At Impro Aerospace, we offer precision investment casting services for mission-critical applications for the aerospace, energy, and medical sectors. We work closely with clients worldwide to provide highly accurate and complex products that are tailored to meet the demands of each specific project. Provided here is an overview of this versatile casting process and the advantages it offers for your component needs.
What Is Investment Casting?
Investment casting is a metal forming technique that derives its name from the step of the process wherein a wax pattern is invested, or surrounded, with a heat-resistant material. Materials that are suitable for investment casting include stainless steel, aluminum, superalloys, low alloy steel, and titanium. The process can be used for castings of various sizes, from a few ounces to several hundred pounds.
Investment casting first involves a wax pattern being enclosed in a ceramic shell to create a ceramic mold. Once the shell has hardened, the wax is melted away to reveal the mold. The metal part can then be cast by pouring molten metal into the ceramic mold. Investment casting offers a superior level of design flexibility and dimensional accuracy relative to other casting methods and can be used to produce parts of almost any complexity or size.
About the Investment Casting Process
The investment casting process is performed in a series of steps, which include:
- Wax pattern creation. Wax patterns are made by injecting melted wax into a metal die. Ceramic or water-soluble cores are used to create the internal features of the pattern. Next, wax patterns are mounted to a central gating system comprised of sprue and runners, enabling the formation of a casting cluster pattern. The gating system generates channels that facilitate the flow of molten metal into the mold cavity or cavities.
- Ceramic shell creation. The casting cluster is dipped into a slurry of fine-grain ceramic particles, coated with coarser particles, then dried to form a ceramic shell around the gating system and patterns. This process is repeated until the shell’s ceramic coat is of adequate thickness to withstand the molten metal it will encounter. An oven is then used to melt the wax away from the shell, forming the single-piece ceramic mold that will hold the metal material.
- Pouring. The ceramic mold is preheated to approximately 1,000° C and molten metal is ladled into the gating system. The natural downward force of gravity facilitates the flow of molten metal into the various cavities in the mold. If needed, vacuum or pressure can be applied to accelerate the flow or to force material into very complex cavities.
- Cooling. The mold containing the molten metal is then allowed to cool and the metal solidifies into its final shape. The time required for cooling will depend on the size of the part, the thickness of the mold, and the type of material used.
- Casting removal. After cooling, the casting can be removed by breaking the surrounding mold. Following the mold removal, the gating system is either cut off with a saw or broken off with liquid nitrogen.
- Finishing. If needed, finishing techniques such as grinding and/or sandblasting can be employed to smooth rough areas where the gating was removed. Heat treatment may be applied to harden the final product.
Advantages & Disadvantages of Investment Casting
Understanding the advantages and disadvantages of investment casting will help to decide if this process is the best option for a particular project. Some of the benefits include:
- Great flexibility in material selection.
- Well-suited for producing complex parts that require intricate design features, tight tolerances, and high levels of precision.
- Provides excellent surface finishes, reducing or eliminating the need for secondary machining.
- Economies of scale can be achieved over large production runs or multiple runs.
Despite these advantages, investment casting may not be the most suitable metalworking solution for every project. Here are some potential drawbacks of investment casting:
- A higher cost—particularly when performing short production runs.
- It tends to be labor-intensive and involves multiple operations, resulting in longer production cycles relative to alternative casting methods.
- It is not ideal for casting certain part types, such as cores.
Investment Casting Applications
Aerospace castings require consistent and robust process capabilities that will meet the industry’s stringent quality standards and requirements for tight tolerances. Investment casting is well-suited for producing complex and high-performing parts that meet these criteria. The process is used to create components for:
- Actuation systems
- Brake systems
- Cabin control systems
- Environmental control systems
- Fuel systems
- Hydraulic systems
- Landing control systems
- Seat safety systems
The medical industry also requires absolute precision for parts that will be used in surgical instruments and other critical applications. Investment casting enables components to be made with exceptional levels of consistency and accuracy that meet the medical industry’s strict quality control standards. Some examples of equipment and devices that use components created through investment casting include:
- Diagnosis equipment
- EMS equipment
- Injury-stabilizing technology
- Laboratory instruments
- MRI machines
- Patient-handling equipment
- Surgical instruments
- X-ray equipment
The energy industry also relies on investment casting for the production of robust and reliable components that can withstand intense conditions. Components used for energy applications must be built to endure temperature extremes, high levels of humidity and moisture, and exposure to harsh elements such as dust, oil, mud, and corrosive chemicals.
Investment-cast products are fully capable of meeting these demands. Examples of energy components made using investment casting include:
- Engine emission control products
- Flame and gas detection systems
- Gas turbine fuel nozzle parts
Investment Casting at Impro Aerospace
At Impro Aerospace, our integrated in-house investment casting services are handled from start to finish by our team of highly-skilled engineers and manufacturers. We are equipped to produce casting products in aluminum, superalloy, stainless steel, and low alloy steel, with sizes ranging from a few ounces to 100 pounds. Our use of water-soluble and ceramic cores allows us to create complex and intricate designs according to exact specifications.
Our extensive precision casting experience, multiple certifications, and ability to perform non-destructive testing ensure integrity and quality of our products. We manufacture parts that are used in virtually all major airframes, including Boeing (737, 777, and 787), Airbus (A320, A330, and A350), and business jets such as Gulfstream and Embraer.
To learn more about our investment casting services or other precision machining capabilities, please contact us today.