Causes of nine common faults of INA Bearing
Causes of nine common faults of INA Bearing
2022年5月13日
Analysis of distinguishing the burn fault of Koyo bearing
Analysis of distinguishing the burn fault of Koyo bearing
2022年5月14日

Fault inspection of NSK bearings in operation

Check the vibration of NSK bearings in during operation.

  •  The peeling, indentation, corrosion, crack, wear, etc. will be reflected in the vibration measurement of NSK bearing. The vibration of NSK bearing is very sensitive to the damage of NSK bearings.
  •  Therefore, the vibration can be measured by using a special NSK bearing vibration meter (frequency analyzer, etc.), and the specific abnormal situation can not be inferred by frequency division. Since the measured values are different due to the service conditions of NSK bearing or the installation position of sensor, it is necessary to analyze and compare the measured values of each machine in advance to determine its judgment standard.
  • Check the sound condition of NSK bearing during rolling. Even if NSK bearing has slight peeling and other damage, it will produce abnormal sound and irregular sound. Therefore, the sound detector can be used to distinguish. The sound detector is used to check the size and sound quality of NSK bearing rolling sound in operation, so as to prevent it in advance.Fault inspection of NSK bearings in operation
  • To check the temperature of NSK bearing during rotation, it is more appropriate if the temperature of NSK bearing outer ring can be measured directly by oil hole. Generally, the temperature of NSK bearing can be inferred from the temperature outside the NSK bearing chamber. Fault inspection of NSK bearings in operation
  • If the lubrication and installation parts are appropriate, the NSK bearing temperature will rise sharply and abnormal high temperature will occur. At this time, the operation must be stopped and necessary preventive measures must be taken.Fault inspection of NSK bearings in operation
  • Generally, the temperature of NSK bearing rises slowly with the start of operation and reaches a stable state after 1-2 hours. The normal temperature of NSK bearing varies with the heat capacity, heat dissipation, speed and load of the machine. Fault inspection of NSK bearings in operation
  • Whether the outer packaging is clear: generally, the brands of the main factory have their own special designers to design the outer packaging, and arrange the factories with qualified production conditions for production. Therefore, the packaging is very clear from line to color block – unambiguous.Fault inspection of NSK bearing in operation
  • Whether the steel seal words are clear: the SKF Bearing body will be printed with brand words, labels, etc. The font is very small, but most of the products produced by the original factory use steel printing technology, and they are pressed before overheating treatment. Fault inspection of NSK bearing in operation
  • Therefore, although the font is small, it is concave – deep and very clear. The font of counterfeit products is not only fuzzy, but also floating on the surface due to the rough printing technology. Some of them can even be easily erased by hand.Fault inspection of NSK bearings in operation
  • Whether there is any noise: hold the inner sleeve of SKF Bearing with your left hand, and turn the outer sleeve with your right hand to hear whether there is any noise. Due to the backward production conditions of most counterfeit products and the complete manual workshop operation, it is inevitable that impurities such as sand will be mixed in the production process and hidden in the SKF Bearings, so it will make a noise when rotating. This is a big difference from the factory brand that strictly implements production standards and operates with machines.
  • Whether there is muddy oil on the surface: this should be paid special attention when purchasing SKF bearings. As the current domestic antirust technology is not particularly good, it is easy to leave thick oil stains when antirust the SKF Bearing body, which is sticky and thick when holding it in your hand. NSK bearings
  • However, there is almost no trace of antirust oil on the SKF Bearing originally imported from abroad. However, a particularly careful expert said that the imported SKF Bearing smells like a smell. It must be under antirust oil, but it can’t be seen.NSK bearings
  • Whether the chamfer is uniform: the so-called chamfer of SKF Bearing, that is, the junction of horizontal and vertical surfaces. Due to the limitation of production technology, the fake SKF Bearing is not handled satisfactorily at these corners.
Fault inspection of NSK bearing in operation

Whether the steel seal words are clear: the SKF Bearings

  • Whether the outer packaging is clear: generally, the brands of the main factory have their own special designers to design the outer packaging, and arrange the factories with qualified production conditions for production. Therefore, the packaging is very clear from line to color block – unambiguous.Fault inspection of NSK bearings operation
  •  body will be printed with brand words, labels, etc. The font is very small, but most of the products produced by the original factory use steel printing technology, and they are pressed before overheating treatment.Fault inspection of NSK bearings operation
  •  Therefore, although the font is small, it is concave – deep and very clear. The font of counterfeit products is not only fuzzy, but also floating on the surface due to the rough printing technology. Some of them can even be easily erased by hand.Fault inspection of NSK bearings operationFault inspection of NSK bearings operation
  • Whether there is any noise: hold the inner sleeve of SKF Bearing with your left hand, and turn the outer sleeve with your right hand to hear whether there is any noise. Due to the backward production conditions of most counterfeit products and the complete manual workshop operation, it is inevitable that impurities such as sand will be mixed in the production process and hidden in the SKF Bearing, so it will make a noise when rotating. This is a big difference from the factory brand that strictly implements production standards and operates with machines.Fault inspection of NSK bearings operation

