Spur gear is the key component of high-end equipment. The design and manufacture of high life, high performance, high efficiency and low cost has become the main way to improve the competitiveness of products. Conventional cutting or the combination of hot forging and cutting can not meet the development requirements. The extensive hot die forging process has significant problems such as high energy consumption and many processing procedures. The cutting manufacturing method has the disadvantages of destroying the continuity of gear fiber, easily leading to surface stress concentration and reducing fatigue life. The precision forging technology of spur gear can improve the above problems. The precision forging process maintains the integrity and continuity of metal streamline, obtains better material structure and performance, reduces the weight of parts, and improves the safety, reliability and service life of parts. The research shows that compared with cutting spur gears, the strength and bending fatigue life of precision forged spur gears are increased by 20%, the deformation of heat treatment is reduced by 30%, and the service life is increased by 20%. Especially in mass production, precision forging has greater benefits and competitiveness.
Precision forging technology refers to the technology that only a small amount of processing or no processing can meet the requirements of parts after forging. Moreover, the production of products close to the final shape as much as possible, or even the complete provision of finished parts, is the inevitable trend and development direction of plastic processing technology reform [6]. At present, the precision forging of bevel gear has carried out mass industrial production, while the metal flow direction of spur gear, especially large module spur gear, is perpendicular to its stress direction during precision forging, and there is no draft angle during forming, resulting in difficult tooth forming, large forming force and serious die wear. At present, there are many researches on the precision forging of spur gears with small modulus (m < 2mm), and there are few researches on the precision forming of large modulus (M > 3mm). There are still many problems to be solved. The development of spur gear precision forming process has become one of the hot topics in the field of plastic forming.