FEM-based quality analysis of multi-stage tool paths in single point incremental forming

Single-point incremental forming (SPIF) offers significant advantages in sheet metal forming due to its flexibility and reduced tooling costs. This study explores the influence of tool path strategies on the geometric accuracy of SPIF-formed truncated cones. A finite element method (FEM)-based investigation, validated by experimental results, was conducted to evaluate five tool path strategies: a single-stage approach and four multi-stage methods involving multiple roughing and finishing passes. The focus was on minimizing wall deviations and pillow defect, a common distortion affecting the bottom surface. FEM simulations showed that roughing-finishing strategies, especially the variable angle roughing and finishing approach (ModeMD in the paper), produced superior accuracy with a more uniform material thickness distribution while reducing springback effects. This methodology avoids direct bottom deformation, significantly mitigating defects induced by rigid body motion (RBM). Experimental tests on aluminum alloys (AA1050 H24 and AA5754 H111) with different tool radii confirmed the simulation results, highlighting the importance of adopting multi-step trajectories to improve SPIF accuracy and establishing ModeMD as a robust strategy to improve geometric precision and industrial applicability in SPIF processes. This approach offers a systematic pathway to optimize sheet metal forming processes, significantly reducing the dependency on extensive experimental testing through accurate FEM-based predictions.