Influencing geometric stability in free-form bending by exploiting non-tangential bending

Free-form bending is a kinematics-based bending process, which offers a wide flexibility for bending arbitrary 3D-geometries. Especially in the automotive sector, it can represent an optimal process for the bending of structural components in high strength materials from the prototyping up to the series production, due to the reduction of tooling costs and the ease of process adjustment. Nevertheless, it still requires a complex design of the kinematics of the bending die in order to obtain the part in the desired tolerance range. In this contribution, the effect of different kinematic strategies on the geometrical stability of the process is investigated. First, the principles of tangential and non-tangential bending (under- and overbending) are described. Successively, the strategies are tested on different semi-finished parts before and after different heat treatments to simulate inhomogenities in the materials. Finally, the results are discussed, and it is found, that the overbending strategy allows to reduce the fluctuations in the obtained bending radius and angle, hence improving the stability and reproducibility of the process.