In the blog on Direct Extrusion, we had pointed the main disadvantage of direct extrusion being the excess use of force due to friction between the cylinder and billet. Accordingly, to deal with this issue, whenever possible one can use indirect or backward extrusion, wherein comparative lesser force is required for extruding the material.
Indirect or backward extrusion is a type of metal extrusion process wherein the billet(work-piece) is kept inside the chamber, which is completely closed on one side. In this type of extrusion, the billet and the container move simultaneously whereas the die remains stationery. Extrusion dies are placed on the ram, which applies the force from the open end of the chamber. These dies are held tightly in position by the “stem” which is longer then the length of the container. The column length of this stem decided the ultimate length of the extruded metal.
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