Maintenance Strategies to Reduce Downtime Due to Machine Positional Errors

Manufacturing strives to reduce waste and increase Overall Equipment Effectiveness (OEE). When managing machine tool maintenance a manufacturer must apply an appropriate decision technique in order to reveal hidden costs associated with production losses, reduce equipment downtime competently and similarly identify the machines’ performance. Total productive maintenance (TPM) is a maintenance program that involves concepts for maintaining plant and equipment effectively. OEE is a powerful metric of manufacturing performance incorporating measures of the utilisation, yield and efficiency of a given process, machine or manufacturing line. It supports TPM initiatives by accurately tracking progress towards achieving “perfect production.” This paper presents a review of maintenance management methodologies and their application to positional error calibration decision-making. The purpose of this review is to evaluate the contribution of maintenance strategies, in particular TPM, towards improving manufacturing performance, and how they could be applied to reduce downtime due to inaccuracy of the machine. This is to find a balance between predictive calibration, on-machine checking and lost production due to inaccuracy. This work redefines the role of maintenance management techniques and develops a framework to support the process of implementing a predictive calibration program as a prime method to supporting the change of philosophy for machine tool calibration decision making. Keywords—maintenance strategies, down time, OEE, TPM, decision making, predictive calibration

Electronic properties of antidot lattices fabricated by atomic force lithography

Antidot lattices were fabricated by atomic force lithography using local oxidation. High quality finite 20 x20 lattices are demonstrated with periods of 300 nm. The low temperature magnetoresistance shows well developed commensurability oscillations as well as a quenching of the Hall effect around zero magnetic field. In addition, we find B periodic oscillations superimposed on the classical commensurability peaks at temperatures as high as 1.7 K. These observations indicate the high electronic quality of our samples.Comment: Appl. Phys. Lett., in prin

Результаты многолетних измерений на линейном базисе Коштице

Currently, electronic total stations based on the principles of laser long-range distance measurement are used for collecting geospatial information. As time goes, in the process of using the electronic total stations, their technical parameters vary, necessitating periodic calibration of the instruments. Calibration of the long-range distance measurement laser component of the electronic total stations is carried out at specialized baselines and consists in testing the constant component of an electronic total station, determining the scale error and determining the cyclic error. In the territory of the Czech Republic, two geodetic baselines are operated, the National Calibration Baseline Hvězda and Koštice. Koštice is the Czech State Long Distances Measuring Standard, where electronic total stations are calibrated. From 2017 to 2020, about 600 electronic total stations by different manufacturers Leica Geosystems, Trimble, Topcon, Sokkia, Nikon, Pentax, South and Geomax were calibrated. The total number of measurements performed under the program in all combinations has equaled about 40000. In this paper, results of analysis many years’ measurements performed at the geodetic baseline Koštice from 2017 to 2020 with electronic total stations manufactured by Leica Geosystems are presented. In total, 9186 measurements between the baseline sections 1–2, 1–3, 1–4, 1–5, 1–6, 1–7 and 1–8 have been analyzed. For each section, measurements have been detected which did not pass the Grubbs test criterion (the Smirnov – Grubbs test). Altogether, 261 outliers have been detected, totaling 3 % of the total number of measurements. After excluding the detected outliers with the algorithm of the parametric version of least squares optimization, the length of each section of the baseline was found, and the accuracy of the results obtained was evaluated. The calculated values of the length of the baseline sections are in generally good agreement with the results of the measurements performed at the geodetic baseline Koštice by the specialists from the laboratory of the Bundeswehr University in Munich (Germany) and the results of similar measurements conducted at the same baseline by the specialists from the Research Institute of Geodesy, Topography and Cartography (Czech Republic). For section 1–5, based on the results of both verifications, differences have been obtained exceeding the permissible values of the accuracy of determining baseline characteristics. This may be related to the fact that there are displacements of certain pillars, which mainly have a periodic character and depend on the season. To allow more specific assumptions regarding instability of certain pillars, it is recommended to verify the lengths of the baseline sections once in three months, according to the program in all combinations, which will allow comparison of the values of the confidence limits of the baseline section lengths and putting forward hypotheses regarding variations in the position of individual centers, so that the deviations revealed should be included into the residual uncertainty of length measurement.В настоящее время для сбора геопространственной информации широко используются электронные тахеометры, основанные на принципах лазерной дальнометрии. В процессе эксплуатации изменяются их технические параметры и возникает необходимость периодической калибровки. Она осуществляется на специальных линейных базисах и состоит в поверке постоянной cоставляющей электронного тахеометра, определении ошибки масштаба и циклической ошибки. На территории Чешской Республики действуют два линейных базиса – Гвезда и Коштице. Последний является национальным государственным эталоном длины дальних расстояний, на котором осуществляются поверки электронных тахеометров. С 2017 по 2020 год здесь выполнена калибровка порядка 600 тахеометров различных фирм (Leica Geosystems, Trimble, Topcon, Sokkia, Nikon, Pentax, South и Geomax), общее количество измерений во всех комбинациях около 40000. В статье представлены результаты анализа многолетних измерений, проведенных на линейном базисе Коштице тахеометрами фирмы Leica Geosystems. Исследованы 9186 измерений между секциями базиса 1–2, 1–3, 1–4, 1–5, 1–6, 1–7 и 1–8. По каждой секции выявлялись измерения, которые не прошли заданный критерий Смирнова – Граббса, обнаружен 261 выброс, что составляет 3 % всех измерений. После исключения выбросов с помощью алгоритма параметрической версии МНК-оптимизации определена длина каждой секции базиса и выполнена оценка точности полученных результатов. Вычисленные значения длин секций в целом хорошо согласуются с результатами измерений, проведенных на линейном базисе Коштице Лабораторией геодезии Военного университета Мюнхена (Германия) и Научно-исследовательского института геодезии, топографии и картографии. По секции 1–5 в ходе обоих сравнений получены разности, превышающие допустимые значения точности определения характеристик базиса. Это может быть связано с тем, что по отдельным пунктам наблюдаются смещения, которые носят в основном периодический характер и зависят от времени года. Для более конкретных предположений о нестабильности отдельных пунктов рекомендуется проводить поверку длин секций базиса один раз в три месяца по программе во всех комбинациях, что позволит сопоставлять значения доверительных границ длин секций базиса и выдвигать гипотезы о колебаниях положения отдельных центров. В дальнейшем это позволит включать полученные смещения в остаточную неопределенность измерения длины.    

