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.     

Multiple orientation technique for the calibration of cylindrical workpieces on CMMs

Coordinate measuring machines (CMMs) are widely used in various fields of precision engineering and science. Although they are highly accurate instruments, for some tasks, e.g. calibration of reference artifacts, the accuracy even of the best available instruments is not sufficient.In this paper, we describe a highly accurate technique using a CMM for the measurement of cylindrical workpieces. The proposed method is a combination of multiple orientation and substitution techniques and compensates for all geometrical errors of a CMM, systematic probing effects and the bending of the workpiece due to gravity. We demonstrate the method on a cylinder gauge with flat ends that incorporates a number of different geometrical features. The evaluation of the measurement uncertainties for each characteristic was performed manually and using the Virtual CMM (VCMM) [Trapet E, Franke M, Haertig F, Schwenke H, Waeldele F, Cox M, et al. Traceability of Coordinate Measurements According to the Method of the Virtual Measuring Machine: Final Project Report MAT1-CT94-0076, PTB-Report F-35, Parts 1 and 2; 1999; Haertig F, Trapet E, Waeldele F, Wiegand U. In: Proceedings of the 5th IMEKO TC-14. Traceability of coordinate measurements according to the Virtual CMM concept; 1995. p. 245–54.]. The results show, that very low uncertainties can be achieved by the proposed measurement techniques. It is also demonstrated that the VCMM approach considers reversal effects correctly for the calculation of measurement uncertainties.     

Adaptive sampling for coordinate metrology

An iterative sampling process for dimensional measurement is presented. The strategy is based upon the use of surface normal measurement data to develop an interpolating curve between sample points. The interpolant is used to select subsequent measurement targets iteratively. The process is repeated until the measurement converges to a complete and accurate evaluation of the surface. The required sample size is proportional to part quality. The most accurate parts will require the least sample points; whereas, lower quality parts will require a greater number of total samples. The method is particularly applicable to measurement of complex surfaces with coordinate measuring machines (CMMs).     

Training in coordinate measurement using 3D virtual instruments

Coordinate metrology is a subject that has evolved driven by two important vectors: hardware and software development. At present, most 3D measuring software offer features for offline programming of the Coordinate Measuring Machines (CMM). A few software solutions enable the simulation of both the CMM and other elements involved in the measuring process, such as the human operator or an automated system for loading and unloading the measured parts. The paper presents the features and advantages offered by Delmia V5 for simulating a complete measuring environment encompassing: the CMM, the human operator, a robot or automated system for manipulating the parts. The simulations developed represent a powerful learning tool that can complement existing models for CMM training.     

Fiber deflection probe for small hole metrology

This paper presents the development of a new probing method for coordinate measuring machines (CMM) to inspect the diameter and form of small holes. The technique, referred to as fiber deflection probing (FDP), can be used for holes of approximately 100 μm nominal diameter. The expanded uncertainty obtained using this method is 0.07 μm (k = 2) on diameter. The probing system consists of a transversely illuminated fiber (with a ball mounted on the end) whose shadows are imaged using a camera. We can infer the deflection of the probe from the motion of the image seen by the camera, and we infer the position of the measured surface by adding the fiber deflection along x- and y-directions to the machine scale readings. The advantage of this technique is the large aspect ratio attainable (5 mm deep for a 100 μm diameter hole). Also, by utilizing the fiber as a cylindrical lens, we obtain sharp crisp images of the fiber position, thus enabling high resolution for measured probe deflection. Another potential advantage of the probe is that it exerts an exceptionally low force (ranging from a few micronewtons down to hundreds of nanonewtons). Furthermore, the probe is relatively robust, capable of surviving more than 1 mm over-travel, and the probe should be inexpensive to replace if it is broken. In this paper, we describe the measurement principle and provide an analysis of the imaging process. Subsequently, we discuss data obtained from characterization and validation experiments. Finally, we demonstrate the utility of this technique for small hole metrology by measuring the internal geometry of a 129 μm diameter fiber ferrule and conclude with an uncertainty budget.     

平行关节机器人坐标系统的校正

提出单基准点校正和三基准点校正两种方法解决关节型机器人坐标系统校正难题,采用优化方法求解出系统的初始关节角.用三点校正法可使位置精度达到50μm.     

Laser tracker performance quantification for the measurement of involute profile and helix measurements

Standard-conforming measurements for a large involute gear were performed with a manually operated laser tracker system and the corresponding task-specific measurement uncertainties were estimated. Especially, readers using laser trackers for inspecting large involute gears will get information of a taskspecific measurement performance for the first time, which significantly differs from the laser tracker machine specification. To ensure unambiguous and repeatable measurement results, user-friendly auxiliary tools are used, which allows the operator to probe the measurement points according to existing guidelines and standards. Measurements were taken on a robust and highly accurate large involute gear measurement standard of the Physikalisch-Technische Bundesanstalt (PTB) under laboratory conditions. The size of this gear measurement standard complies with those gears used in wind power plants. The external gear materializes a left and a right hand gear as well as a spur gear. The obtained results of profile, helix and surface measurements are presented. These research activities were carried out at the PTB in the department of coordinate metrology.     

