According to the analysis of the simulation results of the original process scheme, the bottom pouring system of the original process did not achieve the expected effect. The shrinkage cavity at the thick part of the bottom of the box sand mold casting was large, and the shrinkage cavity in the upper half of the box sand mold casting was more. Setting the inner gate around the bottom did not play a good role in feeding. Moreover, this subject studies the box sand casting and its structure is complex. Through the analysis of the structural characteristics of the box sand casting itself, it can be known that the size of the box sand casting is large and the height is greater than 400mm. Therefore, the new gating system adopts a stepped gating system, which introduces liquid metal into the casting in two layers, which is compared with the upper inner sprue, More liquid metal is introduced into the bottom sprue, and both the bottom sprue and the upper sprue will play a certain role in feeding. Because the material of the sand casting of the gearbox box is gray cast iron, there is no need to design the riser and use the gating system for feeding.
The gate position of the new gating system is determined according to the analysis of the original process simulation results. From the analysis of the original process simulation results, it can be seen that the inner gate position of the bottom injection gating system is distributed around the bottom of the box sand casting and is not set at the thick part of the bottom, so it has no feeding effect on the shrinkage cavity at the thick part of the bottom, In addition, the bottom casting gating system is not conducive to the control of shrinkage and shrinkage defects in the upper part of the box sand casting, so the position of the inner gate of the newly designed stepped gating system is preliminarily set at the thick part at the bottom of the box sand casting and the upper half of the box sand casting, and two are set at the bottom, and one inner gate is set on both sides of the upper half of the box sand casting.