Finishing, shaping, and re pressing processes in powder metallurgy gear production and processing

In order to improve the accuracy and strength (density) of powder metallurgy gear parts, the gear sintered parts are subjected to a second press after sintering. This process method can be divided into finishing, shaping, and re pressing.

The function of powder metallurgy gear finishing is to obtain the required dimensional tolerance and surface roughness for the sintered gear parts; The function of shaping is to obtain a specific surface shape and appropriately improve local density of sintered parts; The main function of re pressing is to increase the overall density of sintered parts to meet the strength requirements of the parts.

At room temperature, in order to obtain the required dimensional accuracy and surface roughness of powder metallurgy mechanical parts, the sintered parts are re pressed to produce plastic deformation on the surface of the sintered parts, in order to correct their size and deformation, which is called finishing.

During the sintering process of powder metallurgy gear blanks, due to shrinkage (or expansion) and deformation, the dimensional tolerance and surface roughness of the gears cannot meet the requirements of the parts. The use of finishing technology can improve the dimensional accuracy and surface roughness of the sintered parts. During the finishing process, a small amount of plastic deformation (accompanied by elastic deformation) is generated on the surface layer of the gears, which corrects most of the gear deformation. For too large chamfers, grooves Marking and other methods can also be addressed through refinement.

After sintering, the powder metallurgy gear is re pressed to change its shape and improve its accuracy, with a density increase of 5% -12%. When shaping, the gear is placed into the female mold hole and pressurized through the upper and lower stamping dies. This method is suitable for gears with high strength, high density, and difficulty in forming in one go, such as bevel gears, end face spiral gears, etc., and requires high local density.

A special full finishing method for powder metallurgy gears, which has no finishing allowance for both the inner and outer diameters, and leaves mold clearance, but has a large reduction rate (12% -20%) in the height direction. The main purpose is to improve the physical and mechanical properties of the gears (density can be increased by 5% -20%).