Dynamic Balancing:

Dynamic Balancing is a method used to eliminate vibration created by unequal centrifugal forces introduced during manufacture. These forces are usually a result of density irregularities in the parent material and/or machining eccentricities and can in many cases be equivalent to several times the rotor's weight at rotational speed.

Why Dynamic Balance?
Imbalance greatly reduces bearing life, and in the case of high speed rotors can compromise operational quality

1.What is a dynamic balancing machine?

Dynamic balancing machines measure the size (magnitude) and angle (direction) of vibration.

There is no limit to the number of products that rotate. Using cars as an example, they consist of tires, shafts, flywheels, gears, and crankshafts, to name just a few. In our homes, we have a variety of equipment, including fans, vacuum cleaners, refrigerator compressors, video heads, DVD and CD systems, and computer hard drives. It would be impossible to count all the types of rotating objects and how many exist.

When these rotating parts or materials rotate, they generate centrifugal forces. Normally, the sum of these centrifugal forces equals zero, however, if they do not, that rotating object will generate vibration and noise. Dynamic balancing machines measure the amount and angle of this vibration

2. What does "balancing" a rotor mean?  

It means to reduce the amount of unbalance.

Unbalance refers to the center-of-gravity of the rotor being out of alignment with its center-of-rotation (eccentricity). If unbalanced, centrifugal forces will generate vibration and noise during rotation. The world in which we live is overflowing with rotating objects. In most homes, looking around many rooms you can find air conditioners, forced air heaters, or fans, and sometimes even dehumidifiers, humidifiers, or a video, CD or DVD player under the television. In the bathroom you can find washing machine, drier, electric razor, n the kitchen ventilation fans, refrigerators, microwave ovens and in a different room a computer and printer. All of these consumer electronic products include internal rotating parts (motors). Outside the home you see automobiles, which are a dense concentration of multiple rotating objects, as are trains, ships, and aircraft. In manufacturing plants, you can find all types of rotating machinery on a production line. At power plants there are rotating turbines and generators. If all these items were not balanced properly, our lives would undoubtedly be extremely noisy. Furthermore, generating vibration and noise consumes energy, meaning energy is being wasted, which is counterproductive to current efforts to save energy. Not only does vibration waste energy, it causes bearings to wear more quickly and shortens the operating life of products. The process of reducing the amount of unbalance in rotating items like these is called balancing.
 

Unbalance Present With Static Static Unbalance:

When a rotor is placed on smooth rails, the heavy side will turn to face downward. The unbalance experienced when an object is static (not moving) is called static unbalance. Static unbalance can be corrected using only one location (one-plane correction for one-plane unbalance).


Dynamic Balancing.pdf