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MEC109 > Past Paper Questions > Flashcards

Past Paper Questions Flashcards

1
Q

Describe the following machining techniques:
-Peripheral/slab Milling
-Pocket Milling
-External Profile Milling
-Face Milling

A

-Peripheral Milling
Cutter Parallel to surface of workpiece.
Cutting edge on outside periphery of cutter.

-Pocket Milling - ?
-External Profile Milling - ?

-Face Milling
Cutter perpendicular to surface of workpiece.
Cutting edge on both outside and end periphery of cutter.

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2
Q

Explain what ductility means.

A

Ability of a material to plastically strain without fracture.

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3
Q

What are the 4 classifications of materials? Give an example of each

A

-Metals and their alloys
-Polymers
-Ceramics
-Composites

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4
Q

What is a non-ferrous metal? List 3 metals commonly used in engineering applications.

A

Metal elements and alloys not based on iron.
-Aluminium
-Copper
-Magnesium
-Zinc
-Titanium
-Nickel

and their alloys

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5
Q

Define technological processing capability.

A

The available set of manufacturing processes in the plant (or company)
 Certain manufacturing processes are suited to certain materials
– By specializing in certain processes, the plant is also specializing in certain materials
 Includes not only the physical processes, but also the expertise of the plant personnel
 Examples:
– A machine shop cannot roll steel – A steel mill cannot build cars

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6
Q

Define unit operation.

A

involve a physical change or chemical transformation such as separation, crystallization, evaporation, filtration, polymerization, isomerization, and other reactions.

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7
Q

What are the 4 categories of shaping operations?

A

-Solidification
-Particulate
-Deformation
-Material removal processes (subtractive manufacturing)
-Material addition processes (additive manufacturing)

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8
Q

What is a machine tool?

A

any stationary power-driven machine that is used to shape or form parts made of metal or other materials.

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9
Q

Explain the difference between thermoplastic and thermoset materials.

A

Thermoplastic - solid at room temperature, viscous liquid when heated to temps of a few hundred degrees.
-easily shaped.
-can be reheated without significant degradation.

Thermosets - cannot tolerate being reheated
- material hardens into an infusible solid
-doesnt soften when heated, it degrades.

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10
Q

What properties should an ideal engineering polymer have?

A
  • Low density
  • Good strength to weight ratio
  • High corrosion resistance
  • Low electrical and thermal conductivity
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11
Q

Describe the components of a typical extrusion machine.

A

-Hopper
-Turning screw
-Barrell
-Heaters
-Shaping die
-Final product

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12
Q

What are the advantages and disadvantages of welding compared to other types of assembly operations?

A

Advantages
-Provides permanent joint - becomes single unit.
-Most economical way of joining - doesn’t require mechanical fastening.
-Not restricted to factory environment - can be used on site.

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13
Q

Describe the key components of MIG welding.

A

-Uses consumable bare metal wire as electrode and flooding arc with gas for arc shielding.
-wire is fed automatically from spool through welding gun.
-Bare electrode wire and shielding gases eliminate slag on the weld bead.

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14
Q

Describe the key components of TIG welding.

A

-Uses nonconsumable tungsten electrode and an inert gas for arc shielding.

Applications
-Aluminium
-stainless steel

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15
Q

How would you expect the stress-strain curve to differ for a ductile material?

A

????

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15
Q

Explain what Elasticity means.

A

Material returns to its original length when stress is removed.

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16
Q

Explain what Hardness means.

A

Resistance to permanent indentation.

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17
Q

What is the role of fibre in fibre reinforces composites?

A

Fibers are the reinforcement and the main source of strength

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18
Q

What are the advantages of composites over metals traditionally used in engineering?

A

Composites cab be:
-Strong and stiff while being lightweight.
-possible to achieve combinations of properties unlike metals.

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19
Q

Explain the following 8 lathe operations:
-Facing
-Straight turning
-Taper turning
-Contour turning
-Form turning
-Chamfering
-Cut off
-Drilling

A

-Facing - uses a facing tool to cut a flat surface perpendicular to the work piece’s rotational axis. (cleans the workpiece end)

-Straight turning - the process of reducing the work diameter to a specific dimension as the carriage moves the tool along the work. (Same diameter along the whole piece)

-Taper turning - the process whereby a tool is given its gradual reduction/increase in diameter using a lathe. (to make a point)

-Drilling - Creates a round hole in workpiece.

20
Q

Compare the water jet cutting process to abrasive jet machining.

A

Water jet cutting process - uses high pressure, high velocity stream.
Abrasive jet machining - the water jet cutter with abrasive particles added to be used on metals.

