CMM Measurement Uncertainty Reduction via Sampling Strategy Optimization

2008 ◽  
Author(s):  
Giovanni Moroni ◽  
Stefano Petro`
Keyword(s):  
Measurement Uncertainty ◽  
Measurement Errors ◽  
Coordinate Measuring Machine ◽  
Sampling Strategy ◽  
Uncertainty Reduction ◽  
Repeated Measurements ◽  
Trade Off ◽  
Geometrical Error ◽  
Measuring Machine

Uncertainty is a key concept in any environment which involves measurements to ensure process quality: a trade-off has to be found between measurement costs, which increase as uncertainty lowers, and costs related to measurement errors. In mechanics, geometrical conformance is a common requirement. Two similar standards series deal with the problem of uncertainty in geometrical error estimate: ASME B89.7.3 and ISO 14253. Geometrical inspection is often performed by means of a “Coordinate Measuring Machine” (CMM). For a CMM, a trade off between measurement and errors costs may be found by optimizing the sampling strategy. In this work a cost function will be proposed as support for finding a trade-off between measurement uncertainty and costs. This function may be optimized by means of an heuristic algorithm. The method will involve repeated measurements of calibrated parts to evaluate uncertainty (like in ISO/TS 15330-3). A case study will be proposed.

Surface Texture Measurement with Profile Method Using Six-Axis Coordinate Measuring Machine

2021 ◽  
Vol 410 ◽  
pp. 872-877
Author(s):  
Andrey V. Kochetkov ◽  
Andrey A. Troshin ◽  
Oleg V. Zakharov
Keyword(s):  
Surface Texture ◽  
Measurement Errors ◽  
Coordinate Measuring Machine ◽  
Texture Measurement ◽  
Analytical Geometry ◽  
Complex Shapes ◽  
Measurement Results ◽  
Measuring Machine ◽  
Cartesian Coordinate ◽  
Filtering Effect

Currently the measurement of surface texture in mechanical engineering is traditionally carried out using profilometers. Modern profilometers do not allow measuring of surfaces with complex shapes. This is due to the different sensitivity of the sensor and the discreteness of the movements along the axes of the Cartesian coordinate system. Coordinate Measuring Machines are devoid of such a drawback. However, stylus of the coordinate measuring machine has a diameter many times larger than the diamond stylus of the profilometer. Therefore, there is a mechanical filtering effect, that affects the results of measuring the parameters of the surface texture. In this paper a mathematical model of the contact of the spherical stylus and a rough surface based on analytical geometry is proposed. Influence of the diameter of the spherical stylus on the maximum measurement errors of a amplitude parameters are investigated. Seven amplitude parameters Rp, Rv, Rz, Ra, Rq, Rsk, Rku of the surface texture are modeled. Coordinate measuring machine and profilometer with stylus diameter of 2 μm measurement results are compared. it was concluded that the stylus diameter of the coordinate measuring machine when measuring the surface texture should be no more than 20 μm.

Calibrator for 2D Grid Plate Using Imaging Coordinate Measuring Machine with Laser Interferometers

2015 ◽  
Vol 9 (5) ◽  
pp. 541-545 ◽  
Author(s):  
Mariko Kajima ◽  
◽  
Tsukasa Watanabe ◽  
Makoto Abe ◽  
Toshiyuki Takatsuji
Keyword(s):  
Measurement Method ◽  
Laser Interferometer ◽  
Coordinate Measuring Machine ◽  
Calibration Procedure ◽  
Expanded Uncertainty ◽  
Geometrical Error ◽  
Grid Plate ◽  
Measuring Machine ◽  
Laser Interferometers

A calibrator for 2D grid plates have been developed. The calibrator was based on a commercial imaging coordinate measuring machine (imaging CMM). A laser interferometer for the calibration of the x-coordinate and two laser interferometers for the calibration of the y-coordinate were attached to the imaging CMM. By applying multistep measurement method for the calibration procedure, the geometrical error in the calibrator was reduced. The calibration of a precision 2D grid plate was demonstrated, and the expanded uncertainty was estimated to be 0.2 μm (k =2).

