New design of the evolvent worm mill with carbide turning rack

Abstract

For high-speed cutting of teeth of cylindrical wheels made of structural and difficult-to-machine steels and alloys, cast iron, non-ferrous metals and various non-metallic materials with increased abrasive ability in conditions of mass and large-scale production, carbide hob cutters are used. A promising direction for hob cutters is the use of rotary racks as cutting elements. However, when they are rotated by 180°, errors in the tool profile are transferred to the workpiece. Therefore, the existing designs of such cutters are used only for roughing or semi-finishing, reaching accuracy classes B, C and D according to GOST 9324-2015. In order to improve their accuracy, the article proposes a new design of the assembled hob cutter with carbide rails, which allows maintaining the required tooth profile after turning the cutting elements. Milling cutters with flat front surfaces and back surfaces are adopted, the generatrix of which is perpendicular to the cutting edge. From the point of view of the working conditions of the cutting tool, studies of the kinematic angles were carried out. The calculation was carried out according to the formulas derived according to the scheme for the general option of cutting the wheel with a worm cutter. In this case, the working angles were calculated at points on the tooth profile at different moments of rotation of the cutter and along the entire length of the cutter. The analysis of the influence of the main parameters of the cutter on the cutting angles is presented. The possibility of using the design of a prefabricated worm cutter with flat front surfaces and back surfaces, the generatrix of which is perpendicular to the cutting edge, has been confirmed. Recommendations for achieving optimal working angles in the process of gear hobbing for milling cutters of the adopted design are proposed.