An extruder can be compared to a toothpaste packaging: it consists of a long screw inside a barrel that by turning melts the plastic (usually in the form of pellets) and pushes it forward through a die. The die gives the plastic its desired shape. The product comes out in one continuous piece, like toothpaste would come out of a tube.

A complete extrusion unit also comprises a cooling unit where the product solidifies and gets its final shape and a cutting unit to cut the product into manageable pieces.