Technical introduction of high speed spindle bearings for machine tools

Technical introduction of high-speed spindle bearings for machine tools (machine tool bearings):

Increasing the speed of the spindle bearings is the key to achieving a high-speed, practical spindle. With the development of high speed, it is efficient for machining machine tools. The rolling element is made of ceramic material, the dmN value is about 20×104, and the numerical control machining center with dmN value of 100×104 under grease lubrication condition is increasing day by day. It has become a development trend, and the oil and oil mist lubrication method will become the future. The development direction of high-speed machine tool spindle bearing lubrication.

1 high-speed spindle bearing development:

Generally, angular contact ball bearings with excellent rigidity and high speed performance are used, in order to meet the high speed requirements of the machine tool spindle. Secondly, cylindrical roller bearings are used.

The dmN value under grease lubrication conditions is 50×104 or less. After the development of oil and gas lubrication, at the same time, gradually develop a compatible lubrication system. From the dmN value of the high-speed performance of the spindle bearing (dm is the diameter of the bearing pitch circle mm × N is the speed r / min. The dmN value has reached 100 × 104 or more. Later, in the bearing, the angle of the rolling element is ceramic Contact ball bearings, after the dmN value of 200 × 104 × 90 years developed spray lubrication, dmN value can reach 300 × 104.

2 high speed spindle bearing technology:

(1) High-speed angular contact ball bearings:

Single row and double row cylindrical roller bearings are inferior to angular contact ball bearings in terms of high speed performance. Angular contact bearings are bearings with contact angles, and tapered roller bearings can be seen. The larger the contact angle, the better the axial stiffness, but since the gyro sliding and the spin sliding between the ball and the raceway are also large, the heat is also increased. In order to improve the speed performance, the method is to reduce the size (or mass) of the ball to change the curvature coefficient of the channel, to reduce the centrifugal force of the ball, reduce the internal load generated during high-speed operation, and increase the number of balls to increase the rigidity.

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Teach you a few practical tips for fault diagnosis of rolling bearings

Rolling bearings are widely used in equipment. The condition of rolling bearings is directly related to the operating state of rotating equipment. Especially in large-scale continuous production enterprises, it is widely used in important parts of large-scale rotating equipment. Therefore, in actual production, the rolling bearing condition monitoring and Fault diagnosis is an important part of equipment maintenance and management. After long-term practice and exploration, we have accumulated some practical skills for the actual fault diagnosis of rolling bearings.

First, the method and key points of rolling bearing fault diagnosis

A practical method for condition monitoring and fault diagnosis of rolling bearings is vibration analysis.

In practice, you need to pay attention to the location and acquisition method of the measuring point. In order to accurately and accurately reflect the vibration state of the rolling bearing, it must be noted that the collected signal is accurate and true. Therefore, the measuring point should be arranged in the nearest place to the bearing. Generally, there is a rear fan cover at the free end of the motor, and the measuring point is selected in the fan cover fixing screw. Good monitoring results. In addition, it is necessary to pay attention to the multiple acquisition and analysis of the vibration signal, and comprehensively compare. To get an accurate conclusion.

Second, the characteristics of rolling bearings normal operation and practical diagnostic techniques

In the long-term production status monitoring, we found that the rolling bearing showed strong regularity during its use and the repeatability was very good. Normal high-quality bearings are relatively small in vibration and noise at the beginning of use, but the spectrum is somewhat scattered and the amplitude is small, which may be due to some defects in the manufacturing process, such as surface burrs.

After a period of motion, the vibration and noise are maintained at a certain level, and the spectrum is very single, only one or two times the frequency. There are very few spectrums above the power frequency, and the bearing status is very stable and enters a stable working period.

After continuing to run, the bearing vibration and noise begin to increase, and sometimes abnormal sounds occur, but the vibration increase changes slowly. At this time, the bearing kurtness value suddenly reaches a certain value. We believe that the bearing is an initial failure at this time.

At this time, it is required to closely monitor the bearing and pay close attention to its changes. After that, the bearing kurtosis value begins to drop rapidly and approaches the normal value, while the vibration and noise begin to increase significantly, and the increase rate begins to accelerate. When the vibration exceeds the vibration standard (such as ISO2372 standard), the bearing kurtosis value also begins. Rapid increase, when both the vibration standard is exceeded, and the kurtosis value also exceeds the normal value (the available kurtosis is relative to the standard), we believe that the bearing has entered the late fault production, and it is necessary to repair the equipment in time and replace the rolling bearing.

