Segmented blank holder concept to influence the forming zone during incremental bending

Decreasing batch sizes and a simultaneous increase in the number of variants are developments in production technology that can no longer be managed economically using conventional mould technology with rigid, product-specific functional surfaces for semi-finished products. Individual or even in-line reconfigurations of the tool’s functional surfaces are being investigated to meet production requirements. Moreover, the goal is to control these surfaces during the process to compensate fluctuations, e.g. in semi-finished products. Incremental swivel bending (ISB) is a process for flexible bending forming in which the bending moment is transferred to the semi-finished product by friction by means of the clamping surfaces of the blank holder. In addition to the geometric and mechanical properties of the semi-finished product, the contact normal force and friction are responsible for the size and shape of the forming zone. In this paper, established analytics are utilized to present a tool concept that enables the clamping force distribution to be specifically adjusted by means of adjustable segmented hold-down surfaces with a vertical degree of freedom and, as a result, the size and shape of the forming zone to be influenced. The potential for extending the limits of forming technology is then discussed regarding the numerically determined local strain distribution through the dynamic loading and unloading of the clamping surface segments during incremental forming with the overall goal to achieve an in-process controllable material flow during sheet metal forming.