Feed Rate Improvement for Face Hobbing on a Six-Axis CNC Bevel Gear-Cutting Machine

Abstract

Face hobbing is one of the two primary mass-producing methods for bevel gears. It is renowned for its high-quality contact and high production efficiency. This cutting method is widely used in the automotive industry. In contrast to face milling, face hobbing employs a more complex cutter system and cutting motions. These two methods used to be performed on different dedicated machines decades ago. Now, they are both integrated into modern six-axis computer numerical control (CNC) bevel gear-cutting machines. Modern CNC machines provide high precision and rigidity, enabling easier adjustments to cutting speeds through numerical codes (NC) programming, thereby improving cutting efficiency. While machine-recommended cutting feed rates are generally feasible, they may not be optimal. Engineers often need to manually adjust cutting speeds by monitoring cutting torque during the process. Additionally, the material removal rate (MRR) is vital in determining cutting torque. Although automatic optimization of feed rates based on the MRR is technically feasible, accurately determining the MRR for face hobbing has proven challenging. This article introduces a new ring-dexel-based cutting simulation method for face hobbing. The proposed approach calculates the MRR by simulating the removal volume and the planned feed rate. Experimental results reveal a nearly linear relationship between MRR and cutting torque, enabling accurate predictions of torque based on MRR. As a result, the feed rate was optimized, reducing the pinion machining time for the roughing process from 76 s to 43.5 s, while the ring gear machining time was reduced to just 1 min.