Search

Industrial X-ray computed tomography (XCT) is a nondestructive technique that can measure workpieces with non-accessible internal features or multimaterial components and assess the dimensional properties of assemblies in assembled states. Surface determination is one of its most crucial steps, which consists of determining boundary surfaces between a solid material and the surrounding air or between different solid materials. It allows for extracting surface points and assessing different features of the object from the data acquired through XCT scans. This task is particularly complex because of challenges associated with material properties, artefacts and noise. The main objective of this work is to assess not just the dimensional but also the geometric characteristics of industrial parts, which requires a more accurate definition of surface points. Therefore, we propose a new surface determination technique (SDT) in XCT to achieve subvoxel accuracy in determining surface points. We demonstrated the effectiveness and stability of our method by comparing it with other SDTs documented in the literature or with results from commercial software. The validation involved measuring various attributes, such as diameter, cylindricity and flatness, of a multi-stepped aluminium part calibrated by a coordinate measuring machine.Highlights: Surface determination techniques in X-ray computed tomography for geometrical metrology are analysed in-depth. A novel surface determination technique is proposed to assess geometric tolerances. The considered techniques are compared through experiments focused on size and form tolerances. [ABSTRACT FROM AUTHOR]

The paper presents a new method of analysis of a controlled radius (CR). The presented method was verified based on simulations of coordinate measurements and during real measurements conducted on the selected coordinate measuring machine (CMM) -- ACCURA II. In addition, the investigations were conducted by means of the Calypso metrology software and the Python programming environment. Computer simulations were performed for the selected dispersion of measurement points relating to nominal data of measured products. The actual coordinate measurements were conducted by using various measurement strategies. The created method takes into account the analysis of flattening of a considered curve, for which the measurement characteristic CR is determined. The analysis was conducted based on linear regression. The advantage of the presented method is the possibility of its implementation in software of a CMM and, consequently, the use of the above-mentioned method in industry. The new method detected flat fragments of measured objects regardless of the applied number of measurement points. [ABSTRACT FROM AUTHOR]

Reliable measurement uncertainty is a crucial part of the conformance/nonconformance decision-making process in the field of Quality Control in Manufacturing. The conventional GUM-method cannot be applied to CMM measurements primarily because of lack of an analytical relationship between the input quantities and the measurement. This paper presents calibration uncertainty analysis in commercial CMM-based Coordinate Metrology. For the case study, the hole-plate calibrated by the PTB is used as a workpiece. The paper focuses on thermo-mechanical errors which immediately affect the dimensional accuracy of manufactured parts of high-precision manufacturers. Our findings have highlighted some practical issues related to the importance of maintaining thermal equilibrium before the measurement. The authors have concluded that the thermal influence as an uncertainty contributor of CMM measurement result dominates the overall budgets for this example. The improved calibration uncertainty assessment technique considering thermal influence is described in detail for the use of a wide range of CMM users.

Precise dimensional measurements, predominantly through coordinate metrology, largely influence the quality control in manufacturing industries. Other than the standard coordinate measuring machines (CMMs), coordinate metrology also functions in conjunction with measurement systems utilizing structured light, imaging, laser triangulation, photogrammetry and computer tomography. An articulated arm coordinate measuring machine (AACMM) or portable CMM provides enhanced flexibility and diminished weight as compared to the conventional CMM. Periodic reverification of articulated arm CMM is essential to ascertain accurate and precise dimensional measurements. In the present experimental investigation, an articulated arm coordinate measuring machine has been verified as per ISO 10360–12:2016 using one-dimensional standard artefact (KOBA Step Gauge, 1220 mm). The measurement uncertainty estimation has been carried out using Monte Carlo Simulation (MCS) and compared with ISO GUM (law of propagation of uncertainties: LPU) outcomes. Established expanded uncertainties and measured mean values acquired from the two approaches were observed to be in reasonable concordance. [ABSTRACT FROM AUTHOR]

