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Bearing diagnostic management
In order to maintain the performance of the rolling bearing, it can maintain long-term use under good conditions. The bearing must be inspected and maintained. This kind of inspection and maintenance (see the attached bearing storage before the bearing is installed), it is very important to prevent failure in advance. Importantly, it is desirable to carry out regular inspections and maintenance according to the operating standards that are suitable for the operating conditions of the machine. The following methods are generally used: 3.1 Inspection in the operating state According to the rolling sound, vibration, temperature inspection of the bearing and the nature of the lubricant, the lubricant is checked. The time of supplement or replacement is judged. For details, see item 4: In-service inspection and troubleshooting. 3.2 Bearing inspection Fully observe the periodic inspection and replacement of the machine and remove the bearing. Check the condition of the raceway surface and whether it can be used again. For details, please refer to item 5: Inspection of the bearing.
Bearing inspection
Observe the bearings that have been removed by regular inspection and replacement of the machine, check the condition of the raceway surface and whether it is damaged or not. For details, please refer to item 5: Inspection of bearings.
4. During the operation check and the trouble check operation, the inspection items include the rolling noise, vibration, temperature, and lubrication status of the bearing. The details are as follows: When an abnormal state is found during operation, refer to Table 2-8 above.
4.1 Rolling sound of the bearing The sounder is used to check the size and sound quality of the rolling sound of the running bearing. Even if the bearing is slightly peeled off, abnormal sounds and irregular sounds will be emitted, which can be distinguished by the sounder.
4.2 Bearing vibration The vibration of the bearing is very sensitive to the damage of the bearing. For example, peeling, indentation, rust, crack, wear, etc. will be reflected in the vibration measurement of the bearing. Therefore, by using a special bearing vibration measuring device (frequency analyzer, etc.) The magnitude of the vibration can be measured, and the specific situation of the abnormality cannot be inferred by the frequency. The measured values vary depending on the conditions of use of the bearing or the mounting position of the sensor. Therefore, it is necessary to analyze and compare the measured values of each machine in advance to determine the judgment standard.
4.3 Bearing temperature The temperature of the bearing, generally the temperature outside the bearing can be inferred. If the oil hole can directly measure the bearing outer ring temperature, it is more suitable. Usually, the temperature of the bearing rises slowly as the operation starts, and reaches a steady state after 1-2 hours. The normal temperature of the bearing varies with the heat capacity, heat dissipation, speed and load of the machine. If the lubrication and installation parts are suitable, the bearing temperature will rise sharply and abnormal temperature will occur. At this time, it is necessary to stop the operation and take necessary precautions. Based on a large amount of test data, Table 4-1 lists the average value of the outer ring temperature when the bearings are working in various machines for reference. Since the temperature is affected by lubrication, speed, load, and environment, the values in the table only indicate the approximate temperature range. The thermal sensor can be used to detect the working temperature of the bearing at any time, and automatically alarm or stop the occurrence of the burning shaft accident when the temperature exceeds the specified value.
4.4.1 Effect of bearing lubrication Lubrication has an important influence on the fatigue life of rolling bearings and friction, wear, temperature rise, vibration, etc. Without normal lubrication, the bearings cannot work. Analysis of the cause of bearing damage indicates that about 40% of bearing damage is associated with poor lubrication. Therefore, good lubrication of the bearings is an effective measure to reduce bearing friction and wear. In addition, the lubrication of the bearing also has various functions such as heat dissipation, rust prevention, sealing, and shock relief. The effect of bearing lubrication can be briefly explained as follows: a. Form a gap between the two rolling surfaces or sliding surfaces that are in contact with each other. The oil film separates the two surfaces, reducing friction and wear on the contact surfaces. b. When using oil lubrication, especially when using circulating oil lubrication, oil mist lubrication and fuel injection lubrication, the lubricating oil can take away most of the friction heat inside the bearing and effectively dissipate heat. c. When grease lubrication is used, foreign matter such as dust can be prevented from entering the bearing and sealing. d. Lubricants have the effect of preventing metal corrosion. e. Extend the fatigue life of the bearing.
