Original NSK bearing common fault analysis

1. NSK bearing surface strain: cutting abrasive grains are found in the iron spectrum, and the abrasive grain composition is non-ferrous metal.

2, NSK bearing journal surface corrosion: Spectral analysis found that the concentration of iron is abnormal, there are many sub-micron particles of iron in the iron spectrum, the lubricating oil exceeds the standard or the acid value exceeds the standard.

3, NSK bearing tile surface corrosion: spectral analysis found that the concentration of non-ferrous metal elements is abnormal; there are many sub-micron wear particles of non-ferrous metal components in the iron spectrum; lubricating oil moisture exceeds the standard, acid value exceeds the standard.

4, NSK bearing tile back fretting wear: spectral analysis found that the iron concentration is abnormal, there are many iron components in the iron spectrum sub-micron wear particles, lubricating oil moisture and acid value is abnormal.

Under liquid lubrication conditions, the sliding surface is separated by the lubricating oil without direct contact, and the friction loss and surface wear can be greatly reduced. The oil film also has a certain vibration absorbing capability.

5, NSK bearing journal surface strain: iron spectrum cutting abrasive grains or black oxide particles in the iron spectrum, tempering color on the metal surface.

6. Super-precision NSK bearings do not produce metamorphic layers and spikes that are extremely prone to wear, and can also remove the metamorphic layer left by grinding. Increase the service life of the workpiece by about 5 times.

7. The workpiece after super-finishing after NSK bearing grinding can reduce the running noise by 8~10dB after assembly, and the vibration is small. Smooth operation.

8. The margin of ultra-finished NSK bearings is reduced by an order of magnitude compared to the grinding allowance, which is actually only a few microns. For low pressure feed processing. Therefore, the super-finishing has a small dimensional dispersion and an extremely high yield.

9. Super-precision NSK bearing surface is cross-mesh, easy to store oil, and will not be easy to wear, easy to heat and burn phenomenon during grinding.

10. Super-precision NSK bearings have more complicated trajectories and can be transferred from grinding to grinding, which can reduce surface roughness faster. However, due to its repeated changes in the direction of motion, it affects the quality of the machined surface.

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SKF bearing limit speed problem and noise treatment method

(1) Rolling sound of imported bearings and its control method Rolling sound is a kind of slippery continuous sound that the rolling elements roll on the raceway surface when the bearing is running. It is the unique basic of all rolling bearings. sound. 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 rolling track sound decreases with the increase of viscosity; while for SKF bearings with small rolling sound, the sound pressure level is reduced when the viscosity increases to above 20 mm2/s. Turned to 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 of controlling the rolling sound is to select a low-noise 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.

(2) Impact sound of rolling element and its control method When the larger type of ball bearing or cylindrical roller bearing runs at low speed under pure radial load, the rolling element in the non-load area will be small due to the small centrifugal force of the rolling element. Noise is generated by impacting the cage or raceway. 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 a bearing having a reasonable structure and a flexible material.

(3) Bearing rolling sound and its control method Rolling sound is a harsh metal friction sound that can occur in cylindrical roller bearings in all occasions, mostly in the grease-lubricated larger type SKF bearing, and in the base oil Greases with degraded performance are more likely to occur and hardly occur when oil is lubricated. In addition, it is more likely to occur in winter. When subjected to pure radial load, it is easy to occur in the case of large radial clearance, and it is easy to occur in a certain speed range depending on the size of the model, and it will occur continuously. It will appear intermittently. Special processing methods for the outer ring raceway can prevent the occurrence of rolling noise. If necessary, the bearing can be selected, or the radial clearance of the bearing can be appropriately reduced, and the grease with excellent performance and the rigidity of the bearing device can be improved. .

Bearing lubrication methods are broadly classified into grease lubrication and oil lubrication. To fully utilize the bearing function, it is important to use the lubrication method for the purpose of reduction and use. Table 4-2 shows the advantages and disadvantages of grease lubrication and oil lubrication. Third, grease lubrication Grease is a lubricant composed of base oil, thickener and additives. When choosing, you should choose the oil that is very suitable for the bearing conditions. The trademarks will be different, and the performance will be very different. When choosing, you must pay attention.

Common 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 SKF bearing is suitable for filling the inner space of the bearing by 1/2-1/3. It should be reduced to 1/3 at high speed. Excessive grease will increase the temperature rise. Fourth, the choice of grease When the working temperature is selected grease, the main indicators should be the dropping point, oxidation stability and low temperature performance, the dropping point can generally be used to evaluate the high temperature performance, the actual working temperature of the bearing should be lower than the dropping point of 10-20 °C. Synthetic grease should be used at a temperature below the drop point of 20-30 °C.

