1. Precision improvement method of fag bearing
After fag bearing is installed in the main engine, if the radial runout of fag bearing spindle is measured, it can be found that the measured value of Installing each revolution has a certain change; During continuous measurement, it can be found that this change will approximately repeat after a certain number of revolutions.
The index to measure the degree of change is the cyclic rotation accuracy. The number of revolutions required Installing for the approximate repetition of the change represents the “quasi period” of the cyclic rotation accuracy. The large magnitude change in the quasi period is the poor cyclic rotation accuracy.
If the fag bearing spindle is properly preloaded and the speed is gradually increased to close to the working speed, so as to implement the Installing “running in” function of the bearing, the cyclic rotation accuracy of the spindle can be improved.
2. A method to improve the accuracy of fag bearing
A precision instrument is trial produced in a factory. The main shaft uses 6202 / P2 bearing, but its accuracy still can not meet the Installing requirements. After that, the journal is thickened and a raceway is made on it to replace the inner ring, and the steel balls are accurately measured.
Each group of steel balls is divided by three particles in size, and each group of steel balls is separated by an interval of nearly 120 °. Due to the reduction of one heavy machining surface and one heavy fitting surface,
At the same time, the stiffness of the shaft bearing system is improved, and the nearly equidistant distribution of large three particles and small three particles improves the rotation Installing accuracy of the shaft, so it meets the accuracy requirements of the instrument.
After the angular contact ball bearing is installed into the main shaft of fag bearing, the verification sequence of installation accuracy is as follows Installing (take the ordinary lathe with shaft diameter of 60-100mm as an example):
(1) Measure the size of the shaft and bearing seat hole to determine the matching accuracy of the bearing. The matching requirements are as follows: the inner ring and the shaft adopt Installing interference fit with an interference amount of 0 ~ + 4 μ M (0 under light load and high precision);
Clearance fit is adopted between the outer ring and the bearing seat hole, with a clearance of 0 ~ + 6 μ M (but when the angular contact ball bearing is used for the bearing at the free end, the clearance can also be increased);
The roundness error between shaft and seat hole surface is 2 μ M below, the end face parallelism of the spacer used for the bearing is 2 μ M below, Installing the runout of the inner end face and the outer end face of the shaft shoulder is 2 μ Below m;
The runout of the shoulder of the bearing seat hole to the axis is within 4 μ Below m; The runout of the inner end of the front cover of the main shaft facing the axis is within 4 μ Below M.
(2) Installation of fixed end front Installing bearing on the shaft: thoroughly clean the bearing with clean cleaning kerosene. For grease lubrication, first inject organic solvent containing 3% ~ 5% grease into the bearing for degreasing and cleaning, and then fill a certain amount of grease into the bearing with an oil gun (accounting for 10% ~ 15% of the bearing space volume);
Heat the bearing to raise the temperature by 20 ~ 30 ℃, and install the bearing into the shaft end with an oil press; Press the set sleeve on the shaft and press the bearing end face with appropriate pressure to make it axially positioned;
Roll the belt of the spring scale on the outer ring of the bearing and check whether the specified preload changes greatly by measuring the starting torque (even if the bearing is correct, the preload may also change due to the deformation of the fit or cage).
(3) Install the fag imported bearing shaft assembly into the seat hole: heat the seat hole to raise the temperature by 20 ~ 30 ℃, and install the bearing shaft assembly into the seat hole with continuous and gentle pressure;
Adjust the front cover so that the fastening amount of the front cover is 0.02 ~ 0.05 μ m. Take the outer end face of the bearing seat as the benchmark, push the dial indicator against the journal surface, rotate the shaft and measure its runout.
The error is required to be within 10 μ Below m; Position the dial indicator on the shaft, push the indicator against the inner surface of the rear seat hole, and rotate the shaft to measure the coaxiality of the front and rear seat holes of the bearing seat.
(4) Place the free end bearing selectively at the position where the deviation can be offset, and install it at the rear support position of the bearing seat to offset the roundness deviation and coaxiality deviation as much as possible.