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Ceramic molding process helps metalcasting facilities remain competitive.



The intense competition seen throughout the metalcasting industry today favors two kinds of operations--those that are highly mechanized mech·a·nize  
tr.v. mech·a·nized, mech·a·niz·ing, mech·a·niz·es
1. To equip with machinery: mechanize a factory.

2.
 and can produce in bulk at minimum cost and firms employing minimum skill, low cost labor. But one area where a conventional metalcasting facility can still compete is in the production of precision cast components.

Precision castings can be made by conventional sand technologies but often require considerable skills. At best, overall accuracy can be very good but surface finish leaves much to be desired. No cast component produced in a sand mold can yield the type of surface finish one would expect of a typical investment casting investment casting

Precision casting for forming metal shapes with minutely precise details. Casting bronze or precious metals typically involves several steps, including forming a mold around the sculptured form; detaching the mold (in two or more sections); coating its
. However, the costs and logistics of converting a conventional metalcasting facility to an investment casting firm are often prohibitive.

The answer is a method of casting that lies halfway between traditional sand techniques and investment casting that is commonly referred to as ceramic molding. Increasing demand tot greater ease of operation and better accuracy has led to more recent developments by Unicast Development Co., New Haven New Haven, city (1990 pop. 130,474), New Haven co., S Conn., a port of entry where the Quinnipiac and other small rivers enter Long Island Sound; inc. 1784. Firearms and ammunition, clocks and watches, tools, rubber and paper products, and textiles are among the many , Conn., which develops and distributes the Unicast Process worldwide. This technology emphasizes ease of molding with minimal need for additional skills. There are few limitations on size or alloy, and castings are being produced in all materials from aluminum and copper-based alloys and iron, to most carbon and stainless steel stainless steel: see steel.
stainless steel

Any of a family of alloy steels usually containing 10–30% chromium. The presence of chromium, together with low carbon content, gives remarkable resistance to corrosion and heat.
 alloys.

The ceramic molds are formed by pouring a quick setting refractory refractory

Material that is not deformed or damaged by high temperatures, used to make crucibles, incinerators, insulation, and furnaces, particularly metallurgical furnaces.
 slurry slurry,
n a thin mixture of insoluble material floating in liquid.


slurry

solids in suspension. Used as a method of feeding pigs—slurry is pumped through fixed lines and delivered to troughs by hoses equipped with gasoline pump fittings.
 over the pattern, usually within a removable flask flask (flask)
1. a laboratory vessel, usually of glass and with a constricted neck.

2. a metal case in which materials used in making artificial dentures are placed for processing.
. The slurry is prepared as needed as needed prn. See prn order.  using a simple mixer to combine the graded dry ceramic with a liquid organo-silicate binder. There is a choice of numerous ceramic blends and binders depending on the ultimate mold of core strength needed and the degree of permeability permeability /per·me·a·bil·i·ty/ (per?me-ah-bil´i-te) the property or state of being permeable.

per·me·a·bil·i·ty
n.
1. The property or condition of being permeable.

2.
 and surface finish required. Cores ate produced using a standard type corebox but with a ceramic slurry variation that permits good venting, high strength and ease of removal. As with mold patterns, coreboxes need to be accurately constructed and well finished to yield optimum internal surfaces in the finished casting.

Slurry setting time is usually within 3-5 min., and the set section can be removed manually or with a simple stripping machine, with the pattern or corebox removed, the molded ceramic is chemically stabilized then quickly flame dried. This is followed by rapid high temperature curing, usually to about 1,800F (1,000C) in a kiln-type furnace. Depending on the alloys being cast, molds can be poured hot, immediately after furnace removal, of can be cooled to lower temperature.

The latest applications for the process continue to extend beyond the original concepts to include cores and other applications. By using ceramic molding technology, ceramic cores that can be set into a conventional sand mold for pouring can be produced Where greater overall accuracy and surface finish is needed, the cope and drag In foundry work, the terms Cope and Drag refer to the upper and lower parts of a two-part casting flask, used in sand casting. The flask is a wood or metal frame, which contains the molding sand, providing support to the sand as the metal is poured into the mold.  mold halves as well as the core can be produced entirely in ceramic. Figure 1 shows a typical shell arrangement for producing impellers.

[FIGURE 1 OMITTED]

With the process, there is no penalty for short or single run castings, allowing wide diversification of applications. An entirely independent market that often uses short run castings is cast-to-size tooling. This includes cast cavities, molds and inserts for plastics molding, diecasting and forging dies, even foundry patterns and coreboxes. Complex shapes and intricate geometry can often be cast at much lower cost than equivalent machined sections. Figure 2 illustrates a cast-to-size beryllium-copper mold used for producing plastic toy moldings.

[FIGURE 2 OMITTED]

Ceramic slurry costs ate higher than sand, but the difference is not significant on small molds. It becomes more of a concern on larger molds and is compensated for by forming a thin ceramic shell backed by a low-cost supporting sand mold.

Through increasing ceramic technology, the Unicast Process has allowed smaller, conventional metalcasting facilities to recoup recoup

To sell an asset at a price sufficient to recover the original outlay or to offset a previous loss.
 the work they have lost over the past decade.

Select No. 091 at www.moderncasting.com/info
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Title Annotation:New Product
Publication:Modern Casting
Geographic Code:1USA
Date:May 1, 2004
Words:653
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