Numerical Analysis And Optimization Of Spur Gear Extrusion Forming Process

Gears are widely used parts in the mechanical field, which are used to transfer power, change the speed and direction of movement. Gears have plenty of advantages, such as:larger power range, higher transmission efficiency, more accurate transmission ratio, longer service life, safe and reliable. The gears made by cold extrusion, not only have higher production efficiency, higher material utilization, less subsequent processing operation, but also have uniform metal fiber, less microdefects, more excellent mechanical properties. However, since the cold extrusion forming technology of a spur gear is difficult, especially unsuccessful tooth filling, serious die wear, low production efficiency, it has not been used in practical production.By means of the orthogonal experimental design, total length of gear, shrinkage depth of upper surface, collapse length of under surface, effective length of gear and peak load are chosen as indicators to measure the effect of spur gear during the cold extruding process. Using finite element analysis method, the influence laws of die angle, die bearing length, blank diameter coefficient, friction coefficient, extrusion speed on cold extrusion forming process of spur gear are obtained. Orthogonal experimental results show that die angle and blank diameter coefficient are the greatest effect factors, friction coefficient takes the second place, and die bearing length and extrusion speed have little impact on the forming results. Reducing the die angle is an effective way to increase the effective length of gear. Blank diameter coefficient and friction coefficient have inconsistent influences to all the indexes.In order to reduce the shrinkage depth of upper surface, blank preform design and mold optimization design based on orthogonal experiment were put forward. Numerical analysis results indicate that blank preform designs is difficult to improve the shrinkage phenomenon of the upper surface, but the mold optimization design can reduce the shrinkage depth of the upper surface, which is good for improving the forming effect and raw material utilization of spur gears. Among the optimal design parameters of under shape of the punch, the depth of the concave is the most important factor. The shrinkage depth of upper surface is minimum when the depth of the concave is5mm. The radial dimension of the concave is the second larger influence factor. The shrinkage depth of upper surface is minimum when the radial size of the concave is equal to the root circle diameter. The fillet radius is the minimal impact factor. The shrinkage depth of upper surface is minimum when the fillet radius is2mm.Through numerically analyzing the elastic deformation of the mold at the end of forward extrusion and the elastic recovery of the gear after formed, a precise design method of the mold cavity of cold extruding a spur gear was established. The elastic deformation of the mold at the end of cold extrusion forming of spur gear and the elastic recovery of the gear were obtained using the finite element analysis method. According to the dimension compensation theory, the elastic deformation of the mold and the elastic recovery of the gear were compensated to the mold cavity to realize the precise design of the mold cavity.