Factors affecting the tolerance of NTN combined bearings and their solutions

The maintenance and repair of NTN combined bearings can ensure the reliability of operation, improve the productivity and economy, so as to prevent accidents, ensure the reliability of operation, improve the productivity and economy, and ensure that the plain bearing can maintain its original performance in good condition for a long time.

Bearing cleaning: gasoline and kerosene are commonly used as common cleaning agents. When disassembling the lower NTN bearing for maintenance, first record the appearance of the bearing, confirm the residual amount of lubricant, and then start cleaning the joint bearing after sampling the lubricant for inspection. Cleaning is divided into coarse cleaning and fine cleaning, which are placed in the container respectively. First, put the metal mesh pad on the bottom, so that the bearing does not directly contact the dirt of the container.NTN combined bearings
In the process of using bearings, regular cleaning is very important. How to clean bearings accurately? When the joint bearing is removed for inspection, the appearance record shall be made by means of photography. In addition, confirm the amount of remaining lubricant and sample the lubricant before cleaning the bearing.NTN combined bearings
The cleaning of NTN bearings can be divided into rough cleaning and fine cleaning, and the metal grid can be placed at the bottom of the applied container.
During rough cleaning, use a brush on the top of the oil to remove grease or adhesion. At this time, if the joint bearing is migrated and changed in the oil, the rolling surface will be damaged due to foreign matters.
During fine cleaning, the bearing shall be slowly moved and changed in oil, and it shall be stopped with great efforts.
The cleaning agents used on weekdays are neutral water-free diesel oil or oil, and warm lye is sometimes used according to the demand. No matter what kind of cleaning agent is used, it should always be filtered and kept clean.
After cleaning, coat the joint bearing with antirust oil or grease immediately.
Maintenance and judgment of NTN bearing: in order to judge whether the disassembled bearing can be used, it should be checked after the bearing is cleaned.
The maintenance contents include: monitoring the operation status, supplementing and changing the lubricant, and regularly disassembling the inspection, which is the operation standard for maintaining the operation conditions of the corresponding machinery, and shall be carried out regularly. As maintenance items during operation, there are rotating sound, vibration, temperature, lubricant status, spherical plain bearings and other separable bearings, and the raceway surfaces of rolling elements and outer rings can be inspected respectively.
Check the state of the raceway surface, rolling surface and mating surface, the wear of the cage, the increase of NTN bearing clearance and the abnormal damage of irrelevant dimensional accuracy decline. For non separable small ball bearings, use one hand to support the inner ring horizontally, and rotate the outer ring to confirm whether the large bearing cannot be rotated by hand. Pay attention to the appearance of the rolling element, raceway surface, cage, edge retaining surface, etc.
The more important the joint bearing is, the more careful the inspection is. Influence of temperature: when NTN bearing is working, due to friction heating and other heat sources, the temperature of the ferrule will be higher than that of the corresponding parts.
