Investment Casting Explained
Investment casting is a process that involves molding metals into complex shapes. In the early years, it was used to produce complex net shapes and intricate metal components. Later, it expanded to industrial and commercial applications. For example, in February 2014, Planetary Resources, a company that manufactures aerospace parts, unveiled its titanium integral space bus satellite. The design included integral cable routing and a toroidal propellant tank.
The process is easy and straightforward, and it can produce parts with tight tolerances and high detail. First, a tool die is created for the part that will be melted into the metal. The tool die is then injected with wax, which creates the wax pattern. After the wax pattern has been formed, it is replaced with the melted metals.
Investment casting is done with several different types of metals, including aluminum and copper alloys. The most common types of metals are copper alloys and aluminum. A liquid refractory material is used to coat the mold and fill it with the metal. The resulting product is a complex, durable part. Investment casting can be used for prototypes and production runs of 10,000 or more pieces. The process is most suitable for complex designs with thin walls or thin cores.
A wax pattern can be made with a variety of materials. Commonly used for wax patterns are aluminum split cavity dies. Special dies that have a soluble or ceramic core are also available. The molten metal is then transferred into the mold cavity through a gating system. The heating cycle in an autoclave can be controlled more precisely to minimize stress fracture.
An alternative way to create investment casting patterns is Fused Deposition Modeling (FDM). This additive manufacturing process builds plastic parts layer by layer, using CAD files. It is fast, allowing foundries to produce prototypes in a matter of hours. This technology allows manufacturers to test investment casting components without any delays.
Creating an investment casting mould is a complex process. The temperature and pressure of wax injection play a significant role in the quality of the finished product. Using a vacuum and minimizing humidity during the casting process is recommended to achieve the best result. In addition, improper de-waxing can reduce the batch yield and cause shell cracking, one of the most common defects in investing casting. De-waxing is usually done through a flash fire or autoclave (steam). However, steam autoclaves are preferred because the heating is uniform and the stress is reduced on the material.
Investment casting has a long history in manufacturing. However, recent technological advances have led to the development of specialized varieties for specific applications. While die casting is more cost-effective for large production volumes, investment casting is often more economical for smaller parts or stainless steel components.