Remedies for Cutting Edge Failure of Carbide Hob due to chip Crush-Some Results of Evaluation by this Method in the Automotive Industry

摘要

Dry bobbing is friendly to the environment, increases productivity and decreases manufacturing cost, but it often suffers failure of the hob cutting edge or problems with the surface quality of manufactured gears' tooth flanks. In the previous report, a simulation method to calculate the clearance between hob cutting edge and work gear tooth flank during hobbing was developed. In this report, this simulation is applied to some practical industrial problems of dry hobbing, i.e. chipping failure of a carbide hob's cutting edge and coarse, scratched surface finishes on hobbed gears' tooth flanks-perhaps due to chip crush. The simulation explains the mechanism of such actual failures in detail. Based on the simulation, the Distance of Single Edge Cutting (DSEC) of a hob tooth is proposed to be an index of pinching and crushing of chips that could intrude into the clearance between hob cutting edge and work gear tooth flank. Influencing factors on DSEC are investigated, and the bases for finding countermeasures are shown. This method has been applied to some practical cases of problems in mass production of automotive gears, and good results were obtained.