Whether there is muddy oil on the surface: NSK bearings

  • this should be paid special attention when purchasing SKF bearings. As the current domestic antirust technology is not particularly good, it is easy to leave thick oil stains when antirust the SKF Bearing body, which is sticky and thick when holding it in your hand. Fault inspection of NSK bearings operation
  • However, there is almost no trace of antirust oil on the SKF Bearing originally imported from abroad. However, a particularly careful expert said that the imported SKF Bearing smells like a smell. It must be under antirust oil, but it can’t be seen.NSK bearings
  • Whether the chamfer is uniform: the so-called chamfer of SKF Bearing, that is, the junction of horizontal and vertical surfaces. Due to the limitation of production technology, the fake SKF Bearing is not handled satisfactorily at these corners. Before scraping and grinding, carefully check whether the journal is smooth and whether there are defects such as rust and bruise, and try to eliminate them first; Fault inspection of NSK bearings operation
  • Then, check the contact between the journal and the shaft. The inspection method is to apply a thin layer of display agent (such as red lead powder, red Qian oil, etc.) on the shaft diameter, then install the journal in the Koyo bearing, rotate it two or three times in the positive and negative directions by hand, take out the shaft, and check the distribution of coloring points on the Koyo bearing. If the distribution of coloring points is abnormal or does not move at all, start scraping and grinding.NSK bearings
  • During scraping and grinding, the principle of first heavy and then light, scraping heavy and leaving light, scraping large and leaving small shall be adopted according to the situation. For the first few times, the hand can be heavier and scrape off more metal, so as to achieve better contact quickly. When the contact area reaches 50%, it should be scraped gently. NSK bearings
  • After each scraping, wipe the tile surface, apply the display agent on the journal for inspection, and then scrape and grind according to the contact condition until it meets the technical requirements. Indicator can be used for scraping and grinding inspection, but for precision Koyo bearings with high requirements for contact points, indicator cannot be used in the later stage of scraping and grinding. Because the coloring point on the Koyo bearing is too large after coating the display agent, it is difficult to judge the actual contact situation.
  •  At this time, the journal can be wiped clean, directly put in the Koyo bearing for verification, and then take out the shaft. It can be seen that the bright spot on the Koyo bearing is the contact point. Then scrape and grind the bright spot until it meets the technical requirements.NSK bearings
  • During scraping and grinding, not only the contact point shall meet the technical requirements, but also the side clearance and contact angle shall meet the technical requirements. Generally, the contact point shall be studied first, and the contact angle shall be taken into account at the same time, and then the side clearance shall be scraped.
  •  However, there should be no obvious boundary between the contact part and the non-contact part. When wiping the surface of Koyo bearing with fingers, no trace should be detected.NSK bearings

Cage is a part without rolling working surface NSK bearing.

  •  Its fault can not impact the inner and outer rings and rolling elements. In principle, it is not among the diagnostic objects.NSK bearings
  • However, the diagnosis system found a large number of cage faults. The mechanism is:NSK bearing
  • When the cage window is broken, the lost objects generated by fracture vibration and friction enter the grease, which is recognized by the system as “free impurity mode” and gives an alarm;NSK bearings
  • Or the lost object adheres to the inner and outer rings and the working surface of the rolling element and is judged as the fault of the parasitic working surface by the system in the “parasitic impurity mode” and gives an alarm;
  • After opening the fag bearing, it is found that it is the cage fault rather than the fault of the specific alarm object (inner and outer rings and rolling elements). This “quasi misdiagnosis” is harmless to a set of fag bearings – it is a “diagnosis” for the fag bearings.NSK bearings
  • The reliability of this “parasitic fault mode” is not 100%, so there are some missed diagnosis of cage fault.
  • The main mechanism is that even if the cage window strip falls off, it will not impact with the rolling parts during uniform speed operation. In this regard, the author has made a test on fag bearing of diesel locomotive axle box: insert a 1m long iron wire between fag bearing cages, and even insert a saw blade. The locomotive runs back and forth for dozens of times in the servicing depot. After decomposition and inspection, the fault parts are intact.NSK bearings
  • Mechanical analysis shows that only in emergency braking and when the grease is very thin, the falling window strip can impact with the rolling body. Accordingly, the 4th generation of the diagnostic system plans to launch the “broken bar detection braking method”, that is, when the braking preparation reverse detection is carried out after the forward rotation detection is completed, the braking method detection is inserted.NSK bearings
  • However, because the material of the cage is softer than that of the inner and outer rings and the rolling element, even if there is an impact with the rolling element during braking, its value is also very small. This brings difficulties to the detection. In particular, FAG bearings of railway freight cars can not be detected after changing to plastic cages.NSK bearings
  • The use of plastic steel cage can not only prevent fracture with the flexibility and uniformity of the cage, but also because even if the cage material is lost in grease, it will not be as dangerous as steel, which is a wise move.NSK bearings

