The following is the answer to how to design the mold gate system in Precision Shaft Die Casting Processing, which is divided into four natural paragraphs:
1. Basis for the layout of the gate position
In Precision Shaft Die Casting Processing, the layout of the gate position is the primary consideration in the design of the gate system. First of all, the design should be based on the structural characteristics of shaft parts. If the shaft parts have special structures such as shoulders and keyways, the gate should be kept as far away from these parts as possible to avoid affecting their accuracy and integrity. For example, for parts with high-precision shoulders, if the gate is close to this place, stress concentration may occur due to the solidification shrinkage of the gate, affecting the flatness and dimensional accuracy of the shoulder. At the same time, the flow balance of the liquid metal in the cavity should be considered. For longer shaft parts, you can choose to set the gate at one or both ends of the shaft, or use a ring gate design to ensure that the liquid metal can evenly fill the entire cavity. This can prevent defects such as pores and shrinkage caused by uneven flow, especially for precision shaft parts with high internal quality requirements. Uniform flow helps to ensure the density of the organization.
2. Adaptability selection of gate type
The selection of gate type is crucial for precision shaft die-casting molds. Pin-point gate is a more commonly used type, which has many advantages. Due to its small gate size, the gate mark left after die-casting is small, which is very beneficial for the situation where the surface quality requirements of precision shaft parts are high. For example, in some shafts that require subsequent electroplating or high-precision assembly, pin-point gate can reduce interference with surface treatment and assembly. However, the processing accuracy requirements of pin-point gate are high, and it is more sensitive to the fluidity of die-casting materials. Another option is the side gate, which has a simple structure, easy processing and low cost. For some shaft die-castings that do not have top-level strict requirements on surface quality, the side gate is a feasible solution. When selecting the side gate, its width and thickness need to be determined according to factors such as the wall thickness and size of the shaft parts to ensure the reasonable inflow of liquid metal.
3. Accurate calculation of gate size
The determination of gate size requires accurate calculation. First of all, the size of shaft parts, including length, diameter and wall thickness, should be considered. For large shaft parts, a larger gate size is required to ensure that enough liquid metal flows into the cavity. When calculating the gate size, it is necessary to base it on the flow characteristics of the die-casting material. Different die-casting alloys (such as aluminum alloys, zinc alloys, etc.) have different fluidity and viscosity. Taking aluminum alloy as an example, its fluidity is good, but the flow resistance in the cavity must still be considered when determining the gate size. If the gate size is too small, the liquid metal will flow too fast, which may cause air entrainment; if the size is too large, the liquid metal flow rate may be too slow, affecting the filling effect, and even causing cold shut defects. At the same time, it is also necessary to combine the die-casting process parameters, such as die-casting pressure and injection speed, and comprehensively calculate through empirical formulas and simulation software to determine the gate diameter (pin point gate) or width and thickness (side gate).
4. Coordination of the gate system with other mold structures
The gate system does not exist in isolation, it needs to work in coordination with other structures of the mold. In terms of coordination with the runner system, the gate should match the size and shape of the runner to ensure smooth flow of liquid metal from the runner to the gate. For example, the roughness and diameter of the runner will affect the flow rate and pressure loss of the liquid metal, and thus affect the filling effect at the gate. In coordination with the exhaust system, the design of the gate should take into account the discharge of gas in the cavity. If the gate position or size is unreasonable, it may hinder the discharge of gas, resulting in defects such as pores. For example, when designing the gate, it should be avoided that the gate is facing the gas gathering area in the cavity, or the flow direction of the liquid metal can be adjusted by optimizing the gate size so that the gas can be discharged smoothly. At the same time, the gate system should also be compatible with the cooling system of the mold, because the solidification speed at the gate will affect the die-casting quality of the entire part. A reasonable cooling system layout can be adjusted according to the position and size of the gate to ensure the uniformity of the quality of shaft parts.
