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1

An approach to an intelligent scanning of the machine tool workspace

Marchewka Lukasz, Grudzinski Marek

Journal of Machine Engineering

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2021

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Vol. 21, No. 2

60--74

EN

Modern 3D scanners can measure the geometry with high accuracy and within a short time. In turn, currently produced CNC machine tools allow for very accurate manufacturing; however, processes beyond the machining cycle remain time-consuming. This paper presents the idea and experimental tests of the scanning system in the CNC machine, which allows to speed up on-machine measurements, align clouds of 3D data points with an accuracy close to that of the machine itself, and finally set the workpiece coordinate system for machining. This modern approach is in line with Industry 4.0, combining the terms of data processing, machine vision, manufacturing automation, and human-machine interfaces. The future implementation of the proposed system as an interchangeable tool will allow performing autonomous measurements, inspection, and supervision of the workspace, without engaging the machine operator. The system calibration and experimental results using the industrial 3D scanner and CNC machine are described.

2

A review on enabling technologies for resilient and traceable on-machine measurements

Dahlem Philipp, Emonts Dominik, Sanders Mark P., Schmitt Robert H.

Journal of Machine Engineering

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2020

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Vol. 20, No. 2

5--17

EN

On-Machine Measurements are a key factor for shorter closed quality control loops in industrial manufacturing. Especially for the production of large components, they promote the first-time-right approach, which is highly desirable, due to small quantities and steep value chains. In contrast to measurement rooms for CMMs, the production environment conditions are unregulated and impact multiple factors along the on-machine measurement metrological chain. As presented as a keynote speech at the XXXI CIRP Sponsored Conference on Supervising and Diagnostics of Machining Systems “MANUFACTURING ACTIVE IMPROVEMEN” by Professor Dr. Robert H. Schmitt, this article reviews current research and ideas regarding on-machine measurements. The authors collect necessary process data with the help of new technologies in the course of digitalization and thus propose a holistic model for systematic error compensation and measurement uncertainty prediction. For assessing the machine’s volumetric accuracy under thermal loads, the authors develop a novel modelling approach, which determines transient geometric errors by abstracting structural parts as spline curve with typical deformation modes. To address the workpiece’s influence on the measurement process, a data-driven framework, fusing real-time sensor-data with the virtual component, is used to model and predict transient thermo-mechanical workpiece states. For dissemination, the authors continue working on ISO standardization and, as subjects of future research, explore new paths in terms of data-driven modelling approaches, using physical abstractions coupled with machine learning and live process data.

3

Compensation of systematic errors of damaged probe for on-machine measurement

Wozniak A., Jankowski M.

Journal of Machine Engineering

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2018

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Vol. 18, No. 1

88--94

EN

Spatial characteristic of triggering radius of the damaged probe for the CNC machine tools has been presented. In such case a clear distortion of the probe performance characteristic and a significant increase in probe errors have been observed. Then, to such a damaged probe, a variable speed correction method of systematic errors was used. By setting proper measurement speeds, varying for different measurement directions, errors of the probe can be significantly reduced.

4

Właściwości metrologiczne sond stosowanych w obrabiarkach CNC

Jankowski M., Woźniak A.

Mechanik

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2016

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R. 89, nr 10

1338--1339

PL

Sondy stykowe do obrabiarek CNC są powszechnie stosowane do ustawiania przedmiotu i do jego kontroli wymiarowej. W związku z tym ich dokładność bezpośrednio wpływa na dokładność produkowanych części. W artykule zaprezentowano właściwości metrologiczne wybranych sond ze szczególnym uwzględnieniem ich niestabilności promienia przełączania.

EN

Probes for CNC machine tools are widely used to setting up a workpiece and to measure its dimensions. That’s why their accuracy directly influences quality of produced parts. In the paper, metrological features, especially triggering radius variation, of exemplary probes are presented.

5

Lokalne metody obliczania krzywych offset

Kawalec A., Magdziak M.

