Brass Investment Casting Process from jaiachuancasting's blog

Brass Investment Casting Process

Almost any castable metal can be investment cast. The brass investment casting process is suitable for parts ranging from a few grams to several hundred pounds; however, most parts weigh 15 pounds or less. The first step in investment casting is to create a master mold from wax. This wax pattern can be engraved by hand or machine, and can also be produced by injection molding. A mold is an exact replica of the part to be produced. It is attached to a wax stick called a gate. Hundreds of wax molds can be attached to the same runner, or it can be a single mold. When the master mold is firmly attached, the assembly is turned upside down and dipped into a ceramic slurry called an investment mold. Multiple dips are possible to obtain a uniform coating and desired thickness.

Another method is to mount the assembly in a flask and pour the embedding material. Then let the investment dry, which takes a few hours unless the process is assisted by a fan or vacuum. Once completely dry, the components are turned upside down and baked in an oven or furnace to melt or evaporate the wax. The mold is heated more than necessary to ensure there is no moisture or residual wax inside that would interfere with the liquid brass, then poured into the space left by the wax. To completely fill the mold, the molten metal can be drawn in by vacuum, positive air pressure or centrifugal casting methods. Sometimes gravity is enough. The brass cools, and once hardened to a solid, the investment is removed to release the brass casting inside.