Investment casting is commonly referred to as lost wax casting
because wax is used to create the mold and then it is “lost” (or
melted away) from the mold prior to metal being added to fill the
cavity left behind by the “lost” wax. If you need a custom,
precision metal part created, investment casting is one way of
getting that part made. This process is used in many industries to
make parts from a variety of metallic material types. Nickel and
cobalt-based super alloys account for 50% of total output by value,
steels (of all types) account for 35%, aluminum accounts for about
10%, and copper and titanium alloys make up a large part of the
remaining 5%.
An investment casting mold is made in foundries by first making a
wax impression produced from high pressure dies or special
investment cast tooling; the wax can be replaced by other materials
such as foam (lost foam), or some other material that can be melted
away during the investment casting process. This wax impression is
then dipped and coated in a refractory ceramic slurry, forming an
investment casting mold with a hard skin. After this, the entire
mold is then placed in an oven and the wax is melted away. Because
the mold is formed around a one-piece wax impression (which does not
have to be pulled out from the mold as in a traditional sand casting
process), very intricate parts with recesses and indents can be
produced.
COST EFFICIENCY
Investment casting is an extremely cost-efficient process. It
reduces costly machining operations - sometimes even eliminating
them. Several parts can be made as one casting. This eliminates the
need for fabrication, which reduces assembly, welding, handling &
inspection costs. Any company that deals with high assembly costs
benefits instantly when investment casting techniques are employed
for manufacturing.
Investment casting also enables relatively small quantities of an
item, typically for research and development trials, to be produced
prior to commitment to larger production quantities. Rapid
prototyping is also possible using wax impressions produced from
digital models.
Overall, reduced material, reduced labor costs, and the elimination
of some assembly steps makes investment casting an extremely
attractive option.
VERSATILITY AND ACCURACY
Investment casting also provides tremendous design flexibility for
engineers and designers; it is regarded as a precise casting process
to fabricate near-net-shaped metal parts from almost any alloy -
thus the versatility. The name “near-net-shaped” points to the
quality and volume of the “net” or final shape. Near-net quality in
the final investment casting reduces the costly and time consuming
finishing that is usually done by machining or grinding. The
investment casting process is capable of producing precise detail
and dimensional accuracy in parts weighing from many pounds to just
a few ounces.
Although its 5,000 year history lies to a great extent in the
production of jewelry, the most common use of investment casting in
more recent history has been the production of components requiring
complex, often thin-wall castings. The one-piece mold gives rise to
a component shape that is aesthetic and uniform. It can be used to
make parts that cannot be produced by normal manufacturing
techniques, such as turbine blades that have complex shapes and
would require unusual coring in standard sand casting processes.
Nearly every industry relies on investment casting to produce
lightweight precise dimension parts with fine details including
helicopter, marine, automobile, and even jet engine companies. Parts
that require sharp finishes can be cast without extra effort.
Lettering, precision holes, splines, serrations, bosses, and even
some threads can be investment cast. Reproducing the fine detail
necessary in these by using investment casting ensures consistency
across production.
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