Principle of Dynamic Balance -- Why do dynamic balance
Principle of Dynamic Balance -- Why do dynamic balance
Commonly used machinery contains a large number of rotating motion parts, such as a variety of transmission shaft, spindle, motor and turbine rotor, collectively known as the rotary body. Under ideal conditions, the rotary body rotates and does not rotate, the pressure on the bearing is the same, such a rotary body is a balanced rotary body. But engineering of all kinds of solid of revolution, due to uneven material or casting defects, processing and assembly of error, and even design with asymmetric geometry, and other factors, makes the solid of revolution in rotates, the centrifugal force produced by each tiny particles on the cannot cancel each other out, centrifugal force by bearing role to the machine and its basis, causing vibration, Produces noise, accelerates bearing wear, shortens mechanical life, and can cause destructive accidents when serious. To this end, the rotor must be balanced to achieve the allowed balance accuracy level, or the resulting mechanical vibration degree is reduced within the allowed range.
1, definition: the difference between rotor dynamic balance and static balance
1) Static balance
The balance is corrected on a correction surface of the rotor, and the residual unbalance after correction is to ensure that the rotor is in the prescribed range of allowable unbalance when it is static, which is also known as the static balance.
The balance is corrected on the two correction surfaces of the rotor at the same time, and the residual unbalance after correction is to ensure that the rotor is in the specified range of allowable unbalance when it is dynamic, which is also known as double-sided balance.
2, rotor balance selection and determination
How to choose the balance mode of the rotor is a key problem. Its selection has such a principle: as long as it meets the needs of the rotor balance after the use of the premise, can do static balance, do not do dynamic balance, can do dynamic balance, do not do static and dynamic balance. The reason is simple, static balance is easier to do than dynamic balance, save time, effort, and cost.
Modern dynamic balancing technology was developed with the advent of the steam engine at the beginning of the century. With the rapid development of industrial production, rotating machinery is gradually developing in the direction of precision, large-scale and high-speed, which makes the problem of mechanical vibration more and more prominent. The violent vibration of machinery will bring a series of harm to the machine itself and its surroundings. Although there are various causes of vibration, it is generally believed that "unbalanced force" is the main cause. According to statistics, about 50% of mechanical vibration is caused by unbalanced force. Therefore, it is necessary to change the mass of the moving part of the rotating machinery to reduce the unbalance force, that is, to balance the rotor.
There are many factors that cause the rotor unbalance, such as the uneven material of the rotor, the unbalance of the coupling, the asymmetry of the keyway, the rotor processing error, the corrosion, wear and thermal deformation of the rotor in the process of movement. The unbalance caused by these factors is generally random and cannot be calculated. It needs to be measured and corrected by gravity test (static balance) and rotation test (dynamic balance) to reduce it to the allowable range.
