一种气浮主轴径向回转误差的测量方法

详细论述了双传感器转位法测量气浮主轴径向回转误差的基本原理,该方法能有效地分离出主轴的回转误差和标准钢球的圆度误差,通过消除一次谐波来去除安装偏心。并且设计了回转误差的测试系统,该系统能满足测量的要求。     

机床主轴径向回转误差的测试与研究

给出了一种主轴回转误差动态测量的误差分离方法,提出了一套主轴回转精度的动态测试系统.该系统由位移测试单元、采样时钟单元、数据采集卡、通用计算机及数据处理软件组成.该系统用于电主轴回转精度的实际测量,取得了良好效果.     

高速主轴回转误差测试装置研究

主轴回转误差是影响加工精度的关键因素,利用3个电涡流传感器对安装在主轴前端的标准棒进行动态测试,利用设计好的支架,将3个电涡流传感器安装在主轴三维笛卡尔坐标的3个方向上,电涡流采集的3个方向上的位移信号在计算机中显示.通过试验研究,实现了良好的检测结果.     

液体静压电主轴回转精度测量与结果分析

为解决高精密液体静压电主轴回转误差难以精密测量与分离的问题,提出了一种主轴回转精度测量与分析的新方法。以液体静压电主轴为测量对象,设计一套以电容微位移传感器为基础,以VC++和Matlab为软件平台的主轴回转误差测量系统,采用自为基准原理,以机床精车后的工件代替传统的检验棒进行直接测量,利用频域三点误差分离法,对主轴回转误差和圆度误差进行测量与分析。实验表明该系统能对高精密主轴回转误差进行测量,在转速(0⁶00)r/min范围内,该主轴的回转误差为0.28μm。     

精密球面磨床主轴回转误差的高精度测量

利用主轴回转误差单点测量法设计了一套测量系统,该系统由高精度标准球、高精度非接触位移传感器和角度传感器组成.阐述了回转误差的测量原理,分析了测量过程中可能引入的测量误差及其消除方法,并进行了实验研究.通过测量系统对测量数据进行了自动获取和分析处理,并用最小二乘法对测量数据进行评定,实现了精密球面磨床主轴回转误差的高精度测量.     

数控车床主轴热变形检测及回转精度评定

针对主轴回转热误差包含的多种误差分量,采用双向正交法测量了不同转速温度场下数控车床主轴热变形所引起的回转误差。以复向量描述主轴回转精度理论为基础,利用FFT误差分离方法,从传感器测得的信号中分离并去除检棒的安装偏心及热变形导致的回转中心的偏移量,从而得到精确的主轴回转热误差信息,进而评定数控机床主轴热变形对加工精度的影响。     

基于软件同步的机床主轴回转精度测试

机床主轴回转精度反映了主轴回转时轴心线在空间所产生的运动误差,该误差是机床加工误差的主要来源之一。传统测试方法的理论非常成熟,但是测试时的安装非常不方便。本文分析了软件同步技术的原理和适用场合之后,并将该原理运用到车床回转精度测试系统的数据前处理过程中,替代了传统的角度测试装置——编码器。该技术的运用降低了车床主轴测试安装要求,使测试系统更适用于现场测试;同时也降低了测试系统的成本,提高了其适应性。     

车床主轴回转精度数字式单向测量法北大核心

车床主轴回转精度的测量是一项重要的测试课题。针对传统的测量方法需要使用基圆发生器,数据处理困难,测试结果难以在各车床间进行比较等问题,提出了利用数字式单向测量法对车床主轴回转误差进行动态测量。从分析回转误差的测试原理和误差性质出发,建立起回转误差的数学模型,利用信号分析的手段分离出基准球安装偏心误差,并通过计算机仿真对该数学模型及分离方法进行验证和分析。实验结果表明,采用本文的方法对C616主轴回转精度进行测量,其测量结果与DJ-HZ-1型机床回转精度测量分析仪的测量结果基本吻合。     

机床主轴回转误差测试研究

以LabVIEW为平台,设计了主轴回转误差实验系统。该系统由位移测试单元、采样时钟单元、数据采集卡及通用计算机组成。用于主轴回转精度的实际测量,取得了良好效果。     

基于三点法的主轴回转精度实验分析

应用三点法的测量系统,对气浮主轴的回转精度进行测量。该测量系统主要由纳米级圆度的标准球、多通道双灵敏度电容位移传感器组成。通过搭建实验平台,建立误差分离模型,对三点法测量气浮主轴回转精度进行分析,利用误差分离算法对实验得到的数据进行处理,然后利用MATLAB对测得的原始数据进行仿真,得到气浮主轴在不同转速下的回转精度。分析出不同因素对回转误差影响的趋势并进行归纳,为气浮主轴回转精度的控制和在线监测提供了理论依据。     

