Articles (KKS)

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http://hdl.handle.net/11025/30154

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Showing 1 - 20 out of 47 results

Development and Production of a Children’s Upper-Limb Cycling Adapter Using 3D Printing
(2024) Kopová, Barbora; Bakeš, Martin; Čížek, Martin; Horký, Adam; Dvořák, Josef; Ráž, Karel; Chval, Zdeněk
The research described in this study focuses on the development of an innovative upper-limb adapter for young children aged 1–3 years who have congenital upper-limb defects. The objective was to create a functional and affordable solution that allows children to engage more safely and actively in physical activities such as cycling. The adapter was designed within the DESIGN+ project at the University of West Bohemia in Pilsen in collaboration with the German company Ottobock. The development included a detailed analysis of hand movements during cycling, modelling using CAD software (NX 1888), prototype manufacturing through 3D printing, and subsequent testing. The result is an adapter that allows 360° rotation around the arm axis, provides natural hand movement while turning, and is made of soft material to enhance safety. Despite initial challenges and necessary prototype adjustments, a functional and reliable design was achieved. This adapter will contribute to improving the quality of life for children with upper-limb disabilities, supporting their coordination, strength, and confidence in daily activities. © 2024 by the authors.
Accuracy and Powder Removal Limits in Multi Jet Fusion 3D Printing
(2025) Ráž, Karel; Chval, Zdeněk; Hofrichterová, Petra
Multi Jet Fusion (MJF) is a leading technology for producing functional polymer parts. However, it still faces challenges with dimensional accuracy and removing unfused powder from complex internal geometries. First, dimensional accuracy was mapped by producing 45 identical PA12 specimens on an HP MJF 4200 printer in a 5 × 9 layout across five vertical layers. The analysis revealed a consistent pattern: parts located in the central positions of the build volume exhibited the poorest accuracy, while those near the perimeter were the most precise, regardless of their vertical height. This spatial variation is attributed to non-uniform thermal control from the printer’s adaptive lamp–thermal camera system. Second, the limits of powder removal from closed body-centered cubic (BCC) lattice structures were quantified. Using sandblasting and X-ray inspection, a strong inverse relationship was found between a lattice’s relative density and the maximum thickness that could be thoroughly cleaned of powder. For example, low-density structures (ρ = 0.07) could be cleaned up to five layers deep, whereas high-density structures (ρ = 0.39–0.47) were limited to only 1.5–1.7 layers. These findings offer actionable guidelines for optimizing part placement and designing internal lattice structures for MJF technology. The key findings are the spatial variation in dimensional accuracy in MJF printing, where the central parts are the least accurate and perimeter parts are the most precise, and the inverse relationship between a lattice’s relative density (ρ) and cleanable thickness. Specifically, low-density structures (ρ = 0.07) could be thoroughly cleaned up to five layers, while high-density ones (ρ = 0.39–0.47) were limited to approximately 1.5–1.7 layers. The layer thickness was a pre-designed parameter (2, 3, 4, and 5 layers), and powder removal was supported by using automated sandblasting followed by verification via industrial X-ray imaging.
Surface Treatment and Analysis of 3D-Printed Plastic Molds for Prototype and Small-Series Injection Molding
(2025) Ráž, Karel; Chval, Zdeněk; Hůla, František; Markopoulos, Angelos
Additive manufacturing (AM) has emerged as a promising technology for producing low-cost, customized tooling, particularly for prototyping and small-series injection molding. However, the inherent surface roughness and anisotropic properties of 3D-printed parts pose significant challenges for their direct use as functional mold inserts. This study investigates the effectiveness of various post-processing techniques on 3D-printed plastic inserts made from polyamide 12 (PA12) and glass bead-filled PA12 (PA12GB). The primary objective was to evaluate the impact of these surface treatments on the functional properties and service life of the mold inserts. A comprehensive analysis was conducted, including a detailed characterization of roughness using a confocal microscope, cross-sectional analysis to determine layer thickness, and tribological tests employing the ball-on-disc method to assess wear resistance. The study employed a modular injection mold and tested a range of surface finishing processes, including PostProcess Suspended Rotational Force (SRF) technology, metal decomposition coatings from HVM Plasma, and various methods from DyeMansion (Powershot S and Powerfuse). Results show a significant reduction in surface roughness across all methods. Notably, the vapor-based Powefuse treatment from DyeMansion achieved a surface roughness (Ra) of 1.2797 mu m, which is below the typical Ra value of 1.6 mu m for conventional metal molds, thereby making it suitable for high-quality molding applications. The tribological analysis provided critical insights into the durability and wear resistance of the treated surfaces, supporting their potential for extended use. This research validates the potential of specific post-processing methods to transform AM parts into functional tooling, enabling cost-effective and rapid prototyping in the plastics industry.
