@inproceedings{SchkutowFrick2022, author = {Schkutow, Andreas and Frick, Thomas}, title = {Laser surface structuring for metal-polymer hybrid connections using fast modulated cw-laser radiation}, publisher = {DGM - Deutsche Gesellschaft f{\"u}r Materialkunde e.V.}, address = {Sankt Augustin}, year = {2022}, abstract = {Laser direct joining of metals and plastics is a promising process for producing hybrid material joints without the need for adhesives, fasteners or additional materials [1,2]. In this process, a metallic part is structured by laser radiation to increase the surface roughness and to create undercuts. A thermoplastic or thermoplastic composite material is then brought into contact with the metal component and melted in the contact zone. The melt flows into the structures and, after cooling, a stable joint is formed. The properties of such joints strongly depend on the properties of these structures. So far, two main approaches have been used for the structuring process: By repeated irradiation with continuous laser radiation, linear grooves or grid structures can be introduced at high removal rates [3]. More complex structures with high aspect ratios can be generated with short and ultra-short pulsed laser radiation [2]. Such structures can lead to higher bond strengths, but due to the limited average power and high cost per watt of those laser systems, the process is usually much slower than with cw beam sources [2]. Modern high-power and comparatively inexpensive cw-fiber lasers feature fast optical modulation capability with modulation frequencies in the range of up to 100 kHz [4], enabling increased temporal control of the laser-material interaction by using pulses in the μs range and temporal pulse shaping. As shown in Fig. 1, surface structuring using fast modulated laser radiation was found to lead to increased melt expulsion and therefore higher removal rates compared to remote ablation cutting with continuous wave laser radiation at the same average and peak power levels. Therefore, shorter processing times and in some cases a single irradiation can be sufficient to achieve the desired structuring depth. In addition, the lower overall heat input reduces distortion in thin-walled specimens. References [1] A. Klotzbach; M. Langer; R. Pautzsch; J. Standfuß; E. Beyer; Thermal direct joining of metal to fiber reinforcedthermoplastic components. J. Laser Appl. 2017, 29, 22421. [2] K. van der Straeten; C. Engelmann; A. Olowinsky; A. Gillner; Comparison of laser-based joining approaches forplastic-metal-hybrids - Strength vs. process speed. In Proceedings of the 3rd Hybrid Conference, Bremen,Germany, 2018, pp. 203-309. [3] C. Engelmann, D. Meier, A. Olowinsky; M. Kielwasser, Metal meets Composite - Hybrid Joining for AutomotiveApplications, Lasers in Manufacturing Conference 2015, 2015. [4] D. A. V. Kliner et al.; Next-generation industrial fiber lasers enabled by high-performance components, Proc.SPIE 10513, Components and Packaging for Laser Systems IV, 2018, 105130S.}, language = {en} } @inproceedings{SchkutowFrickScholleetal.2019, author = {Schkutow, Andreas and Frick, Thomas and Scholle, Karsten and Lamrini, Samir and Fuhrberg, Peter}, title = {Experimental characterization of spectral scattering properties of polymers for laser welding applications}, series = {Proceedings of LAMP2019}, booktitle = {Proceedings of LAMP2019}, publisher = {Japan Laser Processing Society (JLPS)}, year = {2019}, abstract = {Laser transmission welding of polymers is a widely used joining technique for automotive components, consumer products, medical applications and others. The process is strongly dependent on the transmission properties of one of the joining partners to ensure a suitable laser intensity distribution in the joining zone between the two components. Scattering at crystalline structures, additives or reinforcements in composites as well as the absorptivity of the matrix can compromise the transmitted beam profile [1, 2, 3]. Successful welding of these materials is therefore often limited to thin parts. This work describes methods for measuring the spectral absorption, transmission and