Use and fit of SKF Bearing
Use and fit of SKF Bearing
2022年5月9日
Function of deep groove ball bearing
Function of deep groove ball bearing
2022年5月10日

How to identify NTN bearing quality

NTN bearing quality working state monitoring instrument

  • The specific judgment method of whether fag bearing should be reported for repair, that is, the specific judgment method of fag bearing has been fully utilized and near damage is as follows:NTN bearing quality
  • It is a convenient and reliable method to judge the working state of fag bearing and decide when fag bearing should be repaired by using such instruments as Ferrograph or SPM or i-id-1 fag bearing working state monitoring instrument.NTN bearing quality
  • For example, when HD-1 instrument is used, when the pointer approaches the dangerous area from the warning area, and the pointer does not return after taking measures to improve lubrication, it can be determined that it is the problem of fag bearing itself. At this time, the fag bearing can be reported for repair before entering the dangerous area. How far away from the dangerous area to start the repair can be adjusted by experience.
  • Using such an instrument, we can make full use of the working potential of fag bearings, report fag bearings for repair in time, and avoid faults. It is and economical.NTN bearing quality
  • In the absence of the above instruments, the operator can hold a round bar or wrench and other tools to collide with the part of the machine shell close to the imported fag bearing, shame his ears on the tool and listen for the sound of fag shaft transmitted by the tool. Of course, it is also possible to refit the medical stethoscope.
  • The normal fag shaft rotation sound should be uniform, stable and not harsh, while the abnormal fag shaft rotation sound has a variety of intermittent, impact or harsh sounds. First, get used to the normal fag shaft carrying sound, and then you can grasp and judge the abnormal fag shaft carrying sound. Then, through the accumulation of practical experience, you can further analyze what kind of abnormal sound corresponds to what kind of abnormal phenomenon of fag bearing. There are many types of abnormal sounds of fag bearings, which are difficult to speak and mainly rely on experience accumulation.
How to identify NTN bearing quality

