Causes and preventive measures of shaking during operation of slewing bearing
Slewing bearing, also known as slewing bearing and slewing bearing, is one of the important components of modern construction machinery slewing devices, such as excavators, cranes, pile drivers, graders, road rollers, dynamic compactors, roadheaders, tower cranes, etc.
Slewing bearings will be used in all cases. Due to the large load operation and the harsh working environment, the operation is not smooth (jitter) and the noise exceeds the standard (abnormal noise). So, what is the reason for the jitter when the slewing bearing is running?
Table of Contents
1.The reason for the jitter of the slewing bearing during operation.
1. Internal machining accuracy of slewing bearing
The machining accuracy of the steel ball inside the slewing bearing and the machining accuracy of the inner raceway are not high, or there are quality defects and the lack of lubricating oil in the raceway. When the slewing bearing is defective, sometimes the frequency of failure can be reduced by replacing the steel ball.
2. The machining of gears is not precise enough
The gear accuracy grade of the slewing bearing should be between 7 and 11, which determines the stability of the slewing bearing transmission, the uniformity of the load distribution and the transmission accuracy.
The higher the gear precision, the denser the contact spots of the meshing tooth surface, so that the noise value is reduced and the operation stability is improved.
3. Welding defects of upper and lower supports
If the welding quality is not up to standard, it is necessary to repair and repair the weld defects. During repair welding, it will not only generate new welding stress, but also have a great impact on the flatness of the machined mounting surface.
At the same time, the current generated by welding will also cause certain damage to the internal rolling elements and raceways when passing through the slewing bearing. damage.
In addition, if the assembly error generated in the manufacturing and assembly, the threading of the pin shaft and the pre-tightening of the bolts in the field installation do not meet the specified requirements, abnormal noise or vibration will also occur.
4. Quality problems of gears and starting motors
Due to the long working time of the gear under load, small pieces of metal or strip-shaped metal iron filings will appear near the pitch line of the tooth surface, resulting in pitting or gnawing.
The pitting corrosion of the tooth surface continues to expand with the increase of working time, so that the meshing tooth profile is damaged, the noise and impact during rotation increase, and the metal particles impacted 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 produce shock jitter, and the meshing process between the drive wheel and the support is unstable, which also increases the frequency of jitter and the decibel of abnormal noise.
2.Preventive measures for slewing bearing jitter
1. Installation and operation
High-strength bolts should be selected for the installation of slewing bearings, and the bolts and nuts should meet the requirements of GB3098.1 and GB3098.2 standards.
It is forbidden to use spring washers. Before the mounting bolts are tightened, the meshing adjustment (backlash) of the large and small gears must be carried out to ensure that the meshing of the slewing bearing and the pinion meets the requirements.
Tighten the mounting bolts at 180°, the mounting plane must be clean and flat, and there must be no burrs, iron filings and other debris, and the plane must meet the following requirements: the slewing bearing often has broken teeth during operation, so it is also
The influence of wind on the slewing bearing should be taken into account. If the jib cannot rotate freely with the wind after the operation exceeds the specified wind force or stops the operation, it may damage the gear meshing with the bearing or the slewing bearing, and a serious safety accident will occur.
Therefore, detailed inspection should be done during installation and operation.
2. Fastening bolts
The connecting bolts of the slewing bearing and the upper and lower supports are not only subjected to the pre-tightening force, but also subjected to the axial pulsating load, which will cause the bolts to be elongated or the connecting surface to deform, making the bolts loose.
If the loosening pre-tightening force of the bolt connection fails to meet the requirements, the axial clearance will increase, the rolling elements will be rotated by a large overturning moment, and the edge of the raceway will be subjected to huge contact stress, which will cause the edge of the raceway to be damaged.
Therefore, the tightening of the slewing bearing bolts must be checked regularly to make it reach the specified pre-tightening force, which is generally 400-500 N.m.
3. Internal lubrication of slewing bearing
In daily use, each part should be lubricated according to the lubricant, lubrication method and lubrication cycle regulations in time and on time according to the instruction manual. The corresponding ball slewing bearing is generally refilled every 100 hours of operation, and the roller slewing bearing is filled every 50 hours.
For special working environments with a lot of dust, high humidity and high temperature difference, the lubrication cycle should be shortened.
The raceway must be filled with each lubrication until the lubricating oil seeps out, and the slewing bearing needs to be slowly rotated to make the grease evenly filled while filling.
By adding lubricating oil for maintenance, the friction between the gear pairs can be reduced, the wear speed of the gear ring can be slowed down, and the formed oil film can also act as a shock absorber to eliminate 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 surfaces. Thereby reducing the friction noise of the operation and increasing the service life of the bearing.
