In gear hobbing, as in every cutting process, the predictability of such machining parameters as tool wear, cutting forces, etc., considering workpiece tool and production data is of immense research and industrial concern 1–12 . The generating-rolling principle governing the hobbing kinematics makes difficult the analytical approach of the tool wear. On the other hand, owing to their complex geometry, hobbing cutters are quite expensive and their extended exploitation becomes dominant. The variant chip formation on each cutting tooth during hobbing provokes different wear laws and usually leads to an unequal wear distribution on the hob teeth 6,12–15 . Hereby, through an appropriate tangential tool shifting a uniform wear on the hob teeth, before the sharpen- ing or the replacement of the tool can be reached. For this pur- pose, optimum values for the hob shift displacement and amount of gears per shift position have to be determined.
The restricted cutting performance of HSS tools does not fulfill the high cutting speed requirements of modern CNC hobbing ma- chine tools. This led among others to the application of Physically Vapor Deposited PVD coatings on such tools, which improved the performance of HSS tools at higher cutting speeds, and in- creased considerably the productivity of gear manufacturing 8,16 – 24 .
In the present paper models to predict the wear development in gear hobbing are introduced, whereas the chip generation in full cut and in the transient workpiece cutting regions is considered. The wear laws in the individual generating positions investigated in 6,13–15 are exhibited with the aid of the developed algorithm FRSWEAR and procedures to determine the optimum tangential shift amount are proposed. In order to enable the monitoring of the wear progress in the individual generating positions and the determination of the included in the wear describing equations constants, the fly hobbing with continuous axial feed was applied.