TY - CHAP A1 - Hierl, Stefan ED - Meran, Cemal T1 - Laser Transmission Welding of Plastics BT - Principles, Applications and Process Monitoring T2 - 15th International Materials Symposium - IMSP'2014, Denizli, 2014 Y1 - 2014 SP - 1084 EP - 1093 ER - TY - CHAP A1 - Schmailzl, Anton A1 - Hüntelmann, Sven A1 - Loose, Tobias A1 - Käsbauer, Johannes A1 - Maiwald, Frederik A1 - Hierl, Stefan ED - Sommitsch, Christof ED - Enzinger, Norbert ED - Mayr, Peter T1 - Potentials of the ALE-Method for Modeling Plastics Welding Processes, in Particular for the Quasi-Simultaneous Laser Transmission Welding T2 - Mathematical Modelling of Weld Phenomena 12 N2 - The Arbitrary-Lagrangian-Eulerian-Method (ALE-Method) offers the possibility to model the quasi-simultaneous laser transmission welding of plastics, in which a squeeze-flow of molten plastic occurs. It is of great interest to get a deeper understanding of the fluid-structure-interactions in the welding zone, since the occurring squeeze-flow transports heated material out of the joining zone, causinga temperature decrease inside.In addition, the numerical modelling offers the possibility to investigate the flow conditions in the joining zone. The aim of this article is to show the potentials of the ALE-Method to simulatethe quasi-simultaneous laser transmission welding with the commercially available software LS-DYNA. The central challenge is to realize a bi-directionalthermo-mechanically coupled simulation,which considers the comparatively high thermal expansion and calculates the interactions of solid and melted plastic correctly. Finally, the potentials of the ALE element formulations for the mathematical description of welding processesare shown, especially for those with a squeeze-flow. Y1 - 2018 U6 - https://doi.org/10.3217/978-3-85125-615-4-51 SP - 965 EP - 975 PB - Verlag der Technischen Universität Graz CY - Graz ER - TY - CHAP A1 - Schmailzl, Anton A1 - Hierl, Stefan A1 - Schmidt, Michael ED - Schmidt, Michael T1 - Gap-Bridging during Quasi-Simultaneous Laser Transmission Welding T2 - Physics Procedia N2 - Tightness is often the main requirement for quasi-simultaneous laser transmission welds. However, remaining gaps cannot be detected by the used set-path monitoring. By using a pyrometer in combination with a 3D-scanner, weld seam interruptions can be localized precisely while welding, due to temperature deviations along the weld contour. To analyze the temperature signal in correlation to the progress of gap-bridging, T-joint samples with predefined gaps are welded. The set-path is measured synchronously. Additionally, the temperature distribution and the influence of the thermal expansion of the polymers are studied by a thermo-mechanical FEM-process simulation. On top of that, the melt blow-out of the welded samples is analyzed using μCT-measurements. The experiments have shown that closing of a gap can be identified reliably by the temperature signal and that the squeezed melt flow into the gap and the thermal expansion in the gap zone accelerates gap-bridging. Furthermore the inserted heat can be adapted in the fault zone, in order to avoid thermal damage. Y1 - 2016 U6 - https://doi.org/10.1016/j.phpro.2016.08.113 SN - 1875-3892 SN - 1875-3884 VL - 83 SP - 1073 EP - 1082 PB - Elsevier CY - Amsterdam [u.a.] ER - TY - CHAP A1 - Schmailzl, Anton A1 - Amann, Thomas A1 - Glockner, Markus A1 - Fandanelli, Martin A1 - Wagner, Marcus A1 - Hierl, Stefan ED - CADFEM GmbH, ED - ANSYS Germany GmbH, T1 - Finite element analysis of thermoplastic probes under tensile load using ls-dyna compared to ansys workbench 14 in correlation to experimental investigations T2 - ANSYS Conference & 30th CADFEM Users' Meeting - ACUM, 24.