The inspection process in today's digital production cycles is acyber-physical complex including the physical collection of high-quality metrology data and extensive computational tasks to generate valuable information following, intermittently, or online with the manufacturing tasks, to support quality control or quality improvement of products, or production system's health monitoring and prognostics. In this paper, amethodology to estimate the geometric deviation zones of large coordinate metrology point clouds is presented based on afinite difference approach relying on the anisotropic diffusion analogy. Instead of heat, the normal distances between the ideal model and the measured points are considered as the independent variables in the diffusion process with respect to the time and location. The location term is discretized by finite differences and the temporal term is estimated by the forward Euler method. In order to eliminate saturation in the diffusion process, the diffusion coefficient dynamically changes in each iteration based on the variations in the standard deviation of the Euclidean distances. The developed methodology is fully implemented and avariety of validation tests and experimental studies are conducted. According to the results of the virtual tests and the experimental studies, the developed methodology reduces on average about 60% of the number of measured points and consequently the computation time, even for highly complex surfaces with considerable inherent manufacturing errors, without imperiling the accuracy of the deviation zone estimation. [ABSTRACT FROM AUTHOR]

This paper is concerned with the evaluation of the uncertainties associated with Gaussian-associated features following the GUM methodology. We show how sensitivity matrices necessary for a GUM uncertainty evaluation can be calculated and how the variance matrices associated with the feature parameters can be estimated for a range of complete and partial features common in engineering. Example results are given in tables that allow practitioners to estimate, a priori, the uncertainties associated with fitted parameters, given a proposed measurement strategy for the case in which the point-cloud variance matrix is a multiple of the identity matrix. The sensitivity matrices can be used to evaluate the uncertainties for associated features for more general point-cloud variance matrices. All the calculations involved are direct and involve no optimization or Monte Carlo sampling; they can be implemented in spreadsheet software, for example. [ABSTRACT FROM AUTHOR]

As far as machine parts are concerned, accuracy can be defined in many aspects. In order for a workpiece to be functional, dimensional and surface roughness requirements are not enough. Accuracy of geometric elements and position tolerances is necessary information. The notation, definitions, interpretations and general values of geometric tolerances are defined by standards. Nevertheless, there are several mathematical methods of calculating values based on data measured by means of coordinate measuring machines. Standards demand the use of the minimum zone method in assessing form deviation without mentioning the way of obtaining it. In this paper, the minimum zone method, which is an iterative algorithm, was investigated. Thus, the result of flatness measurement was calculated by continuous approximation. There are various methods of defining the steps of iteration, affecting the length of time and accuracy of the flatness value. The aim of the research was to examine the characteristics of two non-commercial software solutions for assessing the minimum zone in comparison with the commercial CMM software. Based on the analysis, it can be concluded that the developed software solutions are efficient in assessing flatness error and that the differences between these and the commercial software are negligible.

Reliable measurement uncertainty is a crucial part of the conformance/nonconformance decision-making process in the field of Quality Control in Manufacturing. The conventional GUM-method cannot be applied to CMM measurements primarily because of lack of an analytical relationship between the input quantities and the measurement. This paper presents calibration uncertainty analysis in commercial CMM-based Coordinate Metrology. For the case study, the hole-plate calibrated by the PTB is used as a workpiece. The paper focuses on thermo-mechanical errors which immediately affect the dimensional accuracy of manufactured parts of high-precision manufacturers. Our findings have highlighted some practical issues related to the importance of maintaining thermal equilibrium before the measurement. The authors have concluded that the thermal influence as an uncertainty contributor of CMM measurement result dominates the overall budgets for this example. The improved calibration uncertainty assessment technique considering thermal influence is described in detail for the use of a wide range of CMM users. [ABSTRACT FROM AUTHOR]

This paper is concerned with the generation of numerical artefacts, that is, reference data sets, for assessing the accuracy and fitness of purpose of software for computing minimum zone (MZ, Chebyshev) associated features. We describe an algorithm for generating datasets corresponding to a pre-specified best-fit surface and form error. We use a Gaussian process model to generate form errors that are spatially correlated. The form errors can be drawn from multivariate Gaussian or rectangular distributions. For the latter case a Gaussian copula is used to construct a multivariate multivariate distribution with the pre-assigned correlation. We illustrate the data generation on MZ circle fitting problems. We also describe an approximate MZ circle fitting problem that can be solved using linear programming.

