A New Approach to Blade Design With Constant Rake and Relief Angles for Face-Hobbing of Bevel Gears

Abstract

Face-hobbing is a productive process to manufacture bevel and hypoid gears. Due to the complexity of face-hobbing, few research works have been conducted on this process. In face-hobbing, the cutting velocity along the cutting edge varies because of the intricate geometry of the cutting system and the machine tool kinematics. Due to the varying cutting velocity and the specific cutting system geometry, working relief and rake angles change along the cutting edge and have large variations at the corner which cause the local tool wear. In this paper, a new method to design cutting blades is proposed by changing the geometry of the rake and relief surfaces to avoid those large variations while the cutting edge is kept unchanged. In the proposed method, the working rake and relief angles are kept constant along the cutting edge by considering the varying cutting velocity and the machine tool kinematics. By applying the proposed method to design the blades, the tool wear characteristics are improved especially at the corner. In addition, in this paper, complete mathematical representations of the cutting system are presented. The working rake and relief angles are measured on the computer-aided design (CAD) model of the proposed and conventional blades and compared with each other. The results show that, unlike the conventional blade, in case of the proposed blade, the working rake and relief angles remain constant along the cutting edge. In addition, in order to validate the better tool wear characteristics of the proposed blade, finite element (FE) machining simulations are conducted on both the proposed and conventional blades. The results show improvements in the tool wear characteristics of the proposed blade in comparison with the conventional one.