Machine tool spindle bearing types are usually: deep groove ball bearings, angular contact ball bearings, thrust angular contact ball bearings, double row cylindrical roller bearings and tapered roller bearings.
Most deep groove ball bearings only bear radial loads, and are usually used in common drilling machine spindles and other equipment that do not require high precision and preload.
Angular contact ball bearings which can simultaneously withstand radial and axial load force, need to be combined in pairs to use, can be preloaded to improve the spindle stiffness. Its contact angle is usually 15°, 25°, 40° three, for example: B7000CY type high-precision angular contact ball bearing contact angle is 15 °, can be applied to high-speed grinding machine spindle, with high rotational accuracy and high speed, low friction, low temperature rise of excellent performance.
Type 230000 bi-directional thrust angular contact ball bearing, its contact angle is 60°, able to adjust the required preload of the bearing by the height of the spacer. It can bear two-way axial load, with high rigidity, low temperature rise, high speed, easy to install and dismantle the characteristics, usually used in grinding machines, lathes, drilling machines and other machine tool spindle components.
Double row cylindrical roller bearings commonly used types are: NN30/W33, NN30K/W33 series bearings and NNU49/W33, NNU49K/W33 series bearings.
Tapered roller bearings can also be good to bear radial load and axial load, if it is a double row tapered roller bearings also have can bear two-way axial load capacity.
The limit speed of tapered roller bearings is lower than that of cylindrical roller bearings of the same size. Hollow tapered roller bearings using oil-cooled rollers, temperature rise is lower, higher speed. However, the manufacturing process is complex and the lubrication system requirements are high when using them, so they are usually only used in the spindles of special horizontal machine tools.
The development of machine tool industry in heavy industry is extremely rapid, which virtually drives the development of chain industry. As an important part of machine tool spindle, how to refer to the standard
With the development of science and technology, the speed of machine tool spindle is higher and higher, and the speed range is larger and larger. Therefore, the requirements for high-speed operation stability of fag imported bearings are higher and higher.
The temperature rise of fag imported bearing of machine tool spindle is an important factor limiting the speed of fag imported bearing. Generally, correct selection of fag imported bearing type, tolerance grade, configuration mode, clearance (preload), lubricant and lubrication mode can improve the high-speed performance of rolling fag imported bearing to a certain extent.Selection standard of fag imported machine tool spindle bearing
Service life and bearing capacity spindle bearing
For general machine tools, the service life of the spindle assembly mainly refers to the service life of maintaining the spindle accuracy. Therefore, the accuracy maintenance performance of fag imported bearings is required to meet the requirements of the service life of the spindle assembly. For heavy machine tools or power cutting machine tools, the bearing capacity of fag imported bearings should be considered first.Selection standard of fag imported machine tool spindle bearing
Stiffness and vibration resistance spindle bearing
In order to ensure the machining quality of the machine tool, the spindle system must be rigid enough, otherwise it will produce large re mapping error and even flutter. Vibration resistance refers to the ability to resist forced vibration and self-excited vibration. Selection standard of fag imported machine tool spindle bearing
The vibration resistance of the spindle assembly depends on the stiffness and damping of the spindle and fag imported bearings. The use of preloaded rolling fag imported bearings can effectively improve the stiffness of the spindle system.Selection standard of fag imported machine tool spindle bearing
In high-speed grinding machine, the noise of fag imported bearing of grinding head is the main component of the noise of the whole machine, and low-noise rolling fag imported bearing should be selected.Selection standard of fag imported machine tool spindle bearing
Characteristics and application of fag imported bearing oil for main shaft
Fag imported bearing oil of spindle is a special lubricating oil for fag imported bearings of precision machine tools and similar equipment. It plays a very important role in ensuring the working accuracy and service performance of spindle and prolonging its service life. It is also called fag imported bearing oil.Selection standard of fag imported machine tool spindle bearing
Its main performance:spindle bearing
Proper viscosity and good viscosity temperature characteristics
In order to prevent the spindle temperature of the machine tool from being too high and causing thermal deformation of the machine tool, affecting the machining accuracy or poor lubrication of the fag inlet bearing, select the lubricating oil with appropriate temperature according to the structure.Selection standard of fag imported machine tool spindle bearing
