Process: Plastic pellets are fed into a heated cylinder and driven forward by a turning screw which compacts and melts them and forces the melt through a die at the end, creating continuous lengths of shapes with the desired profile. It is a system much like that of a mincing machine except for the addition of heat. Once the plastic shape is formed it is cooled by air or water
Introduced: First experiments in the 1840s, widely used from late 1930s
Plastics: any, especially high density polyethylene; polystyrene and polyvinyl chloride; all synthetic fibres
Marks: None
Tooling cost: Moderate
Production volume: High but restricted to minimum order lengths
Uses: Anything with a constant cross section: fibres; tubing; pipes; sheets; films; cable sheathing; profiles e.g. curtain rails or window frames