Methodology of Using CAx and Digital Twin Methods in the Development of a Multifunctional Portal Centre in Its Pre-Production Phase
(2025) Bernardin, Petr; Hájíček, Zdeněk; Janda, Petr; Kozák, Josef; Sedláček, František; Lašová, Václava; Kubíček, Jiří
The latest phase of the industrial revolution (Industry 4.0 and Industry 5.0) involves a large number of key areas that are crucial to improving the performance of technical systems. Computer-aided design and computer-aided engineering are important in their development and the digital twin of systems is one of the key tools for optimising their properties. This research deals with the use of these tools in the development of a machine tool. Nowadays, these tools are usually used separately. The aim of this work was therefore to propose a widely applicable methodology that would suitably combine the previously mentioned tools and thus use their synergistic effect. The proposed methodology was used on a specific machine, namely, a multifunctional portal centre, where features of computer-aided engineering (modelling, topology optimisation, stiffness and stress analyses, modal analyses, and analytical calculations) were combined with tools using the digital twin. The advanced simulations and the creation of the digital twin were performed in the pre-production phase of the machine and are described in detail within this paper. The aforementioned methodology was used to obtain and verify the final dimensions of the developed machine centre, which were the expected results. The proposed dimensions were verified in this way in terms of the mechanical properties of the designed machine (stiffness, strength, and modal properties), in terms of the suitability for machining the specific part, and in terms of the moved masses and drive parameters.
Integrating 3D Printing with Injection Molding for Improved Manufacturing Efficiency
(2025) Chval, Zdeněk; Ráž, Karel; da Silva, João Pedro Amaro Bennett
This study investigates a hybrid manufacturing approach that combines 3D printing and injection molding to extend the limitations of each individual technique. Injection molding is often limited by high initial tooling costs, long lead times, and restricted geometric flexibility, whereas 3D-printed molds tend to suffer from material degradation, extended cooling times, and lower surface quality. By integrating 3D-printed molds into the injection-molding process, this hybrid method enables the production of complex geometries with improved cost-efficiency. The approach is demonstrated using a range of polymeric materials, including ABS, nylon, and polyurethane foam-each selected to enhance the mechanical and thermal performance of the final products. Finite element method (FEM) analysis was conducted to assess thermal distribution, deformation, and stress during manufacturing. Results indicated that both temperature and stress remained within safe operational limits for 3D-printed materials. An economic analysis revealed substantial cost savings compared to fully 3D-printed components, establishing hybrid manufacturing as a viable and scalable alternative. This method offers broad industrial applicability, delivering enhanced mechanical properties, design flexibility, and reduced production costs.
Determination of Energy Losses of the Crank Press Mechanism
(2024) Hlaváč, Jan; Dekastello, Jiří
This paper focuses on determining the friction energy loss in the mechanism of a mechanical crank press. After defining the crank press mechanism and how it works, we describe the energy balance of a technological operation—forming. Four distinct methodologies for calculating friction loss in the mechanism are then presented, namely an empirical method, a spreadsheet calculation utilising force decomposition in a crank mechanism, an analytical calculation of the dynamic behaviour of a press, and a multibody simulation. Each additional approach expands the possibilities for approaching reality, but as the primary aim of the study is to compare the approaches, these possibilities are not exploited. Multibody simulation has proved itself to be accurate and suitable for simulating press mechanisms and investigating their dynamics. Multibody simulation is a much more powerful tool that can lead to a digital twin, which can help us to develop a less energy-demanding press. Confirmation of the multibody simulation results is the main outcome of the comparison and will be used in future work.
