Sheet Thinning Prediction and Calculation in Incremental Sheet Forming

Abstract

Incremental Sheet Forming (ISF) technique is an emerging process for die less forming. It has wide applications in many industries e.g., automobile and medical bone transplants. In ISF, forming of the sheet is done using Numerical Control (NC) single point forming tool, which incrementally deforms the sheet by highly localized plastic deformation. It gives better formability when compared with traditional forming processes, like deep drawing and spinning. ISF has few limitations out of which sheet thinning is one of the most critical limitations. In ISF, formability is generally measured by the limit of maximum formable wall angle and maximum permissible sheet thinning. Formability of the sheet during ISF or traditional forming processes can be presented by a Forming Limit Curve (FLC). The sheet thinning in ISF can be predicted through sine law. By assuming plastic incompressibility, sheet thinning can also be predicted by considering volume constancy concept. In this study, forming limit has been predicted for two wall profiles, viz., circular and elliptical wall. Further, a methodology has been presented as a way to predict and calculate sheet thinning during ISF. The developed methodology has been validated through numerical simulations followed by experimental investigations. An in-house Computer-Aided Manufacturing (CAM) module for incremental toolpath is developed for both simulations and experiments. The results are in correlation with considerable accuracy.