A feature line, which is a narrow and long curved surface on a smooth panel, is an essential element of the exterior style of the car. However, it is difficult to make the feature lines accurately, especially with a small radius and a large angle, in a typical automotive panel stamping process. A simple stamping process to find the minimum formable radius of the subtle feature line for automotive outer panel manufacturing was employed. This study presented three methods to find the minimum formable radius of the feature line; analytical approach, finite element analysis, and experiments. The three approaches showed similar and consistent results. In the experiment, the minimum formable radius of the subtle feature line was 20 mm, 8 mm, 7 mm, and 4 mm, when the punch angles of 175 °, 170 °, 165 °, and 160 °, respectively. This study showed that no matter how well-engineered dies and punches, there are limits to stamping the subtle feature line in automotive manufacturing. The results of this study could be used in the design process and the die engineering process of automotive panel making.

特征线是光滑面板上的窄而长的曲面，是汽车外观风格的基本要素。然而，在典型的汽车面板冲压工艺中，很难准确地制作出特征线，尤其是小半径和大角度的特征线。采用了一种简单的冲压工艺来找到汽车外板制造的细微特征线的最小可成形半径。本研究提出了三种求特征线最小可成形半径的方法；分析方法、有限元分析和实验。这三种方法显示出相似且一致的结果。实验中，当冲头角度分别为175°、170°、165°和160°时，细微特征线的最小可成形半径为20 mm、8 mm、7 mm和4 mm。这项研究表明，无论模具和冲头设计得多么好，在汽车制造中冲压细微的特征线都是有限的。本研究的结果可用于汽车面板制造的设计过程和模具工程过程。