2022 September the Fifth Week GQZ Technical Knowledge: Installation and Adjustment of Rolling Bearing for High Speed Motor
Hot tags: cylindrical roller bearing(8)
A set of process methods are summarized for rolling bearing installation and commissioning
Abstract: With the continuous improvement of science and technology, high-speed motors are used more and more widely, which is accompanied by high noise, high temperature and short life. In view of this kind of problem, combined with many years of experience, a set of technological methods for rolling bearing installation and commissioning are summarized for readers' reference.
Keywords: high-speed motor; Bearing; Installation; debugging
1 Bearing storage method
(1) Although the bearing surface is coated with antirust oil before packaging and baling, the contact with the external air flow cannot be completely eliminated, so it should be avoided to store it in a damp environment as far as possible.
(2) Clean, dry, well ventilated and cool places shall be selected as far as possible. The place with a height of more than 30 cm shall be kept with cabinets or shelves.
(3) If the packed bearing has been disassembled due to incoming inspection and other reasons, pay great attention to the anti rust measures of the bearing.
2 Bearing cleaning
In order to prevent dust and rust during transportation and storage, the bearing surface is usually coated with anti rust oil. After opening the package, it is necessary to clean the antirust oil, which can be cleaned with high-purity gasoline or aviation kerosene (in a dust-free environment).
3 Check relevant parts
(1) The shaft and bearing chamber shall be cleaned without scars, burrs, burrs, etc.
(2) Check whether the dimensions of the shaft and bearing housing meet the tolerance fit with the internal and external diameters of the bearing.
(3) The measurement shall be carried out in the temperature control room. When the temperature of the measured parts and measuring tools is stable, use a micrometer or cylindrical gauge for measurement (multiple points measurement is required to check whether there is an obvious dimension difference).
4 Bearing installation
(1) The bearing is installed on the shaft by hot installation. Bearing heating temperature: room temperature+50 ℃~+60 ℃, and the maximum bearing heating temperature cannot exceed 120 ℃. Install lock nuts after two rows of bearings are sleeved on the shaft.
(2) When installing the angular contact ball bearing back to back, first cover the bearing on the shaft, then tighten the lock nut, and then apply the load. Then install the shaft and bearing into the end cover bearing chamber, and fix it with the front cover.
(3) Fastening of bearing. In order to fasten the inner ring of the bearing on the shaft, the thread is generally machined on the shaft and the lock nut is used for fastening. The perpendicularity between the threaded part of the nut and the end face is very important, because even if the accuracy of a single nut or thread on the shaft is very high, there will be deviation or inclination due to the gap between the shaft and the nut when tightening, so it is necessary to adjust to ensure the rotation accuracy of the shaft; At the same time, pay attention to take anti loose measures for the lock nut. Pay attention to applying proper torque on the tightening force of the nut. When placing a wide spacer between combined angular contact ball bearings, if the tightening force of the nut is too large, the inner spacer will be deformed. Therefore, the preload during installation is slightly greater than the set value. For 7010CDB/P4 bearing, the pre tightening force of locknut is 390 N. In order to fasten the bearing cup in the direction of the shaft, the bearing cover is usually fastened with bolts. If the tightening amount is too large or uneven, the outer ring raceway is easy to deform. In order to tighten the outer ring, it is recommended to tighten the bolts so that the clearance between the bearing cover and the end face of the bearing chamber is between 0101 mm and 0103 mm. For 7010CDB/P4 bearing, the bolt tightening force is 2500 N, the bolt tightening torque is 17 N · m, and the tightening amount of bearing cover is 0101 mm ～ 0103 mm.
(4) Precautions for installation. 1) The installation shall be carried out carefully, and the strong impact on the bearing is strictly prohibited. That will cause scratches and indentations, which will damage the bearing in serious cases, making the bearing unusable and scrapped. 2) Select the appropriate operation tool. 3) Pay attention to corrosion of bearing. When operating the bearing, the sweat on the hands will become the cause of rust, so you must wear gloves for operation. It is better to use fine cloth gloves or rubber gloves.