Coordinate metrology can be thought of as a two-stage process, the first stage using a coordinate measuring system to gather coordinate data – point clouds – related to a workpiece surface, the second extracting a set of parameters or characteristics from the data. In this paper, we describe a range of straightforward, approximate models of CMM behaviour that can be used to generate variance matrices associated with point clouds. In particular, we describe models that incorporate spatial correlation to capture the smooth departure of CMM behaviour from ideal geometry. We also discuss how variance matrices associated with point clouds can be propagated through to variance matrices associated with derived features.

We propose a unified theory for the metrological treatment of helical machine elements such as cylindrical and conical gears, worms, and screw threads. The main idea is to introduce a universal 3D geometry model for threaded components that provides for distinct parameterization using a unique set of geometry parameters and that offers and a functional description of the transverse profile. Using modern 3D coordinate measuring technology, a holistic evaluation algorithm yields the actual geometry as the result of a high dimensional best-fit procedure and form deviations as corresponding residuals. All determinants and evaluation parameters can then be calculated from the set of actual geometry parameters. By applying certain constraints to the model to be fitted, the novel method can be reduced to the established 2D methods and hence meets demands for the comparison of the two procedures. The results of the novel approach have proven to be very stable and they enable the evaluation of areal measurements with no loss of information. [ABSTRACT FROM AUTHOR]

In this work an approach to investigate measurement uncertainty in coordinate metrology is presented, based on fitting Gaussian random fields to high-density point clouds produced by measurement repeats. The fitted field delivers a depiction of the spatial distribution of random measurement error over a part geometry, and can incorporate local bias information through further measurement or with the use of an external model to obtain a complete, spatial uncertainty map. The statistical model also allows the application of Monte Carlo simulation to investigate how error propagates through the data processing pipeline ultimately affecting the determination of features of size and the verification of conformance to specifications. The proposed approach is validated through application to simulated test cases involving known measurement error, and then applied to a real part, measured with optical and contact technologies. The results indicate the usefulness of the approach to estimate measurement uncertainty and to investigate performance and behaviour of measurement solutions applied to the inspection and verification of industrial parts. The approach paves the way for the implementation of automated measurement systems capable of self-assessment of measurement performance. • Gaussian random fields used to build statistical point cloud models. • Statistical models provide spatial distribution of measurement uncertainty. • Error propagation in point cloud processing analysed via Monte Carlo simulation. • Statistical models can be built for height maps and 3D point cloud surface data. [ABSTRACT FROM AUTHOR]

This paper is concerned with the evaluation of the uncertainties associated with Gaussian-associated features following the GUM methodology. We show how sensitivity matrices necessary for a GUM uncertainty evaluation can be calculated and how the variance matrices associated with the feature parameters can be estimated for a range of complete and partial features common in engineering. Example results are given in tables that allow practitioners to estimate, a priori, the uncertainties associated with fitted parameters, given a proposed measurement strategy for the case in which the point-cloud variance matrix is a multiple of the identity matrix. The sensitivity matrices can be used to evaluate the uncertainties for associated features for more general point-cloud variance matrices. All the calculations involved are direct and involve no optimization or Monte Carlo sampling; they can be implemented in spreadsheet software, for example.

Recent ISO Geometrical Product Specifications (GPS) standards have introduced multiple ways to define geometrical deviations in design and manufacturing. These definitions depend on an association operation, which fits an ideal-form surface to a nonideal-form feature. This paper describes new mathematical and computational challenges that stem from these recent developments and provides a unification of different points of view using classical definitions of Riemann sums and integration. It also provides important practical means to define association operations for verification using digital technologies. [ABSTRACT FROM AUTHOR]

On-line data collection from the manufactured parts is an essential element in Industry 4.0 to monitor the production’s health, which required strong data analytics. The optical metrology-based inspection of highly reflective parts in a production line, such as parts with metallic surfaces, is a difficult challenge. As many on-line inspection paradigms require the use of optical sensors, this reflectivity can lead to large amounts of noise, rendering the scan inaccurate. This paper discusses a method for noise reduction and removal in datapoints resulting from scanning the reflective planar surfaces. Utilizing a global statistic-based iterative approach, noise is gradually removed from the dataset at increasing percentages. The change in the standard deviation of point-plane distances is examined, and an optimal amount of noisy data is removed to reduce uncertainty in representing the workpiece. The developed algorithm provides a fast and efficient method for noise reduction in optical coordinate metrology and scanning.