The fatigue of highly formed bodies
(2023) Kašpar, Jaromír; Bernardin, Petr; Lašová, Václava
Fatigue of cold formed parts is an important consideration especially in the automotive industry. Methods exist for predicting the fatigue of parts where the plastic deformation during forming is less than the uniform elongation. Nevertheless, many stamped parts include areas where forming strain exceeds uniform elongation. These areas are also very important in terms of high cyclic fatigue. Fatigue tests were carried out on these highly formed bodies. The results are presented in this paper. Also, a simple method is proposed for avoiding some common mistakes in fatigue evaluation.
Kombinované nůžky pro dělení a ostřihování nekonvenčních materiálů
(2024) Čechura, Milan; Hlaváč, Jan; Kubec, Václav
Procesy dělení materiálu jsou všeobecně známé a jejich konstrukční řešení jsou v podstatě standardizované, přesto je možné se setkat s nutnostmi inovativního řešení. V příspěvku je představeno konstrukční řešení nůžek integrovaných do stávající válcovací tratě. Komplexnost navrhovaného řešení je především v tom, že umožňuje provádět celou škálu střihů jak v příčném, tak v podélném směru, případně pod úhlem. Největší výzvou při hledání řešení bylo výrazné omezení zástavbového prostoru, který vychází z možností stávající válcovací tratě.
Lattice Structures—Mechanical Description with Respect to Additive Manufacturing
(2024) Ráž, Karel; Chval, Zdeněk; Pereira, Mathis
Lattice structures, characterized by their repetitive, interlocking patterns, provide an efficient balance of strength, flexibility, and reduced weight, making them essential in fields such as aerospace and automotive engineering. These structures use minimal material while effectively distributing stress, providing high resilience, energy absorption, and impact resistance. Composed of unit cells, lattice structures are highly customizable, from simple 2D honeycomb designs to complex 3D TPMS forms, and they adapt well to additive manufacturing, which minimizes material waste and production costs. In compression tests, lattice structures maintain stiffness even when filled with powder, suggesting minimal effect from the filler material. This paper shows the principles of creating finite element simulations with 3D-printed specimens and with usage of the lattice structure. The comparing of simulation and real testing is also shown in this research. The efficiency in material and energy use underscores the ecological and economic benefits of lattice-based designs, positioning them as a sustainable choice across multiple industries. This research analyzes three selected structures—solid material, pure latices structure, and boxed lattice structure with internal powder. The experimental findings reveal that the simulation error is less than 8% compared to the real measurement. This error is caused by the simplified material model, which is considering the isotropic behavior of the used material PA12GB (not the anisotropic model). The used and analyzed production method was multi jet fusion.
Evolutionary algorithm-driven screw press design
(2025) Fait, David; Karban, Pavel; Hofrichterová, Petra
This paper explores the integration of evolutionary algorithms (EAs) into the process of designing manufacturing machines. The goal is to partially substitute the work of the human designer with modern artificial intelligence methods. The study focuses on the application of ISRES (Improved Stochastic Ranking Evolution Strategy) to design a screw press. The first part of the text is dedicated to a literature review and the search for a similar application. The field of manufacturing machines is quite conservative and even in the context of the whole of mechanical engineering only a few similar research papers have been found. The next paragraph deals with the calculation methodology and a basic description of a screw press. The background calculation model is described in the next chapter. The paper then proceeds with the principles of evolutionary algorithms and leads on to the optimisation process. The last part deals with the connection to a CAD (Computer Aided Design) program. The paper then concludes with the advantages and possible impact in the context of mechanical engineering.
