Bescast Answers: What Is Investment Casting?

Do you need intricately designed parts with thin walls? Does your application demand precise casting with extremely tight tolerances? It can be hard to get components like these manufactured. But the investment casting process can be the answer for many challenging applications. 

This article will answer the question, "What is the investment casting process?" We'll also delve into the different types of investment casting products and the advantages of this advanced manufacturing process.

What Is the Investment Casting Process?

The investment casting process, also known as lost-wax casting, uses wax patterns and ceramic shells to create near-net shape parts. It's a multi-step procedure that starts with an investment casting die and ends with components that have superior finishes and tight tolerances. The investment casting process steps include:

1. Produce an Investment Casting Die

A metal investment casting die is created based on a master pattern that matches the end product, taking shrinking into account.

2. Create Wax Patterns

Wax is injected into the investment casting die to create replicas of the end product. Cores can be incorporated to manufacture highly complex parts.

3. Assemble Wax Patterns

The wax patterns are attached to a sprue to create a tree. This tree is a gated system that will allow the molten metal to flow freely into every portion of the cast component. If the final product is small, a tree can accommodate numerous wax patterns. For the very largest parts, there may be just one pattern per tree.

4. Create Ceramic Shells

The wax trees are dipped repeatedly into a ceramic slurry to build up a shell. Granular refractory stuccos can also be used. Each layer is allowed to harden before a new layer is created. The size and shape of the end product, along with the temperature of the molten metal, determines the thickness of the ceramic shells. In the end, the dried ceramic shells will be sufficiently hard to contain the molten metal.

5. Remove the Wax

The ceramic shells are treated to melt and remove the wax. The hollowed-out shells contain a cavity that matches the shape of the desired component. 

6. Pour the Metal

The ceramic shells are heated to an appropriate temperature, usually around 1,000°F to 2,000°F. At this temperature, the shells are further strengthened, residual wax melts away and any moisture in the shells dissipates. Once the shells reach the target temperature, they're filled with molten metal. The temperature of the metal is usually significantly higher than the mold, ensuring it flows into all areas before solidifying.

7. Cool the Ceramic Shells

Once filled, the ceramic shells are set to cool, allowing the metal to solidify. The cooling rate can be controlled by the thickness of the ceramic shell and the ambient temperature around it. This solidification process can take a few minutes to a few hours.

8. Remove the Ceramic Coating

Once the metal has solidified, the ceramic shells are removed through a knockout operation. The sprues and gates that allowed the metal to flow into the shells are also removed.

9. Finish the Parts

The metal castings go through a finishing process. This can include sandblasting to remove any remaining ceramic material, heat treatment to alter the properties of the metal or minor machining to achieve the final dimensions.

10. Inspect the Parts

The last step is inspecting the final products to ensure they meet all specifications. This may involve visual inspection, dimensional checks or more advanced methods, like non-destructive testing.

What is Investment Casting

Advantages of the Investment Casting Process

The investment casting process, often called "precision casting," delivers numerous advantages. It is a highly versatile process that allows for a significant degree of design freedom, allowing manufacturers to create intricate, detailed components that may be difficult or impossible to produce through other casting methods. Its exceptional accuracy and repeatability often eliminate the need for secondary machining, reducing overall production costs.

Additionally, investment casting is known for its excellent surface finish, often providing a smooth, polished result without the need for additional finishing or polishing. It also offers other advantages, such as:

  • No flash or parting lines
  • The efficient use of materials
  • Reduced environmental hazards

Materials Used in the Investment Casting Process

The investment casting process lends itself to a wide range of materials. Common investment casting materials include:

  • Steel
  • Cobalt alloys
  • Nickel alloys
What is Investment Casting

Not sure what metal is best? Our capabilities include material selection assistance.

Applications for the Investment Casting Process

Because of its many advantages, the investment casting process is well-suited to a broad array of applications in fields like aerospace, aviation, industrial gas turbine and gas compression. Typical investment casting products include:

  • Structural castings
  • Open and closed-face impellers
  • Turbine blades and vanes

Frequently Asked Questions about the Investment Casting Process

As a leading expert in the field, Bescast has the answers you're looking for about the investment casting process. Read on for the information you need, and feel free to contact us for additional details.

What Size of Investment Casting Products Are Possible?

Investment casting products can be as small as a few ounces are as large as 800 pounds or more.

Why Is It Called "Investment" Casting?

"Investment" refers to the ceramic slurry that "invests" or covers the wax pattern, creating the ceramic mold.

What Are the Disadvantages of the Investment Casting Process?

The main drawbacks of the investment casting process include the relatively high cost for small production runs and a longer production cycle due to the multiple steps involved in the process.

What Types of Investment Casting Does Bescast Provide?

We specialize in air, vacuum and dual-chamber vacuum investment casting.

Does the Investment Casting Process Lend Itself to Recycling?

Recycling is an essential component of the investment casting process since the investment casting wax can be reclaimed and reused.

Trust Your Investment Casting
Needs to Bescast

Now that we've answered the question, "What is investment casting?" you're ready for the next step. Leading manufacturers rely on Bescast for their investment casting needs. They appreciate our responsiveness and all the customer advantages we provide. Contact us today to benefit from everything we offer.