Extrusion is a manufacturing process where a billet of material is pushed and/or drawn though a die to create a shaped rod, rail or pipe. The process usually creates long length of the final product and may be continuous or semi-continuous in nature. Some materials are hot drawn whilst other may be cold drawn.

Perhaps the most interesting of these processes is the manufacure of pipe where not only is the outside diameter controlled but also either a fixed or floating die is also used to set the internal diameter and hence the wall thickness.

Commonly extruded materials are copper (pipe for plumbing), aluminium (various extrusion profiles for tracks, frames, rails), steel (rod, track) and a multitude of plastics (pipes, rods, rails, seals).

It is common in the plastic extrusion process to use plastic chip, which is then melted and rather than drawing the material through the die to squeeze the plastic out of the die in a similar fashion to the extrusion of toothpaste from a tube.

Extrusion has found a great application in Food Processing. Various products like pastas, breakfast cereals, ready to eat snacks, fry-ums etc. are now manufactured by extrusion.