This paper briefly introduces the characteristics of several forming methods of drivenof vehicle main reducer, and analyzes the forging forming process and die cavity of spiral , which provides a reference for the research of forging forming process of spiral bevel gear.
1. Casting forming
The processing technology of spiral bevel gear for a long time is forging forming method. For the driving and driven spiral bevel gear of automobile, the production technology is the method ofblank first and then machining. In the long-term application, casting has gradually developed into a relatively mature process and become the mainstream process [1-3]. But the disadvantages and shortcomings of this method are also very prominent, low efficiency, serious waste of materials. In the process of cutting, the streamline inside the material is seriously damaged, which greatly affects the ability of bending resistance of the important parts of the gear, the wear resistance and corrosion resistance are also greatly reduced, and then affect its life.
2. Forging method
Forging is a kind of processing method which uses forging machine to exert pressure on the metal blank to produce plastic deformation to obtain forgings with certain mechanical properties, shape and size.  In order to save energy and reduce cost, it is necessary to use forging process to directly produce spiral bevel gear of reducer. Through forging, defects such as loose as cast metal produced in smelting process can be eliminated, microstructure can be optimized, reliability and feasibility of the process must be guaranteed, die life is high enough to recover cost, and stability is a key problem Question: can it be filled, will it be folded, and how is the demoulding performance [3, 4]. It is obviously a luxury to study by physical simulation, which will waste a lot of manpower and material resources, produce a large amount of mold material cost, mold processing cost and research and development time. It is necessary to use the finite element method and numerical simulation to clearly show every detail in the forming process, and to optimize the forming defects more succinctly.
3. Comparison of casting and forging forming methods
3.1 Improvement of microstructure and properties
The feature of forging is that the billet receives three-dimensional compressive stress during the forming process, which makes the grain of the material refined, improves the compactness of the structure and heals many defects. The metal flow lines are all along the outer surface, eliminating the residual stress, and the tooth shape will not deform after heat treatment, so that the performance of the gear is improved. Theoretically, the impact strength of the forged gear is increased by 15%, and the bending fatigue life and strength are increased by more than 20% .
3.2 High precision
Generally, gears do not need machining after forging, or only need a little machining to enter the heat treatment process and start to use. In this way, the production efficiency is improved and the production cost is reduced accordingly. In theory, the production efficiency of gears produced by precision forging can be doubled compared with that of conventional machining. If mass production is carried out, the cost will be reduced by more than 30%, and the utilization rate of materials will be increased by about 40%. From an economic point of view, if more than 2000 parts are produced in one batch, the advantages of precision die forging are very prominent. If the existing forging and heating equipment can meet the process requirements, precision die forging technology can be used for production when more than 500 pieces are produced, and the advantages of precision forging will be better reflected .
3.3 Compared with the convenience of machining, precision forging can reduce the utilization of machine tool and site, and it is found that precision forging gear has less meshing noise
To sum up, compared with traditional machining, precision forging gear can significantly improve product performance and save cost.