-26- Oktober 2012, Kassel N2 - Joining thermoplastic requisitions is a popular technique to build sophisticated plastic applications. Therefore the laser-transmission welding process is used to join thermoplastic polymers in visible regions. The clamping force in this case plays a decisive role when it comes to the weld quality. Simulating the clamping pressure with finite element techniques is therefore highly attractive to understand the principal of the process. Thermoplastic polymers under tensile load often show a brittle behavior coupled with softening. Simulating such materials is quite difficult for FEM programs. In this case a finite element study of the tensile test in LS-DYNA and ANSYS Wb 14 with respect to the material models was analysed. The experimental data get validated in comparison with the FEM solution for a tensile test. The material models and the problems in simulating softening behavior for thermoplastic polymers were discussed Y1 - 2012 UR - https://www.oth-regensburg.de/fileadmin/media/fakultaeten/m/labore/FEM/pdf/fb-2012_paper_acum.pdf N1 - DVD-ROM SP - 1 EP - 10 CY - Grafing bei München ER - TY - CHAP A1 - Schmailzl, Anton A1 - Quandt, Benjamin A1 - Schmidt, Michael A1 - Hierl, Stefan T1 - In-Situ Process Monitoring during Laser Transmission Welding of PA6-GF30 T2 - Procedia CIRP N2 - Quasi-simultaneous laser transmission welding is preferably used for packaging sensors and electronics. In order to protect the components from moisture, a hermetic encapsulation is needed. However, local weld seam interruptions cannot be identified with the commonly used set-path monitoring. By using a pyrometer, coaxially integrated into a 3D-scanner, gaps between the joining partners can be allocated on basis of the measured temperature. However, the scattering of the heat radiation, especially caused by the fiber reinforcement of the plastics, leads to a reduction of the accessible heat radiation, which makes the identification of gaps considerably more difficult. The herein used experimental setup is characterized by a small detection spot and only by a slight weakening of the heat radiation inside the scanner. Hence, for welding PA6-GF30, the detection of small sized gaps is possible, even if a glass fiber content of 30 percent (wt.) and a weld seam width with approximately 1 mm are given. Y1 - 2018 U6 - https://doi.org/10.1016/j.procir.2018.08.131 VL - 74 SP - 524 EP - 527 ER - TY - JOUR A1 - Schmailzl, Anton A1 - Hierl, Stefan A1 - Sieben, Manuel A1 - Brunnecker, Frank T1 - Optimierung der Spanndruckverteilung beim Laserdurchstrahlschweißen komplexer Bauteile mittels FE-Berechnung JF - JOINING PLASTICS Y1 - 2013 VL - 7 IS - 1 SP - 30 EP - 34 ER - TY - CHAP A1 - Schmailzl, Anton A1 - Hierl, Stefan ED - Ziemann, Olaf ED - Bogner, Werner ED - Mottok, Jürgen T1 - Online-process monitoring of laser transmission welding for polymers T2 - Applied Research Conference 2013, ARC 2013 ; 17th and 18th October 2013, Deggendorf Y1 - 2013 SP - 374 EP - 378 PB - Shaker CY - Aachen ER - TY - JOUR A1 - Maiwald, Frederik A1 - Englmaier, Stephan A1 - Hierl, Stefan T1 - Online pyrometry for weld seam localization in absorber-free laser transmission welding of transparent polymers JF - Journal of Laser Micro/Nanoengineering N2 - Production of optical and medical devices makes high demands on cleanliness, precision, visual appearance and reliability. Advantages of laser transmission welding – contactless input of energy, high precision, no adhesives and no particle formation – can be fully exploited for this use. For absorber-free welding, lasers emitting in the polymers’ intrinsic absorption spectrum between 1.6 μm and 2 μm are used. Focusing the laser beam with high NA provides large intensity gradients inside the specimen and enables selective fusing of the joining zone without affecting the surface. Since a molten upper surface leads to visible and palpable irregularities and causes warpage, the verticalexpansion of the weld seam is crucial. To meet the high quality and reliability required in the medical and optical industry, online monitoring of the seam is necessary. The aim of this work is the localization and evaluation of the weld seam using pyrometry. First, the emitted thermal radiation is computed, enabling signal analysis regarding origin and spectrum. Thus, assessment of measurement spectrum and forecast of the signal in dependence on seam shape and position is possible. Finally, welding tests with