Towards accuracy improvement in single point incremental forming of shallow parts formed under laser assisted conditions

Single point incrementally formed parts with a low wall angle geometry typically exhibit a manufactured geometry that significantly deviates from the design surface due to accumulated unwanted bulging deformation. Development of the bulge on the bottom of the part might result in wrinkling of the sheet at the bulged region which leads to higher forming forces and can even cease the forming process. In this study, the geometric inaccuracy of low angled parts is investigated by means of both Finite element analysis and an experimental campaign on a conical geometry. Deformation mechanisms in shallow sloped parts have been studied in detail and the tool-sheet contact area has been characterized both for low and high angled geometries. In a second phase, the laser assisted single point incremental forming process and its potential for improving accuracy are investigated. To obtain suitable process parameters for a warm forming condition, a transient heat transfer analysis is developed to simulate the laser movement on the conical geometry. Based on the simulated and experimentally determined tool-sheet contact zone, different laser spot positioning strategies have been used while the accuracy of the part and forming forces were measured. It has been observed that overforming of the cone wall is due to the continuous deformation of the sheet outside the contact zone which changes into underforming upon laser treatment. By selection of a proper laser positioning strategy a reduction of 42 % in bulge height is observed. This shows its effect in reducing radial forming forces.