Research on Simplification of Opposed Dies Shearing Process Utilizing Differential Pressure

Opposed dies shearing process proposed by one of the authors is based on the idea of smooth sheared surface formation utilizing a cutting mechanism and has excellent features not found in other shearing processes. This process involves two stages; after sufficient shearing between die and protruding die, a product part is separated successively by a knock-out punch, where knock-out timing is important to prevent fracture of the surface and burr formation. Therefore, this process requires use of a precise hydraulic press which facilitates this complicated action and exact knock-out timing. This requirement seems to prevent wide practical application of this process. Therefore, we propose a simplification of Opposed dies shearing process utilizing differential pressure. First, this idea was tested using a coil spring substituted for hydraulic pressure and its feasibility was confirmed. Secondly, a differential pressure mechanism was realized with a hydraulic press and straight shearing of mild steel was achieved. Basic phenomena of this method were studied and it was found that knock-out timing was controllable by varying the pressure difference. Furthermore, a die set unit utilizing this mechanism was developed and disk blanking of aluminium with a mechanical press was demonstrated.