超精密车削加工中的圆度补偿

提高工件形状精度是开发超精密加工技术的主要目标。本文应用综合计算机、动态检测、信号处理、控制理论、微位移技术等手段，在国产SI—235超精密车床上进行切削试验，开发一种主轴回转运动误差补偿技术来提高金刚石刀具超精密车削工件的圆度精度，可达50％以上，圆度值＜0．0     

超精密车床运动系统结构分析

超精密车削在加工盘形零件及圆锥形零件领域发挥着重要作用,所加工零件的表面质量受超精密车床运动系统精度的直接影响。为了探索超精密车床运动系统的影响因素,分别对车床的主轴运动系统及导轨运动系统进行了结构分析和传动机理分析,讨论了主轴运动系统及导轨系统结构的不同结构设计对超精密车床控制系统的影响,为超精密车床运动的高精度控制提供了理论支撑。     

超高精度轴系的研制

随着宇航、计算机、微电子、智能系统和兵器等技术的飞跃发展,不少零件的精度超出了经典的几何精度的“精密”概念,如高于0.05微米的圆度和0.1角秒的分度误差等。这些零件的加工和检验,主轴回转精度起着极其重要的作用。因此,国内外很重视这方面的研究,而且取得很高的精度。如日本超精密车床主轴径向     

超精密数控立式车床

一种用于加工高精度菲涅尔透镜阴模和阳模的超精密数控立式车床———NJ K0 2 3超精密数控立式车床 ,近期在成都宁江机床集团试制成功。由于菲涅尔模板制造技术的高精度加工要求 ,目前世界上只有日本、德国、丹麦等少数国家生产。而宁江机床集团此次取得的技术成果填补了该机床国内生产的空白。该机床采用高精度气浮主轴 ,用花岗岩做主要基础件 ,真空吸盘夹持零件 ,采用低温冷风技术和真空吸尘排屑技术等多项国内外超精密高新加工技术 ,为背投彩电的屏幕制造提供了理想的加工设备。宁江集团研制成功的超精密数控立式车床获得了用户“中国…     

数控车床主轴热变形误差检测及改善措施

热变形误差是影响高速高精密数控机床加工精度的主要因素,对机床主轴热变形进行检测与研究显得至关重要。以CAK3665数控车床主轴为研究对象,运用传热学经典理论对主轴系统的热源分布以及传热方式进行了介绍,并通过FLIR红外热像仪测温技术和激光测距技术对主轴温升与车床热变形进行了测量与研究,测得主轴中速连续运转270min时达到稳定温升,温度对主轴轴向的热伸长误差的影响大于主轴径向的热变形误差。最后,根据测量结果提出减小主轴热变形的措施。研究工作为车床主轴的进一步改进设计和热变形补偿提供依据。     

主轴回转误差测量技术研究现状

主轴回转误差是超精密领域的一个重要参数,准确测量主轴回转误差,对控制主轴运动、提高加工精度而言具有重要意义.介绍了主轴回转误差测量技术的研究现状.现有的主轴回转误差测量技术可以分为探针法、光学法、刻痕法,对探针法中常用的反转法、多点法、多步法进行了原理论述与误差分析.     

超精密磨床主轴部件热特性的有限元分析

加工中机床热误差是影响机床加工精度稳定性的关键因素,对其进行准确的分析至关重要。文章运用ANSYS软件建立超精密磨床主轴部件的有限元模型,分析主轴热源及初始条件,边界条件,通过计算得到磨床主轴的温度场、热应力及热变形量。分析结果说明了热误差为超精密磨削的主要误差,为后期加工和试验分析提供了参考依据。     

车床主轴旋转精度测量系统设计

车床主轴的旋转精度是衡量车床加工性能的一个重要因素。一是车床的主轴旋转精度会很大地影响车床的加工精度;二是随着数控车床的普及,要求对机床的回转精度进行实时测量、实时误差补偿。研究车床主轴旋转精度的测量方法,设计非接触式测量系统来实现机床主轴旋转精度的动态测量,并根据所采集信号初步估计车床主轴的运动情况,具有一定的理论依据及实际应用意义。     

