Analysis of the influence of the effective angles on the tool wear in gear hobbing

Abstract

Gear hobbing is one of the most productive manufacturing processes for cylindrical spur gears. The macro geometry of the cutting edge of a hob depends on the tool angles. The tool angles consist of rake angle, wedge angle, and clearance angle. Due to the relative motion between workpiece and tool, the tool angles change to the effective angles during the process. The tool angles have a significant influence on the abrasive flank wear and the heat transfer through the tool. The use of indexable insert hobs compared to conventional hobs offers geometric design freedom. In contrast to full profile tools, the tool clearance angle can be designed freely along the profile by using indexable insert hobs. By dividing the reference profile into at least one left and one right indexable insert, the rake angles of both flanks can be set independently. As a result, the use of indexable insert hobs offers a significantly increased variability in tool design. In order to predict tool wear, the influences of tool angle and cutting edge geometry on tool wear in gear hobbing with indexable insert must be investigated in more detail. Therefore, the objective of the investigation presented in this paper is to improve the cutting conditions by modifying the effective angles in indexable insert hobbing. In analogy tests, the influence of the effective angle on tool wear was investigated by a variation of the rake and clearance angles. Based on the outcomes of the theoretical and empirical investigation, a wear model was developed for the main wear mechanism of abrasive wear. The wear model was trained by analyzing the tool life through an analogy test and was validated in an industrial hobbing process with indexable inserts.