Casting ProCess
dia is attributed as one of the first civilizations to use casting methods to mass-produce coins. Around the middle of the first millennium BC
(1000 BC – 1 BC), coins used were made from silver, but as the millennium progressed, the coins shifted to a cast copper alloy. [4] New
technology was developed to mass-produce the new copper coins. Introduced was a multi-piece, stackable coin template mold. Multiple
molds were placed on top of one another into a clay cylinder so molten metal could be poured down the center, filling and solidifying in the
open spaces.[4] This process allowed one hundred coins to be produced simultaneously.[4]
In the Middle East and West Africa, the lost wax technique was used very early in their metallurgy traditions, while China adopted it much
later. In Western Europe lost wax techniques are considered to have been hardly used especially in comparison to that of the Indus Valley
Civilisation.[4] There were no pieces of lost wax found in the capital of Anyang during the Shang dynasty (1600–1040 BC) while a large amount
(100,000 pieces) of piece-mould fragments were found. This led to the conclusion that lost wax was not performed in the capital during this
dynasty. However, the discovery of a mask made using the investment moulding dated at around 1300 BC indicated that the lost wax
technique may have influenced other regions in China.[10]
Historians debate the origin of the development of the cannon, but most evidence points to Turkey and Central Asia in the 18th and 19th
century. The casting process of a cannon is a bit more complex with the use of a clay core, a template which has clay moulded around it and
then broken out, followed by an assembly in a casting pit that involves binding the casting with iron bands.[4]
Types
[edit]
Main article: List of manufacturing processes § Casting
Metal
[edit]
Judenplatz Holocaust Memorial (Nameless Library), by Rachel Whiteread. Concrete cast of books on
library shelves turned inside out.
Main article: Casting (metalworking)
In metalworking, metal is heated until it becomes liquid and is then poured into a mold. The mold is a hollow cavity that includes the desired
shape, but the mold also includes runners and risers that enable the metal to fill the mold. The mold and the metal are then cooled until the
metal solidifies. The solidified part (the casting) is then recovered from the mold. Subsequent operations remove excess material caused by
the casting process (such as the runners and risers).
Plaster, concrete, or plastic resin
[edit]
Main article: Resin casting
Plaster and other chemical curing materials, such as concrete and plastic resin, may be cast using single-use waste molds as noted above,
multiple-use 'piece' molds, or molds made of small rigid pieces or of flexible material such as latex rubber (which is in turn supported by an
exterior mold). When casting plaster or concrete, the material surface is flat and lacks transparency. Often topical treatments are applied
Casting ProCess
to the surface. For example, painting and etching can be used in a way that gives the appearance of metal or stone. Alternatively, the
material is altered in its initial casting process and may contain colored sand so as to give an appearance of stone. By casting concrete,
rather than plaster, it is possible to create sculptures, fountains, or seating for outdoor use. A simulation of high-quality marble may be
made using certain chemically-set plastic resins (for example, epoxy or polyester, which are thermosetting polymers) with powdered stone
added for coloration, often with multiple colors worked in. The latter is a common means of making washstands, washstand tops and shower
stalls, with the skilled working of multiple colors resulting in simulated staining patterns as is often found in natural marble or travertine.
Fettling
[edit]
Raw castings often contain irregularities caused by seams and imperfections in the molds,[10] as well as access ports for pouring material
into the molds.[11] The process of cutting, grinding, shaving or sanding away these unwanted bits is called "fettling" in British English. [12][13] In
modern times robotic processes have been developed to perform some of the more repetitive parts of the fettling process, [14] but
historically fettlers carried out this arduous work manually,[5] and often in conditions dangerous to their health.[15] Fettling can add
significantly to the cost of the resulting product, and designers of molds seek to minimize it through the shape of the mold, the material
being cast, and sometimes by including decorative elements.[16][10]
