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Bearings are important components in contemporary mechanical equipment. Its main function is to support the mechanical rotating body, reduce the friction coefficient during

its movement, and ensure its rotation accuracy.

New bearings aside, how do we tell if an old bearing is ready to be used again?

First of all, carefully investigate and record the removed bearing and its appearance, clarify and investigate the remaining amount of lubricant, and carefully clean the

bearing after sampling.

Secondly, check the condition of the raceway surface, rolling surface and mating surface, as well as the wear status of the cage, etc. for damage and abnormalities.

To determine whether a bearing can be used again, the decision must be made after considering the degree of bearing damage, machine performance, importance, operating

conditions, and inspection intervals.

If damage or abnormality is found in the bearing, the cause should be identified promptly and countermeasures should be formulated. If the inspection results show the

following defects, the bearing can no longer be used and needs to be replaced with a new one.

1. There are cracks and fragments in any of the inner and outer rings, rolling elements, and cages.
2. Any of the inner and outer rings or rolling elements is peeled off.
3. The raceway surface, ribs, and rolling elements are obviously jammed.
4. The cage is severely worn or the rivets are loose.
5. The raceway surface and rolling elements are rusty and scratched.
6. There are obvious indentations and scratches on the rolling surfaces and rolling elements.
7. There is creep on the inner diameter surface of the inner ring or the outer diameter of the outer ring.
8. Overheating can cause severe discoloration.
9. The sealing ring and dust cover of the grease-sealed bearing are seriously damaged.

1. Definition of crossed roller bearings

Crossed roller bearing is a special high-performance rolling bearing. Its characteristic is that the two rows of rollers inside the bearing are arranged at a 90-degree cross, which makes the bearing have higher rigidity and stability when bearing radial load and axial load. This kind of bearing has high dynamic load bearing capacity, low friction coefficient, and excellent rotation accuracy. It is widely used in various high-precision, high-load, and high-speed mechanical systems.

2. Application scenarios of crossed roller bearings

(1) CNC machine tools: CNC machine tools have extremely high requirements for rotation accuracy and dynamic performance. Crossed roller bearings can provide stable and precise support for the machine tool spindle, improving the machine tool’s processing accuracy and production efficiency.
(2) Industrial robots: Industrial robots require high-precision and high-rigidity rotating joints. Crossed roller bearings can provide excellent rotation performance and load capacity and are important components of robot joints.

(3)Aerospace: In the aerospace field, crossed roller bearings are widely used in key parts such as main shafts and servos of various aircraft due to their high precision, high speed and high load capacity.
(4)Precision instruments: Precision instruments have extremely high requirements for rotation accuracy and dynamic performance. Crossed roller bearings can provide stable and accurate support for the instrument and improve the measurement accuracy and stability of the instrument.

3. Working principle of crossed roller bearings

The working principle of crossed roller bearings is different from ordinary rolling bearings. In ordinary rolling bearings, the rollers move linearly along the inner ring of the bearing, while in crossed roller bearings, due to the cross arrangement of the rollers, the rollers can produce bidirectional displacements in the axial and radial directions when bearing loads. Has better rigidity and stability. In addition, the rotation accuracy of crossed roller bearings has also been significantly improved, because the cross arrangement of the rollers causes the friction between the inner and outer rings to cancel each other out, reducing the friction loss and heating of the bearing.

4. Installation method of crossed roller bearings

(1) Preparation work

Before starting to install crossed roller bearings, the following preparations need to be made:

1.Prepare the required tools and materials: crossed roller bearings, nuts, flat washers, lock washers, lubricants, cleaning agents, plastic or rubber hammers, measuring tools, etc.
2.Check the crossed roller bearings: Confirm that the bearings are not damaged, rusted, worn, etc., and check whether the mating surface is smooth.
3.Clean the case: Use cleaning fluid to clean the inside of the case to remove impurities and residues.
4.Prepare the installation surface: Apply lubricant inside the casing to reduce friction and improve installation efficiency.

2) Installation steps

1.Clean crossed roller bearings carefully
Due to the special structure of crossed roller bearings, their inner and outer surfaces need to be carefully cleaned before installation. Wipe the bearings with detergent and a clean cloth to ensure the surface is free of residue and dust. Pay special attention to keeping the mating surface clean to prevent impurities from affecting the installation effect.

2.Assemble the bearing so that the rings and rolling elements rotate
Assemble the rings and rolling elements of the crossed roller bearing to ensure free rotation. Pay attention to keeping the gap between the inner and outer rings of the bearing and the rolling elements even to avoid sticking. During assembly, no tools or knocks should be used to avoid damaging the bearings.

