Manufacture of High Precision Spur Gears With End Milling Cutters

A new method is proposed for cutting large module spur gears on NC milling machines, using end milling cutters. End milling eliminates undercutting and leads to a significant reduction of tooling costs. The method relies on the motion of a simple geometry tool rather than the shape of an expensive form tool to generate the gear profile. The tool center path is defined and computed for the standard 20 deg full-depth system. Tool steps are generated by a highly precise interpolation algorithm. The practical aspects of the method are also investigated to establish its feasibility. The computation of the maximum tool size shows that sufficient tool rigidity can be secured for gear modules greater than or equal to 10 mm. The Lewis equation is used to investigate the beam strength of the resulting tooth profile and generate data for the design process. Gears made by end milling are shown to be comparable in strength to those produced by shaping or hobbing.