Research On Cold Extrusion Process Technology For Planetary Spur Gear

With the development of automobile industry and the growing demand for car parts, the future trend of automobile fittings production technology development are higher and higher accuracy requirement, more and more low cost, energy saving and so on. As an important part of mechanical transmission, spur gears are widely used in automotive industry. However, complex structure of the cylindrical spur gear leads to the disadvantages that the difficult metal flow, poor filling effect of gear, no easy filling in the cavity corner, big collapse angle on the tooth top, low tooth profile precision, large forming force and low die life and so on. These are more obvious in cold extrusion forming process for big modulus gear, because the modulus is larger, the difficulty of forming is increasing. Therefore, more and more attention has been paid to the research on the forming technology of large module spur gear.This paper took a large modulus planetary gear as an example. A cold extrusion process was put forward to solve the issues that low production efficiency and high production cost in the cutting process of the gear. The gear cold extrusion forming process were analyzed through combining with the finite element analysis, mathematical methods and process test, the main work as follows:(1)The theories and technological schemes used in the cold extrusion forming process were elaborated to make a theoretical preparation for the study of the cold extrusion for the large modulus planetary spur gear;(2)The advantages and disadvantages of the general forming method for spur gear of were compared, and cold extrusion process was selected as the forming method for large modulus planetary spur gear. According to the planetary gear structure to determine forming difficulty part of the tooth shape, cold extrusion process was chosen through comparing the classical gear cold extrusion forming process, and the three-dimensional shape of the die was designed. The ways out of the mold of push-out and get-through were analyzed, and then the way out of the mold get-through was chosen;(3)Cold extrusion process of the gear was simulated and analyzed, and the factors of forming load, lower collapse angle, tooth rebound effect of gear cold extrusion were analyzed by using DEFORM-3D finite element simulation analysis software;(4)The effect of die land length on spur gear in cold extrusion forming process was analyzed, it was found that has influence on the effective length of gear and the shrinkage of the upper gear, and the best die land length was obtained;(5)The optimization goals were to reduce the forming load and the collapse angle axial length and acquire small elastic recovery for gear. The mould angle, blank diameter coefficient, friction coefficient and deformation speed were chosen as the optimization variables. In addition, orthogonal design and Design-Expert 8.0 software were used to multi-objective optimize. The best combination of parameters were obtained by using the Design-Expert 8.0 software.Through the research of this paper, the tooth profile accuracy of the planetary spur gear and the surface quality of the gear have been improved, and the economic benefit has been brought to the enterprise. At present, the cold extrusion process of planetary spur gear has been used in mass production. At the same time, the research results of this paper has provide a reference for the improvement of the accuracy and quality of the other same types of part.