3.Apply a certain amount of pressure so that the bearing can be firmly installed on the casing
Install the crossed roller bearing on the casing through nuts and flat washers. Start by placing the flat pad inside the case, then gently place the bearing on the flat pad. Next, tighten the nut and apply some pressure so that the bearing can be firmly installed on the casing. When tightening the nut, the force should be kept moderate to avoid damaging the bearing and mating surface.

4.Carry out post-installation inspection and debugging to ensure the bearings work smoothly
After completing the installation, the following inspections and debugging are required:

(1) Check the rotation flexibility of the bearing: Rotate the outer ring and inner ring of the bearing to ensure that they rotate freely without sticking.
(2) Check the mating surface: Check whether the mating surface between the bearing and the casing is tightly fitted to ensure there is no gap.
(3) Check the preload force: Adjust the preload force as needed to ensure that the bearing has appropriate preload force during operation.
(4) Debugging the lubrication system: Check whether the lubrication system is operating normally and ensure that the bearings are fully lubricated during operation.
(5) Trial operation: Carry out a trial operation test to observe whether the operating status of the bearing is normal. If there is abnormal sound or vibration, stop the machine immediately to check and troubleshoot.

Inspection and installation methods of motor bearings：

1.Before inspecting the bearing, first remove the old lubricating oil from the inner and outer small covers of the bearing, and then clean the inner and outer small covers of the bearing with a brush and gasoline. After cleaning, clean the bristles or cotton filaments and do not leave them in the bearing.

2.Carefully inspect the cleaned bearings. The bearings should be clean and intact, without overheating, cracks, peeling, grooves, impurities, etc. The inner and outer raceways are smooth, and the clearances everywhere are qualified. If the support frame is loose and causes friction between the support frame and the bearing sleeve, Bearings should be replaced with new ones.

3.After maintenance, the bearing should rotate flexibly without jamming.

4.Check that there is no wear on the inner and outer small covers of the bearing. If there is wear, the cause should be found out and dealt with.

5.The fit between the inner sleeve of the bearing and the shaft should be tight, otherwise it should be dealt with.

6.When assembling a new bearing, use oil heating or eddy current heating to heat the bearing. The heating temperature is preferably 90 to 100°C. Set the bearing on the motor shaft at high temperature and ensure that the bearing is assembled in place. It is strictly forbidden to heat the bearing in a cold state. Go up to avoid damaging the bearings.

Motor bearings should generally be cleaned and refueled after 2,000 hours of use. There are two methods for cleaning motor bearings:

1.Hot oil cleaning method

Mainly use soft dry oil or anti-rust paste to harden motor bearings. They should be immersed in hot engine oil at 100-200°C. Clamp the motor bearings with pliers and use a brush to clean the oil stains on the motor bearings. Soft dry oil or anti-rust paste melts when heated to 100-200°C, and is easily washed out from the gaps in the motor bearings. Sometimes as long as the motor bearing is shaken in the oil many times, the oil dirt will flow away from the gaps.

When cleaning the centripetal spherical motor bearings of the motor, the balls, bead frames, and inner rings should be turned laterally out of the outer ring and then immersed in hot oil. When cleaning the short cylindrical roller motor bearings, the rollers, beads should also be removed. The frame, inner ring and outer ring are detached.

During hot oil cleaning, the bearing temperature of the oil should not exceed 200°C. If an open flame is used for direct heating, care should be taken to prevent the oil from burning. The motor bearings should be suspended in the oil pan. If they sink to the bottom, they will cause overheating and reduce the hardness.

2 General cleaning method

Soak the motor bearings in kerosene for 5-10 minutes. Hold the inner ring with one hand and rotate the outer ring with the other hand. The dry oil or anti-rust paste on the motor bearings will fall off. Then put the motor bearings into cleaner kerosene, scrub with a soft brush to clean the oil in the balls and gaps, then put them in gasoline to clean them once, take them out and put them on clean paper.

When cleaning radial ball motor bearings and short cylindrical roller motor bearings, the balls, ball frames, inner rings and outer rings should be separated and cleaned. The motor bearings mounted on the shaft are mainly cleaned by spraying oil or spraying with an oil gun. Oil stains that are easy to be cleaned are first treated with kerosene and then gasoline; oil stains that are difficult to be cleaned are first sprayed with hot engine oil at 100-200°C. Wash or spray with oil gun, then clean with gasoline. Be careful not to use sharp tools to scrape hardened grease or rust on the motor bearings to avoid damaging the motor.
Check the smoothness of the rolling elements and groove rings of the motor bearings. Clean the motor bearings and wipe them dry with a clean cloth.

Ball bearings are very important components in the mechanical field and are widely used in various rotating shafts and linear guide mechanisms. In order to ensure the good operation of ball bearings in the mechanism, they must be reasonably classified.

