Varying law of extrusion force in process of backward extrusion

By the aid of the comparison experiment of direct extrusion with backward extrusion, the varying law of extrusion force and the difference of maximum extrusion force between direct and backward extrusion were studied. The experiment results show that in backward extruding bars, the extrusion force increases with extrusion process and reaches the maximum value which is about 10% smaller than that in direct extrusion at the end of the extrusion process, and this phenomenon is opposite to that in direct extrusion; in backward extruding pipes, the extrusion force reaches the maximum value which is about 30% smaller than that in direct extrusion at the beginning of basic extrusion stage and then decreases with extrusion process and reaches a constant in end. This phenomenon is similar to that in direct extrusion.