Topas 8007-04 are performed at 200 mm/s feed rate and monitored with 100 kHz. The comparison of tracked data with thin-cuts demonstrates that weld seam localization by pyrometry is possible, enabling online assessment of the process. KW - Laserdurchstrahlschweissen KW - Kunststoff KW - Transparenz KW - Schweißnaht KW - Wärmestrahlung KW - Pyrometrie KW - Prozessüberwachung Y1 - 2021 U6 - https://doi.org/10.2961/jlmn.2021.01.2002 SN - 1880-0688 VL - Vol. 16 IS - 1 SP - 8 EP - 13 PB - Japan Laser Processing Society ER - TY - CHAP A1 - Maiwald, Frederik A1 - Englmaier, Stephan A1 - Hierl, Stefan T1 - Online pyrometry for weld seam localization in absorber-free laser transmission welding of transparent polymers T2 - 21st International Symposium on Laser Precision Microfabrication: Dresden, 26.06.2020 N2 - Optical and medical devices made of transparent polymers are gaining popularity because of its cost advantages. The manufacturing technology must be able to meet the high demands of these applications. Advantages of laser transmission welding – contactless input of energy, precision, no adhesives and no particle formation – can be exploited here. For absorber-free welding, lasers emitting in the polymers‘ intrinsic absorption spectrum are used. Focusing the laser beam with high NA enables selective fusing of the joining zone. Since a molten upper surface leads to visible and palpable irregularities, the lateral expansion of the weld seam is monitored in this work. Welding tests with 1 mm thick plates of COC are performed and monitored by pyrometry. Distances between seam and surface measured in thin cuts and are compared with the pyrometer signal. This shows that the localization of the weld seam is possible and proper and faulty parts can be distinguished by pyrometry. KW - Laserdurchstrahlschweissen KW - Kunststoff KW - Transparenz KW - Schweißnaht KW - Wärmestrahlung KW - Pyrometrie KW - Prozessüberwachung Y1 - 2020 UR - http://www.jlps.gr.jp/en/proc/lpm/20/073.pdf PB - Japan Laser Processing Society ER - TY - JOUR A1 - Maiwald, Frederik A1 - Hierl, Stefan T1 - Pyrometerbasierte Prozessüberwachung beim Laserkunststoffschweißen JF - Photonik KW - Laserschweissen KW - Kunststoff KW - Prozessüberwachung KW - Pryrometer Y1 - 2020 IS - 52 SP - 22 EP - 25 PB - AT-Fachverl. CY - Fellbach ER - TY - CHAP A1 - Käsbauer, Johannes A1 - Schmailzl, Anton A1 - Prehm, Jens A1 - Loose, Tobias A1 - Hierl, Stefan T1 - Simulation of Quasi-Simultaneous Laser Transmission Welding of Plastics BT - Optimization of Material Parameters in Broad Temperature Range T2 - Procedia CIRP N2 - Thermo-mechanical simulation offers great opportunities to optimize welding processes of plastics. For realistic simulation, the temperature dependent mechanical properties need to be implemented from ambient temperature to temperatures above the flow temperature. Standard test methods are insufficient for characterization in the entire temperature range because close to the flow temperature the material is too soft for tensile tests and too stiff for rheometry. Therefore, an optimization strategy is developed, that determines unknown material parameters by testing in welding simulations. The unknown parameters are iteratively adjusted to minimize the mismatch between computed and measured set-paths. Thus, important process characteristics are calculated realistically, enabling the computer aided assessment of the weld quality. KW - plastics welding KW - simulation KW - material modelling KW - optimization KW - parameterization KW - Kunststoffschweißen KW - Thermomechanische Eigenschaft KW - Simulation Y1 - 2020 U6 - https://doi.org/10.1016/j.procir.2020.09.136 VL - 94 SP - 737 EP - 741 PB - Elsevier ER - TY - CHAP A1 - Maiwald, Frederik A1 - Englmaier, Stephan A1 - Hierl, Stefan T1 - Absorber-free Laser Transmission Welding of Transparent Polymers using Fixed Focus Optics and 3D Laser Scanner T2 - Procedia CIRP N2 - Laser transmission welding is a well-known joining technology for thermoplastics, providing reliable and hermetical sealing without adhesives or particle formation. The