Extrusion

This process is used to produce items of uniform profile such as curtain rails and plumbing pipes. Plastic granules are fed from a hopper

through a die by a rotating screw. The plastic is heated in the chamber before it enters the die and cooled by air jets or water as it leaves the die.

The extruded products can be cut into lengths or coiled. Polythene, PVC and nylon are commonly extruded.