Onesided offsetting and smoothing algorithm for complex 3D trimming curve of trimming insert steel for automotive panels

Abstract

ABSTRACT Based on the offset of the feature inflection point, the one-sided offsetting and smoothing algorithm of 3D trimming curve is proposed for trimming insert steel of automotive panels. The core of the algorithm is to determine the curve’s 3D offset direction and its feature inflection point. It obtains the offset direction of 3D discrete point by cross-multiplying the trimming direction with the vector of the two adjacent points of the 2D projection of them. Therefore, the offset direction of the 3D curve is not unique, and each discrete point has its own offset direction. To avoid the curve distortion caused by excessive discrete point offset, only by offsetting the feature inflection points, that control the curve shape and trend, to improve the curve smoothness. The 3D feature inflection points in the plane and trimming direction are determined by the abrupt change in curvature and perturbation, so the offset curve maintains the original curve’s characteristics. Self-intersecting defects of the offset curve are eliminated by pre-offsetting the 2D projection points. The target points are obtained by offsetting the feature inflection points and distribution points, and the one-sided offsetting and smoothing curve is obtained by constructing the spline curve.