Multi-Step Tool Paths Development for Reducing Geometric Deviation and Pillow Effect in the Single-Point Incremental Forming

Single-point incremental forming (SPIF) process represents a good candidate in the Industry 4.0 panorama, whose paradigms of customized and small batch production require quick and cost-effective reconfigurations of manufacturing systems. SPIF enables the production of sheet components using simple equipment, consisting of a blank fixture and a hemispherical forming tool, without the need of dies. Despite its flexibility, this process presents springback-related drawbacks, which can limit its accuracy. Consequently, optimizing process parameters (such as feed rate, step-down size, and tool trajectory) is essential to mitigate these limitations. This study investigates how multi-step tool path strategies affect the geometric precision of walls and the occurrence of pillow defects during the incremental forming of AA1050 H24 aluminum alloy frustum cones. The findings from a comprehensive experimental campaign, which evaluated achievable geometry, applied loads, strain field, and thickness distribution, permitted the identification of best practices for improving the overall accuracy of the final product. As a result, a novel multi-step tool trajectory, concerning both a variable wall angle roughing phase and a finishing phase, has been identified as the optimal approach. This approach not only allows force reduction but also contributes to achieving a uniform thickness distribution. The results are encouraging, confirming the suitability of the proposed methodology and suggesting its diffusion at an industrial level.