In recent years, sheet metals tend to be customized and produced in small quantities. Traditional stamping requires a lot of cost and time in the production of dies. Incremental forming is highly competitive in customization because it does not require dies. However, the maximum draw angle limits the application of incremental forming. Multi-stage single-point incremental forming can effectively increase the formability of the sheet, i.e., the limitation of maximum forming angle. Nevertheless, tool paths in multi-stage single-point incremental forming are simple. Therefore the thickness distribution is not homogeneous, leading to possible material failure. This research investigated the deformation mechanism of multi-stage single-point incremental forming and proposed a strategy to optimize the thickness distribution with Bezier curves.

   In this research, finite element analysis was used to simulate the forming process of axisymmetric cone in multi-stage single-point incremental forming. In the traditional multi-stage single-point incremental forming, the first-stage profile is equal-angle linear profile. In this research, the Bezier curve was used to establish the curve profile. The curved profile are designed according to simulation results. By adjusting the thickness distribution in the first stage, the purpose of adjusting the final thickness distribution was achieved. The parameters of the curve profile were defined according to the relationship between strain and displacement, so that the thickness distribution was more homogeneous. This research applied the above strategy to form vertical round cups, which had a significant improvement in both thickness and formability compared to conventional methods.

Keywords: single point incremental forming, multi-stage forming, formability, thickness distribution, CAE