4.4.2 Comparison of grease lubrication and oil lubrication The lubrication methods of bearings are roughly classified into grease lubrication and oil lubrication. In order to fully utilize the function of the bearing, it is important to use a lubrication method depending on the purpose of use reduction and use. Table 4-2 shows the advantages and disadvantages of grease lubrication and oil lubrication.
4.4.3 Grease Lubricating Grease is a lubricant consisting of a base oil, a thickener and an additive. When selecting, you should choose a grease that is very suitable for the conditions of use of the bearing. Due to the different trademarks, there will be great differences in performance, so you must pay attention when choosing. Commonly used greases for bearings include calcium-based greases, sodium-based greases, calcium-sodium-based greases, lithium-based greases, aluminum-based greases, and molybdenum disulfide greases. The amount of grease filled in the bearing is preferably 1/2-1/3 of the internal space of the bearing. It should be reduced to 1/3 at high speed. Excessive grease will increase the temperature rise.
4. During the operation check and the trouble check operation, the inspection items include the rolling noise, vibration, temperature, and lubrication status of the bearing. The details are as follows: When an abnormal state is found during operation, refer to Table 2-8 above.
4.1 Rolling sound of the bearing The sounder is used to check the size and sound quality of the rolling sound of the running bearing. Even if the bearing is slightly peeled off, abnormal sounds and irregular sounds will be emitted, which can be distinguished by the sounder.
4.2 Bearing vibration The vibration of the bearing is very sensitive to the damage of the bearing. For example, peeling, indentation, rust, crack, wear, etc. will be reflected in the vibration measurement of the bearing. Therefore, by using a special bearing vibration measuring device (frequency analyzer, etc.) The magnitude of the vibration can be measured, and the specific situation of the abnormality cannot be inferred by the frequency. The measured values vary depending on the conditions of use of the bearing or the mounting position of the sensor. Therefore, it is necessary to analyze and compare the measured values of each machine in advance to determine the judgment standard.
4.3 Bearing temperature The temperature of the bearing, generally the temperature outside the bearing can be inferred. If the oil hole can directly measure the bearing outer ring temperature, it is more suitable. Usually, the temperature of the bearing rises slowly as the operation starts, and reaches a steady state after 1-2 hours. The normal temperature of the bearing varies with the heat capacity, heat dissipation, speed and load of the machine. If the lubrication and installation parts are suitable, the bearing temperature will rise sharply and abnormal temperature will occur. At this time, it is necessary to stop the operation and take necessary precautions. Based on a large amount of test data, Table 4-1 lists the average value of the outer ring temperature when the bearings are working in various machines for reference. Since the temperature is affected by lubrication, speed, load, and environment, the values in the table only indicate the approximate temperature range. The thermal sensor can be used to detect the working temperature of the bearing at any time, and automatically alarm or stop the occurrence of the burning shaft accident when the temperature exceeds the specified value.
4.4.1 Effect of bearing lubrication Lubrication has an important influence on the fatigue life of rolling bearings and friction, wear, temperature rise, vibration, etc. Without normal lubrication, the bearings cannot work. Analysis of the cause of bearing damage indicates that about 40% of bearing damage is associated with poor lubrication. Therefore, good lubrication of the bearings is an effective measure to reduce bearing friction and wear. In addition, the lubrication of the bearing also has various functions such as heat dissipation, rust prevention, sealing, and shock relief. The effect of bearing lubrication can be briefly explained as follows: a. Form a gap between the two rolling surfaces or sliding surfaces that are in contact with each other. The oil film separates the two surfaces, reducing friction and wear on the contact surfaces. b. When using oil lubrication, especially when using circulating oil lubrication, oil mist lubrication and fuel injection lubrication, the lubricating oil can take away most of the friction heat inside the bearing and effectively dissipate heat. c. When grease lubrication is used, foreign matter such as dust can be prevented from entering the bearing and sealing. d. Lubricants have the effect of preventing metal corrosion. e. Extend the fatigue life of the bearing.
