Introduction to the process flow of silica sol casting

Silica sol precision casting is a high-precision and high-quality casting process widely used in aerospace, automotive, medical equipment, energy and other fields. This article will provide a detailed analysis of the entire process of silica sol precision casting, including process flow, design, mold making, wax mold making, shell making, air drying, casting, cutting, surface treatment, mirror finish, wire drawing, powder coating, and machining.

1. Overview of Process Flow

The process flow of silica sol precision casting mainly includes the following steps:

Design and Mold Manufacturing

Wax pattern production

Shell Making

Air drying and dewaxing

casting

Cutting and Cleaning

Surface Treatment

machining

Each step has a crucial impact on the quality of the final product, which we will explain in detail below.

2. Design and mold making

Design is the first step in precision casting, usually using CAD software for 3D modeling. When designing, it is necessary to consider the functional requirements, material properties, feasibility of casting processes, and subsequent processing requirements of the product. After the design is completed, a mold needs to be made.

Mold making usually uses aluminum alloy or steel materials, and high-precision molds are manufactured through CNC machining or electrical discharge machining (EDM). The quality of the mold directly affects the accuracy of the wax mold, so the production of the mold must be very precise.

3. Wax mold production

Wax mold is a crucial step in precision casting. The production of wax molds usually uses injection molding technology, where melted wax is injected into the mold, cooled, and the wax mold is removed. The surface of the wax mold must be smooth and the dimensions precise to ensure the quality of the final casting.

After the completion of wax mold production, multiple wax molds are usually assembled into wax trees to improve production efficiency. The assembly of wax trees requires precise control of the position and angle of each wax mold to ensure smooth subsequent shell making and casting.

4. Shell making

Shell making is one of the core processes of silica sol precision casting. The shell making process mainly includes the following steps:

Dip coating of silica sol: Dip the wax mold into the silica sol to ensure that the surface of the wax mold is uniformly covered with a layer of silica sol.

Sanding: Sprinkle fine sand on the silica sol before it dries to increase the strength of the shell.

Drying: Place the wax mold coated with silica sol and sand into a drying chamber for air drying. The drying time usually ranges from a few hours to a day.

Repeated immersion coating and sanding: Depending on the complexity and requirements of the casting, it is usually necessary to repeat immersion coating and sanding multiple times to increase the thickness and strength of the shell layer.

After the shell is completed, the shell must have sufficient strength and high temperature resistance to withstand the subsequent dewaxing and casting processes.

5. Air drying and dewaxing

After the shell making is completed, the wax mold needs to undergo dewaxing treatment. Dewaxing is usually carried out by steam dewaxing or high-temperature dewaxing methods. Steam dewaxing is the process of placing wax molds into a steam chamber, melting and discharging the wax using high-temperature steam. High temperature dewaxing is the process of placing wax molds into a high-temperature furnace and directly heating them to melt the wax.

After dewaxing, a cavity is formed inside the shell, which is the shape of the final casting. The dewaxing process must be carefully controlled to avoid shell cracking or deformation.

6. Casting

After dewaxing is completed, the shell needs to be preheated before casting. Casting materials are usually stainless steel, high-temperature alloys, titanium alloys, etc. During casting, the melted metal is poured into the shell to fill the entire cavity.

The casting process requires strict control of temperature, pouring speed, and cooling speed to ensure that the internal structure of the casting is dense and free of defects such as porosity and shrinkage.

7. Cutting and Cleaning

After casting is completed, the casting needs to be cut and cleaned. Firstly, cut the casting from the wax tree, and then use a grinding wheel or cutting machine to remove excess material. Next, sandblasting or acid washing treatment is carried out to remove the surface oxide scale and residual shell material.

8. Surface treatment

Surface treatment is the final process of precision casting, mainly including the following methods:

Mirror treatment: By polishing or electrolytic polishing, the surface of the casting is made to achieve a mirror effect. Mirror processing is commonly used for parts that require high precision and smoothness, such as medical devices, optical components, etc.

Wire drawing treatment: By mechanical or chemical wire drawing, a uniform texture is formed on the surface of the casting. Wire drawing processing is commonly used for decorative parts, such as watch cases, phone cases, etc.

Powder coating treatment: By electrostatic spraying or powder spraying, a uniform coating is formed on the surface of the casting. Powder coating treatment can improve the corrosion resistance, wear resistance, and aesthetics of castings.

9. Machining

For some high-precision parts, machining is still required after casting is completed. Machining usually includes processes such as turning, milling, drilling, and grinding to ensure that the dimensional and shape accuracy of the parts meet the design requirements.

High precision CNC machines are required during the machining process, and appropriate cutting tools and machining parameters should be selected based on the material characteristics of the parts.

10. Quality control

Quality control is crucial throughout the entire precision casting process. Each stage requires strict testing and control to ensure the quality of the final product. Common detection methods include:

Dimensional inspection: Use a coordinate measuring machine (CMM) or optical measuring instrument to check the dimensional accuracy of the parts.

Surface quality inspection: Use a surface roughness meter or microscope to check the surface smoothness of the parts.

Internal quality inspection: using X-ray or ultrasonic testing to detect internal defects of parts, such as porosity, shrinkage, etc.

11. Summary

Silica sol precision casting is a complex and precise manufacturing process that involves multiple steps and procedures. Each stage needs to be strictly controlled to ensure the quality of the final product. Through reasonable design, precise mold making, high-quality wax mold making, stable shell making process, strict casting control, and fine surface treatment and machining, high-precision and high-quality precision castings can be produced.

As the owner of a silica sol precision casting enterprise, mastering these process flows and technical points not only helps improve product quality, but also enhances the company's market competitiveness. I hope this article can provide valuable reference and guidance for your business.