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Manufacturing:
Metal Casting
Metal
Casting Techniques - Investment
Casting or Lost Wax
Investment Casting
is the process of completely investing a
three-dimensional pattern in all of its
dimensions to produce a one-piece destructible
mold into which molten metal will be poured.
A refractory slurry flows around the wax
pattern, providing excellent detail.
The wax patterns are assembled
on a "tree" and invested with
a ceramic slurry. The tree is then immersed
into a fluidized bed of refractory particles
to form the first layer of the ceramic shell.
The mold is allowed
to dry and the process repeated with coarser
material until sufficient thickness has
been built up to withstand the impact of
hot metal.
When the slurry
hardens, the wax pattern is melted out and
recovered and the mold or ceramic shell
is oven cured prior to casting.
Most materials
can be cast by this process but the economics
indicate that fairly high volume is necessary
and the shape and complexity of the castings
should be such that savings are made by
eliminating machining.
Advantages
- Excellent accuracy and
flexibility of design.
- Useful for casting alloys
that are difficult to machine.
- Exceptionally fine finish.
- Suitable for large or
small quantities of parts.
- Almost unlimited intricacy.
- Suitable for most ferrous
/ non-ferrous metals.
- No flash to be removed
or parting line tolerances.
Disadvantages
- Limitations on size
of casting.
- Higher casting costs
make it important to take full advantage
of the process to eliminate all machining
operations.
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