Design criteria for precision casting structures

Precision casting process is different from traditional stamping process. When designing the casting structure, it is necessary to fully consider whether the casting structure meets the requirements of the casting process. The rationality of the casting structure design is related to the casting quality. Good structural design will reduce casting defects such as shrinkage porosity, shrinkage porosity, casting stress, deformation, etc. that occur during casting. Based on casting experience and relevant theories, several main principles of casting structure design can be summarized as follows:

(1) Minimum wall thickness criterion

On the premise that the structural performance meets the requirements, the wall thickness of the casting should be as small as possible, but the wall thickness of the casting cannot be less than its minimum value. If the wall thickness of the casting is thick, bubbling may occur, leading to a decrease in the quality of the casting. If there is a large solid structure, the stiffness of the structure can be strengthened by reasonably arranging reinforcement bars, changing the shape of the structure, and other forms.

(2) Flexibility criterion in the direction of tendon length

Strengthening ribs is a very important structure in castings. It can not only effectively improve the strength and stiffness of the structure, but also avoid the occurrence of thick walled parts, reduce the use of materials, and improve the quality of castings. In order to avoid shrinkage deformation of the reinforcing bars during cooling, methods such as honeycomb reinforcement bars, inclined bending reinforcement bars, misalignment of reinforcement bars, and cutting of reinforcement bars are used.

(3) Guidelines for avoiding local material accumulation

In traditional structural design, increasing wall thickness is often used to improve structural strength and stiffness. However, in the design of castings, it is necessary to avoid the accumulation of local materials. If there is a significant change in the thickness of the connected walls in the structure, due to the different cooling rates of different wall thicknesses, it is easy to generate casting stress during cooling, which can cause deformation and defects in the castings. This not only fails to strengthen the situation, but also becomes a weak link.

(4) Good stress state criteria

For castings, compressive strength is usually higher than tensile strength, so compression is prioritized in casting design. Castings are mostly plate shell structures, and local reinforcement is required at the point of concentrated force to prevent excessive bending loads on the plate shell.

(5) Guidelines for smooth flow

The designed structural components need to ensure that the pouring fluid can pass smoothly and that no voids are generated.

(6) Easy exhaust criteria

(7) Guidelines for easy cutting processing

After the casting product is completed, it is almost a finished product, but it still needs some cutting processing before it can be used. Therefore, when designing the casting, it is necessary to fully consider the subsequent cutting processes of the casting.