How Geometrical Tolerances Affect the Measurement of Reciprocal Alignment of Two Different Assemblies: A Case Study

2010 ◽  
Author(s):  
David Vetturi ◽  
Matteo Lancini ◽  
Ileana Bodini
Keyword(s):  
Numerical Simulations ◽  
Angular Displacement ◽  
European Space Agency ◽  
Coordinate Measuring Machine ◽  
Linear Displacement ◽  
Repeated Measurements ◽  
Uncertainty Sources ◽  
Component Design ◽  
Measuring Machine ◽  
The Right

Often a designer has the problem to apply a suitable system of geometrical and dimensional tolerances to an assembly. The right solution is not unique, in fact it depends on the chosen parameters. If the tolerances have to be optimized, some important parameters have to be taken into account, e.g. the efficiency of each prescription, or if this last is reachable, or it can be verified and how much the realization costs. The authors opinion is that a statistical approach based on the Monte Carlo Method is very useful when the tolerances chains are complex. This paper shows an application of this method in order to verify the functional alignment between two assemblies and a critical analysis of the uncertainty in phase both of the component design and test. This study has been developed thanks to the strict requirements imposed by ESA (European Space Agency) on the components that Thales Alenia Space has to realize within the LISA Pathfinder experiment. The very critical aspect of this work is to reciprocally align two cylindrical elements of two different assemblies. The specifications require 100 μm as maximum linear displacement and 300 μrad as maximum angular displacement. Moreover this prescriptions have to be verified also when the two elements are independently moving. To be able to reach such strict accuracy level the components have been assembled in an ISO 100 class cleanroom and the work space was a 3D Coordinate-Measuring Machine (CMM). The cylindrical elements have a 10 mm diameter, so the value of the measurement uncertainty associated with the alignment check is fundamental. Starting from the different uncertainty sources, the measurability and verifiability of the alignment have been considered and evaluated. The overall uncertainty has been assessed by numerical simulations which have taken into account the dimensional, geometrical and form tolerances as well as the instrumental uncertainty of the 3D CMM. This estimation has been positively validated by a session of repeated measurements. Numerical simulations have also allowed performing a sensitivity analysis, in order to give information about which sources more contribute to the overall uncertainty.

scholarly journals Performance Investigation of CMM Measurement Quality Using Flick Standard

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Salah H. R. Ali
Keyword(s):  
Measurement Errors ◽  
Coordinate Measuring Machine ◽  
Scanning Speed ◽  
Data Sets ◽  
Evaluation Tool ◽  
Roundness Error ◽  
Application Range ◽  
Evaluation Algorithm ◽  
Measuring Machine ◽  
High Level

Quality of coordinate measuring machine (CMM) in dimension and form metrology is designed and performed at the NIS. The experimental investigation of CMM performance is developed by using reference Flick standard. The measurement errors of corresponding geometric evaluation algorithm (LSQ, ME, MC, and MI) and probe scanning speed (1, 2, 3, 4, and 5 mm/s) are obtained through repeated arrangement, comparison, and judgment. The experimental results show that the roundness error deviation can be evaluated effectively and exactly for CMM performance by using Flick standard. Some of influencing quantities for diameter and roundness form errors may dominate the results at all fitting algorithms under certain circumstances. It can be shown that the 2 mm/s probe speed gives smaller roundness error than 1, 3, 4, and 5 mm/s within 0.2 : 0.3 μm. It ensures that measurement at 2 mm/s is the best case to satisfy the high level of accuracy in the certain condition. Using Flick standard as a quality evaluation tool noted a high precision incremental in diameter and roundness form indication. This means a better transfer stability of CMM quality could be significantly improved. Moreover, some error formulae of data sets have been postulated to correlate the diameter and roundness measurements within the application range. Uncertainty resulting from CMM and environmental temperature has been evaluated and confirmed the quality degree of confidence in the proposed performance investigation.

scholarly journals Information Contents of a Signal at Repeated Positioning Measurements of the Coordinate Measuring Machine (CMM) by Laser Interferometer

