Extrusion is the process of reshaping a material by pushing it through a smaller or differently shaped opening (“die”). The material (“billet”) is loaded into a container in the press, then pushed through the die. The appropriate technique depends on a few factors such as type of material, size and shape of final product.
This technique can be put into two categories: Direct (“forward extrusion”) or indirect (“backward extrusion”). With direct extrusion (the more common technique), the ram and the die are located on opposite sides and the ram moves forward to push the material through the die. With indirect extrusion, the die is part of the ram itself.
The extrusion process can be performed using hot or cold material. Hot extrusion requires temperatures above the material’s recrystallization to make it easier to push through the die and is most effective for large parts and complex shapes. Cold extrusion requires room temperature (or near room temperature) and is most effective for softer materials.