Development of a Submillimetric GNSS-Based Distance Meter for Length Metrology

[EN] Absolute distance determination in the open air with an uncertainty of a few tenths of a millimetre is increasingly required in many applications that involve high precision geodetic metrology. No matter the technique used to measure, the resulting distances must be proven consistent with the unit of length (SI-metre) as realized in the outdoor facilities traditionally used in length metrology, which are also known as calibration baselines of reference. The current calibration baselines of reference have distances in the range of 10 to 1000 m, but at present there is no solution on the market to provide distances with submillimetric precision in that range. Consequently, new techniques such as multi-wave interferometry, two-wave laser telemeters or laser trackers are being developed. A possible alternative to those sophisticated and expensive techniques is the use of widely used Global Navigation Satellite Systems (GNSS) in order to provide a GNSS-Based Distance Meter (GBDM). The use of a GBDM as a potential technique for length metrology has been thoroughly analysed in several European research projects by using the state-of-the-art geodetic software, such as Bernese 5.2, but no definite conclusions have been drawn and some metrological questions are considered still open. In this paper, we describe a dedicated approach to build up a submillimetric GBDM able to be applied in the current calibration baselines of reference, as well as possible methods to cope with the multipath error of the GNSS signals which is the major limitation for the practical uptaking of the technique in metrology. The accuracy of the proposed approach has been tested following the length metrology standards in four experiments carried out in the Universitat Politecnica de Valencia (UPV). The results demonstrate that the proposed GBDM can provide an accuracy of a few tenths of a millimetre in the current calibration baselines of referenceThis work was partly performed within the 18SIB01 GeoMetre project of the European Metrology Programme for Innovation and Research (EMPIR). This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. This research was also partly funded by the Spanish Ministry of Education, Culture and Sports (PRX17/00371).García-Asenjo Villamayor, L.; Baselga Moreno, S.; Atkins, C.; Garrigues Talens, P. (2021). Development of a Submillimetric GNSS-Based Distance Meter for Length Metrology. Sensors. 21(4):1-21. https://doi.org/10.3390/s2104114512121