Research And Optimization Of The Thermal Characteristics Of The Hydrostatic Spindle

Micro-Nano imprinting rollers are the core components for the manufacture of various precision optical functional films,and the diamond turning is the most efficient way to realize the ultra-precision manufacture of the rollers.The hydrostatic spindle,with lots of advantages such as high stiffness,high rotation accuracy,high vibration resistance,high damping,and long life,is a crucial component of ultra-precision single-point diamond turning machine tools.Thermal Characteristics of the spindle means performance changes due to thermal effects generated,including changes of the carrying capacity and the thermal deformation.Due to the heating of the built-in motor and the heating of the bearing,the overall temperature of the system rises,and the distribution is uneven,which leads to stress concentration and deformation-finally resulting in machining errors during the working process of the hydrostatic spindle.For ultra-precision machine tools,the thermal characteristics are important factors affecting the processing perfonnance.It is of considerable significance to study the thermal characteristics to improve the processing quality and processing accuracy.The research object of this paper is the hydrostatic spindle of an ultra-precision horizontal roller diamond lathe.In order to study its thermal characteristic,firstly,based on the working principle of the spindle,a theoretical model of the analysis of the thermal characteristics of the spindle is established based on the assumption of fluid continuity.The model includes the raw thermal model of the spindle,the bearing model,and the theoretical model of the finite element analysis.Through the model,the heat generation mechanism of the spindle can be clarified,the main factors affecting the thermal characteristics of the spindle are identified,the influence law on the thermal characteristics of the spindle are analyzed,and the boundary conditions required for finite element simulation are calculated.This model rammed the foundation for the finite element numerical simulation.In the case of clarifying the thermal boundary conditions of the spindle system,a one-way "thermal-flow-solid”coupling numerical simulation was performed based on the data exchange between the ANSYS Workbench and the Fluent platform.Firstly,the pressure field and temperature field distribution of the radial bearing and the thrust bearing are calculated,and the results are transferred as boundary conditions into the solid spindle system,and then the temperature field of the spindle system and the thermal deformation field are calculated.So far,a complete set of heat Finite element analysis model of thermal characteristics of the spindle system was established.The model can be used to simulate the thermal characteristics of the spindle under different working conditions.Based on numerical simulation,the experiment was designed and tested to verify the correctness and accuracy of the simulation results.The temperature measurement experiment was carried out to measure the actual temperature rise of the spindle at different temperature points under the working condition.The average error is 10.5%,the minimum error is 0.3%,and the maximum error is 17.5%.The simulation results of the spindle system temperature field were verified.The displacement measurement experiment was carried out to measure the axial elongation of the spindle under the working condition.Compared with the simulation results,the error is 2.5%.The simulation results of the thermal deformation field of the spindle system are verified.The fluctuation experiment of the spindle is carried out to verify the change rule of spindle bearing capacity with temperature rise,which is consistent with the trend of numerical simulation results.The established theoretical model and the finite element simulation model are used to optimize the thermal characteristics of the spindle,and a complete optimization design process is designed.The main structural parameters affecting the thermal characteristics of the spindle are optimized so that the overall heat generation of the spindle reduced by about 30%,the spindle radial stiffness increased by 2.38 times.At the same time,based on the optimized spindle parameters,the model was re-modeled to optimize the appearance and size structure of the spindle.