl mechanism is used to allow a shaft, axle or pin to
rotate in one direction only. The teeth on the ratchet wheel are so shaped
that the pawl slides over them in one direction and engages to restrict
movement in the other direction. Ratchet and pawl mechanisms are used
in ratchet spanners, fishing reels, ratchet screwdrivers, micrometers and
winding machines etc.
Micrometer
A micrometer is a precision measuring instrument used for accurately
Measuring small distances of up to 0.01mm. Usually based on a caliper
design, the operation of a micrometer depends on the opening and
closing of a screw thread (spindle). Articles are measured between
the face of an anvil and the end face of the screw thread. One complete
turn of the screw thread closes the micrometer a distance equal to the
pitch of the spindle thread.
.
Lathe Tailstock
A tailstock is part of a centre lathe. The tailstock sits on the lathe bed at
the opposite end to the lathe headstock. It can be clamped to the bed at
any point. The tailstock contains a barrel which slides in the body when
you turn the hand wheel. The barrel can be locked in any position. The
barrel can accommodate different tools for drilling, reaming or for
supporting long shafts when machining. The tailstock can be moved
from side to side on its base, this feature is used for taper turning.
4
(i) Any two
Good clear description
Award 6 + 6(5)
Total (12, 11) Marks
Wireless connection
Wireless connection allows computers / phones share information without
the use of connecting cables. Information data is moved between computers
by radio waves allowing laptops to move about within wireless networks.
The cost and complexity of cable connections is removed.
USB key
A USB (Universal Serial Bus) key is a small portable data memory storage
device. The key consists of a flash memory device integrated with a USB
interface with can be inserted into a PC or laptop’s USB port. USB keys
are removable and rewritable and physically much smaller than CD’s or
DVD’s. Because of their design USB keys are faster, have thousands
of times more storage capacity and are more durable and reliable because
of their lack of moving parts.
Graphics card
A graphic card is a printed circuit board that plugs into a computer to give it
display capabilities. The graphics card generates output images for a display
monitor or screen. Graphic cards, located in expansion slots, can offer added
functions such as improved rendering of 3D & 2D drawings, video capture,
TV-tuner adapter, MPEG-2/MPEG-4 decoding, firewall, light pen, and TV
output etc.
Video conferencing
Video conferencing uses telecommunications of audio and video to bring
people at different locations together for a meeting. This can be as simple
as a conversation between two people in private offices or involve several
different locations with more than one person in large rooms. Video
conferencing can also be used to share documents, computer - displayed
information and whiteboards.
5
(k)
Elasticity
Elasticity is the ability of a material to return to its original shape when
freed from a force which was distorting it.
Definition
Award 6(5) Marks
Eample
Award 6(5) Marks
Total (12,11) Marks
Materials used to produce compression or tension springs need to have
good elasticity to ensure they exert the correct type of force when trying
to return to their original shape.
(l) Any two
Good description
Award 6 + 6 (5)
Total (12, 11) Marks
Engraving
Engraving is a process of cutting designs or text into metal surfaces with
sharp tools. Different shaped tools may be used to provide a range of
designs while power tools are often used for engraving letters and numbers
on ornamental objects.
Printed circuit board (PCB)
A printed circuit board (PCB) is usually a plastic board about 1.6mm thick
with a thin layer of copper on one side. Unwanted portions of the copper are
routed or etched away to leave pads and strips which form electrical connections
between the components. The components are soldered to the pads. The strips
allow the current to move from component to component.
Parting-off tool
Parting – off is a machining process of cutting off metal in the centre lathe. A narrow
tool is fed into and through the centre of the work. The tool is kept as narrow as
possible to reduce waste and power requirements.
(m)
Lacquering
Lacquering is the process of applying a lacquer or varnish to metals to protect
and preserve their surface finish. Lacquers are applied by brushing or spraying
and can be used on both ferrous and non ferrous metals.
Name
Award 6(5) Marks
Function
Award 6(5) Marks
Name:
Total (12,11) Marks
A combination centre or slocombe drill.
Function:
A combination centre drill is used to locate the centre of round bars when
drilling on the centre lathe. The combination centre drill is also used to produce
the correct seating for the tailstock centre and / or headstock centre when
supporting work between centres.
6
Question 2
(a)
Any three
(i)
Name:
Function:
(ii) Name:
Function:
(iii) Name:
Function:
(iv) Name:
Function:
(b)
(45 Marks)
Name and function
Electric Arc Furnace.
