Study On Thermal-Structure Coupling Model And Thermal Characteristic Control Of High-Speed Spindle

The thermal and dynamic characteristics of the high-speed spindle have an important influence on the machining accuracy and efficiency of the machine tool.Because the preload can not be adjusted flexibly,the fixed position and constant pressure preload spindle cannot meet the comprehensive requirements of different processes for thermal and dynamic characteristics.In addition,the commonly used circulating cooling method can control the temperature rise of the outer ring of the bearing and the main shaft shell,but it has a weak inhibition on the temperature rise of the rotor.Aiming at the above problems,this paper mainly studies the modeling and simulation methods of high-speed spindle thermal-structure coupling,and the thermal characteristic control device and method based on preload.Based on Jones' bearing model,the nonlinear model of angular contact ball bearing is established by considering the thermal deformation and displacement of inner and outer rings of bearing caused by thermal effect and centrifugal force of spindle,thermal expansion of ball and gyroscopic moment.On this basis,the thermal-structure coupling model is established by taking the spindle with fixed position and series back-to-back bearing as an example.The influence of thermal and centrifugal force effect on the heat generation power of bearing,and the influence of temperature and speed change on the heat transfer model of spindle are analyzed.Based on this,a coupling simulation method is proposed,and a case simulation and experimental verification are carried out.The results show that the coupling simulation method is more accurate than the traditional transient temperature field simulation method,and reveals the thermal-structure coupling mechanism.This method is also suitable for other types of spindles,which can provide guidance for the design and control of thermal characteristics of spindle and the performance monitoring of spindle running state.Aiming at the typical structure of variable preload spindle based on piezoelectric actuator,the static and dynamic models are established,and the preload model of varible preload spindle is established according to the output characteristics of piezoelectric actuator.Based on this,the influence of stiffness of piezoelectric actuator and initial preload on preload adjustment range and first order natural frequency are analyzed,and the design and selection principle of preload mechanism is proposed.Finally,a variable preload spindle system with integrated temperature detection function is designed to verify the correctness of the above principles and provide a hardware basis for thermal characteristic control.In order to suppress the axial thermal error,the objective of keeping the temperature field unchanged before and after the change of processing parameters is proposed.Based on the influence mechanism of the preload on the temperature rise of spindle and from the perspective of heat source,a control strategy of equal change of heat generation and heat dissipation power of bearing is proposed,based on which,the preload adjustment value can be calculate under the objective of this paper.At the same time,the position mutation of the front end of the spindle caused by the adjustment of the preload is calculated theoretically.After the position mutation is compensated by numerical control system,the theoretical axial thermal error is zero.Through the experiment,the temperature rise,front displacement and rotation accuracy of the spindle under the control of the thermal characteristics based on preload and fixed position preload are compared before and after the change of processing parameters,which shows the effectiveness of this method.