@article{HofmannHierl, author = {Hofmann, A. and Hierl, Stefan}, title = {Kontrolliertes Laserdurchstrahlschweißen}, series = {Kunststoffe}, volume = {95}, journal = {Kunststoffe}, number = {6}, publisher = {Hanser}, pages = {36 -- 38}, abstract = {Obwohl das Laserdurchstrahlschweißen sehr reproduzierbar arbeitet, k{\"o}nnen Fehler aus den Vorprozessen Compoundieren, Spritzgießen etc. das Schweißergebnis negativ beeinflussen. Dem Anwender steht inzwischen eine breite Palette an Prozess{\"u}berwachungsmethoden zur Verf{\"u}gung, um eine gleich bleibende Produktqualit{\"a}t zu erzielen.}, 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} } @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 = {01}, pages = {57}, language = {de} } @inproceedings{SchmailzlQuandtHierletal., author = {Schmailzl, Anton and Quandt, Benjamin and Hierl, Stefan and Schmidt, Michael}, title = {Correlation between Joint Strength and Process Temperature in Quasi-Simultaneous Laser Transmission Welding of Polyamide 6}, series = {Proceedings of LiM2019 - Lasers in Manufacturing (23 June 2019, Munich)}, booktitle = {Proceedings of LiM2019 - Lasers in Manufacturing (23 June 2019, Munich)}, publisher = {Wissenschaftliche Gesellschaft Lasertechnik e.V.}, pages = {1 -- 10}, abstract = {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.}, language = {en} } @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} } @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} } @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{SchmailzlKaesbauerMartanetal., author = {Schmailzl, Anton and K{\"a}sbauer, Johannes and Martan, Jiř{\´i} and Honnerov{\´a}, Petra and Sch{\"a}fer, Felix and Fichtl, Maximilian and Lehrer, Tobias and Pruš{\´a}kov{\´a}, L. and Tesař, Jiř{\´i} and Sk{\´a}la, J. and Honner, Milan and Hierl, Stefan}, title = {Measurement of Core Temperature through Semi-Transparent Polyamide 6 using Scanner-Integrated Pyrometer in Laser Welding}, series = {International Journal of Heat and Mass Transfer}, volume = {146}, journal = {International Journal of Heat and Mass Transfer}, number = {January}, publisher = {Elsevier}, doi = {10.1016/j.ijheatmasstransfer.2019.118814}, abstract = {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.}, language = {en} } @inproceedings{MaiwaldEnglmaierHierl, author = {Maiwald, Frederik and Englmaier, Stephan and Hierl, Stefan}, title = {Absorber-free Laser Transmission Welding of Transparent Polymers using Fixed Focus Optics and 3D Laser Scanner}, series = {Procedia CIRP}, volume = {94}, booktitle = {Procedia CIRP}, doi = {10.1016/j.procir.2020.09.117}, pages = {686 -- 690}, abstract = {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.}, language = {en} } @inproceedings{KaesbauerSchmailzlPrehmetal., author = {K{\"a}sbauer, Johannes and Schmailzl, Anton and Prehm, Jens and Loose, Tobias and Hierl, Stefan}, title = {Simulation of Quasi-Simultaneous Laser Transmission Welding of Plastics}, series = {Procedia CIRP}, volume = {94}, booktitle = {Procedia CIRP}, doi = {10.1016/j.procir.2020.09.136}, pages = {737 -- 741}, abstract = {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.}, subject = {Kunststoffschweißen}, language = {en} } @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{KaesbauerSchmailzlWeberetal., author = {K{\"a}sbauer, Johannes and Schmailzl, Anton and Weber, Ulrich and Hierl, Stefan and Jaus, Tobias and Schwalme, Michael}, title = {Simulationsgest{\"u}tzte Evaluierung von Strahloszillationsmustern beim quasi-simultanen Laser-Durchstrahlschweißen}, series = {JOINING PLASTICS - F{\"u}gen von Kunststoffen}, volume = {13}, journal = {JOINING PLASTICS - F{\"u}gen von Kunststoffen}, number = {2}, pages = {102 -- 109}, 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} } @inproceedings{KaesbauerSchmailzlHierl, author = {K{\"a}sbauer, Johannes and Schmailzl, Anton and Hierl, Stefan}, title = {Simulationsgest{\"u}tzte Prozessentwicklung beim Laser Durchstrahlschweißen von Thermoplasten ohne absorbierende F{\"u}llstoffe}, series = {36. CADFEM ANSYS Simulation Conference, 10.