@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} } @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}, publisher = {Japan Laser Processing Society}, 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} } @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} } @phdthesis{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}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:29-opus4-207070}, pages = {xiii, 157}, 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} }