ComplexTrans–global land transportation systemThe best way ahead for railways and roads is coherent cooperation, not the competition
(2021) Hofman, Jiří; Čermák, Roman
The land-transportation cannot meet its demands anymore. Jammed highways and cities, dangerous emissions, omnipresent traffic accidents, delays, expensive railways.Solutions are being sought to transfer a large part of passenger-and especially freight-traffic to (high-speed) rail and the efforts are shifting towards electromobility, car-sharing, 5G-connectivity, autonomous ride, MaaS-transport-coordination or Hyperloop-type solutions. However, all these solutions have further problems and limitations.Solutions are not sought where they really exist -in the mutual adaptation of the road and rail vehicles and their deep cooperation.The ComplexTrans-project shows that simply adapting dimensions and functions of the road and rail vehicles can eliminate (or at least substantially reduce) all the problems of existing land transport. The main features of the ComplexTrans system are sufficient parking spaces, reduced traffic density inside and outside of the cities,electric-vehicles with unlimited range and cheaper than the standard cars, cheaper and affordable recharging of batteries, autonomous ride, self-financing rail-transport, transfer of intercity freight to rail, replacement of part of the continental air-transport and many others.
Optimisation of metal-to-composite bonded joints with various adhesive layer configurations using finite element method
(2017) Lašová, Václava; Bernardin, Petr; Sedláček, František
The purpose of this paper was to optimise several bonded joints using the optimisation cycle implemented in finite element analysis (FEA) software. These bonded joints were compared to each other based on different geometry and strength obtained by the optimisation cycle. For these bonded joints the bonded surfaces had various shapes and parameters. The impact of the length, thickness and cross-section angle of the adhesive layer on the resulting stress level and the final relative twist angle between a composite tube and a steel flange have been investigated. Specimens with cylindrical bonding surface were used as the reference shape, which influenced the calculated strength of the specimens. The shape of the bonded joint is in accordance with the bonded joints used for transmitting torque to machine tool spindles in machine tool design and results of this research will be used for similar applications.
Identification of the Cohesive Parameters for Modelling of Bonded Joints between Flat Composite Adherends with Thick Layer of Adhesive
(2024) Bernardin, Petr; Sedláček, František; Kozák, Josef; Kučerová, Ludmila; Lašová, Václava
The failure of bonded composite materials is accompanied by specific failure modes. These are specifically Mode I, Mode II, Mode III, and their combination (so-called mixed mode). These modes depend on the direction and type of loading. The mechanical properties describing the damage initiation and the damage evolution are unique according to the type of adhesive and present mode of failure. However, a few research studies have focused on an adhesive thicknesses greater than 0.2 mm. The main objective of this research is to investigate the mechanical properties of a bonded joint with large adhesive thickness loaded according to Modes I and II. The observed failure parameters, the cohesive and damage parameters, are identified by minimizing the difference between the force–displacement diagram obtained from the experimental data for both Mode I and Mode II. The finite element model is confronted with these parameters and is evaluated based on their agreement. Compared to other studies with a small adhesive layer thickness, the values of failure parameters are lower. The results show that the adhesive thickness has an influence on the values of cohesive and damage parameters and that these parameter values decrease significantly compared to a small adhesive thickness. The obtained parameters can be further used to predict the fracture toughness of other bonded joints loaded in any direction.
Using a Model Created Using a 3D Printer to Mould a Grey Cast Iron Casting
(2024) Ráž, Karel; Chval, Zdeněk; Kořínek, Jiří
This article deals with the possibility of using 3D-printed models as an input for the production of a mould for cast iron castings. This new progressive process is significantly faster (with sufficient accuracy) compared to the current way of making models for moulds. The need to create a wooden model is removed by this process. The quality of this wooden model was highly dependent on the experience and qualifications of the worker. This article describes the manufacturing process of the model and mould in detail. The key dimensions of the final parts are compared with the model and, thus, the accuracy of the chosen procedure is verified. A 3D-printing technology known as Multi Jet Fusion (MJF) was used to produce the model. The material used for the production of the model is polyamide PA12 with 40% glass fibre filling. This material has sufficient structural and strength properties to be used for the given application. Taking into account the dimensions of the part and the printing space of the printer, it was necessary to structurally modify and divide the part. The inlet cone of a turbine is used as an example This cone is produced from grey cast iron as standard.
