通用车偏心夹具

如图所示的通用车偏心夹具通过其夹具体4安装在车床主轴上,用于加工偏心表面。夹具体的右端装入套筒3内,相对于机床主轴轴线的偏心距为5mm。卡盘1的轴线相对于套筒的回转轴心也偏移5mm。当相对于夹具体回转带有卡盘的套筒时,卡盘轴线相对于主轴轴线的偏移量可达10mm。因而,即使卡盘与套筒的回转角度很大,偏心量却改变不大,这能避免产     

新式万能偏心夹具

<正> 这种夹具是用来加工偏心表面的。夹具壳体4的一头装在车床的主轴里,壳体的另一头装在与机床主轴成5毫米偏心距的套筒3里。偏心套上紧固着用于夹持被加工零件的自定心卡盘1。这样一来,卡盘的轴线就相对于套筒的旋转轴线偏移了5毫米。装有卡盘的套筒3相对于夹具壳体旋转起来之后,卡盘的轴线相对于机床主轴的偏心值可达10毫米。即使卡盘相对于套筒有很大的角位移,这对偏心值的影响也不是很大的。从而也就避免了夹具在调整中所产生的很大调整误差。可以用各种方法解     

精密离心机结构安装误差对主轴回转精度的影响

针对精密离心机的精度控制,建立了精密离心机结构安装误差对静压气体轴承主轴回转精度影响的定量计算模型,运用该模型开展了多方面结构安装误差参量对主轴回转精度影响规律的研究。研究表明主轴回转误差随转盘与静压气体轴承轴线间偏心量、静压气体轴承轴线铅垂度安装误差和转盘与静压气体轴承轴线安装垂直度误差的增加而增大,其中偏心量和垂直度误差对主轴回转误差的影响较大,铅垂度误差对主轴回转误差的影响较小。研究可为精密离心机的设计提供帮助。     

主轴顶尖偏心调整机构在数控滚齿机上的应用

数控滚齿机床上误差总是不可避免地存在,特别是数控机床主轴的回转误差更是由多种因素引起的,它的存在将直接影响被加工对象或被测量对象的精度.为此,将自由调节回转偏心的顶尖应用于数控滚齿机上,即使其主轴存在偏心,通过调整此机构,也可使顶尖轴线和回转轴线的回转偏心接近于零.     

自定心卡盘装夹偏心轴数控车削

1.加工偏心轴的装夹方法加工偏心轴的方法,应按工件的加工数量、形状和精度要求,采用不同的装夹方法。但最终应保证所要加工的偏心部分轴线和车床主轴旋转轴线重合。在此讨论最常用的自定心卡盘装夹偏心轴及其数控加工。     

车削偏心工件

在机械传动中,回转运动变为往复直线运动或直线运动变为回转运动,一般都是用偏心轴或曲轴(曲轴是形状比较复杂的偏心轴)来完成。 偏心轴即工件的外圆和外圆之间的轴线平行而不相重合。偏心套即工件的外圆和内孔的轴线平行而不相重合,这两条轴线之间的距离称为“偏心距”。 车削偏心的方法,应按工件的不同数量、形状和精度要求相应地采用不同的装夹方法,但最终应保证所要加工的偏心部分轴线与车床主轴旋转轴线重合。     

车工校正编心误差分析

车工经常会碰到车削偏心工件。在车削前偏心是否能准确校正,将直接影响到工件的加工质量。笔者从事车工技能培训二十多年,现借贵刊一角,对校正偏心时容易出现的误差作一番分析。 1.用百分表校正偏心的误差分析 (1)常用校正方法 将百分表测杆的轴线垂直并过车床主轴轴线安装,表的触头和工件外圆接触,     

大偏心轴及角度偏心轴的简易加工

在没有专用加工设备的情况下,偏心轴一般是在车床上加工的。其加工原理基本相同,即把需要加工偏心部分的轴线校正到与车床主轴旋转轴线相重合的位置。 1.大偏心轴的简易加工 当遇到偏心距大、长度长、批量大的偏心轴加工时(如图1所示零件),在卧式车床上用常规加工方法:备长度为265mm、(?)180mm的圆钢,→加工两端面至长259mm→划线找出两轴心线位置     

车削偏心工件的通用夹具

在产品加工过程中,经常遇到偏心工件。因受本厂设备限制,只能在普通车床上进行加工。以前,我们对每种类型的偏心工件都设计了专用夹具,由于品种多,因此换工装频繁、效率低,浪费了大量时间和资金。 [1]偏心类工件的分析 　　通过对偏心工件的分析和研究,找出了偏心类工件加工的共同点。 　　①偏心工件的外圆与外圆、外圆与内孔之间的轴线平行而不重合,两轴线间的距离即为偏心距。 　　②偏心工件在车床上加工时,都必须使所需加工的偏心部分的轴线或中心线与车床主轴旋转中心重合。 由于以上两特点,我们设计了这套可调通用夹具。…     

偏心轴的一种装配加工方法

通过对加工图的分析,认为偏心轴加工的关键在于加工偏心孔并保证其轴线与主轴保持平行,从保证品质及节省成本的角度出发,根据现有的加工条件和实际加工过程,探索并提出了一个简单可行、高效经济的加工思路。     

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。     

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.     