The bearing exhibits late fault characteristics to serious faults (generally bearing damage such as axle hung, burn, sand frame spalling, raceway, bead wear, etc.). The time is not more than one week. The larger the equipment capacity, the faster the speed. The shorter the interval. Therefore, in the actual rolling bearing fault diagnosis, once the late fault characteristics are found, the bearing should be judged decisively and the maintenance should be arranged as soon as possible.

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Common bearing wear failures and troubleshooting methods

        In general, if the bearing is used correctly, it can be used until the fatigue life is reached. However, there will be accidents that are prematurely damaged and cannot be used. This early damage, as opposed to fatigue life, is a quality use limit called a fault or accident. Many of them are caused by inadvertent installation, use, and lubrication, and foreign objects intruding from the outside are insufficiently studied for the thermal effects of the shaft and the outer casing.
Regarding the damage state of the bearing, such as the ferrule of the roller bearing and the jam of the rib, it may be considered as a cause of insufficient lubricant, unsuitability, defects in the oil supply structure, intrusion of foreign matter, bearing installation error, shaft deflection If the song is too big, there will be coincidences of these reasons.

Therefore, it is difficult to know the true cause of the damage by only investigating the bearing damage. However, if you know the mechanical use of the bearing, the conditions of use, the structure around the bearing, and the situation before and after the accident, combined with the damage state of the bearing and several reasons, it can prevent similar accidents from happening again.

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Several points of attention for maintaining and testing NTN bearings

1. In the process of using NTN bearings, regular cleaning is very important. How to clean the bearings accurately? When the bearing is first removed for inspection, first use the method of photography to make a good appearance record. Also, verify the amount of lubricant remaining and sample the lubricant before cleaning the bearings.
2. The cleaning of the bearing is divided into rough washing and fine washing, and the metal mesh frame can be placed on the bottom of the used container.
3. When rough washing, clean the grease or adhesive with a brush on the top of the oil. At this time, if the transfer bearing is moved in the oil, the rolling surface is damaged by foreign matter such as foreign matter.
4. When fine washing, slowly shifting the bearing in the oil, it must be forced to stop.
5. The cleaning agent used on weekdays is neutral non-aqueous diesel or petroleum, and sometimes uses warm alkaline liquid according to demand. Regardless of which cleaning agent is used, it is often necessary to filter and clean the cockroach.
6. Immediately after cleaning, apply anti-rust oil or anti-rust grease to the NTN bearing.
In order to make the imported bearings serve the mechanical operation for a longer period of time, it is necessary to perform regular inspections on the NTN bearings on a regular basis. Through the inspection, the problems caused by the mechanical operation can be effectively found, and the problems can be solved satisfactorily. Increased bearing life.
At the time of inspection, it is mainly correct to observe whether the rivet head of the bearing is skewed or loosely welded. The welding of the cage is good or bad. Whether the solder joint is too small, there is a problem that the solder is not strong, or the ball is caused by excessive soldering. They are all special places to pay attention to when testing imported bearings. There are still some issues to be aware of.
Local inspection of the bearing. First of all, the inspection of imported bearings in the environment should be carried out in a light environment, preferably astigmatism, in order to better observe the outside of the bearing and see that there are no cracks and other abnormalities on the surface. For example, wear, scratches and bumps in the mechanical cloud process can cause the bearing device to shift, resulting in poor position of the device, causing flat load and stress concentration, and the accuracy and service life of the molded bearing are reduced.
In addition, the working environment also pays special attention to moisture or contaminants, which are most likely to cause the bearing to rust. The rust is caused by poor installation of the NTN bearing, and early wear and tear, and the bearing will be directly scrapped. Therefore, pay special attention to waterproof and moisture during use.

