Freeform bending tool design for rectangular profiles and its influence on the process

Freeform bending offers a wide range of possibilities in terms of component geometries, material grades and profile cross-sections. In the field of circular solid and hollow profiles, the design of the tool is determined by the circular shape of the profile used. When using rectangular profiles, the cross-section of the tool cannot be easily obtained by an offset of the profile cross-section. The large tolerance ranges of the profile standards require compromises with regard to the shape and tolerances of the tool. Tests have shown that the design of the tool has a great influence on the quality of the component. Furthermore, the trade-off in the tool design can lead to unsuitable tool shapes leading to defects and damages on the profile. These are mainly wrinkling, cross-sectional deformations and strongly deformed profile corners, which in some cases form cracks in the material. In this paper, the influences of the tool design on the bending result and the defects of the profiles are investigated. For this purpose, several tool designs with different variants and combinations of the movable die and the fixed die are compared with each other.