-12. Oktober 2018, Leipzig}, booktitle = {36. CADFEM ANSYS Simulation Conference, 10.-12. Oktober 2018, Leipzig}, pages = {1 -- 9}, language = {de} } @inproceedings{HuentelmannHierl, author = {H{\"u}ntelmann, Sven and Hierl, Stefan}, title = {Methodisches Vorgehen bei der Topologieoptimierung additiv gefertigter Bauteile}, series = {Technikforum 3D Druck - Innovative Ans{\"a}tze f{\"u}r Bauteiloptimierung, Design und Konstruktion. Technologie Centrum Westbayern, 27.11.2018}, booktitle = {Technikforum 3D Druck - Innovative Ans{\"a}tze f{\"u}r Bauteiloptimierung, Design und Konstruktion. Technologie Centrum Westbayern, 27.11.2018}, language = {de} } @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} } @techreport{SchillingerGoerlachHierl, author = {Schillinger, Moritz and G{\"o}rlach, Julien and Hierl, Stefan}, title = {Erstellung eines Konstruktionskatalogs f{\"u}r die additive Fertigung}, series = {Forschung 2018}, journal = {Forschung 2018}, editor = {Baier, Wolfgang}, organization = {Ostbayerische Technische Hochschule Regensburg}, pages = {70 -- 71}, abstract = {Die additive Fertigung bietet vielf{\"a}ltige M{\"o}glichkeiten hinsichtlich der Bauteilgestaltung. Jedoch sind auch bei den generativen Fertigungsverfahren konstruktive Randbedingungen zu beachten, um Bauteile kosteng{\"u}nstig und mit optimalen Eigenschaften herzustellen. Es ist bereits umfangreiche Fachliteratur erh{\"a}ltlich, die entsprechende Konstruktionsempfehlungen gibt. Um Produktentwickler bedarfsgerecht zu unterst{\"u}tzen, ist jedoch ein Nachschlagewerk erforderlich, das mit geeigneter Systematik Konstruktionsvorschl{\"a}ge ausgibt, die zur aktuellen Problemstellung passen. Aufbauend auf dem Stand der Technik, eigenen Analysen und experimentellen Untersuchungen werden erste Ans{\"a}tze f{\"u}r ein solches Nachschlagewerk vorgestellt.}, subject = {Rapid prototyping}, language = {de} } @techreport{Hierl, author = {Hierl, Stefan}, title = {Forschungsschwerpunkte im Labor Lasermaterialbearbeitung}, series = {Forschungsbericht 2017}, journal = {Forschungsbericht 2017}, editor = {Baier, Wolfgang}, organization = {Ostbayerische Technische Hochschule Regensburg}, pages = {56 -- 57}, abstract = {Durch das Laserkunststoffschweißen k{\"o}nnen sowohl filigrane N{\"a}hte in der Mikrotechnik als auchtragf{\"a}hige Verbindungen f{\"u}r Strukturbauteile hergestellt werden. In der Automotiv- oder der Medizintechnik-Industrie ist diese F{\"u}getechnologie mittlerweile etabliert, jedoch sind die Anwen-dungsm{\"o}glichkeiten bei Weitem noch nicht ausgesch{\"o}pft. In k{\"u}rzlich gestarteten Forschungsprojekten mit regionalen Industrieunternehmen und internationalen Forschungspartnern werden im Labor Lasermaterialbearbeitung weitere Potenziale gehoben.}, subject = {Laserschweissen}, language = {de} } @inproceedings{SchmailzlStegerHierl, author = {Schmailzl, Anton and Steger, Sebastian and Hierl, Stefan}, title = {Herausforderungen bei der Integration einer pyrometrischen Temperaturmesstechnik in 3D-Laserscansysteme}, series = {Photonikseminar Kalibrierung des 2D- und 3D-Arbeitsfeldes von Laser-Scan-Systemen, 31.Mai 2017}, booktitle = {Photonikseminar Kalibrierung des 2D- und 3D-Arbeitsfeldes von Laser-Scan-Systemen, 31.Mai 2017}, editor = {bayern photonics e.V., and Bayerisches Laserzentrum GmbH,}, address = {N{\"u}rnberg}, pages = {48 -- 56}, language = {de} } @article{QuandtSchaeferHierl, author = {Quandt, Benjamin and Sch{\"a}fer, Felix and Hierl, Stefan}, title = {Heiße Infos aus schwachem Temperatursignal}, series = {Kunststoffe}, journal = {Kunststoffe}, number = {12}, publisher = {Hanser}, address = {M{\"u}nchen}, issn = {0945-0084}, pages = {65 -- 68}, language = {de} } @inproceedings{SchmailzlStegerDostaleketal., author = {Schmailzl, Anton and Steger, Sebastian and Dostalek, Michael and Hierl, Stefan}, title = {Online process monitoring at quasi-simultaneous laser transmission welding using a 3D-scanner with integrated pyrometer}, series = {Proc. SPIE, Laser-based Micro- and Nanoprocessing X, SPIE LASE 2016, San Francisco, California, United States}, booktitle = {Proc. SPIE, Laser-based Micro- and Nanoprocessing X, SPIE LASE 2016, San Francisco, California, United States}, number = {97361J}, editor = {Klotzbach, U. and Washio, K. and Arnold, C. B.