Ispitivanje preciznosti radnih modela pomoću koordinatne merne mašine u stomatologiji

Background/Aim. Dental impressions present a negative imprint of intraoral tissues of a patient which is, by pouring in gypsum, transferred extraorally on the working cast. Casting an accurate and precise working cast presents the first and very important step, since each of the following stages contributes to the overall error of the production process, which can lead to inadequately fitting dental restorations. The aim of this study was to promote and test a new model and technique for in vitro evaluation of the dental impression accuracy, as well as to asses the dimensional stability of impression material depending on the material bulk, and its effect on the accuracy of working casts. Methods. Impressions were made by the monophasic technique using the experimental master model. Custom trays with spacing of 1, 2 and 3 mm were constructed by rapid prototyping. The overall of 10 impressions were made with each custom tray. Working casts were made with gypsum type IV. Measurement of working casts was done 24 h later using a coordinate measuring machine. Results. The obtained results show that the working casts of all the three custom trays were in most cases significantly different in the transversal and sagittal planes in relation to the master model. The height of abutments was mainly unaffected. The degree of convergence showed certain significance in all the three custom trays, most pronounced in the tray with 3 mm spacing. Conclusion. The impression material bulk of 1-3 mm could provide accurate working casts when using the monophasic impression technique. The increase of the distance between abutment teeth influences the accuracy of working casts depending on the material bulk.Uvod/Cilj. Otisak predstavlja negativ intraoralnih tkiva, čijim se izlivanjem u gipsu njihova morfologija prenosi ekstraoralno na budući radni model. Sa laboratorijskog aspekta izrade zubnih nadoknada, izlivanje tačnog i preciznog radnog modela predstavlja prvi i veoma bitan korak, pošto svaka sledeća faza doprinosi daljem povećanju greške tokom izrade, što za krajnji ishod može imati neodgovarajuću zubnu nadoknadu. Cilj istraživanja bio je da se ispitaju novi model i tehnika za in vitro procenu preciznosti zubnih otisaka, kao i da se odredi uticaj količine otisnog materijala na dimenzionu stabilnost otisaka i preciznost izrade radnih modela. Metode. Za uzimanje otisaka korišćena je monofazna tehnika otiskivanja. Individualne kašike sa međuprostorom od 1, 2 i 3 mm napravljene su aditivnom tehnologijom za brzu izradu prototipova. Sa svakom kašikom napravljeno je po 10 otisaka. Radni modeli izlivani su u gipsu tipa IV. Merenje radnih modela vršeno je nakon 24 sata na koordinatnoj mernoj mašini. Rezultati. Rezultati pokazuju da radni modeli napravljeni pomoću sve tri individulane kašike u transverzalnoj i sagitalnoj ravni značajno odstupaju od glavnog dela modela. Visina patrljaka je u većini slučajeva bila kao na glavnom modelu. Stepen konvergencije pokazao je određena odstupanja samo kod kašike sa međuprostorom od 3 mm. Zaključak. Monofazna tehnika otiskivanja i otisni materijal debljine od 1 do 3 mm obezbeđuju izradu preciznih radnih modela. Rastojanje između zubnih patrljaka utiče na preciznost izrade radnih modela u zavisnosti od količine otisnog materijala

Eksperimentalna analiza i MKE modeliranje vibracija reznog alata

Presented in this paper is a comparative analysis of vibrations, measured during machining process and modelled by FEM. Moreover, microscopic structure of chip cross section was analyzed in order to establish the frequency of lamellae generation and its influence on the total level of vibrations of the cutting tool. Based on the results thus obtained, a method was proposed which allows determination of tool wear degree through separation of reliable indicators from the high-frequency spectrum of the measured vibration signals. This investigation showed that the change of chip segmentation frequency significantly influences the output vibration signal within the high-frequency spectrum, and is a function of tool wear degree.U radu je dat usporedni pregled vibracija reznog alata izmjerenih u procesu obrade i modeliranih primjenom metode konačnih elemenata (MKE). Također, analizirana je mikroskopska strukture poprečnog presjeka odvojenih čestica sa ciljem utvrđivanja frekvencije stvaranja lamela i njihovog utjecaja na ukupnu razinu vibracija alata za obradu. Prikazom dobivenih rezultata postavljene su osnove za verifikaciju predložene metode određivanja stanja istrošenosti alata izdvajanjem pouzdanih pokazatelja iz visokofrekventnog dijela spektra signala izmjerenih vibracija. Provedeno istraživanje pokazalo je evidentan utjecaj promjene frekvencije segmentacije odvojenih čestica na odziv signala vibracija u visoko-frekventnom dijelu spektara, te ovisnost o promjeni stupnja istrošenosti reznog alata

Inteligentni robotski sistemi za ekstremno diverzifikovanu proizvodnju

U okviru ovog rada navode se rezultati sprovedenih istraživanja na četvorogodišnjem projektu TR35007 koji zajednički realizuju Mašinski fakultet Univerziteta u Beogradu, Fakultet tehničkih nauka Univerziteta u Novom Sadu i kompanija Ikarbus iz Beograda. Ovaj projekat finansijskih podržava Ministarstvo prosvete i nauke u okviru četovorogodišnjeg ciklusa istraživačkih projekata za tehnološki razvoj, od 2011. do 2014. godine. Prvo se navode istraživački okvir projekta, osnovni ciljevi koji postavljeni pred istraživački tim i organizacija projekta koja je izvedena po modelu radnih paketa. U drugom delu rada navode se osnovni rezultati ostvaranih u prvoj istraživačkoj godini, sa odgovarajućim opisom i osnovnim detaljima tehničke i organizacione prirode

