Processes

Question 1

Line bending

Answer 1

Plastics can be formed using a strip heater to fold/bend at different angles

Question 2

Injection moulding- why use it?

Answer 2

Used in industry because it is costly to set up, mass production quickly and accurately

Question 3

Injection moulding process

Answer 3

Polymer granules fed into a hopper, a screw transports granules along the heating chamber and presses them against the walls so they melt faster, a hydraulic ram forces molten polymer through a sprue gate and into the mould which is rapidly cooled with water

Question 4

How is the mould released?

Answer 4

The walls of the mould opens and the injection mould is removed by ejection pins

Question 5

Extrusion moulding process

Answer 5

Polymer granules are fed into a hopper, feeds into a heating tube via an Archimedean screw, polymer melts and is pushes through a nozzle into a die mould, two halves of a mould close around the plastic tube, compressed air is blown through the tube forcing it into the sides of the mold, it cools and the halves separate releasing the product

Question 6

What is the extruded plastic tube called?

Answer 6

A Parison

Question 7

Vacuum forming use

Answer 7

Used to make unusually shaped products

Question 8

What is the angle called in vacuum forming

Answer 8

Draft angle, necessary to remove product from former (mould)

Question 9

Vacuum forming process

Answer 9

The former is placed in a vacuum former on top of the platen, a sheet of plastic is clamped above, the heater is turned on and softens the plastic until it is flexible and ready for forming, the heater is turned off and a lever moves the plastic sheet down/ the mould is moved upwards, the vacuum is turned on to create atmospheric pressure which forces the plastic against the former. Plastic is removed and trimmed

Question 10

Drape forming process

Answer 10

A thermoplastic is heated until soft and flexible then draped or pressed onto a mould, when cooled it keeps its shape

Question 11

Press forming process

Answer 11

A plastic sheet (often acrylic) is heated in an oven until soft, it is placed between a yolke and plug which press together, guide pins may be used to ensure accurate alignment

Question 12

Blow moulding process

Answer 12

Pellets are fed into a hopper followed by a large threat that is turned by a motor and molten pellets are fed into the mould, compressed air is forced into the mould which forces the plastic to the sides, when cooled it is removed

Question 13

3D Printing/ Rapid prototyping machine

Answer 13

A type of CAM machine that follows CAD and creates products by repeatedly laying material, a filament of plastic is fed into the machine and heated so it softens and sticks to the previous layer

Question 14

Name 3 types of filament that could be used

Answer 14

ABS, PLA, TPU

Question 15

ABS

Answer 15

A strong, durable and more impact resistant plastic that can be used for products requiring strength and flexibility

Question 16

PLA

Answer 16

A biodegradable plastic used for products requiring detail and accuracy

Question 17

TPU

Answer 17

Used to quickly make flexible rubber-like parts in low volume and is ideal in custom products like insoles, watch bands and prosthetics

Question 18

Rotational moulding process

Answer 18

Mould opens and is filled with powdered polyethylene or polypropylene and is closed, the mould is heated to 300°C and the mould is rotated so the powder is forced against the mould, cool air is blown into mould via fans then the mould opens and product is removed

Question 19

Rotational moulding use

Answer 19

Used for large, one piece, hollow parts like coolers