Ever wondered how plastic is moulded into the exceptionally useful things that we employ in our daily life? Is it as simple as melting plastic and lathering the sides of a mould with it and cooling it, much like chocolate? The answer, actually, is no. Moulding plastic is a little more complex than that. Plastic is made using a process often called plastic injection moulding.
What is this type of moulding
Plastic injection moulding is the method of manufacturing parts made of thermoplastic and thermosetting plastic by melting and forcing into moulds where they cool to form the desired object.
How does plastic injection moulding work?
The process of plastic injection moulding usually begins with an industrial designer or engineer who designs a product. This is followed up by the work of a toolmaker or mould maker who makes the mould to fit the design created. These moulds are metallic and usually made using either steel or aluminum. Using machines, they are made to acquire the exact shape desired by the design. Once this is done, the process of actually making the plastic follows. This involves thermoplastic and thermosetting plastic being fed into a heated barrel and mixed. This melted material is then forced into the cavity of a mould and there it cools and hardens to form the desired part.
Some characteristics of the process:
1. I uses melted and mixed thermoplastic or thermoset plastic as the base
2. It uses a plunger which acts like a screw or a ram to force the melted material in the mould
3. It makes a shape that is open-ended and has taken the shape of the cavity of the mould
4. It shows a parting line and gate marks on the finished products and the ejector pin marks can also usually be made out