Award 3 @ 5 Marks
Electric Arc Furnace is used to produce High Carbon Steel. Total (15) Marks
Basic Oxygen Furnace.
Basic Oxygen Furnace is used to produce Steel.
Cupola Furnace.
Cupola furnace is used to produce Cast Iron.
Blast Furnace.
Blast furnace is used to produce Iron.
Any three descriptions
Good clear description
Award 3 @ 5 Marks
Total (15) Marks
(i) High carbon steel
High carbon steel is hard and wear resistant. It can be hardened and
tempered and contains 0.65% to 1.4% of carbon.
(ii) Metal Ore
A metal ore is required when producing metals. It contains a mixture of
earthy materials in the form of rocks, clay, sand with a metal mix through it.
(iii) Tinplate
Tinplate is produced by coating both sides of thin sheets of steel with tin.
The tin protects the steel from rusting as well as giving it an attractive
appearance.
(iv) Tuyere
Tuyeres are large nozzles found near the base of a Blast Furnace. They allow
hot air to be blown through the base of the mix to aid in the smelting process.
(c)
Any three metals
(i)
(ii)
(iii)
(vi)
Aiuminium
Cast Iron
Lead
High-speed steel
-
Airplane bodies
Bench vices
Roof flashing
Twist drills
(d) Two advantages
Alloys improve the properties of metals or give them new properties.
•
Stainless steel is resistant to corrosion and is suitable for household
kitchen use.
•
High speed steel can retain its hardness at high temperatures and is
suitable for making H.S.S. cutting tools.
Component
Award 3 @ 3 Marks
Total (9) Marks
Advantages
Award 2 @ 3 Marks
Total (6) Marks
7
Question 3
(45 Marks)
(a) Any two descriptions
(i) Hardening
High carbon steel is hardened by heating to a cherry red and then
cooling rapidly or quenching in oil or water. At the cherry red
temperature the steel will undergo structural changes and the
rapid cooling does not allow it to revert to it’s normal condition.
(ii)
Good clear description
Award 2 @ 8 Marks
Total (16) Marks
Annealing
Annealing is carried out to soften metal and to relieve internal stresses.
When annealing a metal it is heated to a red color and allowed to cool as
slowly as possible i.e. in a furnace which is cooling down.
(iii) Tempering
Tempering is used to reduce the hardness level of components which have
been hardened. To temper the point of a centre punch, first polish with
emery cloth so that the tempering colours can appear. Heat slowly behind
the hardened portion and allow the heat to travel gradually to the point.
The tempering colours will appear as the temperature rises. When the
correct colour reaches the point i.e. brown, cool it in oil or water.
.
(b)
(i) One reason
The point of the centre punch has not been hardened / tempered
correctly leaving it too soft for use or the point has been over heated
when sharpening on a grindstone.
(ii) One method
Ensure the point is hardened and tempered to the correct level / ensure
regularly cooling when grinding.
(c)
(d)
Reason
Award 5 Marks
Method
Award 5 Marks
Total (10) Marks
Two safety precautions
•
Wear protective clothing to protect from hot water splashes or rising
steam.
•
Perform hardening process in a well protected area away from busy
environments.
Any two material properties
(i) Brittleness
A brittle material can easily be fractured by an impact. Glass is an
example of a brittle material.
Safety
Award 2 @ 5 Marks
Total (10) Marks
Description
Award 1 @ 5 Marks
Award 1 @ 4 Marks
Total (9)
8
(ii) Malleability
A property which allows a material to be exerted in all directions without rupture,
by rolling or hammering. The malleability of most metals is increased by heating.
(iii) Conductivity
This is the ability of a material to allow heat or electricity to flow through it.
Silver, copper and aluminium are good conductors of heat and electricity.
OR
(d) (i) Pneumatics
Pneumatics uses compressed air to do work. Stored energy in compressed air can
open and close pistons or turn pneumatic motors.
(ii)
A simple pneumatic circuit is the compressed air drill used by dentists for drilling
teeth.
Question 4
(45 Marks)
(a)
(i) Three oxy-acetylene flames
Neutral flame - Oxidising flame - Carbonising flame
(ii) Proportions of oxygen and acetylene
Neutral :
Equal amounts of oxygen and acetylene
Oxidising:
More oxygen than acetylene
Carbonising: More acetylene than oxygen
Name & proportions
Award 3 @ 5 Marks
Total (15) Marks
(b)
Any three
Explanation
(i) Quick and easy to achieve a permanent joint. Only need for access to Award 3 @ 4 Marks
one side of the joint.
