Centrifugal casting
Centrifugal casting in silversmithing is a 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...

 technique where a small mould is poured, then spun on the end of an arm. The centrifugal force
Centrifugal force
Centrifugal force can generally be any force directed outward relative to some origin. More particularly, in classical mechanics, the centrifugal force is an outward force which arises when describing the motion of objects in a rotating reference frame...

 thus generated encourages a successful pour.


Centrifugal casting, or centrifuging,Efunda site page with centrifugal casting fundamentals
is used as a means of casting small, detailed parts or jewelry. An articulated arm is free to spin around a vertical axle, which is driven by an electric motor or a spring. The entire mechanism is enclosed in a tub or drum to contain hot metal should the mold break or an excess of metal be used. Single use molds are prepared using the lost wax method. A small amount of metal in a crucible (a sort of ceramic pan) next to the mold is heated with a torch. When the metal is molten the arm is released, forcing (by centrifugal force) the metal into the mold. The high forces imposed on the metal overcome the viscosity, resulting in a finely detailed workpiece. A similar advantage may be obtained by vacuum casting
Vacuum casting
Vacuum casting is a casting process for elastomers using a vacuum to draw the liquid material into the mold. This process is used when air entrapment is a problem, there are intricate details or undercuts, or if the material is fiber or wire reinforced....

 or pressure casting.

For industrial casting of small parts using poured hot metal, a disk shaped mold is contained within a rotating drum, and molten metal is poured into the center.


It is applied to the fabrication of large telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...

 mirrors, where the natural curve followed by the molten glass greatly reduces the amount of grinding required. Rather than being cast by pouring glass into a mold an entire turntable containing the peripheral mold and the back pattern (a honeycomb pattern to lighten the finished product) is contained within a furnace and charged with the glass material used. The assembly is then heated while spun at slow speed until the glass is liquid, then gradually cooled over a period of months.

The technique is known in the glass industry as "spinning". The centrifugal force pushes the molten glass against the mold wall, where it solidifies. This cooling process takes anywhere between 16 to 72 hours depending on the impurities or volume of material. Typical products made using this process are television picture tubes and missile nose cones.


Centrifugal casting is commonly used to shape glass into spherical objects such as marbles
Marble (toy)
A marble is a small spherical toy usually made from glass, clay, steel, or agate. These balls vary in size. Most commonly, they are about ½ inch in diameter, but they may range from less than ¼ inch to over 3 inches , while some art glass marbles fordisplay purposes are over 12 inches ...



Many machines are available which can perform centrifugal casting, and they are relatively simple to construct. All that is required is an arm which rotates with an adequate amount of centrifugal force, a container on the end of said arm to hold both a mold and the material to be cast into the mold.

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