4.4.2 Comparison of grease lubrication and oil lubrication The lubrication methods of bearings are roughly classified into grease lubrication and oil lubrication. In order to fully utilize the function of the bearing, it is important to use a lubrication method depending on the purpose of use reduction and use. Table 4-2 shows the advantages and disadvantages of grease lubrication and oil lubrication.
4.4.3 Grease Lubricating Grease is a lubricant consisting of a base oil, a thickener and an additive. When selecting, you should choose a grease that is very suitable for the conditions of use of the bearing. Due to the different trademarks, there will be great differences in performance, so you must pay attention when choosing. Commonly used greases for bearings include calcium-based greases, sodium-based greases, calcium-sodium-based greases, lithium-based greases, aluminum-based greases, and molybdenum disulfide greases. The amount of grease filled in the bearing is preferably 1/2-1/3 of the internal space of the bearing. It should be reduced to 1/3 at high speed. Excessive grease will increase the temperature rise.
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Lightweight noise lubrication maintenance of electric spindle bearings
When the raceway of the electric spindle bearing is running, the continuous sound emitted by the rolling element rolling on the raceway surface is generally the unique sound that all the electric spindle bearings will produce. The general bearing sound is the rolling sound plus other sounds. The ball bearing's raceway sound is irregular, the frequency is above 1000Hz, its main frequency does not change with the speed, but its total sound pressure level increases with the increase of the speed. For bearings with large rolling sounds, the sound pressure level of the raceway sound decreases with the increase of viscosity; while for bearings with small raceway sound, the sound pressure level decreases when the viscosity increases to about 20 mm2/s or more. For the increase. The greater the rigidity of the bearing housing, the lower the total sound pressure level of the raceway sound. If the radial clearance is too small, the total sound pressure level and main frequency of the raceway sound will increase sharply as the radial clearance decreases. The method for controlling the rolling sound is to select a low-noise electric spindle bearing, that is, a bearing with a small waviness, and carefully select the conditions of use. The raceway sound often affects the noise of the entire machine, and reducing the raceway sound can reduce the noise of the entire machine.
Impact sound of rolling element and its control method When a larger type of ball bearing or cylindrical roller bearing runs at low speed under pure radial load, the rolling element in the non-loading zone will impact the cage due to the small centrifugal force of the rolling element. Or the raceway makes noise. But as the speed increases, the sound will disappear. The control methods for the impact sound of the rolling element are: appropriately reducing the radial clearance, and using the electric spindle bearing of the cage having a reasonable structure and a flexible material.
When the electric spindle bearing rotates, the bearing wears and fails due to frictional resistance. The resistance to the rotation of the electric spindle bearing is composed of rolling friction, sliding friction and lubricant friction. Rolling friction occurs when the rolling elements roll on the bearing raceway; sliding friction occurs on the guiding surface of the rolling body in the cage, the rib guiding surface of the cage, and the roller end face and the ferrule rib in the roller bearing; lubrication The friction of the agent consists of the internal friction of the lubricant at the contact and the agitation and extrusion of the lubricant. Therefore, the resistance of the impedance bearing movement is the sum of the above three frictions. The purpose of lubrication is to avoid the direct contact between the raceway, the rolling element and the cage metal through the grease and its lubrication method, and reduce the frictional heat to minimize the frictional resistance, thereby reducing wear, preventing corrosion and prolonging its use. life.
About 80% of the bearings are lubricated with grease. There are many types of bearings that are sent to the user after being greased in the bearing factory. Therefore, some people refer to grease as the fifth largest part of the bearing's inner ring, outer ring, rolling element, and cage. Explain the importance of grease to bearings.
Impact sound of rolling element and its control method When a larger type of ball bearing or cylindrical roller bearing runs at low speed under pure radial load, the rolling element in the non-loading zone will impact the cage due to the small centrifugal force of the rolling element. Or the raceway makes noise. But as the speed increases, the sound will disappear. The control methods for the impact sound of the rolling element are: appropriately reducing the radial clearance, and using the electric spindle bearing of the cage having a reasonable structure and a flexible material.
