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Item The Effect of Drag Finishing on Additively Manufactured Customized Dental Crowns(2025) Cosma, Cosmin; Melichar, Martin; Libu, Stelian; Popan, Alexandru; Contiu, Glad; Teusan, Cristina; Berce, Petru; Balc, NicolaeCobalt–chromium (CoCr) alloys are frequently used to produce customized dental applications such as crowns, bridges, or prostheses. These medical products have anatomical forms, and can be effectively manufactured using the laser-based powder bed fusion (PBF-LB/M) technique. A majordisadvantage of this approach is the extended time required to refine the resultant surface. The purpose of this research is to reduce the surface roughness of PBF-LB/M/CoCr dental crowns by adopting drag finishing (DF) technology. To evaluate the impact of this automatic post-processing, surface roughness measurements and geometrical investigations were undertaken. The microstructure was characterized using scanning electron microscopy (SEM), and the chemical composition was verified by energy-dispersive X-ray spectroscopy (EDAX). On outside surfaces, the DF post-processing decreased the initial surface roughness by 70–90%. The dental crown’s surface roughness value after DF post-processing was comparable to that of the basic form (cylinder). The lowest roughness was obtained with DF3 post-processing (Ra~0.60 μm). The inner surfaces were limitedly finished. The 3D surface texture showed that the DF method reduced the height of peaks, uniformizing the surfaces. CMM work compared the deviations between the virtual model and the printed samples before and after DF post-processing. This analysis revealed that dimensional deviations were reduced on the outside crown walls, ranging from +0.01 to +0.05 mm. The laser parameters and the heat treatment applied increased the hardness of CoCr crowns to 520 HV, but the proper DF conditions identified reduced the surface roughness and improved the accuracy.
Item Comprehensive Experimental Analysis of the Effect of Drilled Material on Torque Using Machine Learning Decision Trees(2025) Hnátík, Jan; Fulemová, Jaroslava; Sklenička, Josef; Gombár, Miroslav; Vagaská, Alena; Sýkora, Jindřich; Lukáš, AdamThis article deals with drilling, the most common and simultaneously most important traditional machining operation, and which is significantly influenced by the properties of the machined material itself. To fully understand this process, both from a theoretical and practical perspective, it is essential to examine the influence of technological and tool-related factors on its various parameters. Based on the evaluation of experimentally obtained data using advanced statistical methods and machine learning decision trees, we present a detailed analysis of the effects of technological factors (fn, vc) and tool-related factors (D, εr , α0, ωr) on variations in torque (Mc) during drilling of two types of engineering steels: carbon steel (C45) and case-hardening steel (16MnCr5). The experimental verification was conducted using CTS20D cemented carbide tools coated with a Triple Cr SHM layer. The analysis revealed a significant influence of the material on torque variation, accounting for a share of 1.430%. The experimental verification confirmed the theoretical assumption that the nominal tool diameter (D) has a key effect (53.552%) on torque variation. The revolution feed (fn) contributes 36.263%, while the tool’s point angle (εr) and helix angle (ωr) influence torque by 1.189% and 0.310%, respectively. No significant effect of cutting speed (vc) on torque variation was observed. However, subsequent machine learning analysis revealed the complexity of interdependencies between the input factors and the resulting torque.Item Research of Tribological Properties of 34CrNiMo6 Steel in the Production of a Newly Designed Self-Equalizing Thrust Bearing(2020) Urban, Marek; Monková, KatarínaThere are many cases when in large power equipment (such as a turbine or compressor) asymmetrically loading on bearings due to thermal deformations, production inaccuracies, or simple deflection of the shaft occurs. This asymmetrically loading means misalignment of rotor against stator in angle more than several tenths of a degree and it has an influence on a journal and thrust bearings. Over the last few years, thanks to increasingly precise manufacturing, solutions that can eliminate this phenomenon have been revealed. In the case of the thrust bearing, it is a system of very precise manufactured levers, which are in close contact each to other, so they have to be not only properly designed from the geometrical point of view but the important role plays a quality of the functional surfaces of these levers. The article deals with the surface treatment effect on tribological properties of 34CrNiMo6 steel used for the production of bearing levers, which are the