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Precision Castings: How does it Work?

Posted on May 31, 2021

Precision Castings

Precision castings are applied to manufacture military parts, medical equipment, and supplies, aerospace components, automotive assemblies, and more. The freedom in material choice and complex design makes such a technique prevail in multiple industries.

Precision casting is a process that manufactures parts with complicated geometries and detailed designs. It is also called lost wax castings because the process involves the use of sacrificial casting wax. Precision castings are beneficial because they can deal with both ferrous and nonferrous materials. So how does a precision casting process work? We will break down the steps for you right now.

How does Precision Casting Work?

A precision casting process includes steps as follows: making a pattern, making a tree, creating a molded shell, removing the wax, melting, and casting. Typically, precision castings are able to create net shape components. However, there are cases where additional finish processes are required.

Making the Patterns

The expendable patterns have the identical geometric shape as the finished part. It is made by injecting wax into a metal injection die. Since extreme temperatures are involved in lost wax casting, thermal contraction is usually taking into consideration in the making of the pattern.

Making the Sprue

Making a tree is the step to assemble the patterns. The pattern as well as other wax components are put together on the tree called a sprue.

Creating a Mold Shell

The sprue will be placed into the ceramic slurry in this step to create a molded shell. After that, the sand stucco is applied onto the sprue and covers the assembly. The mold shell is created after the assembly dries out.

Removing the Wax

This step is called dewaxing. It will take place after the dipping and coating with stucco process is repeated multiple times until the shell is about 5 to 8 mm thick. The assembly is placed in an autoclave and heated until the wax is burnt and lost. This step is important because it not only removes the wax but also strengthens and stabilizes the ceramic shell.

Melting and Casting

In this step, the melted metal material is poured into the finished ceramic shell to cast. Heat is also important in this step because it guarantees the metal fluid spreads evenly in the shell.

Precision casting is also called investment casting or precision investment casting because metal materials are poured into the ceramic shell to form the end products. After the metal cools down and hardens, the shell is broken to retrieve the part. This is called knock-out. Sometimes the near net shape (NNS) parts need an additional finish process to attain precision and dimensional accuracy.

Why is Precision Casting Necessary?

Precision investment casting is necessary because it is able to deal with almost all metal materials. While some metals and alloys are hard to machine, precision casting serves as an effective alternative to creating complex parts with these materials. It is suitable for making internal passages and ports in a valve, curve vanes of an impeller, and internal channels in a turbine blade, etc.

:: Read More: Top 4 Investment Casting Companies

What are the Primary Advantages of Precision Investment Casting?

As mentioned, precision castings are able to process hard-to-machine materials and make net shapes with complicated design. However, there are more advantages this technique offers.

  • It is adaptive to the constant change of product design
  • It is ideal for low-quantity production runs (100-1000 pcs).
  • It is able to create complex geometries that are hard to machine or forge.
  • It offers an excellent surface finish.
  • It offers high dimensional accuracy.
  • It offers freedom in material choice. (It works with both ferrous and non-ferrous metals)

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