The inspection of Timken bearing grinding should be carried out under the astigmatism lamp
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.New technology and process equipment of Timken bearing grinding.
and the appearance, cracks and other parts of NTN bearing should be carefully observed.New technology and process equipment of Timken bearing grinding
All kinds of mechanical scars, such as abrasion, scratch, crush and bruise, will cause poor installation of NTN bearing, cause eccentric load and stress concentration, and reduce the rotation accuracy and service life.New technology and process equipment of Timken bearing grinding
Rust, black skin and pitting. The latter two are defects that are easy to store moisture and dirt, which are easy to develop into rust. Corrosion is the pollution source leading to poor installation, early wear and fatigue. Serious corrosion will scrap NTN bearings.New technology and process equipment of Timken bearing grinding
Various cracks, such as raw material cracks, forging cracks, heat treatment cracks and grinding cracks, will become the source of stress concentration and expand rapidly in the future operation of NTN bearing, resulting in the rupture of NTN bearing, which has a great impact on the service life and workability of NTN bearing. In fact, NTN bearing factory has conducted 100% magnetic or radiographic inspection on its components for NTN bearings for important purposes.New technology and process equipment of Timken bearing grinding
Peeling and folding, the local combination of these two defects with the base metal is not firm, and decarburization or carbon deficiency often exist around them in varying degrees. The material is easy to collapse, dent or wear, which is very unfavorable to the service life and accuracy of NTN bearing.New technology and process equipment of Timken bearing grinding
Otherwise, it indicates that the bearing temperature is too high.
For the riveting or welding quality of the cage, mainly observe whether the rivet head is offset, skewed, loose, missing meat or “double eyelid”, whether the welding position is correct, whether the welding spot is too large or too small, and whether the rolling element is stuck due to poor welding or excessive welding
It is common for imported bearings to fail during operation, so there is no need to make a fuss. In case of failure, judgment and treatment are the key. Today we will explain the common faults of bearings and troubleshooting methods.New technology and process equipment of Timken bearing grinding
The inlet bearing temperature is too high
During the operation of the mechanism, the part where the imported bearing is installed is allowed to have a certain temperature. When touching the mechanism shell by hand, it should be normal not to feel hot. New technology and process equipment of Timken bearing grinding
The reasons for the high temperature of imported bearings are: 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); The assembly of imported bearing is too tight; The bearing race rotates on the shaft or in the shell; Excessive load; Broken imported bearing cage or rolling element, etc.New technology and process equipment of Timken bearing grinding
Noise of imported bearing
The rolling 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 imported bearing is faulty.New technology and process equipment of Timken bearing grinding
The causes of rolling bearing noise are complex. One is the wear of the mating surfaces of the inner and outer rings of imported bearings. Due to this kind of wear, the matching relationship between the imported bearing and the shell and between the imported 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. New technology and process equipment of Timken bearing grinding
When the imported bearing is tired, the metal on its surface will peel off, which will also increase the radial clearance of the imported bearing and produce abnormal noise. In addition, insufficient lubrication of imported bearings, dry friction and broken imported bearings will produce abnormal sound. After the imported bearing is worn and shaken, the cage is loose and damaged, which will also produce abnormal noise and damage to the imported bearing. What are the requirements for the installation surface and installation site?New technology and process equipment of Timken bearing grinding
No impurities can enter Timken bearing. If there are iron filings, dust and other impurities in Timken bearing, Timken bearing will produce noise and vibration during rotation, and even cause damage to raceway and rolling element, resulting in damage to Timken bearing. Therefore, before installing Timken bearing, ensure that the installation surface and installation environment are clean.New technology and process equipment of Timken bearing grinding
Timken bearing surface is coated with antirust oil. Before installation, it should be carefully cleaned with clean gasoline or kerosene, and then coated with clean and high-quality lubricating grease before installation and use. Cleanliness has a great impact on the service life and noise of Timken bearing. However, it must be specially reminded that the fully enclosed Timken bearing (Timken bearing with dust cover or sealing ring) does not need cleaning and refueling.New technology and process equipment of Timken bearing grinding
Third, how to choose lubricating grease?