critical parts of a newly developing self-equalizing thrust bearing. The samples with cylindrical and plate shapes were produced from 34CrNiMo6 steel as representatives of the most suitable geometries for contact surfaces. All samples were heat-treated. The surfaces of some samples were treated by electroless nickel plating or nitriding, some of the samples were treated by tumbling. Gradually, the surface roughness, microhardness, metallographic analysis and the influence of selected types of surface treatments on the wear for individual samples were evaluated within the research presented in the article. As the testing methods for evaluation of tribological properties were selected Pin-on-disc test and frequency tribological test. The results showed that the best tribological properties achieved samples treated by electroless nickel plating compared with the nitrided or only heat-treated samples.Item The Influence of the Amount of Technological Waste on the Performance Properties of Fibrous Polymer Composites(2024) Dobránsky, Jozef; Gombár, Miroslav; Fejko, PatrikThe objective of the experimental analysis was to assess the impact of the reuse of technological waste (recyclate) on the selected performance properties of the fibrous polymer composite used to produce components for the automotive industry by injection molding technology. Polyphthalamide (PPA), which belongs to a group of high-tech polymers, was chosen as the analyzed material. In accordance with the set goals, the rheological, mechanical, and structural properties of the material were evaluated using ANOVA analysis in the experimental part of the work, depending on the mass ratio of the recycled material added to the virgin material. The influence of the proportion of recycled material on the lifetime of moldings by the method of their exposure at an elevated temperature for a defined time was also assessed. During the research, it was found that at a concentration of up to 40 wt. % of recyclate, its mechanical properties do not change significantly. At a concentration of 50 wt. %, there is a rapid decrease in mechanical properties. In the long term, it can also be said that the addition of recyclate significantly affects the service life of the components. No significant changes in morphology were observed during the analysis of structural properties.Item Methodology of rotation of general surfaces(2024) Lehner, Radek; Valdman, Jan; Zídková, HelenaWhen parts are machined, especially on heavy machine tools, an accurate description of the rotations around the geometric axes is required. The work adds the concept of rotation around the machine and the workpiece axes. Both types of rotation in mechanics are related to internal and external rotations, which we describe in detail. We show how both types convert to each other and how conversion formulas are derived. The resulting conversions are formalized as functions in the C and MATLAB programming languages. The result of this mathematical description will be transferred to a new transformation cycle that can be used on machines as a standard.Item Analysis of the effect of pretreatment on the overall damage of the coating created by the cataphoretic coating(2024) Fejko, Patrik; Dobránsky, Jozef; Straka, Ľuboslav; Gombár, MiroslavAluminum and its alloys are essential in construction due to their lightweight nature and recyclability. To enhance durability, protection against corrosion is vital, with cataphoretic painting being particularly effective. This study evaluated the damage rate of cataphoresis coatings on AW 1050 H24 aluminum, focusing on the impact of different degreasing solutions. By analyzing temperature, concentration, and deposition time, the study found that concentrations above 5.25 % degrade surface quality due to aluminum dissolution, while temperatures between 37 °C and 50 °C are optimal. At higher temperatures, shorter deposition times improve quality, whereas longer times lead to defects.Item Determination of the brittleness of glass fibers on selected mechanical and rheological properties of the polymer composite(2024) Miščík, Stanislav; Dobránsky, Jozef; Gombár, Miroslav; Čep, RobertThe paper deals with the influence of the brittleness of glass fibers on the selected performance properties of the fibrous polymer composite. Understanding the fatigue behavior of fiber-reinforced plastics is desirable for exploiting their features in safe, durable, and reliable industrial components. Based on the proposed methodology, it is possible to assess the impact of material reuse on selected mechanical and rheological properties. To verify the methodology by experimental analysis, homopolymer PP reinforced with chemically grafted glass fiber (30 wt%) was selected. The proposed methodology was subsequently verified by experimental analysis and evaluated statistically. The morphology of