The open gating system is adopted, and the proportion is as follows:

Within Σ A: ∑A transverse: ∑A straight = 1.2:1.1:1

The design of ingate is the same as that of scheme I, and the sectional area of ingate is 22.5 cm2.

According to the cross-section proportion of open gating system, the cross-section of main runner is s = 1.1 △ 1.2 × 22.5 = 20.6 cm2, and the cross-sectional area is 21 cm2. The cross-sectional shape and geometric dimension of the runner are shown in Fig. 1.

Cylindrical sprue is used as sprue. According to the proportion of gating system, the following formula is adopted:

The calculated diameter is d = 2 × 1.89 = 49 mm. The section shape and geometric dimension of the sprue are shown in Fig. 2.

To sum up, the 3D diagram of open gating system is shown in Fig. 3.

As shown in Figure 3, the total number of internal runner, main runner and sprue in scheme II is 1, 1 and 1 respectively.