1. NSK bearings precision improving method
NSK bearings after installation in the host, such as measurement of NSK bearings of spindle runout, but found its spin measured value has a certain amount of change; continuous measurements, can be found after a certain speed after, this change will approximate repeats. Indicators for measurement of that variability cycle running accuracy, changes required to approximate repeats to a few representative robin rotation accuracy of "cycles", measure changes in quasi periodic large amplitude, is the circular rotation accuracy is poor.
As to appropriate preload the NSK bearing spindle, gradually raise the speed to close to the speed in order to implement bearing "break-in" effect, improves the cycle of spindle running accuracy.
2.NSK bearing mounting accuracy of integrated method of verification
After the angular contact ball bearing into the spindle, the precision calibration sequence is as follows (with shaft diameter for the lathe of 60-100mm as an example):
(1) fixed end Qian bearing in axis Shang of installed: will bearing with clean of cleaning kerosene for thoroughly cleaning, for fat lubrication, first will contains 3%~5% grease of organic solvent injected bearing made skim cleaning Hou, again with oil gun will quantitative of grease filled into bearing within (accounted for bearing space volume of 10%~15%); heating bearing makes warming 20~30℃, with hydraulic machine will bearing loaded into axis end; will tight will sets pressure in axis Shang and to suitable of pressure arrived live bearing end surface makes its axis to positioning ; Tape volumes on the bearing outer ring of the spring scale, a measurement method of starting torque preload under the check whether there is a substantial change (even if the bearing is very correct, but because of the tie or cage deformation, preload changes possible).
(2) will NSK bearing-axis combination body loaded seat hole: heating block hole makes warming 20~30℃, with continuous mitigation of pressure will bearing-axis combination body loaded seat hole; adjustment Qian cover, makes Qian cover of tight solid volume for 0.02~0.05 μ m, to bearing block outside end surface for benchmark, will indicator of table head subject to in axis neck surface Shang, will axis rotating measurement its beat, requirements errors in 10 μ m following; will indicator positioning in axis Shang, table head subject to Hou block hole within surface, Axis to measure coaxiality of hole, before and after the housing block.
(3) place the free end bearing selectively in may offset the location of deviation, installed into the housings support locations, offset the roundness deviation and with each other as much as possible with axis deviation.
(4) measurement axis and bearing block hole of size, to determines bearing of combined with precision, combined with requirements is as follows: within circle and axis take had full combined with, had full volume 0~+4 μ m (in light load, and high precision Shi for 0); outer ring and bearing block hole take gap combined with, gap volume 0~+6 μ m (but in free end of bearing using corner contact ball bearing Shi, also can increases gap); axis and block hole surface round of errors in 2 μ m following, bearing by with across circle of end surface parallel of in 2 μ m following, Shaft inner end face of outer face beat in 2 μ m below bearing block hole of pulsation of the abutments on axis 4 μ m below axis front inner end face runout of spindle below the 4 μ m.
3. a method for improving the accuracy of NSK bearings
A factory trial precision instruments, spindle with 6202/P2 type bearing and its precision still cannot meet requirements, Hou plus rough axis neck and in its Shang produced roll road to instead of within ring, and will steel ball for precision measurement, to size size each three grain a group, each group steel ball take close to 120 ° of interval separated, due to reduced has a heavy processing surface, also reduced has a heavy tie surface, while also improve has axis a bearing system of stiffness, and maximum three grain and minimum three grain steel ball of close to raster distribution, also improve has axis of Rotary precision, Instrument accuracy requirement is met.


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