The thermal expansion of the inner ring loosens the fit with the journal, while the thermal expansion of the outer ring tightens the fit with the housing hole. Therefore, when the working temperature of the bearing is higher than 100 ℃, the selected matching shall be properly modified to ensure the normal operation of the combined bearing.NTN combined bearings
Influence of structure and material of journal and housing hole: the fit tightness between split housing hole and integral housing hole and bearing outer ring is different. The former is slightly loose to avoid flattening the outer ring; The fit between thin-walled shell or hollow shaft and bearing ring shall be tighter than that between thick-walled shell or solid shaft and combined bearing ring to ensure sufficient connection strength.NTN combined bearings
Axial movement of bearing assembly: it can be seen from the above that during the operation of NTN bearing assembly, the journal is easy to stretch due to heating. Therefore, one end of the bearing assembly should ensure a certain axial movement space, and the bearing ring at that end should be loosely matched with the corresponding accessories to ensure that the axial movement can be realized.NTN combined bearings
Influence of rotation accuracy and rotation speed: when the rotation accuracy of NTN bearing is required to be high, the bearing with higher accuracy grade and higher shaft and hole tolerances shall be selected; For the combined bearing with large load and high rotation accuracy requirements, in order to eliminate the influence of elastic deformation and vibration, the rotating ring should avoid using clearance fit, but should not be too tight; NTN combined bearings
For the high-precision bearings used in precision machine tools with small load, in order to avoid the influence of the shape error of the accessories on the rotation accuracy, whether the rotating ferrule or the non rotating ferrule, it is often desired to have a small clearance in the fit with the shaft or hole. NTN combined bearings
When the rotation speed of the bearing is too high and the bearing works under impact dynamic load, the fit of the bearing with the journal and housing hole shall be interference fit. Under the same other conditions, the higher the bearing speed is, the tighter the fit should be.NTN combined bearings
Coordination of tolerance class: the tolerance class of journal and housing hole shall be selected in coordination with the tolerance class of bearing. For example, IT6 is generally selected for the journal matched with grade 0 bearing, and it7 is generally selected for the shell hole; For occasions (such as motors) with high requirements for rotation accuracy and operation stability, the journal is generally selected as it5, and the shell hole is generally selected as IT6.NTN combined bearings
Installation and disassembly of bearing: in order to facilitate the installation and disassembly of combined bearing, loose fitting shall be considered. If it is required that the assembly and disassembly are convenient but tight, the release bearing or NTN bearing with taper hole, tight set sleeve and withdrawal sleeve on the inner ring can be used. To sum up, there are many factors affecting the matching of rolling bearings, which are usually difficult to determine by calculation, so the matching of bearings can be selected by analogy in actual production.NTN combined bearings
The main causes of bearing fracture failure are defect and overload. When the external load exceeds the material strength limit and causes the part to break, it is called overload fracture. The overload is mainly caused by sudden failure or improper installation of the host. NTN combined bearings
The defects of NTN bearing parts, such as microcracks, shrinkage cavities, bubbles, large foreign objects, overheated structures and local burns, will also cause fracture at the defect during impact overload or severe vibration, which is called defect fracture. NTN combined bearings
It should be pointed out that the above defects can be correctly analyzed by instruments during the factory re inspection of raw materials, the quality control of forging and heat treatment, and the control of machining process in the manufacturing process of composite bearings, and the control must be strengthened in the future. But generally speaking, most of the bearing fracture failures are overload failures.NTN combined bearings
In the working process of NTN bearing, due to the influence of external or internal factors, the original fit clearance is changed, the accuracy is reduced, and even “seizing” is called clearance change failure. External factors such as excessive interference, improper installation, expansion caused by temperature rise, instantaneous overload, and internal factors such as residual austenite and residual stress in an unstable state are the main reasons for the change of clearance.NTN combined bearings
In the working process of NTN bearing, due to the influence of external or internal factors, the original fit clearance is changed, the accuracy is reduced, and even “seizing” is called clearance change failure. External factors such as excessive interference, improper installation, expansion caused by temperature rise, instantaneous overload, and internal factors such as residual austenite and residual stress in an unstable state are the main reasons for the change of clearance.NTN combined bearings
If the NTN bearing is well lubricated and properly blocks sundries and moisture, it means that the oil seal should not be worn However, when opening the bearing housing, check the bearing and regularly check the oil seal Check the condition of oil seals near the high-temperature bearing to ensure that they are sufficient to prevent hot liquid or corrosive liquid or gas from penetrating into the bearing along the axis. If the oil seal is worn, replace it as soon as possible