Fatigue Estimation Using Inverse Stamping
(2023) Kašpar, Jaromír; Bernardin, Petr; Lašová, Václava
Reverse engineering methods like 3D scanning are becoming common in engineering practice. These methods enable engineers to reproduce the original shape of a scanned part. If other properties are required, then other reverse engineering methods can follow. Estimation of fatigue is a tricky task even if the material properties of the base material are known. Fatigue is influenced not only by material properties and the part’s shape but also by technological processes. Fast fatigue life estimation of stamped parts using reverse engineering methods is the target of this paper. The forming process, which has a crucial impact on the fatigue of stamped parts, is considered via inverse stamping. Adaptation of inverse stamping method from shell FEM meshes to volumetric meshes is included. The article also discusses the application of two methods, the Material Law for Steel Sheets (MLSS) and the Method of Variable Slopes (MVS). These methods adjust the fatigue curve based on effective plastic strain calculated by inverse stamping. Calculated results were compared with experimental results. In most situations, there is a good agreement between the calculations and the tests of the specimens without surface coatings. Sometimes, the calculated results are more conservative than the experiments. This is acceptable in component design in terms of reliability. When a Zn-Ni surface coating was applied, the fatigue life of the specimen decreased.
ComplexTrans – Global Rail-Road Transportation System: The Best Way Ahead for Railways and Roads Is Coherent Cooperation, Not the Competition
(2021) Hofman, Jiří; Čermák, Roman
Land transport can no longer meet the requirements. Crowded motorways and cities, dangerous emissions, ubiquitous traffic accidents, delays, expensive railways. Solutions are being sought to transfer a large part of passenger and especially freight transport to rail, and efforts are moving towards electromobility, car-sharing, 5G-connectivity, autonomous driving, MaaS-coordinated transport or Hyperloop-type solutions. However, all these solutions have additional challenges and limitations. Solutions are not being searched where they really exist - in the mutual adaptation of road and rail vehicles and their deep cooperation. The ComplexTrans project shows that simply adapting the dimensions and functions of road and rail vehicles can eliminate or significantly reduce all the problems of existing land transport. The main features of the ComplexTrans system are sufficient parking spaces, reduction of road congestions, cheap e-vehicles with unlimited range and increased utility value, cheap and simple charging infrastructure, 'autonomous' ride, easy cooperation of passenger and freight rail transport, railway self-financing, transferring big portion of transport from road and air to rail, covid protection and many others.
Optimization of Components with Topology Optimization for Direct Additive Manufacturing by DLMS
(MDPI, 2023) Sedláček, František; Kalina, Tomáš; Štěpánek, Martin
Tento článek představuje novou metodologii návrhu, která validuje a využívá výsledky topologické optimalizace jako finální tvar produktu. Navrhovaná metodologie má za cíl zjednodušit proces návrhu tím, že eliminuje potřebu remodelování a minimalizuje chyby tisku pomocí simulace procesu. Dále odstraňuje opakovaný export a import dat mezi softwarovými nástroji. Studie zahrnuje případovou studii, která se týká nosného domku řídícího sloupku závodního vozu, kde byla použita topologická optimalizace v programu Siemens NX a nezávislá verifikační analýza byla provedena za pomoci řešiče NX Nastran. Finální řešení bylo vyrobeno z materiálu AlSi10Mg prostřednictvím přímého sintrování laserem na 3D tiskárně a následně bylo úspěšně přímo aplikováno a ověřeno za reálných podmínek. Závěrem tento článek představuje komplexní metodologii návrhu pro přímé využití výsledků topologické optimalizace, která byla ověřena prostřednictvím případové studie a přinesla pozitivní výsledky.