the fracture surfaces was evaluated, and the fiber-polymer matrix adhesion was monitored at the interface of the fracture surfaces. Based on the measured and evaluated values and fracture surfaces, we can say that the brittleness of the fibers significantly affects the performance properties of the tested polymer composite.Item The effect of degreasing temperature on the thickness of the formed layer created by cataphoretic painting(2024) Peti, Damián; Dobránsky, Jozef; Zajac, Jozef; Gombár, MiroslavThe article investigates the impact of degreasing temperature in the degreasing mixture PRAGOLOD 57N on cataphoretic painting using design of experiments (DoE). Key technological factors such as degreasing deposition time, concentration, cataphoretic deposition time, and voltage are examined for their effect on the thickness of the formed anti-corrosion layer. Cataphoretic painting, an economical and eco-friendly method, is widely used for treating metal parts in automotive and engineering industries. The study involves testing 88 samples, with thickness measurements taken via Elcometer 456C according to the ISO standards and graphical analysis performed using statistical software to optimize the process.Item Evaluation of recycled and reused metal powders for DMLS 3D printing(2024) Svozilová, Simona; Zetková, Ivana; Marin, Juan Felipe Santa; Garay, Jesús Arturo TorresMetal powders for additive manufacturing are expensive and producing new ones from mined metals has a negative ecological impact. In this work, recycled and reused metal powders from MS1 steel for Direct Metal Laser Sintering (DMLS) 3D printing were evaluated in the laboratory. The powders were recycled by melting followed by gas atomizing. Virgin, recycled and reused metal powders were evaluated using Scanning-Electron Microscopy (SEM), Energy-Dispersive X-Ray Spectroscopy (EDS), X-Ray Diffraction (XRD), metallography analysis, microhardness measurements, Particle Size Distribution (PSD), shape factor by Digital Image Processing (DIP) and flowability testing. The results showed that the particle distribution was modified after recycling. Kurtosis analysis revealed a reduction from -0,64 for virgin powder to -1,29 for recycled powders. A positive skewness was obtained a consequently, smaller particles were found in recycled powder. The shape factor was also modified and changed from 1,57 for virgin powders to 1,28 for recycled powders. The microstructure also changed and austenite was found in recycled powders. The microhardness of recycled powder decreased by 39% compared to the virgin powder. Recycled powders did not flow using two different funnels to evaluate their flowability. The flowability of used powder was reduced from 4,3 s to 2,9 s.Item Experimental Analysis of Effect of Machined Material on Cutting Forces during Drilling(2024) Sklenička, Josef; Hnátík, Jan; Fulemová, Jaroslava; Gombár, Miroslav; Vagaská, Alena; Jirásko, AnetaCurrent research studies devoted to cutting forces in drilling are oriented toward predictive model development, however, in the case of mechanistic models, the material effect on the drilling process itself is mostly not considered. This research study aims to experimentally analyze how the machined material affects the feed force (Ff ) during drilling, alongside developing predictive mathematical–statistical models to understand the main effects and interactions of the considered technological and tool factors on Ff. By conducting experiments involving six factors (feed, cutting speed, drill diameter, point angle, lip relief angle, and helix angle) at five levels, the drilling processof stainless steel AISI1045 and case-hardened steel 16MnCr5 is executed to validate the numerical accuracy of the established prediction models (AdjR = 99.600% for C45 and AdjR = 97.912% for 16MnCr5). The statistical evaluation (ANOVA, RSM, and Lack of Fit) of the data proves that the drilled material affects the Ff value at the level of 17.600% (p < 0.000). The effect of feed represents 44.867% in C45 and 34.087% in 16MnCr5; the cutting speed is significant when machining C45 steel only (9.109%). When machining 16MnCr5 compared to C45 steel, the influence of the point angle (liprelief angle) is lower by 49.198% (by 22.509%). The effect of the helix angle is 163.060% higher when machining 16MnCr5.Item Influence of Laser Treatment of Ti6Al4V on the Behavior of Biological Cells(2024) Syrovátka, Šimon; Kožmín, Pavel; Holešovský, František; Šorm, MartinThis article explores the enhancement of material surface properties of Ti6Al4V, potentially applicable to dental implants, through ultra-short pulse laser systems. This study investigates potential connections between surface wettability and biocompatibility, addressing the challenge of improving variability in material properties with specific laser treatment. Several designed microstructures