Factors affecting component measurement on coordinate measuring machines

It can often be difficult to find a complete relationship between the specified performance of a coordinate measuring machine (cmm) (see Fig 1) and actual results obtained, because of unexplained differences between them. This report explain one method of identifying these differences and discusses some sources of error which may give rise to them.     

Achievement of accuracy by error compensation of large CMMs

In this paper we will discuss the limit of the possible compensation for the systematic geometrical errors in large coordinate measurement machines (CMMs). One of the main problems is that the methods of measuring the errors produce errors themselves, which statistically add up to a total uncertainty of the compensation. The standard methods of error compensation cannot improve the measuring uncertainty of the machine beyond this limit, and this limit can only be reached if the reproducibility of the machine (ie the statistical error) is improved.     

A two-dimensional test body for calibration of coordinate measuring machines

A two-dimensional test body having cross-aligned hollow cones has been developed for automatic calibration of coordinate measuring machines (CMMs). Two hours are sufficient for the measurement of translatory and rectangularity errors of a CMM by means of the test body. In this paper the principles of measurement of such erros using the test body are described These principles can be utilized on the assumption that one knows the exact values of the test body, so the calibration procedures for the test body are also described.     

基于遗传算法的测量仿真系统路径优化问题研究

分析了三坐标测量机和测量仿真系统的工作原理,阐述了一套基于CATIA V5平台的测量仿真系统的功能和工作流程,在Matlab平台上根据测量点数据和测量机的功能特性建立了数学模型,并利用遗传算法对测量点路径进行优化计算。最后,通过实验验证了路径优化系统的可行性,分析了遗传算法的优化效果。     

基于三坐标测量机的盘形凸轮廓线测量

介绍了盘形凸轮廓线的形成,利用三坐标测量机对盘形凸轮廓线进行测量,讨论了测量原理、方法、数据输出以及对CMM测头直径的补偿。     

A comparison of different algorithms for circularity evaluation

The measurement and evaluation of circularity of cylindrical components is very important for the majority of cylindrical workpieces used in precision engineering. Further, since the measurement and evaluation of cylindricity is more complex and time consuming, only circularity is evaluated for most applications.The evaluation of circularity from a circularity graph and/or from digital data requires a suitable algorithm. The most commonly used criterion for this has been the least squares criterion, though it is known that this does not necessarily give the best solution. Hence, an attempt has been made in this paper to propose different algorithms and compare them. The algorithms considered are based on the methods of least squares, intuition, general second-degree equation for a circle, best-fit ellipse and simplex search. A comparison of these methods is presented.     

分段产生共轭齿廓方法研究

提出了一种分段产生共轭齿廓的方法,此方法是用三次曲线函数来描述刀具方程,然后根据啮合方程求出共轭的齿廓方程.与传统方法不一样的是,它是分段产生共轭齿廓的,是一种离散的方法,此方法的前提是要求出刀具上的一系列点,通过这些点的坐标来确定三次曲线函数.刀具上点的获得有两种方法:一是从刀具方程中直接获得,二是用坐标测量机械来测出刀具上的点.此方法还可以用于检验刀具使用一段时间后所产生的齿廓,通过与原始加工齿廓的比较来判断刀具的磨损程度.     

Problems with software for running coordinate measuring machines: The use of virtual volumetric standards

The validation of software for coordinate measuring machines is increasinly being seen to be as important as the assessment of the machine construction and its coordinate system. Virtual volumetric standards are the coordinates of points on the surface of an imaginary workpiece which can be used to evaluate cmm software. This paper gives some examples of virtual volumetric standards and their use.     

工件圆度误差测量不确定度评定

为了实现工件圆度误差的不确定度评定,对基于三坐标测量机的工件圆度轮廓数据的采样策略、圆度评定方法及不确定度评定方法进行研究。首先,根据工件圆度轮廓特征进行实验测量,获取不同工件的多个样本。接着,基于最小二乘法和微分进化优化算法对样本的圆度误差进行了误差评定。然后,在分析比较误差大小的基础上,说明了采用的采样策略和微分进化评定算法。最后,基于圆度误差评定结果运用了测量不确定度表示指南(GUM)和蒙特卡洛方法(MCM)进行不确定度评定。实验结果表明:微分进化算法与最小二乘法相比均值差最大达到1.1μm, MCM方法比GUM方法得到的标准不确定度均值小0.02μm。合理的采样点数、微分进化算法及MCM不确定度评定方法可以得到更稳定可靠、精度高的评定结果。     

无图纸检测中的CAD/CMM软件接口技术

在简要介绍了无图纸检测技术中CAD/CMM系统集成的必要性之后,提出了一种基于IGES文件的三维零件模型转换的新方法,该方法能够对待测零件的CAD数据自动进行提取和识别,并能在CMM系统中重构零件模型.文中给出了其实现的基本原理和算法,最后通过实验加以验证.     

Optimizing a servo system for a coordinate measuring machine

Time saving is the primary justification for a CMM. The data acquisition activity (probing), in general, occupies over 95% of the real cycle time, and is dictated by the characteristics of the machine and its servo control system. Considering all the requirements, a control system based on a microprocessor was chosen. The microprocessor can be programmed to suit the system requirements in a way which cannot be achieved in pure hardware systems. The control program can even be edited in real time by passing relevant parameters from the supervising computer, if required.     

Circular test for three-coordinate measuring machines and machine tools

Today, two principles are used in testing the accuracy of three-coordinate measuring machines and machine tools: measurement of the machine components, and measurement (or production) of master-pieces. Both methods are in themselves insufficient to fulfil the users' demands but combining the two should lead to better results. In the circular test a standard disc is used. The disc is measured in different positions in the working area of the machine. The calculated mean square fit diameters, standard deviations and Fourier analysis result in an analysis of the error sources and of the geometric error components     

三坐标测量机动态误差与测球半径补偿误差的研究

分析了影响给定的三坐标测量机动态误差的因素,对动态偏转角误差进行了测量,并推导出由动态偏转误差得到测头处的动态位移误差的方法,同时分析了测球半径补偿误差的成因及解决措施。     

A simple method for testing measuring machines and machine tools. Part 2: Construction details

Part 1 of this article, which appeared in the previous issue of this journal, detailed the principles and applications of magnetic ball bars. These can give rapid, precise indications of the two or three dimensional accuracy of a machine. Here, construction details are presented     

Experience with a computerized numerical control coordinate measuring machine

Experience gained with a coordinate measuring machine at the author's company is described. The programming and operation of an LK Granite 80 are explained and a typical machine program and printout of inspection results are given.     

基于三坐标测量机的齿轮参数测量方法研究

结合三坐标测量机对渐开线圆柱齿轮参数的测量进行了研究并提出了测量方法.通过曲线检查法对异常测点的处理,构造一种新的迭代公式,实现对基圆半径的更精确求解,并在此基础上测出齿轮的其他参数.采用VC++开发了一套齿轮测量软件,实现了对渐开线圆柱齿轮的参数进行快速准确的测量,并且适用于破损的不完整齿轮.     

基于Voronoi图的快速成型扫描路径生成算法研究

提出一种平面多连通区域的算法 ,该算法对波前传播算法进行了扩展 ,能适用于平面多连通区域。用 VC++实现了平面多连通区域的 Voronoi图算法 ,并应用于立体光固化法快速成型中的扫描路径规划