**4.3 Simplified gating system**

In the countergravity technique, the gating system is considerably simplified as is depicted in figure 9. It consists merely of branches of flow channels emanating from the central sprue. This simplicity is possible because the interior of the mould is actually an extension of the vacuum system. The high pressure differential between the mould interior and the atmospheric pressure ensures that the molten metal will completely permeate every cavity in the mould. Complex in-gates, depending on gravity flow of melt are thus not needed. This considerably simplifies the mould design.
