TY - JOUR A1 - Laumer, Tobias A1 - Stichel, Thomas A1 - Amend, Philipp A1 - Schmidt, Michael T1 - Simultaneous laser beam melting of multimaterial polymer parts JF - Journal of Laser Applications N2 - By simultaneous laser beam melting (SLBM), parts consisting of different polymer powders can be additively manufactured within one building process. Besides the advantages of conventional LBM, e.g., not needing additional tools and being able to realize parts with almost any geometry, different product requirements can be achieved within a single part. Product requirements may be different chemical resistances or haptic material properties. Therefore, SLBM enlarges the application field for additive manufacturing in general. In the process, two different materials are deposited on the building platform and preheated a few degrees below the melting temperature of the lower melting polymer by infrared emitters. Afterward, a CO2 laser (λ = 10.6 μm) provides the energy for the temperature difference between the preheating temperatures of both materials. Finally, a digital light processing chip is used to achieve simultaneous and flexible energy deposition for melting both preheated polymers. By illuminating the chip with a laser, parts of the beam can be flexibly guided onto the powder bed or into a beam trap. As laser, a single mode thulium laser (λ = 1.94 μm) is used. After melting the layer, a new layer is deposited and the process starts anew. In this paper, polypropylene and polyamide 12 are used as materials. After analyzing the material and melting behavior during the process by a high-resolution thermal imaging system, the parts are qualified regarding their material compatibility at the boundary zone and porosity by cross sections. KW - additive manufacturing KW - material qualification KW - Multi-Material Parts KW - new processes Y1 - 2015 U6 - https://doi.org/10.2351/1.4906303 SN - 1938-1387 SN - 1042-346X VL - 27 IS - S2 PB - Laser Institute of America ER - TY - GEN A1 - Herrmann, David A1 - Schaeffer, Leon A1 - Böhm, Valter ED - Flores, Paulo ED - Marques, Filipe ED - Da Rodrigues Silva, Mariana T1 - Theoretical considerations on 2D multistable tensegrity structures based on equilateral triangles T2 - MMT Symposium (Mechanism and Machine Theory Symposium): Book of Abstracts ; June 26-28, 2024. - Guimarães, Portugal Y1 - 2024 SN - 978-989-33-6448-2 IS - 1. edition SP - 403 EP - 404 PB - Departamento de Engenharia Mecânica, Universidade do Minho CY - Guimarães, Portugal ER - TY - BOOK A1 - Purr, Stephan T1 - Datenerfassung für die Anwendung lernender Algorithmen bei der Herstellung von Blechformteilen N2 - Der industrielle Fertigungsprozess von Blechformteilen unterliegt dem Einfluss einer Vielzahl von Parameterschwankungen, die das Umformergebnis signifikant mitbestimmen. Daher treten Qualitätsprobleme scheinbar zufällig auf und verursachen Ausschuss und einen Verlust an Produktivität. Ein vielversprechendes Mittel zur Verbesserung derartiger Prozesse ist der Einsatz von Datenanalysen und lernenden Algorithmen, die jedoch eine große Datenmenge voraussetzten. Bisher fehlten die Datenbasis und geeignete Möglichkeiten zur Datenerfassung für den Einsatz dieser Methoden. In dieser Arbeit wurde eine allgemeingültige und übertragbare Methode zur Erfassung und Speicherung relevanter Einfluss- und Ergebnisgrößen des Herstellprozesses von Blechformteilen entwickelt. Die Methode und die resultierenden Daten sind die Grundlage für die Analyse von Zusammenhängen im Prozess, die Vorhersage der Qualität durch maschinelles Lernen und die Berechnung geeigneter Maschineneinstellungen. Diese Anwendungen wurden in der Arbeit erprobt und die Ergebnisse bewertet. Dadurch konnten die Funktionalität der Datenerfassung und die erwarteten Potentiale bestätigt werden. N2 - The process of industrially producing shaped sheet metal parts is influenced by a large number of fluctuating factors. Therefore, quality problems appear to occur randomly and cause defective parts and a loss of productivity. A suitable way to improve these processes is the application of data analysis and statistical methods like machine learning, which require a large amount of data. So far, the data base and suitable methods for data acquisition are lacking for the use of these methods. Therefore, in this work, a generally valid and transferable method for recording and saving relevant influencing and resultant variables during the series production of sheet