Springback compensation of symmetrical and quasi-symmetrical sheet metal car body parts

Abstract

Springback compensation for symmetrical and quasi-symmetrical sheet metal parts presents specific challenges. The common approach involves modifying forming tools in the opposite direction of the springback to achieve dimensional accuracy. However, asymmetrical springback effects, such as twisting, can occur even in symmetrical parts. These effects should not be compensated, as they are typically unstable, whether numerical or physical. Numerical distortions can be avoided using symmetry boundary conditions in simulations, but this is not always advisable for quasi-symmetrical parts or symmetrical parts with low stiffness. In quasi-symmetrical cases, it is often unclear whether asymmetry arises from numerical artefacts or slight geometric differences. For theoretically symmetrical parts, ensuring symmetrical behaviour in reality is crucial before applying compensation. This paper analyses springback behaviour in symmetrical and quasi-symmetrical parts and presents a guideline for handling such cases. Quantitative criteria for applying asymmetric compensation are proposed. Additionally, methods are introduced to systematically induce asymmetrical springback to enhance stability.