Analytical model for free form radii after deep and stretch drawing using pressurised membranes

Deep drawing using pressurised membranes shows advantages when forming structured blanks. The forming accuracy of the production process MULTIBRAN was experimentally investigated by means of the forming of free form radii. The influencing parameters on the forming accuracy are: the pressure inside the membranes, membrane wall thickness, membrane material, sheet thickness, sheet material and the geometry of the cavity. An analytical approach for the calculation of the necessary pressure inside the membranes including the influencing variables was developed. With this equation the necessary pressure can be calculated within a spread range of 10%.