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From Flashcardlet > Engineering - Processes > Flashcards

Engineering - Processes Flashcards

0
Q

What are the 5 materials used in injection moulding?

A

Polystyrene

Nylon

Polypropylene

Polythene

ABS

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1
Q

Describe injection moulding

A

Granules of plastic powder are poured or fed into a hopper

A motor turns a thread which pushes the granules along the heater section which melts then into a liquid. The liquid is forced into a mould where it cools into shape

The mould then opens and the shape is removed

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2
Q

What are the 6 advantages of injection moulding?

A

Very complex 3D shapes can be produced

High volumes can be produced with consistent quality

Vary fast compared to other moulding processes

Little labour costs

Little waste

Little to no finishing of the parts is needed

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3
Q

What are the 2 disadvantages of injection moulding?

A

High initial set up costs

Moulds are expensive to make

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4
Q

Describe blow moulding

A

The plastic is fed in granular form into a hopper that stores it

Heated plastic granules are injection moulded into a pre-form shape which is positioned into a mould

Air is forced into the mould which forces the plastic to the sides giving a hollow shape

The mould is cooled and then removed

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5
Q

What are the 5 materials used in blow moulding?

A

HDPE

LDPE

PP

PVC

PET

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6
Q

What are the 4 advantages of blow moulding?

A

Once set up, blow moulding is a rapid method of producing hollow objects

Well suited to low and high production

Many types of plastic can be used

Can be less expensive than injection moulding

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7
Q

What are the 4 disadvantages of blow moulding?

A

Limited to hollow parts

Moulds can be expensive

It is difficult to produce shapes that don’t allow easy extraction from the mould

Difficult to produce triangular shapes

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8
Q

Describe rotational moulding

A

Moulds are loaded with a precise amount of thermoplastic powder

The moulds are clamped together

The mould is then rotated in a heated chamber and the thermoplastic is melted. The continuous rotation ensures the thermoplastic covers all of the inside of the mould

The product is then extracted

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9
Q

What are the 5 materials used in rotational moulding?

A

Polyethylene

Polypropylene

PVC

Nylon

Polycarbonate

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10
Q

What are the 6 advantages of rotational moulding?

A

A hollow part can be made in one piece with no seen lines or joints

Ideal for rigid, tough and flexible shapes

No material waste

Different types of product can be moulded together on one machine

Surface textures can be applied by texturing the mould

Moulds are cheaper than for injection and blow moulding

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11
Q

What are the 2 disadvantages of rotational moulding?

A

Only hollow shapes can be produced and more complex shapes need injection and blow moulding

The plastic used must be ground down into a fine powder which takes money and time

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12
Q

Describe thermoforming

A

Sheet plastic is held securely between the 2 halves of the mould

The plastic is heated just above its softening point

The mould halves close and a vacuum is applied through the lower mould

The upper mould ensures the required amount of detail is achieved

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13
Q

What are the 4 materials used in thermoforming?

A

ABS

Polypropylene

Acrylic

Polycarbonate

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14
Q

What are the 2 advantages of thermoforming?

A

Low cost process

Works well when creating smooth shapes that need extra detail

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15
Q

What are the 3 disadvantages of thermoforming?

A

Deep moulds can result in thin and stretched parts of the product

Limited to simple designs

Trimming is often required creating some waste

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16
Q

Describe vacuum forming

A

A sheet of plastic is heated to a temperature ready for forming

A mould is pushed up into the plastic sheet

A vacuum is turned on and this pumps out all of the air beneath the sheet

The sheet has the shape of the former pressed into its surface

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17
Q

What are the 4 materials used in vacuum forming?

A

ABS

Polystyrene

Acrylic

Polycarbonate

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18
Q

What are the 4 advantages of vacuum forming?

A

Available to schools

Simple process

Can be made from a range of materials

Suitable for one-off and large scale production

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19
Q

What are the 3 disadvantages of vacuum forming?

A

Additional processing required to trim excess material

Moulds can’t have vertical sides

You can only have undercuts with special moulds

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20
Q

Describe plastic extrusion

A

Granules of plastic powder or granules are poured or fed into a hopper

A motor turns a thread which pushes the granules along a heater section

The heater softens the plastic which is then forced through a die

As the plastic leaves the die, it is cooked

The exercises product is then cut to the required length

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21
Q

What are the 4 materials used in plastic extrusion?

A

Plastics

Aluminium

Wood-plastic composites

Ceramics

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22
Q

What are the 2 advantages of plastic extrusion?

A

The best way to make long products with the same profile

Only requires simple dies

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23
Q

What are the 2 disadvantages of plastic extrusion?

A

Parts need to be cut to shape, assembled or drilled

Not suitable for one-off productions because it produces very long parts

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24
Q

Describe calendaring

A

Pre-mixed thermoplastic is fed into rollers

Rollers are heated to just just above thermoplastic softening temperature

The plastic is forced through a gap roller to determine the thickness of the final product

The final roller chills the material

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25
Q

What are the 2 materials used in this process?

A

Thermoplastics

Cellulose acetate

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26
Q

What are the 4 advantages of calendaring?