精密超精密主轴转台套类零件高精高效磨削工艺

套类零件是精密超精密主轴、转台关键共性零件之一,其精度是影响主轴和转台部件性能的重要因素。分析了精密超精密主轴、转台套类零件结构特征、技术特性、加工难点,以及基于卧式内、外圆磨削加工中所存在的问题;设计了基于立式磨削的加工工艺技术路线,实现最小工序转运及基准转换误差累积;对基于立式磨削工艺中工件装卡、前序质量控制、工艺参数选择与优化等关键问题进行了论述;基于立式磨削工艺技术路线,完成了大量典型高精度套类零件磨削,稳定实现了磨削圆度≤1μm、同轴度≤2μm和垂直度≤2μm磨削效果,精密超精密主轴、转台套类零件磨削精度及磨削效率得到有效提升。     

关于高精度车床主轴回转精度的测量

本文主要阐述了高精度车床主轴回转精度的几种测量方法。文中指出:对于超精加工机床、主轴回转精度的动态测试研究是直接提高另件加工精度的关键。介绍了国内外的动态测试的主要方法。文中还介绍了精密球加工机床主轴回转精度测量的方法。提出了采用试切另件后用电容测微仪对主轴径向与轴向进行近似测置的方法与理由。其测量结果和静态测量与加工另件精度基本相同。该方法适用于精加工及回转轴系具有良好的动平衡条件下的测量,测量装置简单易行,便于在生产现场使用.     

超精密光学磨床主轴的温度场分布及其优化设计

为了提高所设计的超精密光学磨床精度和提高温度场分析的准确性,利用有限元分析软件ANSYS和热力学理论,分析了超精密光学磨床主轴的温度场分布。首先,建立自由电子气模型,计算出自主设计的超精密光学磨床主轴材料的热导率;进而研究分析不同结构、不同环境下机床主轴的温升规律;最后,提出了基于热力学分析结果的一系列主轴结构优化方法,采取对主轴和点接触件进行优化设计,减小热源与主轴之间的接触面积等方法,减小机床主轴的热变形,从而提高超精密光学磨床的精度。     

超精气磁轴承主轴系统的结构设计与控制

利用主动磁轴承来提高气体轴承回转精度,实现主轴回转精度的提高.基于该理论,设计了超精气磁轴承主轴系统结构,对主轴系统进行了动力学建模,并对控制系统进行了分析.     

纳米精度在位测量系统测头误差校正方法

针对超精密机床两轴联动接触式在位测量过程中测头误差影响测量精度的问题,提出了一种测头半径误差及形状误差校正方法。进行了在位测量实验,比较分析了测头误差未校正、测头半径误差校正及测头形状误差校正三种情况的测量结果,并分别与Taylor Hobson PGI840离线测量结果进行对比,以验证测头形状误差校正方法的有效性。测头形状误差校正后,面形精度PV值由420nm变为370nm,与离线测量PV值380nm的差值为10nm。结果表明,该在位测量系统测头误差校正方法有效,能够提高在位测量精度。     

Dynamic modeling for thermal error in motorized spindles

This paper proposes a new modeling methodology to predict thermal error in motorized spindles. The dynamic model predicts thermal errors that are caused by deformation in the motorized spindle structure due to heat flow from internal sources. These thermally induced errors become more serious and dominate the total error when it comes to high speed and high precision. If these thermal errors can be predicted, they can be compensated in real time. In this paper, a new thermal errors model (ARX model) is presented which capitalizes on the notion that the motorized spindle thermoelastic system has very complicated dynamics. Furthermore, the selection principle of temperature key points, which are indispensable for building a robust thermal error model, is provided using the thermal error sensitivity technology. At last, an experiment on the thermal error in a motorized spindle is conducted to verify the effectiveness of the ARX model, the experimental results show that above 80 % of axial thermal errors are predicted for a variety of motorized spindle cycles and the dynamic model has good accuracy and robustness.     

XH718加工中心的热误差补偿研究

在分析某XH718加工中心主轴及主轴箱结构和热源的基础上,在主轴箱上初步选择多个测温点,根据测温点温度和主轴热误差的数据,应用模糊聚类分析和相关性分析对测温点进行了优化,确定最小数量的关键测温点。然后应用多元线性回归理论建立了关键测温点的温升和热误差的数学模型。数学模型在加工中心上补偿后的数据表明,可以在很大程度上改进加工中心的精度,达到了客户需要的精度要求。     

