Numerical and experimental investigations on the springback behaviour of stamping and bending parts

For the electrical industry, clamps and springs made from strips and wires are produced by stamping and forming technologies. To realise complex geometries, multi-stage stamping and bending processes with cycle rates of up to 500 parts per minute are utilised. In the field of small-sized components, the demand for load optimised lightweight structures made from high strength materials increases. Due to the complexity of forming processes and materials used for clamps and springs, FE simulation of those processes is a challenging task. The first objective of the presented investigations is a holistic view of the influencing factors of multi-stage stamping and bending processes for springs and clamps. Therefore, clamps from high strength spring steel (X10CrNi18-8) with a thickness of 0.30 mm are formed on a hand-operated stamping and bending machine. In the experimental and corresponding numerical investigations, the gap between the tools, the tool radii as well as tool strokes are varied to evaluate the effects on the bending results. The main influencing factor on the product geometry is the tool stroke. The second objective of this work is to examine the transferability of the obtained results to production conditions. On a production machine, tool strokes were measured using different cycle rates. Regardless the cycle rate, the measured tool strokes were up to 2% shorter than defined in the process design. Simulations with measured tool strokes significantly enhance the predicted geometry after springback. The comprehensive goal is to describe the required geometrical accuracy in the FE model while minimising the required investigations to receive real data instead of nominal one. Thus, the industrial implementation of FE models for stamping and bending processes is accelerated. (C) 2017 The Authors. Published by Elsevier Ltd.