A new tool path with point contact and its effect on incremental sheet forming process

Incremental sheet forming (ISF) is a promising and flexible sheet metal forming process, which is appropriate for small batch production of complex parts and customized sheet metal parts. Although the formability of sheet metal in ISF can be significantly improved compared with conventional stamping, some low-ductility materials still cannot be formed to specific geometry through ISF at room temperature, such as magnesium alloy and titanium alloy. Besides, geometric deviation affects industrial applications. In the present work, a novel point-contact tool path (PCTP) method free of circumferential friction is developed. For better understanding the forming characteristic and deformation mechanism of this new tool path, the surface quality, geometric accuracy, and forming limit of the sheet metal are investigated through experiment and numerical simulation for different sheet materials and compared with conventional spiral tool path. Experimental results demonstrate that PCTP can obviously improve the surface quality and geometric accuracy by using small interval length. Besides, the forming limits of AA2024 and AA7075 sheets are improved dramatically due to the absence of circumferential friction, and an updated analytical model of stress triaxiality is developed based on membrane analysis to explore the increased forming limit of PCTP. This novel tool path provides a simple and feasible solution for forming low-ductility sheet metal components at room temperature.