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Design For Function > Manufacturing: Topic 3 > Flashcards

Manufacturing: Topic 3 Flashcards

1
Q

What do all moulding processes require?

A

Heat and force

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2
Q

Do plastics have good defined regions between viscous liquid and elastic solid?

A

Plastics have a poorly defined region between viscous liquid and elastic solid.

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3
Q

What are thermosets?

A

Long Chain Molecules
Chains linked together by strong chemical bonds
Process is irreversible

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4
Q

What are thermoplastics?

A

Long Chain Molecules
Chains attracted to one another by weak-intermolecular forces
Process is reversible

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5
Q

Two applications of silicon

A

High temp

High grade electrical properties

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6
Q

6 Polymer Processes

A 
Extrusion Moulding
Injection Moulding
Blow Moulding
Compression Moulding
Rotational Moulding
Vacuum Moulding
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7
Q

What is Compression Moulding?

A

Compression moulding is a method of moulding in which the moulding material, generally preheated, is first placed in an open, heated mould cavity.The mould is closed with a top force, pressure is applied to force the material into contact with all mould areas, while heat and pressure are maintained until the moulding material has cured.

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8
Q

What is Extrusion?

A

Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or pulled through a die of the desired cross-section.

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9
Q

What is Injection Moulding?

A

The shaping of rubber or plastic articles by injecting heated material into a mould.

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10
Q

What is Rotational Moulding?

A

Rotational moulding is a process used for producing hollow plastic products. Eg. Hollow sphere partially filled with hot polymer rotated at and cooled at the same time. Thus producing a hollow ball.

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11
Q

What is vacuum forming?

A

Vacuum forming is the process whereby a sheet of plastic is heated to a forming temperature, stretched onto a single-surface mould, and forced against the mould by a vacuum (suction of air).

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12
Q

What is Blow Moulding?

A

Blow moulding is a manufacturing process by which hollow plastic parts are formed. Heated plastic placed inside mould and then a burt of air expands that plastic to fit the mould shape.

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13
Q

Two types of semiconductors

A

N-type

P-Type

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14
Q

What re most semiconductors made from?

A

Silicone

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15
Q

Wafer preparation

A

Grinding
Slicing
0.5mm
Polish

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16
Q

What is Ion Implantation?

A

Ion implantation is a materials engineering process by which ions of a material are accelerated in an electrical field and impacted into a solid.

17
Q

What are rivets?

A

A short metal pin or bolt for holding together two plates of metal, its headless end being beaten out or pressed down when in place.

18
Q

What are fasteners?

A

A fastener is a hardware device that mechanically joins or affixes two or more objects together. Fasteners can also be used to close a container such as a bag, a box, or an envelope; or they may involve keeping together the sides of an opening of flexible material, attaching a lid to a container, etc.

19
Q

Joints with no fasteners

A

Tend to be cheaper, (no cost of fastener)

May be difficult to separate

20
Q

Joints with fasteners

A

Tend to be more expensive because of
– Fastener cost
– Preparation time (drill holes, tap threads etc.)
– Labour to assemble parts
Often easy to disassemble for maintenance or repair

21
Q

Adhesive Joining

A 
Joint is usually inseparable
Bond strength depends on chosen adhesive
Adhesives bond to surfaces in 2 ways
-- chemical attraction
-- mechanical interlocking
22
Q

Requirements for Good Joint

A

Intimate contact between adhesive and substrate

Absence of weak layers or contamination at the interface

23
Q

Adhesion Mechanisms

A

Chemical bonding
Physical attraction
Mechanical Interlocking

24
Q

Adhesive Bond Requirements

A

Surfaces of the adhesend must be clean
Adhesive in liquid form must achieve thorough wetting of the adhesend
Surfaces should not be perfectly smooth

25
Q

Adhesive Bonding Advantages

A 
Ability to join dissimilar materials
Ability to join thin sheet efficiently
Excellent for small delicate parts
Uniform stress distribution in joint
Weight savings over mechanical fastenings
Smooth external surfaces are obtained
Can absorb shock and some movement
26
Q

Adhesive Bonding Limitations

A

Joints generally not as strong as other joining techniques approximately 30 N/mm2
Adhesive must be compatible with materials being joined
Service temperatures are limited
Generally 130 to 200 ºC (can be as high as 350 ºC
Cleanliness and surface preparation a must
Curing times can be very long (sometimes)
Inspection of joint is difficult
Assembly speed restricted by adhesive setting time

27
Q

Welding

A

Joining process in which two or more parts are coalesced at their contacting surfaces by a suitable application of heat and/or pressure.
Used mainly for metals but can be used for plastics

28
Q

Fusion Welding

A

Fusion welding is a generic term for welding processes that rely upon melting to join materials of similar compositions and melting points.

29
Q

Solid State Welding

A

Usually requires heat and pressure
If done cold surfaces must be exceptionally clean and smooth
Good solid state joint has no interface region
Can have long cycle time

30
Q

Welding advantages

A

Provides a permanent joint
Joint can be as strong as parent material
Very economical
Can be done on site

31
Q

Welding disadvantages

A

Sometimes manually performed therefore can be expensive
High energy usage
Permanent bonding cannot be easily disassemble
Difficult to detect defects

32
Q

Brazing

A 
Usually butt or lap joints
Large area required for a good joint
Parts must be kept in alignment before and during brazing.
Entire interface is bonded
Filler metal is used
33
Q

Brazing Advantages

A

Several advantages over welding

    • Any metals can be joined
    • Brazing is quick and consistent
    • Multiple joints can be done in one operation
    • Less heat and power required
    • HAZ problems greatly reduced
    • Can braze joints that cannot be welded
34
Q

Brazing Disadvantages

A
    • Joint strength less than welded
    • Good joint is stronger than filler material but not as strong as base metal
    • High service temperatures can weaken joint
    • Colour of filler material usually not the same as base material
35
Q

Soldering

A

Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal.

36
Q

Soldering Advantages

A

Low energy input compared to brazing or welding
Variety of heating methods possible
Good electrical and thermal conductivity in the joint
Airtight and liquid tight joints possible
Easy to repair and rework

37
Q

Soldering Disadvantages

A

Low joint strength unless reinforced by mechanical means

Possible weakening of joint in elevated temperature service

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