Remedies for Cutting Edge Failure of Carbide Hob Due to Chip Crush: Some Results of Evaluation by This Method in Automotive Industry

Dry hobbing, for friendliness on the environment, for increasing productivity and for decreasing manufacturing cost, often suffers failure of cutting edge of hob or problems about the surface quality of tooth flank of manufactured gear. In the previous report, a simulation method to calculate the clearance between cutting edge of hob and tooth flank of work gear during hobbing process is developed. In this report, this simulation is applied to some practical industrial problems of dry hobbing, i.e. chipping failure of cutting edge of carbide hob and bad coarse scratched surface finish of hobbed tooth flank of manufactured gears, perhaps due to chip crush. The simulation explains the mechanism of such actual failures in detail. On this fact, the “Distance of Single Edge Cutting” 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 tooth flank of work gear. Influencing factors on it are investigated and the bases for finding countermeasures are shown. This method has been applied to some practical cases of problem in mass-production of automotive gears, and good result was confirmed.