metal parts has been developed. This method and the resulting data are the basis for the analysis of correlations in the process, the prediction of quality by learning algorithms and the calculation of suitable press settings. These use cases were tested in the work and the results were evaluated. Thus, the functionality of the data acquisition and the expected potentials could be confirmed. KW - Digitalisierung KW - Umformen KW - Qualitätsmanagement KW - Maschinelles Lernen KW - Data Mining KW - Datenerfassung KW - Ingenieurwissenschaften KW - Maschinenbau KW - Produktionstechnik KW - Blechumformung KW - Tiefziehen KW - Umformtechnik KW - künstliche Intelligenz KW - lernende Algorithmen Y1 - 2020 U6 - https://doi.org/10.25593/978-3-96147-282-6 N1 - Zugl.: Diss., FAU Erlangen-Nürnberg, 2020 PB - FAU University Press ER - TY - JOUR A1 - Hoenicka, Markus A1 - Kaspar, Marcel A1 - Schmid, Christof A1 - Liebold, Andreas A1 - Schrammel, Siegfried T1 - Contact-free monitoring of vessel graft stiffness - proof of concept as a tool for vascular tissue engineering JF - Journal of tissue engineering and regenerative medicine N2 - Tissue-engineered vessel grafts have to mimic the biomechanical properties of native blood vessels. Manufacturing processes often condition grafts to adapt them to the target flow conditions. Graft stiffness is influenced by material properties and dimensions and determines graft compliance. This proof-of-concept study evaluated a contact-free method to monitor biomechanical properties without compromising sterility. Forced vibration response analysis was performed on human umbilical vein (HUV) segments mounted in a buffer-filled tubing system. A linear motor and a dynamic signal analyser were used to excite the fluid by white noise (0-200 Hz). Vein responses were read out by laser triangulation and analysed by fast Fourier transformation. Modal analysis was performed by monitoring multiple positions of the vessel surface. As an inverse model of graft stiffening during conditioning, HUV were digested proteolytically, and the course of natural frequencies (NFs) was monitored over 120 min. Human umbilical vein showed up to five modes with NFs in the range of 5-100 Hz. The first natural frequencies of HUV did not alter over time while incubated in buffer (p = 0.555), whereas both collagenase (-35%, p = 0.0061) and elastase (-45%, p < 0.001) treatments caused significant decreases of NF within 120 min. Decellularized HUV showed similar results, indicating that changes of the extracellular matrix were responsible for the observed shift in NF. Performing vibration response analysis on vessel grafts is feasible without compromising sterility or integrity of the samples. This technique allows direct measurement of stiffness as an important biomechanical property, obviating the need to monitor surrogate parameters. Copyright (C) 2016 John Wiley & Sons, Ltd. KW - ANEURYSMS KW - ARTERIES KW - Biomechanics KW - BIOREACTOR KW - BLOOD-VESSELS KW - BYPASS GRAFTS KW - CONSTRUCTS KW - design KW - extracellular matrix KW - human umbilical vein KW - IN-VITRO KW - MECHANICAL-PROPERTIES KW - proteolysis KW - small calibre graft KW - vascular tissue engineering Y1 - 2017 U6 - https://doi.org/10.1002/term.2186 VL - 11 IS - 10 SP - 2828 EP - 2835 PB - Wiley ER - TY - CHAP A1 - Tahedl, Michael A1 - Borchsenius, Fredrik A1 - Taras, Andreas T1 - Efficient earthquake simulation of stiff and high DOF bridge expansion joint models with Python T2 - Proceedings of the 10th ECCOMAS Thematic Conference on MULTIBODY DYNAMICS: December 12-15, 2021, Budapest, Hungary N2 - Various types of seismic protection devices has been developed to protect structures like bridges from collapse during an earthquake event, such as hydraulic or metallic hysteresis dampers and spherical pendulum bearings. The expansion joints however, which are already included in most large-span bridges, are not considered as an earthquake protection device regardless of the significant friction forces they produce. These friction forces can be seen as damping forces between the shaking environment and the oscillating bridge. To investigate the effect of those damping forces during different earthquake loads, a multibody dynamics simulation model of the expansion joints will be created. This model should be accurate enough to represent the generation of the damping forces and effects of the geometric setup of the expansion joints. Because large expansion joints