Total (12) Marks
(ii) Manual metal arc welding produces high temperatures, too high for
light gauge sheet metal.
(iii) Work in well ventilated area and keep adhesives away from hands and face.
(iv) A is a castle nut which can be locked in place by inserting a pin through any
of the top grooves. B is a wing nut which can be loosened by hand.
(c)
Any three terms
(i) Oxides
Oxides (rust) are produced when oxygen reacts with the surface of a
metal, heat speeds up the production of oxides. Oxides must be
removed from metal surfaces before soldering or welding.
Description
Award 3 @ 4 Marks
Total (12) Marks
9
(ii) Passive flux
A passive flux is non-corrosive and resin based. It prevents oxidation
during soldering. Suitable for electrical work and other applications
where it is not possible to wash away the flux from the joint afterwards.
(iii) Tinning
Tinning is the process of applying a thin layer of solder to the surface of
metals before sweating together. It is good practice to tin the tip of a
soldering bit before soldering.
(iv) Chemically clean
The surface of a metal reacts with the atmosphere to produce an oxide
coating on the surface of the metal. This oxide coating must be removed
for successful soldering. Chemically cleaning is using an active flux to
dissolve away the oxide coating, this allows the tin in the solder to form
an alloy with the surface of the metal.
Reasons
Award 2 @ 3 Marks
Total (6)
(d) Two reasons
(i)
Dark goggles must be worn to protect the eyes from the bright light
produced by the flame.
(ii)
To protect the eyes from molten spelter which can often splash / spit out.
Question 5
(45 Marks)
(a) (i) Names
A
B
-
Vacuum Forming
Blow Molding
Name
Award 2 @ 2 Marks
Total (4)
(ii) Main Differences
Vacuum forming (A)
Used to produce articles from flat thermoplastic sheet. A pre-designed
manufactured 3D mould is also required. The flat sheet is clamped
Differences
Award 2 @ 5 Marks
Total (10)
10
and a heater raises the temperature of the sheet until it becomes soft and
flexible. The mould table is raised and air is removed from beneath the
sheet allowing atmospheric pressure to push down, forcing the sheet to
take up the shape of the 3D mould. When the mould table is lowered the
vacuum formed sheet can be removed for finishing.
Blow Moulding (B)
Used to produce articles from a heated thermoplastic tube called a parison. The
article is moulded by the internal shape of a split mould. The mould closes around
the extruded parison and air is blow inside forcing the parison out against the wall
of the mould. The component is allowed to cool before being removed from the
opened mould.
(iii) End - product
Vacuum forming can be used to produce car bumpers / baths.
Blow moulding can be used to produce water bottles / plastic bins.
(b)
End-product
Award 2 @ 2 Marks
Total (4)
Two safety precautions
A plastic cup takes up to 50-80 years to decompose. Plastic bags and
other plastic waste which makes its way into the sea kills as many as
1 million sea creatures every year. Waste plastics should not be
disposed of with land fill refuge.
Safety precautions
Award 2 @ 3 Marks
Total (6) Marks
Careless disposal of plastics causes serious threat to the environment.
Identification of plastic types can help when recycling. Always separate
plastic waste into biodegradable and non- biodegradable.
(c)
Any three
(i) Laminating
High strength plastics can be produced by impregnating sheets of
paper or cloth with a resin. Layers of this material are bonded by
allowing the resin to set into a solid structure. Heat and pressure
are often used in this process.
Explanation
Award 3 @ 5 Marks
Total (15) Marks
(ii) Adhesives
Adhesives are glues which can be used to join plastics. They provide a
strong permanent joint distributing the load more evenly throughout.
Adhesives can withstand stresses caused by flexing and expansion of
joints. They can also provide a good seal for gases and liquids.
(iii) Strip heating
Strip heating provides local heating along a straight line. When used
11
on thermoplastics it softens the plastic along a line allowing the formation
of straight or small curvature bends in thermoplastic sheet material. A strip
heater can be used to strip heat plastics.
(iv) Dip coating
Dip coating is a process of coating a component with a protective thin layer
of plastic. Carried out in a plastic dip coating tank, the article is heated and
dipped into a fluidized plastic power. The plastic power melts and sticks to
the article providing an even coat all over. Articles made of steel such as
shopping baskets, kitchen utensils and dish washer holding trays are all dip
coated in plastic for protection against corrosion.
