Cold extrusion forming and compound forming process of spur gear

The cold extrusion forming of spur gear refers to the plastic deformation of the metal blank placed in the die after being compressed and extruded from the tooth concave model cavity, so as to obtain the required tooth parts. The cold extrusion process of spur gear generally includes the following processes: blanking, spheroidizing annealing, blank making, phosphorus saponification, cold extrusion, turning, heat treatment and finish turning.

The cold extrusion process of spur gear is similar, and the design and forming process of spur gear die cavity is the key to forming. In 2004, song and im of Korea Automotive Technology Research Institute established a CAD system for spur gear forward extrusion die manufacturing based on blank size, die strength and cold extrusion load. The system uses empirical formulas to calculate and predict the forming load. In 2005, taking the oil pump spur gear as the research object, Li Mingliang of Henan University of science and technology proposed two forming methods: forward cold extrusion and reducing cold extrusion. By comparing the metal flow law in the forming process of forward cold extrusion and reducing cold extrusion, it was determined that the forward cold extrusion method is more suitable for the precision plastic forming of spur gear. In the same year, Liu Quankun and Meng Guanguan of Hefei University of technology proposed a tooth shaped concave model cavity based on streamline. The cavity is based on flow curve, and the metal flows more evenly during extrusion forming, which can effectively reduce the forming load and improve the filling capacity of tooth top. Narayanasamy R and ponalagusamy r proposed a streamline tooth die based on Bezier curve, which was designed and manufactured by computer-aided. Using the die to preform first and then upsetting extrusion can improve the forming uniformity, reduce the extrusion load and reduce the die wear.

In 2009, Zhang Meng of Shanghai University of engineering and technology applied the finite element method to compare the advantages and disadvantages of radial extrusion, split radial extrusion and forward extrusion, and proposed an improved composite process. The numerical simulation results show that the improved composite process can effectively reduce the forming load and ensure the filling of tooth top. In 2010, Chen Wei of Shanghai University of engineering and technology studied the effects of six process parameters on the forward extrusion forming force and forming accuracy of spur cylindrical gears by the combination of numerical simulation and experimental design, and obtained a group of process parameter combinations through optimization to guide the actual production. In 2012, Wang Shi and Han Xiangyin of Nanchang University proposed the two-step precision forming process of “closed die forging pre forming + splitting extrusion final forming” of spur gear, studied the effects of die forging preform shape and splitting extrusion die geometry on forming force, blank stress and strain and splitting extrusion die stress, and obtained the spur gear with full tooth shape and clear tooth profile through physical experiments. In 2014, through numerical simulation and orthogonal experimental design, Wang Yang of Shandong University analyzed the influence law of the five process parameters of die half angle, sizing belt length, blank diameter coefficient, friction coefficient and extrusion speed on the cold extrusion forming of spur gear. The range analysis results showed that the sizing belt length and extrusion speed had no effect on the quality of formed spur gear, According to the actual production situation, a group of optimal process parameter combinations are selected. In 2015, Zhou Zhiqiang of Chongqing University and others optimized the forward extrusion forming process of the spur gear with large modulus of M = 4 and z = 16, and pointed out that when the die insertion angle of the tooth profile die is 45 °, the tooth profile is full and the forming load is low.

From the research results at this stage, the cold extrusion forming process of large module and large tooth width spur cylindrical gear is still in the research and experiment stage, and it is still difficult to form high-precision spur cylindrical gear by relying on a single cold extrusion process. Through the collection of relevant literature at home and abroad and the actual investigation of some domestic spur gear processing enterprises, the team of senior engineers of ZHY gear believes that the cold extrusion composite forming process is one of the main directions for the development of plastic forming of high-precision and high-quality spur gear, and has the practical significance of promoting to large-scale production.

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