Centrifugal Casting

Centrifugal casting, sometimes called rotocasting, is a metal casting process that uses centrifugal force to form cylindrical parts. This differs from most metal casting processes, which use gravity or pressure to fill the mold. In centrifugal casting, a permanent mold made from steel, cast iron, or graphite is typically used. However, the use of expendable sand molds is also possible. The casting process is usually performed on a horizontal centrifugal casting machine (vertical machines are also available) and includes the following steps:

  1. Mold preparation - The walls of a cylindrical mold are first coated with a refractory ceramic coating, which involves a few steps (application, rotation, drying, and baking). Once prepared and secured, the mold is rotated about its axis at high speeds (300-3000 RPM), typically around 1000 RPM.
  2. Pouring - Molten metal is poured directly into the rotating mold, without the use of runners or a gating system. The centrifugal force drives the material towards the mold walls as the mold fills.
  3. Cooling - With all of the molten metal in the mold, the mold remains spinning as the metal cools. Cooling begins quickly at the mold walls and proceeds inwards.
  4. Casting removal - After the casting has cooled and solidified, the rotation is stopped and the casting can be removed.
  5. Finishing - While the centrifugal force drives the dense metal to the mold walls, any less dense impurities or bubbles flow to the inner surface of the casting. As a result, secondary processes such as machining, grinding, or sand-blasting, are required to clean and smooth the inner diameter of the part.

Centrifugal casting is used to produce axi-symmetric parts, such as cylinders or disks, which are typically hollow. Due to the high centrifugal forces, these parts have a very fine grain on the outer surface and possess mechanical properties approximately 30% greater than parts formed with static casting methods. These parts may be cast from ferrous metals such as low alloy steel, stainless steel, and iron, or from non-ferrous alloys such as aluminum, bronze, copper, magnesium, and nickel. Centrifugal casting is performed in wide variety of industries, including aerospace, industrial, marine, and power transmission. Typical parts include bearings, bushings, coils, cylinder liners, nozzles, pipes/tubes, pressure vessels, pulleys, rings, and wheels.

Centrifugal Casting
Centrifugal Casting

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Typical Feasible
Shapes: Thin-walled: Cylindrical
Solid: Cylindrical
Thin-walled: Complex
Solid: Complex
Part size: Diameter: 1 - 120 in.
Length: Up to 50 ft.
Weight: Up to 5 tons
Materials: Metals
Alloy Steel
Carbon Steel
Cast Iron
Stainless Steel
Surface finish - Ra: 63 - 500 μin 32 - 500 μin
Tolerance: ± 0.01 in. ± 0.002 in.
Max wall thickness: 0.1 - 5.0 in. 0.1 - 5.0 in.
Quantity: 100 - 10000 1 - 10000
Lead time: Weeks Days
Advantages: Can form very large parts
Good mechanical properties
Good surface finish and accuracy
Low equipment cost
Low labor cost
Little scrap generated
Disadvantages: Limited to cylindrical parts
Secondary machining is often required for inner diameter
Long lead time possible
Applications: Pipes, wheels, pulleys, nozzles

Disclaimer: All process specifications reflect the approximate range of a process's capabilities and should be viewed only as a guide. Actual capabilities are dependent upon the manufacturer, equipment, material, and part requirements.

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