Plastic Processes

There are many processes used for moulding/forming plastic parts in everyday products.

Heat Forming


The simplest way to form plastic is to bend hot sheet material around a form to bend it into shape.


Injection Moulding

Injection moulding is one of the most common plastic forming processes, tiny plastic pellets are fed into a hopper which feeds a corkscrew. Whilst in transit, these pellets are melted by the heaters and are turned into a runny, liquid form suitable for injecting into the mould. This is injected at high pressure into the two part negative mould and briefly left to cool, the mould then splits and the product can be removed.

This moulding technique is very efficient as little operator input is required to operate the machine as it is mostly automated, no waste is produced as only the exact amount is injected into the mould and the process is very quick.

Compression Moulding

Compression moulding is another technique used as the machinery required is fairly cost effective. Again, the mould consists of a two-part negative mould where one part is attached to a hydraulic press and the other is a fixed, heated mould.

The operator has to measure out a precise amount of the required material and place it into the mould, the mould is then pressed together and the heated material changes shape to fill the mould cavity. From here, the product can be removed and cleaned up. This method is less efficient as an operator has to precisely measure out the material beforehand and then feed the material to the machine which is both time consuming and wasteful.


Rotational Moulding

Rotational moulding is used to form hollow objects such as ping-pong balls. Material is precisely measured and put into the mould cavity which is then sealed. The cavity is heated and spun in 2 axis; X and Y. This spinning motion used centripetal force to form a 'shell' with walls of consistent thickness. This can then be removed from the mould and cleaned up. The thickness of the walls is determined by the amount of material placed in the mould at the start, this is why precise measurements are critical.

This is one of the only one-step ways to form a hollow object. Whilst it is fairly time consuming to measure out the exact amount of material and fill the moulds, it is a very reliable moulding technique and as such, is widely used in industry.