An expandable (i.e. consumable) pattern, usually made of wax, is produced through an “Injection Press” by forcing hot pasty wax at high pressure into a metallic mould called a die.
Disposable Wax Patterns are produced by Injecting Wax in the Dies. These Wax Patterns are positive models of the part intended for casting and reflect the precise geometry of the finished parts. Multiple numbers of Wax Patterns are made, connected and assembled by ‘gates’ to Wax spruce to form a tree or cluster.
The Wax assembly is dipped into refractory slurry. The Assembly after a such wet dip is coated with refractory grains, called “Stucco”.
A number of coats are given with a time of 6 to 8 hour to let the coat dry. The whole process can take upto five days though can be speeded up if required by using special chemicals.
This process is done in Temperature and Humidity controlled rooms, to achieve best dimensional accuracy and excellent surface finish.
This process is invested or covered with refractory layers, it will be dried and thereafter the wax inside the Assembly automatically removed by melting inside a steam autoclave. As the wax gets removed, and in the past it was “lost” by burning off, this process of casting is also called to “Lost Wax Process”.
The ceramic moulds are baked at temperature ranging from 900⁰ C to 1150⁰C depending on the geometry and size of the casting. The molten metal is then poured in the baked ceramic moulds for filling of the entire moulds cavity.
When the metal has cooled and solidified, the ceramic shell is broken off by vibration or by water blasting. The parts are cut away from the central spruce using a high speed abrasive cutter or conventional engineering method. Then send for the Heat Treatment as per the material specifications.
Heat Treatment graph cycles are recorded and documented.