}, doi = {10.1117/12.2211705}, pages = {1 -- 7}, abstract = {Quasi-simultaneous laser transmission welding is a well-known joining technique for thermoplastics and mainly used in the automotive as well as in the medical industry. For process control usually the so called set-path monitoring is used, where the weld is specified as "good" if the irradiation time is inside a defined confidence interval. However, the detection of small-sized gaps or thermal damaged zones is not possible with this technique. The analyzation of the weld seam temperature during welding offers the possibility to overcome this problem. In this approach a 3D-scanner is used instead of a scanner with flat-field optic. By using a pyrometer in combination with a 3D-scanner no color-corrected optic is needed in order to provide that laser- and detection-spot are concentric. Experimental studies on polyethylene T-joints have shown that the quality of the signal is adequate, despite the use of an optical setup with a long working distance and a small optical aperture. The effects on temperature are studied for defects like a gap in the joining zone. Therefore a notch was milled into the absorbent polymer. In case of producing housings for electronic parts the effect of an electrical wire between the joining partners is also investigated. Both defects can be identified by a local temperature deviation even at a feed rate of four meters per second. Furthermore a strategy for signal-processing is demonstrated. By this, remaining defects can be identified. Consequently an online detection of local defects is possible, which makes a dynamic process control feasible.}, language = {en} } @inproceedings{SchmailzlHierl, author = {Schmailzl, Anton and Hierl, Stefan}, title = {Rechenzeitoptimierte Temperaturfeldberechnung beim quasisimultanen Laser-Durchstrahlschweißen}, series = {ANSYS Conference \& 33. CADFEM Users' Meeting 2015, 24.-26. Juni 2015, Bremen, Germany}, booktitle = {ANSYS Conference \& 33. CADFEM Users' Meeting 2015, 24.-26. Juni 2015, Bremen, Germany}, editor = {CADFEM GmbH, and ANSYS Germany GmbH,}, address = {Grafing bei M{\"u}nchen}, pages = {1 -- 15}, abstract = {Beim quasisimultanen Laser-Durchstrahlschweißen von Kunststoffen wird bisher die FEM-Simulation wegen der Vielzahl von Uml{\"a}ufen des Laserstrahls und der damit verbundenen hohen Rechenzeit kaum eingesetzt. Um die Temperaturfeldberechnung zur Prozessauslegung und -optimierung praktikabel nutzen zu k{\"o}nnen, ist eine Reduktion der Rechenzeit zwingend erforderlich. Zur Simulation von Schweißvorg{\"a}ngen in ANSYS-CLASSIC werden die thermischen Lasten mithilfe von Ersatzw{\"a}rmequellen auf Basis von APDL-Routinen berechnet. Im Gegensatz dazu wird in dieser Arbeit eine analytische Lastfunktion zur Berechnung der thermischen Last f{\"u}r das quasismultane Laser-Durchstrahlschweißen vorgestellt. Im Vergleich zur Temperaturfeldberechnung mit Ersatzw{\"a}rmequelle kann bei der Berechnung eines dreidimensionalen Modells die Rechenzeit von mehreren Wochen auf wenige Stunden und f{\"u}r ein zweidimensionales auf nur wenige Minuten reduziert werden.}, language = {de} } @techreport{StegerSchmailzlDostaleketal., author = {Steger, Sebastian and Schmailzl, Anton and Dostalek, Michael and Armbruster, Dominik and Hierl, Stefan}, title = {Entwicklung einer Systemtechnik f{\"u}r das quasisimultane Laser-Durchstrahlschweißen von 3D-Kunststoffbauteilen mit Temperaturmessung und Spanndruckregelung}, series = {OTH Forschungsbericht 2016}, journal = {OTH Forschungsbericht 2016}, editor = {Baier, Wolfgang}, publisher = {Inixmedia GmbH}, address = {Kiel}, organization = {Ostbayerische Technische Hochschule Regensburg}, pages = {37 -- 38}, language = {de} } @inproceedings{SchmailzlArmbrusterDostaleketal., author = {Schmailzl, Anton and Armbruster, Dominik and Dostalek, Michael and Steger, Sebastian and Hierl, Stefan}, title = {Strahlf{\"u}hrungs- und -formungskonzept