COORDINATE MEASURING MACHINE PROBING ACCESSIBILITY

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Improvement of coordinate measuring machine probing accessibility

In this paper, the probe accessibility of coordinate measuring machines (CMM) in dimensional inspection is studied. Based on the previous methods of the accessibility map, the influence of the actual configuration of the probe on the accessibility is analyzed in detail. A method, which takes the effects of the probe length and volume into account, is proposed so that the shortcomings of abstracting the probe as an infinite half-line could be overcome completely. Finally, a feasible and efficient algorithm is given.     

CMM touch trigger probes testing using a reference axis

A new method of testing of touch trigger probes for coordinate measuring machines (CMM) has been proposed. The concept is based on measurements of the distance between reference and triggering points in various directions. The reference points are established by the rotation axis of a precise rotary table. The advantage of this method relies on easy realisation with application of a commercial device for roundness error measurement. The accuracy of the presented method is much higher in comparison with the existing procedures of CMM probes calibration.The mathematical principle of the method has been presented and used for evaluation of its uncertainty. The validity of the method was experimentally confirmed by means of one- and two-stage type probes.     

Influence of measured objects parameters on CMM touch trigger probe accuracy of probing

Influence of the measured objects parameters on coordinate measuring machine (CMM) touch trigger probe inaccuracy of probing is investigated. Factors such as material stiffness of measured workpiece, its surface shape and roughness are taken into consideration. The measuring method out off CMM, based on a rotary table and a reference axis is applied for tests. The concept is based on measurements of the distance between reference and triggering points in various directions. The reference points are established by the rotation of a precise rotary table. The statistical analysis of variance and regression is applied for data analysis.     

Design and analysis of experiments in CMM measurement uncertainty study

In applying a coordinate measuring machine to measure a mechanical object, many factors affect the measurement uncertainty. Although a number of studies have been reported in evaluating measurement uncertainty, few have applied the factorial design of experiments (DOE) to examine the measurement uncertainty, as defined in the ISO Guide to the Expression of Uncertainty in Measurement (GUM). This research applies the DOE approach to investigate the impact of the factors and their interactions on the uncertainty while following the fundamental rules of the GUM. The measurement uncertainty of the location of a hole measured by a coordinate measuring machine is used to demonstrate our methodology.     

Simple master artefact for CMM dynamic error identification

The proposition in this paper is a new method applying a simple master artefact for testing the dynamic performance of coordinate measuring machines (CMM). The principle of the method is presented and the method is used for identification and evaluation of dynamic error sources. The validity of the method is experimentally confirmed on a Zeiss ACCURA bridge coordinate measuring machine equipped with a Vast Gold active scanning probe, as well as Vast XXT passive scanning probe.     

Reduced configuration set for the multi-step method applied to machine and probe error separation on a CMM

This paper presents a refinement and further analysis of an application of the multi-step method for the separation of machine and probe errors on a CMM using multiple redundancy probing of the machine’s own master ball. The objective is to reduce the amount of data required and so minimize the test time in order to reduce the industrial cost of such periodic verifications.     

未知自由曲面三坐标测量新方法

三坐标测量机(CMM)通常难于实现对未知自由曲面的自动测量,首先需要人工进行测量路径规划,手动控制CMM测量,这种方法不但耗时且测量精度不高。本文提出了一种实时在线灰色预测模型用于控制三坐标测量机的测量。该方法分两个步骤进行:初始化数据测量和实时在线灰色预测自动测量。初始化数据测量主要完成预测用原始数据系列的定义,实时在线灰色预测自动测量则根据原始数据系列预测后续点来控制CMM进行测量。采用这种方法免去了对整个曲面进行测量路径规划,可快速准确地测量自由曲面上的数据而且明显减少测量时间。     

An industrial comparison of coordinate measuring machines in Scandinavia with focus on uncertainty statements

This paper describes an industrial comparison of coordinate measuring machines (CMMs) carried out in the Scandinavian countries from October 1994 to May 1996. Fifty-nine industrial companies with a total of 62 CMMs participated in the project and measured a comparison package with five items chosen to represent a variety of dimensions, angles, and other geometrical quantities. A tool holder, two gauge blocks, a straightedge, and a ring together with instructions on how to measure the items were produced and sent to each participant. Simple measurement tasks were observed to be carried out with good results for the majority of the participants; whereas, increasing the level of difficulty from simple length measurements to more complex geometrical quantities gave severe problems for some of the companies. This occurred even though the participants measured according to prescribed procedures. An important part of the intercomparison was to test the ability of the participants to determine measurement uncertainties. One of the uncertainties was based upon a “best guess” but nevertheless, many participants did not even report this uncertainty. Uncertainty budgeting was not used for measurements other than simple length. For each company, a comparison of their measurement ability with the reference laboratory and other Scandinavian companies was made possible. A network regarding CMMs was created in these Scandinavian countries.     

