Optimization of a Classical Stamping Progression by Modal Correction of Anisotropy Ears

This work is a development from the INETFORSMEP European project. It was proposed to realize a global optimization of a deep drawing industrial progression (made of several stages) for a cup manufacture. The objectives of the process were the thickness decrease and the geometrical parameters (especially the height). This paper completes this previous work in the aim of mastering the contour defect. From the optimal configuration, we are looking for minimizing the needed material and the number of forming operations. Our action is focused on the appearance of undesirable undulations (ears) located in the rim of the cups during forming, due to non-uniform crystallographic texture. These undulations can cause a significant amount of scrap, productivity loss and undesired cost during manufacture. In this paper, this phenomenon causes the use of five forming operations for the cup manufacture. The focus is to cut down from five to two forming stages by defining an optimal blank (size and shape). The advantage is to reduce the cost of the tool manufacturing and to minimize the needed material (by suppressing the part flange). The envisaged approach consists in defining a particular description of the ears’ part by modal decomposition and then simulating several blank shapes and sizes generated by discrete cosine transformation (DCT). The use of a numerical simulation for the forming operation and the design of experiment technique allows to find mathematical links between the ears’ formation and the DCT coefficients. An optimization is then possible by using mathematical links. This original approach leads to reduce the ears’ amplitude by ten, with only fifteen numerical experiments. Moreover, we have downsized the number of forming stages from five to two with minimal material use.