A

Produces long continuous rolls without joins

Excellent for producing large quantities of flat sheets

Can be combined with printing or lamination

Very good at handling heat sensitive polymers as it produces very little thermal degradation

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27
Q

What is the disadvantage of calendaring?

A

Suited to large scale production only

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28
Q

Describe compression moulding

A

Compressed plastic powder is placed between the 2 halves of the mould

The mould is heated to a temperature that causes the long chain molecules of the plastic to link together

The mould is held together for a period of time to allow all plastic to link

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29
Q

What are the 2 materials used in compression moulding?

A

Thermosetting plastics

Ceramics

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30
Q

What are the 5 advantages of compression moulding?

A

Ideal for thermosetting plastics

Long production runs

Low set up and mould costs compared with injection moulding

Little waste material

Ideal for creating solid parts with thick walls

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31
Q

What is the disadvantage of compression moulding?

A

Limited complexity of shapes produced

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32
Q

Describe dip moulding

A

A mould is dipped into a bath of liquid / molten plastic

The mould is removed from the plastic having been coated with a layer of the plastic

The mould is cooled and the end product is removed from the mould

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33
Q

What are the 3 materials used in dip moulding?

A

PVC

Polyurethanes

Latex

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34
Q

What are the 4 advantages of dip moulding?

A

Highly cost effective for short production runs

Prototypes and formers can be produced very quickly

No split lines in the final product

Suitable for large production runs

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35
Q

What is the disadvantage of dip moulding?

A

Limited to simple shapes

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36
Q

Describe blanking and piercing

A

When a sheet of metal has a hole punched through it, this is piercing

When a part to be used is punched out of a sheet metal, it is a blank

These processes require punches which use a shearing action

37
Q

What is the material used in piercing and blanking?

A

Sheet metal (usually aluminium)

38
Q

What are the 3 advantages of blanking and piercing?

A

Can produce many different shapes

Can be used for any sheet metal

High level of accuracy

39
Q

What are the 3 disadvantages of blanking and piercing?

A

Limited to size of stock materials

If the material is not fully utilised, there can be a lot of wastage

Restricted to sheet material

40
Q

Describe plasma cutting

A

Plasma cutting is a stream of ionised gas that becomes so hot it vapourises the metal being cut

It can be done with hand-held, manual or CNC control

41
Q

What is the material used in plasma cutting?

A

Any electrically conductive metallic metal (usually stainless steel or aluminium)

42
Q

What are the 4 advantages of plasma cutting?

A

Economical process when creating small batches

Provides smooth clean cuts

Sheet material thinner than 8mm may distort

Large range of materials

43
Q

What are the 2 disadvantages of plasma cutting?

A

Uses a lot of energy

High amount of waste

44
Q

Describe laser cutting

A

A highly accurate form of cutting and decorating materials using a fine beam of light controlled by a CNC machine

45
Q

What are the 4 materials used by laser cutters?

A

Card

Soft woods

Thermosetting plastics

Some metals

46
Q

What are the 5 advantages of laser cutters?

A

Can engrave or cut depending on the power output

Highly complex shapes

Suitable for batch production

Very accurate

More materials than plasma cutting

47
Q

What are the 4 disadvantages of laser cutters?

A

Can leave burn marks

Uses a lot of energy

High amount of waste

Not suitable for large scale production

48
Q

Describe 3D printing

A

Additive layer manufacturing to make 3D objects from a digital model

Material is heated, printed and then it cools quickly

49
Q

What are the 2 materials used in 3D printing?

A

Thermoplastics

Some metal alloys

50
Q

What are the 2 advantages of 3D printing?

A

Any designed object no matter its complexity can be printed

Great for prototyping until it is perfect

51
Q

What are the 2 disadvantages of 3D printing?

A

Illegal objects can be printed

Takes a very long time to print one batch

52
Q

Describe press forming

A

Sheet metal materials are loaded into a hydraulic press and clamped into the blank holder

The punch forces the material through the die to take the shape of the punch

53
Q

What are the 4 materials used in press forming?

A

Steel

Copper

Brass

Aluminium

54
Q

What are the 3 advantages of press forming?

A

High stiffness of final products

Can be carried out at room temperature

Suitable for medium and high production

55
Q

What are the 2 disadvantages of press forming?

A

High level of stresses needed to overcome resistance of metal being pressed

High tooling costs

56
Q

Describe sand casting

A

A pattern is made

Each part of the pattern is placed on a base board

A drag is placed over it

Sand is packed around the pattern

Mould halves are fitted together with locating pins

Molten metal is poured into the running gate

Once the metal solidifies, the mould is broken open

57
Q

What type of materials are used in sand casting?

A

Low melting points

Commonly aluminium, copper alloys, lead etc.

58
Q

What are the 4 advantages of sand casting?

A

Low cost process

Easy to operate

Advanced sand casting can produce very detailed and intricate parts

Flexible levels of production

59
Q

What are the 3 disadvantages of sand casting?

