1. Causes of pure radial runout of spindle
The pure radial runout of the main shaft is caused by the accuracy error between the main shaft journal and the bearing. Bearings used on machine tools are divided into sliding bearings and rolling bearings. Different types of bearings have different effects on pure radial runout.
(1) Influence of sliding bearing on pure radial runout of main shaft
When the sliding bearing is used as the support, the main shaft rotates in the bearing hole with its journal. For lathe type machine tools, in the processing process, the force direction of the spindle is certain, and the spindle journal is pressed to the fixed place on the surface of the bearing hole by the cutting force. At this time, different parts of the main shaft journal are in contact with a fixed part in the bearing hole, so the roundness error of the journal will cause pure radial runout of the main shaft rotation, and the shape error of the bearing hole has little effect on the rotation accuracy of the main shaft.
(2) Influence of rolling bearing on pure radial runout of main shaft
When the main shaft is supported by rolling bearings, the factors that cause the pure radial runout of the main shaft are not only the accuracy of the bearings themselves, but also the accuracy of the bearing mating parts.
2. Influence of pure radial runout of spindle on part machining
(1) Influence on boring machining
When boring on the boring machine, the boring cutter rotates with the spindle of the boring machine. When the spindle makes pure radial runout, it will make the axis move harmoniously along a fixed direction. The boring hole shape is determined by the movement track of the boring tool tip in the inertial coordinate system.
(2) Influence on turning
When machining excircles or boring holes on the lathe, the workpiece rotates with the lathe spindle. Therefore, the geometry of the machined surface of the workpiece is determined by the relative trajectory of the tool in the moving coordinate system.
Through the analysis of the pure radial runout of the spindle, it can be seen that the spindle rotation error has a great impact on the machining accuracy of parts. Therefore, in machining, effective measures should be taken to reduce the influence of spindle rotation error on the machining accuracy of parts. The measures taken can be considered from two aspects. First, improve the rotation accuracy of the spindle. The second is to reduce the influence of spindle rotation error on parts processing.