zur koaxialen Temperaturmessung beim scanner-basierten Laser-Durchstrahlschweißen}, series = {2. OTH-Clusterkonferenz, 18. Januar 2017, Techbase, Regensburg, Tagungsband}, booktitle = {2. OTH-Clusterkonferenz, 18. Januar 2017, Techbase, Regensburg, Tagungsband}, editor = {Falter, Thomas}, publisher = {Weber Druck}, address = {Regensburg}, organization = {Ostbayerische Technische Hochschule Regensburg; Ostbayerische Technische Hochschule Amberg-Weiden}, pages = {201 -- 204}, language = {de} } @inproceedings{ArmbrusterHierl, author = {Armbruster, Dominik and Hierl, Stefan}, title = {Berechnung des Messstrahlengangs f{\"u}r die in einen 3D-Scanner integrierte, pyrometrische Temperaturmessung beim quasisimultanen Laserdurchstrahlschweißen von Kunststoffen}, series = {DVS Congress 2016, Große Schweißtechnische Tagung, DVS Studentenkongress. Vortr{\"a}ge der Veranstaltungen in Leipzig am 19. und 20. September 2016}, booktitle = {DVS Congress 2016, Große Schweißtechnische Tagung, DVS Studentenkongress. Vortr{\"a}ge der Veranstaltungen in Leipzig am 19. und 20. September 2016}, publisher = {DVS Media}, address = {D{\"u}sseldorf}, pages = {165 -- 169}, language = {de} } @inproceedings{SchmailzlHierl, author = {Schmailzl, Anton and Hierl, Stefan}, title = {Scanner-integrierte Temperaturmesstechnik beim Laser-Durchstrahlschweißen}, series = {Laser in der Elektronikproduktion \& Feinwerktechnik - LEF 2017, Tagungsband des 20. Seminars LEF 2017, 07.-08. M{\"a}rz 2017}, booktitle = {Laser in der Elektronikproduktion \& Feinwerktechnik - LEF 2017, Tagungsband des 20. Seminars LEF 2017, 07.-08. M{\"a}rz 2017}, editor = {Schmidt, Michael and Roth, S.}, address = {F{\"u}rth}, pages = {181 -- 192}, language = {de} } @techreport{SchmailzlHierl, author = {Schmailzl, Anton and Hierl, Stefan}, title = {Rechenzeitoptimierte Temperaturfeldberechnung zur virtuellen Prozessauslegung des quasisimultanen Laser-Durchstrahlschweißens}, series = {Forschungsbericht 2014 / Ostbayerische Technische Hochschule Regensburg}, journal = {Forschungsbericht 2014 / Ostbayerische Technische Hochschule Regensburg}, editor = {Baier, Wolfgang}, publisher = {Inixmedia GmbH}, address = {Kiel}, organization = {Ostbayerische Technische Hochschule Regensburg}, pages = {75 -- 77}, language = {de} } @article{SchmailzlStegerHierl, author = {Schmailzl, Anton and Steger, Sebastian and Hierl, Stefan}, title = {Process monitoring at laser welding of Thermoplastics}, series = {Laser Technik Journal}, volume = {12}, journal = {Laser Technik Journal}, number = {4}, doi = {10.1002/latj.201500029}, pages = {34 -- 37}, abstract = {A pyrometer, integrated into a 3D-scanner, offers the possibility to measure the weld seam temperature at quasi-simultaneous laser transmission welding. Experimental studies have shown that gaps located in the joining zone can be identified by a temperature rise even at a high scanning velocity. This enables the implementation of algorithms for observation and control strategies.}, language = {en} } @article{DostalekStegerSchmailzletal., author = {Dostalek, Michael and Steger, Sebastian and Schmailzl, Anton and Hierl, Stefan}, title = {Detecting Defects Reliably}, series = {Kunststoffe International}, volume = {105}, journal = {Kunststoffe International}, number = {12}, pages = {37 -- 40}, abstract = {The integration of a broadband pyrometer in a 3-D scanner enables a continuous and local temperature measurement during the quasi-simultaneous laser transmission welding process. Welding tests on polyethylene samples show that defects can be clearly identified based on the temperature signal, despite a high scanning velocity.}, language = {en} } @misc{SchmailzlHierl, author = {Schmailzl, Anton and Hierl, Stefan}, title = {FE-Modellbildung der Strahl-Stoff-Wechselwirkung beim Laser-Durchstrahlschweißen in ANSYS 14.0}, series = {ANSYS Conference \& 32th CADFEM Users' Meeting 2014, 04.-06. Juni, N{\"u}rnberg}, journal = {ANSYS Conference \& 32th CADFEM Users' Meeting 2014, 04.