The Minimum Formable Radius of Subtle Feature Lines in Automotive Outer Panel Stamping

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.