精密数控机床制造中的误差补偿法

通过对轴系回转精度的误差抵消，大导轨精度的综合修正刮研及坐标定位精度的综合修正，说明系统误差综合补偿法是精密数控机床制造中一个重要应用方向。     

基于粒子群算法的滚削齿面综合轮廓误差预测模型与试验研究

在配备有自主研发的数控滚齿系统的精密卧式滚齿机上,运用三因素两水平响应曲面法设计滚削试验,研究齿轮滚削加工刀具转速、轴向进给速度、背吃刀量对齿轮齿面轮廓误差的影响规律。根据试验结果,分析得出齿轮齿廓总偏差、齿轮螺旋线总偏差、齿距累计总偏差的预测模型及各工艺影响因素对齿面轮廓误差的作用显著程度,并以三个预测模型的附加权重值之和达到最小值为目标,建立可以评定多目标误差的齿面综合轮廓误差数学模型,运用粒子群优化算法对齿面综合轮廓误差数学模型进行分析优化,寻找最佳滚齿加工工艺参数。试验表明,采用粒子群优化算法对响应曲面法建立的齿面综合轮廓误差数学模型进行优化可以作为滚削加工前的工艺参数选取方案。     

Self-calibration and compensation of setting errors for surface profile measurement of a microstructured roll workpiece

Microstructured roll workpieces have been widely used as functional components in the precision industries. Current researches on quality control have focused on surface profile measurement of microstructured roll workpieces, and types of measurement systems and measurement methods have been developed. However, low measurement efficiency and low measurement accuracy caused by setting errors are the common disadvantages for surface profile measurement of microstructured roll workpieces. In order to shorten the measurement time and enhance the measurement accuracy, a method for self-calibration and compensation of setting errors is proposed for surface profile measurement of microstructured roll workpieces. A measurement system is constructed for the measurement, in which a precision spindle is employed to rotate the roll workpiece and an air-bearing displacement sensor with a micro-stylus probe is employed to scan the microstructured surface of the roll workpiece. The resolution of the displacement sensor is 0.14 nm and that of the rotary encoder of the spindle was 0.15r~. Geometrical and mathematical models are established for analyzing the influences of the setting errors of the roll workpiece and the displacement sensor with respect to the axis of the spindle, including the eccentric error of the roll workpiece, the offset error of the sensor axis and the zero point error of the sensor output. Measurement experiments are carded out on a roll workpiece on which periodic microstructures are a period of 133 i~m along the circumferential direction. Experimental results demonstrate the feasibility of the self-compensation method. The proposed method can be used to detect and compensate the setting errors without using any additional accurate artifact.     

Thermal influence of the Couette flow in a hydrostatic spindle on the machining precision

Hydrostatic spindles are increasingly used in precision machine tools. Thermal error is the key factor affecting the machining accuracy of the spindle, and research has focused on spindle thermal errors through examination of the influence of the temperature distribution, thermal deformation and spindle mode. However, seldom has any research investigated the thermal effects of the associated Couette flow. To study the heat transfer mechanism in spindle systems, the criterion of the heat transfer direction according to the temperature distribution of the Couette flow at different temperatures is deduced. The method is able to deal accurately with the significant phenomena occurring at every place where thermal energy flowed in such a spindle system. The variation of the motion error induced by thermal effects on a machine work-table during machining is predicated by establishing the thermo-mechanical error model of the hydrostatic spindle for a high precision machine tool. The flow state and thermal behavior of a hydrostatic spindle is analyzed with the evaluated heat power and the coefficients of the convective heat transfer over outer surface of the spindle are calculated, and the thermal influence on the oil film stiffness is evaluated. Thermal drift of the spindle nose is measured with an inductance micrometer, the thermal deformation data 1.35 μm after running for 4 h is consistent with the value predicted by the finite element analysis's simulated result 1.28 μm, and this demonstrates that the simulation method is feasible. The thermal effects on the processing accuracy from the flow characteristics of the fluid inside the spindle are analyzed for the first time.     

Spindle thermal drift measurement using the laser ball bar

Thermally induced errors are major contributors to the overall accuracy of machine tools. An important component of thermally induced errors is the error associated with spindle thermal drifts. In this paper, a novel method is developed to measure spindle thermal drifts in machine tools using a laser ball bar (LBB) as the calibration instrument. The method is implemented on a two-axis CNC turning center. The LBB is used to measure the coordinates of the spindle center and the direction cosines of the spindle axis at various thermal states. The axial, radial, and tilt thermal drifts of the spindle are then computed from the changes in these coordinates. The new method is verified by comparing the spindle drifts measured with the LBB to those measured by capacitance gauges. The results obtained by the new method show good agreement with the capacitance gauge technique. The primary advantage of the new method is the ability to measure the spatial coordinates of the spindle center and direction cosines of the spindle axis with the same instrument used for measurement of the geometric errors of the machine axes.