The building of spindle thermal displacement model of high speed machine center

This article mainly analyzes the issues of spindle thermal displacement upon the acceleration of spindle, and proposes a complex multivariable regression analytical method to build a spindle thermal displacement model, so as to predict the thermal displacement of spindle caused by the heat under every time slot during the practical high speed machining process. Upon using the compensation of spindle displacement model, the largest value of cutting depth of the hole error of 62 μm that is caused by the spindle thermal displacement not being compensated can be reduced to a maximum cutting depth of the hole of 4.62 μm, and its average error value of cutting depth is 1.58 μm. Therefore, upon compensating the spindle thermal displacement model proposed in this study, the machining precision can effectively be improved.     

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。     

Thermal error of a hydrostatic spindle

This paper proposes a thermo-mechanical error model of a hydrostatic spindle for a high precision machine tool. By predicting the variation of motion error induced by thermal effects on a machine worktable during machining, this model allows deeper insights into the underlying mechanisms that result in evolutions of the spindle accuracy. The heat power generated in the spindle elements and the coefficients of convection heat transfer over its outer surface have been evaluated. Then, the distribution of temperature and deformation of the spindle have been simulated by a finite element coupled thermo-elastic model, from which the influence on notably spindle stiffness variation was deduced. Experimental measurement of the thrust plate axial displacement under thermal expansion is in close agreement with the computed axial thermal expansion.     

Modeling, measurement, and evaluation of spindle radial errors in a miniaturized machine tool

Miniaturized machine tools have been established as a promising technology for machining the miniature components in wider range of materials. Spindle of a miniaturized machine tool needs to provide extremely high rotational speed, while maintaining the accuracy. In this work, a capacitive sensor-based measurement technique is followed for assessing radial errors of a miniaturized machine tool spindle. Accuracy of spindle error measurement is affected by inherent error sources such as sensor offset, thermal drift of spindle, centering error, and form error of the target surface installed in the spindle. In the present work, a model-based curve-fitting method is proposed for accurate interpretation and analysis of spindle error measurement data in time domain. Experimental results of the proposed method are presented and compared with the commonly followed discrete Fourier transform-based frequency domain-filtering method. Proposed method provides higher resolution for the estimation of fundamental frequency of spindle error data. Synchronous and asynchronous radial error values are evaluated in accordance with ANSI/ASME B89.3.4M [9] standard at various spindle speeds and number of spindle revolutions. It is found that the spindle speed and number of spindle revolutions does not have much influence on synchronous radial error of the spindle. On the other hand, asynchronous radial error motion exhibits a significant speed-dependant behavior with respect to the number of spindle revolutions.     

五点法测量机床主轴轴向及倾角的运动误差

提出了测量机床主轴的轴向及倾角运动误差的端面五点法。在轴端面绕轴心的某一圆周上,垂直于轴端面,按通过误差分析优化确定的位置,布置五个测头,在主轴回转一圈中同时测得主轴的轴向及倾角运动误差以及端面基准的形状误差,并将测头的读数及定位误差的影响降至最低程度。本方法可用于机床主轴回转精度的实时测量,试验表明其测量精度可达亚微米级。     

Orthogonal polynomials-based thermally induced spindle and geometric error modeling and compensation

The spindle error and geometric error are the main sources of inaccuracy in CNC machining. With the rising of the machine tool parts' temperature, the spindle error and geometric error increase continually, and the error curves have a nonlinear distribution. To analyze the thermal effects on spindle error and geometric error, an experiment is carried out. To improve the machining accuracy of a CNC machine, an error model is proposed based on orthogonal polynomials. With the application of the orthogonal polynomials, the polynomial regression can be transformed into multiple linear regressions which are easier to calculate. In order to implement the real-time error compensation for the thermally induced spindle error and geometric error, an error compensation method is proposed based on the external coordinate offset. The thermally induced spindle and geometric error are compensated by 90 % compared with no compensation.     

An identification method for spindle rotation error of a diamond turning machine based on the wavelet transform

This paper presents an identification method for the spindle rotation error from the flatness error in the workpiece surface. The spindle rotation error is identified by the wavelet transform, Weierstrass function, and power spectral density (PSD). The flatness error comprises various errors of the machine tool, such as spindle rotation error, guideway error, motor error, and ball screw error, therefore, wavelet transform is used to process the measured result of the workpiece and the signal is decomposed into high-frequency and low-frequency signal. Weierstrass function is used to fit the spindle rotation error. According to the PSD analysis of the processed signal in the frequency domain, the spindle rotation error is identified from the measured flatness error, this method provides a basis for the identification of machine tool errors.     

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。