Investment casting (lost-wax process) yields a finely detailed and accurate product, with excellent metallurgical properties. Polystyrene foam is also used in investment casting.

After a variable lead time, usually a few weeks, 1–1000 pieces / hour-mould can be produced in the mass range of 2.3–2.7 kg. It is possible to take up items up to 45 kg and as light as 30 gms for unit production.

The process starts by creating an injection die to the desired specifications. This die will be used to inject wax to create the patterns needed for investment casting. The patterns are attached to a central wax sprue, creating an assembly, or mould. The sprue contains the fill cup where the molten metal will be poured into the assembly.

The wax assembly is now dipped multiple times in ceramic slurry, depending on the shell thickness desired. A layer of fine sand (usually zircon) is added on top of each ceramic layer. This process will be repeated until the desired shell is created.

After the shell is created to the specifications desired, the wax must be removed; this is normally achieved using an autoclave. This is where the name "lost-wax process" comes from. This leaves an impression of the desired castings, which will be filled with metal. Before being cast, however, the shells must be heated in a furnace so they do not break during the casting process.

Next, the desired metal is poured into the hot ceramic shell. The metal fills each part on the assembly, and the central sprue cavity and fill cup. The individual parts will be removed after the mould cools and the shell is removed. The shell is generally removed with water-blasting, although alternate methods can be used. What remains are the cast metal parts, but still attached to the sprue assembly. The individual parts are removed by cold-break (dipping in liquid nitrogen and breaking the parts off with hammer and chisel) or with large cutoff saws.

Most investment castings need some degree of post casting machining to remove the sprue and runners, and improve surface finish. Grinding operations are performed to remove the gate. Parts are also inspected to make sure they were cast properly, and if not are either fixed or scrapped. Depending on the investment casting facility and specifications, more finishing work can be done on-site, sub-contracted, or not done at all.

Investment casting yields exceedingly fine quality products made of all types of metals. It has special applications in fabricating very high-temperature metals such as alloy steels or stainless steels, especially those which cannot be cast in metal or plaster moulds and those which are difficult to machine or work.

Investment casting is often used in the aerospace and power generation industries to produce single crystal turbine blade, which exhibit superior creep resistance to equiaxed castings. A combination of slow cooling rates, seed crystals, and an elaborate sprue and runner system referred to as a "pigtail" are used to produce single crystal castings.

Nonexpendable mould casting differs from expendable processes in that the mould need not be reformed after each production cycle. This technique includes at least four different methods: permanent, die, centrifugal, and continuous casting.