The metal forming process known as investment casting dates back nearly 5,000 years. Other names for this technique include lost wax casting and investment casting. Manufacturers use this technique to precisely cast highly heat-resistant metals using plaster, plastic or ceramic molds and molten wax patterns.
Investment casting is ideal for manufacturing precision parts with unique shapes that require tighter tolerances and a better surface finish.
Advantages of Investment Casting
This method is ideal for making small complex geometries with complex features with one mold.
Investment casting is used in many ways. Because you can combine multiple wax patterns to create a unique mold, you can configure parts that you cannot machine or tool make, making them a valuable alternative to weldments.
Dimensional accuracy and finish are other benefits of this casting method. The casters form the ceramic shell around a uniform pattern, leaving no parting lines because there is only one mold instead of two for casting. The result is a smooth finish averaging around 125 micro-finish, but a finer finish can be achieved with post-process smoothing if necessary.
Other advantages of investment casting include:
Reusable Material: Design engineers can reuse melted wax for another pattern. They can also reuse the molds due to their strength.
Tight Tolerances: Investment casting has a tolerance of 0.003 inches, which is tighter than most casting processes, such as die casting.
Design Capabilities: With investment casting, design engineers can add identifying markings such as numbers, logos, and product IDs to castings.
Disadvantages of Investment Casting
Although lost wax casting has its advantages, it also has disadvantages. The biggest downside is the size limitation. Since few design engineers are able to produce large parts using this technique, it may not be the best option for customers who need to manufacture large assemblies.
This process is best suited for casting small complex parts. Parts over 75 lbs are better suited to other casting methods.
Investment cast enclosures are also limited in size and depth. They cannot be smaller than 1.6 mm or more than 1.5 times the diameter in depth. If your casting design requires a core and cannot meet these requirements, you may need to look to other processes.
This technique is more complex than other casting processes and requires extensive preparation and specialized equipment. Therefore, investment casting can be more expensive upfront than sand or die casting, but unit production costs decrease as orders increase.