The quality of lubrication seriously affects the rotation and service life of Timken bearing. The general principle of selecting grease is that grease is composed of base oil, thickener and additives. The performance of different kinds or different brands of grease of the same kind varies greatly, and the allowable limit speed is different. Pay attention to it when selecting. The performance of lubricating grease is mainly determined by the base oil. New technology and process equipment of Timken bearing grinding
Generally, the base oil with low viscosity is suitable for the environment of low temperature and high speed, and the base oil with high viscosity is suitable for the operating environment of high temperature and high load. The water resistance of thickener determines the water resistance of grease. In principle, different brands of greases cannot be mixed together, and even greases with the same thickener will have a bad impact on Timken bearings due to different additives.New technology and process equipment of Timken bearing grinding
Fourth, when lubricating Timken bearings, the more grease, the better?New technology and process equipment of Timken bearing grinding
When lubricating Timken bearings, the more grease is applied, the better. Too much grease in Timken bearing will cause excessive mixing of grease, resulting in excessive temperature. Timken bearing should be filled with 30% ~ 50% of the internal space of Timken bearing.New technology and process equipment of Timken bearing grinding
Not all service environments require Timken bearings to have a small working clearance. You must choose the appropriate clearance according to the service conditions. In the national standard 4604-93, the radial clearance of rolling Timken bearing is divided into five groups: group 2, group 0, group 3, group 4 and group 5. The clearance values are arranged from small to large, of which group 0 is the standard ordinary clearance.New technology and process equipment of Timken bearing grinding
The standard radial clearance group is suitable for general operating conditions, conventional temperature and common interference fit; Timken bearing working under special conditions such as high temperature, high speed, low noise and low friction should choose large radial clearance; New technology and process equipment of Timken bearing grinding
Timken bearings used for precision spindles and machine tool spindles should have small radial clearance. Magnetic bearing, water wave bearing, magnetic core bearing and Laifu bearing are also improved from the above two kinds of sleeve imported bearing and rolling bearing, and the working principle has not changed.New technology and process equipment of Timken bearing grinding
At present, the main imported bearings used on ordinary air-cooled radiators are oil-bearing and ball bearing.
Oil bearing
Oil bearing is a sleeve imported bearing with sliding friction. It uses lubricating oil as lubricant and drag reducer. At the beginning of use, it has low working noise and low manufacturing cost, but the imported bearing is seriously worn and its service life is much lower than that of ball bearing. Moreover, this imported bearing has been used for a long time. New technology and process equipment of Timken bearing grinding
Due to the oil seal (it is impossible for computer radiator products to use oil seal, which is generally an ordinary paper oil seal), the lubricating oil will gradually volatilize, and the dust will enter the imported bearing, resulting in problems such as reduced fan speed and increased noise. In serious cases, it will also cause severe vibration caused by fan eccentricity due to the wear of imported bearings.New technology and process equipment of Timken bearing grinding
Ball bearing
The ball bearing changes the friction mode of the imported bearing and adopts rolling friction. This mode more effectively reduces the friction resistance of the imported bearing, effectively improves the service life of the imported bearing of the fan, and therefore prolongs the service life of the radiator. The disadvantage is that the manufacturing process is more complex, resulting in higher costs.New technology and process equipment of Timken bearing grinding
Sixth, the smaller the radial clearance of Timken bearing, the better?
For the riveting or welding quality of the cage, mainly observe whether the rivet head is offset, skewed, loose Lack of meat or “Double eyelid”, whether the welding position is correct, whether the welding spot is too large or too small, whether the rolling element is stuck due to loose welding or excessive welding, whether the quality of slope pressing, edge trimming, caulking and chiseling of some cages is guaranteed, and whether the rolling element can not fall out of the cage and rotate freely.
If these points are unqualified, the noise and rotation accuracy of Timken bearing will be reduced if they are small, and the cage may be scattered and the bearing will be damaged if they are large Cause mechanical failure or accident.
Peeling and folding, the local combination of these two defects with the base metal is not strong, and decarburization or carbon deficiency often exist around them to varying degrees. The material is easy to collapse, dent or wear, which is very unfavorable to the service life and accuracy of Timken bearing.
Various cracks, such as raw material cracks, forging cracks, heat treatment cracks and grinding cracks, will become the source of stress concentration and expand rapidly in the later operation of Timken bearing, resulting in the rupture of Timken bearing, which has a great impact on the service life and workability of Timken bearing. In fact, for Timken bearings with important applications, Timken bearing factory has conducted 100% magnetic or radiographic inspection on its components.
Rust, black skin and pitting. The latter two are defects that are easy to store moisture and dirt, which are easy to develop into rust. Corrosion is the pollution source leading to poor installation, early wear and fatigue. Serious corrosion will scrap Timken bearings. Whether there is muddy oil on the surface: this should be paid special attention when purchasing NTN bearings.
Since the current domestic antirust technology is not particularly good, it is easy to leave thick oil traces when antirust the NTN bearing body, which is sticky and thick when holding it in your hand. However, there is almost no trace of antirust oil on the bearings originally imported from abroad. However, a particularly careful expert said that the imported bearings smell like a smell. It must be under antirust oil, but you can’t see it.
Whether the chamfer is uniform: the so-called chamfer of NTN bearing, that is, the junction of horizontal and vertical surfaces. Due to the limitation of production technology, the fake NTN bearing of NTN bearing is not handled satisfactorily in these corners. Whether the steel seal words are clear: brand words, labels, etc. will be printed on the NTN bearing body.
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. 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.
Whether there is any noise: hold the inner sleeve of NTN bearing with your left hand, move the outer sleeve with your right hand to rotate it, and listen to NTN bearing for 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 NTN 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
Should Timken bearings be cleaned before installation?
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.
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