Interpretation of bevel gear topography measurements

The bevel gear manufacturing process is characterized by several steps, beginning with gear design requirements and the optimization of meshing properties and ending with extending the cutting and grinding tool life. The rolling process of a gear set is currently optimized by simulating and calculating corrections for the generating movements of the cutter axis. The basis to calculate manufacturing corrections is a measurement of the flank topographies, obtained from the first cut gear. Therefore, the detected flank form deviations serve as the main issue in the subsequent simulations and calculations. Bevel gear metrology is based on a point-wise description of nominal flank geometry, which is not directly ‘visible’ since CMMs or gear measuring instruments (GMI) are able to scan rapidly across the bevel gear flank. This definition of nominal geometry is different from cylindrical gear metrology, which detects deviations through the recreation of the rolling process. Despite the different measuring methods, some of the evaluation parameters were taken over from the ‘cylindrical world’, which leads to several potential problems and misinterpretations. This paper presents common and uncommon evaluation methods, causing different topography results. These differences lead to specific correction calculations in the manufacturing process and impact the closed loop process in a significant way.