High precision bearing after installation accuracy

After the bearing is installed in the main engine, if the radial runout of the spindle is measured, it can be found that the measured value of each revolution has a certain change; When continuous measurements are made, it can be found that the change repeats approximately after a certain number of revolutions. The index to measure the degree of this change is the cyclic rotation accuracy. The revolution required for the approximate repetition of the change represents the "quasi period" of the cyclic rotation accuracy. In the quasi period, the magnitude change amplitude is large, which means the cyclic rotation accuracy is poor.

If appropriate preload is applied to the spindle, the speed will gradually increase to close to the working speed, in order to implement the "running-in" effect of the bearing, the rotation precision of the spindle cycle can be improved.

After the angular contact ball bearing is loaded into the spindle, the installation accuracy check sequence is as follows (take an ordinary lathe with a shaft diameter of 60-100mm as an example) :

(1) Measure the size of shaft and bearing seat hole to determine the fitting accuracy of bearing. The fitting requirements are as follows: the inner ring and shaft should adopt interference fit, and the interference amount is 0 ~ 4μm(0 in light load and high precision); The outer ring and the bearing seat hole adopt clearance fit, the clearance amount is 0 ~ 6μm(but when the free end bearing uses angular contact ball bearing, the clearance can also be increased); The roundness error of the shaft and the seat hole surface is less than 2μm, the parallelism of the end face of the bearing ring is less than 2μm, and the runout of the inner end face of the shaft shoulder is less than 2μm; The runout of the bearing seat hole shoulder to the axis is below 4μm; The runout of the inner end of the spindle front cover facing the axis is less than 4μm.

(2) The fixed end front bearing is installed on the shaft, and the bearing is thoroughly cleaned with clean cleaning kerosene. For grease lubrication, the organic solvent containing 3% ~ 5% grease is injected into the bearing for degreasing and cleaning, and then the oil gun fills the bearing with a certain amount of grease (accounting for 10% ~ 15% of the bearing space volume); The bearing is heated up 20 ~ 30℃, and the bearing is loaded into the shaft end with an oil press; The clamping sleeve is pressed on the shaft and pressed against the bearing end face with appropriate pressure to make its axial positioning; Roll the belt of the spring balance over the outer ring of the bearing and check for a significant change in the specified preload by measuring the starting torque (even if the bearing is correct, there may be a change in preload due to fit or cage deformation).

(3) Load the bearing and shaft assembly into the seat hole, heat the seat hole to temperature 20 ~ 30℃, and load the bearing and shaft assembly into the seat hole with continuous light and slow pressure; Adjust the front cover, so that the fastening amount of the front cover is 0.02 ~ 0.05μm, with the outer end face of the bearing seat as the benchmark, the dial table head conflict on the surface of the journal, the shaft rotation measurement of its runout, the error is required to be less than 10μm; The dial meter is positioned on the shaft, the watch head conflicts with the inner surface of the backseat hole, and the shaft is rotated to measure the coaxiicity of the front and rear seat holes of the bearing seat.

(4) The free end bearing is selectively placed in the position that may offset the deviation, installed to the bearing seat after the support position, as far as possible to offset the roundness deviation and coaxiality deviation between each other.