Precision & Investment Casting
Precision casting using the lost wax process
Investment casting, also known as the lost wax process, is a precision casting technique used to produce high-quality metal components with complex geometries. The process begins by creating a wax model-or pattern-replicating the final product in exact size and shape. This wax pattern is then coated with a refractory material to form a mould. Upon heating, the wax melts and drains away, leaving a detailed cavity into which molten metal is poured. Once solidified and cooled, the outer ceramic shell, a refractory mould formed around the wax pattern, is broken away to reveal the final cast part.
Historical development and modern advancements
Investment casting has been used for thousands of years, but modern developments have refined the process considerably. Today, computer-aided design (CAD) tools and 3D printing are employed to produce highly accurate wax patterns. For smaller parts, multiple wax patterns can be assembled into a single unit called a tree, connected by wax gates and sprues. Advanced computer modelling techniques are used to simulate molten metal flow, ensuring that all sections of the mould fill completely during casting.
Ceramic shell building with refractory slurries
The complete wax assembly, or tree, is repeatedly dipped into a series of refractory ceramic slurries, with drying time allowed between coats. The first coat consists of ultra-fine refractory particles, producing a smooth surface finish on the final casting. Subsequent layers use progressively coarser materials to build up a strong ceramic shell. This multilayered shell adheres well to the wax pattern and, once fired, becomes durable enough to withstand the high temperatures of molten metal without shrinking or cracking.
Advantages of investment casting in metal manufacturing
The key advantage of investment casting lies in its dimensional accuracy and ability to replicate intricate details. It is especially effective for parts with undercuts, thin walls or complex geometries that would be difficult or impossible to produce using other casting methods. A wide range of metals-both ferrous and non-ferrous-can be used, including stainless steel, aluminium, titanium, and bronze. While it is generally more expensive than sand or die casting, investment casting often eliminates the need for extensive machining or post-processing, making it ideal for precision-critical components in aerospace, defence, medical and industrial sectors.
Learn more in our blog: Unlocking the Potential of Investment Casting