Centrifugal Casting – process overview

Horizontal axis centrifugal casting process diagram. Image © 2018 EngineeringClicks

Centrifugal casting is a permanent mold process which makes use of centrifugal force to fill a mold with molten material. There are 3 types of this process: centrifugal casting, semi-centrifugal casting and true centrifugal casting. The principle is the same for all three types: the mold is rotated around an axis and molten metal is poured into the pouring cup, from where it is forced into the mold by centrifugal force.

Applications

  • True centrifugal casting is used for the production of tubular parts like gun barrels, pressure vessels, pipes and nozzles.
  • Semi-centrifugal and centrifugal casting are used for the production of solid parts like flywheels, pulley wheels, gear blanks, train wheels and brake drums.

Materials

Most common metals and their alloys including steel, aluminum, copper and iron can be processed. Along with metal alloys, some composites and polymers can also be processed using this method.

Design Considerations

  • Limited to producing parts with rotational symmetry.
  • Here are some examples of the geometric limitations:

1) Maximum length of part cannot exceed fifteen meters.
2) Draft angle of approximately 1° is required.
3) Diameter range for the part is 25mm to 2m.
4) 125mm is the maximum allowable sectional thickness.
5) 2.5mm is the minimum allowable sectional thickness.
6) Machining allowances of up to 6mm should be added mostly for the inner surface in true centrifugal casting.

Process variations

  • This process is usually classified as a permanent mold process. However, it is not truly a permanent mold process because in some cases sand molds are used, so it is actually a semi-expandable/permanent mold process.
  • True centrifugal casting is used to produce hollow cylindrical parts, while the other two process types are used to produce solid parts. Semi-centrifugal casting produces radially symmetrical parts, but this is not a requirement in centrifugal casing.
  • Also known as “rotocasting”.

Economic Considerations

  • Moderate production rate, which depends upon the size of the product.
  • Moderate labor, equipment and tooling costs.
  • Finishing of the product is normally required (machining to net shape, deburring, etc).

Selection of a permanent or expandable mold depends on the production volume, quality and geometry of the product

Quality Considerations

  • Properties and quality of the finished part depend upon the distance of the mold from the rotational axis.
  • Causes unidirectional cooling of the molten material, so defects like shrinkage do not exist in finished part
  • Fine grain structure and control over the mechanical properties make this process suitable for high quality production.
centrifugal casting - train wheels

Train wheels on the production line

Centrifugal casting advantages and disadvantages

  • Advantages: Suitable for both low-volume and high-volume production. Suitable for a wide range of materials.
  • Disadvantages: Limits on product geometry. Post processing and finishing is required.

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