Experimental and finite element investigation of over-bending phenomenon in Double-Sided Incremental Forming (DSIF) of aluminium sheets

Abstract

Abstract Double-Sided Incremental forming (DSIF) is a flexible sheet forming method with increasing research interest in the last decade. It offers improved formability and accuracy over the conventional single point incremental forming (SPIF) although it accompanies with the possibility of tools losing contact during the forming process. Mounting a pneumatic supporting tool is an efficient solution. However, the tools may squeeze and over-bend the material when forming for a high wall angle. A possible reason may be due to inaccurate prediction of material thinning or the effect of tool deflection. This work uses a modified finite element (FE) model with dedicated toolpath design incorporated with simplified stiffness of tools and machine in order to reproduce the effect of system elasticity to the DSIF process with hydraulic supporting tool and evaluate the root causes of the over-bending problem. The numerical results are compared with experimentally produced components, focusing on the thickness evaluation and development of the tool deflection throughout the process. This comparison demonstrates the effect of the tool deflection upon the formed parts, including the geometric error and excessive deformation on the wall region. The conclusion suggests a need for a compensation based approach in the design of DISF toolpath and machine systems.