Abstract
As a key parameter, stiffness determines the dynamic characteristics of both the bearing and the spindle unit. However, interactions between the spindle speed, initial preload, and cutting force caused by the thermal expansion of spindle unit components alter the bearing stiffness characteristics during the running process. Aiming to carry out real-time online monitoring of the thermal characteristics and their effect on the machine tool spindle bearing stiffness, a fiber Bragg grating (FBG) sensors network was proposed. Further, the effects were considered under various axial loads, combined axial, and specific radial load to study bearing temperature increase, thermally induced preload, and thermal stiffness. The results have shown that the bearing thermal stiffness of the bearing decreases with the increase of the spindle speed. Moreover, an optimal initial preload can be selected with respect to the speed to maximize the thermal stiffness. Finally, the thermally induced preload additionally pre-tightened the bearing.
Highlights
As the core component of the spindle unit, angular contact bearing is widely used in high speed spindle unit cause enduring high speed, axial and radial force simultaneously
Aiming at real-time online monitoring of the thermal characteristics of machine tool spindle bearing stiffness, this paper proposed a fiber Bragg grating (FBG) sensors network
The results show that the thermal stiffness of the bearing decreases with the increase of the spindle speed, and there is an optimal initial preload at the speed to maximize the thermal stiffness of the bearing, and the thermally induced preload has an additional pre-tightening effect on the bearing
Summary
As the core component of the spindle unit, angular contact bearing is widely used in high speed spindle unit cause enduring high speed, axial and radial force simultaneously. Exploring the bearing thermal stiffness characteristics should consider the spindle speed, cutting loads and initial preload which is necessary for angular contact bearing. Wu Wenwu et al.[5, 6] studied the influences of non-uniform load on bearing thermal performance under different preloads and established the stiffness function for calculating the local contact deformation of angular contact ball bearings with uneven preload through analysis to predict the stiffness of the bearing. In order to solve this problem, this paper uses the measurement advantages of FBG "one line and multiple points"[10], builds a real-time online monitoring system for the service status of the FBG embedded spindle bearing to complete the thermal characteristic test of the spindle unit, and explores the change law of spindle bearing thermal stiffness under the action of spindle speed, initial preload and cutting force
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