Pomiary Automatyka Kontrola

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2012

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R. 58, nr 1

130-132

PL

W artykule przedstawiono i porównano wybrane metody obliczania krzywych offset. Metody te mogą mieć zastosowanie do korekcji promienia końcówki trzpienia głowicy pomiarowej w trakcie pomiaru powierzchni swobodnych na obrabiarce sterowanej numerycznie. W ramach pracy przeprowadzono badania numeryczne oraz doświadczalne. Badania symulacyjne wykonano poprzez zastosowanie krzywych analitycznych reprezentujących zaobserwowane punkty pomiarowe. Z kolei badania ekspery-mentalne zrealizowano z użyciem współrzędnościowej maszyny pomiarowej ACCURA II wyposażonej w głowicę pomiarową VAST XT i oprogramowanie Calypso.

EN

In this paper there are presented and compared various selected methods of computing offset curves. They may be used for correction of the radius of a measurement tip during measurements of free-form surfaces on a CNC machine tool directly during the manufacturing process. In order to measure free-form surfaces during in-process measurements, CAD/CAI software can be used. In the first part of the first section the disadvantages of using such programs are reviewed. One of them concerns the process of calculation of corrected points according to nominal normal vectors at measurement points. The second part of the first section shows the possible solution of this problem by using the global method of the offset curve calculation. Unfortunately, this method can be used for such measurement surfaces which are characterized by small curvature. In the second section of this paper two new algorithms for generation of corrected measurement points are presented. Both of them are based on Bézier curves. In contrast to the global method, they are local ones and can be used especially for some parts of measurement surfaces which are characterized by big curvature. The following two sections concern both numerical and experimental investigations. In the first case some methods of computing offset curves, including those presented in the second section, are compared. Comparisons are made on the basis of some analytic curves representing the sequence of the observed measurement points for which the corrected points are calculated. In the second case the results of application of the proposed local methods for computing offset curves are compared with the results of experimental investigations concerning measurements of free-form surfaces made on the CMM ACCURA II equipped with the measurement head VAST XT and the associated software Calypso.

6

Measurement of free-form surfaces on CNC milling machine considering tool wear and small changes of its working length and offset radius

Kawalec A., Magdziak M., Cena I.

Advances in Manufacturing Science and Technology

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2011

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Vol. 35, nr 1

25-40

EN

This paper contains a survey of the selected strategies of measurements concerning free-form surfaces which may be used during in-process measurements of a workpiece on a CNC milling machine. Additionally, a supplement to conventional strategy of measurements of free-form surfaces directly on CNC machine tool is proposed, considering such variable factors as the real working length and real working radius of applied milling cutter as well as its wear. Results of experimental and numerical investigations are presented which show how tool wear and small changes of real working length and real working radius of applied milling cutter influence the shape and accuracy of machining a workpiece containing some free-form surfaces.

PL

W artykule przedstawiono przegląd wybranych strategii pomiaru powierzchni swobodnych, które mogą mieć zastosowanie w trakcie pomiaru przedmiotu na obrabiarce sterowanej numerycznie. Dodatkowo zaproponowano uzupełnienie strategii pomiaru realizowanego bezpośrednio w warunkach produkcyjnych o czynniki wynikające ze zmiennej długości narzędzia skrawającego i rzeczywistej wartości jego promienia, a także zużycia narzędzia w trakcie procesu obróbki. Przedstawiono wyniki badań doświadczalnych, numerycznych wizualizujących wpływ zmiany długości i promienia narzędzia oraz jego zużycia na postać geometryczną wybranych powierzchni swobodnych.

7

An influence of the number of measurement points on the accuracy of measurements of free-form surfaces on CNC machine tool

Kawalec A., Magdziak M.

