Effects of toolpath on defect phenomena in the incremental forming of thin polycarbonate sheets

Abstract The incremental sheet forming has been largely investigating in the last two decades because of its versatility and cost-effectiveness which make this technology especially viable for manufacturing highly customized parts, as well as small and medium-sized batches. One of its main strengths is that it allows reaching greater formability, compared to conventional sheet forming processes; in contrast, defect phenomena like twisting and wrinkling occur frequently and strongly influence the geometric accuracy of the formed parts. All these aspects are dramatically accentuated when forming soft materials like thermoplastics. With these premises, the following research aims to investigate the effects of the toolpath strategy on the occurrence of failures and defects in the incremental sheet forming under very severe process conditions; thin polycarbonate sheets were formed to obtain cone frusta with a fixed wall angle, imposing four unidirectional helical trajectory-based toolpaths, one traditional and three stair strategies. The analysis of the forming force trends, the evaluation of the worked surface quality and the monitoring of the defectiveness highlight understanding the advantages of an appropriate toolpath strategy to improve the accuracy of the incremental sheet forming of thermoplastic parts.