Nc machine tool for precision demanding, there is strict technical characteristic of spindle component.
General matching using spindle are bearing, the points after the front end, bearing structure for the 2 + 2, 2, 3 + 4 + 2, etc.
Such as the front two bearing assembly two bearing spindle bearing installation, should make before and after two of eccentricity in the same direction of supporting bearing installation, properly choose the size of the eccentricity, the precision of the front bearing should be higher than the accuracy of the rear bearing, after making the assembly of the front end of the spindle assembly location on the surface of the eccentric quantity is small.
Rolling bearings rolling bearing clearance and preload when there is a big gap, load will focus on the stress direction on a few rolling body, make the bearing stiffness, bearing capacity drops, low stress, rotating accuracy is poor.
Will be appropriate rolling bearing preload, rolling body contact with the inner and outer ring raceway in place to produce predeformation, increased the number of rolling element bearing, after loading force uniform trend, improve the bearing capacity and stiffness, is advantageous to the reduction of spindle axis drift, improve the rotation accuracy.
The interference if the amount is too large, friction and wear of the bearing increased, the force will be decreased significantly, the relationship between the bearing life and clearance as shown in figure 7
14 on the machining center, angular contact ball bearing installed on the main shaft, bearing and spindle, generally USES 1 -
5 um interference fit;
Bearings with holes, using 0
5 um clearance fit.
Spindle assembly USES period of time, bearing wear gap will increase, will be the new adjust the clearance.
As a result, the spindle assembly must have bearing clearance adjustment of the structure.
Angular contact ball bearing clearance adjustment and preload method as shown in figure 7
Pairs made is to use angular contact ball bearing inner ring end face or outer end face grinding after implementation.
Bearing manufacturer quantity in pairs according to the requirements of the preload, assembly don't need to adjust, and close it with the nut after can obtain precise pre-tightening force.
Due to the use of cannot adjust, maintenance more troublesome.
Figure 7 -
16 for every set of adjustment method.
Using two sets of adjusting, through two sets of the width of the poor, adjust bearing clearance.
Or in the bearing outer ring spacer, assembly with a nut and pre-tightening force inner ring to get what you need.
This adjustment methods don't have to remove the bearing, the size of the pre-tightening force on worker's experience to determine.