Abstract: To avoid the collision between the cutter’s bottom and the surface, a few measures are taken: Firstly, the feature of the collision is studied. A conclusion is drawn that the key factor for the collision-free is the efficiency of partitioning the collision area from the surface. Secondly, based on the geometry property of the cutting points, the arithmetic is proposed to partition off the potential collision area from the surface. Then, by using the tangent plane of the cutter contact point, the key points of collision are defined, which are independent of the cutter locative vector. Based on this feature, these key points can be used to calculate the cutter’s first location and become the restriction of correcting the cutter location. At the same time, the arithmetic for selecting the key points is designed. On the basis of these key points, the collision-free orientation of the cutter can be gotten. A study case shows that these approaches can not only realize the collision-free of the cutter’s bottom but also provide a favorable basis for the collision-free of the cutter’s blade or the shaft.

Key words: CAM, Collision-free, Flat-end cutter, Free-form surface, Tool path