There is no doubt that metal casting is one of the oldest and yet most fundamental industrial processes known to man. Historically, casting was used to create jewelry and weapons, but it is now a method of rapidly creating complex shapes through the pouring of liquid metal inside of molds. In modern times, a process known as investment casting has been developed for creating highly intricate parts, specifically using standard procedures. As the name implies, investment casting involves the use of wax, slurry, and molds to produce low-tolerance, high-resolution components without having to worry about the hassles associated with traditional casting processes. In this article, we will go over the process of investment casting, how it works, the advantages, and the applications of this technique so that designers can potentially incorporate it into their own works.
What is investment casting, and how does it work?
The investment casting process uses four main steps to produce highly complex parts (for more information about casting, read our article on types of casting processes).
The first step involves creating the wax pattern that will eventually be the final shape of the part(s). However, wax patterns can only be used once each time a part is made because they can be easily melted and reused. Casting Parts Manufacturer must have some sort of master mold in order to create wax patterns due to this limitation. It can be difficult to perfect these if low tolerances are required, and they can be expensive because they must be tailored to every part. A wax bar (known as a “runner”) can be connected between many of these molds, allowing one pour to cast many parts. Finally, a ceramic pouring cup (known as a “sprue”) is added to the top of the wax pattern, so manufacturers have a funnel to pour molten metal into the final mold.
This finalized wax pattern, complete with runners and sprues, is then dipped in a ceramic refractory slurry as the second step of the investment casting process. It is composed of extremely fine silica, water, and other binders. When dipped, the part is covered in a thin layer of slurry, which acts as a mold of the wax pattern. A certain coating thickness (often 5-10mm) is achieved through dipping and drying several times over. In order to create a hollow ceramic mold, Investment Casting Service Supplier turn the dry part upside down and heat it to remove excess moisture and melt away the wax on the inside.
The third step will take place right after the second, where manufacturers will pour molten metal into the ceramic mold while it is still hot from the drying/melting process, right after the second step. This pre-heating from the previous step prevents the molten metal from damaging the ceramic mold, as well as improving the flow of the metal into fine corners/detail areas by preventing the metal from damaging the mold. Aside from that, as the ceramic mold and the metal cool off, both will shrink, improving the dimensional accuracy of the original wax pattern as a whole. As soon as the metal is cast, manufacturers wait for it to cool completely before using it.
In investment casting, the fourth and final step is to remove the ceramic mold from the casting process once it has fully solidified. This is usually done with a water jet or a similar method that allows the ceramic layer to be removed without damaging the underlying metal in any way. It is at this point that the finished parts are ready for cutting from their runners and cleaning to achieve their desired end product finish.