@inproceedings{QuandtSchroeckerHierl, author = {Quandt, Benjamin and Schr{\"o}cker, Korbinian and Hierl, Stefan}, title = {Prozess{\"u}berwachung beim quasi-simultanen Laser-Durchstrahlschweißen glasfaserverst{\"a}rkter Thermoplaste}, series = {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}, booktitle = {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}, editor = {Huber, Otto and Bicker, Marc and Patzelt, Peter}, publisher = {LC-Verlag}, address = {Landshut}, pages = {56 -- 64}, language = {de} } @misc{KaesbauerSchmailzlLooseetal., author = {K{\"a}sbauer, Johannes and Schmailzl, Anton and Loose, Tobias and Hierl, Stefan}, title = {Thermo-Mechanical Modeling of Quasi-Simultaneous Laser Transmission Welding using LS-DYNA with Focus on Accuracy of Heat Input Calculation}, series = {Technology Day 2020 - Plastics on the test rig, Traboch, 04.03.2020}, journal = {Technology Day 2020 - Plastics on the test rig, Traboch, 04.03.2020}, language = {en} } @article{HuentelmannHierl, author = {H{\"u}ntelmann, Sven and Hierl, Stefan}, title = {AM-gerechte Bauteilgestaltung}, series = {additive - Das Magazin f{\"u}r generative Fertigung}, journal = {additive - Das Magazin f{\"u}r generative Fertigung}, number = {1}, publisher = {Konradin-Verlag Robert Kohlhammer GmbH}, address = {Leinfelden-Echterdingen}, pages = {57}, language = {de} } @misc{KaesbauerSchmailzlLooseetal., author = {K{\"a}sbauer, Johannes and Schmailzl, Anton and Loose, Tobias and Hierl, Stefan}, title = {Potentials of the EFG-Method for Modeling Quasi-Simultaneous Laser Transmission Welding Considering the Melt Flow}, series = {Simulationsforum 2019 - Schweißen und W{\"a}rmebehandlung, Weimar}, journal = {Simulationsforum 2019 - Schweißen und W{\"a}rmebehandlung, Weimar}, language = {en} } @misc{MaiwaldHierl, author = {Maiwald, Frederik and Hierl, Stefan}, title = {Absorberfreies Laser-Durchstrahlschweißen transparenter Kunststoffe}, series = {InnovationForum Medizintechnik, Tuttlingen, 24.10.2019}, journal = {InnovationForum Medizintechnik, Tuttlingen, 24.10.2019}, language = {de} } @inproceedings{MeisnerForstnerKaftiranisetal., author = {Meisner, Dennis and Forstner, Lukas and Kaftiranis, Nikitas and Hierl, Stefan}, title = {Investigation of process improvements through laser preheating in extrusion-based additive manufacturing process}, series = {Lasers in Manufacturing Conference (LIM 2023), 26. Juni bis 29. Juni 2023, M{\"u}nchen}, booktitle = {Lasers in Manufacturing Conference (LIM 2023), 26. Juni bis 29. Juni 2023, M{\"u}nchen}, publisher = {Wissenschaftliche Gesellschaft Lasertechnik und Photonik e.V. (WLT)}, pages = {10}, abstract = {Fused layer modeling (FLM) is widely used and is gaining more acceptance in the industry mainly due to its material variety and low costs. However, the usage is limited by a process-related anisotropy of the produced parts. The strength and ductility of the printed parts are significantly lower in the build-up direction than perpendicular to it. This is caused by insufficient interlayer bonding resulting from a reduced surface temperature in the process zone. To overcome this problem, a diode laser is integrated into the conventional FLM process to increase the surface temperature between the already printed surface and the newly applied substrate directly at the deposition zone. The investigations carried out show a significant improvement in the mesostructure, as well as a clear reduction in the anisotropy of the printed test specimens.