Automatic 3D spiral toolpath generation for single point incremental forming

Incremental forming (IF) of sheet metal is emerging as a useful flexible manufacturing process for forming customized shapes, some of which may not be formable using conventional techniques due to limitations of tooling or forming limit. In IF, the toolpath has a significant impact on the geometric accuracy, surface finish, and forming time of the formed component. Toolpath generation techniques used until date are based on commercial CAM packages (Skjoedt, 2007, "Creating 3D Spiral Tool Paths for Single Point Incremental Forming," Key Eng. Mater., 344, pp. 583-590; Verbert, 2007, "Feature Based Approach for Increasing the Accuracy of the SPIF Process," Key Eng. Mater., 344, pp. 527-534) and do not allow the generation of 3D spiral toolpaths for freeform components with constraints on both surface finish and geometric accuracy while simultaneously minimizing forming time. This work exploits the similarities between incremental forming and layered manufacturing to develop a methodology for automatic generation of 3D spiral single point incremental forming toolpaths for forming symmetric and asymmetric components, considering specified constraints on desired geometric accuracy and maximum specified scallop height while reducing the forming time. To test the developed methodology, the scallop heights of components formed using the developed methodology are measured and compared with the maximum permissible scallop heights specified. Furthermore, the geometric accuracy and forming time of the components formed using the developed methodology and by the toolpaths generated using commercial CAM software are compared. It is shown that the toolpaths generated using the developed methodology form components with better or similar geometric accuracy as compared with that generated by commercial CAM packages and with scallop heights lesser than the maximum permissible scallop height specified by the user. At the same time, the developed methodology also reduces the forming time as compared with commercial CAM toolpaths. This methodology can handle symmetric as well as asymmetric shapes and is a critical step toward automation of the toolpath generation for incremental forming.