Precautions for correctly judging the operation law of NSK linear bearing
Precautions for correctly judging the operation law of NSK linear bearing
2022年4月13日
Effect of Timken imported bearing quality on temperature and vibration
Effect of Timken imported bearing quality on temperature and vibration
2022年4月13日

The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed

  • Early detection of IKO faults is of great benefit to mechanical equipment and production. So how can we do this work better?The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • If the failure of IKO bearing in operation can be identified or predicted without disassembly and inspection, it is very beneficial to improve productivity and economy. There are three main fault identification methods for linear bearings:

The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed

  • The bearing sound recognition shall be carried out by special personnel or listeners and sound sticks
  • Recognition by sound requires a wealth of experience. Must be fully trained to recognize IKO bearing sound and non bearing sound. Therefore, special personnel should be assigned to carry out this work as far as possible. The sound of linear bearing can be clearly heard by sticking the listener or listening stick on the shell.
  • Identification by the status of IKO bearing lubricant
  • Firstly, the lubricant is sampled and analyzed to judge whether its turbidity is mixed with foreign matters or metal powder. This method is especially effective for bearings that cannot be close to observation or large bearings.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • Identification by operating temperature of IKO bearing
  • This method is a comparative identification method, which is only used in the situation where the running state does not change much. For this purpose, continuous temperature recording must be carried out. In case of failure, not only the temperature rises, but also irregular changes occur.
  • The resultant force of the force shall pass through the axis of the imported bearing as far as possible, which requires that the force application point shall be uniform, symmetrical and stable, and the force shall be applied through the spherical surface or parallel to the axis.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • The force should be applied stably and evenly without impact, which requires the use of oil pressure or tools that can apply stable tension or pressure. When hammering has to be used, it should also be buffered by soft metal without chip falling, such as copper sleeve, and the knocking force should be as light as possible. Hammer with a copper bar or hammer.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • Avoid applying force through the rolling element, which requires applying force through the inner ring when installing and removing the inner ring (shaft ring) and through the outer ring when installing and removing the outer ring).The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • The drag force shall be maintained to a proper extent. For example, when installing the bearing, stop the force when the bearing is just installed in the correct position, and ensure that the end face of the ferrule (washer) is against the seat hole or the shoulder end face of the shaft, which can not be squeezed too tightly or installed in place.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • The judgment standard shall be different according to the mechanical performance, importance and inspection cycle. In case of fracture and defect of linear bearing parts, peeling of raceway surface and rolling surfacThe common problems and Countermeasures of loading failure of imported rotary table bearing are analyzede, the imported bearing shall not be reused and must be replaced.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • The rotating sound of the bearing is checked with a stethoscope, and there are strong metal noise, abnormal sound, irregular sound and other abnormalities. The bearing seat is damaged or damaged by foreign matters.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • Different lubricating greases form different profiles in rolling bearings. The profile must be quite drafted, and the walking time is short. In the long-term operation, the bearing temperature is low and stable. This is a kind of fantasy lubricating grease. Therefore, the channelization of lubricating grease is particularly important.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • Under popular conditions, the filling amount of rolling bearing grease always exceeds the practical demand of direct intervention lubrication, fills the cavity on the support and the bearing cover, and forms a contour on the periphery of the rolling body. The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • During this process, the bearing temperature rises rapidly due to the resistance of excess grease. Although most of the excess grease is squeezed out at the initial stage of operation, and the grease squeezed in the accessories of the raceway may still be migrated and transformed into the rolling element and brought into the raceway.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • In the initial stage of bearing operation, most of the grease is quickly squeezed out of the raceway (less than one minute), and the accumulated grease is discharged in small quantities in succession as the bearing moves and changes. The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • At this time, the bearing temperature continues to rise until all the excess grease is discharged, which can be called the running in stage of grease. According to the quality and filling amount of grease in the bearing structure, this period may last for more than ten minutes or even several hours.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • Key factors affecting Timken bearing life for many rotating machinery products, their service life mostly depends on the life of bearing components in key parts of the product. “Maintenance free” bearings are not one-way bearings that will never be damaged or fail, but that will not be damaged within a certain period of time. Here, the designers calculated the service life of the bearing. The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • The service life of the bearing is greater than or equal to the overhaul cycle of the mechanical product. In this way, the bearing can be “maintenance free”. When the mechanical product is overhauled, it can be replaced with a new bearing without maintaining the used bearing.
  • Grease lubrication includes the sealing method of filling grease in the sealed bearing in advance, and the filling grease supply method of filling an appropriate amount of grease in the shell and replenishing or replacing it at regular intervals. In addition, for machines with multiple one-way bearings that need lubrication, the centralized grease supply mode with pipes connected to each lubrication position is also adopted. The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • Grease lubrication can be filled with grease for a long time without supplement, and the structure of its sealing device is relatively simple, so it is widely used. Oil lubrication is relatively simple. Regular lubrication can improve the service life of Timken bearings.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
 
