Springback Feasibility for Efficient Compensation

In today’s car body engineering, the primary materials applied are high and ultra high strength steels as well as aluminum. These materials enable car manufacturers to design lighter cars which fulfill the increasing safety requirements. However, the application of these materials poses additional challenges. Forming parts made from high and ultra high strength steels and aluminum are more affected by springback than parts made from conventional deep-drawn steel. In addition, in order to remain competitive, engineers must find ways to reduce the engineering time required for part and tool production. Modern engineering addresses these challenges by applying stamping simulation.

Stamping simulation is used to verify formability issues, such as splits and wrinkles. In the past, the main focus when analyzing splits and wrinkles was on the drawing stage. In recent years, higher quality requirements have to be verified – one of the most important of them is geometrical accuracy. In particular, verification of springback and its countermeasure, springback compensation, are carried out regularly in car body engineering. Gained experience has shown that compensation is not an easy task. In order to carry out the compensation effectively, a set of requirements has to be fulfilled.

This set of requirements includes springback feasibility. The analysis of springback feasibility ensures that the defined process setup allows for efficient compensation in which there is no backdraft in the drawing tool and formability is not compromised. The latest AutoForm software release AutoFormplus R5.2 allows engineers to compensate part geometry early on in the engineering process.

During the advanced feasibility phase of the engineering process, a simple first process plan is defined. This process plan takes into account drawing and all secondary operations as well as springback while maintaining the focus on the drawing operation. The draw die is designed by using concept faces in order to verify if the part is feasible with respect to formability issues. When the complete forming process is determined, the springback of the final part geometry can be calculated.

These first springback results of the final part are applied on the geometry of the original part. Based on this compensated part geometry, the draw die geometry is updated automatically and if required, necessary modifications can be directly applied. The crucial issue is the possible appearance of backdraft in the draw die, which may result due to a significant difference between the compensated part geometry and the original geometry. In order to avoid backdraft, e.g. the tipping can be adapted. The adjusted process with the compensated draw die must be checked with respect to potentially newly introduced formability issues.

This approach ensures a reliable process setup which allows for efficient compensation. As a result, time and cost in engineering are substantially reduced and the risk of later costly changes is minimized. What is more, part and tool quality are enhanced.