Computer aided design of cutters for helicoidal surfaces

Abstract

The design of cutters is an important consideration for the manufacture of helicoidal surfaces such as extruder screw surfaces. These surfaces are produced mostly by milling processes using form cutters of end mill type, side mill type or disc type, such as side-and-face mill or grinding wheel. The methodology proposed in the paper addresses the problem of the design of cutters for the machining of helicoidal surfaces. Using the proposed methodology, the characteristic profile(s) of the cutter can be determined from the given cross-sectional profile and lead of a helicoidal surface. By sweeping this characteristic profile along an appropriate path or around an axis, the geometry of the specific form cutter can be obtained. Such a geometry could be a turning tool, an end mill, a side mill, a side-and-face mill or a grinding wheel, depending on the process adopted for manufacture. The proposed methodology can also be used to determine the geometry of the helicoidal surface that will be obtained by using a given cutter. In the paper, the procedure to obtain the geometry of the cutters for machining extruder screws is explained with illustrations.