processingdetails

Direct Extrusion

Direct extrusion, also be referred as forward extrusion, is one kind of the most common extrusion process and enables the production of semi-finished products such as films, plates, tubes or profiles in one process step. In the process of direct extrusion, the billet is placed in a heavy walled container and pushed through the die by a ram or screw. There is a reusable dummy block between the ram and the billet to keep them separated. The major disadvantage of this process is that the force required to extrude the billet is greater than that need in the indirect extrusion process because of the frictional forces introduced by the need for the billet to travel the entire length of the container. Because of this the greatest force required is at the beginning of process and slowly decreases as the billet is used up. At the end of the billet the force greatly increases because the billet is thin and the material must flow racially to exit the die. The end of the billet (called the butt end) is not used for this reason.