Investment Mold Foundry is one of the oldest known metal forming techniques. Here the Investment means the plastic like substance or molten metal which can stand high temperature in the process of casting and molding. Molding means the object formed by a mold or in other terms the container into which liquid is poured to create a given shape when it hardens by pouring (wax or hot metal) into the cast or mold.
The actual process scheme involves the following steps:
- Preheating the investments molds for casting in a furnace
- Then pouring the molten metal into the mold full to its capacity (if cavities are left then it can be filled completely using pressure, vacuum and centrifugal force etc.
- Then the metal is allowed to solidify
- Then by chirping or sand blasting the thin refractory mold material is to be removed
- Finally by means of an abrasive cut off machine followed by grinding the casting is to be separated from the gating system.
When all these steps are over, one piece complex intricate different geometric shaped molds can be collected in large number.
This shows that the Investment Mold Foundry is based on old Investment Casting process also known as Lost-Wax Casting wherein the equipments required are Furnace, Mold or Investment Ceramic Shell, Alloy Metal, Wax plates etc. The benefits associated with Investment Casting process are that it can produce different complex geometric shapes with a high output capacity, good surface finish and with a minimal degree of machining. Any metal which melts at a high temperature can be casted with this process.
The most important advantageous point in this methodology is that there is no parting in the mold and any type of complex intricate big and small shape can be made very easily, this is not possible with other processes. This process also has some demerits like use of highly specialized apparatus, the costly refractory materials and binders and some intermittent defects in the products.
This process as stated above is not a new process as its use can be traced in historic facts in the making of idols, ornaments and jewelery wherein the natural beeswax was used for patterns, clay for the moulds and for furnace manually operated bellows were stroked. In the present context this process of investment casting is very popularly utilized in Industries relating to Power Generation, Aerospace, Firearm Manufacturers, Military, Medical, Commercial and Automotive.
The Investment Casting process is getting popular in these industries because of close dimensional accuracy, high degree of creep resistance which can be acquired at low cost with the tolerance level ranging from typical +0.0005 inch to as low as +0.002. The surface finishing ranges from typical range of 50 to 125 to 32 to 300 micro inches. The wall thickness of cast is 0.05 and the weight ranges from 0.3 lb to 40 lbs. Also the casting products require only a little machining to create the finished part.
Thus no process parallels Investment Casting Process even today in terms of producing intricate details and close dimensional accuracy using wax or plastic patterns as it requires no drafting and the production rate can also be increased by clustering.