A

Can be labour intensive

Unit costs can be high when used for one-off production

Parts may be require a lot of finishing

60
Q

Describe high pressure die casting

A

Molten metal is poured into a chamber

An injection piston or plunger forces the molten metal under high pressure into the casting cavity

The pressure is maintained until the metal solidifies

Injector pins are used to push the components out of the die

61
Q

What are the 2 most common materials used in high pressure die casting?

A

Aluminium

Zinc

Usually low melting points

62
Q

What are the 4 advantages of high pressure die casting?

A

Suitable for metals with low melting points

Ideal for complex shapes

High level of detail can be achieved

Excellent surface finish

63
Q

What are the 3 disadvantages of high pressure die casting?

A

Expensive so it is only suitable for high production

Parts are not guaranteed to have high structural strength

Excess material requires additional trimming

64
Q

Describe sintering

A

Materials are crushed into a powder

The powder is compacted into a die which will give the product being made its final shape

The compacted shape is then heated so that the powder particles bond

65
Q

What materials are used in sintering?

A

A variety of metals, plastics, glass and ceramics

66
Q

What are the 4 advantages of sintering?

A

Good surface finish

No wasted material

Useful for processing materials that can’t be processed in any other way

Produce complex shapes

67
Q

What are the 3 disadvantages of sintering?

A

There can be problems with shrinkage

Allows use of otherwise waste materials

Requires many different stages

68
Q

Describe drop forging

A

Very large forces are exerted onto a pre-heated metal billet between the 2 die halves

It is used as a refining process large numbers of similarly shapes objects are needed

69
Q

What materials are used in drop forging?

A

Most ferrous materials

Some non-ferrous materials like aluminium and titanium

70
Q

What are the 2 advantages of drop forging?

A

Very strong products

Can be forged cold to reduce energy usage

71
Q

What are the 2 disadvantages of drop forging?

A

It can be very expensive

Significant dangers working with hot metals

72
Q

Describe wood laminating

A

Adhesive is applied to the face of each veneer

Each veneer is stacked on top of each other

Veneers are clamped into position in a die

The adhesive dries and the shape is formed

73
Q

What material is used in wood laminating?

A

Wood veneers (usually birch)

74
Q

What are the 4 advantages of wood laminating?

A

Suitable for different production scales

Range of thicknesses allowed

Creates strong and lightweight products

Can be combined with other materials to enhance properties

75
Q

What are the 2 disadvantages of wood laminating?

A

Involves many steps

Restricted to bends in a single direction

76
Q

Describe steam bending

A

Wood is steamed and softened by hot steam to make it more moist to make it softer

Once the wood is steamed it is more flexible

77
Q

What materials are used in steam bending?

A

Hard woods

78
Q

What are the 4 advantages of steam bending?

A

Has good aesthetic appeal

The most effective technique for bending solid wood

Can be done with simple equipment

Parts with strong weight to strength ratio can be produced

79
Q

What are the 3 disadvantages of steam bending?

A

Only high quality hard wood can be used

Not suitable for applications that require precision

The bend radius depends on the wood used

80
Q

Describe die cutting

A

The sharp edges of the cutting die are brought down on to a thin sheet material

The material can be cut, creased and perforated in one step

81
Q

What 4 materials are used in die cutting?

A

Card

PVC

PET

Polypropylene

82
Q

What are the 4 advantages of die cutting?

A

Low set up cost

Cost effective for batches

Many shapes can be cut with single step

Large batches produced very quickly

83
Q

What is the disadvantage of die cutting?

A

3D products need to be assembled by hand

84
Q

Describe brazing

A

The metal to be joined must be cleaned so that grease and dirt is removed

Flux is brushed along the joint to prevent oxidation taking place on the metal surfaces

Pressurised gas and air is fed through a nozzle and ignited

The joint is heated with the flame until it eventually becomes so hot that it becomes red in colour

A brazing rod (copper-zinc alloy) is pushed gently against the joint

The rod will begin to melt and run along the joint

This is done until the whole joint is brazed

85
Q

What are the 2 materials that are processed with brazing?

A

Copper

Steel

86
Q

What are the 4 advantages of brazing?

A

Low cost

Suitable for many production scales

Complex and intricate joints can be achieved

The bond is extremely strong

87
Q

What are the 3 disadvantages of brazing?

A

Requires a high degree of cleanliness

The joint colour is often different to colour of the material being joined

Not as strong as a welded joint

88
Q

Describe TIG welding

A

TIG generates heat via an arc of electricity jumping from a tungsten electrode to the metal surfaces to be welded

The heat is sufficient to melt the joint edges

The electrode is coated in flux which when melted prevents the joint from oxidising

89
Q

What are the 4 materials that are processed by TIG welding?

A

Titanium

Also: carbon steel, stainless steel and aluminium

90
Q

What are the 3 advantages of TIG welding?

A

Using electricity decreases sparks, smoke and fumes

Less contamination in the weld than brazing providing better quality joints

No tooling costs

91
Q

What are the 3 disadvantages of TIG welding?

A

Requires a lot of set up and is hard for new users to learn

More expensive and takes longer than some other types of welding

Requires quite a lot of skill and practice

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