Dynamic balancing machine measurement principle

A balancing machine is a machine that measures the size and position of the unbalance of a rotating object (rotor).

When any rotor rotates around its axis, centrifugal force is generated due to the uneven distribution of mass relative to the axis. This unbalanced centrifugal force acts on the rotor bearing, causing vibration, noise and accelerated bearing wear, which seriously affects the performance and life of the product. Rotating parts such as motor rotors, machine tool spindles, internal combustion engine crankshafts, turbine rotors, gyro rotors and clock balance wheels need to be balanced during the manufacturing process to operate smoothly and normally.

Correcting the rotor's unbalance according to the data measured by the balancing machine can improve the mass distribution of the rotor relative to the axis, so that the vibration generated when the rotor rotates or the vibration force acting on the bearing is reduced to within the allowable range. Therefore, the balancing machine is an indispensable equipment for reducing vibration, improving performance and improving quality.

Usually, the balancing of the rotor includes two steps: measuring and correcting the unbalance. The balancing machine is mainly used for measuring the unbalance, while the correction of the unbalance is often done with the help of other auxiliary equipment such as drilling machines, milling machines and spot welding machines, or by manual methods. Some balancing machines have made the correction device a part of the balancing machine.

Gravity balancing machine and centrifugal balancing machine are two typical types of balancing machines. Gravity balancing machine is generally called static balancing machine. It relies on the gravity of the rotor itself to measure static imbalance.

If the rotor on two horizontal guide rails has an unbalance, its gravity torque on the axis causes the rotor to roll on the guide rail until the unbalance is at the lowest position and then it stops. The

balanced rotor is placed on a support supported by a hydrostatic bearing, and a reflector is embedded under the support. When the rotor does not have an unbalance, the light beam emitted by the light source is reflected by the reflector and projected on the polar coordinate origin of the unbalance indicator. If the rotor has an unbalance, the rotor support tilts under the gravity torque of the unbalance, and the reflector under the support also tilts and deflects the reflected light beam, so that the light spot projected on the polar coordinate indicator leaves the origin. According to the coordinate position of the deflected light spot, the size and position of the unbalance can be obtained.

Gravity balancing machine is only suitable for some disc-shaped parts with low balancing requirements. For rotors with high balancing requirements, centrifugal single-plane or double-plane balancing machines are generally used.

Centrifugal balancing machines measure imbalance based on the support vibration caused by the rotor imbalance or the vibration force acting on the support when the rotor is rotating. It can be divided into single-plane balancing machines and double-plane balancing machines according to the number of correction planes. Single-plane balancing machines can only measure imbalance (static imbalance) on one plane. Although it measures when the rotor is rotating, it still belongs to static balancing machines. Double-plane balancing machines can measure dynamic imbalance, and can also measure static imbalance and even imbalance separately. They are generally called dynamic balancing machines. Centrifugal balancing

machines can be divided into soft-bearing balancing machines and hard-bearing balancing machines according to different support characteristics. The balancing speed is higher than the natural frequency of the rotor-support system. It is called a soft-bearing balancing machine. The support stiffness of this balancing machine is small, and the signal detected by the sensor is proportional to the vibration displacement of the support. The balancing speed is lower than the natural frequency of the rotor-support system. It is called a hard-bearing balancing machine. The support stiffness of this balancing machine is large, and the signal detected by the sensor is proportional to the vibration force of the support.

The main performance of the balancing machine is expressed by two comprehensive indicators: the minimum achievable residual unbalance and the unbalance reduction rate. The former is the minimum value of the residual unbalance that the balancing machine can make the rotor reach, which is an indicator of the highest balancing ability of the balancing machine; the latter is the ratio of the unbalance reduced after one correction to the initial unbalance, which is an indicator of the balancing efficiency, generally expressed as a percentage.

In modern machinery, due to the wide application of flexible rotors, people have developed flexible rotor balancing machines. This type of balancing machine must be able to perform stepless speed regulation within the working speed range of the rotor; in addition to measuring the vibration or vibration force of the support, it can also measure the flexural deformation of the rotor. Flexible rotor balancing machines are sometimes installed in vacuum protection rooms to suit the balancing of rotors such as steam turbines. They are equipped with large auxiliary equipment such as vacuum systems, lubrication systems, lubricating oil degassing systems, and computer systems for data processing.

According to the needs of mass production, automatic balancing machines that can automatically complete balance measurement and balance correction for specific rotors, as well as balancing automatic lines, are now widely equipped in industrial sectors such as automobile manufacturing and motor manufacturing. (end)