Adaptive increment based uniform sheet stretching in Incremental Sheet Forming (ISF) for curvilinear profiles

Abstract

Incremental Sheet Forming (ISF) is a rapid prototyping based die-less forming process. In this process, curved end based forming tool deforms the sheet by a user-defined Numerical Control (NC) toolpath. This paper focuses on the formability response of the sheet stretching during the ISF process. The stretching in the axial direction primarily depends on the wall angle of the profile and the incremental depth. During the die-less deformation of the constant wall angle based geometries (truncated cone or pyramid); with each increment uniform stretching of the sheet occurs. However, in case of the variable wall angle-based geometries (curvilinear wall profiles), higher sheet stretching occurs at steep wall angles. Adaptive increment based strategy has been developed for the die-less forming of the curvilinear geometries so that uniform sheet stretching in the axial direction can be sustained. The response of the developed strategy towards sheet formability, equivalent stress and strain distribution has been investigated in this study. For implementation, the toolpath for the Finite Element Analysis (FEA) simulations (ABAQUS®) and experimentation has been defined using an in-house developed Computer-Aided Manufacturing (CAM) module. Experimental and simulation results exhibit the improvement in the sheet thickness and stress distribution.