Precision Investment Casting
Also referred to as wax casting or investment casting, precision investment casting is a reliable and precise metal casting process that creates complex metal components from a wax pattern (also known as a master die). Components of a wide range of shapes, sizes, and weights can be made from precision investment casting. Precision investment casting includes stainless steel casting, carbon steel casting, rapid prototype casting, aluminum casting, brass and bronze casting, specialty alloy casting, and off-shore investment casting.
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Advantages of Precision Investment Casting
Precision investment casting is advantageous to other methods. Precision investment casting can create parts with closer tolerances and a more sleek surface finish than sand casting. This removes the necessity for machining and additional processes and offers detailed capabilities such as the creation of logos and lettering. As opposed to machining, precision investment casting can produce parts over long production runs at a much lower cost per piece and with much less material waste. Investment casting has a much greater amount of precision and accuracy than the metal fabrication process. It is also much less labor intensive, significantly less costly, and allows for a wider variety of metals that can be used. Finally, the metal fabrication process may require more than one piece to be used to construct a part, while precision investment casting allows for the part to be made with only one piece. As opposed to die casting, precision investment casting is more inexpensive, has shorter lead times, produces components much closer to the net shape, and allows for greater flexibility with alloys. This includes ferrous materials that cannot be made with die casting. Finally, investment casting is favored over forging due to its ability to produce parts with cored geometries, which the forging process is incapable of doing.
Investment Casting Process
In order to produce precise components, the investment casting process follows a series of complex steps. The first step involves the creation of a wax pattern or a master die. The master die is a replica of the desired part. Sometimes, the master die can even be the part prototype, which is either hand carved or made by machine or by injection molding. Before moving on to the next step, all flaws and imperfections must be removed from the master die in order to make sure it exactly resembles the part to be produced. Using a heated metal tool, the master die is mounted on a wax rod called a sprue. In some cases, one sprue can hold several patterns at once. This cluster is also known as a tree. Once the dies are in place on the sprue, they are repeatedly dipped into the ceramic slurry or the investment. The investment must evenly coat the entire mold, and it is dipped until it achieves the desired thickness. Alternatively, instead of dipping, the sprue can be affixed to a flask, and the investment can be poured around it.
After the mold is immersed in the investment, it is then dried in a furnace or oven. The heat melts the initial wax form and causes it to run out, leaving the desired mold behind. Residue and excess moisture is removed through additional heating. The heating process has the additional benefit of preheating the mold, allowing it to be more evenly coated by incoming molten metal. Once the molten metal is poured into the mold, cooled, and solidified, the investment mold is removed to reveal the precise and seamless final product. This can be done by way of either hammers, dissolving agents, or media blasting vibrations.
Applications of Precision Investment Casting
The investment casting process can enable manufacturers to produce accurate dimensional precision parts. Because of this, investment casting is utilized across a variety of industries, such as automotive, dental, medical, aerospace, and jewelry. The fabrication of precision components through the investment casting process can be accomplished easily, with little to no variation between the molded parts. Common Components that can be made through investment casting include braces, medical equipment, automotive engine parts, and high-precision engineering and mechanical parts. Some applications require these components to be cast from specialized alloys that would otherwise require additional processes to complete, such as removing joining lines or joining more than one part together. Precision investment casting is more costly than other casting methods, but it allows for more flexibility in design, detail, and metal choices. Furthermore, precision investment casting eliminates the need for additional steps such as welding or finishing, which minimizes the procedure’s overall initial cost.