Advances in Manufacturing Science and Technology

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2011

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Vol. 35, nr 2

17-27

EN

In the paper an influence of the number of measurement points on the accuracy of measurements of free-form surfaces on CNC machine tool is presented. There are described several numerical investigations made with selected examples of curves. The errors associated both with machining and making measurements are considered. In the investigations an algorithm for computing offset curve is used which can be applied during the measurements of free-form surfaces on a CNC machine tool. Additionally, formulas are given for converting cubic curves from Bézier to B-Spline representation. The developed formulas differ from the ones described in references and allow to more conveniently compute the coordinates of consecutive points on considered curves. They are an integral part of both method and algorithm used in the investigations described in the paper.

PL

W artykule omówiono ocenę wpływu liczby punktów pomiarowych na dokładność krzywej swobodnej. Prowadzono obliczenia numeryczne dla wybranych przykładów krzywych. Uwzględniono błędy procesu obróbki i pomiaru powierzchni krzywoliniowych. Stosowano algorytm obliczania krzywej offset, mający zastosowanie w trakcie pomiaru powierzchni swobodnych na obrabiarce sterowanej numerycznie. Przedstawiono sposób przeliczania krzywych Bézier'a 3. stopnia, które są integralną częścią algorytmu używanego w badaniach, na krzywe B-Spline 3. stopnia.

8

Porównanie wybranych metod optymalizacji na przykładzie zadania pomiarowego we współrzędnościowej technice pomiarowej

Kawalec A., Magdziak M.

Pomiary Automatyka Kontrola

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2010

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R. 56, nr 8

938-941

PL

W artykule przedstawiono porównanie wybranych metod optymalizacji na przykładzie zadania pomiarowego we współrzędnościowej technice pomiarowej, które polega na obliczeniu współrzędnych punktu środka i wartości promienia okręgu dopasowanego metodą najmniejszych kwadratów do grupy punktów pomiarowych. Zastosowanie metody najmniejszych kwadratów wynika z rodzaju wykorzystanego elementu skojarzone-go we współrzędnościowej technice pomiarowej. Punkty pomiarowe są wynikiem pomiaru na obrabiarce sterowanej numerycznie wyposażonej w głowicę pomiarową.

EN

The comparison of selected methods of optimization on the example of some measurement task in coordinate measurement technique is presented in the paper. The task consists of the computation of coordinates of the center and radius of a circle approximating some set of measured points using least squares method. The application of the method follows an approach used in conventional analysis of an associated element in coordinate measurement technique. In the paper both the numerical and experimental investigations were conducted. At the stage of simulation, within the three fundamental conjugate gradients methods (Fletcher-Reeves, Polak-Ribiére-Polyak and Hestenes-Stiefel), the best results were obtained using the Polak-Ribiére-Polyak method based on the number of iterations made. The aim of experimental investigations was the comparison of the measurement uncertainty components resulting from the repeatabil-ity of applied measurement hardware, in the case of using the coordinate measuring machine VISTA and CNC machine tool DMU 80 P duoBLOCK equipped with SINUMERIK 840D control system and MP700 measuring probe. Investigations were performed basing on measurements of the standard ring for different numbers of measurement points. The measured feature was the diameter of applied standard ring. The Polak-Ribiére-Polyak optimization method was chosen for the analysis of measurement data. Measure-ments made for various numbers of measurement points allowed to determine the minimum limiting number of points. Big dispersion of obtained results appeared for the number of points below the limit. For the number of points above the limit the determination of diameter becomes inefficient.

9

Automatic on-machine measurement of complex high-precision parts

Zeleny J., Janda M.

Inżynieria Maszyn

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2008

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R. 13, z. 3/4

83-90

EN

Milling spindle with inserted 3D tensometric touch probe were applied for on-machine inspection of highly precise parts produced on three- and five-axis milling machines equipped with linear motors and direct rotary drives. New methods of CNC control of angular NC axes during measurement were developed for parts containing hardly accessible surfaces. In-process calibration of multi-directional accuracy of probes has resulted in submicron sensitivity and highest absolute accuracy of on-machine measurements.