In ensuring the spindle manufacturing precision and accuracy of bearing at the same time, choose the appropriate bearing preloaded and use the measures such as directional error of bearing assembly can also be further improve the rotation precision and rigidity of spindle component, for different types of bearings, pre-tightening device and method is also different, prestressing methods commonly used for "machine design foundation" books, go here.
1. Alignment error assembly of rolling bearings
The front end of the spindle must have a positioning surface (cylindrical surface or front taper hole surface). Before mounting the bearing, it is necessary to measure the runout of the radial circle of the bearing inner ring and the positioning surface, and then assemble the bearing according to the directional assembly method, so as to improve the rotation accuracy of the spindle.
1) The spindle with an outer cylinder surface
Due to the processing technology, the runout of the radial circle on the surface of the spindle's journal is not only in the same axial plane but also in the same direction as the positioning surface of the outer cylinder at the front end. Therefore, the runout has little influence on the bearing assembly. During assembly, the maximum radial runout of the front and rear axes should be located in the same axial plane and on the same side of the axis, so as to reduce the radial runout of the end of the spindle and improve the rotation accuracy of the spindle.
2) The spindle with a tapered surface
Because of the processing technology, the surface of the spindle journal and the surface of the taper hole cannot be processed in a single clamping, which will inevitably produce radial circular runout relative to the axis. During assembly, the radial runout of the front and rear bearing inner rings of the spindle and the deviation of the spindle's cone-hole center line should be placed in the same axial plane and assembled in a certain direction to improve the rotation accuracy of the spindle.
2. Finishing after assembly
Special precision spindle assemblies, such as the spindle assembly for the jig boring machine, with spindle bearings mounted inside the sleeve, the runout tolerance of the spindle cone holes is only 1 m -- 2 m. In order to ensure the precision of the spindle assembly, the spindle assembly can be used after the finishing method, that is, the spindle assembly is well assembled, with taper holes at both ends of the spindle as a reference to fine grinding spindle sleeve outer circle; Then with the outer circle of the sleeve as the reference, fine grinding shaft taper hole.
If the bearing needs to be removed during repair after these methods are adopted for precision machine tools, marks should be made between the inner ring of the bearing and the spindle and between the outer ring and the box body (or the spindle sleeve) before removal. In assembly, marks should be made to ensure the precision after reinstallation.