Failure Analysis And Design Method Research Of Gear Cold Extrusion Die

As the most common transmission component,gears play an irreplaceable role in mechanical transmission.Due to the shortcomings of long processing time,high cutting waste,and high production costs in traditional mechanical processing,it cannot meet the market requirements of large quantities,low energy consumption,and high quality.The cold extrusion processing technology has been widely used in the production and processing of straight cylindrical gears due to its advantages of high processing efficiency,low energy consumption,high material utilization rate,and high strength of extruded parts.However,during the cold extrusion forming process,the extrusion pressure is very high.As the main load-bearing component,the tensile stress on the concave mold can easily lead to cracks,damages,and other forms of failure of the mold.The failure of gear cold extrusion molds limits the promotion and application of cold extrusion technology in gear processing.Therefore,how to avoid mold failure during the extrusion process and extend the service life of the mold is currently the key to researching gear cold extrusion forming technology.This article takes the planetary gear of the wheel reducer of a heavy-duty truck as the research object.The gear is a straight cylindrical gear,and based on its structural characteristics,a forward extrusion forming process plan is adopted.Combining numerical simulation results and theoretical calculation formulas,the structural dimensions of the mold are calculated;By analyzing the failure of the integrated composite die,a structure of transverse splitting of the integrated composite die was proposed,but there was a phenomenon of blank drilling during the extrusion process;In response to this phenomenon and its causes,this article proposes a mold structure that divides the core of the concave mold horizontally and uses nuts for axial pre tightening at the bottom of the concave mold,and determines the range of axial pre tightening force values;By combining numerical simulation and response surface methodology,the structural size parameters of the axial compression split combination concave die were optimized and designed,and the optimal size parameter combination was obtained;Explored the influence of different process parameters on the metal flow law and mold stress distribution law during the cold extrusion forming process of spur cylindrical gears.Based on the research on the design method and numerical simulation results of the split type combination concave die,a cold extrusion process test mold for straight cylindrical gears was designed and manufactured,and the cold extrusion forming process experiment for straight cylindrical gears was conducted.The test results showed that the straight cylindrical gears extruded using the axial pressure split type combination concave die structure did not exhibit drilling phenomenon,and the tooth shape was filled fully;After the number of extrusion times of the mold reached 50000,the mold was in good condition,and the common normal detection length of the extrusion part was within the design requirements.This indicates that the use of axial compression split combination concave mold structure can effectively prevent mold failure.The experimental results verify the feasibility of the axial compression split combination concave die structure and the correctness of numerical simulation.