Extrusion processing methods include bar forward extrusion, pipe forward extrusion, reverse extrusion, and unconstrained forward extrusion.
When the bar is being extruded, the metal flows smoothly, and the pressure acting on the mold changes little and is relatively stable. For parts such as extrusion gears, a reduction rate within the range of 20% to 40% is appropriate.
The pipe is extruding. This method is suitable for processing parts with splines on the inner wall and toothed outer circles. The surface friction area and pressure required for extrusion are much larger than when extruding bar stock.
Anti-extrusion. It can be used to extrude products with internal splines or higher tooth heights.
In this processing method, the punch bears all the pressure required for forming, so the elastic limit stress of the punch is the factor that determines the forming limit. Generally, the reduction rate is 30%
The unconstrained form of forward extrusion is carried out in front of the forming part of the die without plastic deformation of the blank, and is suitable for processing spline shafts with shallow grooves. During extrusion, it is necessary to avoid axial distortion and thickening of the hair near the die feed.