Improved Spring-Back Compensation Strategy through Location Optimized Part Position in the Dies

Abstract

Further increasing requirements to the quality of car body components represent a huge challenge for the process planner. As the elastic energy is changing in each stamping operation, it is quite challenging to decide how to compensate which stamping operation. The belonging process definition is known as the compensation strategy. A key prerequisite of an appropriate compensation strategy is a proper location of the part in all stamping operations along the process chain. Proper means that the distance of the part to the die must be minimal to prevent any undefined shift of the part in the die and thus unwanted deformations when closing the dies. Both shifting and deformations would cause dimensional deviations and surface defects. Today different strategies are applied to meet these requirements at least approximately. Strategies, which are published in different papers yet, can only provide suboptimal results. Here a new compensation strategy is being presented, which fulfils the requirement to a proper part location not only in the trimming dies, which corresponds to the so-called Drawshell Strategy, but also in the restriking dies. An important advantage of the respective strategy is that it generally can be applied on all multistage car body stamping operations.

Advanced Springback Compensation Strategy through elimination of avoidable elastic strain energy

“…The so called Improved Springback Compensation Strategy [5] fulfils these requirements in a nearly perfect way. However, by applying this strategy, the time effort is huge, especially if the manufacturing process contains more than one additional operation after drawing.…”

“…Birkert et al [5] recommend an Improved Springback Compensation Strategy (Improved Strategy) through optimized part position in the dies. This strategy can be generally applied to all multistage car body component stamping processes.…”

“…2, different compensation strategies have different pros and cons with regard to general applicability, compensation amount, effort and complexity. The Improved Strategy described in [5] is the only strategy, which can fulfil the requirement of a general applicability, i.e. a reliable reduction of dimensional deviations of any car body component after compensation.…”

Holistic springback compensation procedure

“…A combination of the Advanced Strategy [17] and the Improved Strategy [16] is used here as compensation strategy. The optimized Physical Scaling Approach [14] is used for scaling the drawing operation and the physical compensation method [12] is used for compensating deviations normal to the sheet surface.…”

“…A unique and consistent approach was not presented. Such a consistent approach was presented in the so-called Improved Springback Compensation Strategy (Improved Strategy) [16]. In addition to a dimensionally accurate part at the end of the process, this strategy also makes it possible to achieve a stable part position when inserting the parts into the subsequent operation.…”