圆隙缝动静压轴承静特性分析

本文提出了一种新型动静压滑动轴承－圆隙缝动静压轴承。分析了该轴承的承载能力和刚度，并分析了设计参数对它们的影响。结果表明，该轴承性能优于传统的隙缝式轴承。而且这种轴承加工方便。很有应用前景。     

Metrological feasibilities of CMM touch trigger probes. Part I: 3D theoretical model of probe pretravel

New 3D model of the inaccuracy of a touch trigger probe used to collect coordinates of a measured object by coordinate measuring machine (CMM) is proposed. The analysis is performed both for one and two stage types of probes. The influence of a stylus length and diameter, a spring force and direction of a contact point approach are taken into consideration. The effects of frictional interaction between the stylus ball and a measured surface are also taken into consideration. The theoretical analysis of a tough trigger probe hysteresis is presented. Finally a computer simulation of mathematical modeling in the XYZ space is shown.     

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.     

Effective stylus diameter determination using near zero-width reference

A gage for low uncertainty determination of the effective diameter of styli used for probing in coordinate measuring machines is presented here. The gage embodies a near-zero width reference line which can be measured from opposing sides to obtain the effective stylus diameter. Two modified gage blocks are utilized in the construction of this artifact.     

Genetic Algorithm Modelling and Solution of Inspection Path Planning on a Coordinate Measuring Machine (CMM)

A multiple component inspection path planning problem (MCIPP) can be formulated as an optimisation problem, referred to as a non-deterministic polynomial complete problem (NP). An MCIPP consists of testing points, which will be visited by a CMM probe only once, and dummy points which are set to avoid collision and may be visited by a CMM probe more than once. This paper considers the application of genetic algorithms (GAs) acting as optimisers for optimal inspection path planning systems. The paper explores the techniques used in the GA optimal inspection path planning system. The paper also discusses the comparison of integer programming models and genetic models.     

A general method for analysing the accessibility of features using concentric spherical shells

This paper presents a general method for features accessibility analysis used in the dimensional inspection of mechanical parts by CMMs (coordinates measuring machines). It is based on the intersection of concentric spherical shells (ICSS) centred at the measurement point. This method can be applied to any type of solid or surface and is not limited by continuity or derivability constraints. Accessibility domains can be generated easily as a limit case of the ICSS. This method has been generalised to include inspection with bent probes to take into account the actual shape of the probe. It may be used to analyse the accessibility or probe approach directions for any point within or outside any object. It is also possible to determine the common accessibility domain for a set of points directly or by comparing the accessibility domain of each point. This method has potential applications in fields such as machining and robotics.     

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.     

面向三坐标测量机应用的检测特征自动提取和识别

为了解决三坐标测量机(CMM)中手工输入检测信息的问题,提出了自动提取和识别检测特征的方案。应用特征技术,实现了基于CAD模型公差特征的自动提取。利用CAD模型中几何要素标识唯一的特点,建立了STEP和QDAS中性文件的匹配,解决了几何信息和检测信息在CAD和CMM之间的传递和识别问题。在Unigraphics上进行了二次开发,使其能自动输出匹配好的STEP和QDAS文件,并能被CMM软件识别和应用。     

Quality follow-up of CMM via the measurement of microdefects

The use of CMM in industrial environments requires a surveillance of their state of quality. The implementation of the procedure which allows to ensure the quality of the measurement is often left to the user’s initiative, which is powerless in the face of the complexity of the problem. We are interested in a new type of deviation that we call microdefects. We propose indicators which characterize the microdefects. These indicators are intended to point out metrological failure of CMM axes. We propose indicators that will assess the procedure adapted to a use of CMM in an industrial environment within an integrated CMM global survey system. After an introduction of the microdefects we are interested in, we describe the quality indicators we have defined and the procedure chosen to evaluate them. We conclude with the perspective for these indicators.