Evaporative-pattern casting is a type of
casting process that uses a
pattern made from a material that will
evaporate
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
when the molten
metal is poured into the molding cavity. The most common evaporative-pattern material used is
polystyrene foam
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
.
[.]
The two major evaporative-pattern casting processes are:
*
Lost-foam casting
*
Full-mold casting
The main difference is that lost-foam casting uses an
unbonded sand and full-mold casting uses a bonded sand (or green sand). Because this difference is quite small there is much overlap in the terminology. Non-proprietary terms that have been used to describe these processes include: cavityless casting, evaporative foam casting, foam vaporization casting, lost pattern casting, the castral process, and expanded polystyrene molding.
[.] Proprietary terms included Styro-cast, Foam Cast, Replicast, Policast.
and Lost Foam Sintered Shell (LFSS)
History
The first patent for an evaporative-pattern casting process was filed in April 1956, by Harold F. Shroyer. He patented the use of foam patterns embedded in traditional
green sand for
metal casting. In his patent, a pattern was machined from a block of
expanded polystyrene
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...
(EPS), and supported by bonded sand during pouring. This process is now known as the full mold process.
In 1964, M.C. Flemmings used unbonded sand for the process. The first
North American foundry to use evaporative-pattern casting was the Robinson Foundry at
Alexander City,
Alabama.
General Motors
The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...
' first product using these processes was the 4.3 L, V-6 diesel
cylinder head, which were made in 1981 at
Massena,
New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* '' ...
.
A study found in 1997 that evaporative-pattern casting processes accounted for approximately 140,000 tons of aluminium casting in the United States. The same survey forecast that evaporative-pattern casting processes would account for 29% of the aluminium, and 14% of the ferrous casting markets by 2010.
[.]
References
Bibliography
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