Monitor with simple tools,NTN bearing quality

  • Constant pressure pre tightening is the key point of pre tightening INA Bearing with coil spring, Belleville spring, etc. The rigidity of the preload spring is generally much smaller than that of the INA Bearing, so the relative position of the INA Bearing preloaded under constant pressure will change in use, but the preload is largely stable.
  • When the preload is proportional, the positioning preload has a greater effect on the rigidity growth of INA Bearing, and the rigidity change of INA Bearing has a much smaller effect on the load of INA Bearing.How to identify NTN bearing quality
  • In the use of positioning preload, the axial length difference caused by the temperature difference between the shaft and ina bearing seat, the radial expansion caused by the temperature difference between the inner and outer rings and the displacement caused by load will change the preload; While the constant pressure preload is in use, the change of preload can be ignored carelessly.How to identify NTN bearing quality
  • The radial jacking method is mostly used in tapered bore bearings subjected to radial load. A typical example is the double row precision short cylindrical roller bearing. The nut is used to mediate the axial position of the INA Bearing relative to the sub tapered journal, so that the inner ring has a suitable expansion amount to obtain radial negative clearance. This method is mostly used in machine tool spindle and jet engine.How to identify NTN bearing quality
  • Axial preloading method can be roughly divided into positioning preloading and constant pressure preloading. In positioning preload, ina bearing can decide the size of adjusting bushing or gasket to obtain the appropriate preload; It can also be decided to measure or control the starting friction torque to adjust the appropriate preload; How to identify NTN bearing quality
  • The purpose of preloading can also be realized by directly using the paired duplex ina bearings with preload adjusted in advance. At this time, there is no need for users to mediate. In short, the relative position of ina bearings with axial preload will not change when used.How to identify NTN bearing quality
  • In the oil supply system of hydrostatic fag bearing, except for coarse filtration and fine filtration, other components have a protective effect on hydrostatic fag bearing. The oil supply system is improved on the basis of the original system. The oil outlet behind the throttle plate is connected with a pressure relay and a pressure gauge (originally in front of the accumulator), so that the operator can see the chamber pressure and pressure. How to identify NTN bearing quality
  • When the differential pressure is greater than a certain value, the machine can be shut down immediately to prevent the bearing bush from locking. For example, if the pressure is 2 MPa and the outlet cavity pressure is 1.2 ~ 1.6 MPa, the machine will be shut down if it is lower than 1.2 MPa.How to identify NTN bearing quality
  • There is a gap of 0.04 ~ 0.05mm between the main shaft and bearing bush of wear-resistant electrode static pressure fag bearing, and the oil in between has a certain resistance value. By detecting the change of this resistance value, we can know the size of the phase gap. How to identify NTN bearing quality
  • Take the main shaft as one pole and the bearing bush as the other pole, and measure the resistance change. After processing, the signal is sent to the photoelectric alarm and control system amplifier to control the start and stop of the spindle motor, so as to avoid the friction between the shaft and the bearing
  • The stiffness of thin film feedback throttling fag bearing is very large, but the phenomena such as pad holding, roughening and pressure drop often occur in the operation of machine tools. The key of film feedback is film. In practice, it is considered that the main reasons for bearing bush locking and galling are: ① plastic deformation of film; ② Feedback is slow. 
  • When the external load changes suddenly and the film has not reacted, the shaft and pad have been rubbed; ③ Film fatigue. The film has long service time and fatigue deformation, which is equivalent to changing the feedback parameters.How to identify NTN bearing quality
  • Good results can be obtained by increasing the thickness of the film and using some fatigue resistant materials. Generally, rigid membrane, preloading and reserved gap are adopted. The specific method of fag bearing is to change the 1.4mm thick film into 4mm thick rigid film, pad 0.05mm thick tin foil paper in the lower cavity, and adjust the spindle to a position 0.05mm higher than the ideal position.How to identify NTN bearing quality
  •  The purpose is to return to the ideal center just after the spindle is stressed (grinding wheel weight, cutting force). The sound detector is used to check the rolling sound and sound quality of the running fag bearing. Even if there is slight peeling and other damage, the fag bearing will emit abnormal sound and irregular sound, which can be distinguished by the sound detector.
  • listen for
  • It is a common method to use hearing to identify irregular operation. For example, it is often used by experienced operators to detect the abnormal noise of a part with the help of an electronic stethoscope.How to identify NTN bearing quality
  • If fag bearing is in good continuous rotation state, it will make a low whine sound. If sharp hiss, squeak and other irregular sounds are made, it often indicates that fag bearing is in poor continuous rotation condition.How to identify NTN bearing quality
  • Sharp squeaking noises may be caused by improper lubrication. Improper fag bearing clearance can also cause metallic sound. Dents on the concave track of fag bearing outer ring track will cause vibration and cause smooth and crisp sound. If the knocking scar caused during installation will also produce noise, the noise will vary with the speed of fag bearing.How to identify NTN bearing quality
  • If there is intermittent noise, it indicates that the rolling parts may be damaged. This sound occurs when the damaged surface is rolled out. If there are pollutants in fag bearing, it will often cause hissing sound. Serious damage to the bearing will produce irregular and loud noise.How to identify NTN bearing quality
  • Fag bearing damage can be detected by hearing, but usually it is time for fag bearing to be replaced immediately. Therefore, it is better to use, for example, electronic condition monitoring instruments. The fag bearing condition can be estimated more accurately by using a wooden stick than the old method.How to identify NTN bearing quality

Add digital detection device:NTN bearing

  • NSK bearing is a mass-produced mechanical part with strict manufacturing accuracy and high degree of technical specialization. Therefore, for the vast majority of easy to buy NSK bearing varieties, it should be more cost-effective to buy than repair. The repair of NSK bearing can only be considered under the following circumstances, namely:
  • The failure forms of a large number of NSK Bearings of the same model used in large factories are mainly surface wear, fatigue or fretting abrasion. In particular, most of the damaged parts are cages or bodies, and the rings or washers still have repair value;
  • Large and extra large NSK Bearings are on the verge of failure or have failed without major damage to parts, or valuable NSK Bearings must try to prolong their effective service life;
  • Some NSK bearing varieties that are really difficult to buy have to be repaired without spare parts after failure, especially NSK Bearings;
  • NSK Bearings are slightly damaged, such as slight water rust during storage and slight fretting abrasion during transportation. Such cases are easy to repair and regrettable to discard.
  • In addition to the economy, the repair of NSK bearing also has its technicality, which requires the repairer to fully understand the corresponding technical requirements of NSK bearing and the characteristics of NSK bearing and its parts in structure, technology and materials. Otherwise, it is difficult to ensure that NSK bearing repair has the required effect.
  • Economic benefits of NSK bearing repair
  • Generally speaking, there are few varieties and large quantities of NSK Bearings, the price of a single NSK bearing is high, or the structure of NSK bearing is simple. If the size is large, the lower the repair cost is, the higher the economic benefit is.
  • In addition, monitoring the operation of NSK bearing and repairing it before NSK bearing failure in a planned way can get twice the result with half the effort. Following reasonable process, using efficient repair equipment and tools and obtaining the help of professional NSK bearing factory will help to improve economic benefits.

