Past Paper Questions Flashcards by thomas Harkin

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

-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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Explain what ductility means.

Ability of a material to plastically strain without fracture.

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

-Metals and their alloys
-Polymers
-Ceramics
-Composites

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

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

and their alloys

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Define technological processing capability.

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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Define unit operation.

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

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What are the 4 categories of shaping operations?

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

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What is a machine tool?

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

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Explain the difference between thermoplastic and thermoset materials.

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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What properties should an ideal engineering polymer have?

Low density
Good strength to weight ratio
High corrosion resistance
Low electrical and thermal conductivity

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Describe the components of a typical extrusion machine.

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

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

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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Describe the key components of MIG welding.

-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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Describe the key components of TIG welding.

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

Applications
-Aluminium
-stainless steel

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

????

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Explain what Elasticity means.

Material returns to its original length when stress is removed.

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Explain what Hardness means.

Resistance to permanent indentation.

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What is the role of fibre in fibre reinforces composites?

Fibers are the reinforcement and the main source of strength

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

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

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

-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.

Compare the water jet cutting process to abrasive jet machining.

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.

Describe the following polymer processes:
-Extrusion
-Injection moulding

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.

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

Simplify and Standardise Components

Minimise Tolerances and Variability

Consider Material Selection Carefully

Design Reviews and Feedback

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

Subtractive - material is removed, milling, turning

Additive - materials added, 3D printing

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

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

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

-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:

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

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

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

Explain the term consumable electrode.

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

Why is Tungsten a suitable material for the electrode?

Tungsten resists melting.

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

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

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

shrikage -gas porosity -Misrun

Describe the continuous casting process.

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

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.

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.

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

Explain what a product life cycle is.

Discuss: 'Every technical design design has a manufacturing implication.'

Define an alloy.

Define a ferrous alloy.

Define a non-ferrous alloy.

Define a composite material.

Describe what a single-point cutting process is.

Describe what a multi-point cutting process is.

Describe what a shape generating process is.

Describe what a shape forming process is.

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

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

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.

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