speed and clearance of the fag inlet bearing of the spindle, and require it to have good viscosity temperature characteristics, so as to prevent the lubricating performance from being affected by the excessive change of viscosity when the working temperature and ambient temperature of the spindle change greatly.Selection standard of fag imported machine tool spindle bearing
Good lubricity
In order to keep a uniform oil film between the main shaft and the fag inlet bearing contact surface, and the oil film will not be damaged when the main shaft starts or stops moving to produce impact load, and maintain good lubrication performance, which plays the role of reducing friction and friction heat, reducing the temperature rise of the main shaft and ensuring the machining accuracy, it is required to have good lubrication performance.Selection standard of fag imported machine tool spindle bearing
Good oxidation resistance
When circulating lubrication is adopted for the spindle of the machine tool, the fag imported bearing oil of the spindle is required to be used for a long time without deterioration, so it is required to have good oxidation resistance.Selection standard of fag imported machine tool spindle bearing
Good rust resistance
Because the oil will inevitably mix with condensed water in the air or machine tool coolant during the operation of the spindle lubrication system, the oil is required to have good rust resistance
Selection standard of fag imported machine tool spindle bearing
The quality of heat treatment and quenching of IKO bearing parts mainly depends on the quenching heating conditions and cooling conditions, and the cooling conditions mainly depend on the selection of corresponding quenching oil and cooling technology.Selection standard of fag imported machine tool spindle bearing
IKO bearing parts are mainly quenched and cooled with mineral oil. Mineral oil is composed of paraffin, bad alkane, aromatic hydrocarbon, paraffin aromatic series hydrogen talking compounds and their derivatives. Due to different composition and refining methods, special quenching oils with different characteristics and different uses are formed. Selection standard of fag imported machine tool spindle bearing
According to the use requirements (including cooling speed, service temperature, brightness, etc.), it can be divided into ordinary quenching oil, fast quenching oil, overspeed quenching oil, graded quenching oil, vacuum quenching oil, fast bright quenching oil and mechanical oil.Selection standard of fag imported machine tool spindle bearing
When selecting quenching oil, factors such as material, shape, size, deformation, hardening layer depth, process, brightness and heat treatment equipment of parts to be treated must be fully considered. Excellent quenching oil is made of refined base oil with high thermal stability (generally paraffin base) and various additives that can improve service performance and service life.
For rolling IKO bearing parts, during quenching and cooling, the transformation of pearlite type shall be prevented to avoid opaque quenching or local defects such as troostite and soft spots.Selection standard of fag imported machine tool spindle bearing
Therefore, the cooling rate of quenching oil should be greater than the critical cooling rate of IKO bearing steel. However, the cooling speed should not be too large, so as not to cause large internal stress, resulting in cracking and excessive quenching deformation. Selection standard of fag imported machine tool spindle bearing
According to the C curve, the austenite transformation temperature of gcr15iko bearing steel is about 650 ℃ and 450 ℃. Selection standard of fag imported machine tool spindle bearing
Before this temperature, it must be cooled quickly, but at the later temperature, it can be cooled slowly, especially between the starting point of martensite transformation MS and MF. Slow cooling can reduce deformation and cracks, but it can not be too slow. Otherwise, the stable aging of austenite is easy to cause the increase of residual austenite.Selection standard of fag imported machine tool spindle bearing
Therefore, the cooling rate can be higher than the critical cooling rate at 650 ℃ and 450 ℃, and the oil with slow cooling rate after this temperature is quenching oil Under normal conditions, it is difficult to determine the critical cooling rate of steel under various conditions due to different field conditions.Selection standard of fag imported machine tool spindle bearing
However, in the field, the change trend of critical cooling rate can be judged according to the factors affecting the critical cooling rate, and the quenching oil can be selected accordingly If the quenching temperature is high, the holding time is long, and the original structure is fine, the critical cooling speed will be smaller, which is the quenching oil with small cooling capacity.Selection standard of fag imported machine tool spindle bearing
For IKO bearing rings with large wall thickness, if sufficient hardening layer is obtained, the quenching oil should have a faster cooling rate. For thin-walled IKO bearing rings, the quenching oil should have a slower cooling rate. For parts with complex shapes, quenching oil with short steam film stage and fast cooling speed should be selected.Selection standard of fag imported machine tool spindle bearing