The specific force of positioning preload and constant pressure preload is as follows:NTN bearing quality

  • High speed grinding technology is widely used. When grinding the inner surface, the linear speed of the grinding wheel can reach 60 ~ 80m / S; When grinding the outer surface, the linear speed of the grinding wheel can reach 120m / s.
  • The improvement of grinding wheel grinding linear speed puts forward new requirements for the dynamic balance of grinding wheel. Therefore, the grinding machine tools adopt the dynamic balance device of grinding wheel to make up for the imbalance of grinding wheel caused by grinding.
  • In order to meet the requirements of Timken bearing ring grinding automation, CBN grinding wheel grinding technology has been adopted in Timken bearing ring grinding. Compared with ordinary grinding wheel, its wear ratio is as high as 4000 ~ 10000, which is about 150 times that of ordinary grinding wheel. The grinding efficiency is very high, especially suitable for automatic high-speed grinding.
  • As the material for manufacturing Timken bearing grinder bed, artificial granite is gradually adopted by machine tool manufacturers all over the world because of its strong rigidity, good vibration resistance, low thermal conductivity and short manufacturing cycle.
  • With the help of frequency converter and PC or CNC programming control device, the spindle of head frame and Timken bearing grinder can adjust speed steplessly to obtain large sales volume, high processing quality and maintain the constant linear speed of grinding wheel.
  • With the development of cutting in grinding technology and the application of computer in measurement feedback (inductance active measurement) system, cutting in grinding, dimension measurement and feedback control become a closed-loop system.
  • With the development of hydraulic component technology, the hydraulic system of Timken bearing ring grinder has also been updated. Variable vane pump is widely used to control the working temperature of hydraulic oil at a level higher than 5 ℃ of room temperature, which overcomes the influence of hydraulic system on the working accuracy of machine tool and product processing accuracy.
  • The combined grinding technology of two processes on the same grinder has been applied in Timken bearing ring grinding, which not only ensures high machining accuracy, but also greatly improves the machining efficiency of products.
  • Due to the rapid development of numerical control technology and its hot running components (servo motor, ultra precision roller lead screw and encoder, etc.), PC and CNC control technology are widely used in the control system of Timken bearing ring grinder. The CNC system can program, control, store and modify the action of each mechanism and the whole processing cycle parameters of Timken bearing ring grinder; The grinding wheel dresser realizes the requirements of forming and dressing of linear or circular grinding wheel through NC coordinates.
  • New technology and process equipment of Timken bearing grinding
  • When using NTN bearings, we should first check the appearance of imported bearings to judge whether they meet the standards we require. Let’s share with you what parts we should check.
  • The inspection of NTN bearing should be carried out under the astigmatism lamp, and the appearance, cracks and other parts of NTN bearing should be carefully observed.
  • Damage state: the dark surface of imported bearing with slight wear, on which there are several micro cracks with a depth of 5-10mm from the surface to the inside, and micro peeling occurs in a large range (micro peeling)
  • Cause: improper bearing lubricant. Foreign matter has entered the lubricant. Poor lubricant causes rough surface. The surface finish of paired rolling parts is not good.
  • Measures: select lubricant to improve the bearing sealing device and improve the surface finish of mating rolling parts.
  • Damage state: the imported bearing raceway wheel, steel ball and cage are heated sharply during rotation until they change color, soften, deposit and damage.
  • Reason:   Poor lubrication.  The bearing bears excessive load (excessive preload). 3. The bearing speed is too high.   The clearance is too small. 5. Intrusion of water and foreign matters into the bearing. 6. The accuracy of shaft and bearing box is poor and the deflection of shaft is large.
  • Measures: 1 Study lubricants and lubrication methods. 2. Correct the selection of bearings. 3. Study fit, bearing clearance and preloading. 4. Improve the sealing device. 5. Check the accuracy of shaft and bearing housing. 6. Improve the installation method.