As a critical component of motors, the uniformity of wall thickness in the motor aluminum alloy end cover during die casting directly affects the product's mechanical properties, sealing performance, and yield. Uneven wall thickness easily leads to defects such as localized shrinkage cavities, porosity, and coarse grains, thereby reducing the strength and durability of the motor aluminum alloy end cover and even causing motor malfunctions. Therefore, comprehensive control from multiple dimensions, including mold design, process parameters, gating system, cooling control, structural optimization, and inspection feedback, is necessary to achieve uniform wall thickness.
Mold design is fundamental to controlling wall thickness uniformity. The parting line selection should adhere to the principles of simplifying the mold structure and avoiding critical functional surfaces. Complex contours can be handled through multi-directional parting or sliding block structures, but a balance must be struck between mold cost and production efficiency. The wall thickness transition zone should employ a gradual slope design, with the slope controlled within a reasonable range to avoid stress concentration and surface defects. The draft angle needs to be dynamically adjusted according to surface roughness and depth; a smaller draft angle is typically set for outer surfaces, while a larger angle is appropriately increased for deep cavities or textured surfaces to ensure smooth demolding and a clean surface finish.
Precise control of process parameters is crucial. Injection speed needs to be adjusted in stages. Initially, low-speed filling is used to reduce air entrapment. Once the molten metal covers the cavity, high-speed filling is switched to ensure sufficient filling of thick-walled areas. Injection specific pressure needs to be adjusted according to wall thickness. Increase the specific pressure appropriately in thick-walled areas to enhance shrinkage compensation, while avoiding excessive pressure in thin-walled areas to prevent flash. Mold temperature needs to be uniformly distributed. Local cooling is used to reduce solidification rate in thick-walled areas, while heating or heat preservation measures are used to delay solidification in thin-walled areas, achieving simultaneous solidification and reducing the risk of shrinkage porosity.
Optimization of the gating system directly affects the flow state of the molten metal. The layout of ingates needs to be symmetrical, and the number and location need to be adjusted according to wall thickness differences. Increase the number of ingates in thick-walled areas to enhance filling, while reducing the number of ingates in thin-walled areas to avoid localized overheating. The gate location should be close to thick-walled areas to utilize the gravity of the molten metal to promote filling, while avoiding direct impact on the core or thin-walled structure. Overflow channels and venting channels need to be rationally designed. The capacity of the overflow channel should match the volume of the casting, and the width and depth of the venting channel must meet the gas discharge requirements to prevent porosity caused by gas stagnation.
Targeted design of the cooling system is key to controlling wall thickness uniformity. Thick-walled areas require dense cooling water channels, using direct cooling water circulation or spot cooling needles to enhance cooling, shorten solidification time, and reduce shrinkage porosity. Thin-walled areas require reduced cooling intensity, extending solidification time through insulation jackets or delayed cooling methods to avoid insufficient filling due to excessively rapid cooling. The cooling water channel layout must match the wall thickness distribution to ensure balanced cooling efficiency in each area and prevent deformation or stress concentration due to localized cooling differences.
Structural optimization can indirectly improve wall thickness uniformity. The thickness of the reinforcing ribs should be controlled within a reasonable proportion of the main wall thickness, and the height should not exceed a multiple of the wall thickness. The layout should adopt a radial or grid-like distribution with appropriate spacing to enhance the overall rigidity and deformation resistance of the motor aluminum alloy end cover. The design of rounded corners must adhere to the principle of relating internal corner radius to wall thickness, while the external corner radius must be controlled within a reasonable range to avoid cracks caused by excessively small corner radius or porosity and shrinkage cavities caused by excessively large corner radius.
Detection and feedback are crucial components of closed-loop control. X-ray inspection can detect internal shrinkage cavities and porosity, a coordinate measuring machine can assess wall thickness deviations, and mold flow analysis software can simulate the molten metal filling process and predict potential defect areas. Through feedback from inspection data, mold design can be optimized, process parameters adjusted, forming a continuous improvement cycle, ultimately achieving precise control of the uniformity of the motor aluminum alloy end cover wall thickness.