2016 ◽  
Vol 16 (5) ◽  
pp. 273-279 ◽  
Author(s):  
Tomáš Stejskal ◽  
Tatiana Kelemenová ◽  
Miroslav Dovica ◽  
Peter Demeč ◽  
Miroslav Štofa
Keyword(s):  
Permanent Deformation ◽  
Coordinate Measuring Machine ◽  
Repeated Measurements ◽  
Time Interval ◽  
Passive Resistance ◽  
Complex Information ◽  
Wear And Tear ◽  
Measuring Machine ◽  
The Moment ◽  
Spatial Positioning

Abstract The input of this paper lies in displaying possibilities how to determine the condition of a coordinate measuring machine (CMM) based on a large number of repeated measurements. The number of repeated measurements exceeds common requirements for determining positioning accuracy. The total offset in the accuracy of spatial positioning consists of partial inaccuracies of individual axes. 6 basic errors may be defined at each axis. In a triaxial set, that translates into 18 errors, to which an offset from the perpendicularity between the axial pairs must be added. Therefore, the combined number of errors in a single position is 21. These errors are systemic and stem from the machine’s geometry. In addition, there are accidental errors to account for as well. Accidental errors can be attributed to vibrations, mass inertness, passive resistance, and in part to fluctuations in temperature. A peculiar set of systemic errors are time-varying errors. The nature of those errors may be reversible, for instance if they result from influence of temperature or elastic deformation. They can be also irreversible, for example as a result of wear and tear or line clogging, due to loosened connection or permanent deformation of a part post collision. A demonstration of thermal equalizing of the machine’s parts may also be observed in case of failure to adhere to a sufficient time interval from the moment the air-conditioning is turned on. Repeated measurements done on a selected axis with linear interferometer can provide complex information on the CMM condition and also on the machine’s interaction with the given technical environment.

scholarly journals A Random Factorial Design of Experiments Study on the Influence of Key Factors and Their Interactions on the Measurement Uncertainty: A Case Study Using the ZEISS CenterMax

2019 ◽  
Vol 10 (1) ◽  
pp. 37 ◽  
Author(s):  
Michaela Kritikos ◽  
Lissette Concepción Maure ◽  
Alfredo Alejandro Leyva Céspedes ◽  
Daynier Rolando Delgado Sobrino ◽  
Róbert Hrušecký
Keyword(s):  
Design Of Experiments ◽  
Measurement Uncertainty ◽  
Factorial Design ◽  
Coordinate Measuring Machine ◽  
Standard Uncertainty ◽  
Step Width ◽  
Key Factors ◽  
Measuring Machine ◽  
Factorial Design Of Experiments ◽  
Measurement And Evaluation

This paper addresses the uncertainty analysis in the case of a coordinate measuring machine. The main goal was analyzing, quantifying, and drawing conclusions on the influence of key factors and their interactions on the measurements’ uncertainty of the variable’s parallelism, angularity, roundness, diameter, and distance. In order to achieve this goal, a Random Factorial Design of Experiments was designed and implemented. It focused on the factors Stylus diameter, Step width, and Speed using three random levels each. For the solution of the experiment, an analysis of variance was used. The study was carried out on the coordinate measuring machine (CMM) ZEISS CenterMax. It was concluded that the interaction effects among Stylus diameter, Step width, and Speed were active at a confidence level of 95%. Besides, it was possible to estimate random factors‘ variance and their contribution to the total variation. Among the main effects, the Stylus diameter showed to be the one with the biggest influence. The paper also quantifies the influence in the measurement uncertainty, where the highest value of standard uncertainty belonged to the Stylus diameter in the evaluation of the variable’s angularity and diameter. Besides, the Speed factor was proved to have the biggest influence on the roundness’ measurement and evaluation.

