How to Achieve Good Surface Finish in Sand Casting?

Introduction to Sand Casting

Sand casting is a casting method that produces castings in sand molds. Steel, iron, and most non-ferrous alloys can be obtained through sand casting. The sand casting process allows us to produce parts with excellent surface finish, making it suitable for a range of industrial applications from automotive parts to aircraft turbine blades. The material used to make the sand mold is called molding material, and the material used to make the sand core for the mold is called core sand.

Sodium silicate sand casting is a specific type of sand casting process that can be introduced in this article. In this method, the sand used for making the mold is mixed with a sodium silicate sand binder, which is then hardened with carbon dioxide. Sodium silicate sand casting can produce high-quality castings with good dimensional accuracy and surface finish, making it well-suited for industrial applications such as engine blocks, pump housings, and valve bodies. The molding material used in sodium silicate sand casting is made of sand mixed with sodium silicate, and the core sand is also made using the same binder.

Key factors for Achieving Good Surface Finish in Sand Casting

Pattern integrity

The quality of the pattern used in sand casting is just as crucial as in steel silica sol casting, and professional pattern-makers create patterns using customer-provided designs, 3D models, or software drawings. The patterns used in steel silica sol casting are typically made of high-quality wax or plastic to ensure accuracy and consistency.

Sand selection

The type of sand is also important in sand casting. Just like vacuum die casting, any fault in sand casting can result in rough castings. Because sand particle size and shape affect surface finish, this type of sand should be carefully chosen. Finer particles achieve the better surface finish. This sand is mixed with cold-curing binders (to bond the sand particles together) and catalysts. This helps to form a strong, durable sand mold, which in turn helps to create excellent surface textures on the casting.

Effective ramming

Ramming is the process of compacting sand into the mold. This process is manually performed by our skilled casting team. The mold must be properly rammed to ensure that all voids are filled so that sand does not fall off during the casting process.

High-integrity sand cores

The choice of the core manufacturing process is another important consideration. As we discussed earlier, sand cores are added to the mold to create cavities and complex features. In the foundry, sand casting uses three main techniques: shell core manufacturing, cold box process, and manual ramming technique. Shell core manufacturing produces the best surface finish, but it is also the most expensive technique. It is used when high precision is a priority, such as for critical safety components in aircraft turbine blades.

Machining and finishing

Of course, we can use a variety of machining and finishing techniques to improve the surface finish of sand castings. These include turning, surface grinding and shot blasting. In fact, our castings are all shot blasted for this purpose, and usually, after heat treatment to improve the surface finish.

Metal Casting
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