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The history of molding sand is difficult to study, as much of the origins of the practice predate writing. Molding sand was used exclusively for bronze casts, which was pioneered by the ancient Chinese. The next major advancement came in India in 500 B.C. when cast-crucible steel was created.
The sand that is in contact with the casting is called facing sand, and is designed for the casting on hand. This sand will be built up around the pattern to a thickness of 30 to 100 mm (1.2 to 3.9 in). The sand that fills in around the facing sand is called backing sand. This sand is simply silica sand with only a small amount of binder and no ...
A flask has only sides, and no top or bottom, and forms a frame around the mold, which is typically made of molding sand. The shape of a flask may be square, rectangular, round or any convenient shape. A flask can have any size so long as it is larger than the pattern being used to make the sand mold.
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A sand rammer is a piece of equipment used in foundry sand testing to make test specimen of molding sand by compacting bulk material by free fixed height drop of fixed weight for 3 times. It is also used to determine compactibility of sands by using special specimen tubes and a linear scale. Sand Rammer
The pattern is made of wax, wood, plastic, or metal. The molds are constructed by several different processes dependent upon the type of foundry, metal to be poured, quantity of parts to be produced, size of the casting, and complexity of the casting. These mold processes include: Sand casting – Green or resin bonded sand mold.
The grain size, shape and distribution of the foundry sand, the type and quantity of bonding materials, the density to which the sand is rammed, and the percentage of moisture used for tempering the sand are important factors in regulating the degree of permeability.
A molding sand mixture, usually green sand or bentonite, is blown into a rectangular steel chamber using compressed air. The molding sand is then squeezed between two patterns, which are on the two ends of the chamber. After squeezing, one of the chamber plates swings open and the opposite plate pushes the finished mold onto a conveyor.