Figure 1 is the structure diagram of the designed precision forging part. Because the tooth surface of the spiral bevel gear is arc-shaped and the metal material is not easy to fill the die cavity, the difficulty of the precision forging process of the part lies in the processing of the tooth shape. Chen Shuwan and Huang Sheng put forward in the research status of gears that the processes of Precision Forging Spiral Bevel Gears mainly include open die forging, closed forging and swing rolling forming. Different process schemes have different advantages and disadvantages; Liang Hao, Zhang Liqian and others developed the process scheme of “upsetting pre forging punching final forging” based on the principle of closed forging with central split flow. The forming condition and forming force of tooth profile are obtained through numerical simulation; Gao Zhenshan, Deng Xiaozhong and others studied the influence of preform parameters on the forming quality of tooth profile combined with the semi closed forging scheme.
Combined with the previous research experience, the spiral bevel gear is mostly formed by the method of central shunt (i.e. internal shunt), and its forming scheme is shown in Figure 2. A fixed distance (i.e. shunt gap) is set between the punch and the die to form a shunt cavity. The hydraulic press pushes the upper punch downward and acts on the preform to produce plastic deformation and fill the tooth cavity of the female die. In the process of forming the tooth profile, according to the law of minimum resistance, the internal particles always flow in the direction with the minimum resistance. Therefore, the metal material first flows along the radial direction of the shunting cavity, which is affected by the friction resistance of the punch and the die, and at the same time, it flows axially to fill the tooth cavity of the die. The extrusion as shown in Fig. 3 is formed by using the internal split flow forming process scheme.
The forming force of spiral bevel gear formed by internal shunting process is large. At the end of forming, the metal material may not be able to fill the die cavity. Therefore, based on the structural characteristics of parts, this paper puts forward the double split precision forging process scheme, and compares it with the inner split precision forging process scheme.
As shown in Figure 4, the structure diagram of double split forming process scheme is shown. Different from the internal diversion forming process scheme, the metal material flows radially along the internal and external diversion gap (i.e. two-way diversion) in the process of filling the tooth shape of the female die, and the internal and external flash occurs in the forming process. Affected by the friction resistance of the internal and external diversion gap of the male and female die, it also flows axially to fill the tooth cavity of the die, and finally complete the filling of the tooth shape. The extrusion formed by this process scheme is shown in Figure 5.
