Gating system design is a core element in die-casting mold design, crucial for determining casting quality. Its rationality directly impacts the molten metal filling speed, pressure transmission, venting, and ultimately the casting’s performance. A well-designed gating system guides the molten metal into the mold cavity smoothly and orderly, minimizing defects such as air entrapment, cold shuts, and shrinkage. It also reduces mold wear and extends mold life. Conversely, improper design can lead to a surge in casting scrap rates and low production efficiency. Therefore, gating system design requires systematic planning, taking into account multiple factors, including casting structure, alloy properties, and die-casting machine parameters.
At the beginning of the design, the structural characteristics of the casting need to be clarified, especially the wall thickness distribution, complexity and key functional areas. For thin-walled complex castings, high-speed filling must be achieved through the pouring system to prevent the molten metal from filling the cavity before solidification; while thick-walled castings need to control the filling speed to prevent excessive pores caused by turbulence. For example, the filling time of thin-walled parts such as mobile phone casings usually needs to be controlled at 0.05-0.1 seconds, while thick-walled parts such as engine blocks can be appropriately extended to 0.1-0.3 seconds. At the same time, the design parameters need to be adjusted according to the type of alloy: aluminum alloys have better fluidity and a relatively simplified pouring system can be used; magnesium alloys are easily oxidized and the exhaust design needs to be strengthened; copper alloys have a high melting point and the gate size needs to be optimized to reduce heat loss.
The design of the gating system must adhere to the principles of “sequential filling, pressure balance, and adequate venting.” Sequential filling involves the gradual filling of the mold cavity with molten metal along a predetermined path, avoiding the confluence of multiple streams of molten metal and the resulting vortices. Pressure balance requires a rational distribution of the cross-sectional area of each section of the gating system to minimize pressure loss during the transfer process. Adequate venting requires the placement of the gate and the arrangement of overflow troughs to guide the smooth discharge of gas from the mold cavity. For example, for box-shaped castings, the ingate can be placed in the middle of one long side, allowing the molten metal to fill symmetrically on both sides. Overflow troughs can be placed on the opposite long side to collect gas and cold material, significantly reducing the porosity defect rate.
Simulation technology is indispensable in modern gating system design. Computational fluid dynamics (CFD) software can simulate the molten metal filling process, visually observing flow velocity distribution, pressure changes, and gas accumulation areas, thereby optimizing parameters such as gate location and runner dimensions. When designing a gating system for a transmission case, an automotive parts manufacturer initially encountered insufficient gates, resulting in insufficient far-end filling. After simulation analysis, adding two auxiliary gates increased the casting qualification rate from 72% to 94%. Furthermore, mold trials are required to verify the design results, and the gating system is further adjusted based on casting defects (such as cold shuts and shrinkage) observed in pilot production, forming a closed-loop process of “design – simulation – mold trials – optimization.”
With the advancement of die-casting technology, gating system design is moving towards intelligent and personalized design. For multi-cavity molds, a balanced gating system is required to ensure consistent filling conditions across all cavities. For large, integrated die-cast structural components (such as new energy vehicle chassis), a complex system with multiple gates for coordinated filling, combined with localized pressurization technology to minimize shrinkage, is required. Furthermore, environmental protection requirements are driving the gating system toward a “short process, low consumption” approach. By optimizing runner length and cross-sectional area, metal waste is reduced, lowering subsequent cleanup costs. For example, one company employed a biomimetic tree-like runner design, which reduced metal consumption by 15% compared to traditional designs while improving filling efficiency by 20%.
