Dynamic Balancing: Essential Guide and 10 Expert Tips for Optimal Performance

Dynamic balancing is an essential process for reducing vibrations, improving the lifespan of rotating equipment, and increasing operational efficiency. But what exactly does this process involve, and how can you achieve optimal results? In this guide, we will explore the 10 most important expert tips to understand and apply dynamic balancing, ensuring enhanced performance and minimizing mechanical issues.

For those who don’t know, imbalance is a phenomenon that occurs in any object that makes a rotational movement. For instance, an example would be the vibration car tires create during the ride when they are not balanced. Perhaps we have seen our mechanic correct this issue when he changes our tires for the season. In order to eliminate the unpleasantness and make the ride smooth, he carries out an operation to achieve dynamic balancing.

Since imbalance generates a centrifugal force that increases linearly with the mass of the imbalance and quadratically with the rotor speed, the faster a rotor spins, the greater the imbalance effect. For this reason, and to ensure that the mechanisms we rely on daily work smoothly and precisely, each component must also be assessed from a dynamic performance perspective. The solution is dynamic balancing.

Why is Dynamic Balancing Important?

Accurate balancing is crucial not only to avoid costly repairs but also to optimize energy efficiency, reduce noise, and extend the lifespan of equipment.

We used the example of a car—perhaps the most familiar application of dynamic balancing—but even a simple kitchen blender has high-speed rotating parts and is subject to similar forces. In such cases, dynamic balancing is just as crucial.

Let’s go into detail to understand the causes and effects of the imbalance and how to achieve dynamic balancing.

How Does Imbalance Affect Machinery?

Imbalance is a situation that occurs when something is not in the correct proportions. It is an abstract concept with the general meaning of “lack of balance.” In a machine, it designates the lack of balance in the masses of a solid rotating about its axis.

In everyday usage, the noun “imbalance” also denotes the “mass generating imbalance” or the “vector of imbalance” or the “measurement of imbalance through its effects” (e.g., we say “add an imbalance to the rotor” or “that rotor has an imbalance of g-mm” or “the result of imbalances,” etc.).

The effect of imbalance as the main source of vibration is certainly not abstract; suffice it to say that the imbalance of a rotating body resting on bearings generates forces that, growing with the square of the speed of rotation, can easily reach destructive intensities. That is why it is essential to try to achieve dynamic equilibrium.

A mass applied at a certain distance from the axis of rotation only transforms a balanced rotor into an imbalanced rotor if the rotor is supported by pivots and bearings that force it to rotate about a well-defined axis. Conversely, if there is no obligatory axis of rotation, the imbalance mass merely shifts the axis of the rotor, which can again rotate smoothly around its new axis.

Top Causes of Imbalance in Industrial Equipment

1. unfinished, cast, forged components that are hardly concentric or symmetrical with respect to the axis of rotation;
2. process and assembly tolerances that produce eccentricities, clearances and errors in surface inclination;
3. inhomogeneities in the materials used due to porosity, coagulation, inclusions or irregularities in crystal structure and density;
4. chrome plating and coatings in various materials on the rotor or its components;
5. asymmetries in the rotor components due to design or construction requirements (key cavities, windings for electric motors, handles, etc.);
6. bending or deformation due to forced or heated assemblies or/a heat treatment, nitriding, etc.;
7. dissymmetries generated during operation, due to elastic, plastic or permanent deformations caused by centrifugal forces or by the fluid in which the rotor operates, or by temperature changes.

The designer has an obligation to carefully examine all rotating components to minimize possible causes of misalignment during manufacturing, installation, and operation. It must always be borne in mind that serious imbalances often require large-scale, costly and very often complex corrective actions.

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The harmful consequences of imbalance. Because it is mandatory to aim for dynamic balancing.

When an imbalanced body is rotated, it generates mechanical vibrations and stresses in the rotor itself, in the bearings and in the entire structure of the machine.

The extent of the effects essentially depends on the service speed, the masses and the stiffness and damping of the parts involved (the rotor, the load-bearing structures and the foundations).

The most harmful and/or most annoying effects of the vibrations produced by imbalances are:

1. wear of bearings, pins, couplings, gears, etc.;
2. failures caused by alternating stresses in the pedestals, supports, slabs and foundations;
3. reduction of the mechanical efficiency of the machine and of its useful life;
4. deterioration of the quality of the material produced by the machine;
5. consumption of energy necessary to power the vibrations of the various parts associated with the rotor;
6. transmission of the vibrations to the other parts of the machine and also, via the platforms, to other machines of the plant, with possible particularly harmful resonance phenomena deriving therefrom;
7. disturbances of various kinds caused to people and the environment, like all mechanical vibrations, however generated

How to Measure and Correct Imbalance for Dynamic Balancing

The strict basis of imbalance measurement and compensation is specified in DIN ISO 1940-1 (previously called VDI guideline 2060). The accuracy of a balance is specified with the balance quality “G” (previously called Q).

That said, there are two types of approach depending on the complexity of the objects and/or the machine to be controlled and/or the precision to be obtained:

1. Static balancing which is performed on systems at rest and without the use of particular measuring equipment but simply checking, after having rotated the rotor around its axis, the condition of equilibrium in different points of the rotor
2. Dynamic balancing which is performed on rotating systems. When speaking of complex machines and wanting to monitor the behavior of the vibrations generated during operation, force gauges (accelerometers or similar) are used, suitably placed in the complex, slaved to control monitors interfaced to the electrical panel of the machine. When speaking of individual objects, a specific machine called a “balancing machine” or “balancing machine” is used with which, after having set the rotor in rotation with an appropriate speed, one intervenes promptly by adding or removing material according to the indications provided by the measure.

Top 10 Expert Recommendations to Maintain Dynamic Balance

The cycloidal reducers used in the field of centrifugal separation by decantation, due to both their geometry and their own weight (in the heaviest sizes it can even exceed 500 kg) need to be subjected to accurate and rigorous dynamic balancing checks for two basic reasons:

1. The entire reducer rotates at the same speed as the decanter drum which, to generate the centrifugal force field suitable for the separation of the fluid to be treated into the various phases (typically liquid-solid) is rotated at speeds ranging from 2000 g/1 for large sizes up to 8000 g/1 for smaller sizes.
2. For constructive reasons, the reducer is often mounted cantilevered on one side of the decanter supports and subjected to the pull of the movement belts of all the decanter.

It is easy to understand that if the balancing operation were not present or carried out in part, all the dynamics of the machine would have serious repercussions for its correct use.

To conclude, below is a short list of recommendations to keep in mind when approaching the problem:

1. Accurately determine the required balancing class (tolerance).
2. Once the precision class required by the mechanism has been established by the designer, obtaining greater precision during balancing is useless and uneconomical. The process itself is expensive.
3. Determine if the rotor is rigid or flexible.
4. If the rotor is stiff, choose the two most convenient correction planes and the lowest balancing speed compatible with the desired accuracy.
5. If the rotor is flexible, choose the two or more most convenient correction planes to reduce any bending produced by imbalance.
6. If the rotor is flexible, consider using one of the simplified balancing methods before resorting to modal balancing.
7. If the rotor is severely imbalanced, reduce the static imbalance first, at low speed.
8. Whenever possible, finish balancing with the rotor mounted in actual service conditions.
9. Use a balancing machine with adequate sensitivity, balancing speed, drive power and safety and protection devices.
10. Feel free to contact the machine manufacturer’s design office: a serious manufacturer maintains a mutually beneficial and free collaboration relationship with customers.

Want to optimize your machinery’s performance? Contact our experts today to learn more about dynamic balancing solutions.