Four major categories of bearing material
1, under normal circumstances, the turntable bearing ring selection of 50Mn, but sometimes, in order to meet the special application host need to use 42CrMo.
2, the rolling body general selection of GCr15SiMn.
3, maintain the type of the type of the whole, sub - type, block type, and so on the different structure type. Integral or segmented hold for 20# steel or ZL102 cast aluminum alloy. The block type retainer is made of Polyamide 1010 resin, ZL102 cast aluminum alloy or QA110-3-1. 5 aluminum bronze.
4, sealing ring material: oil resistant rubber, fluorine rubber, oil resistant rubber. Slewing bearing clearance of slewing bearing clearance is mainly used for compensation turntable bearing parts and host is related to the assembly parts of the manufacturing error and installation error to ensure the bearing of normal use. According to slewing bearing structure type / grade of tolerance and rolling body group of pitch circle diameter, slewing bearing clearance value or given the amount of interference.
Machine tool's axis parts, especially the main shaft, generally with the rolling bearings or sliding bearing assembly into one, and with a very high speed of rotation, and sometimes it will produce a high heat. If this phenomenon is not removed in time will lead to overheating of bearing, and make appropriate machine parts of the temperature rise and thermal deformation, serious causes the spindle and tailstock unequal height, which not only affects the precision and accuracy of the machine itself and the bearing burn. The reasons for heating of the main shaft bearing and the methods of elimination are shown in Table 1.
Cause of fever of rolling bearing and its elimination method
(1) reason: bearing low accuracy
Method: the precision grade of the bearing is selected.
(2) reason: the main shaft bending or box hole is not concentric
Method: fix the spindle or box
(3) the reason: the belt is too tight
Method: adjust the belt to make the appropriate
(4) reason: poor lubrication
Method: the material of the grade of the material is selected and appropriate for cleaning.
(5) reason: low quality of assembly
Method: improve the quality of assembly
(6): bearing shell laps
Method: replacement of bearings and related wear parts
(7) axial force is too large
Method: the clearance between the 0.2 ~ 0.3mm is required to correct the balance hole diameter of the impeller and the static equilibrium value.
8) bearing damage
Method: replace bearing
Because of the wide range of types of bearings, the following will be mainly the use and selection of deep groove ball bearing for the most widely used as some analysis. I hope to know less of the bearing can deepen the understanding of the bearing.
One, bearing selection.
1, the choice of bearing type: bearing type is generally by the user's technical staff according to the conditions of use and bearing load on the bearing to choose. Business personnel are mainly about user's actual load whether with the selected bearing consistent, if the bearing is not up to the requirements, should advise the customer as soon as possible the election model, but unless special products in the choice of models generally do not have any questions.
The choice of 2, bearing clearance: user to buy Bearings generally only inform on what type, grade, rarely claim on the bearing clearance, the business people must ask clear bearing conditions of use, the running speed of the bearing, temperature, combined with tolerances are directly related to the shaft bearing clearance choice. General in the 3500 turn / points below the speed of the motor is used mostly cm clearance, such as high temperature and high speed motor requires a relatively large clearance. Bearing clearance after the assembly will because the inner hole of the swollen and round narrow and lead to a reduction, the clearance of reduce weight = over surplus quantity x 60% (the bearing chamber is aluminum, with the exception of). Such as bearing clearance before assembly is 0.01mm, assembly interference of 0.01mm, the clearance of 0.004mm bearing assembly. On the theory of bearing in the zero clearance noise and life to reach the best state, but in actual operation, taking into account issues such as temperature rise, bearing assembly clearance is 0.002mm-0.004mm better.
3, the choice of oil: oil selection is generally based on the speed of the bearing, temperature resistance, noise requirements and starting torque and other aspects of the selection, the requirements of the business to the performance of a variety of grease.
4, bearing seal type selection: bearing lubrication can be divided into oil and grease lubrication. Oil lubricated bearings are generally used in the form of bearings, grease lubricated bearings generally use the dust cover or rubber seal seal. Dust cover is suitable for high temperature or the use of good environment, sealing parts contact seal and non contact seal two, contact sealing and dust proof performance is good, but the power torque is large, non - contact seal starting torque is small, but the sealing performance is not good contact.
People of this bearing is currently in the automotive motor bearings, household electrical appliances, motor bearings, motor bearings, motor bearings and other professional manufacturing, so that the bearing of the noise and life to the best state.
Angular contact ball bearing is centripetal thrust ball bearing, the ball into the more, the radial bearing capacity is greater than that of an ordinary ball bearing, but also bear large axial load or subjected to pure axial load, which allows similar working speed and deep groove ball bearing and supporting more rigid, but requires installation of precision. The axis misalignment error is very sensitive, it is generally not alone bear radial load, while in bear radial load at the same time will bring additional axial load. Variant of many varieties of the bearing, application is very wide, often made with 15 degrees, 25 and 40 degrees contact angle three series, the larger contact angle, the axial load capacity of the higher, but at high speed to the occasion by small contact angle is appropriate.
This kind of bearing most of the pairs for Small Span Rigid double supporting shaft or the precision spindle, use to carefully adjust the clearance, the change of bearing inner ring and outer ring of the axial distance, can adjust the bearing internal clearance, at the same time will several sets of Parallel bearing installation and pre gives the amount of interference, can improve the rigidity of the bearing system.
