The design of inner gate has a very important impact on the casting quality, because the flow direction and speed of liquid metal and the flow state of liquid metal will be affected by the inner gate. The size, shape and position of the inner gate will affect it. It can be seen from scheme 1 that setting the position of the inner gate at the thick part at the bottom of the box can improve the shrinkage and shrinkage casting defects, but from the simulation results of scheme 1, it can be seen that the position of the maximum shrinkage and shrinkage casting defects is between the two inner gates at the bottom of the box. In order to further improve the maximum shrinkage and shrinkage casting defects, it is decided to change the position of the inner gate, See if the maximum shrinkage can be reduced.
1. Scheme design
As mentioned earlier, the size and shape of the inner gate have been determined, so a different inner gate position has been designed. The new gate position is called new process scheme II, and the three-dimensional diagram is shown in Figure 4.7 to ensure that the setting of process parameters remains unchanged and simulate it. Taking the maximum shrinkage rate and total shrinkage porosity of the die casting produced by the simulation results as the inspection indexes, compared with the simulation results of the front inner gate position, the best inner gate position is selected to obtain better die casting quality.
2. Comparison and analysis of simulation results
The indexes to evaluate the simulation results are to check the filling time, solidification time, maximum shrinkage rate and total shrinkage. Table shows the simulation results of different ingate positions.
| Inner gate position | Filling time (s) | Setting time (s) | Maximum shrinkage porosity | Total shrinkage porosity (CC) |
| Scheme I | 47.28 | 3159.4 | 0.713 | 91.7074 |
| Scheme II | 48.98 | 2964.7 | 0.707 | 88.8710 |
In the above two schemes, only the position of the inner gate is different, and other casting processes are all the same. It can be seen from the figure that the flow pattern of liquid metal in the mold cavity will be affected by the position of the inner gate. The filling time and solidification time of scheme I and scheme II are different. The mold filling time of scheme 2 is increased by 1.7s compared with scheme 2, but the solidification time is reduced by 194.7s compared with scheme 1. From the simulation results of table 4-8, it can be seen that the maximum shrinkage porosity of the scheme two is the lowest, and the total shrinkage porosity is the lowest. The result is better than scheme 1. Therefore, we can know that the inner gate position scheme II is the lost foam casting process. The casting quality of the gearbox box produced is good, and the inner gate position is more reasonable. At the same time, the maximum shrinkage rate of scheme 2 is 0.707, which is 18% lower than the maximum shrinkage rate of the original process, and the total shrinkage amount of scheme 2 is 88.8710cc, which is 33% lower than the original process. Therefore, in conclusion, the most reasonable gating system is scheme 2.