Investment casting with Advantages, Limitations & Applications
Investment casting:
Wax patterns are produced by injection molding with metal die. Multiple patterns are assembled to a central wax sprue. A shell is built by immersing the assembly in a liquid ceramic slurry. Then the assembly immerse into the extremely the sand. The ceramic is dried, the wax is melted out, ceramic is fired to burn all wax. The shell is filled with molten metal by gravity pouring.
On solidification the parts, gates, sprue and pouring cup become
one solid casting. Hollow casting can be made by pouring out excess metal
before it solidifies. After metal solidifies, the ceramic shell is broken off
by vibration or water blasting. The parts
are cut away from the sprue using a high speed friction saw. Minor finishing
gives final part.
Advantages of investment casting:
•Parts of greater complexity and intricacy can be cast.
•Close dimensional control.
•Good surface finish.
•The lost wax can be reused.
•Additional machining is not required in normal course.
•Intricate shapes can be cast.
•Fairly high production rate.
Limitations of investment casting:
•Time consuming process.
•High labour cost.
•High tooling cost.
•Long lead time possible.
Applications of Investment casting:
•Turbine blades.
•Parmament parts.
•Pipe fittings.
•Lock parts.
•Hand tools.
•Jewellery.
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