(d) Any two
(i) Polystyrene
(ii) Acrylic
Question 6
(a)
Material
Award 2 @ 3 Marks
Total (6)
(45 Marks)
Any three lathe parts
(i) Three jaw self centering chuck
(ii) Fixed three point steady
(iii) Four jaw independent chuck
(iv) Face plate
(b) (i) Two reasons
To improve surface finish
To allow faster cutting speeds
(ii) One safety precaution
Name
Award 3 @ 5 Marks
Total (15) Marks
Cutting fluids
Award 3 @ 5 Marks
Total (15) Marks
12
Change cutting fluid regularly to reduce rancidity
(c) (i) Names
Name & description
Award 3 @ 5 Marks
Total (15) Marks
A is the Rake angle
B is the Clearance angle
(ii)
Function of any one
Rake angle
Rake aids the removal of the chip being cut. Increasing the rake reduces the
amount of power consumed in cutting and also the amount of heat generated.
Clearance angle
The clearance angle ensures that only the cutting edge of the tool comes into
contact with the work. Without clearance, the tool would just rub against the
work without cutting.
OR
(c) Any three
Explanation
Award 3 @ 5 Marks
Total (15) Marks
(i) CAD
The term CAD, Computer Aided Drawing / Design, refers to the use
of computers in the production of 2D or 3D drawings. 2D dimensioned
drawings can be used for manufacturing while 3D drawings can be
used to help visualise design ideas.
(ii) Simulation
This is a means of performing a test run of a CNC program. The machining of
the component can be simulated on the computer screen. It allows the detection
of errors thus avoiding lathe damage and waste of material.
(iii) G Codes
Determine the tool path. The cutting tool will move in a particular way
depending on the number following the letter G. G01, for example, will
cause the tool to travel in a straight line.
(iv) CNC program
A CNC program contains co-ordinates for defining the positions that the tool
must move to during various operations, commands for controlling the tool
movement and commands for controlling the chuck. Distances perpendicular
to the lathe centre line are given as X co-ordinates and distances parallel to the
centre line are given Z co-ordinat
13
Question 7
(a)
(45 Marks)
Types of fit
A: Name: Clearance fit
A clearance fit results when the size of a shaft is smaller than the size
of the hole.
Name & description
Award 2 @ 5 Marks
Total (10)
B: Name: Interference fit
Interference fit results when the size of the shaft is larger than the size
of the hole
(b) (i)
(ii)
(iii)
(iv)
(c)
Nominal diameter of the hole : 30.00
Smallest diameter of the hole: 29.94
Largest diameter of the shaft : 30.08
Type of fit: Interference fit
Calculations
Award 4 @ 5 Marks
Total (20)
Any three
(i)
(ii)
(iii)
(iv)
Plug gauge
Height gauge
Feeler gauges
Surface plate
- for checking the size of holes
- for accurate marking out of components
- for checking the gap between two surfaces
- for marking out and checking flat surfaces
Name & application
Award 3 @ 5 Marks
Total (15)
OR
(c)
Symbols
Award 3 @ 5 Marks
Total (15)
Any three
(i) LED
(ii) Fixed resistor
(iii) Motor
(iv) Transistor
14
Parts 1 and 3
Part 4
Part 6
Parts 2, 5, 7 and 8
3
4
5
Part Number
All Parts of Project
2
Section
1
Subjective Marking 1 - 20
13 - 16 Very Good
8
2
3
Pictorial Sketch / Description
17 - 20 Excellent
7
5
9 - 12 Good
1
1 - 4 Very Poor
4
5
5
20mm Slot
42mm and 6mm Radii
External Profile
Lathe Work
Lathe Work
Part 7
Part 8
Lathe Work
Bench Work
20
20
20
20
Mark
20
100 Marks(× 1.5 = 150 Total)
4
4
4
8
2
Ø6mm and 8mm Holes
Marking Out
2
2
2
2
2
2
4
4
4
4
2
4
6
4
Mark
20
Marking Out
10mm Radii
M5 Tapped Holes
Ø10mm and 6mm Holes
Marking Out
10mm Radii
10mm × 10mm Steps
Internal Profile
Marking Out
20mm Slot
44mm Radius
25mm Radius
External Profile
Part 5
Part 2
Part 6
Part 4
Part 3
Part 1
Concept
Assembly, Function & Finish
Subjective Mark 1-20
5 – 8 Poor
Coimisiún na Scrúduithe Stáit
State Examinations Commission
Leaving Certificate Engineering Practical Marking Scheme 2011
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