5 Grease injection method
Different methods of grease injection may lead to unstable temperature rise during initial running in operation, abnormal temperature rise, long initial running in time, and even sintering. Therefore, it is necessary to adopt appropriate grease amount and correct injection method according to service conditions. (1) Confirmation items before injection confirm that there is no residue inside the bearing. It is recommended that bearings for high-speed spindles be cleaned first, degreased, and then filled with grease. In other service conditions, it is also recommended to remove the rust preventative oil attached to the bearing interior.
(2) Injecting grease In order to inject proper amount of grease, it is recommended to use an injector, preferably one with injection reading.
(3) Grease injection volume The recommended injection volume of precision bearings is 10%~15% of the space volume of angular contact ball bearings for high-speed spindles and 20%~30% of the space volume of ball bearings for ordinary motors.
(4) The injection method is to evenly inject between steel balls. If the guide of the cage is phenol resin cage guided by the outer ring, it is recommended to lightly grease the guide surface of the cage. Rotate the outer ring of the bearing by hand, so that the grease is evenly carried to the raceway surface, the inner diameter of the cage, and the steel ball, so that the grease forms an oil film on the surface of the steel ball and the raceway.
6 Inspection after bearing installation
After the bearing is installed, the bearing circle runout is generally detected to determine whether it is qualified or in place. The axial runout of the outer ring end face of the angular contact bearing is generally controlled below 01002 mm; The inclination of angular contact bearing shall be controlled below 01005 mm; The concentricity of front and rear bearings shall be controlled below 01010 mm.
7 Operation preparation
The initial running in operation of the bearing after installation requires the following adjustments:
(1) Balance correction. The unbalance of the rotating body is due to the reciprocating stress and vibration generated under the action of centrifugal force, especially for the main shaft whose dm n value exceeds 1, 000, 000, it is necessary to carry out the balance correction of the shaft itself and the balance correction after assembly.
(2) Spindle installation. When the V-belt is driven, the coaxiality error between the main shaft pulley and the motor pulley is controlled below 0101 mm.
8 Initial running in operation method
When the motor is powered on for initial operation, if the speed is increased rapidly, the temperature will rise rapidly and the bearing will be damaged. It is indispensable to gradually increase the primary running in speed. Running in operation is carried out at normal temperature (15-25 ℃). It is recommended to test the bearing temperature while running. The maximum bearing temperature (bearing chamber temperature) during running in operation shall not exceed 55 ℃ (target 50 ℃). If this temperature is exceeded, stop running or decelerate to reduce the temperature. As shown in Figure 1, the change trend of temperature with time during running in at a certain speed.
[Continuous running in] Features: gradually increase the speed from low speed, but the running in time is long.
[Operation method] Gradually increase the speed from low speed, and in several stages, repeatedly operate [operation at a certain speed → temperature rise → temperature stability → increase the speed] to gradually reach the maximum speed. Generally, the maximum speed is divided into 10 stages, and the speed is increased after operating for 1-2 hours in each stage. When the temperature rise characteristic is OK as shown in Figure 2, the speed can be increased.
[Intermittent running in] Segment the highest speed (about 8~10 stages), and conduct rapid acceleration and deceleration operation from 0 to each stage speed. It is recommended to accelerate and decelerate the machine for about 1 minute as a cycle, and set it to run for about 10 cycles at each speed. Figure 3 shows the change trend of temperature with time during intermittent running in. Figure 4 shows the case of one week of intermittent running in.
Practice has proved that the noise and temperature rise of the motor will be significantly reduced and the service life of the motor will be greatly improved after the bearing is installed and run in strictly according to the above process requirements.
More about GQZ Cylindrical Roller Bearing：
GQZ precious-quality cylindrical roller bearing with reasonable price for customers all over the world and first-class service and unrivaled products.
GQZ Cylindrical roller bearings are available in a wide range of designs, series, variants and sizes. The main design differences are the number of roller rows and the inner/outer ring flanges as well as cage designs and materials.
The bearings can meet the challenges of applications faced with heavy radial loads and high speeds. Accommodating axial displacement (except for bearings with flanges on both the inner and outer rings), they offer high stiffness, low friction and long service life.
Cylindrical roller bearings are also available in sealed or split designs. In sealed bearings, the rollers are protected from contaminants, water and dust, while providing lubricant retention and contaminant exclusion. This provides lower friction and longer service life. Split bearings are intended primarily for bearing arrangements which are difficult to access, such as crank shafts, where they simplify maintenance and replacements.