were manufactured using a picosecond laser system. After that, the wettability of these structures was measured using the sessile drop method. The basic behavior and growth activity of biological cells (MG-63 cell line) on treated surfaces were also analyzed. While the conducted tests did not conclusively establish correlations between wettability and biocompatibility, the results indicated that laser treatment of Ti6Al4V could effectively enlarge the active surface to better biological cell colonization and adhesion and provide a focused moving orientation. This outcome suggests the potential application of laser treatment in producing special dental implants to mitigate the issues during and following implantation.Item Inverse dependence of heat accumulation on pulse duration in laser surface processing with ultrashort pulses(Elsevier, 2023) Moskal, Denys; Martan, Jiří; Honner, Milan; Ballardin Beltrami, Carlos; Kleefoot, Max Jonathan; Lang, VladislavDélka laserového pulzu je jedním z důležitých parametrů, který je schopen dramaticky změnit účinnost ablace. Kratší doba trvání laserového pulzu vede k hlubšímu transportu absorbované energie v podpovrchových vrstvách materiálu. Ultrarychlé a nerovnovážné procesy dokážou pozoruhodně ovlivnit zbytkovou energii, která se po ablaci akumuluje v hlubších podpovrchových vrstvách. Na druhé straně nežádoucí vysoká akumulace tepla vede k přehřívání materiálu s povrchovou oxidací, vznikem kapalné fáze a v důsledku toho k nízké kvalitě zpracování. V tomto článku byl poprvé experimentálně hodnocen vliv délky laserového pulsu na hodnotu akumulace tepla. Akumulace tepla byla měřena vysoce citlivým rychlým infračerveným detektorem. Výsledky byly prezentovány v porovnání s analýzou struktury povrchu, rychlostí ablace materiálu a optickou odrazivostí. Byla zjištěna neočekávaná inverzní závislost akumulace tepla na délce laserového pulzu. Optimální trvání laserového pulsu blízko 1 ps odpovídá maximální hodnotě akumulace tepla a také nejvyšší účinnosti ablace na rozdíl od delších laserových pulsů. Stejná optimální hodnota trvání pulsu byla detekována pro nízkofrekvenční (250 kHz) a pro vysokofrekvenční (1 MHz) režimy laserového zpracování povrchu. Maximální hodnota akumulace tepla byla očekávána při nejdelších laserových pulzech. Výsledky jsou diskutovány z pohledu dvouteplotního modelu.
Item Ergonomie jako významná součást age managementu(ERC, 2022) Pokorná, VáclavaDemografický vývoj populace v Evropě naznačuje trend, který předpokládá, že počet lidí ve věku nad 60 let se bude v příštích desetiletích ve světě zvyšovat asi o 2 miliony ročně. Tato prognóza poukazuje na situaci, kdy by se mohl počet obyvatel v produktivním věku snižovat a tím začne zároveň klesat počet zaměstnanců. Problém stárnoucí pracovní síly je celosvětová výzva k zamyšlení a je nutné se začít včas zabývat nastavením pracovních podmínek pro starší zaměstnance. Především nacházením možností jejich uplatnění v profesích, které to umožňují. Posláním ergonomie, jako samostatné vědecké disciplíny, je analyzovat pracovní podmínky pro člověka v souladu s jeho fyzickou a psychickou výkonností. Ergonomie se tím stává významnou součástí age managementu, jehož základní filozofií je nutnost nastavení takových podmínek pro práci starších zaměstnanců, aby požadavky byly v souladu s jejich schopnostmi. V článku je představen základní koncept ergonomického auditu pracoviště jako nezbytná součást pro možný výběr sdíleného místa v dané organizaciItem Investigation on the parameter dependency of the perforation process of graphite based lithium-ion battery electrodes using ultrashort laser pulses(Laser Institute of America, 2022) Kleefoot, Max-Jonathan; Sandherr, Jens; Sailer, Marc; Nester, Sara; Martan, Jiří; Knoblauch, Volker; Kumkar, Malte; Riegel, HaraldPerforation of lithium-ion battery electrodes has recently become an increasing interest in science and industry. Perforated electrodes have shown improved electrochemical properties compared to conventional, nonperforated electrodes. It has been demonstrated that through perforation, the fast-charging capability and the lifetime of these batteries can be significantly improved. The electrodes for lithium-ion batteries consist of a copper foil onto which the electrode material is applied as a porous layer. This layer is mainly composed of active material particles, which are bound together by a binder phase. Here, synthetic graphite was used as an active material. Up to now, it has been shown that an advantageous and precise perforation geometry can be produced by ultrashort laser pulse ablation. Since the ablation volumes during perforation of the porous electrode material with ultrashort laser pulses are unusually high compared to solids, this work investigates the parameter dependency on the ablation mechanisms in detail. For this purpose, in particular, single-pulse