The Brilliance of Lost Wax Casting
Investment casting really is a brilliant process. The history of the practice dates back many centuries, and it has continued to perform well as a casting method ever since. There are many reasons why investment casting has persevered for such a long time, but the principal reason is this: investment casting works. The process has come to be known by several names besides investment casting, but the most meaningful and widely-used alternative name is probably lost wax casting. “Lost wax casting” is the most descriptive name in terms of how the casting process works, and it gives hints as to why investment casting works.
The lost wax casting process begins with an engineer and design tools. Today, that process can involve computer-aided design technology and other advanced design tools, but historically it was a much more analogue process. What both design methods have in common is the fact that they produce wax models, which in the business are called “patterns,” that embody the first phase in the investment casting process. Those wax patterns are then coated in a ceramic/sand slurry, the composition and configuration of which can vary from process to process. This coating process can be repeated many times, and in some cases it can take several days to repeat the coating and drying process (though recent advances in casting technology have sped this process considerably in some operations). When the coating is finished, the ceramic shell is heated, which causes the wax to melt and be lost – hence “lost wax casting.”
The last phase of the process is the most simple; molten metal is simply poured into the ceramic shell, and as it travels into the shell it takes its shape. Once the process is finished and the metal has hardened, the shell is removed, leaving a newly-cast metal product.