Investment casting is a casting process that uses wax molds to shape ceramic molds. It has a history of more than 5,000 years and is one of the oldest metal casting methods. At first, it was used to make statues and jewels with beeswax.
Investment casting is different from die casting because it uses disposable wax molds, while die casting uses reusable molds. Investment casting is still a casting method used in foundries to this day. Investment casting is a high-precision metal casting method. The wax mold manufacturing process can produce precise shapes with smooth surfaces. These castings can be used in application fields with extremely high precision requirements, such as aerospace parts, automotive parts, medical equipment, etc. It can also be used in other applications, but its main advantage is that it can precisely manufacture thin, small and complex parts.
Investment casting process involves multiple steps and is the most labor-intensive casting method. These steps include master mold making, wax pattern making, mold making, wax removal, pouring, demolding and fine processing.
Since the wax mold can be damaged during the casting process, a master model is necessary if castings are to be mass-produced. The "master mold" or an exact replica of a part is made as the basis for future wax molds.
Inject hot wax into the master model to solidify it. After solidification, the metal foundry can use the wax mold for casting. If the parts need to be mass-produced, they are usually added to a pouring system (or "tree") to accommodate multiple wax molds for casting.
The wax type is applied to the slurry usually composed of refractory materials such as silica, ceramics, gypsum or plastics, and then left to dry. Repeat this process as needed until the mold reaches the required thickness.
After the wax has solidified, place the ceramic shell into a furnace or autoclave, melt the wax out of the mold, and leave a hollow shell in the desired casting shape.
Pour the molten metal into the hot mold and fill the mold space with the required model. The mold must be in a high-temperature state so that the molten metal can reach the relatively narrow and hard-to-reach parts of the mold, thereby ensuring the accuracy.
After the mold is fully cooled, it is removed from the casting by hammering, vibration, sandblasting or other methods. If there is a gating system, each casting should be removed separately.
Then the castings are cleaned and ground. If other modifications are needed to the casting, manual tool processing and welding will be required.