Tag Archive: centrifugal casting

  1. Advantages of Centrifugal Casting

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    When it comes to manufacturing gear blanks, centrifugal casting holds several advantages over other methods.

    The process involves pouring molten metal into a rapidly spinning mold cavity. The force produced by the mold’s spinning forces the material to conform to the shape of the mold. Additionally, extreme pressures that form within the casting device drive material contaminants to the center of the casting, allowing them to be easily removed in future finishing operations.

    Advantages of the Centrifugal Casting Process

    There are a number of advantages to using centrifugal casting for the manufacture of cylindrical and circular parts, such as:

    • Greater strength. The greater strength of parts produced using centrifugal casting is a result of higher density grain structures. As the process allows for more control over directional solidification, the grain structure is more uniform and its mechanical properties are almost equal in all directions. This higher structural density increases the life span of the component and allows for higher stress tolerances. Another factor that contributes to the enhanced part strength is higher product purity, which eliminates internal porosity and improves structural uniformity.
    • Increased product purity. During the casting process, the spinning of the mold places extreme pressures on the molten material. This pressure causes lighter contaminants and impurities to separate from the denser metal. These impurities gather in the bore of the component, minimizing the risk of formation of weak points or areas of porosity within the metal structure. The machining process following casting removes these impurities, leaving a highly pure end-product.
    • Better production cost-efficiency. Increased product purity also affects production cost-efficiency. As impurities gather at the interior surface of the part and are machined out, there is a reduction in the number of defective parts and rejects. The lack of porosity produced through the centrifugal casting process also allows manufacturers to use less metal and produce less material waste. In addition, faster setup and shorter production cycle times lead to improved production cost-efficiency.

    Limitations of Centrifugal Casting

    Although centrifugal casting offers several manufacturing advantages, the process is limited in its production capabilities. Some of the limitations of centrifugal casting include:

    • Size. To avoid the creation of a parabola at the bottom of the casting—which increases machining time—the height-to-diameter ratio used in vertical casting is 2:1. This requirement limits the size of the produced part. In some cases, horizontal casting provides the solution to these limitations​.
    • Internal diameters. Designs with smaller internal diameters also pose a challenge for centrifugal casting operations. The purity and strength advantages of centrifugal casting decrease as the inside diameters of the components decreases. The issue stems from the higher RPMs required to produce the necessary G forces to form the cast product. Although these speeds are possible, there are significant safety issues related to operating at higher RPMs.
    • Shape. The centrifugal casting process only provides production advantages to parts with a cylindrical geometric shape. Although other mold shapes are possible, the loss of the structural and purity benefits and the additional cost of the unique die and post-processing operations make its use impractical outside of producing cylindrical shapes.

    Additional Casting Services From Accurate Specialties

    At Accurate Specialties, we offer a broad range of casting capabilities. In addition to centrifugal casting, we provide:

    • Spin casting. This type of casting allows for the production of parts with high material purity and consistent weight and density. Additionally, when used for the manufacture of bronze gear blanks, the process creates stronger bonds between the gear tooth and hub.
    • Chilled casting. This casting method produces cast products with tight grain structures and outstanding uniformity. These properties result from pouring molten bronze into an aluminum or steel mold, which is at a significantly lower temperature, producing a rapid cooling or “freezing” effect.
    • Continuous casting. Continuous is cost-effective for large volumes of simple parts. It produces parts with favorable mechanical properties, even distribution of alloy agents, and better machinability, friction, and wear properties. The process involves pouring molten bronze alloys through a graphite mold, cooling them into 12-foot bars, and cutting them into “pucks” for further formation.

    Bronze Centrifugal Casting Solutions From Accurate Specialties

    For the manufacture of cylindrical and circular parts, centrifugal casting offers several advantages, including greater part strength, higher product purity, and better cost-effectiveness.

    At Accurate Specialties, we utilize several casting methods—including centrifugal casting—to produce high-quality bronze gear blanks for our customers. Our solid bronze gear blanks are available in diameters ranging from 1–50 inches.

    To learn more about our centrifugal casting solutions, contact us or request a quote today.

  2. Vertical Centrifugal Casting

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    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
    • Flanges
    • Sprockets

    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.