-06. Juni, N{\"u}rnberg}, editor = {CADFEM GmbH, and ANSYS Germany GmbH,}, address = {Grafing bei M{\"u}nchen}, pages = {1 -- 15}, language = {de} } @techreport{TalbotHierlSchmailzl, author = {Talbot, Sebastian and Hierl, Stefan and Schmailzl, Anton}, title = {Thermische FEM-Simulation des Laser-Durchstrahlschweißens}, series = {Forschungsbericht 2013}, journal = {Forschungsbericht 2013}, editor = {Baier, Wolfgang}, address = {Kiel}, organization = {Ostbayerische Technische Hochschule Regensburg}, pages = {45 -- 46}, language = {de} } @article{StegerDostalekSchmailzletal., author = {Steger, Sebastian and Dostalek, Michael and Schmailzl, Anton and Hierl, Stefan}, title = {Fehlstellen sicher erkennen}, series = {Kunststoffe}, volume = {105}, journal = {Kunststoffe}, number = {12}, pages = {55 -- 58}, language = {de} } @inproceedings{Hierl, author = {Hierl, Stefan}, title = {Laser Transmission Welding of Plastics}, series = {15th International Materials Symposium - IMSP'2014, Denizli, 2014}, booktitle = {15th International Materials Symposium - IMSP'2014, Denizli, 2014}, editor = {Meran, Cemal}, pages = {1084 -- 1093}, language = {en} } @incollection{SchmailzlHuentelmannLooseetal., author = {Schmailzl, Anton and H{\"u}ntelmann, Sven and Loose, Tobias and K{\"a}sbauer, Johannes and Maiwald, Frederik and Hierl, Stefan}, title = {Potentials of the ALE-Method for Modeling Plastics Welding Processes, in Particular for the Quasi-Simultaneous Laser Transmission Welding}, series = {Mathematical Modelling of Weld Phenomena 12}, booktitle = {Mathematical Modelling of Weld Phenomena 12}, editor = {Sommitsch, Christof and Enzinger, Norbert and Mayr, Peter}, publisher = {Verlag der Technischen Universit{\"a}t Graz}, address = {Graz}, doi = {10.3217/978-3-85125-615-4-51}, pages = {965 -- 975}, abstract = {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.}, language = {en} } @inproceedings{SchmailzlHierlSchmidt, author = {Schmailzl, Anton and Hierl, Stefan and Schmidt, Michael}, title = {Gap-Bridging during Quasi-Simultaneous Laser Transmission Welding}, series = {Physics Procedia}, volume = {83}, booktitle = {Physics Procedia}, editor = {Schmidt, Michael}, publisher = {Elsevier}, address = {Amsterdam [u.a.]}, issn = {1875-3892}, doi = {10.1016/j.phpro.2016.08.113}, pages = {1073 -- 1082}, abstract = {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.}, language = {en} } @inproceedings{SchmailzlAmannGlockneretal., author = {Schmailzl, Anton and Amann, Thomas and Glockner, Markus and Fandanelli, Martin and Wagner, Marcus and Hierl, Stefan}, title = {Finite element analysis of thermoplastic probes under tensile load using ls-dyna compared to ansys workbench 14 in correlation to experimental investigations}, series = {ANSYS Conference \& 30th CADFEM Users' Meeting - ACUM, 24.-26- Oktober 2012, Kassel}, booktitle = {ANSYS Conference \& 30th CADFEM Users' Meeting - ACUM, 24.-26- Oktober 2012, Kassel}, editor = {CADFEM GmbH, and ANSYS Germany GmbH,}, address = {Grafing bei M{\"u}nchen}, pages = {1 -- 10}, abstract = {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}, language = {en} } @inproceedings{SchmailzlQuandtSchmidtetal., author = {Schmailzl, Anton and Quandt, Benjamin and Schmidt, Michael and Hierl, Stefan}, title = {In-Situ Process Monitoring during Laser Transmission Welding of PA6-GF30}, series = {Procedia CIRP}, volume = {74}, booktitle = {Procedia CIRP}, doi = {10.1016/j.procir.2018.08.131}, pages = {524 -- 527}, abstract = {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.}, language = {en} } @inproceedings{SchmailzlHierl, author = {Schmailzl, Anton and Hierl, Stefan}, title = {Thermo-mechanische Struktursimulation mit ANSYS Workbench 14.0 am Beispiel des Laser-Durchstrahlschweißens}, series = {ANSYS Conference \& 31st CADFEM Users' Meeting - ACUM, June 19-21, Mannheim}, booktitle = {ANSYS Conference \& 31st CADFEM Users' Meeting - ACUM, June 19-21, Mannheim}, editor = {CADFEM GmbH, and ANSYS Germany GmbH,}, address = {Grafing bei M{\"u}nchen, Darmstadt}, pages = {1 -- 16}, language = {de} } @article{SchmailzlHierlSiebenetal., author = {Schmailzl, Anton and Hierl, Stefan and Sieben, Manuel and Brunnecker, Frank}, title = {Optimierung der Spanndruckverteilung beim Laserdurchstrahlschweißen komplexer Bauteile mittels FE-Berechnung}, series = {JOINING PLASTICS}, volume = {7}, journal = {JOINING PLASTICS}, number = {1}, pages = {30 -- 34}, language = {de} } @incollection{SchmailzlHierl, author = {Schmailzl, Anton and Hierl, Stefan}, title = {Online-Prozess{\"u}berwachung beim Quasi-Simultanen Laser-Durchstrahlschweißen von Kunststoffen}, series = {Young Professionals - Jugend forscht und schweisst}, booktitle = {Young Professionals - Jugend forscht und schweisst}, editor = {GSI Niederlassung SLV M{\"u}nchen,}, pages = {1 -- 7}, language = {de} } @article{MaiwaldEnglmaierHierl, author = {Maiwald, Frederik and Englmaier, Stephan and Hierl, Stefan}, title = {Online pyrometry for weld seam localization in absorber-free laser transmission welding of transparent polymers}, series = {Journal of Laser Micro/Nanoengineering}, volume = {Vol. 16}, journal = {Journal of Laser Micro/Nanoengineering}, number = {1}, publisher = {Japan Laser Processing Society}, issn = {1880-0688}, doi = {10.2961/jlmn.2021.01.2002}, pages = {8 -- 13}, abstract = {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.}, subject = {Laserdurchstrahlschweissen}, language = {en} } @article{MaiwaldHierl, author = {Maiwald, Frederik and Hierl, Stefan}, title = {Pyrometerbasierte Prozess{\"u}berwachung beim Laserkunststoffschweißen}, series = {Photonik}, journal = {Photonik}, number = {52}, publisher = {AT-Fachverl.}, address = {Fellbach}, pages = {22 -- 25}, subject = {Laserschweissen}, language = {de} } @article{MaiwaldHierl, author = {Maiwald, Frederik and Hierl, Stefan}, title = {Absorber-free laser transmission welding of transparent polymers}, series = {Laser Systems Europe}, volume = {50}, journal = {Laser Systems Europe}, number = {Spring 2021}, publisher = {Europa Science}, address = {Cambridge}, language = {en} } @article{ReindlMeisnerHierl, author = {Reindl, Thomas and Meisner, Dennis and Hierl, Stefan}, title = {Benchmarking of plastic-based Additive Manufacturing Processes}, series = {RTe Journal}, journal = {RTe Journal}, abstract = {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.}, language = {en} } @inproceedings{SchmailzlGeisslerMaiwaldetal., author = {Schmailzl, Anton and Geißler, Bastian and Maiwald, Frederik and Laumer, Tobias and Schmidt, Michael and Hierl, Stefan}, title = {Transformation of Weld Seam Geometry in Laser Transmission Welding by Using an Additional Integrated Thulium Fiber Laser}, series = {Lasers in Manufacturing - LIM 2017, Conference Proceedings}, booktitle = {Lasers in Manufacturing - LIM 2017, Conference Proceedings}, editor = {Esen, Cermal}, address = {M{\"u}nchen}, pages = {1 -- 10}, language = {en} } @inproceedings{MaiwaldTroegerHierl, author = {Maiwald, Frederik and Tr{\"o}ger, Johannes and Hierl, Stefan}, title = {Automated weld seam evaluation and 2D simulation parameter calibration for absorber-free laser transmission welding}, 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 = {Absorber-free laser transmission welding enables clean and precise joining of plastics without additives or adhesives. It is therefore well suited to produce optical and medical devices, which place high demands on cleanliness and accuracy. However, the weld usually has an undesirably large vertical expansion, causing bulges and distortion. To improve this, the intensity distribution of the laser beam as well as the processing strategy must be adapted. Due to the complexity, this is aided by process simulation. However, simulation parameter calibration and verification are usually done considering the seam width and height, which is of limited significance. To overcome this, we propose a new method for image processing of microtome sections, determining the spatially resolved geometry of the weld. Thus, the deviation between experiment and simulation can be calculated pixel by pixel. This spatially resolved value is predestined for the calibration of the simulation parameters: For a parameter field with 18 different settings, the total deviation between experiment and simulation is less than 11 \% after calibration.