AutoForm News

September 24, 2008

Springback Effects – Mühlhoff Ensures Production Reliability with AutoForm

Mühlhoff Umformtechnik GmbH ensures the production reliability of complex stamping parts with AutoForm simulation. Mühlhoff knows from experience that stamping parts with springback effects represent a high risk for the company, both with regard to costs and lead times. This cautious approach was again proven during the tool development for the roof reinforcement of the Volvo model.

Comparison of part geometry (red) with reference geometry green) before springback compensation (top) and after springback compensation (bottom).

Mühlhoff was working on a project for Volvo Cars Body Components. The goal was to design a die for a long, narrow stamping part, which showed considerable springback effects. There was no doubt for Mühlhoff that AutoForm simulation was the right choice to ensure production for this stamping. The first simulation result showed an insecure form stability caused by the insufficient stretching of the material. Taking the clamping and fixing points into account, the springback results showed a deviation of several millimeters compared to the target geometry. It was possible to compensate the springback, however the stable production of the stamping part was not yet ensured. Noise variables, such as material gauge thickness were the root cause. Subsequently, the whole process was analyzed with AutoForm-Sigma under the influence of fluctuating manufacturing parameters, in order to design it robustly. Springback compensation can be successfully performed and leads to a dimensionally stable stamping part, only if the process is robust. The tool compensation was realized using the findings of the AutoForm-Sigma analysis, and after four compensation loops the result was in accordance with the geometric specifications. The compensated CAD data generated by AutoForm software were directly used by Mühlhoff for milling.

The gauge fixture (including the clamping and fixing points) is used for checking the dimensional accuracy of the stamping.

Mühlhoff was able to save three tryout loops, which corresponds to the work-load of four weeks and its appropriate cost reduction. In addition, the planning reliability was much better, because parallel projects were not interrupted as frequently. For Mühlhoff, it is very important to ensure the production reliability of critical stampings with AutoForm simulation. AutoForm software delivers fast and significant insights which are crucial for successful springback calculation and compensation.