适合现场使用的准步距规

数控机床在机械行业中应用日益普及。检测数控机床精度是数控机床验收与使用中的重要内容。数控机床位置精度 (重复定位精度、定位精度及轴线的反向差值 )是数控机床精度的核心。国家技术监督局在 1990年 1月 1日正式颁布了数控机床位置的评定标准———ＧＢ10 931— 89《数字控制机床位置精度的评定方法》(以后简称为《评定方法》) ,标准对位置精度的名词、术语、计算公式及检测方法作了明确的规定。但对检测位置精度所用的仪器并没有硬性的限定。目前检测位置精度的仪器有 :激光干涉仪、精密线纹尺与读数显微镜、基准步距规与杠杆千分表 (…     

数控机床位置精度中反向偏差指标合理性的探讨

关于数控机床位置精度的评定方法经国内外十几年的探索,现已基本完善。国际标准化组织于1988年正式颁发了“ISO 230-2:1988数控机床位置精度的评定”的国际标准。我国也于去年批准了“数字控制机床位置精度的评定方法”的国家标准(GB10931-89)。虽然这两个标准的制订说明了人们对数控机床位置精度的认识达到了一个新的水平,但是在实际工作中我们却发现,对反向偏差的确定还需进一步探讨,故提出些不同看法供大家商讨。 ISO和GB标准中对位置精度的评定提出了三项考核指标,即:定位精度、重复定位精度和反向偏差。关于前两项已在《机床》90年…     

基于数控机床空间误差提高其加工精度的补偿方法研究

基于数控机床各运动部件几何关系的综合分析,应用数控补偿技术,对机床整体空间误差进行补偿,提高了各轴移动定位精度、重复定位精度和几何精度,进而提高了数控机床加工精度。     

浅析数控机床线性坐标轴的全闭环控制

随着现代制造业的迅速发展,数控机床越来越多地被广泛应用,同时对数控机床定位精度、重复定位精度也日益提高,原来精密滚珠丝杠加编码器式的半闭环控制系统已无法满足用户的需求。半闭环控制系统无法控制机床传动机构所产生的传动误差、高速运转时传动机构所产生热变形误差以及加工过程中因传动系统磨损而产生的误差,而这些误差已经严重影响到数控机床的加工精度及其稳定性。线性光栅尺对数控机床各线性坐标轴进行全闭环控制,消除上述误差,提高机床的定位精度、重复定位精度以及精度可靠性,作为提高数控机床位置精度的关键部件日益受到用户…     

数控机床定位精度的检测与评定方法分析

分析了数控机床定位精度的刻线基准尺、读数显微镜检测和双频激光干涉仪检测方法.针对定位精度的评定项目,利用适合的评定方法和实测数据,得到各测点的定位误差和重复定位误差,分析出定位精度评定结果.     

数控机床的定位精度及重复定位精度初探

通过对影响定位精度及重复定位精度几个因素的分析及试验,简单地阐述了几种有效提高机床数控精度的措施及方法,旨在提高国产数控机床的数控精度。     

数控机床的高精度线性测量

作为天津市技术监督局计量认证及审查认可，并获得了天津市技术监督局颁发的产品监督检验站授权证书的质量监督部门．我站主要负责各类机床及附件等六大类产品的检验工作。其中．数控机床作为机床类的主导产品．其线性运动的定位精度和重复定位精度是机床精度检验中的关键项。     

订购数控机床须注意精度验收标准

订购数控机床须注意精度验收标准陈功福在选购数控机床时，往往要涉及到机床的位置精度，特别是各轴的定位精度和重复定位精度。由于各生产厂家对这两项精度指标的检测标准不一样，造成用户在购置机床时遇到一些问题。我单位在这方面不乏有一些经验和教训，介绍给大家，供...     

数控机床定位精度的综合分析

数控机床的定位精度是衡量数控机床性能的一个重要指标,影响机床定位精度的主要因素有机床导轨,反向间隙,温度等,着重分析了机床导轨直线度对于定位精度的影响,简述了使用双频激光干涉仪对导轨直线度进行测量的方法和校准原理,并给出了几种有效提高数控机床定位精度的方法.     

如何提高数控机床的精度

随着我国经济的飞速发展，数控机床作为新一代工作母机，在机械制造中已得到广泛的应用，精密加工技术的迅速发展和零件加工精度的不断提高，对数控机床的精度也提出了更高的要求。尽管用户在选购数控机床时，都十分看重机床的位置精度，特别是各轴的定位精度和重复定位精度。但是这些使用中的数控机床精度到底如何呢？     

提高机床重复定位精度的新机构

介绍了一种提高机床重复定位精神的新机构及其工作原理。     

An improved method for thermally induced positioning errors measurement,modeling, and compensation

In order to accurately identify the thermally induced positioning errors, an improved measurement method is proposed based on the repeatability of a machine tool’s temperature rise process. Using this improved measurement method, the mismatches between the thermally induced positioning errors and the machine temperatures can effectively be avoided. To improve the modeling accuracy and efficiency, the least-square fitting of orthogonal polynomial method is used in this research. Using this error modeling method, the thermally induced positioning errors are fitted by 96.7 %. To realize the thermally induced positioning error compensation, a new error compensation method is proposed based on the network. Experimental results show that the thermally induced positioning errors are compensated by 92.6 % compared with no compensation.     