The main causes of corrosion are as follows:NSK bearings

  • In the process of producing NSK Bearings, some enterprises did not carry out anti rust treatment on NSK bearing parts in the processing process and NSK bearing finished products after assembly in strict accordance with the requirements of cleaning and anti rust regulations and oil seal anti rust packaging. Fault inspection of NSK bearings operation
  • For example, the turnover time of the ferrule in the turnover process is too long, and the outer circle of the outer ring is in contact with corrosive liquid or gas.Fault inspection of NSK bearings operation
  • The quality of antirust lubricating oil, cleaning kerosene and other products used by some enterprises in production can not meet the requirements of process and technology regulations.Fault inspection of NSK bearings operation
  • As the price of NSK bearing steel has fallen again and again, the material of NSK bearing steel has gradually declined. For example, the content of non-metallic impurities in steel is high (the increase of sulfur content in steel reduces the corrosion resistance of the material itself), metallographic structure deviation, etc. At present, NSK bearing steel used by production enterprises comes from a variety of sources, and the steel quality is fish dragon mixed beads.Fault inspection of NSK bearings operation
  • The environmental conditions of some enterprises are poor, the content of harmful substances in the air is high, and the turnover site is too small to carry out effective antirust treatment. In addition, the hot weather and the violation of rust prevention regulations by production workers also exist.Fault inspection of NSK bearings operation
  • The anti rust paper, nylon paper (bag), plastic cylinder and other NSK bearing packaging materials of some enterprises do not meet the requirements of anti rust packaging of rolling NSK bearing oil seal, which is also one of the factors causing corrosion.Fault inspection of NSK bearings operation
  • The turning allowance and grinding allowance of NSK bearing rings in some enterprises are too small, and the oxide scale and decarburization layer on the outer circle cannot be completely removed is also one of the reasons.
Fault inspection of NSK bearing in operation

The roundness of the inner race of imported NSK bearings is an important quality index.

  • which directly affects the working accuracy, stability and service life of imported bearing. In addition to the grinding process of the inner ring and the precision of the grinding groove, the precision of the inner ring or the semi-circular groove is usually closely related to the grinding process of the inner ring. Fault inspection of NSK bearings operation
  • The former has been valued by many scholars and has carried out a lot of research, which greatly improves the roundness of grinding inner ring channel. With the improvement of grinding process system accuracy and dynamic characteristics, grinding process parameters have become the main factor affecting roundness.Fault inspection of NSK bearings operation
  •  Therefore, the study of the influence law of grinding process parameters on roundness is of great significance to reasonably select process parameters, ensure the grinding roundness of imported bearing channels, and then optimize the process parameters of grinding imported bearing channels.Fault inspection of NSK bearings operation
  • The groove of imported bearing inner ring usually adopts variable feed rate cut in grinding, and its grinding cycle can be divided into four stages: workpiece rapid approach, coarse feed, fine feed and no feed grinding. The main factors affecting the roundness of the grinding inlet bearing channel can be summarized as follows: Fault inspection of NSK bearings operation
  • The accuracy of the process system in the grinding process, which depends on the accuracy of the grinder and the positioning principle, structural parameters and accuracy of the fixture;Fault inspection of NSK bearings operation
  •  the dynamic characteristics of the process system, especially the balance state of the grinding wheel: in the process of dressing and grinding, the unbalanced grinding wheel will cause forced vibration.Fault inspection of NSK bearings operation
  • Due to the difference between the relative position of the dresser and the grinding wheel when dressing the grinding wheel and the relative position of the workpiece and the grinding wheel when grinding, and the different stiffness of the process system in these two different cases, the vibration causes the surface of the workpiece to be out of round. Fault inspection of NSK bearings operation
  • The grinding process parameters will affect the contact stiffness between the grinding wheel and the workpiece, the wear process of the grinding wheel and the damping characteristics of the vibration of the process system, so as to affect the vibration characteristics of the grinding process, Fault inspection of NSK bearings operation
  • Finally, it is reflected in the geometry (i.e. roundness) and other surface quality of the grinding workpiece: the reflection of the original error of the workpiece caused by the elastic deformation of the process system: by analyzing the variation law of the geometric error of the workpiece in the grinding cycle.Fault inspection of NSK bearings operation
  •  It can be seen that the reflection of the geometric error of the workpiece after grinding mainly depends on the stiffness of the process system, the grinding process parameters, the wear speed of the grinding wheel and the original error of the workpiece?.Fault inspection of NSK bearings operation
  • Considering the above factors, when the stiffness and dynamic characteristics of the process system are certain (especially the grinding wheel must be well balanced), the roundness error of the grinding workpiece mainly depends on the grinding process parameters.Fault inspection of NSK bearings operation
  •  Therefore, through the stepwise regression modeling of the grinding roundness test data, select important parameters from multiple process parameters and gradually introduce the regression equation, so as to establish the optimal regression equation of the relationship between grinding roundness and process parameters.
  • Machine tool vibration caused by unbalanced grinding wheel or other factors will seriously affect the roundness of grinding workpiece. Keeping the good working state of the machine tool and the good balance of the grinding wheel is the prerequisite for the application of the roundness mathematical model.Fault inspection of NSK bearings operation
  •  In addition, the hardness, structure, particle size and abrasive type of grinding wheel, as well as the composition of coolant, will have a certain impact on the roundness of grinding.Fault inspection of NSK bearings operation
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