Accurate gear tooth surface machining is critical operation to achieve the low noise gear drive. Normally tooth rough surface is produced by face milling process, and then finished by tooth grinding process. The high speed face milling can produce high tooth surface quality as grinding with more productivity, but currently the accurate tooth surface cannot be obtained due to the use of simplified cutter geometric model used in tooth modeling. The accuracy of roughing gear tooth produced by face milling is also important. The cutter in finishing process can get benefit from the equally distributed remaining material on roughed stock. In this paper an accurate approach to modeling the genuine tooth surface for face-milled spiral bevel and hypoid gears is proposed.

In the first part of this work, a genuine cutter geometric model for the spiral bevel and hypoid gears is proposed. This model fully matches the real cutter used in industry. The side and circular cutting edges of the genuine cutter are defined on the blade rake plane, rather than the normal plane as the simplified cutter. In the genuine cutter modeling the rake angles and relief angles are taken into consideration. To compare the difference between genuine cutter and simplified cutter, the geometric errors of the simplified cutter are analyzed. The genuine cutter geometric model lays a ground for machining the accurate face-milled spiral bevel and hypoid gear tooth.

In the second part of this work, we build up the accurate spiral bevel gear tooth by using the genuine cutter geometric model. First, with the genuine cutter the member gear tooth surfaces are developed based on the kinematics of the non-generated gear tooth machining process, and then with the genuine pinion cutter geometric model the pinion tooth surfaces are modeled based on the kinematics of pinion generation process. The tooth surfaces of member gear and pinion are accurately represented as NURBS surface by optimizing the number of sampling and control points. The NURBS tooth surface can be directly implemented into CAD software, and provide the accurate geometry for the following FEA process. Finally the tooth geometric errors are calculated, and the tooth contact of the genuine gears is compare to the tooth contact of simplified gears.

In the third part, the accurate tooth surfaces of hypoid gears are built up. Similar to spiral bevel gear tooth modeling process, first the tooth surface of member gear is modeled with genuine cutter, and then the pinion tooth surface is generated, and finally tooth contact of genuine gears are compared to the tooth contact of simplified hypoid gears.

In this work an accurate approach to modeling the genuine tooth surfaces of genuine tooth surfaces for the face-milled spiral bevel and hypoid gears is proposed. With accurate surface model, high speed face milling process becomes possible to be used as the gear tooth finishing process. When the accurate gear tooth surface is used in gear roughing process, the remaining material and residual stress on the roughed stock are distributed equally. It can decrease the workload on the finishing cutter, thus the cutter life is prolonged. The accurate NURBS gear tooth surfaces can also be conveniently used by the FEA process.