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The effect of grease on the service life of KOYO bearings

    The use factors mainly refer to whether the installation adjustment, use and maintenance, maintenance and repair, etc. meet the technical requirements. According to the technical requirements of KOYO bearing installation, use, maintenance and maintenance, monitor and check the load, speed, working temperature, vibration, noise and lubrication conditions of the bearing in operation, find out the cause and immediately adjust the cause, make adjustment It returned to normal. The installation condition is one of the primary factors in the use factor. The bearing is often changed due to improper installation, and the force state between the parts of the whole bearing changes. The bearing is operating in an abnormal state and the end of the service life is early. Refers to the three major factors that determine the quality of the bearing, such as structural design, manufacturing process and material quality.
    The metallurgical quality of imported bearing materials was once the main factor affecting the early failure of rolling bearings. With the advancement of metallurgical technologies (such as vacuum degassing of bearing steels), the quality of raw materials has improved. The proportion of raw material quality factors in bearing failure analysis has dropped significantly, but it is still one of the main factors affecting bearing failure. The proper selection of materials is still a factor that must be considered in bearing failure analysis.
    Bearings are generally manufactured through multiple processes such as forging, heat treatment, turning, grinding and assembly. The rationality, advancement and stability of each processing technology will also affect the life of the bearing. The heat treatment and grinding processes that affect the quality of the finished bearing often have a more direct relationship with the failure of the bearing. In recent years, research on the metamorphic layer of bearing working surface shows that the grinding process is closely related to the bearing surface quality.
The main task of KOYO bearing service life analysis is to find out the main factors causing bearing failure based on a large amount of background materials, analysis data and failure modes, so as to propose improvement measures in a targeted manner, prolong the service life of bearings and avoid bearing protrusion. Early failure of the hair.
    In general, the grease filling amount in the KOYO bearing always exceeds the actual required amount of direct participation in lubrication, in the cavity of the holder and the bearing cover, and forms a contour on the periphery of the rolling element. During this process, the bearing temperature rises rapidly due to the resistance of the excess grease. Although most of the excess grease is squeezed out at the beginning of the run, the grease that is squeezed into the raceway attachment may still be carried by the rolling element into the raceway. In the early stages of bearing operation, most of the grease is squeezed out of the raceway very quickly (less than a minute), and the build-up grease is discharged a small amount while circulating along with the bearing rotor. At this time, the bearing temperature continues to rise until the excess bearing grease is completely discharged, which can be called the walking phase of the grease. According to the grease quality and filling amount in the bearing structure, this time may last for more than ten. Minutes, even hours.
After the remaining KOYO bearing grease is completely discharged, the remaining small amount of grease forms a thin layer of grease film on the mutual contact surface of the rolling element, the raceway and the cage, thereby entering the normal bearing. Operational phase. At this time, the temperature gradually drops and reaches equilibrium. In other words, long-term lubrication is mainly borne by this layer of grease film. In addition, during the long-term operation of the bearing, the contour of the rolling element and the raceway and the grease on the cage are shrunk to separate a part of the base oil, and after flowing into the raceway, the lubrication is also supplemented.

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How to clean imported bearings

Core Tip: Regular cleaning is very important in the process of using imported bearings. So how to properly clean the imported bearings? Let me introduce it to you. When the imported bearings are removed for inspection
Regular cleaning is very important in the process of using imported bearings. So how to properly clean the imported bearings? Let me introduce it to you.

    When the imported bearings are removed for inspection, the appearance records are first recorded by photography. Also, verify the amount of lubricant remaining and sample the lubricant before cleaning the bearings.


    The cleaning of the bearings is carried out by rough washing and fine washing, and a metal mesh frame can be placed on the bottom of the used container.

    When rough washing, remove grease or adhesive with a brush or the like in the oil. At this time, if the bearing is rotated in the oil, be careful that the rolling surface will be damaged by foreign matter or the like.

    When cleaning, the bearing is slowly rotated in the oil and must be carefully carried out.

    The cleaning agent generally used is a neutral non-aqueous diesel oil or kerosene, and a warm alkali liquid or the like is sometimes used as needed. Regardless of which cleaning agent is used, it is often filtered and kept clean.


    Immediately after cleaning, apply anti-rust oil or anti-rust grease to the imported bearings.

