A Gear Cutting Predictive Model Using the Finite Element Method

Abstract Current processes for producing transmission gears involve hobbing, milling or shaping of a forged stock to obtain the gear shape. Gears are typically formed by hobbing tools made from solid tooling material, such as tungsten carbide, and have dozens of teeth. The gear hobbing process entails several teeth in cut simultaneously. Generation of in-volute tooth profiles results in varying chip loads from pass to pass. In this paper, details are provided for a finite element-based model of gear hobbing and milling processes. The model explicitly meshes gear cutter geometries with dozens of teeth. These cutters are used to simulate the complicated kinematic motion between tool and workpiece. Thermo-mechanical coupled calculations within an explicit dynamic formulation are per-formed on the tool and workpiece during chip removal. The complex geometry of involute tooth profiles results in complicated contact scenarios on the evolving workpiece geometry during tooth profile generation. Tooth-workpiece-chip contact is enforced rigorously and is particularly complicated with the confined space of gear hobbing. Advanced adaptive meshing strategies are developed and employed to maintain the resolution of the tool-workpiece interaction while multiple teeth are in contact. Cutting forces, temperatures and stresses in the tool and workpiece are predicted for steel workpiece materials. Models are validated through a set of initially simplified experiments where incremental complexity is added, allowing for direct comparison between predicted and measured forces and chip shapes.