  • The imported bearing is allowed to make slight running noise during operation. If the noise is too loud or there is abnormal noise or impact sound, it indicates that the bearing is faulty.
  • The causes of rolling bearing noise are complex. One is the wear of the mating surfaces of the inner and outer rings of the bearing. Due to this wear, the matching relationship between the bearing and the shell and between the bearing and the shaft is damaged, resulting in the axis deviation from the correct position and abnormal noise when the shaft moves at high speed. The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • When Timken bearing is tired, its surface metal will peel off, which will also increase the radial clearance of the bearing and produce abnormal noise. In addition, insufficient bearing lubrication, dry friction and bearing breakage will produce abnormal sound. After the bearing is worn and loose, the cage is loose and damaged, which will also produce abnormal noise.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • When the mechanism is running, the part where the one-way bearing is installed is allowed to have a certain temperature. When touching the mechanism shell by hand, it should be normal to feel that it is not hot. Otherwise, it indicates that the bearing temperature is too high.
  • The reasons for high bearing temperature include: the quality of lubricating oil does not meet the requirements or deteriorates, and the viscosity of lubricating oil is too high; The mechanism assembly is too tight (insufficient clearance); Timken bearing assembly is too tight; The bearing race rotates on the shaft or in the shell; Excessive load; Broken rolling bearing or cage, etc.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • The vibration system composed of stiffness, flexibility, mass and damping determined by the structural design parameters of one-way bearing will produce vibration suitable for its mechanics under operating conditions.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • Vibration caused by deviation in manufacturing and processing. The smaller the deviation is, the smaller the vibration is. The roundness, waviness and surface roughness of the steel ball surface are the factors that have a great impact on the vibration of each bearing part, followed by the shape error and surface roughness of the inner ring and outer ring channels, and then the cleanliness and lubricant quality of one-way bearing.
  • Operating conditions, such as installation conditions, rotating speed, axial load direction, quantity, etc.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • As soon as the imported bearing rotates, the raceway surface of the inner ring and the outer ring is in rolling contact with the rolling element, so the running track is a dark surface. The running track attached to the raceway surface is not abnormal, so the load conditions can be known. 
  • Therefore, please pay close attention to and observe the running track of the raceway surface when disassembling Timken bearing.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • If you carefully observe the running track, you will know that it only bears radial load, large axial load, moment load, or extreme uneven rigidity on the bearing housing. It can be checked whether the unexpected load is added to the rotary table bearing and whether the installation error is too large, which will become a clue to investigate the cause of bearing damage.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed
  • Lubrication is very important, not only for bearings, but also for all bearings. However, please note that the bearing should not add too much grease. Then it is to replace the lubricant of the imported bearing. For Timken bearings lubricated with engine oil, after draining the old engine oil, if possible, refill fresh engine oil and let the machine rotate at low speed for a few minutes. 
  • Make the oil collect residual pollutants as much as possible, and then drain the oil. When replacing the grease of the bearing lubricated with grease, the Joe remover used shall avoid the contact of cotton with any part of the bearing. Because these residual fibers may wedge between rolling parts and cause damage, especially in the application of small bearings.The common problems and Countermeasures of loading failure of imported rotary table bearing are analyzed

1、 Use and install carefully

  • It is not allowed to punch with force, directly knock the bearing with a hammer, and transfer pressure through the rolling element.

