After the bearing is installed in the main engine, if the radial runout of the main shaft is measured, it can be found that the measured value of each revolution has a certain change; when continuous measurement is performed, it can be found that after a certain number of revolutions, this change will be approximately repeated. Appear. The index to measure the degree of this change is the cyclic rotation accuracy. The number of revolutions required for the change to appear approximately repeats represents the "quasi-period" of the cyclic rotation accuracy. The magnitude of the change in the quasi-period is large, which is the poor cyclic rotation accuracy. .
If appropriate preload is applied to the main shaft, the speed is gradually increased to close to the working speed, so as to implement the "run-in" effect of the bearing, which can improve the cyclic rotation accuracy of the main shaft.
One way to improve the accuracy of bearings is to use 6202/P2 type bearings for the main shaft, but the accuracy still cannot meet the requirements. In the measurement of waxy density, there are three groups of steel balls in size, and each group of steel balls is separated by an interval of nearly 120°. Due to the reduction of a heavy machining surface and a reduction of a heavy mating surface, the rigidity of the shaft-bearing system is improved at the same time. The nearly equidistant distribution of the big three steel balls and the small three steel balls improves the rotation accuracy of the shaft, thus meeting the accuracy requirements of the instrument
Clean the bearing with clean cleaning kerosene. For grease lubrication, first inject an organic solvent containing 3% to 5% grease into the bearing for degreasing and cleaning, and then use an oil gun to fill the bearing with a certain amount of grease (accounting for the bearing). 10% to 15% of the space volume); heat the bearing to raise the temperature to 20 to 30°C, and install the bearing into the shaft end with a hydraulic press; press the adapter sleeve on the shaft and press the bearing end face with 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 prescribed preload has a large change by measuring the starting torque (even if the bearing is correct, the preload also changes due to the deformation of the fit or cage). possible).
Put the bearing and shaft assembly into the seat hole and heat the seat hole to raise the temperature by 20 to 30°C. Use continuous gentle pressure to install the bearing and shaft assembly into the seat hole; adjust the front cover so that the tightening amount of the front cover is 0.02 ～0.05μm, take the outer end face of the bearing seat as the benchmark, put the head of the dial indicator against the surface of the journal, rotate the shaft to measure the runout, and the error is required to be less than 10μm; position the dial indicator on the shaft, the head Against the inner surface of the rear seat hole, rotate the shaft to measure the coaxiality of the front and rear seat holes of the bearing seat.
The free end bearing is selectively placed at the position where the deviation may be offset, and is installed at the rear support position of the bearing seat to offset the mutual roundness deviation and coaxiality deviation as much as possible.