When selecting the grease for the bearing load, the small grease should be selected for the heavy load. When working under high pressure, in addition to the small penetration, it also has higher oil film strength and extreme pressure performance.

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What are the common SKF bearing lubrication methods?

SKF bearings are lubricated in several ways, and each type of bearing and each type of bearing is also different when using lubrication, which is more conducive to maximizing the service life of SKF bearings, which is the highest performance of mechanical equipment. The state of performance.

1, solid lubrication

Under some special conditions, a small amount of solid lubricant is added to the grease. For example, adding 3~5% of molybdenum disulfide No. 1 can reduce wear and improve the resistance to pressure and heat. For high temperature, elegance, high vacuum and corrosion resistance. Special conditions such as anti-radiation and extremely low temperature, the solid lubricant can be added into engineering plastics or powder metallurgy materials to make bearing parts with self-lubricating properties, such as bonding the solid lubricant to the raceway with an adhesive. A lubricating film is formed on the cage and the rolling elements, which has a certain effect on reducing friction and wear.

2, oil lubrication:

Viscosity is an important characteristic of lubricating oil. The viscosity directly affects the fluidity of lubricating oil and the thickness of oil film formed between friction surfaces. The viscosity of lubricating oil at SKF bearing working temperature is generally 12-15cst. The higher the speed, the lower the viscosity, and the heavier the load, the higher the viscosity. Commonly used lubricating oils include mechanical oil, high-speed mechanical oil, turbine oil, compressor oil, transformer oil, cylinder oil, and the like.

Oil lubrication methods include:

a. oil bath lubrication

Oil bath lubrication is the most common lubrication method. It is suitable for the lubrication of low and medium speed bearings. Part of the bearing is immersed in the groove. The lubricating oil is brought up by the rotating bearing parts and then flows back to the oil groove. The oil level should be slightly lower than the minimum. The center of the rolling element.

b. drip lubrication

Drip oil lubrication is suitable for SKF bearing parts that need to supply lubricating oil quantitatively. The amount of dripping oil is generally one drop every 3-8 seconds. Excessive oil quantity will cause the bearing temperature to increase.

c. Circulating oil lubrication

The filtered oil is delivered to the bearing components by an oil pump, filtered through the lubricating oil after the bearings, and then cooled and used. Since the circulating oil can take a certain amount of heat to cool the bearing, this method is suitable for bearing parts with higher rotational speed.

d. Spray lubrication

The dry compressed air is mixed with the lubricating oil through a sprayer to form an oil mist. In the jet bearing, the air flow can effectively cool the bearing and prevent the intrusion of impurities. This method is suitable for the lubrication of high speed, high temperature bearing components.

e. Injection lubrication

The high-pressure oil is injected into the bearing through the nozzle by the oil pump, and the oil injected into the bearing flows into the oil groove through the other end of the bearing. When the SKF bearing rotates at a high speed, the rolling elements and the cage also form a gas flow at the relatively high rotation speed of the surrounding air. It is difficult to send the lubricating oil to the bearing by the general lubrication method. At this time, the lubricating oil must be used by the high-pressure injection method. Spray into the bearing and the nozzle should be placed between the inner ring and the center of the cage.

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The important role of SKF non-standard bearing lubrication in the elimination of the guide

In general, non-standard bearings heat up after they start running, and after a period of time, they are at a lower temperature (usually 10 to 40 degrees higher than room temperature). The normal time is different depending on the size, form, rotation speed, lubrication method of the SKF bearing, and the exothermic conditions around the non-standard bearing. It takes about 20 minutes to several hours.

When the temperature of the non-standard bearing does not reach the normal state and the abnormal temperature rises, the following reasons may be considered. In addition, the machine should be stopped as soon as possible and necessary countermeasures should be taken. Temperature is essential for maintaining the proper life of non-standard bearings and preventing deterioration of lubricating oil. It is recommended to use as much as possible under non-high temperature conditions (generally below 100 degrees). The main cause of abnormal temperature rise is too much or too little. Poor installation of SKF bearings. The internal clearance of non-standard bearings is too small, or the load is too large. The friction of the seal is too large. The lubricant does not match. The creep of the mating surface.

1. Firstly, the parts of the SKF bearing are lubricated to reduce the friction and wear of the bearing;

2. The rolling contact surface of the bearing often forms an appropriate oil film to prolong the fatigue life of the non-standard bearing;

3. The heat generated by friction or other reasons inside the bearing is removed by lubrication;

4. Through lubrication, it can achieve anti-rust and dust-proof effects on non-standard bearings.

Therefore, we must correctly understand the importance of lubrication for SKF bearings, improve bearing performance and reduce consumption.

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