A new sheet metal forming system based on the incremental punching, part 1: modeling and simulation

With the increasing demand for low-volume and customer-made products, incremental sheet metal forming (ISMF), a dieless sheet metal forming process, has become one of the leading R&D topics in the industry today. We developed a new ISMF system based on incremental punching: a sheet metal is formed into the final shape by a series of small incremental punches. This paper is the first of the two papers and is focused on the theory. The theoretical model consists of two parts. First, a mechanics model is developed to predict the final shape based on the minimum energy principle. In this model, an initial geometric surface is formed by the punch positions; then based on the fact that the energy will drive the sheet metal to attain its lowest energy position, the geometry of the final shape is derived. Then, another model is developed to predict the strain and stress distributions of the part using the inverse finite element modeling (FEM), also called the one-step FEM. Several numerical examples are provided. In the second part of the two papers, the design and the building of an incremental punching machine, as well as experiment results are given.