Manufacturing with polymers.

Question 1

Injection moulding process.

Answer 1

1. Thermoplastic granules into the hopper.
2. Rotation of the screw thread by a motor pulling the granules through the chamber and past electric heaters.
3. Heaters melt the granules and one there is enough charge of polymer is formed at the end of the screw. A hydraulic arm forces the screw thread forward injecting the liquid polymer into the mould.
4. The mould is water cooled, which enables the molten polymer to harden quickly.
5. The mould opens and ejector pins push the moulding out.
   * excess polymer is trimmed off and dimensional accuracy is tested using jigs.

Question 2

What is the purpose of injection moulding?

Answer 2

It is used when making complex parts such as toys.

Question 3

Blow moulding process.

Answer 3

1. The polymer is fed into the hopper.
2. The Archimedean screw pulls polymer through a heated section melting it.
3. The molten polymer is extruded as a tube, which is called a parison.
4. The mould sides are closed around the parison and air is injected into the mould forcing the polymer up against the sides of the mould.
5. Once it has cooled the mould is opened and the moulding is ejected.

Question 4

What is the purpose of blow moulding?

Answer 4

To produce bottles.

Question 5

Rotational moulding process.

Answer 5

1. Polymer granules are poured into the mould before it closed and sealed.
2. The mould is transferred inside an oven where it is heated to around 260-270 degrees celcius.
3. The mould is rotated around two axis (fewer than 20 per minute) coating the inside of the mould with a layer of molten plastic.
4. Once it has achieved correct thickness the mould is cooled by water or fan.
5. Finally when it cools it will shrink slightly allowing it to be removed easily.

Question 6

What is the purpose of rotational moulding?

Answer 6

Rotational moulding is used to produce heavy duty, seamless, hollow objects that need a large wall thickness.