For IKO bearing rings requiring small deformation, graded quenching oil shall be selected. If the grading temperature of IKO bearing steel ring is above MS point, the cooling speed reaches the critical cooling speed.Selection standard of fag imported machine tool spindle bearing
Vibration behavior spindle bearing
Generally speaking, the world’s imported bearings such as imported bearings will not be excited. Once that happens. Then we should check it carefully.Selection standard of fag imported machine tool spindle bearing
Excitation caused by the change of the number of loaded rolling elements
When a radial load is loaded on an inlet bearing, the number of rolling elements bearing the load will change slightly during operation, that is, this causes the deviation of the load direction. The resulting vibration is inevitable, but can be reduced by axial preloading, which is applied to all rolling elements (not applicable to cylindrical roller bearings).Selection standard of fag imported machine tool spindle bearing
Waviness of components
When the imported bearing ring is closely matched with the imported bearing seat or transmission shaft, the imported bearing ring may be deformed by matching with the shape of adjacent components. If deformation occurs, vibration may occur during operation. Therefore, it is important to machine the imported bearing pedestal and transmission shaft to the required tolerance.Selection standard of fag imported machine tool spindle bearing
Local damage
Due to incorrect operation or installation, a small number of inlet bearing raceways and rolling elements may be damaged. During operation, rolling over the damaged inlet bearing components will produce a specific vibration frequency. Vibration frequency analysis can identify damaged imported bearing components.Selection standard of fag imported machine tool spindle bearing
In many applications, the stiffness of imported bearings is the same as that of surrounding structures. As long as the bearing preload is selected correctly, it is possible to reduce the bearing preload and its application.Selection standard of fag imported machine tool spindle bearing
There are three ways to reduce the vibration of imported bearings
Remove critical excitation vibration from application; Restraining the critical excitation vibration between the excitation part and the resonance part; Change the stiffness of the structure, so as to change the critical frequency.
The friction of Koyo bearing is mainly composed of rolling friction and sliding friction between rolling element and ring raceway; Sliding friction between cage and rolling element and ferrule surface (sliding friction between rolling elements without cage); Selection standard of fag imported machine tool spindle bearing
The sliding friction between the end face of the roller and the retaining surface of the ferrule; Viscous resistance of lubricant; The sealing device is composed of sliding friction and other aspects, and its size depends on Koyo bearing type, size, load, speed, lubrication, sealing and other factors.Selection standard of fag imported machine tool spindle bearing
Deep groove ball bearings, cylindrical roller bearings and self-aligning ball bearings are usually used in instruments and machinery requiring low friction torque to bear radial load; Single row thrust ball bearing is selected to bear the radial load of Koyo bearing.Selection standard of fag imported machine tool spindle bearing
If it bears combined load, angular contact ball bearing can be selected. When the load angle is basically the same as the contact angle, small friction torque can be obtained; If the gap between the two angles is too large, centripetal and thrust bearing assembly can be used to solve it.Selection standard of fag imported machine tool spindle bearing
When Koyo bearing with low friction torque is selected, contact sealing device shall be avoided in structural design. At the same time, for Koyo bearings with low friction torque, oil drop lubrication, oil mist lubrication and oil air lubrication should be adopted. For novices who just use fag bearings, they often have no experience. Selection standard of fag imported machine tool spindle bearing
I don’t know how to check the purchased fag bearing. The following is a rough introduction to the method of checking fag bearings.Selection standard of fag imported machine tool spindle bearing
Observation method. Observe the rolling fag bearing with naked eyes. The inner and outer raceways shall be free of peeling marks and serious wear, and shall be in the shape of an arc groove; The surface of all rolling elements shall be free of spots, cracks and peeling; The cage shall not be loose, damaged or worn through, and the gap with the rolling element shall not be large.Selection standard of fag imported machine tool spindle bearing
Hand feeling method. The clearance between the inner and outer race of normal fag bearing and the rolling element is 0.005 ~ 0.010 mm. For the rolling fag bearing that has been used for one stage, there shall be no obvious vibration sound when holding the inner race with your fingers for axial shaking.Selection standard of fag imported machine tool spindle bearing