New method of testing of the repeatability of CMM articulating heads

A new method of testing of the accuracy of coordinate measuring machine (CMM) articulating heads was developed and verified. This procedure consists of the measurement of a test sphere, and requires only a basic configuration of the coordinate measuring machine. A new parameter describing the repeatability of angular positioning by CMM articulating probing system was defined.     

基于直驱电机的旋转轴精度检测系统的研究与实现

传统的数控机床旋转轴运动精度检验方法存在精度低、检验重复性差等缺点,而先进的激光干涉仪也存在调整困难、成本偏高的不足.因此对数控机床旋转轴精度的检测进行研究,采用一种可实现高精度位置控制的直接驱动电机和PMAC运动控制卡为关键部件,组成对数控机床旋转轴定位精度检测的测量系统,实现了对混联车铣复合机床旋转轴运动精度的检测,分析了该测量系统的结构和测量原理以及测量误差源的产生,并提出了进一步改进的措施.     

超长数控丝杠磨床精度检测及其不确定度分析

介绍了用激光干涉仪检测超长数控丝杠磨床定位精度、重复定位精度的方法,并通过建立数学模型对这种测量方法的不确定度进行了分析。     

Stiffness effects on repeatability of positioning of linear axes

This paper studies the effect of stiffness (including slider stiffness and bearing stiffness) on the repeatability of the positioning of linear axes. First, a mathematical model between stiffness and the repeatability of the positioning of linear axes is established. The effects of the stiffness of the slider and bearing on the repeatability of positioning are analysed. The theoretical results show that the repeatability of the positioning decreases as the slider component stiffness and bearing stiffness increases. Second, a finite element analysis is implemented to calculate the effect of slider stiffness on the repeatability of positioning, the simulation results are found to be consistent with the theoretical results. Finally, the effect of bearing stiffness on the repeatability of positioning is experimentally investigated. The experimental and theoretical analysis results have been observed to coincide. Thus, the accuracy of the theoretical analysis is verified by both simulation and experimental results. The derived results afford designers and engineers a scientific basis for the stiffness design theory.

     

A non-contact method for detecting on-line industrial robot position errors using a microwave doppler radar motion detector

To be useful, industrial robots must meet positioning accuracy requirements for their given applications. Off-line calibration generally improves robot positioning accuracy to levels needed for open-loop use in most industrial applications. Applications that require greater accuracy with respect to external assemblies generally turn to closed-loop control or passive compliance. However, industrial robot systems do not generally monitor in-process robot position to detect machine faults that can lead to product faults, scrap, machine damage, and additional costs. To achieve greater operational efficiencies, new non-invasive, noncontact methods for monitoring robot position are needed. The investigators developed a low-cost method for in-process industrial robot position monitoring using a Doppler motion detector and a statistical position error measure. The method detects position errors at robot repeatability levels.     

A non-contact method for detecting on-line industrial robot position errors using a microwave Doppler radar motion detector

To be useful, industrial robots must meet positioning accuracy requirements for their given applications. Off-line calibration generally improves robot positioning accuracy to levels needed for open-loop use in most industrial applications. Applications that require greater accuracy with respect to external assemblies generally turn to closed-loop control or passive compliance. However, industrial robot systems do not generally monitor in-process robot position to detect machine faults that can lead to product faults, scrap, machine damage, and additional costs. To achieve greater operational efficiencies, new non-invasive, non-contact methods for monitoring robot position are needed. The investigators developed a low-cost method for in-process industrial robot position monitoring using a Doppler motion detector and a statistical position error measure. The method detects position errors at robot repeatability levels.     

Kinematic modeling and parameter identification of a new circumferential drilling machine for aircraft assembly

Automated fastener hole drilling is a key technology for low-cost and high-quality assembly of aircrafts. In this paper, a new circumferential drilling machine for fuselage assembly of large aircrafts is introduced. In order to meet the required position accuracy of drilled holes, this paper focuses on the kinematic calibration of the machine in order to improve its positioning accuracy. A modeling strategy, which combines the Denavit-Hartenberg (D-H) method and a modified version of the Hayati-Mirmirani (H-M) method, is proposed to deal with the special kinematic structure of the arc-base drilling unit of the machine. Main issues in kinematic parameter identification such as definition of objective function, calibration data selection, acquisition of initial values, and setting of convergence criteria are also discussed. Experiments of repeatability testing and kinematic calibration have been performed, and the results show that the positioning accuracy of the arc-base drilling unit is comparable to its repeatability after calibration. This suggests that the proposed kinematic calibration method is effective. Actual drilling tests have been performed on a simulated aircraft fuselage after implementing the identified kinematic model in the machine’s control software. Position errors of drilled holes are within ±0.5 mm, which meets the requirement for fastener hole drilling in the fuselage assembly of large aircrafts.