1、 Selection aspect

Problem 1: Inaccurate load analysis leads to unreasonable selection

-Performance: In practical applications, if the size and direction of the radial and axial loads borne by the equipment are not accurately evaluated, bearing models with mismatched bearing capacity may be selected. For example, on a machine tool spindle with both large radial loads and significant axial loads, if the 7000/7200/7300 series bearings with too small contact angles are selected, there will be insufficient axial bearing capacity, resulting in significant axial displacement of the spindle during operation and affecting machining accuracy.

-Solution: Before selecting, it is necessary to conduct a detailed mechanical analysis of the equipment. Professional mechanical design software or consulting a professional mechanical engineer can be used to accurately calculate the specific values and directions of radial and axial loads. Then, based on the characteristics of bearings with different contact angles in terms of radial and axial load-bearing capacity, select the appropriate contact angle (such as choosing a model with a contact angle of 30 ° -40 ° when the axial load is large) and appropriate size specifications of bearings to ensure that they can effectively cope with the actual load conditions of the equipment.

Problem 2: Neglecting speed requirements and selecting models that are not suitable for high-speed working conditions

-Performance: When the equipment is in high-speed operation, such as high-speed grinding machine spindle, aviation engine accessory transmission system, etc., if a bearing model with a lower limit speed is selected, problems such as heating, increased vibration, and increased noise are likely to occur during operation. In severe cases, the bearing life may even be shortened, affecting the normal operation of the equipment.

-Solution: Fully understand the speed requirements of the equipment. For high-speed application scenarios, priority should be given to selecting bearing models with higher limit speeds. At the same time, the internal structure of the bearing should be comprehensively considered, such as the size and quantity of rolling elements, as well as the design of the retaining frame (generally, rolling elements are relatively small and retaining frames are more suitable for reducing centrifugal force at high speeds). In addition, appropriate lubrication methods and lubricants should be used (lubricating oil should be selected for high-speed operation, and attention should be paid to its heat dissipation and wear resistance) to ensure that the bearings can work stably at high speeds.

Problem 3: Incorrect consideration of accuracy level and pairing method selection

-Performance: In some situations where high precision is required, such as ultra precision machining machines, optical instruments, etc., if the selected bearing accuracy level is not high enough (such as choosing P2 or P4 level but choosing P5 or P6 level), it will result in the equipment's machining accuracy or measurement accuracy not meeting the expected requirements. In addition, if the pairing method (back-to-back, face-to-face, or series) is not reasonably selected based on the actual load distribution, installation space, and other working conditions, it will also affect the stability and rotation accuracy of the equipment. For example, on the spindle of a horizontal machining center that needs to bear bidirectional axial loads, the wrong selection of series paired bearings will result in insufficient ability of the spindle to resist axial forces during cutting, leading to vibration and decreased accuracy.

-Solution: Based on the specific precision standards of the equipment, select bearings with corresponding precision levels accurately. Thoroughly analyze the specific operating conditions of the equipment, including load direction, size, and installation space limitations, and determine the appropriate pairing form based on the characteristics of different pairing methods. For example, in the case of bidirectional axial loads and the need to improve system rigidity, back-to-back pairing is preferred; For those with large axial loads and compact installation space, face-to-face pairing can be considered; For those that bear large axial loads in a single direction, a series pairing method is used.

2、 Installation aspect

Problem 1: Bearing damage during installation

-Performance: Due to the high precision and relatively fine structure of the 7000/7200/7300 series bearings, improper installation can easily cause damage. For example, using inappropriate tools to directly strike the bearing may cause scratches and bumps on the surface of the bearing; When using the hot installation method, if the heating temperature is too high, the heating is uneven, or the heating time is too long, it will affect the material properties and dimensional accuracy of the bearing, damage its internal structure, and cause early failure of the bearing in subsequent use.

-Solution: Strictly follow the correct installation process and specifications, prepare suitable specialized installation tools before installation, such as high-precision bearing installation sleeves, presses, etc., and avoid directly tapping the bearings. For the hot installation method, the heating temperature (usually around 80-120 ° C, adjusted according to the actual situation) and heating time should be strictly controlled according to the specifications and materials of the bearings, and the heating should be uniform. Professional bearing heating equipment can be used for operation. At the same time, the installation environment should be kept clean and dry to prevent impurities from entering the bearing installation site.

Problem 2: Improper adjustment of axial clearance or preload during the installation of paired bearings

-Performance: When installing paired bearings, it is necessary to accurately adjust the axial clearance or apply preload force. If the adjustment is not accurate and the clearance is too large, it will cause the bearings to vibrate and move more during operation, affecting the rotational accuracy of the equipment; Insufficient clearance or excessive preload force can increase the internal friction of the bearing, causing overheating, accelerating bearing wear, and shortening its service life.

