What is investment casting?
In investment casting, wax or a suitable polymer pattern is applied by dipping into a refractory slurry. Once the refractory coating has hardened, the dipping process is then repeated several times to increase coating thickness and strength. Once the final coating hardens, the wax melts and the molten metal is poured into the cavity formed by the wax mold. Once the metal has solidified within the mold, the metal casting is removed by breaking the refractory mold.

The process can be summarized into the following steps - mastering, mastering, model making, model assembly, refractory mold making, dewaxing, casting and part removal.

Investment casting, known as lost wax casting, is a precision metal casting process because of its ability to produce high-precision and intricate castings compared to similar manufacturing processes such as sand casting.

Typical parts include turbine rotors, gears, electronics housings, valves, jewelry and dental fixtures. In the past, this process has successfully cast parts up to 1.5 m in diameter and weighing up to 1140 kg, although typical parts have an average size of less than 100 mm and a weight of less than 500 g.

Advantages and disadvantages of investment casting
Advantages of investment casting
Parts with extremely complex shapes and complex features can use investment casting as a single piece casting
Features short lengths or shallow depths to cast thin sections down to 0.40 mm (0.015 in) without cold barrier defects
Lost wax casting has excellent dimensional accuracy and can easily achieve tighter 0.075 mm (0.003 in) tolerances.
Compared to similar manufacturing processes, investment casting achieves an excellent surface finish without any post-processing. Typically about 1.3 – 0.4 microns RMS Ra
It offers almost unlimited freedom in investment casting materials, but the most commonly used materials include aluminum alloys, cast iron and non-ferrous alloys. This process is particularly attractive for superalloys.
Drafting on the wall is not required, but if you are using a master mold to make a wax pattern, then surface drafting will help make the pattern easier.
Since there is no dividing line, there won't be any sparkle in the cast. But wax patterns may have parting lines from the master pattern.
Additional machining can be eliminated or reduced, usually an allowance of 0.4 to 1 mm (0.015 to 0.040 in) is sufficient.
Combined with a very smooth as-cast surface, excellent dimensional accuracy can be achieved. These capabilities are particularly attractive when making products from high-melting, difficult-to-machine metals that cannot be cast using plaster or metal mold processes.
The wax used can usually be recycled.
Disadvantages of investment casting
Compared to other metal casting methods such as die casting and sand casting, lost wax casting involves many complex steps, making the process relatively expensive. But for some products, certain steps can be automated. It may be more expensive than die casting or sand casting, but the unit cost will decrease as production increases.
The expensive molds to make the models have traditionally limited investment casting to high-volume production
The high cost is also due to professional equipment requirements, expensive refractory materials, and high labor costs
Difficult to cast if the part requires a core, the hole is smaller than 1.6mm or deeper than 1.5 times the diameter