29-04-2014, 02:35 PM
INVESTMENT CASTINGS
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HISTORY
The history of lost-wax casting dates back thousands of years.
Its earliest use was for idols, ornaments and jewellery
In the 1940s, World War II increased the demand for precision net shape manufacturing and specialized alloys leading to investment casting boom.
Dr. William H. Taggart of Chicago, whose 1907 paper described his development of a technique. He also formulated a wax pattern compound of excellent properties, developed an investment material, and invented an air-pressure casting machine.
DEFINITaION
Investment Casting (Lost Wax Process)
A pattern made of wax is coated with a refractory material and then metal is poured.
"Investment" comes from a less familiar definition of "invest"
"to cover completely," which refers to coating of refractory material around wax pattern
It is a precision casting process ,capable of producing castings of high accuracy and intricate detail.
WHY INVESTMENT CASTINGS?
Design Flexibility:Investment casting produces near net shaped configurations, offering designers and engineers freedom of design in a wide range of alloys.
Wide Choice Of Alloys:Various Ferrous and Non Ferrous metals are routinely cast.
Eliminate Tooling Setup:By offering near net shaped configuration ,fixturing costs are substantially reduced or eliminated.
CONCLUSIONS
Investment casting may be termed as “lost-wax casting”
Investment casting is practical for prototype and low-volume production applications. In less than two weeks, prototype castings in numerous alloys are ready for testing,evaluation or use.
Although it is an expensive process,it produces quality casting.
In many cases weight is reduced by more than 50% percent thus inputing more raw material usage and increasing the overall productivity of the unit.
Unlimited design freedom since draft angles, cores, parting lines, etc., are irrelevant.Very complicated products can be manufactured which are almost impossible by casting process,welding etc.
Patterns and molds are expendable