Rotation method. Hold the fag bearing inner race with one hand and rotate the outer race with the other hand. The fag bearing shall be able to rotate flexibly without radial shaking.Selection standard of fag imported machine tool spindle bearing
During inspection, the above three empirical methods shall be combined to make a correct judgment on the technical state of rolling fag bearing. For tapered roller fag bearings, also observe whether the rolling element is located in the middle of the outer race. If it moves forward, it shall not exceed 1.5mm.Selection standard of fag imported machine tool spindle bearing
s the world’s NSK bearing, it is widely used. Each industry has different characteristics of damage. Let’s take a look at the damage characteristics of engine sliding NSK bearing.Selection standard of fag imported machine tool spindle bearing
Mechanical damage
The mechanical damage of sliding NSK bearing refers to the groove marks in different degrees on the alloy surface of bearing bush. In serious cases, metal peeling and large-area random scratch occur on the contact surface; Generally, contact surface damage and ablation exist at the same time. The main reason for the mechanical damage of NSK bearing is that it is difficult to form oil film on the surface of NSK bearing or the oil film is seriously damaged.Selection standard of fag imported machine tool spindle bearing
NSK bearing cavitation
Under the repeated action of cylinder pressure (impact load), the surface layer of sliding NSK bearing has plastic deformation and cold work hardening, locally loses its deformation ability, gradually forms wrinkles and expands continuously, and then forms cavities in the loaded surface layer with the falling off of wear debris. Generally, when the bearing bush is pitted, the pit first appears, and then the pit gradually expands and causes the cracking of the alloy layer interface. Selection standard of fag imported machine tool spindle bearing
The crack extends along the parallel direction of the interface until it peels off. The main reason for cavitation of sliding NSK bearing is that the sudden change of the cross section of structural elements such as oil groove and oil hole causes strong disorder of oil flow, forming bubbles in the vacuum area with disordered oil flow, and then cavitation occurs due to the collapse of bubbles due to the increase of pressure. Cavitation usually occurs in the high load area of NSK bearing, such as the lower bearing bush of crankshaft main NSK bearing.Selection standard of fag imported machine tool spindle bearing
fatigue pitting
Fatigue pitting corrosion of NSK bearing refers to the fatigue damage, fatigue pitting corrosion or fatigue falling off in the middle of NSK bearing caused by overheating of NSK bearing and excessive clearance of NSK bearing due to overload operation of engine. This damage is mostly caused by overload, too large NSK bearing clearance, or unclean lubricating oil and foreign matters mixed in it.
Therefore, attention should be paid to avoid overload operation of NSK bearing during use, and do not operate at too low or too high speed; Adjust the engine to a stable state at idle speed; Ensure the normal NSK bearing clearance and prevent the engine speed from being too high or too low; Check and adjust the working condition of the cooling system to ensure that the working temperature of the engine is appropriate.Selection standard of fag imported machine tool spindle bearing
NSK bearing alloy corrosion
NSK bearing alloy corrosion is generally caused by impure lubricating oil. The chemical impurities (acid oxides, etc.) in the lubricating oil oxidize the NSK bearing alloy to form acidic substances, causing part of the NSK bearing alloy to fall off and form irregular small cracks or pits. The main causes of NSK bearing alloy corrosion are improper selection of lubricating oil, poor corrosion resistance of NSK bearing materials, or rough engine operation and high temperature.Selection standard of fag imported machine tool spindle bearingSelection standard of fag imported machine tool spindle bearing
NSK bearing melting
There is a small convex metal surface between the journal and the NSK bearing friction pair, which forms a local high temperature. Under the condition of insufficient lubrication and poor cooling, the NSK bearing alloy blackens or burns locally. This fault is often caused by too tight fit between journal and NSK bearing; Insufficient lubricating oil pressure is also easy to burn NSK Bearings.Selection standard of fag imported machine tool spindle bearing
NSK bearing outer circle
The outer circle of NSK bearing means that NSK bearing has relative rotation in the seat hole. After the NSK bearing goes through the outer circle, it will not only affect the heat dissipation of the NSK bearing, which is easy to ablate the alloy on the inner surface of the NSK bearing, but also damage the back of the NSK bearing and burn the NSK bearing in serious cases. The main reason is that NSK bearing is too short, tenon damage, processing or installation does not meet the specifications, etc.Selection standard of fag imported machine tool spindle bearing
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