分类归档： Industry News

Slewing bearing is one of the important parts of many modern machinery and equipment. It is called “joint of machine”. Many people are familiar with various parameters of slewing bearing, including clearance, inner and outer diameter, friction coefficient, etc. Many of my friends don’t know the module of supporting gear, so let’s follow the editor today to understand it.

 

1. what is the slewing ring gear module

 

The length of the arc (gear)/straight line (rack) occupied by a single gear tooth in the indexing circle (gear)/or line (rack), its length is π * m, and m is the modulus.

 

What does the module of the slewing ring represent: The module of the slewing ring represents the product of the tooth pitch and the number of teeth of the slewing ring gear, which is the circumference of the index circle. The gear modulus of the slewing ring determines the size of the tooth. The gear modulus is a basic parameter for the calculation of the gear size. The symbol is “m”. Gear cutters can be standardized, so that the standard modulus of gears can be standardized for mass production. Facilitate the replacement of later accessories. In the same way, “modulus” refers to the ratio of the pitch t between the tooth profiles of two adjacent gear teeth on the same side and the circumference ratio π (m=t/π), in millimeters.

 

If the number of teeth of the slewing ring gear is constant, the larger the gear modulus, the larger the radial dimension of the gear. The teeth of a gear with a large modulus are thick, and for two gears with the same number of teeth, the outer circle of the gear with a large modulus is larger. Therefore, the modulus of the gear in a watch is very small, and the modulus of the flywheel and transmission gear on the mechanical punching machine is large. The modulus of the two meshing gears must be the same. Modulus is the basic parameter of gear design, and it is used in many calculations of gear design.

 

 

2. Reasonable selection of gear modulus

 

When designing a gear, one of the important parameters is this modulus. The gnawing of the gear will produce gnawing pulsation. The main reason is that it has a great relationship with the elastic deformation of the gear teeth. It is a basic part of the gear design. Parameter-gear modulus, if it is a relatively large modulus (that is, a gear with a relatively large size), it will also have a relatively large load-bearing capacity. The modulus parameter is inversely proportional to the degree of bending of the gear teeth. The increase of the modulus means that the rigidity of the gear teeth is improved, so that the elastic deformation of the gear teeth will not be great when the gnawing transmission is carried out, which greatly reduces the impact force formed by the gear teeth, thereby achieving The purpose is always greatly reduced. Therefore, from this point of view, the modulus should be increased appropriately, but the error generated when machining gears is also related to the modulus. If the modulus is increased, the tooth profile and pitch will also be increased. At this time, the error of gnawing noise will also increase accordingly, so the choice of modulus should be determined according to the specific situation.

 

In the case of keeping the modulus unchanged, the diameter of the gear is proportional to the number of teeth, so the change of the number of teeth will also change the bending amount and elastic stiffness of the gear teeth: the strength of the noise generated by the sound source is not only related to the energy of the vibration source It is related to the size of the radiation area. If the radiation area is increased, the radiation power will also increase. Increasing the diameter of the gear will increase the noise radiation area, which will greatly affect the gear. Effective noise control. Therefore, in the relevant design, within the permissible range of ensuring the strength of the gear, the number of teeth and the small modulus should be used as much as possible, and the reasonable selection of materials and heat treatment methods can be combined to promote the improvement of the strength of the gear teeth, thereby Reduce the gear tooth diameter to achieve the purpose of reducing gear noise.

 

The above is the relevant introduction about the slewing ring gear module. In the slewing ring selection process, the first two sets of data listed in the national standard parameters of the slewing ring module should be selected first, which is more important for the adaptation of the bearing and the replacement of accessories. Convenient, but non-standard gears with customized bearing module requirements for bearings used in special machines are not within the above constraints.

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.

After the bearing is installed, in order to ensure the smooth operation of the bearing, the inspection work before the bearing operation should be paid attention to.

