What are the production methods of casting investment molds?

Investment casting is one of the important technologies in the field of precision casting, especially suitable for manufacturing metal parts with complex geometric shapes, thin-walled or elongated grooves. This process typically involves multiple fine steps to ensure the accuracy and quality of the final casting. The following are several common casting investment casting methods, each with its unique features, suitable for different types of casting needs.

1. Soaking method
The immersion method is an effective process for treating long hole and narrow groove castings. This process is usually implemented during the production of multi-layer shells. Firstly, use wax molds or other combustible models to construct the basic shape, and then coat the outer layer with refractory material to form a shell. After the shell reaches a certain thickness, it is immersed in a specially designed slurry that can penetrate into the long holes or narrow grooves inside the shell, filling all small voids. After the slurry is dried and cured, repeat the coating and drying steps again until the shell reaches the required thickness and strength. This method is particularly suitable for ensuring complete replication of details in complex structures.

2. Projection wax model method
Projection wax casting, also known as precision casting or lost wax casting, is a long-standing technology. It melts wax or plastic materials by heating and injects them into metal molds to form precise wax molds. Afterwards, these wax molds are assembled into a tree like structure, which is coated with fire-resistant coating and sand particles to form a multi-layer shell. After heating, the wax mold melts and flows out, leaving a cavity, which is then injected with molten metal. After cooling, the shell can be smashed to obtain precise metal castings. This method is suitable for mass production and the manufacturing of complex parts, especially for geometric shapes that are difficult to achieve through mechanical processing.

3. Centrifugal casting
Centrifugal casting is a special casting method that uses centrifugal force to fill the mold cavity. It is particularly suitable for manufacturing cylindrical or tubular parts, such as shafts, fittings, etc. In this process, wax or molten molds are first placed in the rotating mold, and then the molten metal is poured under centrifugal force to evenly distribute and adhere to the inner wall of the mold, thereby reducing the generation of pores and shrinkage. This method helps to improve the density and strength of castings, especially suitable for parts with large aspect ratios.

4. Pressure casting
Pressure casting is a method of injecting molten metal into molds at high speed and pressure, suitable for producing small, thin-walled, high-density complex parts, such as automotive parts. Through high pressure, the molten metal can quickly fill all the details of the mold, ensuring that the casting has good dimensional stability and surface smoothness. However, this method requires high durability of the mold and relatively high cost, making it unsuitable for large or thick walled castings.

5. Ceramic core method
For castings that require complex internal structures, such as water and oil channels in the engine block, the ceramic core method is an effective solution. Ceramic cores, as temporary support structures, can be dissolved or broken out after casting, leaving the required internal channels. This technology combines traditional casting with modern materials science and can manufacture highly complex internal structures without the need for subsequent mechanical processing.

In summary, there are various methods for making investment molds for castings, each with its unique application scenarios and advantages. Choosing the most suitable process not only depends on the complexity of the parts, but also needs to consider production costs, material characteristics, production efficiency, and the performance requirements of the final product. With the advancement of technology, such as the application of 3D printing technology in investment casting manufacturing, new possibilities have been provided for the rapid prototyping and small-scale production of complex parts, further expanding the boundaries of precision casting.