Understanding Plastic Products in Cars11 May, 2018
The meaning of plastic moulding assumes the absolute basic meaning of the words ‘plastic’ and ‘moulding.’ It is the process by which plastics are shaped into the desired design by using a previously prepared rigid material (mould) that also assumes the said shape.
The plastic is usually molten before being poured into the mould and left to cool and solidify. There are various moulding techniques used which depend on factors like the type of plastic, the thickness of the desired product, product size and rigidity of the mould (ability to resist melting under great heat).
The most common plastic moulding techniques include:
- Plastic Injection Moulding – The plastic is molten then forced (injected) into the mould cavity it is meant to assume the shape of. It is popular in the mass production of small products like toys, utensils, and prototypes.
- Compression Moulding – Hard molten plastic is placed between two halves of a mould which are then pressed together. The mould halves are usually vertically placed. Once the slug is poured and compressed, it is then air-cooled before the moulded product is removed.
- Rotational Moulding – this is a more complex technique that involves rotating hollow spokes held centrally by a hub. The plastic is ground to a powder then poured on the spokes which then rotate slowly inside a furnace causing it to melt into the spokes. The mould is then transferred to a cooling room where it is sprayed with water.
- Blow moulding- This involves pouring molten plastic vertically into a tube before covering with the mold. The mould forces it to assume its shape resulting in a hollow product. The style is used for bottles and other similar containers.
Plastic moulding began taking shape in the 1930s but it was not until the 50s that it became popular on an industrial scale. Moulding basically differs from casting in that the latter does not use pressure to make the molten plastic assume the mould’s shape. Casting is used for materials that are less viscous when molten.