What Parts Can Be Made Using Centrifuge Casting?
There may now be lots of fancy manufacturing methods like 3D printing but that does not mean that the older methods are no longer viable. Old-fashioned methods like forging and casting are still superior in terms of part strength and economics for high-volume production.
In this article, we will be focusing on a specific type of casting – centrifuge casting. Some people can also refer to this as spin casting or roto casting. How exactly does centrifuge casting work? What are the parts and products we commonly see that are made using centrifuge casting?
How does centrifuge casting work?
Centrifuge casting is a type of casting that uses the centrifugal force generated by rapid rotation to push any molten material into the inner walls of a mold. This process is mainly used for making metal and alloy parts, but glass is also a common material. By the very principle of its operations, centrifuge casting is appropriate for parts that have geometries that are symmetrical with respect to an axis of rotation.
Centrifuge casting makes use of a permanent mold typically made of graphite, steel, or cast iron. This mold is held in place by a series of rollers that are connected to a motor. At one end of the mold is a spout that allows for the introduction of molten material.
The mold can have an exhaust on the other side to release pressure as the material is introduced. Alternatively, the air inside the mold can be pumped out to create negative pressure. This is a variation called vacuum centrifuge casting and is ideal when working with metals that are highly reactive to oxygen.
While the mold is rotating, molten material is introduced via the spout. The forces of centripetal acceleration force the material against the walls of the mold. The molten material is distributed evenly and consistently and cools down from the outside inwards.
After the part has fully cooled, its outer surface can be enhanced via machining. This is not always necessary, as centrifuge cast parts can have a smooth finish as-is.
The entire centrifuge casting apparatus needs to be very stable for safety. This is considering the weight of the materials and the rotational speeds involved, often exceeding 300 rpm. A sturdy foundation is critical in designing equipment for centrifuge casting.
Parts made with centrifuge casting
Any part that appears symmetric with respect to a rotational axis has likely been made using centrifuge casting. This may not always be obvious because centrifuge casting can be done in either of two possible orientations:
In this method, the mold and the axis of rotation are horizontal. This is appropriate when parts are a lot longer than their diameter measurements. However, highly complex features are difficult to recreate with horizontal casting.
Horizontal casting is typically used for pipes and tubes. There are used by high-performance industries including power plants, automobile manufacturers, and food manufacturers. Even the pipes and tubes used for home construction are likely made using this variation of centrifuge casting.
In vertical casting, the mold is set up so that the axis of rotation is along the vertical direction. Doing vertical casting is much easier but it is only appropriate for parts that have large diameter-to-length ratios.
Vertical casting can be done for both cylindrical and non-cylindrical parts. Rings, flanges, and bearings are typically made via vertical casting, but more geometrically complex parts like valve seats, pump housing, and gear blanks can also be produced.
Pros and cons of centrifuge casting
Centrifuge casting is one of the more unique manufacturing methods because it performs for producing the parts that are geometrically appropriate. However, it is also very limited in the types of geometries that it can accommodate. When deciding whether a part is suitable for centrifuge casting, these pros and cons have to be considered:
If the inner surface of the mold is smooth, then the finished part from centrifuge casting will also have a very smooth finish. With a minimal need for machining, doing centrifuge casting for high-volume production is efficient and cost-effective. The low manufacturing cost and good output quality of centrifuge casting is a rare combination that few methods can offer.
If a die has been made for centrifugal casting, then it can be used for casting different materials including both ferrous and non-ferrous metals. One unique trait of centrifuge casting is that the same die can be used even for parts with different wall thickness values. The only parameter that has to be adjusted is the amount of molten material that is introduced into the die while casting. Again, this makes centrifuge casting cost-effective for manufacturing a wide portfolio of products.
Better properties and accuracy
The process of material deposition via centrifugal forces promotes density layering and good grain distribution. This typically translates to better metallurgical properties and parts that are mechanically stronger. Moreover, any impurities in the metal material tend to shift to the outer surface of the finished part. This makes them easy to remove via machining.
Centrifuge casting is also superior to other manufacturing methods in terms of dimensional accuracy. As the molten material hits the walls of the mold, the material starts to cool down from the outside and in an inward direction. While the material slowly solidifies, centrifugal forces continue to be applied via the rotation of the mold. This provides enough pressure to counteract the effects of contraction via cooling.
With the quality and accuracy benefits of centrifuge casting, it is often the go-to process for parts that are used for high-performance or those that have very small margins of error.
Limited geometry options
The biggest downside of centrifuge casting is that it is limited only for parts that are rotationally symmetrical. If this basic qualification is not met, then a manufacturer will have to look at other manufacturing methods such as forging, investment casting, vacuum casting, or machining.
Requires a high capital
As with many traditional manufacturing methods, much of the cost associated with centrifuge casting comes from creating the die or mold. This means that it becomes only practical if you plan on making a high number of copies of the same part. Fortunately, this is typically the case for manufacturers of pipes, tubes, and other engineering components.
As long as the geometry is appropriate, there really is no worthwhile alternative to centrifuge casting. It’s fast, cost-effective, and yields parts with excellent quality and accuracy. The use of centrifugal forces to ensure the even distribution of material is a stroke of genius that has proven to be one of the more brilliant ideas through the years.
Centrifuge casting is one of the manufacturing methods that exemplifies the excellence of practices that have been tested and refined through time. It’s also one of the more ingenious techniques of manufacturing and has proven to be irreplaceable for creating cylindrical parts.
If you look around you, you can probably spot a handful of items that were made using centrifuge casting. A testament to the versatility of this process is the fact that produces parts that can see in a household as well as those used in power plant, airplanes, and space shuttles.