Chen Ye, Zhao Xiangsong, Gao Weiguo, Hu Gaofeng, Zhang Shizhen, Zhang Dawei
Tianjin Key Laboratory of Equipment Design and Manufacturing Technology, School of Mechanical Engineering, Tianjin University, Tianjin 300072, China.
Beijing Machine Tool Research Institute, Beijing 101312, China.
Rev Sci Instrum. 2016 Dec;87(12):125102. doi: 10.1063/1.4968042.
The rotational accuracy of a machine tool spindle has critical influence upon the geometric shape and surface roughness of finished workpiece. The rotational performance of the rolling element bearings is a main factor which affects the spindle accuracy, especially in the ultra-precision machining. In this paper, a new method is developed to measure the rotational accuracy of rolling element bearings of machine tool spindles. Variable and measurable axial preload is applied to seat the rolling elements in the bearing races, which is used to simulate the operating conditions. A high-precision (radial error is less than 300 nm) and high-stiffness (radial stiffness is 600 N/μm) hydrostatic reference spindle is adopted to rotate the inner race of the test bearing. To prevent the outer race from rotating, a 2-degrees of freedom flexure hinge mechanism (2-DOF FHM) is designed. Correction factors by using stiffness analysis are adopted to eliminate the influences of 2-DOF FHM in the radial direction. Two capacitive displacement sensors with nano-resolution (the highest resolution is 9 nm) are used to measure the radial error motion of the rolling element bearing, without separating the profile error as the traditional rotational accuracy metrology of the spindle. Finally, experimental measurements are performed at different spindle speeds (100-4000 rpm) and axial preloads (75-780 N). Synchronous and asynchronous error motion values are evaluated to demonstrate the feasibility and repeatability of the developed method and instrument.
机床主轴的旋转精度对成品工件的几何形状和表面粗糙度有着至关重要的影响。滚动元件轴承的旋转性能是影响主轴精度的一个主要因素，尤其是在超精密加工中。本文提出了一种测量机床主轴滚动元件轴承旋转精度的新方法。通过施加可变且可测量的轴向预载，使滚动体在轴承滚道中就位，以此来模拟工作条件。采用高精度（径向误差小于300纳米）和高刚度（径向刚度为600牛/微米）的静压基准主轴来旋转测试轴承的内圈。为防止外圈旋转，设计了一种二自由度柔性铰链机构（2-DOF FHM）。采用基于刚度分析的修正因子来消除二自由度柔性铰链机构在径向方向上的影响。使用两个具有纳米分辨率（最高分辨率为9纳米）的电容式位移传感器来测量滚动元件轴承的径向误差运动，而不像传统的主轴旋转精度测量那样分离轮廓误差。最后，在不同的主轴转速（100 - 4000转/分钟）和轴向预载（75 - 780牛）下进行了实验测量。通过评估同步和异步误差运动值，来证明所开发的方法和仪器的可行性和可重复性。
