Pattern/Die Making :
To manufacture any part, item, product or piece you require an aluminum die for that particular product. The die is then required to produce wax patterns of the same product. Usually the die cost varies depending upon the complexity of the product as well as the metal from which the die is to be manufactured. Generally aluminum dies are easy to be handled as they are lightweight and cheaper to make changes on it compared to other metal dies.
Wax Injection :
Wax replicas of the desired casting are produced by injection moulding. These replicas are called wax patterns
Once the wax pattern has been made it is assembled with various other wax components to make a metal delivery system called the gate and the runner. The gate and runner’s shape and size would change according to the product shape size in direct proportion. The patterns are joined to the feeding system by dip sealing. The gate of the pattern can be dipped in molten wax and held against a wax runner or sprue before the wax sets which takes only few seconds.
The few important aspects of the assembly is the gating and the metal deliverying or the feeding system; as compared with other casting methods, the purpose of gating system here is to convey the molten metal to the mold cavity. The system must be designed to control metal velocity and to assure distribution of the metal to all areas of the cavity. Gate sizes and locations play critical role in determining the solidification of metals.
Shell building :
The shell is built by immersing the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand. Upto eight layers may be applied in this manner.
After drying of the shell moulds, they are now ready to be dewaxed. The technique is to shock-heat the mould in a steam autoclave to cause the wax to melt very rapidly at its surface and percolate into the porous mould. This avoids the mould cracking which occurs when wax is heated up slowly and expands as a solid. The resultant mould cavity is a faithful reproduction of the shape of the wax pattern and original die cavity. More than 80% of the wax can be recovered and recycled in this manner.
Now the shells are ready to be poured after a through visual inspection for any leaks or cracks in the shell.
The shells are placed into a shell baking furnace for an hour before the pouring of metal. After the molten metal reaches the desired temperature the shells are taken out from the baking furnace and are kept on the pouring bed to pour the molten metal in to it, the desired shaped metal is casted.
A sample before pouring the molten is checked with spectrometer to verify the chemistry of the metal.
When the metal has cooled and solidified, the ceramic shell is broken off by vibration or water blasting. The parts are cut away from the central sprue using a high speed abrasive cutter. After minor finishing operations, heat treatment and inspection, the castings identical to the original wax patterns are ready to be shipped to the customer.