The velocity field of the forging process of straight bevel gear directly reflects the metal flow law in the deformation process, as shown in the figure below, the velocity field distribution of straight bevel gear blank under different reduction. At the initial stage of deformation, the upper surface of the straight bevel gear blank is in contact with the upper punch, and the lower surface of the straight bevel gear blank is in contact with the lower punch. The lower punch is stationary. Under the downward movement of the upper punch, the metal mainly moves downward, and the blank is mainly deformed by upsetting; With the increase of reduction, the workpiece height becomes smaller and the radial dimension increases. The outer surface of the lower part of the straight bevel gear workpiece begins to contact with the tooth root of the small end tooth die, and the contact parts continue to increase, and the metal flow direction also continues to shift laterally; When the reduction reaches a certain size, the tooth top of the small end tooth die is completely in contact with the workpiece of the straight bevel gear, less and less metal keeps flowing downward, and the metal begins to flow to the tooth top of the large end tooth die, and the metal flow is mainly to fill the tooth cavity.

According to the metal flow law, the forming process can be divided into three stages:

The first stage: from the beginning of deformation to the beginning of contact between the tooth root of the small end die and the outer surface of the straight bevel gear, the metal flow is mainly formed by upsetting;

The second stage: from the contact between the tooth root of the small end tooth die and the surface of the straight bevel gear to the complete contact between the tooth top of the small end tooth die and the surface of the workpiece, the metal begins to fill the tooth shape cavity;

The third stage: until the tooth top of the big end gear die is fully filled and the punching thickness meets the design requirements.