Abstract: A positioning strategy is presented to minimize the error range based on one parameter envelope theory for flank milling undevelopable ruled surfaces with cylindrical cutter and conical cutter. Based on three propositions, a global optimization theory of tool positioning is described in detail. Firstly, a positioning strategy of cylindrical cutter with least square is presented. Based on the method of cylindrical cutter, a posi-tioning strategy of conical cutter is presented subsequently. At last, two examples are given to verify the effectiveness of the developed flank milling technique. The results show that the two methods are accurate and effective.

Key words: 5-axis machining, Flank milling, NC machining, Ruled surfaces