NSK bearing purchase matters:
1, the choice of NSK bearing model: NSK bearing model is generally selected by the user's technical personnel according to the use conditions and load bearing of supporting products.Business personnel mainly understand whether the actual load of the user is in line with the selected NSK bearing. If the NSK bearing cannot meet the use requirements, it should be recommended to change the model as soon as possible, but there will be no problem in the selection of the model unless the special product is selected.
2, NSK bearing clearance choice: when users buy NSK bearings, businesses generally just let us know in what type, grade, rarely for NSK bearing clearance request, business people must ask NSK bearing NSK bearing conditions of use, including speed, temperature, NSK bearing clearance fit tolerance are directly related to the choice.Generally, CM clearance is used for motors with speeds below 3500rpm, such as high temperature and high speed motors, which require relatively large clearance.
NSK bearing clearance will be reduced after assembly because of the increase of the inner hole and the reduction of the outer circle, the reduction of clearance = the amount of interference x60%(except for the NSK bearing chamber which is aluminum).For example, the clearance of NSK bearing before assembly is 0.01mm, and the interference amount during assembly is 0.01mm, then the clearance of NSK bearing after assembly is 0.004mm.In theory, the noise and life of NSK bearings reach the best state at zero clearance. However, considering the temperature rise and other problems in actual operation, it is better for NSK bearings to have clearance of 0.002mm-0.004mm after assembly.
3, the selection of grease: the selection of grease is generally based on the speed, temperature resistance, noise requirements and pneumatic torque of NSK bearings, which requires us to understand the oil and grease.
4, the choice of NSK bearing seal form: NSK bearing lubrication can be divided into oil lubrication and grease lubrication.Oil lubricated NSK bearings are generally in the form of NSK bearings, and grease lubricated NSK bearings are generally sealed with dust caps or rubber seals.Dust cover is suitable for high temperature or good use environment parts, seals are divided into contact seal and non-contact seal two kinds, contact seal dustproof performance is good but the pneumatic torque is large, non-contact seal pneumatic torque is small, but the sealing performance is not good as the contact type.
Matters needing attention when using NSK bearings:
1, shaft and NSK bearing room tolerance selection and control: NSK bearing pressed into NSK bearing should be flexible rotation without blocking sense.If there is obvious rotation is not flexible, it indicates that the size of the shaft is too large and the tolerance should be reduced.If the NSK bearing is pressed into the shaft and rotated by hand, it may be that the tolerance of the shaft is too large or the roundness of the shaft is not good.Therefore, roundness should also be controlled when controlling the tolerance of the shaft and NSK bearing chamber. At present, many domestic manufacturers only control the tolerance
There are controls on roundness.
2, NSK bearing assembly mode: because NSK bearing is a high-precision product, such as improper assembly is easy to cause damage to NSK bearing channel, resulting in damage to NSK bearing.NSK bearings should have special dies during assembly, which can not be knocked at will. When they are pressed into the shaft, they can only be stressed by small rings, and only by large rings when they are pressed into large rings.When assembling, it is required to use air pressure or hydraulic pressure. When pressing, the upper and lower dies should be outside the horizontal state. If there is an inclination, it will lead to damage of NSK bearing channel due to force, and make NSK bearing lead to sound.
3, the prevention of foreign body assembly: when NSK bearings are installed on the rotor for dynamic balancing, it is easy to enter the iron filings generated during dynamic balancing into the internal NSK bearings, so it is best to install NSK bearings before dynamic balancing.Some manufacturers in order to facilitate assembly, assembly in the NSK bearing room coated with some oil or grease lubrication effect, but often it is difficult for the operator to control the amount of good, if the oil or grease in the NSK bearing room deposit more, it is easy to enter the NSK bearing interior along the shaft when the NSK bearing rotated.It is best not to paint oil or grease in the NSK bearing room. If it is necessary to control it, there shall be no accumulation in the NSK bearing room.
4. Prevention of paint rust: the characteristic of paint rust is mostly in sealed motor. The sound of the motor is very good during assembly, but after some time in the warehouse, the abnormal sound of the motor becomes very big.In the past, many manufacturers will think that it is the problem of NSK bearings. After our continuous publicity, now the motor factory has realized that it is mainly the problem of insulating paint.The problem is mainly because the acid substances volatilizing from the insulating paint form corrosive substances at a certain temperature and humidity, which corrodes the NSK bearing channel and leads to the damage of the NSK bearing.At present, the only way to solve this problem is to choose good insulating paint and assemble it after a period of ventilation after drying.