The techniques used to mold and shape metals have evolved significantly over the centuries. Forging, sand casting (static casting), and rolled and welded procedures are just some of the traditional methods used to manufacture metal parts and components. However, there are many applications where these fabrication methods are either unsuitable or inefficient.
The centrifugal casting process can produce components with intricate geometries at a lower cost and with reduced machining requirements in comparison to other commonly used casting methods. The process entails pouring molten metal into the center of a rotating mold. The centrifugal force induced by the rotation pushes the molten metal against the inner wall of the mold to create the intended shape. The molding dies can be oriented horizontally (horizontal centrifugal casting) or vertically (vertical centrifugal casting).
When to Rely on Centrifugal Casting
Centrifugal casting has traditionally been used to manufacture hollow shapes with specified thicknesses in the instance where the end product requires the most dense “best” material on the OD of the product. Due to its mode of operation, centrifugal casting is most suitable for components with axisymmetric geometries (i. e., shapes that are symmetric about a given axis). One benefit of centrifugal casting is reduction in instances of retained air pockets or porosity in the finished product.
Because centrifugal casting is done with a predetermined mold size and controlled via electronic means, it is best suited to applications that require high accuracy. Products with precise dimensions and weight can be manufactured to tight tolerances by controlling the casting process with computerized controls.
Although most commonly associated with molten metals, there are centrifugal casting advantages when used with virtually any material that can be melted into a pourable slurry, including concrete, glass, ceramic, and plastics.
The Vertical Centrifugal Casting Process
The vertical centrifugal casting process consists of several stages. At the beginning, the molten metal is poured into a vertically oriented preheated rotating die. The centrifugal forces in the vertical spinning mold then cause the molten metal to spread horizontally and vertically along the inner diameter of the mold so that it assumes the specified shape.
As the mold and die spin, the denser elements of the molten metal are pushed toward the outer diameter. In a process known as directional solidification, the mold acts as a cooling surface which solidifies the metal from the outer diameter as it moves towards the bore. This process causes impurities to ‘float’ toward the inner diameter, from which they can be machined away when the casting process is complete.
The result is a final product with superior mechanical properties and a more uniform, fine grain structure. For this reason, vertical centrifugal casting techniques are used to manufacture components in the aviation, aerospace, military, petrochemical, and any other industries that require high-reliability components.
Although vertical and horizontal castings can produce products of similar quality, castings with vertical orientations are more suitable for cylindrical shapes with a diameter several times larger than the depth (or height) of the cast. Rings and bearings are examples of products best suited to vertical centrifugal casting.
Vertical centrifugal casting can also be used to cast non-cylindrical parts such as valves and propellers by using specialty castings. Other products that are commonly produced with vertical centrifugal casting methods include:
- Balls for ball valves
- Gear blanks
- Short bushings
Accurate Specialties Inc. is an industry leader in manufacturing centrifugal cast bronze gear blanks. Our vertical centrifugal casting techniques produce gear blanks with high purity, density, and durability. Our state-of-the-art equipment generates pressures up to 60 times the force of gravity to segregate and remove impurities and other unwanted elements from our products. All of our gear blanks are machined with high dimensional accuracy using our advanced 4-axis, CNC-controlled VTC to ensure proper installation and minimization of errors.
At Accurate Specialties Inc., we have developed countless gear blanks for thousands of applications for over 30 years. Our ISO 9001:2015 certified quality systems ensure that each one of our gear blanks and friction materials exceeds industry standards and leaves our facilities in the best possible condition.
To learn more about our centrifugal cast gear blanks or our other services, feel free to contact us.