Development of a Novel Artifact as a Reference for Gear Pitch Measuring Instruments

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Yohan Kondo ◽  
Kazuyuki Sasajima ◽  
Sonko Osawa ◽  
Osamu Sato ◽  
Masaharu Komori
Keyword(s):  
Measurement Uncertainty ◽  
Coordinate Measuring Machine ◽  
Measuring Instruments ◽  
Pitch Accuracy ◽  
Gear Teeth ◽  
Reference Axis ◽  
Small Uncertainty ◽  
Orientation Technique ◽  
Measuring Machine ◽  
Pitch Deviation

The pitch accuracy of a gear is graded on the order of 0.1 μm in ISO 1328-1; therefore, it is necessary for gear measuring instruments (GMIs) to be able to measure gears with the required high accuracy. GMIs are evaluated by measuring a calibrated gear or a gearlike artifact. It is, however, difficult to obtain a measurement uncertainty of less than 0.1 μm. The reason for this difficulty is that a gear artifact has a form error and surface roughness, and that the measurement position on the gear face differs slightly from the calibrated position. In view of this situation, we propose a novel multiball artifact (MBA), which is composed of equally spaced pitch balls, a centering ball, and a datum plane. The pitch balls are assumed to act as gear teeth by calibrating the angular pitch between the centers of each pitch ball. The centering ball and the datum plane are used to set a reference axis of the virtual gear. We manufactured an MBA with the pitch balls arranged on a curvic coupling. The angular pitch deviation between the centers of each pitch ball was calibrated using a coordinate measuring machine (CMM) and adopting the multiple-orientation technique. A master gear was also calibrated for comparison. The measurement uncertainty for the cumulative angular pitch deviation was 0.45 arc sec for the MBA and 1.58 arc sec for the master gear. The MBA could be calibrated with small uncertainty compared with the master gear. After the calibration, a virtual gear of the MBA was built using the calibration value. The virtual gear was measured using the gear-measuring software on the CMM. The measurement value was equal within the range of uncertainty of calibration value. It is verified that the superiority of the MBA to the gear artifact is due to the following reasons: (1) The balls can be manufactured with an accuracy of several tens of nanometers. (2) The calibrated result for the MBA is almost independent of a probe-positioning error because the centers of each pitch ball can be measured at multiple points. (3) In setting the reference axis, the gear artifact generally uses a datum cylinder, in contrast, the MBA uses more accurate ball.

scholarly journals Accuracy of three-dimensional photogrammetry and cone beam computed tomography based on linear measurements in patients with facial deformities

2020 ◽  
pp. 20200001
Author(s):  
Zhenqi Zhao ◽  
Lizhe Xie ◽  
Dan Cao ◽  
Iman Izadikhah ◽  
Pengcheng Gao ◽  
...  
Keyword(s):  
Reference Values ◽  
Measurement Errors ◽  
Three Dimensional ◽  
Coordinate Measuring Machine ◽  
Cone Beam ◽  
Reference Systems ◽  
Linear Measurements ◽  
3D Photogrammetry ◽  
Measuring Machine ◽  
Linear Accuracy

Objectives: This study was aimed to investigate the accuracy of soft-tissue measurements obtained by two imaging modalities, three-dimensional (3D) photogrammetry and cone beam CT (CBCT) when confounded by influence factors (facial deformities and partitions). Methods: 60 wax facial models from facially deformed patients were captured by 3D photogrammetry and CBCT. 19 linear distances on each image were measured and juxtaposed to reference values attained via a coordinate-measuring machine (CMM) as the gold-standard. Paired t-tests were used to compare linear accuracy of the test and reference systems. The influence of deformities and partitions (created by dividing the face with three vertical and five horizontal lines) on the measurement errors were analyzed by independent sample t-test and one-way ANOVA. Results: Statistically significant differences were found between linear accuracy of the test and reference systems. The test values obtained by 3D photogrammetry were closer to the reference values than CBCT’s. 3D photogrammetry’s measurement errors were significantly higher in deformed areas, unlike CBCT’s. Both systems reported significantly lower errors within partitions 8 and 13 compared to other partitions; for CBCT, aside from partitions 8 and 13, the differences in the errors for partitions 6 and 10 were significant compared to partitions 8, 12, 13, 14. Conclusion: 3D photogrammetry showed a higher linear accuracy than CBCT in patients with facial deformities due to protuberances. Facial reconstruction by both test modalities was significantly influenced in different facial partitions, but facial deformities extensively affected the results from 3D photogrammetry.

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