Do you understand all the bearing knowledge?

Bearings are generally composed of an inner ring, an outer ring, a rolling element and a cage. For sealed bearings, add lubricant and a sealing ring (or dust cap). That's what bearings are all about.

According to the working condition of the bearing, different types of bearings can be selected to better play the function of the bearing and extend the service life of the bearing. We choose bearings to consider the following factors:

   1. Radial load

   2.  Axial load

   3.  Speed requirements 

   4.  Radial runout 

   5.  Axial runout 

   6.  Operating temperature 

   7.  Noise requirements 

   8.  Lubrication status

Bearing selection method

     The market requirements for the performance of various mechanical devices and instruments using rolling bearings are becoming increasingly stringent, and the conditions and performance required for bearings are becoming increasingly diversified.

     In order to select the most suitable bearing from a large number of structures and sizes, it is necessary to study from various angles. In the selection of bearings, the bearing structure is generally determined by considering the bearing arrangement, installation, and disassembly difficulty of the shafting, the space allowed by the bearing, the size and the marketability of the bearing.

     Secondly, while comparing the design life of various machines using bearings and the different endurance limits of bearings, the bearing size is determined. When choosing bearings, it is often inclined to only consider the fatigue life of bearings, and the grease life, wear, noise and so on caused by the aging of grease also need to be fully studied.

     Furthermore, according to different uses, it is necessary to choose bearings that are specially designed for accuracy, clearance, cage structure, grease, and so on. However, there is no certain order and rules for the selection of bearings, and the priority should be given to the conditions, performance and most relevant matters required for bearings, which are particularly practical.

Bearing use precautions

    Rolling bearings are precision components, and their use must be carefully carried out accordingly. No matter how high performance bearings are used, if they are used improperly, they will not get the expected high performance, and the use of bearings should be noted as follows.

  1. Keep bearings and their surroundings clean. Even small dust that can't be seen by the eyes will have a bad effect on the bearing. Therefore, it is necessary to keep the surrounding clean so that the dust does not invade the bearing.

  2. Use with care and caution. Strong impact on bearings in use will produce scars and indentations, which will become the cause of accidents. In serious cases, it will crack and break, so it must be paid attention to.

  3. Use the appropriate operating tools. Avoid replacing existing tools with the right ones.

  4. Pay attention to the corrosion of bearings. When operating the bearing, the sweat on the hands will become the cause of rust. Be careful to use clean hands, it is best to wear gloves.

Proper mounting of bearings

    Whether the bearing is installed correctly affects the accuracy, life and performance. Therefore, the design and assembly department should fully study the installation of bearings. It is expected to be installed according to operating standards. The items of operating standards are usually as follows:

  1. Clean the bearing and bearing related parts 

  2.  Check the size and finishing of the related parts 

  3. Installation 

  4. Inspection after the installation of the bearing 

  5. Supply lubricant

    Before installation, unpack. General grease lubrication, no cleaning, directly fill grease. Lubricating oil lubrication, ordinary do not need to be cleaned, however, instruments or high-speed bearings, etc., to clean with clean oil, remove the anti-rust agent coated on the bearing. The bearing with the rust inhibitor removed is easy to rust, so it can not be placed in disregard. In addition, bearings that have been sealed in grease can be used directly without cleaning.

   The installation method of the bearing varies according to the bearing structure, fit and condition. Generally, the inner ring needs interference fit because it is mostly rotating. Cylindrical bore bearings, multi-purpose press, or multi-purpose hot loading method. In the case of taper holes, install directly on the taper shaft, or install with a sleeve. When installed to the shell, the general clearance is more, the outer ring has interference, usually pressed into it by a press, or there is also a cold shrink fit method for installation after cooling. When dry ice is used as a coolant and cold shrinkage is combined with installation, the moisture in the air will condense on the surface of the bearing. Therefore, appropriate anti-rust measures are needed.

Bearing maintenance methods

    In order to maintain the original performance of the bearing in good condition for as long as possible, it is necessary to maintain and overhaul in order to prevent accidents, ensure the reliability of operation, and improve productivity and economy. Maintenance of the best operating standards corresponding to the operating conditions of the machine, carried out regularly. The contents include monitoring operation status, replenishment or replacement of lubricants, and periodic disassembly inspections. As maintenance matters in operation, there are bearing rotation sound, vibration, temperature, lubricant status and so on.

bearing lubrication

    The purpose of lubrication of rolling bearings is to reduce internal friction and friction loss of bearings, prevent burning and sticking, and its lubricating effect is as follows:

 1.  Reduce friction and wear loss. Prevent metal contact and reduce friction and wear in the mutual contact part of the bearing ring, rolling element and retainer.

 2.  Prolong fatigue life. The rolling fatigue life of the bearing is extended when the rolling contact surface is well lubricated during rotation. On the contrary, the oil viscosity is low, the lubricating oil film thickness is not good, it is shortened.

 3.  Discharge friction heat and cooling. The circulating oil feeding method can use oil to remove heat caused by friction, or heat from the outside, and cool. Prevent the bearing from overheating and prevent the lubricating oil itself from aging.

 4. Others also have the effect of preventing foreign bodies from intruding into the bearing, or preventing rust and corrosion.

    The lubrication method of bearing is divided into grease lubrication and oil lubrication. In order to make the bearing function well, first of all, it is necessary to choose the lubrication method suitable for the use conditions and the purpose of use. If only lubrication is considered, the lubricity of oil lubrication is dominant. However, grease lubrication has the advantage of simplifying the structure around the bearing, and the advantages and disadvantages of grease lubrication and oil lubrication are compared.

Bearing maintenance methods

    Bearing cleaning: When disassembling the bearing for maintenance, first record the appearance of the bearing, confirm the residual stock of lubricant, and wash the bearing after sampling the lubricant used for inspection. As a cleaning agent, cleaning agent and kerosene are commonly used. The removed bearings are cleaned, divided into rough cleaning and fine cleaning, respectively, placed in the container, and the metal mesh bottom is put first, so that the bearings do not directly contact the dirt of the container. During rough cleaning, if the bearing rotates with dirt, the rolling surface of the bearing will be damaged, and it should be paid attention to. In the crude cleaning oil, use a brush to remove grease and adhesion, roughly clean, transfer to fine washing. Fine washing is to rotate the bearing in the cleaning oil while carefully cleaning it. In addition, the cleaning oil should be kept clean frequently.

    Bearing maintenance and judgment: In order to determine whether the disassembled bearing can be used, it is necessary to check after the bearing is cleaned. Check the state of raceway surface, rolling surface, matching surface, cage wear, bearing clearance increase and damage and abnormality unrelated to dimensional accuracy reduction. For non-separated small ball bearings, use one hand to support the inner ring horizontally and rotate the outer ring to confirm whether it is smooth. Tapered roller bearings and other separated bearings can be checked separately on the raceway surface of the rolling body and the outer ring. Because large bearings can not be rotated by hand, pay attention to checking the appearance of rolling body, raceway surface, cage, guard surface, etc. The higher the importance of bearings, the more careful inspection is required.