Pressure determination of the backward cup extrusion process

Abstract

Extreme loading of the tool, especially of the punch, sometimes represents a limiting factor in applying the backward cup extrusion process. If the punch is not properly centered and guided, each disturbance can lead to instability of the extrusion process and damage or breaking of the punch. That is why it is of primary importance to calculate pressure (force) of the punch. To calculate the punch pressure, an approximate energetic method known as the upper bound method is applied in this study. For easier application in engineering practice the derived formula is presented in the form of diagram. Likewise, to meet the needs of design and calculation of the technological processes of forming by means of computer, an approximate formula is also proposed in the paper. It has been found that the discrepancy of the theoretical and experimental results is within the boundaries of acceptable error.