The cold extrusion process of spur gear is a net forming or near net forming process. Its production efficiency and material utilization are much higher than the traditional machining methods. In addition, after cold extrusion, the metal fiber structure of the workpiece is continuously distributed along the tooth profile, there are few micro defects, and the mechanical properties of spur gear are high.
1.Cold extrusion process of spur gear
The forming processes of spur gears mainly include the following: forward extrusion, radial extrusion, split radial extrusion, hot forming, cold finishing, closed die forging, etc. The table shows the comparison of forming processes of several spur gears.
It can be seen that forward extrusion not only has good filling effect, but also has relatively high material utilization rate and die life. However, the technology of forward extrusion forming spur gear still faces many problems in the process of practical application, such as the shrinkage of the upper end face and the collapse angle of the lower end face of the spur gear after extrusion forming. At present, it can only be cut through subsequent machining, which wastes materials and increases machining hours.
The cold extrusion forming process of spur gear is usually as follows: rough return – softening treatment – surface purification and lubrication treatment – cold extrusion forming – dressing after extrusion.
2.Forward extrusion process
When spur gear is being extruded, the flow direction of metal is the same as that of punch. The figure is the schematic diagram of the principle of forward extrusion solid workpiece. First put the return material into the four mold cavity, and then squeeze the return material through the punch. Under the pressure of the punch, the metal enters the plastic state and flows out from the small hole at the lower part of the die, and finally make the required straight tooth cylindrical gear.