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 -