Hobbing Strategy and Performance Analyses of Linkage models for Non-circular Helical Gears Based on Four-axis Linkage

The application of non-circular helical gears has been largely restricted to their manufacturing techniques. For realization of their hobbing, a kind of hobbing strategy based on a four-axis linkage and some fundamental hobbing models have been built by a generating method of helical tooling rack. This method includes profile-linkage models and extra rotation models. Based on the strategy and the models achieved, eighteen kinds of schemes and functional models have been developed according to the variety of hobbing processes in profile movement, axial movement, and extra rotation, which have an effect on profile precision, axial precision and control performance. The effect is analyzed from the aspects of profile-hobbing performance, axial movement performance and extra rotation performance, by using a 3D machining simulation. Excellent strategy and models have been singled out progressively. Finally, the excellent strategy and model (constant revolving velocity of hob & constant axial speed for workpiece & extra rotation of workpiece) is obtained with the characteristics of high precision, high efficiency and ease of control. The excellent strategy and model have been demonstrated to be valid by hobbing tests. The results between the test for tooth flanks and the computer simulations are in good agreement. This work provides the options of schemes for the manufacture of non-circular helical gears, and will promote its application significantly.