The molten metal was not directly poured into the mold cavity due to the possible corrosion of the mold in Dongguan CNC plant. The molten metal is poured into a gate cup with storage function and smoothly enters into the sprue. The gate cup also has the ability to prevent the slag from entering the mold cavity through the skimmer or skimming core shown in Figure 5.27. It retains the sand and sludge floating in the upper layer and only allows the clean metal below to enter the sprue. The sprue cup can be separated directly from the end cap section, or a separate dry sand sprue cup can be prepared for use as shown in Figure 5.27.

In the pouring operation of Dongguan CNC plant, the molten metal should be filled with the gate cup, otherwise it is easy to form a funnel through which the atmospheric gas and dregs will enter the mold cavity.
One of the walls of the sprue cup is tilted 45 degrees to the horizontal. Liquid metal is dumped on this plane to eliminate the heat Metal momentum and avoid the formation of eddy current. In Dongguan CNC processing plant, in some special cases, the gate cup can form a part that allows slag cutting and maintains a constant metal height in the cup. The sprue is a channel through which liquid metal is introduced into the parting surface. Through the parting surface, liquid metal enters into the runner and gate, and finally into the cavity. The liquid metal obtains a velocity from the top to the parting surface. As a result, when an equal amount of metal flows at the top, a smaller cross section is required. If the sprue is made as shown in Figure 5.28

(a) As shown in the straight cylinder, the metal flow will not be filled at the bottom, but will form a low pressure zone around the liquid metal in the sprue. Due to the permeability of the sand mold, atmospheric gas will be sucked into the low pressure zone and then into the cavity. To eliminate the problem of gas suction, the sprue is tapered to gradually reduce the cross-sectional area of metal flowing from the top to the bottom as shown in Figure 5.28 (b). Dongguan CNC processing plant is really good, worthy of attention!!