Numerical study on the rotation of an elastic rod in a viscous fluid using an immersed boundary method

We present a three-dimensional computational model based on an immersed boundary (IB) method to study the hydrodynamic features of a solid flexible cylindrical rod in a viscous fluid driven at one side by a tiny motor. The elastic rod is modelled by a number of circular cross-sections with twelve IB points on each cross-section. Three types of elastic links are created from each IB point to obtain an elastic network model of the rod and the first cross-section is modelled as the motor part. The elastic forces are computed based on an elastic energy approach and the motor forces are obtained from the applied angular frequency of rotation of the motor. The Stokes equations governing the fluid are solved on a staggered Cartesian grid system using the fractional-step based finite-volume method. Numerical simulations are performed to demonstrate the three dynamical stages of rod motion-twirling, whirling and overwhirling for different rotational frequency of the motor. It is revealed that for low rotational frequencies, the rod undergoes stable rigid body motion known as twirling. For high rotational frequencies of the motor, it is observed that the rod initially undergoes whirling motion and attains an unstable helical shape. Further, it is noticed that a discontinuous shape transition occurs for the rod and it folds back on itself. This unstable motion is referred to as overwhirling. It is also found that there exists a critical value of angular frequency of rotation of the motor below which the rod is subjected to twirling motion and above which it undergoes overwhirling motion.     

高精度主轴回转精度的测试与研究

通过对锯齿形多槽式动静压气体润滑轴承［１］主轴回转精度的实验研究，采取一定的测试方法和分析手段，找出了产生回转误差的主要原因，提出了进一步提高回转精度的有效措施。     

HSK刀柄-主轴结合面接触特性及其影响分析

以HSK刀柄-主轴为研究对象,采用有限元方法对HSK-A63型刀柄-主轴结合面接触特性及主轴系统动态特性进行了仿真分析。分析结果表明：高转速条件下,转速对接触面积影响较大,接触面积随转速增大而减小。夹紧力对接触应力影响较大,在转速和过盈量一定时,接触应力随夹紧力增大而增大,且接触应力的分布情况会发生变化。刀柄-主轴结合面对主轴系统固有频率、振动幅值影响显著,考虑结合面影响后,主轴系统的固有频率降低,振动幅值增大。     

龙门数控机床主轴热误差及其改善措施

依据ISO和ASME标准建立龙门数控(Numerical control,NC)机床热误差测试条件,通过主轴恒转速和变转速热误差试验分析主轴箱温度场分布及其对主轴热误差的影响趋势。建立龙门机床误差元素模型,分析影响机床各坐标轴加工精度的主轴热误差分量。研究发现,主轴热误差和主轴箱温度存在单调对应关系,温度对主轴轴向的热伸长误差的影响要远大于主轴径向的热漂移误差,但温度变化相对各坐标变形存在热延迟和热惯性等特性。对主轴径向精度影响最大的热误差分量是由机床生热产生的同方向的偏移误差和与之垂直的偏转误差;对轴向精度影响最大的则是轴向的偏移误差。针对热误差特点和分布规律,提出结构优化、热平衡、误差补偿建模等3种减小热误差的措施,并对其各自优点进行了分析。     

Form error in diamond turning

The main feature of ultraprecision, single point diamond turning (SPDT) is its ability to produce high quality surface finishes on the order of nanometers while meeting tight form tolerances on the order of micrometers. This capability allows for the production of optical devices with minimum post-processing operations. The issue of form error is critical since it may severely compromise the performance of the designed optical system. Tool-workpiece relative vibration is a major cause of this error. In this article, the authors have demonstrated that imbalance of the spindle is a major cause of form error which eventually leads to a structured error called “spindle star” that appears as straight concentric spokes radiating out from the center of the part. The formation of a spindle star pattern can be explained using Campbell's rotordynamics analysis. This analysis explains how assisted air-hammering instability and cross-coupling effect of the air-bearing spindle can contribute to spindle star. This experimental approach used force and accelerometer data with the help of modal analysis to conclude that spindle star is a synchronous error and is a function of rotational frequency of the spindle and its harmonics. The integer harmonic from the Campbell's waterfall diagram predicts the number of spokes in the spindle star. It was also observed that the height of the spindle star undulations increases with higher rotational speed. It was also observed that cutting material and tool geometry has no influence on the spindle star formation; rather this is an inherent characteristic of air-bearing journals. Finally, the analysis was successfully validated by changing the natural frequency of the spindle by adding mass.     