We propose a unified theory for the metrological treatment of helical machine elements such as cylindrical and conical gears, worms, and screw threads. The main idea is to introduce a universal 3D geometry model for threaded components that provides for distinct parameterization using a unique set of geometry parameters and that offers and a functional description of the transverse profile. Using modern 3D coordinate measuring technology, a holistic evaluation algorithm yields the actual geometry as the result of a high dimensional best-fit procedure and form deviations as corresponding residuals. All determinants and evaluation parameters can then be calculated from the set of actual geometry parameters. By applying certain constraints to the model to be fitted, the novel method can be reduced to the established 2D methods and hence meets demands for the comparison of the two procedures. The results of the novel approach have proven to be very stable and they enable the evaluation of areal measurements with no loss of information.

• Full model of the evaluation method of gear profile deviations considering installation errors. • Results showed that the method could significantly decrease influence of installation errors. • The application range of EMI-Profile method was simulated. Gear elemental deviations, such as profile deviations, are important items for gear accuracy evaluation and generally measured on a Gear Measurement Center or Coordinate Measuring Machine. There are installation errors when the gear installed on the shaft positioned in the center before measurement. Therefore, the evaluation method of gear profile deviations considering installation errors was introduced to measure gear profile deviations without the precise adjustment of installation errors in the study. In this method, installation errors were described as the installation eccentricity error and the installation wobbling error. Then, the installation error model, the coordinate transformation model and the tooth profile deviation evaluation method were established. The gear base circle center was calculated with the tooth profile measurement points. Then, the tooth profile measurement points under the machine coordinate system were transformed into the coordinates in the work-piece coordinate system. After that, the profile deviations were evaluated according to ISO 1328-1:2013. The measurement experiments were carried out on a gear measurement center under different installation errors. The application scope of the method was discussed by simulation. The range of the total profile deviation obtained with this method was 0.51 μm under four groups of the installation conditions, whereas the value obtained with GMC was 3.17 μm. Experimental results showed that this method could significantly decrease the influence of installation errors for measuring gear profile deviations under the rough positioning conditions of product gears. [ABSTRACT FROM AUTHOR]

Für viele Aufgaben der modernen Qualitätssicherung sind Koordinatenmessgeräte mit Multisensorik von Vorteil. In den letzten 25 Jahren wurden durch eine kontinuierliche Erweiterung des Funktionsumfangs bestehender sowie die Entwicklung neuer Sensoren viele neue Lösungen sowohl für hohe Anforderungen an die Genauigkeit als auch für Messungen mit hoher Geschwindigkeit im Fertigungstakt geschaffen. Coordinate measuring machines with multisensor technology are advantageous for many tasks of modern quality assurance. Over the past 25 years, the continuous expansion of the functional range of existing sensors and the development of new sensors have created many new solutions for both high-accuracy requirements and high-speed measurements in the production cycle. [ABSTRACT FROM AUTHOR]

