Research status of cold extrusion forming accuracy of spur gears

As an important transmission part in automobile and machinery industry, the efficiency of traditional machining can not meet the high-speed growth market demand. More efficient precision cold extrusion is one of the development trends in the future. In recent years, the forming accuracy of cold extrusion gear has attracted extensive attention. How to ensure the forming accuracy without increasing the subsequent tooth profile processing process is not only the main problem faced by the cold extrusion of spur gear, but also the core problem concerned by spur gear manufacturers, Only by producing high-precision spur gears at a lower cost than cutting can we take the lead in the market competition and enhance the core competitiveness of enterprises.

Therefore, some scholars at home and abroad have studied the cold extrusion accuracy of spur gears from many aspects. Wanheim. T et al. Comprehensively considered the elastic deformation and elastic recovery phenomenon in the cold extrusion forming of spur gear, adjusted the die cavity accordingly based on the elastic deformation, obtained the formed parts with higher dimensional accuracy and improved the part quality. The experiment shows that reasonable elastic compensation can improve the forming accuracy of extrusion gear. Professor Feng Zaixin of Zhongbei university put forward the forming process scheme of spur gear after warm extrusion and cold shaping. The cold shaping amount is determined based on the size of spur gear, die material and unit extrusion force.

Zhou Rui, Hefei University of technology, applied the finite element analysis software MSC to predict the accuracy of cold formed spur gears Marc establishes the cold shaping elastic-plastic finite element model, and uses the combination of numerical simulation and physical experiment to study the change of dimension offset of spur cylindrical gear during cold shaping. During cold shaping, the offset in tooth profile direction gradually increases from base circle to tooth top circle, and the offset in tooth direction gradually increases from bottom to top. Zhu Huaishen and others calculated the value range of cold shaping quantity of large module spur cylindrical gear by using generalized Hooke theory, carried out numerical simulation by using DEFORM-3D, obtained the relationship between shaping quantity and tooth surface springback, and optimized the cold shaping quantity of large module spur cylindrical gear. Stone et al. Used the commercial software ABAQUS to establish the elastic-plastic finite element model of cold shaping of thick wall parts, analyzed the influence of shaping amount on surface roughness and size, and considered that the cold shaping process can improve the surface quality of the workpiece without greatly changing the geometry of the workpiece, which is suitable for the shaping of tooth shaped parts. Chang et al. Conducted shaping experiments on a single tooth without error. The experimental results show that the roughness of the tooth surface is improved by 85% through cold shaping, put forward three different tooth profile models, and analyzed the causes of the drum shape of the tooth surface after finishing and the relationship between the tooth profile die and the drum shape of the tooth part.

Taking the structure and heat treatment conditions of spur gear as variables, song et al studied the accuracy of spur gear, and analyzed the influence law of various process parameters on the quality of spur gear. The research results show that the forming accuracy of spur gear is not only related to its own structure and die structure, The rationality of technological process and technological conditions also has an impact on the plastic forming accuracy of spur gears. Behrens. Taking the hot forging gear as the research object, B, a and others proposed using cold shaping and self-designed elastic die to improve the tooth direction accuracy of hot forging gear. The experiment shows that the improvement measures can reduce the total helix deviation of hot forging gear by 30%, but the die device is complex, and the installation and manufacturing are not suitable for large-scale production.

Liu Hua of Xi’an Jiaotong University and others studied the metal flow of spur gear during cold precision forging by combining numerical simulation and process experiment. Based on the numerical simulation results, the node coordinate information was extracted by C + + to establish the formed tooth profile curve, According to the change of tooth profile curve, it is concluded that the elastic deformation of die is the main factor affecting the tooth profile accuracy of spur gear, and the die tooth profile is modified. Finally, the correctness of this conclusion is verified by process test. Referring to the cold forging of spur gear, Lin Xue and others simulated the plastic forming process of spur gear by using the finite element method, and studied the specific elastic deformation of materials. Based on the obtained simulation data, they fitted the elastic deformation curve of die cavity and the elastic recovery curve of spur gear, and modified the die cavity according to the inverse compensation principle, The research results have great reference value for improving the accuracy of spur gears.

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