Vyhodnocení efektu terapie na močovou inkontinenci u mužů po radikální roboticko asistované prostatektomii v rámci Rehaspring konceptu PPA
(LIEČREH s.r.o., 2023) Palaščáková Špringrová, Ingrid; Bartoníčková, Tereza; Firýtová, Rita; Drlík, Pavel
Východisko: Zhoubný nádor prostaty patří mezi nejčastější onkologická onemocnění u mužů. Pokud je nádor lokalizován pouze na prostatu, metodou léčby je pak radioterapie nebo radikální prostatektomie. Po radikální prostatektomii nalézáme u 80% mužů erektilní dysfunkci a u 10-15% trvalou stresovou inkontinenci různého stupně. Fyzioterapie svalů pánevního dna je nejčastěji doporučovaným konzervativním léčebním postupem močové inkontinence, kterou má vysoké procento mužů po operaci. Soubor: Výzkumný soubor tvořilo 23 mužů, kteří navštěvovali ambulantní zařízení fyzioterapie. Skupinu A (n=9, věk 57,4 ± 6,9 let) tvořili probandi, kteří podstoupili první vstupní vyšetření ještě před plánovanou radikální prostatektomií a byli kontinentní. Do skupiny B (n=14, věk 66,3 ± 10 let) byli zařazeni pacienti, kteří nejprve podstoupili operaci RARP a následně v intervalu 3-9 týdnů po výkonu přicházeli na vstupní vyšetření k fyzioterapeutovi. Probandi ze skupiny B trpěli po operaci únikem moči v různém množství. Metody: Pro získání výsledků efektivity terapie všech potřebných dat ke studii byly použity dotazníky Rehaspring konceptu PPA (Palascak Pelvic Aproach) a ICIQ-SF Guidelines dotazník pro kvantifikaci úniku moči. Výsledky: Nejvýraznější pokles byl mezi vstupním vyšetřením skupiny A (9,8±6,8) ICIQ- -SF bodů a skupiny B (18,5±4,97) ICIQ-SF a mezi 1. a 2. kontrolním vyšetřením skupiny A (6,3±4,9) ICIQ-SF bodů a skupiny B (9,64±5,7) ICIQ-SF bodů. Močová inkontinence poklesla o 36,2% u skupiny, která použila v terapii rektální závaží. Závěry: Výsledky studie ukázaly, že pravidelné cvičení a posílení svalů pánevního dna a také použití rektálního závaží má vliv na snížení močové inkontinence. Studie prokázala, že instruktáž před operací pacienta snižuje močovou inkontinenci po RARP.
Návrh pohonu kovacího lisu 25 MN bez předlohové hřídele a s planetovou převodovkou uvnitř setrvačníku na hlavním hřídeli
(Svaz kováren, 2022) Glatz, Karel; Hlaváč, Jan; Volejníček, Martin
Obsahem diplomové práce je rešerše na téma pohon mechanických lisů, planetové převodové mechanismy a diferenciály. Praktická část obsahuje návrh variant řešení pohonu lisu s využitím planetového převodového mechanismu nebo diferenciálu. Pro každou z nich je uveden postup konstrukčního řešení na lisu SKL 2500.
Use of SW tool to support teaching technical subjects
(MM publishing Ltd., 2022) Kratochvíl, Martin; Slámová, Ivana; Kalina, Tomáš; Hrdlička, Filip
Softwarový nástroj pro návrh nosníku byl vytvořen pro vzdělávací účely. SW Tool je založen na standardních vzorcích rozšířených o Ashbyho teorii. Jedná se tedy o SW nástroj pro konstrukční návrh profilů s ohledem na jejich stabilitu a umožňující tvarovou optimalizaci pro co nejefektivnější využití materiálu. SW nástroj je specializovaný tak, aby pomohl studentům rychle a snadno vyhodnotit vhodný profil. Tento článek pojednává o softwarovém nástroji, který se používá pro výukové účely a byl v praxi testován jako součást vysokoškolského předmětu. Cílem bylo na několika úkolech ověřit, zda studenti dokážou tento nový softwarový nástroj používat, a shromáždit data o jejich přístupu a výsledcích. Všechna data byla porovnána a vyhodnocena. Z hodnocení vyplynulo, že softwarový nástroj je uživatelsky přívětivý a studenti je mohou bez problémů okamžitě používat.

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