}, language = {en} } @article{MaiwaldRoiderSchmidtetal., author = {Maiwald, Frederik and Roider, Clemens and Schmidt, Michael and Hierl, Stefan}, title = {Optical Coherence Tomography for 3D Weld Seam Localization in Absorber-Free Laser Transmission Welding}, series = {Applied Sciences}, volume = {12}, journal = {Applied Sciences}, number = {5}, publisher = {MPDI}, address = {Basel}, doi = {10.3390/app12052718}, pages = {1 -- 11}, abstract = {Quality and reliability are of the utmost importance for manufacturing in the optical and medical industries. Absorber-free laser transmission welding enables the precise joining of identical polymers without additives or adhesives and is well-suited to meet the demands of the aforementioned industries. To attain sufficient absorption of laser energy without absorbent additives, thulium fiber lasers, which emit in the polymers' intrinsic absorption spectrum, are used. Focusing the laser beam with a high numerical aperture provides significant intensity gradients inside the workpiece and enables selective fusing of the internal joining zone without affecting the surface of the device. Because seam size and position are crucial, the high-quality requirements demand internal weld seam monitoring. In this work, we propose a novel method to determine weld seam location and size using optical coherence tomography. Changes in optical material properties because of melting and re-solidification during welding allow for weld seam differentiation from the injection-molded base material. Automatic processing of the optical coherence tomography data enables the identification and measurement of the weld seam geometry. The results from our technique are consistent with microscopic images of microtome sections and demonstrate that weld seam localization in polyamide 6 is possible with an accuracy better than a tenth of a millimeter.}, language = {en} } @article{MaiwaldKrothGeigeretal., author = {Maiwald, Frederik and Kroth, Lea and Geiger, Ren{\´e} and Schmitt, Bernhard and Hierl, Stefan and Schmidt, Michael}, title = {Laser welding of polymer foils with spatially adapted intensity distributions}, series = {Joining Plastics}, journal = {Joining Plastics}, number = {1}, publisher = {DVS Media}, address = {D{\"u}sseldorf}, issn = {1864-3450}, doi = {10.53192/JP20250146}, pages = {46 -- 52}, abstract = {Absorber-free laser transmission welding is characterized by its contactless energy input and geometricflexibility and enables the precise and clean joining of polymer films without absorbing additives or adhesives. It is therefore well suited for applications with high demands regarding process reliability and cleanliness such as packaging, fluid containersor as sealing film in medicaland food industry. A homogeneous weld seam temperature is necessary for a large processwindow. In this work, the naturally Gaussian-shaped intensity distributionof the laser beam is there foreconverted into a donut-shaped and a flat-top-shaped distribution. When using the donut-shape, the processwindow for welding polypropylene or polyethylene films is increased by up to a factor of 3. At the same time, the weld seam strength almost corresponds to the strength of the base material.}, subject = {Laserschweissen}, language = {en} } @misc{MaiwaldDzaficHierl, author = {Maiwald, Frederik and Dzafic, Adelisa and Hierl, Stefan}, title = {Messung der Schmelzefließgeschwindigkeit beim Laser-Durchstrahlschweißen von Kunststoffen}, series = {Laser in der Elektronikproduktion \& Feinwerktechnik - LEF 2021, Erlangen, 22.04.2021}, journal = {Laser in der Elektronikproduktion \& Feinwerktechnik - LEF 2021, Erlangen, 22.04.2021}, subject = {Laserdurchstrahlschweissen}, language = {de} } @article{DzaficMaiwaldHierl, author = {Dzafic, Adelisa and Maiwald, Frederik and Hierl, Stefan}, title = {Messung der Schmelzefließgeschwindigkeit beim Laser-Durchstrahlschweißen von Kunststoffen}, series = {Werkstoffe in der Fertigung}, volume = {57}, journal = {Werkstoffe in der Fertigung}, number = {3}, publisher = {HW-Verl.}, address = {Mering}, issn = {0939-2629}, pages = {31 -- 33}, subject = {Laserdurchstrahlschweissen}, language = {de} }