Wenn heute von der Digitalisierung der Produktion gesprochen wird, löst das in der Koordinatenmesstechnik häufig Verwunderung aus, weil die Koordinatenmesstechnik von Anfang an digitale Verfahren genutzt hat. Ohne die Möglichkeiten der Digitalisierung würde es sie gar nicht geben. Erst die rechnergestützte Auswertung ermöglicht eine effiziente Verknüpfung der gemessenen Koordinatenpunkte zu Merkmalen der Produktgeometrie. Heute werden bei optischen Messsystemen Millionen von Koordinatenpunkten in Sekunden aufgenommen und verarbeitet. Die Anwendung der Computertomographie für die Koordinatenmesstechnik wurde erst durch die heute zur Verfügung stehende Rechnerleistung möglich. Aufgrund der vorhandenen digitalen Systeme wurde die Koordinatenmesstechnik bei der Vernetzung schon frühzeitig eingebunden. Während am Anfang die rechnergestützte Übertragung von Ergebnissen im Vordergrund stand, sind heute Koordinatenmesssysteme teilweise vollständig in digital gesteuerte Produktionsprozesse integriert. The digitization is a key element of recent developments in production technology. From the point of view of coordinate metrology this is quite surprising, because coordinate metrology has applied digital technologies right from its start. Without digital data processing coordinate metrology would not even exist. The computer-based evaluation is the prerequisite for the efficient fusion of the measured point coordinates to get attributes of product geometry. Today optical measurement systems generate and process several millions of data points per second. The application of computed tomography was made possible by the high computing power of computer systems available today. Coordinate metrology instruments were integrated in evolving IT networks at a very early stage because the digital systems already existed in this field. While at the beginning the focus laid on the digital transfer of measurement results, today more and more devices of coordinate metrology are completely integrated in digitally controlled production processes. [ABSTRACT FROM AUTHOR]

Beschrieben wird eine vollständige Definition für zylindrische Evolventenverzahnungen als dreidimensionales Formelement. Grundlage ist ein evolventisches Koordinatensystem. Mit ihm lassen sich innen und außen verzahnte Räder mit linkssteigender und rechtssteigender Flankenrichtung sowie Geradverzahnungen darstellen. Besondere Bedeutung gewinnt diese Darstellung im Bereich der Verzahnungs- und Koordinatenmesstechnik. Gewöhnlich liegen die Messpunkte als kartesische Koordinaten in Form von Tastkugelmittelpunkten des Antastelements vor. Diese können außerhalb ihrer Bezugsflächen nahezu beliebig über die Flanke verteilt sein. Der Einsatz von Evolventenkoordinaten ist Grundlage für eine einfache Auswertung der Verzahnungsparameter. Die dargestellten Definitionen und Algorithmen ergänzen bestehende Richtlinien und Normen, in denen die Zusammenhänge bisher nicht beschrieben sind. A holistic definition of cylindrical involute gears is presented in the form of a three-dimensional form element. It is based on an involute coordinate system and can be used for internal and external gears with left-hand and right-hand slope directions as well as for spur gears. This representation is of particular importance in the fields of gear metrology and coordinate measuring technology. Usually, the measuring points are given in Cartesian coordinates in the form of probe centers of a spherical probing element. These points can be tracked outside their reference faces and distributed almost arbitrarily over the flank. The use of involute coordinates is the basis for a simple evaluation of gearing parameters. The presented definitions and algorithms complement existing guidelines and standards, in which the mathematical relations have not yet been described. [ABSTRACT FROM AUTHOR]

• A novel involute gear coordinate system is introduced. • General definitions and mathematical calculation methods are provided. • They allow 3D coordinates to be evaluated in conventional evaluation cross sections. • The definitions and formulas presented complete existing standards and guidelines. • They provide clear instructions required for handling a gear as a full 3D object. The definition of 3D workpiece coordinates for cylindrical involute gears, together with their formal relation to conventional cross sections, are prerequisites for an unambiguous and thus reliable evaluation of 3D measurement data. Both will be described in this article, as no corresponding information is currently available in national or international standards and guidelines. The definitions and calculation methods presented here are part of reference algorithms used by the Physikalisch-Technische Bundesanstalt (PTB), the national metrology institute of Germany, to certify gear evaluation software. [ABSTRACT FROM AUTHOR]

Fringe projection profilometry in combination with other optical measuring technologies has established itself over the last decades as an essential complement to conventional, tactile measuring devices. The non-contact, holistic reconstruction of complex geometries within fractions of a second in conjunction with the lightweight and transportable sensor design open up many fields of application in production metrology. Furthermore, triangulation-based measuring principles feature good scalability, which has led to 3D scanners for various scale ranges. Innovative and modern production processes, such as sheet-bulk metal forming, thus, utilize fringe projection profilometry in many respects to monitor the process, quantify possible wear and improve production technology. Therefore, it is essential to identify the appropriate 3D scanner for each application and to properly evaluate the acquired data. Through precise knowledge of the measurement volume and the relative uncertainty with respect to the specimen and scanner position, adapted measurement strategies and integrated production concepts can be realized. Although there are extensive industrial standards and guidelines for the quantification of sensor performance, evaluation and tolerancing is mainly global and can, therefore, neither provide assistance in the correct, application-specific positioning and alignment of the sensor nor reflect the local characteristics within the measuring volume. Therefore, this article compares fringe projection systems across various scale ranges by positioning and scanning a calibrated sphere in a high resolution grid.

