Extrusion
Extrusion may also be a direct or indirect method.
Direct extrusion
Direct extrusion is the most common method of extrusion, can also be referred to as forwarding extrusion. Firstly, the billet that is to be extruded is placed in a heavily walled container. The billet is then pushed through the die using a ram or screw. It is known as forwarding extrusion because the billet and the ram are moving forward in the same direction.
Indirect extrusion
Indirect extrusion is also gone by the name backward extrusion. In this method, the billet and container move in tandem while the ram and the die remain stationary. This is accomplished by employing a stem, which must be longer in length than the container. In this way, the billet is forced through the stationary die. This method eliminates nearly all of the frictional forces，and the flow of the metal during the process is more homogeneous, so the performance of the product is more uniform.
