What Is Rotor Balancing and Why Is It Essential?

Rotors in rotor balance machineRotors are a critical component used to convert electric or electromagnetic energy into rotational motion. For rotors to operate reliably, they must maintain even weight distribution across the rotational axis. Too much weight on one side creates uneven mass distribution known as “unbalance”.

Rotating parts in any mechanical assembly can become unbalanced. Uneven weight distribution of a rotating component causes the part’s rotational center to be out of alignment with the geometric axis. When unbalance occurs, the operational efficiency and safety of the system in which the rotor operates are compromised. Rotor balancing can help to prevent issues caused by unbalance, reducing noise and vibration and extending the life of your system.

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What Are the Various Rotor Groups?

Rotors are grouped into two categories: rigid and flexible. Rigid rotors can be balanced at lower speeds, as long as there is sufficient centrifugal force to detect the unbalance. Flexible rotors, on the other hand, deflect outward from the rotational axis, and the center of rotation moves away from the rotational axis as the speed increases. Unlike rigid rotors, flexible rotors must be balanced in stages, starting with lower speeds and slowly working up to operating speed.

Why Is Rotor Balancing Essential?

High levels of vibration caused by unbalance can cause equipment to operate less reliably, which results in increased energy usage, decreased operational efficiency, and reduced equipment service life. The force exerted by the dynamic load from an unbalanced rotor will cause wear to the rotor itself, the bearings and mountings holding it in place, and the machine’s structural support. Although the severity of the dynamic load varies depending on the degree of unbalance and the rotation speed, any unbalance can cause problems.

Silver rotor balancing machine in operation

Vibration from an unbalanced rotor creates excessive noise and resonance, which will ultimately compromise the structural integrity of the equipment that supports the rotor assembly. The damage caused by unbalance is especially apparent in bearings, suspension equipment, support housing, and the equipment foundation. These components are typically exposed to the highest level of stress caused by the excess dynamic load due to unbalance. With ongoing exposure, these components will be more likely to suffer premature wear.

In addition, the high vibration caused by unbalance can loosen fasteners such as screws, nuts, and bolts, rendering the structure less stable. Pipes, electrical cables, wiring, electrical connections, and switches can also be negatively affected. With extended exposure to high levels of vibration, even nearby equipment and structures can be compromised, creating the potential for greater damage and injury.

What Are the Various Types of Unbalance?

When balancing your rotor, it is critical to understand the different types of unbalance. There are three types of unbalance, including:

  1. Static Unbalance: This type of unbalance occurs when the mass axis is displaced parallel to the shaft axis. Static unbalance is corrected only in one axial plane.
  2. Couple Unbalance: Couple unbalance occurs when the mass axis intersects with the running axis. This type of unbalance is typically corrected in two axial planes.
  3. Dynamic Unbalance: Dynamic unbalance is typically a combination of static and couple unbalance and occurs when the mass axis does not intersect with the rotational axis. This can usually be repaired by correcting the balance along two axial planes.

Contact Test Devices by SCHENCK

Rotor balancing being performed by machine on white backgroundAt Test Devices by SCHENCK, we are dedicated to providing our customers with expert balancing solutions for rotating and oscillating equipment in a wide range of applications and industries. With more than 50 years of experience, we have the knowledge, equipment, and skill necessary to provide superior balancing services for everything from modular drills to industrial crankshafts and wind power turbines. We are skilled in servicing equipment of all sizes, from miniature dental motors of only a few ounces to 400-ton steam turbine rotors.

Our expertise extends to dynamic balancing, static balancing, couple balancing, and much more. With an international team of over 900 experts, we work tirelessly to design, research, develop, and produce actionable balancing solutions for customers in the automotive, aerospace, electrical, and mechanical engineering industries. In addition, we offer maintenance services and quality control testing to ensure that your rotor equipment is operating within applicable industry standards and regulatory guidelines.

We are committed to providing superior rotor balancing services to our customers around the world. To learn more, contact us today.

Figure 1,  A Rigid Test Rotor mounted on a Schenck Hard Bearing Balancing Machine.



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