The safety height of riser feeding is taken as the evaluation index in the orthogonal test. The measurement method of safe height is to cut the model longitudinally along the center of shrinkage cavity area after solidification, and detect the vertical distance between the lowest point of riser shrinkage porosity area and the highest point of casting, which is the safe height value.

Figure 1 shows the riser feeding situation under different combinations of orthogonal tests.

The safe height of riser in 9 groups of tests was calculated and the test results were listed. The safety height of riser No.4 is the highest, which is 10.52cm. The feeding liquid is sufficient and the feeding effect is better. The safety height of riser No.3 is the lowest, which is 6.42cm, and the feeding effect is the worst.

In range analysis, the influence of each factor on the test index (riser safe height) is sorted according to the magnitude of the range difference. The larger the range value is, the greater the influence of this factor level on the test index (riser safe height) is the greatest when the level of this factor changes. According to table 3-6, the range of factor A (pouring temperature) is 2.79, that of factor B (negative pressure) is 0.71, and that of factor C (pattern density) is 1.18. The order of range value from large to small is 2.79 > 1.18 > 0.71, that is, the influence of various factors on riser feeding is: pouring temperature > pattern density > negative pressure degree.