To high precision bearings can meet the requirements of the precision we mainly pay attention to the following points:
1, improve the actual with the accuracy of the method in order to improve the actual fit precision of NSK bearing installation, must use the measurement methods and tools do not make the bearing deformation, precision measurements of NSK bearing inner hole and the outer circle with the surface size of the actual, the inner diameter and outer diameter measurement project all be measured, and make a comprehensive analysis of the measured data, according to this, installation position of the bearing precision worthy of shaft and housing bore size. In the actual measurement of the distribution of shaft and hole of appropriate size and shape, should be at the same temperature conditions and measurement of NSK bearings.
In order to guarantee the higher actual tie effect, the shaft and hole matched with the NSK bearing surface, the roughness should be as small as possible.
In the measurement, should be in the outer circle of NSK bearing inner hole, and the corresponding surface of the shaft and bore, on both sides near the assembly chamfer, make two groups of marker can show the maximum deviation direction, so that in the actual assembly, so that the maximum deviation to match the two party at the same range in this way, after the assembly, both of deviation to partially offset.
Make two sets of directional signs, is the deviation compensation can be considered, even supported at both ends of each rotating accuracy improved, and between the two bearing seat hole and the trunnion coaxiality error on both ends are partially eliminated. On the surface strengthening measures surface, such as sand blasting, precision plunger diameter slightly larger plug a hole, are beneficial to improve matching precision.
2, NSK precision bearings on the matching parts because of the requirements of precision NSK bearing accuracy within 1μ m, thus requiring matched parts ( shaft, bearing, end cover, ring ) has high dimensional accuracy and shape accuracy, especially with the surface precision control in NSK bearing the same level inside, this is extremely important, but also the most easily overlooked.
We must also pay attention to matching parts precision NSK bearing if not up to the requirements above, often make the precision bearing occurred several times larger than the original bearing error after installation error, even 10 times more, not be precise NSK bearing, the reason is the error matching parts are not simply added to the error of NSK bearing the different magnification, but to add the following.
3, in order to ensure the precision of NSK bearing with the bearing after installation without excessive deformation, must do:
(1 ) of the fixing ring to take small interference fit condition is matched both have very high surface shape accuracy and smaller roughness, otherwise cause difficult installation and removal more difficult, in addition, also need to consider the influence of the spindle thermal elongation.
( 2 ) the main use of duplex mounting angular contact ball bearings, multiple half-load lighter, the amount of interference such as too large, the axial preload of its internal will be significantly larger, adverse effects. Main use of double row short bearing and spindle bearings, the load is relatively large, so the interference fit is relatively large.
( 3 ) the roundness of the shaft and hole and verticality shoulder according to the corresponding precision bearing NSK requirements.
( 4 ) to calculate the amount of interference of rotating rings fit, to accurately calculate the appropriate amount and fixed rings.
Rotating ring interference where possible should be made smaller. As long as the guarantee of working temperature thermal expansion effects, as well as the highest speed under the effect of centrifugal force, without causing tight fit creeping or sliding on the surface. Fixed rings depending on load size and NSK bearing size, select a very small clearance fit or interference fit, too loose or too tight is not conducive to precise shape.
( 5 ) NSK bearing such as running in the condition of high speed, and high working temperature, special attention should be paid to cooperate with rotating rings must not be too loose, to prevent the emergence of the eccentric vibration, cooperate with and fixed rings do not appear gap, to prevent the ring under load deformation and vibration excitation.