Abstract: In order to study the effect of pre-hem steel stopping position on boundary roll-in, the hemming process of a front door was analyzed and modeled based on AutoForm. Relative stroke was defined to quantify the pre-hem steel stopping position. The analysis result was also verified by the experiments on the hemming machine, and a method of adjusting boundary roll-in was proposed based on the numerical and experimental analysis. The investigation shows that the boundary roll-in increases with the increase of the relative stroke, but the increasing process is non-linear. When the pre-hem steel has under stroke, the influence of the relative stroke on the boundary roll-in is relatively small. While a quadratic function fits the relation between boundary roll-in and relative stroke well when the pre-hem steel has over stroke.

Key words: automobile sheet, hemming, boundary roll-in, pre-hem steel, finite element analysis