液体静压主轴回转误差的形成机理研究

Study on the Mechanism of Hydrostatic Spindle Rotational Error Motion

液体静压主轴是精密、超精密机床的核心功能部件,虽然已在工程领域获得广泛应用,但其回转误差的形成机理长期以来并不明确。利用现有的静压主轴计算模型,难以对主轴从静平衡位置到动态回转误差轨迹的过渡过程进行定量精确的计算和仿真,难以揭示出回转误差运动的扰动因素与主轴位置、轴承流量和油膜力等因素之间的内在联系,因而不能从物理本质上合理解释静压主轴回转误差的形成机理。建立了液体静压主轴回转误差的动力学模型,采用全程动网格方法、平衡位置动网格方法和平衡位置油膜刚度阻尼等三种方法,定量再现了主轴从轴颈与轴承的同心初始位置到形成回转误差运动轨迹的过渡过程,揭示了静压主轴形成平均回转中心和回转误差时扰动因素与主轴合力、轴承流量和轴心位置之间的相互影响规律。采用最小二乘法对回转误差轨迹进行评价,对比分析了三种方法计算结果存在差异的原因,提出了可同时兼顾计算效率和计算精度的将动网格与油膜刚度阻尼相结合的回转误差计算方法。

Hydrostatic spindles are core components of high precision machine tools, which have been widespread used in mechanical engineering, but the mechanism of rotation error has not been revealed clearly. According to current documents and models, the transient processes of the spindle from an equilibrium position to a dynamical orbit could not be simulated quantitatively. The intrinsic relationship among the disturbance factors, the position, the flow and the oil film force could not be revealed, as resulted in that the mechanism of the rotational error motion of hydrostatic spindle could not be described exactly. The dynamic model of the rotation error motion of hydrostatic spindles is established. Three methods, which are full process moving mesh method, equilibrium position ＆ moving mesh method, and equilibrium position ＆ simplified formula method, are used to quantitatively calculate the trajectory of a spindle from the concentric position to forming rotational error. The inherent laws among the disturbance factor, total force, the flow and the position are discovered. The rotation error is evaluated by using of the Least squares method. By studying the influence of these three calculation methods on the rotary centre position and rotary error, the reasons that results in calculation difference are found. The method which combines the moving mesh method and the simplified formula to calculate the rotary accuracy of hydrostatic spindle are verified to be efficient and pinpoint.