Ball bearings are mainly classified according to their structural characteristics and friction properties. According to structural characteristics, ball bearings can be divided into two categories: single row and double row ball bearings. Single row ball bearings have only one raceway, while double row ball bearings have two raceways. In addition, according to different friction properties, ball bearings can be divided into two categories: sliding bearings and rolling bearings.

Sliding bearings have the characteristics of strong load-bearing capacity, smooth operation, and long life. However, the friction resistance is large and requires regular maintenance and upkeep. Rolling bearings have the advantages of small friction resistance, high operating accuracy, and simple maintenance. However, the carrying capacity is relatively low and the price is high.

Sliding bearings can be divided into two types: full oil film and mixed film according to different load-bearing characteristics. Full oil film bearings have small friction resistance and are suitable for light load applications with high speed rotation. Hybrid film bearings have strong load-bearing capacity and are suitable for low-speed and heavy-load applications.

Rolling bearings can be divided into deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings and other types according to their shape and size. Deep groove ball bearings have high precision and low friction resistance and are widely used in various mechanical transmission devices. Angular contact ball bearings can withstand radial and axial loads and are suitable for high-speed and high-precision applications. Cylindrical roller bearings have strong load-bearing capacity and high operating accuracy, and are suitable for low-speed and heavy-load mechanical transmission.

Ball bearings are widely used in various fields, such as aerospace, automobiles, machinery, etc. In the aerospace field, due to the extremely high accuracy and stability requirements for rotating mechanisms, high-precision deep groove ball bearings and angular contact ball bearings are required. In the automotive field, rolling bearings are widely used in engines, chassis and suspension systems to improve the vehicle’s handling and stability. In the field of machinery, ball bearings are widely used in various rotating shafts and linear guide mechanisms to achieve precise transmission and positioning of mechanical parts.

Bearings are an integral part of mechanical equipment and they play a key role in various movements and rotations. However,the life of bearings is often affected by various factors,including use environment, maintenance frequency and method,etc. Here are some tips on how to maintain bearings.

1.Keep it clean.

1.Keep the bearings away from impurities such as dust, debris and metal particles. These impurities can cause bearing wear and damage.
2.Clean the area around the bearings regularly to make sure there is no residue or debris.
3.Use appropriate seals and guards to reduce the ingress of dust and other particulate matter.

2.Lubrication and maintenance.

1.Choose the appropriate lubricant based on the bearing type and working environment. For example, grease lubrication is suitable for low-speed heavy loads, while oil lubrication is suitable for high-speed light loads.
2.Change the lubricant regularly, usually based on usage time and mileage.
3.Avoid using too much or too little lubricant to avoid overheating or insufficient lubrication of the bearing.
4.For high-precision, high-speed bearings, it is recommended to use special grease or add lubricating oil.

3.temperature control

1.Bearing overheating can be caused by insufficient lubrication, excessive loading, or improper installation.
2.Check bearing temperatures regularly to make sure they are within normal limits.
3.For high-temperature environments or heavy-duty applications, consider using special materials and mounting methods to reduce temperatures.

4. Regular inspection and maintenance

1.Regularly inspect the bearings, including appearance, lubrication and fixation.
2.For bearing types that are prone to failure, preventive maintenance should be performed in advance.
3.Bearing components that are prone to wear, such as balls or cages, should be replaced regularly.
4.During repairs, follow proper installation methods and use the correct tools to avoid further damage to the bearings.

5.Correct installation method

1.Select the correct installation method and tools based on bearing type and equipment requirements.
2.Appropriate pressure and speed should be used during installation to avoid damage to the bearings.
3.During installation, ensure the correct alignment and fit of the inner and outer bearing rings to avoid friction and vibration.
4.After installation is complete, check that the bearings are well fixed and that the equipment is in the correct position and angle.

6.avoid overloading

1.Make sure the equipment operates within the rated load range to avoid overloading.
2.If equipment loads change, the bearings should be adjusted to accommodate these changes.
3.For heavy-duty applications, bearings of appropriate strength and thickness should be selected.

7.Avoid shock and vibration

Avoid exposing bearings to shock or vibration, which may cause bearing damage or loosening.
For applications that are susceptible to shock, consider using buffer bearings or other shock-resistant designs.
Regularly check the status of the equipment to ensure its stable operation and avoid accidental impact on the bearings.

In summary, caring for bearings requires careful attention and maintenance, including keeping them clean, properly lubricated, controlling temperature, regular inspection and maintenance, proper installation, avoiding overloading, and avoiding shock and vibration. By following these recommendations, you can extend bearing life and improve equipment equipment performance.