Bi-directional dieless incremental flanging of sheet metals using a bar tool with tapered shoulders

Flanging of sheet metals in a rapid and cost-efficient way is strongly needed in practice. This paper describes a flexible and versatile flanging method based on the single-point incremental sheet forming (ISF) technology utilizing simple bar tools with tapered shoulders in a two-stage procedure. The experiment and numerical simulation used Al 6061 sheets with a thickness of 1 mm. The results confirmed that forward/backward flanging of various open edges and hole rims of plates can be performed by this method without dedicated die. This gives a more complete flexible forming chain based on ISF. In contrast to conventional ISF, however, dieless incremental flanging gives particular force and deformation modes and might form different defects including plate warpage and buckling at flange onset. A larger inclination angle θ of the tool shoulder decreases the tendency of buckling but might incur larger warpage. The recommended θ-value for round-hole-flanging is 20-30°. Curved plates have less warpage versus planar ones because the curvature enhances structural stiffness. Moreover, control strategies of typical defects were presented mainly through the path optimization and geometry modification of tools.