Numerical Investigation of Multistage Toolpath Strategies Enhanced Formability and Thickness Distribution in Single-Point incremental Forming

Abstract

This study investigates the effect of multistage toolpath strategies on formability, thickness distribution, and dimensional accuracy in the multistage single-point incremental forming of aluminum sheets. The primary objective was to enhance formability, mitigate localized thinning, and enable the fabrication of conical parts with large wall angles. To this end, three-dimensional finite element simulations were performed using Abaqus/Explicit and validated against experimental results. Spiral toolpaths were developed in MATLAB, and the effects of different multistage forming strategies on strain-path evolution and sheet-thickness distribution were evaluated. In addition, a tensile fracture forming-limit criterion was employed to predict ductile failure and determine the formability limit. The numerical results showed good agreement with the experimental data, with a maximum thickness prediction error of 3.26% and a dimensional error of less than 3% for the final part. The results demonstrated that the multistage strategy alters the strain path from an approximately linear to a nonlinear trajectory and redistributes shear strains along the part wall, thereby reducing stress concentration and improving formability. Consequently, larger wall angles could be achieved without premature failure. Furthermore, incorporating a final corrective stage into the toolpath effectively reduced the undesired bottom bulging and improved the dimensional accuracy of the formed geometry.