With reliable transmission quality and efficiency, gears are widely used in mechanical field, especially in military industry, aerospace and other important fields. The common processing method of gear products is cutting, which is easy to operate, but due to the limitations of processing methods, the gear strength will also be affected. Precision forging technology has little damage to the overall mechanical properties of components, especially for gears. Forging method ensures the structure and mechanical properties of gear teeth, so that the gear teeth strength, meshing stability and other functions are higher than those of gear cutting. In addition, mature precision forging technology can effectively save materials. Aiming at the problem of precision forming of spur gear, the forming methods at home and abroad can be summarized as closed die forging, extrusion forming, spinning forming and two-step splitting extrusion forming.

In this paper, the forming process of spur internal gear tooth cavity is studied. The simulation and experiment show that upsetting and extruding spur internal gear with toothless punch is better than upsetting and extruding spur internal gear with toothed punch in load and die structure.

Through the combination of experiment and numerical simulation, the traditional closed die forging process and the proposed two-way upsetting extrusion precision forming process of spur gear are compared and analyzed. The simulation and experimental results show that the two-way upsetting extrusion process of spur gear is better than the one-way upsetting extrusion process. In the forming process, the tooth cavity can be filled smoothly, the tooth shape is good and the forming process is stable The load value decreases about 57%, which can reduce the die load and improve the die life.