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A-Level Design > Plastic Manufacturing Processes > Flashcards

Plastic Manufacturing Processes Flashcards

1
Q

What is injection moulding?

A

A method of forming thermoplastics into complex 3D shapes.

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2
Q

What is the first stage of injection moulding?

A
  • Plastic granules are placed in the hopper.

- The granules fall through the hopper into the Archimedean screw.

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3
Q

What is the second stage of injection moulding?

A
  • The screw is rotated via the motor and gearbox.
  • The polymer is forced forwards towards the heaters.
  • The polymer becomes softened and is injected into the mould.
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4
Q

What is the third stage of injection moulding?

A
  • The hydraulic ram forces the softened polymer through the feedhole into the mould.
  • Pressure from the ram fills the cavity.
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5
Q

What is the fourth stage of injection moulding?

A
  • Once the polymer has solidified, the mould halves are opened.
  • Ejector pins release the product from the mould.
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6
Q

What is the fifth stage of injection moulding?

A

-The mould is resealed for another cycle.

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7
Q

Give three advantages of injection moulding.

A
  • Complex 3D shapes can be produced.
  • High volumes of consistent quality can be produced.
  • Metal inserts can be included in the product.
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8
Q

Give two disadvantages of injection moulding.

A
  • Initial setup costs are high.

- Moulds are expensive.

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9
Q

What is blow moulding?

A

A method of forming thermoplastics into shapes with a single opening.

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10
Q

Give an example of a product produced using blow moulding.

A

Drinks bottles

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11
Q

What is the first stage of blow moulding?

A

A tube of softened polymer is extruded vertically. (parison)

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12
Q

What is a parison?

A

The extruded thermoplastic used in blow moulding.

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13
Q

What is the second stage of blow moulding?

A

The mould halves close trapping and sealing the top of the parison.

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14
Q

What is the third stage of blow moulding?

A

Hot air is blown into the parison forcing it into the shape of the mould.

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15
Q

What is the fourth stage of blow moulding?

A

The polymer is cooled by the mould and released.

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16
Q

What is the fifth stage of blow moulding?

A

The mould halves are opened and the product is extracted.

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17
Q

Give two advantages of blow moulding.

A
  • It is a quick method of producing hollow products.

- Non-circular shapes can be produced.

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18
Q

Give three disadvantages of blow moulding.

A
  • Moulds are expensive.
  • Complex shapes are hard to make.
  • Triangles are hard to produce.
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19
Q

What is rotational moulding?

A

A method of forming thermoplastics by rotating a mould about a fixed central point.

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20
Q

What is the first stage of rotational moulding?

A
  • The moulds are loaded with a precise weight of thermoplastic.
  • The mould halves are then clamped together.
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21
Q

What is the second stage of rotational moulding?

A
  • The moulds are rotated about two arms though a heated chamber.
  • The continuous rotation ensures the plastic covers the whole mould.
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22
Q

What is the third stage of rotational moulding?

A

The mould is then moved to a cooling chamber.

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23
Q

What is the fourth stage of rotational moulding?

A

The mould is returned to the start where the moulds are separated.

24
Q

Give six advantages of rotational moulding.

A
  • One piece mouldings can be produced.
  • Both rigid and flexible shapes can be produced.
  • A large range of sizes can be produced.
  • Surface textures can be applied.
  • Moulds are cheaper since high pressures aren’t required.
  • Lower production runs are possible.
25
Q

Give a disadvantage of rotational moulding.

A

Only hollow shapes can be produced.

26
Q

What is thermoforming?

A

A form of vacuum forming that uses air pressure and a female mould.

27
Q

What is vacuum forming?

A

A process where thermoplastic is heated and pulled onto a simple mould.

28
Q

Give two advantages of thermoforming.

A
  • Low cost process

- Good for smooth shapes with additional detail

29
Q

Give three disadvantages of thermoforming.

A
  • Walls can become thinned where the material has been stretched.
  • Limited to simple designs.
  • Trimming is usually needed.
30
Q

What is extrusion?

A

A process used to produce plastic products with a uniform cross-section.

31
Q

What is the first stage of extrusion?

A
  • Thermoplastic powder is placed in the hopper and falls into a rotating Archimedean screw.
  • This pushes the material towards the heated section of the extruder.
32
Q

What is the second stage of extrusion?

A

The heaters soften the plastic which is forced through the die by the rotating screw.

33
Q

What is the third stage of extrusion?

A

The plastic is cooled by a water jet.

34
Q

What is the fourth stage of extrusion?

A

The product is cut to the required length.

35
Q

What is calendaring?

A

A process used to manufacture thermoplastic sheets.

36
Q

What is the first stage of calendaring?

A

The rollers are heated to just above the softening point of the thermoplastic.

37
Q

What is the second stage of calendaring?

A

The plastic is forced through the rollers which determine the thickness of the sheet.

38
Q

What is the third stage of calendaring?

A

The final roller cools the material.

39
Q

What is line bending?

A

A method of processing thermoplastic sheets that involves using a single heating strip.

40
Q

How are accurate bends achieved when using a line bender?

A

A bending jig is used

41
Q

What is compression moulding?

A

The main manufacturing process for thermosetting plastics.

42
Q

What is the first stage of compression moulding?

A

A preformed slug is placed between the two halves of the mould.

43
Q

What is the second stage of compression moulding?

A

The mould is heated to a temperature that causes cross links to be formed.

44
Q

What is the third stage of compression moulding?

A
  • The mould is closed onto the preform and the pressure forces out excess material.
  • The moulds are held closed under pressure giving the material time to cure.
45
Q

What is the fourth stage of compression moulding?

A

The product can ejected whilst it’s still hot.

46
Q

Give two advantages of compression moulding.

A
  • Startup costs are relatively low.

- There is little waste material.

47
Q

Give two disadvantages of compression moulding.

A
  • A preform has to be manufactured.

- Products can’t be overly complex.

48
Q

Give one way of identifying a product that has been injection moulded.

A

They often have ejector pin marks.

49
Q

Give one way of identifying a product that has been blow moulded.

A

There is often a sprue at the bottom of the product.

50
Q

Give one way of identifying a product that has been rotation moulded.

A

There will be seam lines where the mould halves have been joined.

51
Q

Which process would be used to manufacture a bottle?

A

Blow moulding

52
Q

Which process would be used to manufacture a bottle top?

A

Injection moulding

53
Q

Which process would be used to manufacture a bottle?

A

Calendaring with LDPE

54
Q

What is overmoulding?

A

Injecting a second polymer over specific areas of a component.

55
Q

What is twinshot injection moulding?

A

Injecting two polymers using two separate barrels but a single mould.

A-Level Design (8 decks)

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