Optical technique to measure five-degree-of-freedom error motions for a high-speed microspindle

We present an optical technique to measure five-degree-of-freedom error motions of a high-speed microspindle. The measurement system consists of a rod lens, a ball lens, four divided laser beams, and multiple divided photodiodes. When the spindle rotates with its concomitant rotation errors, the rod and ball lenses, which are mounted to the chuck of the spindle, are displaced, and this displacement is measured using an optical technique. For this study, we decide the design parameters of the optical system using ray tracing, fabricate a prototype of the measurement system, and evaluate it experimentally. The results show that the measurement system has a resolution of 5 nm and can be used to evaluate high-speed microspindle rotation errors.     

A speed-dependent variable preload system for high speed spindles

High speed machine tools are required to operate in a wide range of spindle rotational speeds with high stiffness and high accuracy. The stiffness of the spindle is largely dependent on the axial preload of the angular contact bearings. A large preload is required at lower range of speeds to provide sufficient stiffness for vibration-free heavy cutting. However, at higher speeds, it results in rapid temperature rise and reduces the life of the bearing. For optimum performance, it is essential that the bearing preload is reduced as the rotational speed increases. In this paper, an automatic variable preload system is proposed that changes the preload on the bearings as a function of rotational speed. This system is based on the use of centrifugal forces and requires little space inside the spindle. The performance of this mechanical system is determined using finite element modeling. A prototype of the system is fabricated and its performance is investigated using a specially devised test stand for direct measurement of the preload. The effectiveness of the proposed system in reducing the preload at higher speeds is demonstrated.     

Hydrostatic ionic liquid-lubricated fluid film bearing for a rotational electron-beam lithography system

Rotational electron-beam mastering (REBM) systems have been studied with the aim of achieving the high data density necessary to facilitate the fabrication of next-generation optical data media, such as holographic storage. This study reports the design and testing of an ionic liquid (IL)-lubricated hydrostatic spindle system comprising an IL bearing, IL supply pump, and ionic magnetic fluid seal; and its outgassing performance under high-vacuum conditions. An inner vacuum chamber pressure of approximately 10⁻⁴ Pa was maintained during rotation of the spindle system. The outgassed products, as measured by a quadrupole mass spectrometer, were primarily generated from the air components in the lubricant IL. The non-repeatable runout in the radial direction, which is an important parameter of REBM accuracy, was 100 nm for a rotational speed of less than 130 min⁻¹. The proposed method can be used for a 100-nm scale REBM device.     

主轴回转运动精度的计算机视觉测量系统

基于计算机视觉测量技术,建立了机床主轴回转运动精度测量系统。系统主要由CCD 摄像机、计算机和相应的图像处理软件组成。利用图像传感器记录靶标特征点运动轨迹,经过图像处理软件的数据处理,可直接测得主轴的回转运动。由于靶标特征点的提取直接影响系统的测量精度,因此提出了以圆形标记作为靶标图案,采用面积矩方法提取圆心来提高系统测量精度。在MATLAB 环境下编程实现图像处理和数据计算,采用最小区域圆法计算主轴回转误差。最后采用该系统对车床主轴进行了测量,试验证明,系统可以实现主轴回转运动精度的精确、快速测量,且精度达到微米级。     

超高速磨削机床主轴系统模态分析

针对液体动静压轴承支撑的超高速磨削主轴系统工作的特殊性,在机床工作过程中,主轴高速旋转,动静压轴承的支撑刚度随转速动态变化.为了解主轴系统工作过程中的动态特性,应用Flunent软件求解液体动静压轴承的动态支撑刚 度,而后在此基础上利用有限元分析软件ANSYS建立超高速磨床主轴系统的三维有限元模型,并对其进行模态分析,得到了各阶固有频率和振型.通过设置不同转速下轴承的支撑刚度,获得主轴系统模态分析结果,并利用图解法求解出主轴系统的临界转速.分析结果表明主轴系统在高速旋转状态下,系统的结构刚度会发生变化,使主轴系统的固有频率改变,并且随着转速提高差异越显著.通过振动试验测试验证仿真分析的可靠性,经分析可知,试验与仿真的误差主要来源于支撑模型的简化.