for large-span bridges are of special interest, the number of degrees of freedom (DOF) becomes very high. Because this models include stiff bushings, implicit solvers need to be used to gain a stable simulation. Expansion joints are almost unique constructions for every specific bridge, which requires a automated model generation. Because of its excellent modules for numerical mathematics, the scripting language Python is used. To create an efficient simulation model, several optimization techniques such as Just-In-Time (JIT) compilation and parallelization are implemented and tested. KW - Parallelization KW - Optimization KW - Python KW - Earthquake Engineering Y1 - 2021 SN - 978-963-421-870-8 U6 - https://doi.org/10.3311/ECCOMASMBD2021-196 SP - 172 EP - 183 PB - Budapest University of Technology and Economics CY - Budapest, HU ER - TY - JOUR A1 - Reindl, Thomas A1 - Meisner, Dennis A1 - Hierl, Stefan T1 - Benchmarking of plastic-based Additive Manufacturing Processes JF - RTejournal - Forum für Rapid Technologie N2 - Additive Manufacturing (AM) is a future-oriented manufacturing technology that is experiencing an enormous boom in the times of Industry 4.0. As a result, various AM technologies and printer models from different manufacturers are entering the market over a short time span. With the advancing establishment of this manufacturing technology for series applications, the expectations and requirements of the fabricated components are also increasing. However, a major challenge is the application-specific selection of the most suitable AM process due to a lack of comparable data. Furthermore, there needs to be more know-how regarding the geometrical and mechanical characteristics of AM parts. This paper addresses this problem by comparing the three most common plasticbased AM processes in the areas of surface quality, dimensional accuracy, and mechanical properties. Roughness measurements, evaluation of a benchmark artifact, tensile tests, and load increase tests are carried out. Based on the results, the individual possibilities and limitations of the compared AM processes can be detected. KW - Additive Manufacturing KW - benchmark artifact KW - dimensional accuracy KW - Fused Layer Modeling KW - mechanical properties KW - Multi Jet Fusion KW - process benchmark KW - Selective Laser Sintering KW - surface quality Y1 - 2023 U6 - https://doi.org/https://doi.org/10.58134/fh-aachen-rte_2023_002 PB - Fachhochschule Aachen ER - TY - CHAP A1 - Schneidewind, Jan A1 - Galka, Stefan T1 - Interactive reinforcement learning-based factory layout planning T2 - 13th Conference on Learning Factories (CLF 2023), 9-11 May 2023, Reutlingen, Germany N2 - Due to the complexity and the number of factors involved in factory layout planning, computers were identified as an efficient tool to support the process. However, so far no method for computer-aided layout planning has gained wide acceptance in practical application. One reason for this is that in present approaches either the user or the computer designs the layout, neglecting either the qualitative or the quantitative goals. To bridge this gap, this article introduces a concept for human-computer-integration based on evaluative feedback and inverse reinforcement learning. A key element of the concept is the interactive planning process in which user and computer alternately design and improve the layout until a satisfactory layout is found. The user evaluates the layouts according to qualitative criteria, adjusts them intuitively and specifies objectives and restrictions in an explorative way. The computer on the other hand – in form of a reinforcement algorithm – generates possible layouts and incorporates the user’s feedback into its policy. This synergy is expected to generate better results than an expert or an algorithm alone could. Furthermore, in the context of learning factories, it encourages critical thinking and allows students to develop a deeper understanding of the factors that contribute to efficient manufacturing processes. Both an architecture for the implementation is proposed and the requirements for the user interface are specified. KW - factory planning KW - facility layout problem KW - machine learning KW - optimization KW - inverse reinforcement learning Y1 - 2023 UR - https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4469300 PB - SSRN ER - TY - CHAP A1 - Galka, Stefan T1 - Untersuchung von Auftragsfreigabestrategien für mehrzonige Kommissioniersysteme im Online-Lebensmittelhandel T2 - ASIM SST 2022 Proceedings Langbeiträge, 26. ASIM Symposium Simulationstechnik: 25.07.