High temperature often indicates that the bearing is in abnormal condition High temperatures are also detrimental to lubricants in bearings Sometimes the overheating of bearings can be attributed to the lubricant of NTN bearings If the bearing operates for a long time at a temperature of more than 125 ℃, the service life of the high-temperature bearing will be reduced
The causes of high-temperature bearings include insufficient or excessive lubrication, magazines in the lubricant, excessive load, bearing damage, insufficient clearance, and high-temperature friction caused by oil seals
Check the condition of the running machine and monitor it to avoid equipment shutdown
As long as NTN bearings are well maintained and tested, high-temperature bearings will certainly serve the long-term operation of machinery. Because the earlier the problem is found, it will be well solved, effectively increasing the service life of the bearing. The following are some precautions for bearing maintenance and inspection.NTN combined bearings
In the process of using NTN bearings, regular cleaning is very important. How to clean bearings accurately? When the bearing is removed for inspection, the appearance record shall be made by means of photography. In addition, confirm the amount of remaining lubricant and sample the lubricant before cleaning the bearing.NTN combined bearings
The cleaning of NTN bearings can be divided into rough cleaning and fine cleaning, and the metal grid can be placed at the bottom of the applied container.NTN combined bearings
During rough cleaning, use a brush on the top of the oil to remove grease or adhesion. At this time, if the high-temperature bearing is transferred in the oil, the rolling surface will be damaged due to foreign matters.NTN combined bearings
During fine cleaning, the bearing shall be slowly moved and changed in oil, and it shall be stopped with great efforts.NTN combined bearings
The cleaning agents used on weekdays are neutral water-free diesel oil or oil, and warm lye is sometimes used according to the demand. No matter what kind of cleaning agent is used, it should always be filtered and kept clean.NTN combined bearings
After cleaning, coat the NTN bearing with antirust oil or grease immediately.NTN combined bearings

We want to emphasize NTN combined bearings

Regular inspection of NTN bearings is very important to maintain the bearings in good condition, and can also reflect the problems found. Matters needing attention and relevant knowledge about bearing in use.NTN combined bearings
We want to emphasize that it is very important to keep the flange bearings lubricated and clean. Therefore, before we inspect the NTN bearing, we should first clean the surface of the bearing, and then disassemble the parts around the bearing.NTN combined bearings
It should be noted that the oil seal is a very fragile part, so extra care should be taken during inspection and disassembly. Do not apply excessive force to avoid damage to the parts. Then carefully check the oil seal of the bearing and its surrounding parts. If there are bad symptoms, be sure to replace them. The bad oil seal will cause damage to the bearing, make the bearing cloud abnormal and cause the equipment shutdown.
We also check the lubricant of the bearing. Lubrication is important, not for bearings, but also for all flange bearings. However, please note that NTN bearings should not be greased too much.
Rub between your fingers with a little lubricant. If there are pollutants, you can feel them; Or apply a thin layer of lubricant on the back of the hand, and then perform light sealing inspection.
After draining the old engine oil from the bearings lubricated with engine oil, if possible, refill fresh engine oil and let the machine rotate at low speed for several minutes. Make the oil collect residual pollutants as much as possible, and then drain the oil.
Note: the engine oil is filtered before use. When replacing the grease of the bearing lubricated with grease, the arbor used shall avoid cotton contacting any part of the flange bearing. Because these residual fibers may wedge between the rolling parts and cause damage, especially in the application of small bearings.NTN combined bearings
NTN bearing failure is often due to a variety of factors, all the design and manufacturing process factors and bearing failure, their analysis is not easy to determine. Under normal circumstances, in general, you can consider and analyze factors and internal factors.NTN combined bearings
The main factors used for adjustment are that the installation, use and maintenance, maintenance and repair meet the technical requirements. Installation conditions are one of the factors that use bearings and are often the primary factors that cause incorrect load-bearing capacity of the state changes between various parts of the installation package, operation in abnormal states and early failure. NTN combined bearings
Monitor and inspect the contact load, speed, temperature, vibration, noise and lubrication status of the bearing operated according to the technical requirements for installation, use, maintenance and maintenance of the flange bearing. In case of any abnormality, immediately find out the cause and adjust it back to normal.NTN combined bearings
The metallurgical quality of NTN bearing material is the main factor of early failure of rolling bearings. With the progress of Metallurgical Technology (such as bearing steel, vacuum degassing, etc.), the quality of raw materials has been improved. NTN combined bearings
The proportion of raw material quality factor in flange bearing fault analysis has decreased significantly, but it is still one of the main factors of bearing failure. It is still necessary to consider the failure analysis of rolling bearings. The NTN bearing is strongly impacted during use, which will produce scars and indentations, which will become the cause of the accident. In serious cases, cracks and fractures may occur, so attention must be paid.NTN combined bearings
To avoid replacing with the existing tool NTN bearing tools, proper tools must be used. We often emphasize the importance of tools because too many customers use the wrong tools during installation, resulting in the damage of self-aligning roller bearings.
