The Numerical control(NC)machining and programming technique of the spiral rotor with large module and few teeth were studied.Milling process of the rotor with helicoid was carried out on the 4-axis NC machining centre with an ordinary ball-end milling cutter.The NC programme was obtained with the help of a computer.The geometrical model of the rotor was established in the software Pro/E.Through discreting the involute line and the cycloid,as well as calculating the contact point coordinate of the cutter an...