ablation was investigated with respect to the ablation thresholds at different pulse durations. The pulse durations were varied over a large range from 400 fs to 20 ps. By varying the number of pulses per perforation up to 50 and the single-pulse energy up to 45 μJ, it could be shown that a homogeneous ablation down to the conductor foil through the 63 μm thick active material layer can be achieved.Item Design of a risk register for an accredited laboratory according to the ISO/IEC 17025(MAGNANIMITAS Assn., 2021) Bícová, Kateřina; Jirásko, AnetaHlavním zaměřením tohoto příspěvku jsou možnosti řízení rizik a zavedení metodiky pro práci s riziky v akreditované laboratoři dle ISO/IEC 17025. Snahou je plnit dostatečně všechny požadavky standardu a nastavit proces posuzování rizik tak, aby byl pro akreditovanou laboratoř srozumitelný a snadno použitelný pro následné analýzy. Přínosem tohoto příspěvku je poskytnutí komplexního pohledu na danou problematiku a závěry mohou sloužit jako zdroj informací pro laboratoře, které budou podstupovat certifikaci zavedeného systému řízení kvalityItem Comparative Study of Chip Formation in Orthogonal and Oblique Slow-Rate Machining of EN 16MnCr5 Steel(MDPI, 2019) Monková, Katarína; Monka, Peter Pavol; Sekeraková, Adriana; Hruzik, Lumír; Bureček, Adam; Urban, MarekItem VERIFICATION OF NORMALITY AS A BASIC PRECONDITION FOR THE USE OF QUALITY MANAGEMENT TOOLS(MAGNANIMITAS Assn., 2021) Bícová, Kateřina; Sklenička, JosefCílem tohoto příspěvku je představit možnosti, jak ověřit předpoklad normálního rozdělení dat pro další statistické zpracování, a to bez nutnosti studia nepřeberného množství metod a hypotéz o statistickém zpracování dat. Hlavní myšlenkou je to, aby například podniky v oblasti automobilového průmyslu, kde standardy jako IATF 16949 vyžadují 100% kontrolu a využívání statistických nástrojů pro monitorování procesů, měly snadný návod jak ověřit relevantní vstupní data pro další statistické zpracování. Normální rozdělení dat je jedním z nejčastějších rozdělení, které data mají. A zároveň je nejvhodnějším pro statistické nástroje, neboť lze u těch to dat predikovat, že hodnocený proces se bude za stejných vstupních podmínek chovat stejně. Bez tohoto ověření by další zpracování dat nemělo dostatečnou vypovídací schopnost o sledovaném parametruItem Základní přístup k otázkám bezpečnosti a ergonomie při projektování kolaborativních pracovišť(Výzkumný ústav bezpečnosti práce, 2020) Pokorná, VáclavaSoučasný svět průmyslové výroby lze definovat jako období růstu a výrazných změn od tradičních technologií k naprosto novým řešením a převratným změnám. Jedním z těchto trendů je zavádění kolaborativních robotů do výroby. Změny, které jsou spojeny s nákupem automatizační techniky a robotů jsou nejen finančně náročné, ale vyžadují především nový přístup při řešení a projektování pracovišť, který úzce souvisí s vybranými principy ergonomických zásad. Ty získávají v současném světě využívání moderních technologií a rozvoji automatizace nový význam. V tomto pojetí jsou více propojeni s požadavky na nutnou úroveň bezpečnosti. Standard ISO 9241-210:2010 představuje návod pro uplatnění nového přístupu (HCD) pro designové řešení produktu. Tento dokument je nezbytným doplňkem stávajících norem pro návrh společných pracovišť člověk-robot a v současnosti není mezi projektanty příliš známý. Antropocentrický přístup při projektování takových pracovišť je založen na myšlence, že člověk má oproti robotu určitá omezení a tato omezení mohou být hlavní příčinou chyb a selhání, související s prací operátora. Toto je důvod, proč by mělo být osvojení ergonomických zásad, rovněž tak znalost ISO 9241-210, součástí projektových prací při návrhu kolaborativních pracovišťItem Influence of the number of points on the contact scanning process during measuring on the CMM(Magnanimitas, 2020) Kubátová, Dana; Milsimerová, Aneta; Kutlwašer, JanItem Grinding of maraging steel 1.2709 with SiC grinding wheels and effect of grinding conditions on the surface roughness and wear of the wheels(J. E. Purkyne University in Usti nad Labem, 2020) Farský, Jindřich; Bakša, Tomáš; Zetek, MiroslavBroušení je jednou ze základních dokončovacích operací, kterou lze použít u dílů z různých materiálů, kde je vyžadována vysoká kvalita a přesnost povrchu. Jedním z těchto materiálů je vysokopevnostní ocel 1.2709, která se používá zkušební vzorky pro zkoušení tahem. V tomto případě je velmi důležité dosáhnout dobré kvality povrchu. Opotřebení brusného kotouče je nejlépe vyjádřen hodnotou G-ratio, která udává, zda jsou parametry broušení zvoleny správně. Tento článek se zabývá vlivem podmínek pro broušení nástrojové oceli Vaco 180 na 5osé brusce. Experiment byl navržen s cílem zjistit vliv změn řezné rychlosti, hloubky řezu a použití dvou brusných kotoučích. Na konci tohoto článku je provedeno shrnutí a porovnání výsledků experimentu
