The gating system is composed of a gate cup, a runner, a sprue and an inner gate. It is a channel in the mold to introduce liquid metal into the mold cavity (Fig. ). The role of the gate cup is to carry the molten metal poured into the ladle to avoid splashing; the role of the runner is to connect the sprue cup and the sprue to quickly introduce the molten metal into the mold; the function of the sprue is to connect the sprue and the inner gate of each cavity to distribute the metal flow direction; the function of the inner gate is to connect the runner with the part cavity and pour molten metal into the mold cavity.
Whether the design of gating system is correct or not has a great influence on the quality of castings. Some data show that more than 30% of the waste products of castings are caused directly or indirectly by improper design of gating system. A good gating system should meet the following requirements:
(1) The location, direction and number of runner determined should conform to the solidification principle or feeding method of casting.
(2) Fill the cavity within the specified pouring time and ensure that all cavities are filled at the same time.
(3) Necessary filling pressure head shall be provided to ensure clear casting contour and fillet.
(4) The liquid metal flow is stable and serious turbulence is avoided. Prevent excessive oxidation of metals by entrainment of gases.
(5) It has good slag resistance.
(6) When the liquid metal enters the cavity, the linear velocity should not be too high to avoid splashing and scouring the mold wall or sand core.
(7) The liquid metal in the mold has enough rising speed to avoid sand inclusion, wrinkle skin, cold shut and other defects.
(8) The function of cold iron and core seat is not damaged.
(9) The metal consumption of gating system is small and easy to clean.
(10) The modeling is simple and reduces the modeling complexity.