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The specific reasons for the failure of imported bearings

Core Tip: The cause of the failure of imported bearings is often multi-factor. The influencing factors of all design and manufacturing processes will be related to the failure of imported bearings, and it is difficult to judge by analysis. In general, large
The reasons for the failure of imported bearings are often multi-factorial. The influencing factors of all design and manufacturing processes will be related to the failure of imported bearings, and it is difficult to judge by analysis. In general, it can be considered and analyzed in terms of both usage factors and internal factors.

    The use factors mainly refer to whether the installation adjustment, use and maintenance, maintenance and repair, etc. meet the technical requirements. The installation condition is one of the primary factors in the use factor. The imported bearing is often changed due to improper installation, and the force state between the parts of the whole bearing changes, and the bearing runs in an abnormal state and fails early. According to the technical requirements for the installation, use, maintenance and maintenance of imported bearings, monitor and check the load, speed, working temperature, vibration, noise and lubrication conditions of the bearing in operation, find the cause and find the cause immediately, and make adjustments. It returned to normal. In addition, it is important to analyze the quality of the grease and the surrounding medium and atmosphere.

    The internal factors mainly refer to the three major factors that determine the quality of imported bearings, such as structural design, manufacturing process and material quality.

    First of all, the structural design is reasonable and advanced, so that it will have a long bearing life. Bearings are generally manufactured through multiple processes such as forging, heat treatment, turning, grinding and assembly. The rationality, advancement and stability of each processing technology will also affect the life of the bearing. The heat treatment and grinding processes that affect the quality of the finished bearing often have a more direct relationship with the failure of the bearing. In recent years, research on the metamorphic layer of bearing working surface shows that the grinding process is closely related to the bearing surface quality.

    The metallurgical quality of imported bearing materials was once the main factor affecting the early failure of rolling bearings. With the advancement of metallurgical technologies (such as vacuum degassing of bearing steels), the quality of raw materials has improved. The proportion of raw material quality factors in bearing failure analysis has dropped significantly, but it is still one of the main factors affecting bearing failure. The proper selection of materials is still a factor that must be considered in bearing failure analysis.

    The main task of the failure analysis of imported bearings is to find out the main factors causing bearing failure based on a large amount of background materials, analysis data and failure modes, so as to propose improvement measures in a targeted manner, prolong the service life of bearings and avoid sudden occurrence of bearings. Early failure of sex.

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Bearing heat treatment method in foreign machinery industry (below)

Core Tip: Bearing heat treatment method in foreign machinery industry (below) Abstract: Revitalize the industry position of equipment manufacturing industry Safe and environmentally controlled microbial growth A/B rotary working head inverter brake
Bearing heat treatment method in foreign machinery industry (below) Abstract: Revitalizing the industry status of equipment manufacturing industry Safe and environmentally controlled microbial growth A/B rotary working head Inverter braking new ideas, new methods Longitudinal wave method flaw detection quantitative analysis uncertainty High-precision milling processing technology and numerical control programming example High-performance grinding wheel dresser design and application High-efficiency CNC grinding AutoCAD-based planning library management system design and implementation Metal cutting new concept and soft soft starter energy saving principle CNC machine tool installation and commissioning CNC machine tools go to the information age Dalian has made breakthroughs in the research and development of cutting-edge CNC equipment. Metal cutting principle and tool vibration aging process principle Historical status and development trend of stainless steel electrode research at home and abroad Standard programming language CNC machine tool system composition and function processing method industry machinery foreign atmosphere cleaning equipment bearing cooling bearing heat treatment equipment 7.1 annealing equipment industrial developed countries as early as the 1960s and 1970s, the promotion of putter type roller-type isothermal spheroidizing furnace Shrink Annealing cycle annealing to improve the quality of energy saving bearing parts processing technology precision forging precision ring rolling process using parts rough machining precision turning technology to bring more and gradually extended protective atmosphere annealing needs of industrialized countries.

7 bearing heat treatment equipment

7.1 Annealing equipment

In the industrialized countries, as early as the 1960s and 1970s, push-rod and roller-type isothermal spheroidizing annealing furnaces were widely promoted to shorten the annealing cycle, save energy and improve annealing quality. With the development of bearing parts processing technology, precision forging and precision 辗 expansion (cold 辗) process, the processing precision of parts blanks is getting higher and higher, and gradually no less turning process is introduced, which brings about annealing of protective atmosphere. demand. Industrial developed countries have generally adopted protective atmosphere annealing to reduce the amount of machining after annealing, improve processing efficiency, save energy and reduce costs.