液晶电视彩色分析仪校准系统的研究

利用相对光谱功率测量原理成功地研制了彩色分析仪校准系统,实时测量显示单元的颜色参数,并通过改变其信号源的红绿蓝3色输出比,使显示单元复现各种色温和亮度的标准白场,与彩色分析仪进行比对测量,实现对液晶等平板电视的各类彩色分析仪的校准和定标。     

The calibration and error compensation techniques for an Articulated Arm CMM with two parallel rotational axes

The calibration and error compensation techniques for an Articulated Arm Coordinate Measuring Machine (AACMM) with two parallel rotational axes are proposed. An improved six-parameter D–H model is established. The reversal techniques are used to calibrate the parallelism errors, arm lengths and zero position of the AACMM. The effects of the bending and torsion deformations caused by the gravity of the arms are removed. The experiments prove that the calibration method is simple and the measurement expanded uncertainty (_2uc$2_{u_c}$) of the developed AACMM with a measuring range of (∅200–∅1000 mm) × 250 mm is less than 10 μm after error compensation.     

Ball array calibration on a coordinate measuring machine using a gage block

The distances between the balls of a ball array used in machine geometry calibration have to be very accurate. These distances can be calibrated using a laser measurement system, which requires specially designed optical devices and measuring probes. In this paper, a new and economical alternative method for calibrating the ball array is described. A single gage block is used for measuring the standard distance at the starting position. Then, the exact distances between the balls can be obtained by using the coordinate measuring machine (CMM) probe motion. This method does not depend on the accuracy of the CMM. Also, this method does not require expensive instruments or devices, but a CMM and a gage block. A simple “parallel-plane” bracket, mounted on to the measuring end of a CMM probe, is used to determine the centers of the balls automatically and accurately.     

Automated dimensional inspection planning using the combination of laser scanner and tactile probe

Combining multiple sensors on CMMs (Coordinate Measuring Machines) is useful to fulfil the increasing requirements on both complexity and accuracy in dimensional metrology. Yet, the methodology to plan measurement strategies for systems combining different types of sensors is still a major challenge. Such planning is commonly done in an interactive way. This paper presents a methodology which can create inspection plans automatically for CMM inspection combining a touch trigger probe and a laser scanner. The inspection features are specified based on the extracted geometry features and the associated PMI (Product and Manufacturing Information) items from a CAD model. A knowledge based sensor selection method is applied to choose the suited sensor for each inspection feature. For touch trigger measurements, the sampling strategy considers the measurement uncertainty calculated by simulation. A geometry-guide method is developed for collision-free probing path generation. For laser scan measurements, the required view angles and positions of the laser scanner are determined iteratively, based on which the scan path is generated automatically. The proposed methodology is tested for several cases and validated by measurement experiments. The methodology provides suited planning results and can be used for automated dimensional inspection, i.e. Computer Aided Quality Control (CAQC).     

三坐标测量技术在汽车制造业中的应用

大量的三坐标测量机用于汽车产品质量控制,提供了一种快捷方便的检测手段。为正确进行测量和分析,许多规范和必要的辅助工具也是必须的。     

基于计算机视觉的大型工件特征点三维坐标测量方法研究

大型工件特征点三维坐标测量具有其重要性和复杂性，近年来人们提出了各种相关的测量方法，其中计算机视觉方法以其独特的优点引起了广泛的兴趣。本文着重讨论计算机视觉方法在大型工件特征点坐标测量中的应用，提出了一种准确、快速、简单的测量方法     

“Isara400”超精密坐标测量机的设计与标定

介绍了Isara 400 3维超精坐标测量机标定的关键技术,包括平台标定和系统镜面台非垂直度标定.同时,提出了一种新的超精接触探针系统,给出了这种3维灵敏度探针的标定结果.     

An experimental method for assessing the contribution of the production process variations to the task-specific uncertainty of coordinate measurements

The present paper deals with an important source of variation often neglected in uncertainty estimates of coordinate measurements: the between-sample variation. This source of variation becomes relevant to the measurement uncertainty when significant interactions occur between variations in the production process and specific limitations in the measurement process. This paper discusses some particular types of interaction which usually lead to between-sample variation in coordinate measurements. For analysing the statistical significance of the between-sample variation and for assessing its contribution to the measurement uncertainty, an experimental method using multiple calibrated workpieces is described. A case study involving the uncertainty estimation of a roundness measurement process using a coordinate measuring machine is presented. The results show the importance of considering the between-sample variation in uncertainty evaluations of coordinate measurements.