Pre-Processing of Point-Data from Contact and Optical 3D Digitization Sensors

Contemporary 3D digitization systems employed by reverse engineering (RE) feature ever-growing scanning speeds with the ability to generate large quantity of points in a unit of time. Although advantageous for the quality and efficiency of RE modelling, the huge number of point datas can turn into a serious practical problem, later on, when the CAD model is generated. In addition, 3D digitization processes are very often plagued by measuring errors, which can be attributed to the very nature of measuring systems, various characteristics of the digitized objects and subjective errors by the operator, which also contribute to problems in the CAD model generation process. This paper presents an integral system for the pre-processing of point data, i.e., filtering, smoothing and reduction, based on a cross-sectional RE approach. In the course of the proposed system development, major emphasis was placed on the module for point data reduction, which was designed according to a novel approach with integrated deviation analysis and fuzzy logic reasoning. The developed system was verified through its application on three case studies, on point data from objects of versatile geometries obtained by contact and laser 3D digitization systems. The obtained results demonstrate the effectiveness of the system

IMPLEMENTATION OF MID IN SLOVAK REPUBLIC

This research is a part of ETIQUM Tempus Project which is focused on development of training courses in the field of quality management and metrology. The article covers the analyse of steps which were required for transposition EU Directive on measuring instrument (MID) into national legislation of Slovak republic. It covers not only information about implementation but also mandatory periodic verification after placing on the market as well

IMPLEMENTATION OF MDD IN SLOVAK REPUBLIC II

This research is part of Tempus ETIQUM Project which is financed by EU. This article covers the analyse of steps which were necessa ry for transposition and implementation of EU Directi ve on medical devices into the national legislation of the Slovak republic. It covers not only information about implementation but also mandatory periodic verification after placing the medical device with measuring function on the market as well

Comparative analysis of the results of measuring roundness

Coordinate measuring machines are devised for most complex measurements. Besides their dimension measuring abilities, the CNC operated machines can measure geometrical characteristics of form, such as straightness, roundness, cylindricity, etc. These are vital features in current times when control needs to submit very thorough reports not only on the form, but also on the geometrical features of the given workpiece. Yet the question arises: are these measuring data regarding roundness received from the CMM accurate and reliable enough for them to be exploited? In order to confirm this statement, the geometrical roundness characteristics are measured on three types of coordinate measuring machines, the results of which are analyzed from several aspects. The results have shown a special importance of specific measuring parameters and have shown to be independent of the type of measuring machines

MULTICRITERIA APPROACH FOR ASSESSMENT OF ENVIRONMENTAL QUALITY

Environment is important and inevitable element that has direct impact on life quality. Furthermore, environmental protection represents prerequisite for healthy and sustainable way of life. Environmental quality can be represented through specific indicators that can be identified, measured, analyzed, and assessed with adequate methods for assessment of environmental quality. Problem of insight in total environmental quality, caused by different, mutually incomparable, indicators of environmental load and difficult expression of overall environment quality, can be solved with multicriterial assessment. This paper presents appliance of multicriterial methods for analysis of indicators that represent environmental quality for several sites

Radojeviĉ D., Aggregation for quality management

Abstract: The problem relevant for quality management such as aggregation of many features into one representative is analyzed. Actually, in quality management practice, standard approaches to aggregation are often trivial and as a consequence- inadequate. In this paper, aggregation is treated as a logical and/or pseudo-logical operation that is important from many points of view such as adequacy and interpretations

Eksperimentalna analiza i MKE modeliranje vibracija reznog alata

Presented in this paper is a comparative analysis of vibrations, measured during machining process and modelled by FEM. Moreover, microscopic structure of chip cross section was analyzed in order to establish the frequency of lamellae generation and its influence on the total level of vibrations of the cutting tool. Based on the results thus obtained, a method was proposed which allows determination of tool wear degree through separation of reliable indicators from the high-frequency spectrum of the measured vibration signals. This investigation showed that the change of chip segmentation frequency significantly influences the output vibration signal within the high-frequency spectrum, and is a function of tool wear degree.U radu je dat usporedni pregled vibracija reznog alata izmjerenih u procesu obrade i modeliranih primjenom metode konačnih elemenata (MKE). Također, analizirana je mikroskopska strukture poprečnog presjeka odvojenih čestica sa ciljem utvrđivanja frekvencije stvaranja lamela i njihovog utjecaja na ukupnu razinu vibracija alata za obradu. Prikazom dobivenih rezultata postavljene su osnove za verifikaciju predložene metode određivanja stanja istrošenosti alata izdvajanjem pouzdanih pokazatelja iz visokofrekventnog dijela spektra signala izmjerenih vibracija. Provedeno istraživanje pokazalo je evidentan utjecaj promjene frekvencije segmentacije odvojenih čestica na odziv signala vibracija u visoko-frekventnom dijelu spektara, te ovisnost o promjeni stupnja istrošenosti reznog alata