The basic forming process of spur gear has its own obvious advantages and disadvantages. It can only solve the problems existing in the precision forging process of spur gear in a limited way, and can not reach the level of industrial mass production. How to combine the advantages of a single process and solve the technical problems that can not be solved by the existing single process is the key research direction of spur gear precision forming.
Yu Shuqing, Yang Shenhua, etc. carried out cold precision forging process experiments on spur cylindrical gears made of 15 steel, 45 steel and 20CrMnTi by closed upsetting extrusion constrained split flow two-step forming method, which effectively reduced the forming load. Considering the different stress states at different positions of the final forging tooth die and the different elastic deformation and wear of the die, the modified design of the tooth die can not only improve the service life of the die, but also obtain high tooth dimensional accuracy.
Feng chongqian et al. Used the principle of floating die and hollow split flow method to form straight tooth cylindrical wheel by hot precision forging, upsetting and extrusion. The floating die changes the relative movement between the die and the metal blank, the beneficial friction between the blank metal and the die promotes the tooth filling, the hollow diversion reduces the forming pressure and the tonnage requirements of the forming equipment.
Xia Shisheng, Wang Guangchun, etc. adopted the two-step forming process of pre forging split zone and split final forging. During pre forging, the split zone was preformed at the upper and lower end faces of the hollow blank. During final forging, the metal flow state at the end face of the blank was changed, the blank fluidity was improved, and the gears with full top teeth on the upper and lower ends were obtained. The forming load was nearly 30% lower than that of the traditional closed upsetting extrusion straight tooth cylindrical gears.
Zhang Qingping, Zhao Guoqun, etc. proposed a closed die forging inward shunting method for two-step forming of solid spur gear. Closed die forging extrudes the upper and lower end faces of the blank to form a spherical shunting cavity, but the tooth shape is not completely filled. The final forging inward shunting fills the tooth shape, and the excess metal shunts into the spherical shunting cavity, which is not fully filled, so the forging load is reduced.
Zhang Yuhua and others deeply studied and analyzed the forming process and forming mechanism of gear parts. On the basis of closed upsetting extrusion and split forging, a new two-step forming process of spur internal gear by secondary split precision forging, namely shrinkage extrusion upsetting extrusion composite forming process, was proposed. A set of special die for floating mandrel is designed to realize this process.
Via MSC The simulation is carried out by SuPerform software, the process parameters affecting tooth filling are optimized, and the best combination of process parameters is obtained. The feasibility of the process and the accuracy of the finite element model are verified by physical simulation.
In the first mock exam, Fang Chuen and Xin Xuanrong et al. Have developed a new two way cold upsetting extrusion process with floating die and diffusing forging technology. Firstly, the annular blank is pre forged and upsetted by the floating die with movable mandrel, and then the flow chamber of the movable mandrel is removed for split flow final forging. In the two-step forming process, there is no need to replace the die, which shortens the process flow and improves the processing efficiency.
Wang gangchao, Xu Feng and others improved the axial shunting process with floating die, and analyzed the influence of shunting cavity with different shape, size and position on tooth filling through numerical simulation. When the circular shunting cavity is set in the center of the blank and the metal flows violently, a large amount of metal flows into the shunting cavity at the end of forming, but the upper and middle tooth tops of the tooth profile are still not filled. When the rectangular shunting cavity is set at the tooth shape position where the upper end face of the die is the most difficult to fill, and the tooth shape is basically filled at the end of the forming, a small amount of metal flows into the rectangular shunting cavity. Compared with the traditional axial shunting process, it not only significantly improves the filling of tooth cavity, but also greatly alleviates the sharp increase of forming load.
Song Yuquan, Jing Yuanyuan, Wang Minghui, etc. designed a new type of hydraulic press equipment with up and down double action, and developed a compound forming process of upsetting, extrusion and bulging of spur gear. Select the straight tooth cylindrical gear with module M = 4 and tooth number Z = 20 to establish the finite element model for simulation analysis. It is proved that the process can theoretically make the metal blank completely fill the tooth cavity of the female die, maintain the extrusion force until the end of forming, solve the defect of microcrack at the tooth root, and prolong the service life of the die. The experimental material of gear blank was prepared by layered plastic clay method, and the upsetting extrusion bulging composite forming process of spur gear was physically simulated.
Hu Chengliang, Liu Quankun and others boldly put forward the theoretical hypothesis of rigid translational flow mode by analyzing the metal flow law in the forging process of spur gear, which was verified by finite element simulation and physical simulation. The pre forging tooth profile is designed by using the rigid translational flow mode theory, and then the split flow forging is introduced to put forward the rigid translational final forging process. The optimized design of asymmetric die can change the stress state of blank metal, make the metal flow filling of upper and lower end faces tend to be uniform, and the forming load is up to 42% lower than that of traditional closed forging process.
Wang Shi, Zhang Ruhua, etc. studied and analyzed the metal flow law of closed die forging and split extrusion, and put forward the two-step forming process of “closed die forging pre forming + Split extrusion final forming” of spur gear. The splitting extrusion die was designed, and the physical simulation experiment was carried out with industrial pure lead. The spur gear formed by the new process has the advantages of full tooth shape filling, small forming load, easy demoulding, and simple equipment action.
Zheng Li and others studied the “half ridge – half groove” forming process of spur gear, refined the process flow, and designed a complete set of molds and positioning tooling required for forming. This process opens up a new way of cold extrusion forming of spur gears, and has great advantages over other forming methods, such as small forming load, high material utilization rate, no demoulding problem, simple equipment and die structure requirements and so on.