Germany, Japan and other developed countries began to study the helical gear forming process very early, and the technology is more advanced. The relevant research in China began in the 1970s. Traditionally, cutting technology is used to process the tooth profile of helical gear, which not only cuts off the continuous fiber structure in the metal, but also affects the structural strength of helical gear; Moreover, single piece processing takes a long time and wastes a lot of raw materials. Later, with the continuous progress of material processing technology, various new processes have been introduced and applied to the processing and production of helical gears.
Kondo K. et al. Used the cold precision forging process to process the helical gear with boss, and obtained the metal flow law in the forming process; Doege e proposed and proved the possibility of forming spur and helical gears by hot die forging on cross opening and closing machines; Cai J applies the cross combination of floating and immovable female dies, inclined and plane male dies to the production of forgings respectively. By observing the metal flow and stress-strain conditions under different combinations of male dies and female dies, it is concluded that when inclined male dies and floating female dies are used, the metal filling die cavity is the best and the forging forming load is the lowest; Duggirala r studied the forging process of spiral bevel gear by using rigid plastic finite element method, analyzed the forming condition of helical gear with the help of I-DEAS software, and guided the structural design optimization of die according to the simulation results; Watanabe et al. Designed the tooth mold according to the meshing characteristics of the driven spiral bevel gear, and successfully trial produced the sample parts; Kong Weiyi discusses the use of continuous casting and continuous forging process to produce helical gear, and introduces the advantages of using this process to process gear blank compared with the traditional process; Using numerical simulation technology, Yang Shenhua verified the possibility of forming the differential bevel gear of a car by cold closed die forging process; Kou Shuqing studied the application of cold closed die forging process to the forming process of spur bevel gear; Wang Huajun et al. Simulated the precision forging process of driven spiral bevel gear, obtained the workpiece with full tooth shape filling, and concluded that the large section bevel gear is not suitable for cold precision forging; Yang dy studied the metal flow law and stress-strain distribution during ring rolling; Tian Fuxiang put forward the compound forming process of hot precision forging and cold extrusion to form spur gear, introduced its advantages and designed the corresponding processing equipment; Xia Juchen and others used the method of combining finite element simulation and process test to apply the cold precision forging process to the helical gear forming process, and studied the influence of die size, gear blank shape and finishing quantity on the forming process; Fang Yuan et al. Studied the influence of helical gears with different structural and technical parameters on the precision forging process of driven helical bevel gear, and concluded that the helical angle and pressure angle have little influence on the forming load of the workpiece, and the forming load and equivalent stress at the tooth root are directly proportional to the module and number of teeth of helical gear; Wang Fengsheng used DEFORM software to study the production of driven spiral bevel gear by hot precision forging and then machining. By analyzing the metal flow field and equivalent stress-strain distribution, he learned that the metal flow at the step of gear boss is difficult. Based on this, he optimized the die structure, and came to the conclusion that the initial forging temperature has little relationship with energy consumption; Yan Hongyan et al. Put forward the problems needing attention in precision control in the processing of helical gears, carried out process experiments on the forming of planetary gears by hot precision forging cold precision forging compound forming process for billets with different diameters and different pier thickness ratio, and determined the reasonable process parameters; Cheng mengbiao analyzed the rotary forging shaping process of driven spiral bevel gear through finite element simulation technology, and determined the best process parameters; Qiu Dehua et al. Applied the gear hollow split flow theory to the forming of spur bevel gear. According to the different cold precision forging quantities of tooth surface and tooth root, two cold precision forging schemes of standard shape tooth profile and non-standard shape tooth profile are designed respectively. It is concluded that the non-standard shape tooth profile is more suitable for the finishing process of spur gear; Zhang Qingping et al. [20] simulated and analyzed the influence of different parameters on the helical gear forging process by using DEFORM software: increasing the die speed is conducive to improving the metal fluidity. Compared with cold precision forging, the workpiece and die stress of warm forging process are greatly reduced, the forming load of materials with low carbon content is smaller, and the service life of forming equipment is higher.