Abstract A key enabler for innovation in manufacturing is the competent use of advanced measuring equipment. As reported [1, 2], operators with their decisions are frequently the most relevant error sources in Coordinate Metrology, especially when dealing with new measuring technologies supporting Digital Manufacturing. In this article, new concepts for structuring of learning material as well as development and distribution of learning material for training in Coordinate Metrology are presented. A 10-steps model is used to structure training material and new tools are presented for a global collaboration in development, updating and distribution of learning material. With the methods used, fast and efficient learning material update and distribution is made available to meet the ongoing development of measuring equipment and international standards and bridge the world of Education and Industry 4.0. [ABSTRACT FROM AUTHOR]

Inspired by previous experience in freeform metrology practice and industrial needs, the Czech Metrology Institute developed the freeform standard Hyperbolic paraboloid 300 of dimensions 300 mm × 300 mm × 160 mm with a freeform functional area of approximately 64 000 mm 2 . The paper presents a mathematical–metrological approach to finding a suitable strategy for calibrating the freeform standard on a coordinate measuring machine with a tactile probing system. The calibration strategy consists in the development of a freeform digital twin of the standard, i.e. a continuous digital representation of a freeform measured value with associated uncertainty. A procedure to estimate the uncertainty of the coordinate freeform measurement is described, too. After calibration, the Hyperbolic paraboloid 300 standard will become a verification gauge suitable for use as a precision reference in advanced freeform metrology similar to common verification gauges widely used in length metrology. [Display omitted] • Well-designed freeform standards expand established verification standards. • Calibration of freeform geometries is a non-standardised field in length metrology. • Calibration of freeform geometries can be realised through a freeform digital twin. • Evaluation of measurement for freeform geometries is increasingly urgent. • Coordinate measuring systems can be verified using freeform digital twins. [ABSTRACT FROM AUTHOR]

Nowadays, simulators facilitate tasks performed daily by the engineers of different branches, including coordinate metrologists. Sometimes it is difficult or almost impossible to program a Coordinate Measuring Machine (CMM) using standard methods. This happens, for example, during measurements of nano elements or in cases when measurements are performed on high-precision (accurate) measuring machines which work in strictly air-conditioned spaces and the presence of the operator in such room during the programming of CMM could cause an increase in temperature, which in turn could make it necessary to wait some time until conditions stabilize. This article describes functioning of a simulator and its usage during Coordinate Measuring Machine programming in the latter situation. Article also describes a general process of programming CMMs which ensures the correct machine performance after starting the program on a real machine. As an example proving the presented considerations, measurement of exemplary workpiece, which was performed on the machine working in the strictly air-conditioned room, was described

Already developed and applied engineering information, it is often stored and forgotten. Current approaches for information retrieval are not effective enough in understanding of engineering contents, because they are not developed to share, reuse and represent information of an engineering domain. This paper presents the current state of development engineering ontology (EO) and suggests the method of its development at conceptual level, in order to reuse and share knowledge in domain of coordinate metrology (CM). Furthermore, the method defines development of ontology for the construction of knowledge base, as one of the basic components of an intelligent system for the inspection of prismatic parts on coordinate measuring machine (CMM). The proposed method is implemented in the software Protégé on the example of one measuring part.

Now equipped with touch trigger probes machine tools are increasingly used to measure workpieces for various tasks such as rapid setup, compensation of final tool paths to correct part deflections and even verify conformity to finished tolerances. On five-axis machine tools, the use of data acquired for different rotary axes positions angles brings additional errors into play, thus increasing the measurement errors. The estimation of the machine geometric error sources, using such methods as the scale and master ball artefact (SAMBA) method, and their use to calibrate machine tools may enhance five-axis on-machine metrology. The paper presents the use of the ball dome artefact to validate the accuracy improvement when using a calibrated model to process the machine tool axis readings. The inter-axis errors and the scale gain errors were targeted for correction as well the measuring tool length and lateral offsets. Worst case and mean deviations between the reference artefact geometry and the on-machine tool measurement is reduced from 176 and 70 µm down to 31 and 12 µm for the nominal and calibrated machine stylus tip offsets respectively.

