Tooth Flank Scratching of Gears Due to Hobbed Chip Crush in Cutting Edge Clearance

Abstract

Dry hobbing has advantages such as high speed cutting, production cost decrease and environmental friendliness. however, scratching of tooth flank of manufactured gear becomes of problem, which is not serious for hobbing with cutting oil. In this report, state of scratching on tooth flank of hob cutting edge and of generated chip are observed and the corresponding hobbing state is analyzed using the simulation, that virtually constructs the state of generated chip flow over the rake surface of hob tooth and the clearance-change between the cutting edge and the tooth flank of work gear. Thin chips from the finish cutting edges of hob are crashed in the clearance between cutting edge of hob and tooth flank of work gear to produce scratching of tooth flank. The shrinking clearance leads to press and drag the crashed chip on tooth flank. The scratching due to crash of chips from rough cutting edges does not influence the finished tooth flank of gear. The state of scratching on wet-hobbed tooth flank is different from that of dry hobbing. The pale black mark on the clearance flank of hob teeth suggests the occurrence of chip crush.