Influence of Tool Geometry, Straightening Strategy and Tool Clearance in Thin Wire Punch-Bending

In punch-bending of thin stainless steel components, the final product angle is significantly influenced by springback after process completion. In the present study, an attempt has been made to investigate the effect of wire straightening strategies and bending tool parameters on the springback behavior of cold-rolled EN 1.4310 flat wire (3.9 mm × 0.4 mm). The wire, supplied in coiled form with inherent residual stresses, was subjected to single-pass, two-pass, and four-pass three-roller straightening prior to bending. Tensile characterization was performed to examine changes in elastic-plastic flow stress behavior, and the experimentally obtained true stress–true plastic strain data were directly implemented in finite element simulations. A full factorial parametric study was conducted by varying the bending angle (66–90°), bending radius (1.33 mm–2.93 mm), and die-punch clearance conditions. Experimental investigations on a subset process parameters were performed to assess the simulation outcomes. It was observed that the straightening history modifies the springback magnitude. Among the parameters considered, the bending radius was found to be the dominant factor governing springback sensitivity. An increase in the clearance gap between the die and punch produces systematic and monotonic shifts in the final product angle due to an increase in the effective bending radius.