-Solution: Use professional measuring tools such as feeler gauges, specialized clearance gauges, etc. According to the equipment requirements and bearing matching method, adjust the axial clearance or apply pre tension force accurately by reasonably adding or removing gaskets, adjusting nuts, and other methods. During the adjustment process, multiple measurements should be taken to verify that it is within the specified reasonable range. For example, for paired angular contact ball bearings on machine tool spindles, it is usually necessary to consider the spindle's specifications? Under working conditions such as speed and load, the preload force is accurately set to ensure that the spindle can achieve high rotational accuracy while avoiding problems such as overheating caused by excessive preload.

Problem 3: Poor coaxiality after installation

-Performance: If there is a deviation in the coaxiality between the bearing and related components after installation, it will cause uneven bearing force on the shaft, resulting in unilateral wear during operation, which can lead to vibration, increased noise, and decreased rotational accuracy, seriously affecting the normal operation and service life of the equipment.

-Solution: Adopt appropriate installation assistance methods to ensure coaxiality, such as using positioning pins, specialized fixtures, etc., to ensure that the axis of the bearing coincides with the axis of other related rotating components of the equipment as much as possible during the installation process. After installation, coaxiality can be checked using measuring tools such as a dial gauge. If coaxiality does not meet the requirements, the installation position of the bearing needs to be readjusted, and factors that may cause coaxiality deviation such as uneven installation surfaces and insufficient machining accuracy of the shaft need to be investigated and corrected.

3、 Maintenance aspect

Problem 1: Poor lubrication management

-Performance:

-Improper selection of lubricants: If the viscosity of the selected lubricant does not meet the requirements of the equipment operating conditions, such as using lubricating oil with high viscosity on high-speed equipment, it will result in poor fluidity, delayed heat dissipation, and increased bearing temperature; However, using lubricants with low viscosity on heavy-duty equipment cannot form an effective oil film, resulting in increased wear.

-Unreasonable lubrication cycle: Failure to scientifically set the lubrication cycle based on factors such as bearing speed, load, and operating temperature, resulting in insufficient or excessive lubrication. When lubrication is insufficient, friction between bearing components increases, which can easily lead to problems such as wear and overheating; Excessive lubrication may cause excessive accumulation of grease inside the bearing, increase operating resistance, and also cause heating. It may also lead to grease leakage and equipment contamination.

-Solution:

-Correct selection of lubricant: Taking into account the working conditions of the bearing, such as selecting lubricating oil with low viscosity, good heat dissipation, and wear resistance for high rotational speed; Choose lubricants with high viscosity and strong load-bearing capacity for the load; Simultaneously pay attention to other performance indicators such as antioxidant and corrosion resistance of lubricants. You can refer to the recommendations of bearing manufacturers and industry experience to determine the appropriate type of lubricant.

-Reasonably determine the lubrication cycle: Develop a lubrication plan based on the specific operating conditions of the bearing. Generally, it can be determined whether lubrication operation needs to be advanced or delayed by regularly checking the status of the lubricant (such as color, viscosity changes, etc.), monitoring the temperature and operating sound of the bearing, etc. For high-precision bearings on critical equipment, an automated lubrication monitoring and control system can even be established to ensure optimal lubrication at all times.

Problem 2: Failure to promptly identify and address potential fault hazards

-Performance: Lack of effective monitoring methods and regular inspection system makes it difficult to detect early signs of bearing failure, such as slight wear, slight temperature rise, etc., in a timely manner. By the time the malfunction becomes apparent, such as abnormal increase in vibration, high temperature, and harsh noise, the bearings often have suffered severe damage and may need to be replaced in advance. This may even affect the normal operation of other components of the equipment, leading to prolonged downtime and increased maintenance costs.

-Solution: Establish a comprehensive regular inspection mechanism, specify the inspection items (including appearance wear, clearance changes, temperature, vibration, etc.) and corresponding inspection cycles, use professional detection equipment (such as infrared thermometers, vibration sensors, etc.) to monitor the operating parameters of bearings in real time or regularly, and set reasonable warning thresholds. Once a parameter is found to be close to or exceed the threshold, stop the machine in a timely manner for detailed inspection, analyze the cause of the fault, and take corresponding maintenance measures, such as supplementing or replacing lubricants, readjusting installation, replacing bearings, etc., to eliminate potential faults in their early stages.

By accurately identifying common technical issues with high-precision and paired angular contact ball bearings 7000/7200/7300 series and adopting effective solutions, the performance advantages of these bearings can be better utilized, their service life can be extended, and the stable and efficient operation of the equipment can be guaranteed.