On the shaft and in the bearing seat, the bearing is required to fix its position in the radial, axial and tangent directions. Radial and tangential positioning is realized by tight fitting of bearing rings, while axial positioning is only realized by tight fitting in a few cases; Generally, axial limit parts, such as end caps and retaining rings, are used to limit the axial position within the clearance range.NTN combined bearings
The following four points shall be paid attention to when selecting the fitting:NTN combined bearings
The circumferential surface of bearing ring shall be well supported and evenly stressed to reduce deformation and give full play to the bearing capacity of self-aligning roller bearing.
The ferrule shall not slide along the tangent direction in its mating surface, otherwise the mating surface will be damaged.
The free end bearing must be able to adapt to the length change of the shaft and bearing seat hole, that is, it must have the ability to adapt to the axial position within a certain range.
Attention must be paid to making the NTN bearing easy to install and disassemble, saving labor, time and expense. When operating self-aligning roller bearings, sweat on your hands can become a cause of rust. Pay attention to operate with clean hands and wear gloves as much as possible.
Proper removal tools shall be used to prevent damage to other machine components. Incorrect removal technology may cause damage to the bearing. If the bearing reaches its final service life, it shall be replaced. Although the self-aligning roller bearing can no longer be used, the correct removal of the original bearing and the timely replacement of the new bearing can play a good role in promoting the extension of the service life of the new bearing. Therefore, the replacement of the old and new bearings is very important, which requires professional personnel to conduct inspection and operation
The thermal sensor can be used to monitor the working temperature of the movable bearing at any time, and automatically alarm or stop when the temperature exceeds the specified value to prevent the occurrence of combustion shaft accidents. High temperature often indicates that the bearing is in abnormal condition. High temperatures are also harmful to the bearing lubricant.
Sometimes bearing overheating can be attributed to the lubricant of the bearing. If the temperature of the self-aligning roller bearing exceeds 125 ℃ for a long time, the service life of the bearing will be reduced. The causes of high temperature bearings include insufficient or excessive lubrication and lubricant. It contains impurities, excessive load, bearing ring damage, insufficient clearance, high friction caused by oil seal, etc.
Therefore, it is necessary to continuously monitor the temperature of moving bearings. NTN bearings are used to measure the bearing itself or other important parts. If the operation premise remains unchanged, any temperature change can indicate that a fault has occurred.
The regular measurement of bearing temperature can be aided by a thermometer, such as a digital thermometer, which can accurately measure the temperature of self-aligning roller bearings and display it in units of ℃ or Fahrenheit.
The temperature of the bearing can be inferred from the temperature outside the bearing chamber. If the temperature of the outer ring of the bearing can be measured directly by using the oil hole, the bearing is more suitable. Generally, the temperature of self-aligning roller bearing begins to rise slowly with the operation of the bearing, and reaches a stable state after 1-2 hours.
The normal temperature of NTN bearing varies with the thermal capacity, heat dissipation, rotating speed and load of the machine. If the lubrication and installation parts are appropriate, the bearing temperature will rise sharply, which will cause abnormal high temperature. At this time, it is necessary to stop the operation and take necessary preventive measures.

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