The process of extrusion is simply forcing a billet of metal through a shaped die to produce a continuous length of constant section similar to the die profile.   Lead was the first metal to be extruded as pipe in the early 19th century. (J.Bramahs patent in 1897)  The extrusion of copper really initiated the extrusion process as a high production process

There are two basic extrusion processes , Direct extrusion and indirect extrusion.  Direct extrusion is by far the most widely used process.  Indirect extrusion more efficient and produced higher quality products.

Aluminium and copper are most often extruded as complicated sections and pipes.   Virtually all metals and alloys can be extruded.   Extrusions can be solid or hollow.   Extrusions can be tapered or stepped by manupulating the die during the extrusion process.

Extrusion presses are generally hydraulically operated and the process is generally completed in a horizontal elevation.   An extrusion press can have a capacity of over 200 MN for extruding stiffer metals such as titanium or steel.   Hot metal extrusion involves preheating the billet prior to extrusion to reduce the work required to extrude the section.