In the 1950s, gears were mainly obtained by cutting, and the output was very low. At that time, German Burwell light metal company tried to use the method of closed die forging to process gears, and applied for the patent of this technology. In 1984, Kondo K, a Japanese researcher, proposed the precision forging of spur gear by split flow method. Using this method, the forming force can be significantly reduced and the die chamber can be filled well. Then, the scope of application of this method was discussed and the split flow technology of gear precision forging was improved. Tuncer C and Dean TA of the University of Birmingham in the UK have developed a variety of gear precision forging dies with floating die to process the hollow blank, discussed the die structure, and pointed out the key points of the process when using the closed die forging precision forging gear. This method reduces the energy consumption, improves the utilization rate of materials and reduces the subsequent processing. Dreun v m and Dean t a designed a set of parametric software for designing the precision forging die of spur or helical cylindrical gear.
Since 1991, Lin Zhiping has put forward various process schemes for precision forging of spur gears on the basis of cold and hot precision forging process tests through self-made dies, and designed a special combined die for precision forging of spur gears to ensure that the tooth die is filled through floating female die and ring flash groove of upper die. Tian Fuxiang invented the forming process of combining hot precision forging and cold extrusion of spur gear. Firstly, the blank is formed by hot precision forging, and then the tooth surface is extruded and finished at room temperature. This process does not need as high forming force as cold forging, but the tooth surface can achieve high shape and dimensional accuracy after finishing at room temperature, Spur gears can be directly used as finished parts after forming without machining.