For small machines, you can directly rotate the bearing by hand to see if it can run smoothly. In daily inspection operations, common poor operation phenomena mainly include: poor operation due to foreign objects, scars and indentations; poor operation due to improper installation; large installation errors due to too small clearance, etc. The reason is that the torque is too large, resulting in poor operation of the bearing, etc. If no abnormality is found after careful inspection, the bearing can be used for the next step of power operation.

For large machinery, manual rotation is not possible, but inertial operation can be carried out by stopping the power in time after starting without load, and then carefully observing the vibration and noise of the bearing and the actual contact of each rotating part to confirm that there is no After the abnormality, the next power rotation stage can be carried out.

Power rotation, this stage generally starts from the no-load low-speed stage and gradually increases to the rated operating speed. During the trial operation stage, the focus should be on checking: whether there is abnormal sound in the bearing, whether there is lubricant leakage, and whether the bearing has a large temperature rise change, etc. If an abnormality occurs during the trial operation of the bearing, the bearing should be carefully inspected even if the operation is stopped, and the bearing should be disassembled and inspected if necessary.

The temperature rise of the bearing can usually be known by inspecting the bearing housing, but it is also possible to directly inspect the temperature of the outer ring of the bearing with the aid of the oil filling hole, so that the inspection result obtained will be more accurate. The bearing temperature of mining machinery generally rises gradually from the beginning of the bearing operation, and the bearing temperature usually tends to stabilize after rising to a certain temperature. If the bearing is installed improperly, it may cause the bearing temperature to rise sharply and produce abnormal temperature rise. In addition, excessive bearing lubricant, too small internal free gap, severe wear of the ball, high-speed rotation, etc., may also cause a transitional temperature rise of the bearing.

Slewing bearings are important parts in many modern machinery and equipment, because their performance is more unique than other mechanical parts, including significant advantages in anti-corrosion performance. However, if the slewing bearing is not produced strictly in accordance with the cleaning and anti-rust regulations and the requirements of oil seal anti-rust packaging, the bearing parts in the processing process and the finished bearing products after assembly shall be treated with anti-rust; or the anti-rust used in production The quality of rust lubricating oil, cleaning kerosene and other products cannot meet the requirements of the process technology, and the use of inferior anti-rust lubricating oil will cause the bearing to rust. So what can be done to prevent it from rusting? Today, the editor will share with you several ways to prevent the rust of turntable bearings.

One. Surface cleaning method

Cleaning must be based on the nature of the surface of the anti-rust material and the prevailing conditions, and an appropriate method must be selected. Generally, there are solvent cleaning method, chemical treatment cleaning method and mechanical cleaning method. When the surface is dry and cleaned, it can be dried with filtered dry compressed air, or dried with a dryer at 120~170℃, or dried with clean gauze.

Second, the method of coating anti-rust oil

1. Brushing method

This method is suitable for slewing bearings or special-shaped bearings that are not suitable for immersion or spraying. When brushing, it is necessary to pay attention not to produce anti-rust oil accumulation, and of course to prevent leakage.
Slewing ring

2, spray method

Some large slewing bearings cannot be oiled by immersion method, generally use about 0.7Mpa pressure filtered compressed air to spray in clean air. The spray method is suitable for solvent-diluted anti-rust oil or thin-layer anti-rust oil, but complete fire protection and labor protection measures must be adopted. This method is mostly used for rust prevention of some large slewing bearings.

3, soaking method

The slewing bearing is soaked in anti-rust grease, and a thick layer of anti-rust grease can be adhered to its surface. The thickness of the oil film can be achieved by controlling the temperature or viscosity of the anti-rust grease, and this layer of grease can effectively isolate it from The contact of air achieves the effect of rust prevention.

The above are several ways to prevent rusty slewing bearings. I hope everyone can help after reading them. In addition, when we use the bearing, do not directly touch the bearing with your hands, because when sweat contacts the bearing, a layer of sweat film will be formed on the bearing surface. The sweat film will cause electrochemical effects on the bearing and corrode the bearing. Therefore, use special tools such as special gloves or finger cots to pick up the bearing, and do not touch it directly with your hands.