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Lubrication of plain bearings

Core Tip: The role of lubricant lubricants is to reduce frictional resistance, reduce wear, cooling and vibration absorption. Lubricants are liquid, solid and gas and semi-solid. Liquid lubricants are called lubricants.
Lubricant

The role of the lubricant is to reduce frictional resistance, reduce wear, cooling and vibration absorption. Lubricants are liquid, solid and gas and semi-solid. Liquid lubricants are called lubricating oils, semi-solid, at room temperature. The grease is grease.

Lubricant

Lubricating oil is the main lubricant. The main physical property index of lubricating oil is viscosity. Viscosity characterizes the internal friction property of liquid flow. The greater the viscosity, the worse the fluidity. Another physical property of the lubricating oil is oiliness, which characterizes the adsorption capacity of the lubricating oil on the metal surface. The greater the oiliness, the stronger the adsorption capacity for the metal, and the easier the oil film is formed. The choice of lubricating oil should take into account factors such as bearing capacity, journal rotation speed, lubrication method, and surface roughness of sliding bearings.
The general principles are as follows:

1. Under high-speed and light-load working conditions, in order to reduce frictional power consumption, a lubricant with a small viscosity can be selected;
2. Under heavy or shock load working conditions, oil with large oiliness and high viscosity should be used to form a stable lubricating film;
3, static pressure or dynamic and static pressure sliding bearings can choose a small viscosity lubricant;
4. Surfaces with rough or unrunned surfaces should be selected with high viscosity lubricants.

The selection of the viscosity of the lubricating oil for hydrodynamically lubricated bearings can be checked by calculation.

Grease

For plain bearings with a journal speed of less than 1 m/s to 2 m/s, grease can be used. The grease is blended with mineral oil, various thickeners (such as calcium, sodium, lithium, aluminum and other metal soaps) and water. The grease has a large consistency (needle penetration) and a large carrying capacity, but its physical and chemical properties are unstable. It should not be used under conditions of large temperature changes, and is often used in low-speed heavy-duty or oscillating bearings.
Solid lubricants and gas lubricants

Solid lubricants include graphite, molybdenum disulfide (MoS2) and polytetrafluoroethylene (PTFE). Generally used under heavy load conditions or under high temperature working conditions. Gas lubricants are commonly used in air, and are used at high speeds and in oils or greases.

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Ntn roller bearing in use failure daily maintenance precautions

