How To Improve The Installation Accuracy Of SKF Bearings?

(1) Measure the size of the shaft and the SKF bearing seat hole to determine the matching accuracy of the SKF bearing. The matching requirements are as follows: the inner ring and the shaft adopt an interference fit, and the interference is 0 ~ +4 μm (at light load and high precision, it is 0); the outer ring and the SKF bearing seat hole adopt clearance fit, the clearance amount is 0～+6μm (but when the bearing at the free end uses angular contact ball bearing, the clearance can also be increased); the roundness error of the shaft and the seat hole surface is 2μm Below, the end face parallelism of spacers used in SKF bearings is less than 2 μm, the runout of the inner end of the shaft shoulder to the outer end face is less than 2 μm; the runout of the shoulder of the SKF bearing housing hole to the axis is less than 4 μm; Beat below 4μm.
(2) Installation of SKF bearings on the shaft before the fixed end: Clean the bearings thoroughly with clean kerosene. For grease lubrication, first inject an organic solvent containing 3% to 5% grease into the bearings for degreasing and cleaning, then Use an oil gun to fill a certain amount of grease into the SKF bearing (accounting for 10% to 15% of the space volume of the SKF bearing); heat the SKF bearing to raise the temperature by 20 to 30°C, and install the bearing into the shaft end with a hydraulic press; put the adapter sleeve Press on the shaft and press against the end face of the SKF bearing with a suitable pressure to make it axially positioned; wind the belt of the spring balance on the outer ring of the bearing, and check whether the specified preload has a large change by measuring the starting torque (Even if the SKF bearing is correct, the preload may vary due to fit or cage deformation).
(3) Put the imported SKF bearing-shaft assembly into the seat hole: heat the seat hole to raise the temperature by 20-30°C, and install the SKF bearing-shaft assembly into the seat hole with continuous and gentle pressure; adjust the front cover so that the front The fastening amount of the cover is 0.02～0.05μm. Based on the outer end surface of the SKF bearing seat, the head of the dial indicator is touched on the surface of the journal, and the shaft is rotated to measure its runout. The error is required to be below 10μm; The meter is positioned on the shaft, the head of the meter touches the inner surface of the rear seat hole, and the shaft is rotated to measure the coaxiality of the front and rear seat holes of the SKF bearing seat.
(4) Selectively place the SKF bearing at the free end at a position that may offset the deviation, install it at the rear support position of the bearing housing, and offset the mutual roundness deviation and coaxiality deviation as much as possible.
After the SKF bearing is installed in the main engine, if the radial runout of the SKF bearing main shaft is measured, it can be found that the measured value of each revolution has a certain change; when the measurement is carried out continuously, it can be found that after a certain number of revolutions, the change will Approximately repeated. The index to measure the degree of this change is the cyclic rotation accuracy. The number of revolutions required for the approximate repetition of the change represents the “quasi-period” of the cyclic rotation accuracy. The magnitude of the change in the quasi-period is large, that is, the cyclic rotation accuracy is poor. .
If proper preload is added to the SKF bearing spindle, the speed is gradually increased to close to the working speed to implement the “run-in” effect of the SKF bearing, which can improve the cyclic rotation accuracy of the spindle.
After the SKF bearing is installed, in order to check whether the installation is correct, a running inspection is required. Small machinery can be rotated by hand to confirm whether it rotates smoothly. The inspection items include poor operation caused by foreign objects, scars, and indentations, unstable torque caused by poor installation and poor processing of the mounting seat, excessive torque caused by too small clearance, installation errors, and seal friction, etc. wait. If there is no abnormality, the power operation can be started.
Large machines cannot be rotated by hand, so cut off the power immediately after starting without load, run the machine idling, check whether there is vibration, noise, contact with rotating parts, etc., and enter power operation after confirming that there is no abnormality.
Power operation starts from low speed with no load and gradually increases to the rated operation under the specified conditions. The items to be checked during the test run are whether there is abnormal sound, temperature change of SKF bearing, leakage or discoloration of lubricant, etc. If any abnormality is found, stop the operation immediately, check the machine, and remove the bearing for inspection if necessary.
The temperature of SKF bearings can generally be estimated based on the external temperature of the bearing seat. However, it is more accurate to directly measure the temperature of the outer ring of the bearing by using the oil hole. The bearing temperature gradually rises from the start of operation, and usually stabilizes after 1 to 2 hours. If the bearing is not installed properly, the temperature will rise sharply and abnormally high temperature will appear. The reasons are such as too much lubricant, too small bearing clearance, poor installation, excessive friction of the sealing device, etc. In the case of high-speed rotation, the wrong choice of SKF bearing structure and lubrication method is also the reason.
The rotating sound of SKF bearings is checked with a stethoscope, etc. Strong metal noise, abnormal sound, irregular sound, etc. indicate abnormalities. The reasons include poor lubrication, poor precision of the shaft or housing, bearing damage, foreign matter intrusion, etc.