main advantages of laser-based energy input - high precision, no additional adhesive and no particle emission - are essential for medical and optical applications. To obtain sufficient absorption in visually transparent polymers, thulium fibre lasers emitting in the polymers’ intrinsic absorption spectrum are used. Optics with high numerical aperture provide large intensity gradients inside the specimen, enabling selective fusing in the joining zone. Although the basic feasibility has already been demonstrated, the welding process lacks stability and productivity. Aim of this work is the determination of optimized settings for a fast and reliable welding process. Thus, the interplay of process parameters as well as their impact on the seam are analysed by thermal simulations. Calculated settings are verified by welding tests with COC, PA6 and PETG, using a fixed-focus optics and a 3D laser scanner with up to 200 mm/s feed rate. Y1 - 2020 U6 - https://doi.org/10.1016/j.procir.2020.09.117 VL - 94 SP - 686 EP - 690 PB - Elsevier ER - TY - JOUR A1 - Schmailzl, Anton A1 - Käsbauer, Johannes A1 - Martan, Jiří A1 - Honnerová, Petra A1 - Schäfer, Felix A1 - Fichtl, Maximilian A1 - Lehrer, Tobias A1 - Prušáková, L. A1 - Tesař, Jiří A1 - Skála, J. A1 - Honner, Milan A1 - Hierl, Stefan T1 - Measurement of Core Temperature through Semi-Transparent Polyamide 6 using Scanner-Integrated Pyrometer in Laser Welding JF - International Journal of Heat and Mass Transfer N2 - Predicting the core temperature during welding is an ambitious aim in many research works. In this work, a 3D-scanner with integrated pyrometer is characterized and used to measure the temperature during quasi-simultaneous laser transmission welding of polyamide 6. However, due to welding in an overlap configuration, the heat radiation emitted from the joining zone of a laser transmission weld has to pass through the upper polymer, which is itself a semi-transparent emitter. Therefore, the spectral filtering of the heat radiation in the upper polymer is taken into account by calibrating the pyrometer for the measurement task. Thermal process simulations are performed to compare the temperature field with the measured temperature signal. The absorption coefficients of the polymers are measured, in order to get precise results from the computation. The temperature signals during welding are in good agreement with the computed mean temperature inside the detection spot, located in the joining area. This is also true for varying laser power, laser beam diameter and the carbon black content in the lower polymer. Both, the computed mean temperature and the temperature signal are representing the core temperature. In order to evaluate the spatial sensitivity of the measurement system, the emitted heat radiation from both polymers is calculated on basis of the computed temperature field. Hereby it is found, that more than 90 percent of the detected heat radiation comes from the joining area, which is a crucial information for contact-free temperature measurement tasks on semi-transparent polymers. KW - Semi-transparent polymer KW - Pyrometer KW - Laser transmission welding KW - Temperature KW - measurement Y1 - 2020 U6 - https://doi.org/10.1016/j.ijheatmasstransfer.2019.118814 VL - 146 IS - January PB - Elsevier ER - TY - CHAP A1 - Schmailzl, Anton A1 - Quandt, Benjamin A1 - Hierl, Stefan A1 - Schmidt, Michael T1 - Correlation between Joint Strength and Process Temperature in Quasi-Simultaneous Laser Transmission Welding of Polyamide 6 T2 - Proceedings of LiM2019 - Lasers in Manufacturing (23 June 2019, Munich) N2 - The joint strength is gaining importance in quasi -simultaneous laser transmission welds, especially in structural components. A correlation between the joint strength and a process characteristic is a basic requirement for selecting the best process parameter setting. In this work, the temperature is measured during welding polyamide 6 by using a scanner-integrated pyrometer with an InGaAs-detector. The filtering of the heat radiation in the upper joining partner is taken