When the electric spindle bearing rotates, the bearing wears and fails due to frictional resistance. The resistance to the rotation of the electric spindle bearing is composed of rolling friction, sliding friction and lubricant friction. Rolling friction occurs when the rolling elements roll on the bearing raceway; sliding friction occurs on the guiding surface of the rolling body in the cage, the rib guiding surface of the cage, and the roller end face and the ferrule rib in the roller bearing; lubrication The friction of the agent consists of the internal friction of the lubricant at the contact and the agitation and extrusion of the lubricant. Therefore, the resistance of the impedance bearing movement is the sum of the above three frictions. The purpose of lubrication is to avoid the direct contact between the raceway, the rolling element and the cage metal through the grease and its lubrication method, and reduce the frictional heat to minimize the frictional resistance, thereby reducing wear, preventing corrosion and prolonging its use. life.
About 80% of the bearings are lubricated with grease. There are many types of bearings that are sent to the user after being greased in the bearing factory. Therefore, some people refer to grease as the fifth largest part of the bearing's inner ring, outer ring, rolling element, and cage. Explain the importance of grease to bearings.
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Introduction to several error maintenance of machine tool spindle bearing failure
The bearing installation is normal and the lubrication is sufficient. The original doubt that the lubricating oil did not enter the upper part of the machine spindle bearing was excluded. However, all inner ring channels have indentations or craters or surface crack-type fatigue spalling, rather than subsurface exfoliation failure, which does not occur when the oil supply is sufficient.
These foreign objects and the indentations caused by them destroy the integrity of the oil film and become the fatigue of the early failure of the spindle bearings of the machine tool. The above judgment is correct.
The development of a "seal-clean" type bearing has achieved great success. This kind of bearing is a rubber sealing ring with a special structure on both sides of the original standard bearing. The characteristic is that the sealing ring is mainly used to prevent the intrusion of dirt into the bearing, and the main purpose is to maintain the grease. The seals are different.
1, through the surface feeling bearing quality
In the process of selling Swedish bearings, I found that many customers said that as long as the bearing surface is bright, the quality is good, which is wrong. The surface of the machine tool spindle bearing should be bright, and the reason for this blackness is that the steel used in the bearing is up to standard and its grinding process and cutting fluid used, etc., the former two are the main ones.
2. Is the chamfer bright?
The chamfer of the spindle of the machine tool does not determine the quality of the stainless steel bearing, but it reflects the processing method of the bearing. The chamfer is black, indicating that heat treatment such as quenching increases the hardness of the bearing, and some people think that the chamfer is black and it is not processed completely. This is a misunderstanding.
3, the integrated cage is better than the two bodies, although the new process uses an integrated cage, but it only saves the material, and the performance of the rotation is worse than the two.
In general, the service life of machine tool spindle bearings is related to three factors, one is the quality of the bearing itself. The second is to use the environment. The third is the installation method.
These foreign objects and the indentations caused by them destroy the integrity of the oil film and become the fatigue of the early failure of the spindle bearings of the machine tool. The above judgment is correct.
The development of a "seal-clean" type bearing has achieved great success. This kind of bearing is a rubber sealing ring with a special structure on both sides of the original standard bearing. The characteristic is that the sealing ring is mainly used to prevent the intrusion of dirt into the bearing, and the main purpose is to maintain the grease. The seals are different.
1, through the surface feeling bearing quality
In the process of selling Swedish bearings, I found that many customers said that as long as the bearing surface is bright, the quality is good, which is wrong. The surface of the machine tool spindle bearing should be bright, and the reason for this blackness is that the steel used in the bearing is up to standard and its grinding process and cutting fluid used, etc., the former two are the main ones.
2. Is the chamfer bright?
The chamfer of the spindle of the machine tool does not determine the quality of the stainless steel bearing, but it reflects the processing method of the bearing. The chamfer is black, indicating that heat treatment such as quenching increases the hardness of the bearing, and some people think that the chamfer is black and it is not processed completely. This is a misunderstanding.
3, the integrated cage is better than the two bodies, although the new process uses an integrated cage, but it only saves the material, and the performance of the rotation is worse than the two.
In general, the service life of machine tool spindle bearings is related to three factors, one is the quality of the bearing itself. The second is to use the environment. The third is the installation method.
For more information and purchase please visit: https://www.supplyforever.com
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