Online Tool Wear Measurement for Hobbing of Highly Loaded Gears in Geared Turbo Fans

Abstract Continuous increase in flight passengers alongside with a high demand for fuel efficiency has led to the development of Geared Turbo Fans (GTF). Being a safety-critical part, the gearbox faces strong safety requirements that also account for sophisticated manufacturing processes and monitoring systems. One major issue is tool wear and the threat of tool breakage during the hobbing process. Due to the high costs of both the raw material and the tool, wear induced tool breakage is a major cost driver. Common practice today is to use each tool for a designated time, but in-situ online wear assessment would result in a major reduction of costs. Tool wear of hobs is not spread equally across all cutting edges; hence the assignment of tool wear to each blade would enable a monitoring system to analyze the individual tool life and predict its operational capability. This research paper discusses the general feasibility of a blade-oriented monitoring system for gear hobbing processes. A correlation between tool wear and effective power is found and analyzed. It can be shown that the respective position of the tool wear changes the effective power signal significantly. These findings enable further research on an online, model based and position-oriented tool wear monitoring system.