Aluminium Extrusion is a plastic deformation process of a pre heated aluminium billet which is forced to flow by compression through a steel or ceramic die with an aperture of a smaller cross-sectional area than the original billet.
There are two main methods of aluminium extrusion, these are:-
Direct Aluminium Extrusion
With direct aluminium extrusion the preheated billet is placed in a heated part of the
press called the container. Here, the billet is pushed through the die by ram
pressure. The direction of the metal flow is in the same direction as the
ram travel. During this process, the billet slides relative to the walls of
the container, resulting in a necessary increase in ram pressure to overcome
the friction between the billet surface and container liner.
Indirect Aluminium Extrusion
With indirect aluminium extrusion, the die located at the front end of a hollow stem
moves relative to the container. The die is either pushed through the container
or the container is pushed over the die. There is no relative displacement
between the billet and the container liner. Therefore one advantage of the
indirect extrusion process is that there is no friction, during the process,
between the billet and the container liner. The metal flow is more uniform
during indirect extrusion than direct. This usually relates to better section
uniformity along its length.