①The body of rotation is in an unbalanced state when the center of mass of the rotating body is eccentric from the center of rotation (axis) relative to the center of the axis presented in the design or when an unbalanced mass exists. When the rotation speed of the rotating body increases, a larger unbalanced centrifugal force is generated due to mass eccentricity and the centrifugal force is transmitted to the bearing and supporting part, which becomes the cause of the vibration of the structure. Therefore, balancing refers to the operation that compensates the unbalance of the rotating body within the tolerance range.
② According to the definition of ISO, the mass distribution of the rotating body is investigated and based on the investigation, it refers to the control work ensuring that the kinetic energy that interacts with the vibration and bearing of the rotating body is within the limit at the frequency (rotational frequency) reacting to the operating speed.
When the center of the mass of the rotating body is eccentric from the center of rotation or when there is an unbalanced mass, the rotating body is in an unbalanced state and when the rotating speed of the rotating body increases, a larger unbalanced centrifugal force occurs, which causes vibration of the structure due to vibration and stress that is applied to the structure and bearing. Such vibration and stress of the rotating body cause the following problems.① Provides the cause of fatigue phenomenon about material of construction (structure).
② It afflicts the driver of the machinery and causes quality degradation.
③ It can roughen the surface of the structure.
④ It has direct correlation with the life expectancy of the machinery.
⑤ It not only decreases the quality of the processed products, but also brings severe abrasion to the bearing, axis, spindle, gears, etc.
⑥ It causes stress that is detrimental to structural support and may damage the structure.
⑦It brings inefficient loss of energy of the equipment and has influence on the adjacent equipment, which decreases the efficiency as well as the accuracy of the adjacent equipment.
In particular, the influence of the vibration due to unbalanced mass becomes more prominent when the diameter of the axis becomes narrower and then the rotation speed becomes higher. Therefore, the following results can be obtained by compensating the unbalanced mass that unify the center of gravity of the rotating body and center of geometric axis to decrease the vibration of the rotating body. The operation of compensating unbalance mass of the rotating body is called balancing.① Extension of life span for the rotating body and the structure.
② Improvement of the quality of products subjected to production.
③ Improvement of workability and productivity.
④ Prevention of an unnecessary loss of energy.
⑤ Improve the operator’s fatigue by preventing noise and vibration and improvement of working environment.
⑥ Improvement of the added value of products.
Due to the above effects, there are regulations on the rotating body of all products in industrial sites. It suggests that balancing is a very important process.
① Eccentricity occurring during the machining process and owing to the textural distribution of materials.
② Tolerance of the part assembling process.
③ Conditions of the assembling sites.
① Cause centrifugal force in the presence of unbalance when the specimen is rotated.
② Produce equipment to measure the quantity of motion that is generated with centrifugal force under the vibrating conditions.
③ Detect the mechanical vibration with electric signal by using the vibration element.
④ Convert an electric signal into a digital and read it on the computer PC CPU.
⑤ Program and calculate the measured signal data, and then display them on the monitor.
There are various causes of vibration for the rotational machinery. However, unbalance is the greatest part of them. Therefore, let’s take a look at the analysis table for importance by the causes of vibration created in Japan.1. Unbalance of a Rotor.
2. Poor bed or installation.
3. Unbalance in inertial force of a reciprocator.
4. Clearance or abrasion of the bearing section.
5. Automatic vibration due to friction.
6. Poor combination of gears.
7. Surging pulsation of air, water, etc.
8. Impact during the operation.
9. External vibration.
10. Deterioration of the bed.