关键词: 汽车门盖压合；开口超差；预压合优化；翻边高度；模具参数；精密制造

Abstract: This paper focuses on the failure of conventional pressure adjustment in hemming the outer panels of automobile doors and hoods due to factors such as the geometric characteristics of single parts, design styling, and improper adjustment of mold parameters. Through a combination of theoretical analysis and case validation, the study systematically reveals the influence mechanisms and optimization methods for hemming quality issues caused by small R angles on the flanging surface of single parts, the inherent warping characteristics of the clamping flanging process, material flow conflicts due to the convex arc structure of outer panel styling, and improper adjustment of hemming process parameters. The research shows that a small R angle can cause mechanical interference, necessitating the use of a welding pre-hemming process to adjust the R angle to a reasonable range. The inherent warping of the flanging surface in the clamping flanging process can be addressed by optimizing the R angle through welding pre-hemming and improving the stamping flanging process to control the warping amount. For convex arc-shaped surfaces, it is essential to balance the conflict between material accumulation and expansion, and shortening the flanging length can effectively reduce stress concentration. Mold parameter optimization requires collaborative adjustment of parameters such as mold pressure and the position of the bottom mold. Case validation demonstrates that after optimization, the hemming opening dimensions are stably controlled within the enterprise standard range (≤0.3 mm for four doors, ≤0.4 mm for two hoods). The study provides a systematic solution to enhance the failure issues of conventional adjustment in door and hood hemming openings.

Key words: automobile door and hood hemming; opening deviation; pre-hemming optimization; flange height; mold parameters; precision manufacturing