Coordinate metrology processes typically include the measurement of a limited number of discrete 3D points from the measured surface to estimate the geometric deviation zone of the entire surface from an ideal geometry. Three main computational tasks are required in coordinate metrology of manufactured surfaces including Point Measurement Planning (PMP), Substitute Geometry Estimation (SGE), and Deviation Zone Evaluation (DZE). The issue of uncertainties in the results of any of these three tasks potentially jeopardizes the accuracy of the entire inspection process. It is also shown recently that interactive closed-loops between DZE and PMP, or SGE will increase the efficiency, and reduce the sources of uncertainties in the computational processes. This paper presents a methodology to complete a comprehensive DZE for the entire measured surface using the geometric deviations of a limited number of measured discrete sample points. The result of a detailed DZE is a skin model of the measured workpiece which represents the geometric deviation at any point on the measured surface from the ideal geometry. The developed skin model is definitely needed when the inspection results are used for all possible downstream processes, planning for precise finishing operations, manufacturing error compensation, closed-loop of manufacturing and inspection, dynamic process control, or accurate verification of design tolerances. The developed methodology in this paper uses a finite element approach to solve the differential equation for detailed DZE of the entire surface estimating the geometric deviations for any location that is not measured on the surface. The methodology is fully implemented and employed in various case studies on several industrial parts. The resulting skin models are examined and successful results are achieved. The developed methodology can be easily adopted by commonly used coordinate metrology computational software tools. [ABSTRACT FROM AUTHOR]

Due to the rigorous requirements for implementation of virtual models of CMMs, such models are primarily used in high-profile calibration laboratories. This paper presents a novel methodology for implementing a Virtual CMM model capable of correct uncertainty determination for measurements performed in less stable, industrial conditions. Verification results obtained under varying ambient conditions are also presented to prove the correctness of proposed methodology. [ABSTRACT FROM AUTHOR]

Evaluation of geometric deviations for the purpose of determining compliance with specified form tolerances requires the acquisition of numerous measured data points and extensive computation to accurately characterize the inspected part’s geometry. If there are not enough data points measured or when the measured points are not distributed properly on the measured surface a high level of uncertainty in characterizing the inspected part’s geometry can be expected. However, increasing the number of data point also significantly increases the computational time and also increases computational uncertainty by adding to instability of the optimization process required to find the minimum deviation zone. Selections of number and location of the measured date points need to be performed by understanding the significance of these two sources of uncertainties. This paper discussed the effect of sampling procedure on uncertainty and precision of flatness inspection.

The use of machine tools for on-machine coordinate measurement on the workpiece is becoming commonplace. However, numerous errors can adversely affect the measurement accuracy. For instance, the inter-axis parameters are major contributors to the overall machine tool's inaccuracy hence estimation and compensation of such errors are prerequisite to fully exploit the machine's measurement capability. This paper presents a scheme to assess the accuracy of coordinate measurement by probing a precision sphere mounted on the machine table for different rotary axes indexations. Only the sphericity of the reference sphere is assumed and neither its size nor position. All individual probing data from all indexations are used for the assessment of the apparent out of sphericity of the reference sphere. Machine readings are processed either directly, using the machine nominal model, or using a compensated model. This provides a fast method to validate on-machine measurement before and after compensation with the exception of isotropic scale effects.

A micro-probe based on laser trapping has been proposed for the probe system of a nano-coordinate measuring machine. This study focused on the “shadow effect,” which is the case wherein a partial beam for laser trapping is shaded by the specimen. A radially polarized beam was introduced to improve the shadow effect. As the result of increasing the trapping efficiency by 3.2 times, this high-efficient laser trapping made it possible to extend the measurable range of the vertical surface under the shadow effect.