Die surface design optimization accommodating springback assisted by an automatic surface generator

One of manufacturing problems in sheet metal forming is springback. This elastic recovery occurs when unloading the formed part off the tooling dies, resulting in shape inaccuracies. Optimizing the geometry surfaces of the tools can be used to accommodate the springback, so that after the unloading process, the formed part meets the target shape. This paper presents an optimization method to modify the geometry surfaces of the tooling dies based on springforward simulations assisted by an automatic surface generator during the process. In the optimization cycle, new sets of upper and lower die surfaces are required. An automatic surface generation method based on normal vector has been developed to create new finite elements of the new surfaces. The normal vector calculation of the deformed elements after springback generates new upper and lower surfaces with uniform gaps. The new generated elements can be used directly during the optimization cycle. For testing and verification purposes, the method is applied in various complicated surfaces. The test results show that this method is able to generate a uniform gap in a corner with 90 degrees angle, without discontinuity in any elements. The application in optimization to minimize the springback is conducted in hat- shape problem. The result shows that the automatic mesh generator works effectively during the optimization cycle. The distortion error after springback can be significantly minimized.