Most automotive sheet metal parts are produced using cold stamping. In real-world manufacturing, these parts often suffer from various defects such as wrinkles, stacking, necking, rebound, trimming, burrs, crushing, and slip lines. Among these, part stacking can lead to scrap, affecting both quality and production efficiency. Based on my work experience, I will analyze the causes of these issues and provide practical solutions for automotive sheet metal stamping problems.
Li Likun, from the Technical Center of SAIC-GM-Wuling Automobile Co., Ltd., has dealt with several challenges in the stamping process. One common issue is the occurrence of material stacking after forming. This particular part shows a stacking defect in the red-circled area, which is a critical zone that needs to fit with other components. The stacking reduces the overall size of the body-in-white and may cause assembly problems if not addressed.
The root causes of the stacking problem include design factors and process parameters. From a design perspective, the shape of the part makes it prone to material gathering during stamping. If the material flow is not controlled properly, this leads to excessive accumulation and stacking. Additionally, the choice of stamping process plays a significant role. In this case, a forming process was used instead of a drawing process. While forming helps improve material utilization and reduce costs, it is less effective at controlling material flow compared to drawing. This limitation contributes to the stacking issue.
Another factor is the punching direction. The original stamping direction was not optimal for material flow in the stacking area, worsening the problem. To address this, we optimized both the part design and the stamping process.
In terms of design improvement, we added small ribs to the stacking areas in the digital model. These ribs help spread out the gathered material, reducing the risk of stacking. However, there were constraints: the ribs had to be carefully sized to avoid interference with other components and to ensure sufficient punch strength. As a result, the effectiveness of this approach was limited.
To further improve the situation, we also optimized the stamping process by adjusting the punching direction. The new direction allowed better material flow in the critical stacking zones, significantly reducing the stacking defect. This combined approach—design modification and process optimization—proved effective in solving the problem.
Through these changes, the quality of the stamped parts improved, and the likelihood of defects was reduced. This case highlights the importance of considering both design and process factors when dealing with common stamping issues in the automotive industry.
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