Development of Tool Paths for Multi-axis Single Stage Incremental Hole-flanging

In this paper, multi-axis single stage incremental hole-flanging is explored in place of three axis multi-stage tool paths in order to prevent flange conicity in hole-flanging by single point incremental forming (SPIF). The angle of inclination of the forming tool, the starting radius and step size of the tool paths are varied to investigate the feasibility of new tool paths. Using the proposed tool paths, an optimization is performed by Finite element (FE) analyses. The geometrical accuracy of the flange is maintained within tolerances relevant to industrial applications while minimizing the resultant forces acting on the tool and maintaining high formability (hole expansion ratio, HER). The FE analyses of the process reveal low formability and high forming forces for flanges formed at high angles of inclination of the forming tool. The tool paths with small diameters at the start point of the tool path result in high bulge heights and high resultant forces. Hence, the existing three axis tool paths are better than the proposed strategies. To prevent flange conicity, over bending of the flange edge to compensate for springback after forming is implemented on the three axis tool path strategy. This is achieved by adding a second tool path with an over bend angle at the end of the three axis tool path.