Learn About Investment Castings: The Process From the Industry's Best
Dive into precision manufacturing with our RLM Industries FAQ page, centered on the investment casting process—a contemporary practice rooted in the ancient art of lost-wax casting. This time-honored technique has been refined over countless generations as a cornerstone of modern industrial metal forming.
Our investment casting solutions are trusted across various industries, including the aerospace industry, to produce complex metal parts with intricate details and complex geometry. Thanks to the precision casting process, we can achieve tight tolerances and high-quality finishes for even the most demanding applications.
Here, we address your curiosities, offer insights, and illuminate how our mastery of investment castings delivers precise and customized solutions for your complex metal component needs.
Step-by-Step Guide to the Investment Casting Process
The investment casting process is renowned for its ability to produce metal parts with exceptional dimensional accuracy and intricate detail. Here’s a step-by-step look at how this precise manufacturing process unfolds:
- Creating the Wax Pattern: The process begins by injecting wax into a metal die to form a replica of the desired part. These wax patterns are crafted with meticulous attention to detail, ensuring that the final investment cast will meet tight tolerances and complex geometries.
- Assembling the Wax Tree: Multiple wax patterns are attached to a central wax sprue, forming what is known as a “wax tree.” This assembly allows for the simultaneous casting of several components, optimizing efficiency and reducing material waste.
- Building the Ceramic Shell: The wax tree is repeatedly dipped into a ceramic slurry and coated with fine refractory materials. Each layer is allowed to dry before the next is applied, gradually building a robust ceramic shell around the wax patterns. This ceramic shell will ultimately define the smooth surface finish and high dimensional accuracy of the final part.
- Removing the Wax: Once the ceramic shell reaches the desired thickness, the assembly is heated in a kiln. The wax melts and drains away—a process known as “lost wax”—leaving behind a hollow ceramic mold that perfectly mirrors the original wax patterns.
- Pouring the Molten Metal: The preheated ceramic shell is filled with molten metal, such as stainless steel or high-performance alloys. The metal flows into every cavity, capturing the fine details and complex shapes of the mold.
- Cooling and Shell Removal: After the metal solidifies and cools, the ceramic shell is carefully broken away, revealing the newly formed investment cast parts. The components are then cut from the central sprue, cleaned, and finished as needed.
- Final Inspection and Finishing: Each part undergoes rigorous inspection to ensure it meets the required dimensional accuracy and quality standards. Minimal secondary machining is typically required, thanks to the precision of the investment casting process.
By following this step-by-step process, manufacturers can produce precise components with complex geometries, tight tolerances, and minimal material waste—making investment casting a preferred solution for industries demanding high performance and reliability.
Investment Casting FAQs
Investment casting, also known as the lost wax process, is a casting method in which a wax cluster is covered in a ceramic slurry made from a refractory ceramic material. Once hardened, the wax is melted out of the ceramic shell. The shell is heated to 1,800 degrees Fahrenheit, and molten metal is poured in. After cooling, the ceramic is vibrated and blasted off the metal products. The products are then cut, cleaned, and prepared for shipping.
Generally, all ferrous and non-ferrous materials can be investment castings. Material selection is critical in investment casting projects, as choosing the right alloy—such as stainless steel alloys or carbon steel—depends on the required properties like corrosion resistance and wear resistance. Carbon, tool, alloy steel, 300, 400, 15-5ph, and 17-4ph stainless steels are most commonly poured. Advancements in investment casting materials and pattern materials have expanded the range of alloys and applications. Check our Alloy Selection Guide for details.
Investment castings can range from a fraction of an ounce to over 1,000 pounds. Most investment casting foundries only cast parts up to 20lbs. RLM can cast parts up to 250 lbs.
RLM tolerance—first inch plus or minus 0.010 and .005 for every additional inch. Recent advancements in investment casting now enable even tighter tolerances, allowing for more precise and complex parts.
The ceramic shell is built around a smooth wax pattern, and the finish achieved by investment casting is excellent. The use of high-quality refractory materials and refractory ceramic materials in the shell-building process enhances the surface finish and minimizes the machining required after casting. A 125 micro-finish is standard.
Indeed, investment castings are usually more expensive than forged parts or those produced by other casting methods. Investment casting is a cost-effective solution for producing complex parts in large volumes, thanks to an efficient production process that minimizes secondary costs. Investment casting, however, compensates for this added cost by reducing the amount of machining and other secondary costs associated with other processes.
Investment castings are widely used in applications that require parts to be x-rayed and meet specific soundness criteria. Non-destructive testing techniques, such as radiography, ultrasonic testing, and dye penetrant testing, are commonly used to ensure the internal and surface integrity of investment castings. The integrity of investment casting can be significantly superior to that of parts produced by other methods.
Typically, 6 weeks for commercial grade and 8 weeks for ordnance. Deliveries can be negotiated and changed for customers with special requirements.