液体静压主轴的回转精度规律及其极限预测

The Laws and Ultimate Prediction of Rotation Accuracy for Hydrostatic Spindle

液体静压主轴是精密、超精密机床的核心功能部件,对机床的加工效率、加工精度和加工表面质量具有直接而重要的影响。回转精度是液体静压主轴的关键性能,目前学术界和工程界对回转精度的各种评价指标之间的内在联系尚缺乏统一认识,对回转精度的机理和形成规律尚缺乏深入研究。系统分析了回转精度各种评价指标和测试方法之间的内在联系,明确了不同误差成分的来源和成因;针对现有回转精度评价方法的局限性,提出了"最小峰峰值+同步误差+异步误差"的综合评价方法。系统比较了不同节流方式对液体静压轴承刚度的影响规律,提出了采用可控节流实现高回转精度的方法。建立了可控节流液体静压主轴的流固热耦合模型,实现了轴心运动轨迹形成过渡过程的精确定量仿真,揭示了供油压力、供油压力波动、动不平衡量和轴颈圆度误差对回转精度的影响规律。最后对液体静压主轴可能达到的回转精度极限进行了预测。

Hydrostatic spindles are crucial core components for the precision and ultra-precision machine tools,which have direct and significant influence on the processing efficiency,machining accuracy and machined surface quality.The rotation accuracy is the key performance of hydrostatic spindle systems.At present,there is a lack of unified cognition of the intrinsic relationship with various evaluation indexes of rotation accuracy in academic and engineering communities,besides,the mechanism and formation law of rotation accuracy still need in-depth investigations.The intrinsic relationships between various measuring methods and evaluation indexes of rotation accuracy are systematically analyzed.The formation causes of different error components are clarified.Finally,aiming at the limitation of the existing evaluation methods of rotation accuracy,a comprehensive evaluation method of"minimum peak-to-peak value+synchronous error+asynchronous error"is proposed.On the basis of systematically coMParing the influence of different throttling methods on the hydrostatic journal bearing stiffness,the method of adopting controllable restrictor to achieve higher rotation accuracy is put forward.The flow-structure-thermal coupling model of the hydrostatic spindle is established to achieve the accurate quantitative simulation of the transient process of the axial motion trajectory,which further revealed the laws of oil supply pressure,fluctuation of oil supply pressure,the dynamic unbalance and the journal roundness error on the rotation accuracy.Ultimately,the attainable extreme limit of rotating accuracy for hydrostatic spindle system is predicted.