Development of a new burr-free hydro-mechanical punching

A new burr-free hydro-mechanical punching is developed, which consists of mechanical half piercing and hydro counter punching. In this hydro-mechanical punching, hydrostatic pressure delays fracture initiation. Smooth holes without any burr and small fracture face in the sheared surface are archived. During development of hydro-mechanical punching, finite element simulations for mechanical half piercing and mechanical counter punching is performed, which lead the method of hydro counter punching. To verify the significance of hydro-mechanical punching, conventional punching is performed under similar conditions and relatively larger portion of fracture surface is detected in the punching hole. Despite the quality of sidewall is not good enough yet, it is possible to make the hole shaped upright, reduce the roll-over radius and minimize the fracture surface by the optimization of process parameters.