Slewing bearing can also be called turntable bearing and rotating bearing. It is one of the important parts of modern construction machinery slewing devices, such as excavators, cranes, pile drivers, graders, road rollers, dynamic compactors, roadheaders, tower cranes, etc. Slewing bearings are always used. Due to the large load during operation and the harsh working environment, the operation is not smooth (jitter) and excessive noise (abnormal noise) failure occurs. So, what is the cause of jitter when the slewing ring is running? How to prevent it? Next, follow the editor to understand it.
Reasons for the vibration of the slewing bearing during work
1. The internal machining accuracy of the slewing ring
The machining accuracy of the steel balls inside the slewing ring and the machining accuracy of the internal raceway are not high, or there are quality defects and the lack of lubricating oil in the raceway. The roller collides with the spacer, which directly affects the smoothness of the slewing ring operation and the level of noise, so check When the slewing bearing is defective, sometimes the frequency of failure is reduced by replacing the steel ball.
2. The gear processing is not precise enough
The gear accuracy grade of the slewing ring should be between 7 and 11, which determines the stability of the slewing ring transmission, the uniformity of load distribution and the transmission accuracy. The higher the gear accuracy, the denser the contact spots on the meshing tooth surface, so that the noise value is reduced and the smooth operation is improved.
3. Welding defects of upper and lower supports
If the welding quality is not up to standard, the weld defects need to be repaired and repaired. During repair welding, not only new welding stress will be generated, but also the flatness of the machined mounting surface will be greatly affected. At the same time, the current generated by welding will also cause a certain amount of internal rolling elements and raceways when passing through the slewing ring. damage. In addition, if the assembly errors generated in the manufacturing and assembly, the pin and bolt pre-tightening in the on-site installation do not meet the specified requirements, abnormal noise or jitter will also occur.
4. Quality problems of gears and starting motors
Because the gear has been loaded for a long time, small pieces of metal or strip-shaped metal iron filings will fall off near the pitch line of the tooth surface, resulting in pitting or tooth gnawing. The pitting corrosion of the tooth surface continues to expand with the increase of working time, so that the meshed tooth profile is damaged, the noise and impact during rotation increase, and the metal particles that impact repeatedly accelerate the wear of the tooth surface, forming a vicious circle. In addition, the manufacturing and assembly of the starter motor in the slewing mechanism has its own defects, which produces shock jitter, and the meshing process between the drive wheel and the support is unstable, which also increases the jitter frequency and the decibel of abnormal noise.
Preventive measures against shaking of slewing ring
1. Installation and operation
High-strength bolts should be used for the installation of the slewing bearing. The bolts and nuts should meet the requirements of GB3098.1 and GB3098.2. Spring washers are prohibited. Before the installation bolts are tightened, the meshing adjustment of the large and small gears (backlash) must be carried out to ensure that the meshing of the slewing ring and the pinion meets the requirements. The mounting bolts should be tightened at 180°. The mounting plane must be clean and flat, free of burrs, iron filings and other debris. The plane must meet the following requirements: The slewing bearing often has broken teeth during operation, so it is also in operation. Consider the influence of wind on the slewing support. If the boom cannot rotate freely with the wind after the specified wind power is exceeded or the operation is stopped, the gear or slewing bearing meshing with the support may be damaged, and serious safety accidents may occur. Therefore, detailed inspections should be done during installation and operation.
2, tightening bolts
The connecting bolts of the slewing bearing and the upper and lower supports are subjected to axial pulsating load in addition to the pre-tightening force, which will cause the bolts to elongate or the connecting surface to deform, which makes the bolts loose. After the bolt connection is loosened and the pre-tightening force fails to meet the requirements, the axial clearance increases, the rolling elements are rotated by a large overturning moment, and the raceway edge is subjected to huge contact stress, causing damage to the raceway edge. Therefore, the tightening of the slewing bearing bolts must be checked regularly to make it reach the specified pre-tightening force, which is generally 400-500N.m.
3, internal lubrication of the slewing ring
In daily use, each part should be lubricated according to the lubricant, lubrication method, and lubrication cycle in accordance with the instructions in the operation manual in time and on time. Corresponding ball slewing bearings are generally filled once every 100 hours of operation, and roller slewing bearings are filled once every 50 hours. The lubrication cycle should be shortened for the special working environment with a lot of dust, high humidity and high temperature difference. Each lubrication must fill the raceway until the lubricating oil seeps out. While filling, the slewing ring needs to be slowly rotated to make the grease evenly filled. By adding lubricating oil for maintenance, the friction between the gear pairs can be reduced, and the wear rate of the gear ring can be slowed down. The oil film formed can also act as a shock absorbing ring, eliminating part of the vibration energy generated during operation. In addition, the lubricating oil film can also lubricate and clean the friction surfaces well, prevent rust, and eliminate the influence of iron filings on the friction surface. Thereby reducing the friction noise of operation and increasing the service life of the support.
The above is the analysis and explanation of the reasons and preventive measures for the shaking of the slewing ring during operation. I hope it will be helpful after reading it. Luoyang Hengguan Bearing is a slewing ring/slewing bearing comprehensive entity enterprise integrating design, research and development, production, sales and service. Mainly engaged in a variety of high-precision slewing bearings, large thrust ball bearings, non-standard special-shaped bearings and other products, and also provide customers with customized exclusive bearing products. Everyone is welcome to call for detailed consultation.