After the ntn bearing is installed, check the operation in order to check if the installation is correct. The small machine can be rotated by hand to confirm whether the rotation is smooth. The inspection items have poor operation due to foreign matter, scratches, and indentations. The installation is poor, the torque generated by the mounting is not stable, and the torque is too large due to too small clearance, installation error, and sealing friction. Wait. If there is no abnormality, the power running can be started. Large machinery cannot be rotated manually, so the power is cut off immediately after the start of the no-load, the machine is idling, and the presence or absence of vibration, noise, and contact of the rotating parts is checked. After confirming that there is no abnormality, the power is turned on. The power running starts from the no-load low speed and slowly increases to the rated operation of the specified conditions. The items to be checked during the test run are whether there is abnormal sound, change in the temperature of the roller bearing, leakage or discoloration of the lubricant, and the like. If an abnormality is found, stop the operation immediately, check the machine, and remove the bearing check if necessary.
The temperature can generally be estimated based on the external temperature of the bearing housing. However, it is more accurate to directly measure the temperature of the outer ring of the ntn bearing by using the oil hole. The bearing temperature gradually rises from the start of the operation, and the temperature is usually stable after 1 to 2 hours. If the roller bearing is poorly installed, the temperature will rise sharply and an abnormally high temperature will occur. The reasons are such as excessive lubricant, too small bearing clearance, poor installation, excessive friction of the sealing device, and the like. In the case of high-speed rotation, the selection of the structure and lubrication method is also the cause.
1) Wash the bearing with kerosene, press it into the bearing seat, fill the roller of the bearing outer ring with Shell No. 3 lithium base grease to two-thirds full, apply evenly with the net hand, install the ntn bearing gland, apply with the coating The fastening bolt of the bolt anti-slipping rubber is pressed against the bearing gland;
2) The bearing is a cylindrical roller bearing with a detachable inner casing. The bearing should be placed on the rotating shaft and placed in place;
3) Mount the bearing housing on the casing. If there is grease grease hole, it must be aligned. Pressing the bearing block with the fastening bolts of the anti-loosening rubber;
4) The inner and outer eccentric blocks are mounted on the rotating shaft and are in place. If there is an axis key, the shaft key should be inserted into the keyway and then the outer eccentric block should be installed, and the shaft can be mounted on the rotating shaft with the retaining ring;
5) Tightly fix the eccentric block fastening bolts and turn the adjustable eccentric block to the angular position before the unloading and tighten the fastening bolts. After the above assembly is completed, the shaft should have a certain axial movement;
6) The protective cover on both ends of the upper vibration motor is fastened with screws.
The imported bearings have certain changes to the installation form of the vibration motor and other aspects of the performance, and the form considered from different angles has a certain change effect, and slowly the installation situation of all aspects has also been I understand it.
The use factors mainly refer to whether the installation adjustment, use and maintenance, maintenance and repair, etc. meet the technical requirements. The installation condition is one of the primary factors in the use factor. The ntn bearing often changes the force state between the parts of the whole set of roller bearing due to improper installation, and the bearing runs in an abnormal state and fails early. According to the technical requirements of bearing installation, use, maintenance and maintenance, monitor and check the load, speed, working temperature, vibration, noise and lubrication conditions of the ntn bearing in operation, find out the cause and immediately adjust the cause, make adjustment It returned to normal. In addition, it is important to analyze the quality of the grease and the surrounding medium and atmosphere.

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Ntn tapered roller bearing to adjust the rotation accuracy of regular lubrication maintenance

After the ntn bearing is installed in the main machine, if the radial runout of the tapered roller bearing main shaft is measured, it can be found that the measured value of each revolution has a certain change; when the measurement is continuously performed, it can be found that after a certain number of revolutions, this Changes will repeat approximately. The index for measuring the degree of change is the cyclic rotation precision, and the change approximately repeats the required number of revolutions to represent the "quasi-period" of the cycle rotation accuracy. The magnitude of the magnitude change in the quasi-period is large, that is, the cycle rotation precision is poor. .
1, grease lubrication
Relubrication of ntn bearings is best carried out during planned equipment downtime and is periodically replenished, while removing old grease or extruding old grease through the drain. Wipe the grease fittings clean before adding fresh grease. If the bearing housing does not have a grease fitting, the bearing housing cover or end cap should be opened to remove the old grease and, after cleaning, replenish the same type of fresh grease.
2, lubricating oil lubrication
Regularly check the oil level and oil quality of the lubricating oil. Under normal circumstances, the normal oil level should be within the range of 1/3-2/3 of the equipment oil level window or mark. The oil filling method is oil cup, the oil level shown only represents the oil replenishing capacity, and the bearing tank oil level is to meet the operation requirements. The oil level in the oil cup is less than 1/4 of its total volume.
Check and replenish the oil method, take a small amount of lubricating oil as a sample and compare it with fresh oil. The competent unit can consider the oil quality test to ensure the oil quality is qualified. If the sample looks cloudy, it may be the result of mixing with water, which is commonly referred to as oil emulsification. At this point, the lubricant should be replaced. Installation of the fixed-end front bearing on the shaft: Thoroughly clean the tapered roller bearing with clean cleaning kerosene. For grease lubrication, firstly inject the organic solvent containing 3% to 5% grease into the ntn bearing for degreasing and cleaning. Use a grease gun to fill the bearing with a certain amount of grease (10% to 15% of the bearing space volume); heat the bearing to raise the temperature by 20 to 30 °C, load the bearing into the shaft end with a hydraulic press; press the adapter sleeve on the shaft And axially position the bearing end face with appropriate pressure; wind the belt of the spring balance on the outer ring of the bearing, and check whether the specified preload has a large change by measuring the starting torque (even if the taper rolls The sub-bearings are correct, but the preload is also subject to change due to the deformation of the fit or cage.

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