21
Q

Describe the following polymer processes:
-Extrusion
-Injection moulding

A

Extrusion
-Only thermoplastics
-turning screw pushes plastic pellets through while melting by heaters.
-can form sheets, tubes or structural parts etc.

Injection moulding
-Thermoplastics and some thermosets
-ram retracts, drops pellets, forced by ram into heating chamber. Molten plastic forced under pressure into mould.

22
Q

Describe 4 guidelines one could take to promote design for manufacture.

A

Simplify and Standardise Components

Minimise Tolerances and Variability

Consider Material Selection Carefully

Design Reviews and Feedback

23
Q

What is the difference between subtractive and additive manufacturing? provide one example of each process.

A

Subtractive - material is removed, milling, turning

Additive - materials added, 3D printing

24
Q

Describe polymer materials with reference to a thermoplastic, a thermosetting plastic and an elastomer. (Compare molecular structures found in each materials)

A

3 types - thermosets, thermoplastics and elastomers.
Thermoset - cannot be remoulded
thermoplastics - can be remoulded
elastomers - rubbers - always recovers to original shape.

Molecular structure:
thermoplastic - Linear or Branched
Thermosetting plastics - Tightly cross-linked
Elastomers - Loosely cross-linked

25
Q

Describe the product life cycle of a plastic product (polymer).

A

-Development and Design:
-Manufacturing and Production:
-Distribution and Marketing:
-Utilization and Consumption:
-Maintenance and Upgrades:
-End of Life (Disposal or Recycling):
-End-of-Life Recycling and Repurposing:
-Regulatory Compliance and Adaptation:

26
Q

Describe the difference between shape generating and shape forming in the context of subtractive machining processes.

A
27
Q

In Peripheral/slab milling, explain the difference between up-cut and down-cut milling.

A

Uncut milling - Starts thin and gets thicker, longer chip.
Downcut milling - Started Thick and gets thiner, ship is shorter

28
Q

Explain the term consumable electrode.

A

Consumed during the welding process, it is the source of filler in arc welding. comes in rods or wires.

29
Q

Why is Tungsten a suitable material for the electrode?

A

Tungsten resists melting.

30
Q

Describe the sand casting process and explain the following associated terms for a closed-mould casting process:
-Cope and drag
-Pouring cup and downsprue
-Riser
-The in-gate
-Core

A

Pour molten metal into sand mould, solidify, break up the mould, clean and sometimes heat treatment to improve its properties.

-Cope and drag - contains sand
-Pouring cup and downsprue - where molten metal enters the process, Minimises splash
-Riser - a reservoir built into a metal casting mold to prevent cavities due to shrinkage
-The in-gate -
-Core - used during the process of sand casting if the piece has internal surfaces swell as external surfaces

31
Q

Defects may occur in casting. describe the following defects and how they can occur in the casting process:
-shrikage
-gas porosity
-Misrun

A

shrikage
-gas porosity
-Misrun

32
Q

Describe the continuous casting process.

A

used to manufacture stock materials - steel slab production is an example.

33
Q

Industry is sometimes categories into 3 types, primary,secondary and tertiary. describe each category and discuss the petty and clark law of how a country becomes a post-industrial or information society.

A

Primary - obtaining natural resources example fishing
Secondary - processing the raw materials into consumer/capitol goods example manufacturing
Tertiary - Called the service industry, examples education, transport

Petty & clark law - Where a country has to have at least 50% tertiary industry. if a country has less it is not called a post- industrial country.

34
Q

Describe 4 actions one could take to promote environmentally conscious manufacturing.

A
35
Q

Explain what a product life cycle is.

A
36
Q

Discuss:
‘Every technical design design has a manufacturing implication.’

A
37
Q

Define an alloy.

A
38
Q

Define a ferrous alloy.

A
39
Q

Define a non-ferrous alloy.

A
40
Q

Define a composite material.

A
41
Q

Describe what a single-point cutting process is.

A
42
Q

Describe what a multi-point cutting process is.

A
43
Q

Describe what a shape generating process is.

A
44
Q

Describe what a shape forming process is.

A
45
Q

Describe 4 types of chip that occurs in single point machining operations.

A
46
Q

Name two types of wear feature that can occur on a lathe cutting tool and mention the location of the wear on the tool.

A
47
Q

discuss the application cutting inserts that use tungsten carbide in a cobalt binding (WC-Co). specifically, discuss their application in terms of their suitability to different workpiece materials, trade-off in engineering properties obtained and the recommended cutting operations.

A
48
Q

Explain the different between up-cut and down cutting milling when cutting with a multi-pint cutter.

A

MEC109 (9 decks)

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