Selection of High-Speed Balancing Test Bench

Posted on 2017-09-15
The balancing machine is a device for measuring the size and position to rotating objects. When any of the rotors rotates around its axis, the centrifugal force is generated due to the uneven distribution of the mass distribution relative to the axis. This unbalanced centrifugal force acts on the rotor bearings to cause vibration, noise and accelerated bearing wear, which seriously affects the performance and longevity of the product. Rotary parts, such as machine tool spindle, motor rotor, and internal combustion engine crankshaft, steam turbine rotor and watch wheel, in the manufacturing process, it is necessary to measure the rotor unbalance by the balancing machine and correct the rotor according to the measurement result to improve the rotor mass distribution The vibration of the journal or the force acting on the bearing is reduced to a prescribed range in order to ensure the smooth and normal operation of the rotating object. The main performance indicators of the dynamic balancing machine are expressed by two comprehensive indicators of minimum reachable residual unbalance and unbalanced reduction rate. The former is the minimum value of the balance imbalance to achieve the remaining unbalance of the rotor. It is an indicator that measure the highest balance machine ability. The latter is the ratio of the unbalanced amount to the initial unbalance after correction. It is an indicator of equilibrium efficiency, generally expressed as a percentage.


 
The classification of balancing machines
The classification of the dynamic balancing machine can basically be divided from the principle and the application this two aspects:
1, from the measurement principle of division, it can be divided into hard bearing balancing machine and soft bearing dynamic balancing machine.
(1) The hard support balancing machine has the characteristic that the balance speed is lower than the natural frequency of the rotor support system, which can be balanced at low speed, easy to operate and good in safety performance.
(2) The soft support dynamic balancing machine has the balance speed higher than the natural frequency of the rotor support system. The balancing machine is influenced by the external vibration signal, and the measurement precision is high, which is suitable for the mass production.
2, from the application of the division it can be divided into horizontal and vertical balancing machines, general and special dynamic balancing machine categories.
(1) Horizontal balancing machines are balancers that are horizontally equilibrated on the balancing machine by rotating as the axis of the rotor. Generally, a rotor has a rotary shaft or a convenient assembly shaft, such as shafts, impellers, rollers, electric rotors, etc. Horizontal balancing machines. Vertical balancing machine is the balance of the rotor rotation axis in the balance machine was in the vertical state of the balance machine, generally, no rotary axis of the disc-shaped work piece, such as pump impeller, flywheel, grinding wheel, chuck, brake, are applicable to the legislation type balancing machine.
(2) General dynamic balancing machine is in the specified rotor weight and speed range, can balance a variety of rotor balancing machine. Special dynamic balancing machine is designed for a certain type of rotor designed and manufactured balancing machine.


 

Application of Dynamic Balance in Motor Manufacturing
1, the importance of motor balancing test
In the ideal case, even when the motor rotor rotates and does not rotate, the pressure generated by the bearing is the same, but because the motor rotor material is not uniform or rough defects, processing and assembly of the error, even when designed to have asymmetric geometric shape and other factors, making the motor rotor in the rotation, the tiny particles on each of the centrifugal inertia force cannot offset each other, the centrifugal inertial force through the bearing to the mechanical and its basis, causing vibration, resulting in noise, Bearing wear, shorten the mechanical life, serious can cause damage to the accident. Therefore, in order to ensure reliable and getting higher and higher.
 
2, the limitations of the existing dynamic balance test
Our existing dynamic balancing equipment is mainly low-speed light equipment, can test the weight of not more than 5T, the maximum speed of not more than 1250rpm. With the development of large-scale civilian motor, new products will be towards the high-speed, high-power direction of development, the existing equipment and process level cannot meet the requirements to enhance the manufacturing level, high-speed dynamic balancing test technology will become to enhance the manufacturing level an important means and development trend. Motor rotor weight of nearly 10T, speed requirements to 360Orpm, much beyond the limits of the existing dynamic balancing machine.


 
Feasibility Analysis of high - speed Heavy - duty Dynamic Balancing Motor Test
1, rated motor speed 2988rpm, over speed test in 3600rpm, the first order critical speed 3580rpm. When the maximum speed of the motor is less than 0.3 times the first order critical speed of the rotor, it is regarded as a constant state rotor. The dynamic balance can be used to replace the dynamic balance of the rotor at maximum speed, and higher than 0.3 times the first order critical Rotor above the speed as a flexible rotor, the dynamic balance must be used under the speed of the dynamic balance.
2, the rotor in the high-speed dynamic balancing machine to the speed of the motor speed test to do the rotor dynamic balance, the first low speed 600rpm to do the rotor dynamic balance, the balance of the rotor to achieve the balance of the quality of G0.4 below, and then the speed of 1500rpm at high speed Dynamic balancing machine to do the balance until the balance of quality in G0.4 and below. The rotor balance speed is set to 3600rpm, real-time measurement of rotor unbalance, if the amount of imbalance in the technical requirements within the qualified, if exceeded, then the rotor at 1500rpm dynamic balance speed again to reduce the imbalance, and then measured at 3600rpm speed, repeated measurements until qualified.
3, the rotor with the whole machine balance technology for processing, due to machine vibration is often caused by many reasons, not a single imbalance problem, increasing the technical difficulty of balancing work; the other hand, it may also be that the main vibration is mainly caused by other reasons. Imbalance is not a major problem, but trying to use a balanced way to reduce vibration, which makes the whole vibration problem is not easy to solve, the technical requirements of the staff, the work efficiency is low.
4, so in the low-speed dynamic balance cannot meet the requirements and the impact of the whole motor balance in the case of more factors, the use of motor speed in the case of rotor dynamic balance will improve the motor rotor dynamic balance quality, excluding the rotor balance quality is not satisfied The requirements of the machine vibration caused by failure. In addition to ensure the accuracy of the test, equipped with a constant temperature, constant humidity control room, at the same time by the balance of protective cover and other safety equipment safety standards supporting protective equipment.
 
Conclusions
In summary, the high-speed dynamic balancing machine will significantly improve the motor dynamic balance quality, can solve the motor rotor quality caused by the motor vibration instability, exceeding the problem; at the same time significantly improve the motor rotor balance detection efficiency, and the actual operation.