Twin symmetry roll axial rolling: new method of plastic forming profiles demonstrated using manufacture of spiral bevel gears

When using conventional manufacturing methods for machining gears, the percentage of stock material utilisation in the finished article is low due to the amount of swarf removed during machining. In addition, the machining process itself may result in low tooth strength. Adopting a plastic forming method to produce gear forms can greatly enhance the mechanical properties of the product. The size of the automotive transmission driven by a rear axle spiral bevel gear which is used as a case study in this paper is larger than that usually manufactured by the plastic forming method. Objects of this size require high capacity hot forming equipment, and even then it is difficult to obtain a full profile. In this paper, a new method of plastic forming profiles: twin symmetry roll axial rolling is described using a spiral bevel gear as a case study. The technology was analysed by producing a three-dimensional model of the spiral bevel gear, and finite element analysis was used to simulate the process. It can be seen that the teeth were completely filled with a well defined outline and only a small amount of horizontal overfilling and vertical flash occurred because there was small contact area between the blank and rolls which minimised the rolling force.