Evaporative-pattern casting
Encyclopedia
Evaporative-pattern casting is a type of casting
process that uses a pattern
made from a material that will evaporate when the molten metal
is poured into the molding cavity. The most common evaporative-pattern material used is polystyrene foam.
The two major evaporative-pattern casting processes are:
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, and Policast.
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
first product using these processes was the 4.3 L, V-6 diesel cylinder head
, which were made in 1981 at Massena
, New York
.
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.
Casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...
process that uses a pattern
Pattern (casting)
In casting, a pattern is a replica of the object to be cast, used to prepare the cavity into which molten material will be poured during the casting process.Patterns used in sand casting may be made of wood, metal, plastics or other materials...
made from a material that will evaporate when the molten metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
is poured into the molding cavity. The most common evaporative-pattern material used is polystyrene foam.
The two major evaporative-pattern casting processes are:
- Lost-foam castingLost-foam castingLost-foam casting is a type of evaporative-pattern casting process that is similar to investment casting except foam is used for the pattern instead of wax...
- Full-mold castingFull-mold castingFull-mold casting is a evaporative-pattern casting process which is a combination of sand casting and lost-foam casting. It uses a expanded polystyrene foam pattern which is then surrounded by sand, much like sand 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, and Policast.
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 (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
North American
North American generally refers to an entity, people, group, or attribute of North America, especially of the United States and Canada together.-Culture:*North American English, a collective term used to describe American English and Canadian English...
foundry
Foundry
A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal in a mold, and removing the mold material or casting after the metal has solidified as it cools. The most common metals processed are aluminum and cast iron...
to use evaporative-pattern casting was the Robinson Foundry at Alexander City, Alabama
Alabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
. General motors
General Motors
General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...
first product using these processes was the 4.3 L, V-6 diesel cylinder head
Cylinder head
In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket...
, which were made in 1981 at Massena
Massena (town), New York
Massena is a town in St. Lawrence County, New York, United States. The town is on the northern border of the county and is nicknamed "The Gateway to the Fourth Coast". The population was 13,121 at the 2000 census. The town of Massena contains a village also called Massena...
, New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
.
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.