Lost Wax Casting
Lost wax casting is a common metallurgical process which entails the metallic replication of a wax mold t to create various components and parts. During the molding process, the wax mold is melted away, or “lost.” Lost wax casting is not the most economical of processes, but it enables manufacturers to fabricate complex shapes with precision. Furthermore, lost wax casting can be cost efficient for many applications, because of the fact that secondary operations are not necessary.
During the lost wax casting process, a surface is created that takes after the wax mold. As opposed to other molding processes, which involve two halves of a mold, wax forms are one whole piece. As a result, products made with a wax form are seamless and feature no joining lines. Wax Casting yields products that are consistently accurate, due to the wax model being the exact size and shape as the final product.
All of the materials used in the process—whether it is the creation of the mold itself or the materials that go inside it—can be manipulated to achieve desirable characteristics such as weight load and durability. At the same time, the undesirable features can be minimized. The first step is creating the wax pattern, also referred to as the master die. The wax used to make the master die can be carved by machine or by hand. However, in a more automated scenario, injection molding can be used. Before the next step in the process may be taken, the mold must be rid of any imperfections to ensure that it resembles the exact shape of the desired final product. Using a heated metal tool, the die is then attached to a wax rod called a sprue. Sprues form a mount for the pattern, form a channel for both wax elimination and an entryway for molten metal, and they can collect excess molten metal. Sometimes, up to several patterns can be attached to one sprue. This arrangement is known as a tree. The sprue or tree is then dipped a number of times into the investment, or a ceramic slurry. An alternative method involves placing the pattern into a flask, which is then filled with the slurry. Once it reaches a certain thickness, the investment is cooled. Once the investment is in a solid state, it is placed upside down into an oven or furnace, which causes the wax to melt and run out, leaving the mold of the product behind. The metal is then exposed to extremely high temperatures in order to get rid of residue or moisture. The molten metal is poured into the hollow shell and left to cool. Once cooled, the cast is removed and sometimes disposed of, and the product is complete. One thing to keep in mind about the lost wax casting process is that some materials may be more sensitive to certain temperatures, and thus prone to change their dimensions after being exposed to extreme temperatures.
Traditionally, the process of lost wax casting has been used for fabricating jewelry, and has been used by jewelers to create unique signature designs for centuries. In the context of jewelry making, a wax pattern is made into a jewelry mold and filled with molten silver or other types of metal. The filled wax mold is then placed into cold water which disintegrates the mold and solidifies the silver, revealing a completed piece of jewelry. Another application for lost wax casting is the creation of dental impressions. A wax pattern of the missing tooth or rim is created. The wax pattern is sprued, and immersed into the investment. The wax pattern of the tooth is eliminated by either burning it inside a furnace or dissipating it in hot water, and the mold is complete. After the cast is cleaned, the sprue is removed from the cast, and the cast is sent for finishing and polishing. Lost wax casting is highly valued in fabricating dental impressions due to the material’s ability to be cast asymmetrically, inexpensively, and with intricate detail.
Recent advances in science and technology have expanded the applications for which lost wax casting can be used. Today, lost wax casting is used for applications such as propellers, pipes, fittings, couplings, engines, and medical tools. Almost any metal that can be cast can be used in lost wax casting. These metals include brass, titanium, gold, stainless steel, copper, and aluminum. Industries that utilize lost wax casting include sports, military, plumbing, telecommunication, food processing, mining, construction, electrical, medical, dental, automotive, and aerospace.
Lost Wax Casting – MES, Inc.