-27.07.2022, TU Wien N2 - This paper briefly presents the challenges for order control and release of multi-zone order picking systems. On the one hand, the order control must ensure that all orders are processed on time, and on the other hand, the space requirements (buffer) and the utilisation of the zones must be considered. Within the framework of a case study, different strategies for order release were developed. The paper shortly describes the ideas of the strategies and presents results of a case-based simulative evaluation of the strategies. The findings of the simulation study are the basis for the development of a digital twin for the operational control of multi-zone picking systems. KW - Simulation KW - Kommissionierung KW - Simulation KW - Logistik KW - Planung Y1 - 2022 SN - 978-3-901608-97-1 U6 - https://doi.org/10.11128/arep.20.a2021 VL - 2022 SP - 23 EP - 30 PB - ARGESIM Verlag CY - Wien ER - TY - GEN A1 - Rieffel, John A1 - Herrmann, David A1 - Lehmann, Lukas A1 - Schaeffer, Leon A1 - Böhm, Valter ED - Flores, Paulo ED - Marques, Filipe ED - Da Rodrigues Silva, Mariana T1 - Illuminating the morphological diversity of 2D tensegrity grids T2 - MMT Symposium (Mechanism and Machine Theory Symposium): Book of Abstracts ; June 26-28, 2024. - Guimarães, Portugal Y1 - 2024 UR - https://mmtsymposium.com/wp-content/uploads/2024/07/mmtsymposium_bookofabstracts.pdf SN - 978-989-33-6448-2 IS - 1. edition SP - 457 EP - 458 PB - Departamento de Engenharia Mecânica, Universidade do Minho CY - Guimarães, Portugal ER - TY - CHAP A1 - Schmid, Florian A1 - Galka, Stefan A1 - Marinkovic, Minja A1 - Meißner, Sebastian ED - Bergmann, Sören ED - Feldkamp, Niclas ED - Souren, Rainer ED - Straßburger, Steffen T1 - Simulationsbasierte Untersuchung von Abstraktionsgraden im Kontext Digitaler Zwillinge für innerbetriebliche Transportsysteme T2 - Tagungsband 20. ASIM-Fachtagung Simulation in Produktion und Logistik, Ilmenau, 13. – 15. September 2023 N2 - Current challenges in the planning and control of internal logistics systems are based on permanent changes in the requirements on the system, e.g., due to fluctuating order numbers or changes in their structure. For the representation and planning of in-house logistics processes, digital twins offer the possibility to verify different operational decisions such as predictive workforce scheduling. In this context, the quality of the results and their in-time presentation plays a decisive role. However, both target criteria are influenced by the detail-level of the digital representation. Based on a case study, this paper investigates the influence of the level of detail on the simulation runtime and result divergence to provide an evaluation for detail levels in the modelling of intralogistic transport systems. T2 - Simulation-based Analysis of Abstraction Degrees in the Context of Digital Twins for Intralogistics Transport Systems Y1 - 2023 SN - 978-3-86360-276-5 U6 - https://doi.org/10.22032/DBT.57794 SP - 135 EP - 144 PB - Universitätsverlag Ilmenau CY - Ilmenau ER - TY - CHAP A1 - Galka, Stefan A1 - Schmid, Florian A1 - Grasser, Dominik A1 - Hohm, Jonathan A1 - Stauber, Stephan A1 - Meißner, Sebastian T1 - Integration eines SAP-Transportleitsystem in eine Simulationsumgebung zur Unterstützung von Entscheidungen im operativen Betrieb T2 - Tagungsband 20. ASIM-Fachtagung Simulation in Produktion und Logistik, Ilmenau, 13. – 15. September 2023 N2 - Digital twins enable the digital representation of physical systems and provide comprehensive modelling and analysis capabilities. An online data exchange between the Digital twin and SAP is feasible, through integration of a transport control systems (SAP) via RESTful API. This interface allows decision making in resource allocation and furthermore the adaptation of the digital model if the real system changes. Despite the associated challenges in terms of data synchronisation, the integration has benefits such as a reduction in modelling effort and an increase in the lifetime of the digital twin. In the context of this work, the design of the interface between the simulation software and a SAP transport control system via RESTful API is described. Y1 - 2023 SN - 978-3-86360-276-5 U6 - https://doi.org/10.22032/DBT.57813 SP - 281 EP - 291 PB - Universitätsverlag Ilmenau CY - ILmenau ER -