into account by calibrating the mea surement system. By this, the measured temperature signal represents the temperature in the joining zone. A correlation is found between the measured temperature and the resulting joint strength. Moreover, high joint strengths are also seen for welds with short welding times, as far as the temperature is sufficiently high. With this knowledge, a process window can be derived easily in order to produce welds with high strength and short welding times. Y1 - 2019 SP - 1 EP - 10 PB - Wissenschaftliche Gesellschaft Lasertechnik e.V. ER - TY - JOUR A1 - Käsbauer, Johannes A1 - Schmailzl, Anton A1 - Weber, Ulrich A1 - Hierl, Stefan A1 - Jaus, Tobias A1 - Schwalme, Michael T1 - Simulationsgestützte Evaluierung von Strahloszillationsmustern beim quasi-simultanen Laser-Durchstrahlschweißen JF - JOINING PLASTICS - Fügen von Kunststoffen Y1 - 2019 VL - 13 IS - 2 SP - 102 EP - 109 PB - DVS-Verl., Verl. für Schweißen und Verwandte Verfahren CY - Düsseldorf ER - TY - CHAP A1 - Quandt, Benjamin A1 - Schröcker, Korbinian A1 - Hierl, Stefan ED - Huber, Otto ED - Bicker, Marc ED - Patzelt, Peter T1 - Prozessüberwachung beim quasi-simultanen Laser-Durchstrahlschweißen glasfaserverstärkter Thermoplaste T2 - 9. Landshuter Leichtbau-Colloquium: Leichtbau in Forschung und industrieller Anwendung von der Nano- bis zur Makroebene, 27. / 28. Februar 2019 Hochschule Landshut, Tagungsband zum Colloquium Y1 - 2019 SP - 56 EP - 64 PB - LC-Verlag CY - Landshut ER - TY - GEN A1 - Käsbauer, Johannes A1 - Schmailzl, Anton A1 - Loose, Tobias A1 - Hierl, Stefan T1 - Thermo-Mechanical Modeling of Quasi-Simultaneous Laser Transmission Welding using LS-DYNA with Focus on Accuracy of Heat Input Calculation T2 - Technology Day 2020 - Plastics on the test rig, Traboch, 04.03.2020 Y1 - 2020 ER - TY - JOUR A1 - Hüntelmann, Sven A1 - Hierl, Stefan T1 - AM-gerechte Bauteilgestaltung BT - Erarbeitung eines methodischen Vorgehens für die Topologieoptimierung additiv gefertigter Bauteile JF - additive - Das Magazin für generative Fertigung Y1 - 2020 UR - https://additive.industrie.de/forschung/am-gerechte-bauteilgestaltung/#slider-intro-2 IS - 1 SP - 57 PB - Konradin-Verlag Robert Kohlhammer GmbH CY - Leinfelden-Echterdingen ER - TY - GEN A1 - Käsbauer, Johannes A1 - Schmailzl, Anton A1 - Loose, Tobias A1 - Hierl, Stefan T1 - Potentials of the EFG-Method for Modeling Quasi-Simultaneous Laser Transmission Welding Considering the Melt Flow T2 - Simulationsforum 2019 - Schweißen und Wärmebehandlung, Weimar Y1 - 2019 ER - TY - CHAP A1 - Hüntelmann, Sven A1 - Hierl, Stefan T1 - Methodisches Vorgehen bei der Topologieoptimierung additiv gefertigter Bauteile T2 - Technikforum 3D Druck - Innovative Ansätze für Bauteiloptimierung, Design und Konstruktion. Technologie Centrum Westbayern, 27.11.2018 Y1 - 2018 ER - TY - GEN A1 - Maiwald, Frederik A1 - Hierl, Stefan T1 - Absorberfreies Laser-Durchstrahlschweißen transparenter Kunststoffe T2 - InnovationForum Medizintechnik, Tuttlingen, 24.10.2019 Y1 - 2019 ER - TY - RPRT A1 - Schillinger, Moritz A1 - Görlach, Julien A1 - Hierl, Stefan ED - Baier, Wolfgang T1 - Erstellung eines Konstruktionskatalogs für die additive Fertigung T2 - Forschung 2018 N2 - Die additive Fertigung bietet vielfältige Möglichkeiten hinsichtlich der Bauteilgestaltung. Jedoch sind auch bei den generativen Fertigungsverfahren konstruktive Randbedingungen zu beachten, um Bauteile kostengünstig und mit optimalen Eigenschaften herzustellen. Es ist bereits umfangreiche Fachliteratur erhältlich, die entsprechende Konstruktionsempfehlungen gibt. Um Produktentwickler bedarfsgerecht zu unterstützen, ist jedoch ein Nachschlagewerk erforderlich, das mit geeigneter Systematik Konstruktionsvorschläge ausgibt, die zur aktuellen Problemstellung passen. Aufbauend auf dem Stand der Technik, eigenen Analysen und experimentellen Untersuchungen werden erste Ansätze für ein solches Nachschlagewerk vorgestellt. KW - Rapid prototyping KW - Methodisches Konstruieren KW - Konstruktionskatalog Y1 - 2018 UR - https://doi.org/10.35096/othr/pub-1382 SP - 70 EP - 71 ER -