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How To Select Bearings And Precautions In Use

With the progress and development of society, mechanization has been widely used in production and life. As an indispensable part of machinery, bearing will be used more and more widely, because it will be used wherever there is rotation.

Bearing mainly plays the role of supporting and reducing friction in machinery, so the accuracy and noise of bearing are directly related to the service life of machinery.

However, business personnel often encounter some customers, that is, the efficiency of good bearings or imported bearings is not high, which is related to the use and selection of bearings. Some people may say that “the use and selection of bearings are the business of users. I only care what users want and what I sell”. However, as a qualified salesperson, in addition to being proficient in their own product knowledge, they should also be proficient in the use of products, that is, doctor sales, and select good supporting bearings according to the performance and service conditions of users’ supporting products. This is the specialized manufacturing and sales popular among major companies in the world. This method has also achieved good results since its implementation in renben group.

Because there are many types and a wide range of bearings, the following will mainly analyze the use and selection of deep groove ball bearings with a wide range of applications. It is hoped that people who know less about bearings can deepen their understanding of bearings.

How To Select Bearings And Precautions In Use
Bearing selection
1. Selection of bearing model:

the bearing model is generally selected by the user’s technicians according to the service conditions and load of supporting products. Business personnel mainly know whether the user’s actual load is consistent with the selected bearing. If the bearing fails to meet the use requirements, they should advise the customer to change the model as soon as possible, but there will be no problem in selecting the model unless special products.

2. Selection of bearing clearance:

when purchasing bearings, users generally only tell what model and grade they are in, and rarely put forward requirements for bearing clearance. Business personnel must ask about the service conditions of bearings, including bearing speed, temperature and fit tolerance, which are directly related to the selection of bearing clearance. Generally, CM clearance is mostly used for motors with speed below 3500 rpm. For example, relatively large clearance is required for high-temperature and high-speed motors. After assembly, the bearing clearance will be reduced due to the increase of inner hole and the reduction of outer circle. The reduction of clearance = interference × 60% (unless the bearing housing is aluminum). For example, if the clearance before bearing assembly is 0.01mm and the interference during assembly is 0.01mm, the clearance after bearing assembly is 0.004mm. Theoretically, the noise and service life of the bearing reach a good state when there is zero clearance, but considering the problems such as temperature rise in actual operation, the clearance of the bearing after assembly is 0.002mm-0.004mm.

3. Selection of grease:

generally, the selection of grease is based on fag bearing according to the bearing speed, temperature resistance, noise requirements and starting torque. The business personnel are required to understand the performance of various grease.

4. Selection of bearing sealing type:

bearing lubrication can be divided into oil lubrication and grease lubrication. Oil lubricated bearings are generally formal bearings, and grease lubricated bearings are generally sealed with dust covers or rubber seals. The dust cover is suitable for parts with high temperature or good service environment. The seals are divided into contact seal and non-contact seal. The contact seal has good dust-proof performance but large starting torque, and the non-contact seal has small starting torque, but the sealing performance is not as good as the contact seal.

Precautions for bearing use
1. Selection and control of shaft and bearing housing tolerance:

the bearing shall rotate flexibly without blocking feeling after being pressed into the bearing. If there is obvious inflexible rotation, it indicates that the size of the shaft is too large and the tolerance should be reduced. If there is an obvious “rusty” feeling when the bearing is rotated by hand after being put into the bearing, it may be that the tolerance of the bearing is too large or the roundness of the bearing is not good. Therefore, when controlling the tolerance of shaft and bearing chamber, INA Bearing should also control the roundness. At present, many domestic manufacturers only control the tolerance and do not control the roundness.

2. Assembly method of bearing:

because the bearing is a high-precision product, improper assembly is easy to damage the bearing channel, resulting in bearing damage. The bearing shall be equipped with a special mold during assembly, and can not be knocked at will. When pressing the shaft, only the small ring can be stressed, and when pressing the large ring, only the large ring can be stressed. Air pressure or hydraulic pressure is required during assembly. During press assembly, the upper and lower molds shall be outside the horizontal state. If there is inclination, the bearing channel will be damaged due to stress and the bearing will produce conduction sound.

3. Prevention of assembly foreign matters:

when the bearing is installed on the rotor for dynamic balance, it is easy to enter the iron filings generated during dynamic balance NSK bearing into the bearing, so it is better to perform dynamic balance before installing the bearing. In order to facilitate assembly, some manufacturers apply some oil or grease in the bearing chamber for lubrication effect during assembly, but it is often difficult for operators to control the amount. If more oil or grease is accumulated in the bearing chamber, it is easy to enter the bearing along the shaft during bearing rotation. The bearing chamber shall not be coated with oil or grease. If it must be coated, it shall be controlled and there shall be no accumulation in the bearing chamber.

4. Prevention of paint rust:

paint rust is often found in sealed motors. The sound of the motor is very good during assembly, but after being placed in the warehouse for some time, the abnormal noise of the motor becomes very large, and there is serious rust when removing the bearing. In the past, many manufacturers thought it was the bearing problem. After our continuous publicity, the motor factory has realized that the main problem is the NTN bearing insulating paint. This problem is mainly because the acidic substances volatilized from the insulating paint form corrosive substances at a certain temperature and humidity, which corrodes the bearing channel and leads to bearing damage. At present, only good insulating paint can be selected and assembled after drying and ventilation for a period of time.

The service life of the bearing is closely related to manufacturing, assembly and use. It must be done well in each link in order to make the bearing in a good running state and prolong the service life of the bearing.