Die casting casting slope
The casting angle of a die-cast part refers to the angle of inclination between the wall of the die-cast part and the wall of the mold cavity. Its primary function is to ensure smooth removal of the die-cast part from the mold, avoiding scratches, deformation, and even cracking during demolding. In die-casting production, casting angle is a crucial structural design parameter that directly impacts the demolding efficiency and surface quality of the die-cast part. Different die-casting structures, materials, and mold types have different casting angle requirements. Properly designed casting angle can reduce mold wear, extend mold life, and improve production efficiency and quality consistency of die-cast parts.
The casting slope is determined based on a combination of factors, including the die-casting’s height, surface roughness, and material properties. Generally speaking, the taller the die-casting, the greater the required casting slope. This is because taller walls create a larger contact area with the mold cavity during demolding, resulting in greater friction. A larger slope effectively reduces demolding resistance. For example, for die-castings under 50mm in height, the casting slope can be controlled at 0.5°-1°; for those between 50-100mm in height, the slope can be increased to 1°-2°; and for those over 100mm in height, the slope must be 2°-3° or even greater. Furthermore, the inner surfaces of die-castings (such as those in holes and slots) typically require a greater casting slope than the outer surfaces. This is because the inner surfaces experience stronger wrapping forces during demolding, requiring a larger slope to offset these forces.
Material properties also significantly influence the choice of casting slope. Different die-casting alloys have different elastic moduli and yield strengths, resulting in varying degrees of elastic deformation during demolding, and therefore different casting slope requirements. Zinc alloys have a lower elastic modulus and weaker elastic recovery after demolding, requiring a relatively small casting slope. Aluminum alloys have a higher elastic modulus and significant elastic recovery, requiring a larger slope to avoid extrusion deformation during demolding. Copper alloys have higher strength and hardness, resulting in greater friction with the mold cavity, and therefore typically require a larger casting slope than zinc and aluminum alloys. For example, the outer surface slope of a zinc alloy die-casting can be 0.5°-1°, while the outer surface slope of a copper alloy die-casting must reach 1°-2°.
The surface quality of the mold cavity and the die-casting process parameters also affect the design of the casting slope. The smoother the mold cavity surface, the lower the friction coefficient, and the required casting slope can be appropriately reduced; conversely, if the cavity surface is rough, the casting slope needs to be increased to reduce demolding resistance. Parameters such as mold temperature and injection speed in the die-casting process will also indirectly affect the choice of slope. Excessively high mold temperature will lead to increased adhesion between the die-casting part and the cavity, in which case the casting slope needs to be increased; excessively fast injection speeds may cause the die-casting part to fit more tightly with the cavity, similarly requiring an appropriate increase in the slope to ensure smooth demolding. Therefore, when designing the casting slope, it is necessary to flexibly adjust it in combination with the mold processing quality and actual production process parameters.
The design of the casting slope must also take into account the die-casting’s assembly performance and appearance requirements. Excessive casting slope may reduce the die-casting’s dimensional accuracy, affecting assembly with other components. This is especially true in areas requiring precise fit. The casting slope must be minimized while ensuring smooth demolding. For example, excessive slope at the interface between the engine block and cylinder head can lead to poor sealing. Therefore, the slope must be precisely calculated to ensure that it does not affect demolding while meeting assembly accuracy requirements. For exterior parts, excessive slope can affect the product’s aesthetics. In this case, optimizing the mold polishing process and improving the cavity surface quality can reduce the slope while ensuring smooth demolding. In short, the design of the casting slope requires striking a balance between demolding performance, assembly accuracy, and appearance quality. The most reasonable slope value must be determined by comprehensively considering various factors.
