Design of formed cutter for milling of the screw rotor with the tooth profile represented by discrete points

Formed milling is one of the most commonly used methods for rough machining of the screw rotors. To design the cutter for a screw rotor with the tooth profile represented by discrete points, a numerical cutter profile generation method was proposed. Firstly, based on the coordinate relationship between the cutter and the workpiece, series of intersection planes were constructed perpendicularly to the revolving axis of the cutter, and the plane-axis intersection points can be transformed to the workpiece coordinate system. Then, one contact point within each intersection plane can be achieved by use of the Golden Section method and cubic Bernstein-Bezier interpolation. Using the same procedure, the cutter profile can be obtained which has the number of points equal with that of the intersection planes. Finally, a cutter profile was generated for the circular arc screw rotor and its maximum deviation can reach sub-micrometers. From the computation process, it also can be seen that the proposed method is also of simple computation, easy application and good generality.