Odd this type bearings can only bear the axial load in one direction, and the need to configure other bearing to offset the additional axial force, and installed in pairs when added axial force is offset each other, and can withstand a force to the axial load, and has two directions of the strong axial spacing, mounted in pairs generally use two sets of bearings in the outer ring of the wide end of the relative (back to back) or narrow face relative (face to face) two installation forms, including back-to-back mounting the stiffness of the bearing system is best. In order to facilitate the installation of pairs or groups, some of the bearing factory supply pairs, three sets of a set of four sets of bearings, such as the supply of the same batch of bearings processing good agreement, the use of load bearing more uniform, additional axial force to offset each other more thoroughly.
This type of bearings are separable and non separable type two, separated type bearings for installation conditions are limited, the outer ring or inner ring can be removed from the complete set of bearings for the case, due to the separation of angular contact ball bearings in magnetic motors, so also known as magnetic motor bearings. This type of bearing in the inner race of the varieties, can be adapted to higher speed.
Rolling bearings in the running process may be due to various reasons causing damage, such as improper assembly, lubrication, moisture and foreign material intrusion, corrosion and overload can lead to premature bearing damage. Even after the installation, lubrication and use of maintenance are normal, after a period of operation, the bearing will appear fatigue spalling and wear and can not work. In short, rolling bearing fault reason is very complex. The main failure forms of rolling bearings and the reasons are as follows.
1 fatigue spalling
Rolling bearings in the inner and outer rolling and rolling surfaces are subjected to load and relative rolling, due to the role of alternating load, first in the surface of a certain depth (maximum shear stress) to form a crack, and then extended to the surface of the contact surface to make the surface spalling, and finally developed to large spalling, this phenomenon is fatigue spalling. Fatigue spalling can cause impact load, vibration and noise in the running. Usually, fatigue spalling is often the main reason for the failure of rolling bearings, the general said that the bearing life is the fatigue life of bearing, bearing life test is fatigue test. Test procedure, in the rolling or rolling body appear on the area of 0.5mm2 of the fatigue spalling pit that bearing life end. The fatigue life of rolling bearings is very large. The maximum service life and the lowest life span of the same batch of bearings are the highest. The importance of fault monitoring of rolling bearing is explained from another point of view.
Due to the intrusion of dust, foreign body, raceway and rolling body relative motion will cause surface wear and lubrication will aggravate the wear, the wear results the bearing clearance increases and surface roughness is increased, reducing the running accuracy of bearing and thus reduce the motion accuracy of the machine, vibration and noise also increases. For precision mechanical bearings, it is often the amount of wear that limits the life of the bearing.
In addition, there is a micro vibration wear. In the case that the bearing is not rotated, due to the action of the vibration, the rolling element and the rolling contact surface have small, repeated relative sliding and wear.
3 plastic deformation
When the axial subjected to impact load or static load, or because of the additional load caused by thermal deformation, or have very high hardness of foreign intrusion when will in the raceway surface form dents or scratches. This will cause the bearing in the running process to produce violent vibration and noise. Once there is an indentation, the impact load caused by indentation will further cause the surface to be peeled off.
Corrosion is one of the most serious problems of rolling bearings, high precision bearings may be due to the loss of accuracy caused by surface rust and can not continue to work. Water or acid, alkaline material directly into the human will cause bearing corrosion. When the bearing to stop working, the bearing temperature dropped to the dew point, the air in the water condensation into the water droplets attached on the surface of the bearing can also cause corrosion. In addition, when the current through the bearing internal, current may through the raceway and rolling body at the contact point, a thin film of oil caused by electric spark generated electrical erosion. On the surface the formation of washboard is uneven.
High load may cause the bearing part fracture. Grinding, heat treatment and assembly will cause the residual stress, the thermal stress will cause the bearing part fracture. In addition, the assembly method, improper assembly process, may also cause the bearing ring rib and roller chamfer off block.
In poor lubrication, high speed and heavy load case work and heat due to friction, bearing parts can be in a very short period of time to reach a high temperature, resulting in surface burns and gluing. The so-called glue is a part of the surface of the metal on the surface of the metal adhesion to another part of the surface phenomenon.
7 cage damage
Due to the improper assembly or use may cause the holder to deformation, increase the friction between it and the rolling body, and even some of the rolling body stuck can not roll, but also may cause the cage and the inner and outer ring friction, etc.. This damage will further make the vibration, noise and heat increased, resulting in bearing damage.
Installation and adjustment of the low noise bearings can also follow the example of long-life bearing grouping method, makes tie had Ying with the same size, the clearance of the bearings is more consistent, and with the hope that the interference in may range from small values, in order to ensure the bearing raceway small deformation and rolling body by caused by noise.
The relationship between clearance of noise, ideal state is when the bearing is in the maximum temperature of operation state, exactly zero clearance values. Judge the clearance is too large methods: static state the shaft axial displacement, the reciprocating range is big, in the running a large and low noise.
If you hate the shrill whistle issued operation, bearing preload is too large, bearing a larger pre interference should be slightly relaxed level of pretension. If the clearance is too large, you can make the two bearing ring along the axial direction slightly relative deviation: reduces both clearance and increases the axial rigidity, can reduce the noise of the bearing.
The rolling body in no load zone will spin or left and right shifting, this would increase the noise can also cause wear, and small clearance and high axial stiffness can eliminate this phenomenon. But the clearance is not too small, so as to avoid high temperature and shorten the life of.
Sometimes due to host the operating temperature range, or shaft and a hole on the discrete size is too big, not a setting is more appropriate clearance, in this case, the bearing outer ring with elastic Preload Method.