Analytical prediction of stepped feature generation in multi-pass single point incremental forming

Single Point Incremental Forming (SPIF) is a new sheet metal forming process characterized by higher formability, product independent tooling and greater process flexibility. The inability of conventional single pass SPIF to form vertical walls without failure is overcome by forming multiple intermediate shapes before forming the final component, i.e., Multi-pass Single Point Incremental Forming (MSPIF). A major issue with MSPIF is significant geometric inaccuracy of the formed component, due to generation of stepped features on the base. This work proposes analytical formulations that are shown to accurately and quantitatively predict stepped feature formation in MSPIF. Additionally, a relationship is derived between the material constants used in these analytical equations and the yield stress and thickness of the blank material, so that computational effort required for calibration of these constants can be minimized. Finally, the physical effects of the yield stress and the sheet thickness on the rigid body translation are further discussed.