The size of the inner shunt gap is determined by the distance between the lower end face of the punch core and the upper end face of the die core. Therefore, as long as the relative position of the punch core is changed, the size of the shunt gap can be adjusted. After studying the influence of the position of the inner shunting surface on the filling of the spur gear tooth profile, it is determined that the position of the inner shunting surface should be far away from the tooth profile of the spur gear die. What is studied is the influence of the size of the inner shunting gap on the metal forming force of the spur gear. Combined with the conclusion, the position of the inner shunting surface is determined at the top, and the shunting gap starts with 4mm and gradually increases in 1mm, Under the condition of ensuring full filling of tooth profile, change the size of shunt gap, conduct numerical simulation, analyze the simulation results, and obtain the trend curve of spur gear forming force with shunt gap, as shown in the figure.
It can be seen from the curve of the relationship between the size of internal split clearance and forming force of spur gear that the size of internal split clearance directly affects the size of forming force. In the process of filling the tooth cavity of the female die with metal materials, when the internal shunt gap is too large, too much metal materials will flow out from the shunt gap. Therefore, more blank volume is required to fill the tooth cavity of the spur gear female die. The selection of shunting clearance is too small. During the forming process of spur gear teeth, the excess metal material cannot flow out of the shunting clearance in time. Only by relying on greater forming force energy, the metal material is forced to flow to the shunting clearance, and a thinner flash is formed at the clearance, which increases the forming resistance, resulting in a sharp increase in the forming force at the end of forming. It can be seen from the curve of 3.15 that when the value of shunt gap is between 4-8mm, the forming force decreases with the increase of shunt gap. When the shunt gap is between 8-18mm, the forming force tends to be stable. When the shunt gap is greater than 18mm, the forming force decreases greatly, but at this time, more blank volume is required to fill the tooth cavity of spur gear die, resulting in unnecessary waste of materials. Therefore, from the perspective of metal forming force of spur gear, it is the best when the shunting gap is between 8-18mm. However, when the shunting gap is between 8-18mm, the flash formed is thicker and the material waste is large, so the inner shunting gap is set as 5mm.