The most effective way to solve the internal shrinkage casting defects of nodular iron castings is to use chill and riser. The combination of the two cannot solve the problem. We must solve the problem from other angles. There is a large hot spot, so it is impossible to rely on self feeding. It is still necessary to increase the feeding effect to solve this problem. We consider setting the riser directly above the hot pitch circle, using the wall thickness of the clay core to form the length of the riser neck and shorten the feeding channel (15mm), which can make the feeding channel of the riser smoother and give full play to the feeding role of the riser. So adjust the use position of the 80/110 heating riser, from the original inlay in the side ear core to the inlay in the upper and lower main cores, so that it is directly above the hot pitch circle, and change the riser neck from rectangular (45 × 25) adjust to round（ υ 35), the circular shape is less likely to solidify prematurely than the rectangular shape (as shown in the figure).
After the improvement, the nodular iron castings were cast, and the internal casting defects of the castings were checked and confirmed again according to the evaluation and anatomy scheme of nodular iron castings. The internal casting defects of nodular iron castings were completely solved, meeting the quality standard requirements of more than grade 2 internal casting defects of user products, and realizing product delivery.
For the same casting and the same type of heating riser, only by adjusting the setting position of the riser, the internal shrinkage casting defects of the product are perfectly solved, the use of chill is reduced, and the manufacturing process is simplified. The practice proves that the top feeding effect of solving the internal defects of nodular iron castings is better than the side feeding effect. The successful realization of this process technology has helped the new product development to complete the project set goals on schedule, shortened the development cycle, and established a platform for this kind of products to solve internal casting defects. Generally, there are many feeding processes with side risers in the process design of nodular iron castings, because the feeding process with side risers is relatively simple and easy to make, but it is very feasible and effective to use top feeding for the internal casting defects of nodular iron castings with high compactness, high requirements and difficult to solve.