Tooling for Investment Casting: What Is The Process and How Does It Work?

Investment casting, also known as lost-wax casting, is a manufacturing process used to create metal parts with fine detail and tight tolerances. Investment casting tooling is used to create the wax or plastic patterns that ultimately determine the shape and dimensions of the finished casting.

The process begins with a tool, typically made from a high-grade aluminum alloy or steel, that serves as the mold for the wax pattern. Hot wax or plastic is injected into the tool and allowed to harden. The pattern is then removed, coated with ceramic and stucco material, and heated until the wax melts away. Molten metal is poured into the resulting ceramic mold to produce the final investment cast component.

Investment casting relies heavily on precise tooling and equipment to ensure that the final metal part meets the specifications.  Tools for investment casting are typically created through a multi-step process that involves several stages of design, fabrication, and testing.  Customers of MetalTek are involved in designing the tooling process to ensure it meets all requirements.

Investment Casting Tooling Design

The first step in the investment casting tooling process is creating the tool design.  This is usually done using computer-aided design (CAD) software, which allows engineers to create a 3D model of the tool.  The tooling design process can be expensive and is often priced into the quote as a separate item.  Ensuring the design is accurate and meets all specifications is critical, as the tool can potentially be reused thousands of times.  MetalTek works closely with every customer throughout this design process.

Creating The Wax Injection Tooling

Once the design is complete, the investment casting tool is fabricated using a variety of techniques, depending on the complexity of the tool and the materials being used.  Some common fabrication techniques include CNC machining, laser cutting, and 3D printing.

Wax injection tooling consists of a metal mold or die designed to produce the wax or plastic pattern used in the investment casting process. The tooling is typically made from aluminum or steel using CNC machining or other precision manufacturing techniques.  The wax injection tool works by injecting liquid wax or plastic into the mold under high pressure.  The wax is then cooled and what remains is an exact copy of the final metal part. The wax or plastic pattern is then removed from the mold and heads to the next steps in the investment casting process.

The designs in the tooling process can be highly intricate.  There can be no cavities, single cavities, or even multiple cavities.  The dimensional tolerances can be extremely tight.  This is an added benefit to this process unlike sand casting with lower dimensional tolerances.

Investment Casting Tool Testing and Production

After the tool has been created, it is tested to ensure that it will perform as expected.  This involves testing for dimensional accuracy, durability, and other factors that could affect the quality of the casting. If issues are identified during testing, the tool is adjusted before any production begins.  The time spent refining and testing can ultimately remove customer cost from the process.  Even small variations in the tool can have a significant impact on the quality of the final casting.  Once testing is complete and the investment casting tooling is approved by the customer, production can begin.

Tooling Design Considerations

When pouring or injecting hot wax into the tool, engineers must consider expected shrinkage.  They must calculate based on the size and metal type, because as the metal cools in the final pour it will shrink. Additionally, the tooling is often designed to be removable or disassembled easily to remove the wax injection safely and accurately.

Tooling is often considered the ownership of the customer after payments are settled, but storage of the tool is important for future uses.  The tooling design is also considered proprietary information as each design is unique.

Investment Casting Tooling Expertise

Overall, the tooling used in investment casting is critical to the success of the process.  It determines the quality and accuracy of the final part, and any defects or imperfections in the tooling can result in sizeable defects in the final part.  On that note, it is important to work with experienced and skilled professionals who have the expertise to design and manufacture high-quality tooling for investment casting.  Contact us to learn more.