Manufacturability of die casting structure design
The manufacturability of die-casting structural design refers to whether the die-casting structure meets the characteristics and requirements of die-casting production, and whether it can achieve efficient, low-cost, and high-quality production while ensuring product performance. Good manufacturability can reduce defects in the die-casting process, reduce the difficulty of mold design and manufacturing, and improve production efficiency and product qualification rate. When designing die-casting structural design, it is necessary to fully consider the specificities of the die-casting process, such as the fluidity of the molten metal, the mold forming method, and the ease of demolding, so that the structural design matches the process requirements and achieves the best production results.
Proper wall thickness design is fundamental to ensuring the structural processability of die-cast parts. The wall thickness of die-cast parts should be as uniform as possible to avoid sudden changes in thickness. This unevenness can lead to inconsistent cooling rates during solidification, resulting in internal stress and deformation, and even defects such as shrinkage cavities and porosity. Generally speaking, the ideal wall thickness for die-cast alloys is 1-5mm, with the specific value determined based on the alloy type and casting size. For example, zinc alloys have excellent fluidity, and a minimum wall thickness of 0.5-1mm is acceptable; aluminum alloys typically have a minimum wall thickness of 1-2mm; and copper alloys have poor fluidity, requiring a minimum wall thickness of 2-3mm. Where necessary variations in wall thickness exist, a gradual transition should be employed, with the transition length at least 3-5 times the wall thickness difference to reduce stress concentration and ensure smooth filling of the molten metal.
The overall structure of a casting should be simple and symmetrical, avoiding complex cavities and protrusions to reduce the difficulty of mold manufacturing and the complexity of controlling the die-casting process. Complex structures can cause eddies and air entanglement during the molten metal filling process, increasing the risk of defects. This can also complicate mold cavity machining, increasing mold costs and manufacturing cycle time. For example, castings with deep cavities, narrow gaps, or irregular protrusions not only make it difficult for the molten metal to fully fill, but also cause the mold core to become slender and fragile, shortening the mold life. Therefore, when designing the structure, the shape should be simplified as much as possible, and a symmetrical structure should be adopted to ensure that the molten metal can evenly and smoothly fill the cavity, improving the stability of the die-casting process.
The design of reinforcing ribs is an important means to improve the structural processability of die castings. Reasonable setting of reinforcing ribs can improve the rigidity and strength of castings, reduce wall thickness, and achieve lightweight design. At the same time, it can also improve the fluidity of molten metal and help molten metal fill thin-walled areas. The thickness of the reinforcing rib is usually 0.5-0.7 times the thickness of the adjacent wall, and the height should not exceed 5 times the thickness of the rib root, otherwise it will cause shrinkage holes at the top of the rib. The distribution of reinforcing ribs should be uniform and symmetrical, avoiding crossing or dense arrangement to prevent the formation of molten metal accumulation at the intersection and shrinkage. In addition, the connection between the reinforcing rib and the wall should be designed with a fillet with a radius of 0.2-0.3 times the rib thickness to reduce stress concentration and improve the fatigue strength of the casting.
The draft angle and fillet design of the casting also have a significant impact on processability. A sufficient draft angle ensures smooth removal of the casting from the mold, reducing demolding resistance and surface scratches. The draft angle should be determined based on the height, material, and surface roughness of the casting, and is generally 0.5°-3°. The draft angle of the inner surface should be greater than that of the outer surface to overcome the wrapping force of the inner surface. All corners of the casting should be rounded to avoid sharp corners. Rounded corners can improve the flow of molten metal, reduce eddy currents and air entrainment, and also reduce stress concentration, thereby increasing the strength of the casting. The fillet radius is generally not less than 0.5mm. For areas subject to greater stress, the fillet radius should be appropriately increased.
The design of structures such as holes, grooves, and threads on castings also needs to take manufacturability into consideration. The size of holes and grooves should not be too small, and their positions should be aligned with the die-casting direction as much as possible to simplify the mold structure and facilitate core setting and demolding. For holes with smaller diameters (less than 3mm), consideration should be given to whether they can be achieved through post-processing to avoid damage to the mold due to overly thin cores. If threaded structures are directly formed by die casting, the precision is relatively low and they are generally suitable for connection occasions with less demanding requirements. For high-precision threads, post-die casting processing should be adopted. In addition, sufficient distance should be maintained between holes and grooves, and between holes and grooves and the edge of the casting, generally not less than 1.5 times the hole diameter or groove width, to ensure the strength of the casting and the filling effect of the molten metal. By comprehensively optimizing these detailed structures, the manufacturability of die castings can be significantly improved, laying the foundation for efficient and high-quality production.
