A Milling Method of an Enveloping Toroidal Worm on a CNC Turning Center

Abstract

To solve the problem of allowance equalization in the grinding process of an enveloping toroidal worm after turning by using the hindley worm turning method, a milling method was presented based on discretization of the spiral surfaces rather than the generating principle. The method is used on a CNC tuning center with a cylindrical end milling cutter rather than on a specialized machine tool. The material of the spiral grooves of the worm was removed layer by layer both in the tangential and the radial directions of the torus of the worm from the tooth top circle to the tooth root circle. The milling model was built, and the coordinates of the discrete points on the spiral surfaces were calculated according to the theoretical equations of the spiral surface of the worm. A series of feed positions X and Z of the milling cutter and the corresponding rotating angles C of the worm were determined for programming. The grinding allowance of a planar enveloping toroidal worm on axial sections was calculated and the trial manufacturing was performed. The allowance in the subsequent grinding process could be equalized and the manufacturing efficiency could be increased greatly.