}, language = {en} } @book{Schmailzl, author = {Schmailzl, Anton}, title = {Festigkeits- und zeitoptimierte Prozessf{\"u}hrung beim quasi-simultanen Laser-Durchstrahlschweißen}, editor = {Franke, J{\"o}rg and Hanenkamp, Nico and Hausotte, Tino and Merklein, Marion and M{\"u}ller, Sebastian and Schmidt, Michael and Wartzack, Sandro}, publisher = {FAU University Press}, address = {Erlangen}, doi = {10.25593/978-3-96147-584-1}, pages = {xiii, 157 S.}, abstract = {Mit Blick auf Leichtbauanwendungen ist der Bedarf an thermoplastischen Strukturbauteilen sowohl in der Automobil- als auch in der Luftfahrtindustrie in den letzten Jahren deutlich angestiegen. Das quasi-simultane Laser-Durchstrahlschweißen ist ein etabliertes Kunststoffschweißverfahren, welches jedoch zur Herstellung von tragenden und sicherheitsrelevanten Bauteilen bislang kaum in Betracht gezogen wird. In der vorliegenden Arbeit wird die Korrelation zwischen dem Prozessablauf und der Schweißnahtfestigkeit beim quasi-simultanen Laser-Durchstrahlschweißen von Polyamid 6 (Ultramid B3s) erstmalig untersucht. Zur Prozessanalyse wird ein 3D-Scanner mit integriertem Pyrometer realisiert und f{\"u}r die Messaufgabe kalibriert. Es wird gezeigt, dass die detektierte W{\"a}rmestrahlung dem Kern der Schweißnaht zuzuordnen ist. Die Kerntemperatur in der quasi-station{\"a}ren Prozessphase steht in direkter Korrelation mit der Schweißnahtfestigkeit. Mit steigender Kerntemperatur bzw. Molek{\"u}lbeweglichkeit erh{\"o}ht sich die Wahrscheinlichkeit der Bildung von Molek{\"u}l-Verschlaufungen in der F{\"u}geebene. Zur Ermittlung der Kerntemperatur ist sowohl die in dieser Arbeit entwickelte Temperaturmesstechnik als auch die realisierte numerische Prozesssimulation nutzbar. Die Erkenntnisse in dieser Arbeit sind f{\"u}r eine festigkeits- und zeitoptimierten Prozessf{\"u}hrung des quasi-simultanen Laser-Durchstrahlschweißens nutzbar.}, language = {de} } @inproceedings{MaiwaldEnglmaierHierl, author = {Maiwald, Frederik and Englmaier, Stephan and Hierl, Stefan}, title = {Online pyrometry for weld seam localization in absorber-free laser transmission welding of transparent polymers}, series = {21st International Symposium on Laser Precision Microfabrication: Dresden, 26.06.2020}, booktitle = {21st International Symposium on Laser Precision Microfabrication: Dresden, 26.06.2020}, abstract = {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.}, subject = {Laserdurchstrahlschweissen}, language = {en} } @misc{Armbruster, author = {Armbruster, Dominik}, title = {Optimization of a system technology for coaxial online pyrometry in three-dimensional laser transmission welding}, series = {Applied Research Conference 2015 ARC 2015 ; 3rd July 2015 N{\"u}rnberg}, journal = {Applied Research Conference 2015 ARC 2015 ; 3rd July 2015 N{\"u}rnberg}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Scharfenberg, Georg and Ziemann, Olaf}, publisher = {pro Business GmbH}, address = {Berlin}, pages = {314 -- 317}, language = {en} } @inproceedings{DostalekHierl, author = {Dostalek, Michael and Hierl, Stefan}, title = {Experimental study to evaluate the influence of clamping pressure variation during laser transmission welding of plastics}, series = {Applied Research Conference 2015 ARC 2015; 3rd July 2015 N{\"u}rnberg}, booktitle = {Applied Research Conference 2015 ARC 2015; 3rd July 2015 N{\"u}rnberg}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Scharfenberg, Georg and Ziemann, Olaf}, publisher = {pro Business}, address = {Berlin}, pages = {289 -- 294}, language = {en} } @inproceedings{PreischlSchmailzlHierl, author = {Preischl, Antonius and Schmailzl, Anton and Hierl, Stefan}, title = {Experimental study to evaluate the process window for laser transmission welding of plastics}, series = {Applied Research Conference 2014 - ARC 2014, 5th July 2014, Ingolstadt}, booktitle = {Applied Research Conference 2014 - ARC 2014, 5th July 2014, Ingolstadt}, editor = {Ziemann, Olaf and Mottok, J{\"u}rgen and Pforr, Johannes}, publisher = {Shaker}, address = {Aachen}, pages = {517 -- 522}, language = {en} } @inproceedings{Quandt, author = {Quandt, Benjamin}, title = {Effect of the Detection Spot Size on pyrometric Temperature Signal at quasi-simultaneous Laser Transmission Welding}, series = {Applied Research Conference 2018, ARC 2018, 10 July 2018, Deggendorf}, booktitle = {Applied Research Conference 2018, ARC 2018, 10 July 2018, Deggendorf}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Bogner, Werner}, publisher = {pro Business GmbH}, address = {Berlin}, pages = {261 -- 264}, language = {en} } @inproceedings{Schaefer, author = {Sch{\"a}fer, Felix}, title = {Temperature Measurement with Scanner-Integrated Pyrometer during Laser Transmission Welding with Clearweld Absorber}, series = {Applied Research Conference 2018, ARC 2018, 10 July 2018, Deggendorf}, booktitle = {Applied Research Conference 2018, ARC 2018, 10 July 2018, Deggendorf}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Bogner, Werner}, publisher = {pro Business GmbH}, address = {Berlin}, pages = {258 -- 260}, language = {en} } @inproceedings{Maiwald, author = {Maiwald, Frederik}, title = {Simulation of Pyrometer Based Temperature Measurement Systems using Non-Sequential Raytracing}, series = {Applied Research Conference 2018, ARC 2018, 10 July 2018, Deggendorf}, booktitle = {Applied Research Conference 2018, ARC 2018, 10 July 2018, Deggendorf}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Bogner, Werner}, publisher = {pro Business GmbH}, address = {Berlin}, pages = {168 -- 171}, language = {en} } @inproceedings{SchmailzlHierl, author = {Schmailzl, Anton and Hierl, Stefan}, title = {Online-process monitoring of laser transmission welding for polymers}, series = {Applied Research Conference 2013, ARC 2013 ; 17th and 18th October 2013, Deggendorf}, booktitle = {Applied Research Conference 2013, ARC 2013 ; 17th and 18th October 2013, Deggendorf}, editor = {Ziemann, Olaf and Bogner, Werner and Mottok, J{\"u}rgen}, publisher = {Shaker}, address = {Aachen}, pages = {374 -- 378}, language = {en} } @misc{KaesbauerSchmailzlHierl, author = {K{\"a}sbauer, Johannes and Schmailzl, Anton and Hierl, Stefan}, title = {Simulative investigation on the influence of material- and process parameter on quasi-simultaneous laser transmission welding}, series = {Applied Research Conference - ARC 2017, 7 July 2017 M{\"u}nchen}, journal = {Applied Research Conference - ARC 2017, 7 July 2017 M{\"u}nchen}, editor = {Klippel, Clemens and Mottok, J{\"u}rgen and Reichenberger, Marcus}, publisher = {pro Business GmbH}, address = {Berlin}, language = {en} } @misc{MaiwaldSchmailzlHierl, author = {Maiwald, Frederik and Schmailzl, Anton and Hierl, Stefan}, title = {Thermo-mechanical computation of weld seam geometry in laser transmission welding}, series = {Applied Research Conference - ARC 2017, 7 July 2017, M{\"u}nchen}, journal = {Applied Research Conference - ARC 2017, 7 July 2017, M{\"u}nchen}, editor = {Klippel, Clemens and Mottok, J{\"u}rgen and Reichenberger, Marcus}, publisher = {pro Business GmbH}, address = {Berlin}, language = {en} } @inproceedings{ArmbrusterHierl, author = {Armbruster, Dominik and Hierl, Stefan}, title = {Simulation of a pyrometer-based temperature measurement system for quasi-simultaneous laser transmission welding regarding the detectable radiant power}, series = {Applied Research Conference - ARC 2016, 24 June 2016, Hochschule Augsburg, Germany}, booktitle = {Applied Research Conference - ARC 2016, 24 June 2016, Hochschule Augsburg, Germany}, editor = {Mottok, J{\"u}rgen and Reichenberger, Marcus and Stolle, Reinhard}, publisher = {Shaker}, address = {Aachen}, pages = {314 -- 317}, language = {en} } @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} } @inproceedings{MaiwaldKrothLaskinetal., author = {Maiwald, Frederik and Kroth, Lea and Laskin, Alexander and Hierl, Stefan and Schmidt, Michael}, title = {Enlarging the process window in absorber-free laser transmission welding of polymer foils using tailored laser intensity distribution}, series = {Procedia CIRP}, booktitle = {Procedia CIRP}, language = {en} }