2、 Use appropriate and accurate installation tools

  • Try to use special tools and try to avoid using things such as cloth and short fiber.

3、 Try to keep the bearings and their surroundings clean

  • Even if the invisible smile dust enters the bearing, it will increase the wear, vibration and noise of the imported bearing.

4、 Prevent bearing corrosion

  • When taking the rotary table bearing directly by hand, fully wash the sweat from your hands and apply high-quality mineral oil before operation. Pay special attention to rust prevention in rainy season and summer.
  • Under some special operating conditions, the bearing can obtain a longer life than the traditional calculation, especially under light load. These special operating conditions are the surface damage that may be caused when the rolling surface (track and rolling parts) is effectively separated and limited by a lubricating oil film. In fact, under ideal conditions, the so-called permanent bearing life is possible
  • When inspecting the bearing, never expose the bearing to pollutants or moisture. If the work is interrupted, the machine shall be covered with oil paper, plastic sheet or similar materials. If it is possible to clean the naked Timken bearing without disassembly, clean it with a brush coated with petroleum solvent, and then wipe it dry with a piece of lint free cloth or blow it dry with compressed air (be careful not to start the rotation of the bearing assembly). 
  • Use a small mirror and a probe similar to that used by dentists to check the track surface, retainer and beads of the bearing. Do not clean the sealed cover or dust-proof bearing; Just wipe the outer surface. If the bearing is damaged, it needs to be replaced. The replacement of imported bearings during regular shutdown and maintenance is much more economical than the loss of sudden shutdown due to array bearing damage.
  • Contact fatigue failure refers to the failure of bearing working surface caused by alternating stress. Contact fatigue spalling occurs on the working surface of the bearing and is often accompanied by fatigue cracks. It first occurs from the large alternating shear stress below the contact surface, and then extends to the surface to form different spalling shapes, such as pitting or pitting spalling, which is called shallow spalling.
  • Wear failure refers to the failure caused by the continuous wear of the metal on the working surface caused by the relative sliding friction between the surfaces. Continuous wear will gradually damage the rotary table bearing parts, and eventually lead to the loss of bearing dimensional accuracy and other related problems. 
  • Wear may affect the change of shape, the increase of fit clearance and the change of working surface morphology, may affect the lubricant or make it polluted to a certain extent, resulting in the complete loss of lubrication function, so that Timken bearing loses its rotation accuracy and even can not operate normally.
  •  Wear failure is one of the common failure modes of various imported bearings. According to the wear form, it can be divided into common abrasive wear and adhesive wear.
  • How to protect it and prolong its service life, the following matters should be paid attention to when using the bearing:
  • The installation and adjustment of low-noise NTN bearing can also follow the grouping method of long-life bearing, so that the matching interference is more consistent, and the clearance of NTN bearing is also more consistent. It is hoped that the matching interference will take a smaller value within the possible range, so as to ensure that the deformation of NTN bearing raceway is small, and the noise caused by the passage of rolling element will be reduced.
  • The clearance has a great influence on the noise. The ideal state is that when the NTN bearing is in the high temperature state of operation, the clearance value is just zero. The methods to judge the excessive clearance are: the axial displacement of the bearing in the static state, the reciprocating amplitude is large, and a large and turbid noise is emitted during operation.
  • If there is an annoying shriek during operation, it indicates that the preload of NTN bearing is too large and the bearing has too large pre interference. The preload should be slightly relaxed. If the clearance is too large, the two bearing rings can be slightly offset along the axial direction: it not only reduces the clearance, but also increases the axial rigidity and reduces the bearing noise.
  • When the rolling element enters the no-load area, it will slip or move left and right, which will not only increase the noise, but also cause wear. Small clearance and large axial stiffness can eliminate this phenomenon. However, the clearance should not be too small, so as not to cause excessive temperature and shorten service life.