Methods To Improve The Installation Accuracy Of IKO Bearings

After the IKO bearing is installed in the main machine, if you measure the radial runout of the main shaft, you can find that the measured value of each revolution has a certain change; when you perform continuous measurements, you can find that after a certain number of revolutions, the change will be approximately Repeatedly. 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 repeatedly represents the “quasi-period” of the cyclic rotation accuracy. The magnitude of the change in the magnitude within the quasi-period is large, which is the cyclic rotation accuracy difference. .
If appropriate preload is applied to the spindle and the speed is gradually increased to close to the operating speed to achieve the “running-in” effect of the bearing, the cyclic rotation accuracy of the spindle can be improved.

2. A method to improve bearing accuracy
   A factory trial-produced precision instruments. The spindle used a 6202/P2 bearing, but its accuracy still could not meet the requirements. The journal was then thickened and a raceway was made on it to replace the inner ring. The steel balls were precisely measured and the size was determined for each. There are three balls in a group, and each group of steel balls is separated at an interval of close to 120°. This reduces one layer of processing surface and reduces one layer of mating surface. At the same time, it increases the stiffness of the shaft-IKO bearing system, and the maximum three balls and the minimum three balls are The nearly equidistant distribution of granular steel balls also improves the rotation accuracy of the shaft, thus meeting the accuracy requirements of the instrument.
3. Comprehensive verification method for installation accuracy
   After installing the angular contact ball bearing into the spindle, the installation accuracy verification sequence is as follows (taking an ordinary lathe with a shaft diameter of 60 to 100 mm as an example):
   (1) Measure the dimensions 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 an interference fit, and the interference amount is 0~+4μm (0 at light load and high precision); the outer ring and the bearing seat hole adopt a clearance fit, and the clearance amount is 0~+6μm (but the bearing at the free end When using angular contact ball bearings, the gap can also be increased); the surface roundness error between the shaft and the seat hole is less than 2 μm, the end face parallelism of the spacer used in IKO bearings is less than 2 μm, and the runout of the inner end of the shaft shoulder to the outer end face is less than 2 μm. ; The runout of the bearing seat hole shoulder to the axis is less than 4 μm; the runout of the inner end of the spindle front cover to the axis is less than 4 μm.
   (2) Installation of the fixed end front bearing on the shaft
   Thoroughly clean the IKO bearings with clean cleaning kerosene. For grease lubrication, first inject an organic solvent containing 3% to 5% grease into the bearings for degreasing and cleaning, and then use an oil gun to fill a certain amount of grease into the bearings ( (accounting for 10% to 15% of the bearing space volume); heat the bearing to raise the temperature by 20 to 30°C, and install the bearing into the shaft end with a hydraulic press; press the adapter sleeve on the shaft and use appropriate pressure against the bearing end surface to make the shaft Position the spring scale in the direction; wrap the strap of the spring scale around the outer ring of the bearing, and use the method of measuring the starting torque to verify whether the specified preload has changed significantly (even if the bearing is correct, the preload may change due to the deformation of the fit or cage) It is also subject to change).
   (3) Install the bearing-shaft assembly into the seat hole
   Heat the seat hole to raise the temperature by 20 to 30°C, and install the bearing-shaft assembly into the seat hole with continuous gentle pressure; adjust the front cover so that the tightening amount of the front cover is 0.02 to 0.05 μm, with the outer end surface of the bearing seat as As a benchmark, touch the dial indicator head against the surface of the journal, rotate the shaft to measure its runout, and the error is required to be below 10 μm; position the dial indicator on the shaft, touch the dial indicator head 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) Selectively place the free end bearing in a position where the deviation can be offset, and install it at the rear support position of the bearing seat to offset the mutual roundness deviation and coaxiality deviation as much as possible.