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Plastics RM > Moulding Plastics > Flashcards

Moulding Plastics Flashcards

1
Q

What is the process of Line Bending?

A

Plastic sheet is heated along the line of the intended fold

Softened area is then bent shape using a bending jig for accuracy

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2
Q

What is used for Line Bending?

A

Line Bender or Strip Heater

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3
Q

How are acrylic sheets often bent?

A

Line Bending

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4
Q

What is the process of Vacuum Forming?

A

Plastic heated and mould moves close to it
Air is ‘sucked out’ to form a vacuum
Causes the hot plastic to be sucked onto mould
As temperature falls, a rigid impression of mould is formed
Vacuum Pump is turned off allowing air to enter
Former is lowered separating from final product

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5
Q

What is a former?

A

A wooden mould around which the softened plastic will be held by the vacuum until it has cooled

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6
Q

What is Vacuum Forming?

A

When a heated plastic is ‘sucked’ onto the former which forms the required shape

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7
Q

What is the most popular material used Vacuum Forming? Why is it used?

A

High-Impact Polystyrene (HIPS)

Cheap and easy to form

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8
Q

What size sheets can be formed in vacuum forming?

A

1.5-1.8m

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9
Q

What is the process of Yoke Moulding?

A

Use an oven set to 110 degrees to soften the material

The pressure from a close fitting yoke will hold the plastic until it has hardened

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10
Q

What is Yoke Moulding used for?

A

Making half shells which can be solvent welded together

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11
Q

Why is foamed PVC a good material to use?

A

Because it has a long working time once hot

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12
Q

What is Yoke Moulding?

A

Requires only one former to go inside soft plastic

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13
Q

What are typical materials used in Injection Moulding?

A

Polythene
Polystyrene
Polypropylene
Nylon

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14
Q

What is step 1 of injection moulding?

A

Plastic powder or granules are fed from the hopper into a hollow steel barrel

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15
Q

What is step 2 of injection moulding?

A

The heaters melt the plastic as the screw moves it along towards the mould

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16
Q

What is step 3 of injection moulding?

A

Once enough melted plastic has collected the screw forces the plastic into the mould

17
Q

What is step 4 of injection moulding?

A

Pressure is maintained on the mould until it has cooled enough to be opened

18
Q

How can injection moulding be done in school?

A

Hot glue gun

Simple mould made from 2 pieces of steel with a cavity between them

19
Q

What are typical materials used in extrusion?

A

Polythene
PVC
Nylon

20
Q

What are the steps of extrusion?

A

Plastic granules are fed into the hopper by rotating screw
Plastic granules heated as they’re fed through
Softened plastic is forced through die in continuous stream to create long tube
Extrusions are passed through a cooling chamber and cut to required length

21
Q

What are common materials used for blow moulding?

A

PVC
Polythene
Polypropylene

22
Q

How is Blow Moulding different to Extrusion?

A

An air supply and split mould is used instead of cooling chamber

23
Q

What is the process of Blow Moulding?

A

Air is blown into an extruded section of tube
Air forces plastic to the sides of the mould
Moulding is cooled and then opened to remove the product

24
Q

What is Rotational Moulding?

A

A rotational moulding machine is rotated continuously with heated thermoplastic power inside

25
Q

What is Rotational Moulding used to make?

A

Footballs
Traffic Cones
Storage Tanks

26
Q

What are the mouldings for Rotational moulding made from?

A

Polythene which has fire retardant qualities

27
Q

What are the steps for the process of Rotational Moulding?

A

Mould splits apart and the plastic is poured in
Heat applied while mould rotated
Plastic thrown outwards to inner surface of mould
On cooling, mould is opened up and product is ejected

28
Q

How are Thermosetting Plastics moulded?

A

Compression Moulding

29
Q

What are examples of plastic that can be moulded in Compression Moulding?

A

Phenol
Urea
Melamine Formaldehyde

30
Q

What happens in Compression Moulding?

A

A large force is used to squash a cube of polymer into a heated mould
The cube of polymer is in the form of power called slug

31
Q

What is used to press the mould’s together?

A

Hydraulic Press

32
Q

What are the different types of Saws?

A

Coping Saw - sawing curves
Hacksaw - sawing straight lines
Junior Hacksaw - sawing straight lines
Power Bandsaw - rotates a continuous strip of saw blades
Power Scroll Saw - reciprocating motion with the blade held in tension

33
Q

What are twist drills and jobber drills used for?

A

Drilling smaller diameter holes in plastics

34
Q

Why are twist drills and jobber drills unsuitable for drilling larger diameters?

A

They leave a ragged edge to the hole

35
Q

What planes that are specially adapted for plastics?

A

Block Plane

Surform

Plastics RM (12 decks)

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