Integrated roughing, finishing and chamfering turning process of toroidal worm manufacture on a general CNC lathe

Abstract

The toroidal worm drives are widely used in heavy-duty transmission systems, such as the solar tracker. However, the existing manufacturing methods cannot meet the mass manufacture of toroidal worms and lack flexibility, which prevents the popularization and application of toroidal worm drives. Hence, this paper presented an integrated roughing, finishing and chamfering turning method for any type of toroidal worm manufacturing on a general CNC lathe. Firstly, CL (cutter location) data of flexible rough turning of the toroidal worm were calculated according to the internal profile on the symmetry shaft section of the enveloped gear tooth. The top circle, root circle, dual internal tooth profile, and the tool parameters were included to ensure the uniformity of rough turning CL data. Secondly, the grid data matrix of the tooth surface was constructed based on accurate spiral surfaces of the toroidal worm. Spatial discrete points were converted to polar coordinates and were projected to the symmetry shaft section by a rotational matrix to calculate the finish turning CL data. Thirdly, the intersecting line between the spiral tooth surface and the outline surface of a semi-finished product was iteratively calculated. The characteristic curve of chamfering was defined and subdivided on the symmetry shaft section. Then the CL data of chamfering were obtained by connecting the sequential and biased chamfering discrete points. At last, the NC roughing, finishing, and chamfering turning codes were generated with the taper thread turning instruction and the CL data of different stages. Simulation and experiment have been conducted on a general CNC lathe, the results show that the integrated method is effective and applicable in automatic toroidal worm turning. The method proposed in this paper can greatly improve the manufacturing efficiency of any type of hourglass worm, without a special four-axis linkage machine tool.