Blending Adjacent Section-Contours in 3D Model Using Rotary Ray with Inner Center

To decrease the influence of the staircase effect to the shape and dimension precision of rapid prototyping part, a method of blending the adjacent section-contours in CAD model using rotary rays is explored in this paper. The current and the next section in CAD model were projected onto a horizontal plane, and the outer and the inner boundary were obtained by computing the sections´ union and intersection, and then the adjacent contours were blended by using rotary rays through proper inner point in the intersection to achieve the current layer´s scanning contour. Test shows that the method can realize the layer´s cusp distribution of the positive tolerance, the negative tolerance and the mixed tolerance, meeting the cusp tolerance distribution requirements of the parts applied in different situations, and expanding the cusp distribution connotation in rapid prototyping.