Abstract: An approach of milling force prediction for ball-end milling of 3D curved surfaces is presented. Based on the idea of differential, in one tooth period the cutting process of curved surface machining is considered as steady-state cut, in this case the whole process of curved surfaces machining can be treated as combination of small steady-state cuts. According to the coordinates of start/end cutter position of each small cut, the mathematical models of feed turning angle and feed inclination angle, which are taken to characterize feed direction, are proposed. The cutter engagement area is determined by a logical array based Zmap method. In addition, the parameter of undeformed chip thickness model is modified for fitting the variation of feed direction and cutter engagement in 3D curved surfaces machining. Three experiments for ball-end milling of convex arc surface, concave arc surface and freeform surface machining are operated. The results of numerical and experiments show that the feed direction and cutter engagement can be described well, and the predicted cutting forces are according with the measurements both in magnitude and in variation trend. Thus, the validity of proposed approach is confirmed.

Key words: Chip thickness, Cutter engagement, Cutting force, Feed direction