The investment casting process starts by making a pattern that has the sameshape as the finished cast part. A sacrificial pattern is the name used for thepattern because you make the pattern from wax, and it will melt away in theprocess. Specifically, you make the pattern by injecting wax into a metal waxinjection die. You then dip the wax pattern in a ceramic slurry covered withsand stucco, repeating the process several times until you achieve the desiredthickness. The thickness will depend on the specifications of the finishedproduct and what raw materials you will use to make the final product.
TheMold
Once the ceramic slurry has dried, the mold is placed in an oven. Thiswill melt the wax, leaving a one-piece mold that you can fill with your desiredmaterial. These molds are typically made using stereo lithography or othercomputer-aided technology; this makes the mold highly accurate. Examples ofproducts made using investment casting include aircraft parts such as turbineblades, armament parts, hand tools and jewelry.
Waxes
You can use avariety of industrial waxes to make investment casting molds. Your specificneeds for the final product will determine the type of wax that you should use.Filled pattern wax, emulsified pattern wax, straight pattern wax, low expansionwax and automatic injection machine wax are some of the waxes commonly used forthis process. The viscosity, melting point and types of injections used are theprimary considerations that will determine the type of wax you want touse.
Materials
Virtually any type of metal can be cast using investmentcasting, including alloy steel, carbon steel, stainless steel, aluminum, copper,nickel, cast iron, lead, magnesium, tin, titanium and zinc. You can also usemany precious metals. You will generally not need to use any machining for thepieces because of the accuracy of the investment castingprocess.
References
WTEC; Metal Casting Applications;Clinton L. Atwood; March 1997
Investment Casting Wax: Categories ofInvestment Casting Wax
Cypress Industries: The Investment Casting Process