scattering properties to assess the weldability of scattering materials. Since many of these materials show anisotropic properties due to the manufacturing processes and the fiber orientation, the transmission properties are influenced by the polarization state of the laser beam. An experimental setup shown in Fig. 1, using a commercially available Spectrophotometer with integrating sphere, is used to measure direct transmission, forward and backward directed scattering and the reflection of linearly polarized light after interaction with amorphous and semicrystalline polymers as well as particle and fiber reinforced thermoplastic composites. The spectral measurements reveal that compared to commonly used lasers emitting at about 1.0 μm the application of laser wavelengths in the range of 1.3 to 2.0 μm can lead to increased transmission and reduced scattering losses within the materials. Variation of the polarization adds an additional degree of freedom to influence the transmission properties, especially in highly anisotropic materials or composites. For validation of the spectrometric results welding experiments using a conventional diode laser beam source and a unpolarised and a linearly polarized 2.0-μm single-mode Tm-fiber [4] were carried out. Additionally the resulting laser beam profiles after transmission through different amorphous and semicrystalline polymeric materials were measured using a scanning slit beam profiler. Using a suitable laser wavelength and adjusted polarization successful welding was achieved for highly scattering materials that could not be welded using a conventional diode laser beam source. [1] X. F. Xu, A. Parkinson, P. J. Bates and G. Zak, Effect of part thickness, glass fiber and crystallinity on light scattering during laser transmission welding of thermoplastics, Optics \& Laser Technology 75, pp. 123-131, 2015. [2] V. Mamuschkin, A. Roesner, M. Aden, Laser Transmission Welding of White Thermoplastics with Adapted Wavelengths, Physics Procedia, 41, p. 172-179, (2013). [3] T. Frick and A. Schkutow, Laser transmission welding of polymers-Irradiation strategies for strongly scattering materials. Procedia CIRP, 74, p. 538-543, (2018). [4] K. Scholle, M. Sch{\"a}fer, S. Lamrini, M. Wysmolek, M. Steinke, J. Neumann, P. Fuhrberg, All-fiber linearly polarized high power 2-μm single mode Tm-fiber laser for plastic processing and Ho-laser pumping applications, Proc. SPIE 10512, Fiber Lasers XV: Technology and Systems, 105120O, (2018).}, language = {en} } @article{GeigerSchkutow2024, author = {Geiger, Ren{\´e} and Schkutow, Andreas}, title = {Mehr Prozesssicherheit beim Laserf{\"u}gen von Kunststoffen}, series = {Laser, Photonics, Professional (LP.PRO)}, volume = {2024}, journal = {Laser, Photonics, Professional (LP.PRO)}, number = {6}, publisher = {Felchner Medien GmbH}, address = {Kaufbeuren}, pages = {22-25}, year = {2024}, abstract = {Hochleistungslaserschweißen temperaturempfindlicher Thermoplaste - was auf den ersten Blick wie ein Widerspruch aussieht, erweist sich in der Praxis als nahezu ideale Kombination. Ein neues Schweißmodul erfasst mittels Hochgeschwindigkeitspyrometer die Bauteiltemperatur in Echtzeit, um ein {\"U}berhitzen der Materialien zu verhindern.}, language = {de} } @article{GeigerSchkutow2023, author = {Geiger, Ren{\´e} and Schkutow, Andreas}, title = {Temperaturgeregeltes Laserdurchstrahlschweißen - Echtzeit-Pyrometrie f{\"u}r erh{\"o}hte Prozesssicherheit}, series = {Plastverarbeiter}, volume = {2023}, journal = {Plastverarbeiter}, number = {10}, publisher = {H{\"u}thig Medien GmbH}, address = {Heidelberg}, pages = {90-92}, year = {2023}, abstract = {Temperaturempfindliche thermoplastische Kunststoffe vertragen sich beim Schweißen durchaus mit Hochleistungslaserstrahlen. Was zun{\"a}chst wie ein Widerspruch klingt, er{\"o}ffnet mit einer Online-Temperaturregelung mittels Hochgeschwindigkeitspyrometer vielf{\"a}ltige Anwendungen in der Praxis.}, language = {de} } @inproceedings{SchkutowFrick2023, author = {Schkutow, Andreas and Frick, Thomas}, title = {Laser surface texturing of metals using dynamic melt expulsion by application of fast modulated cw-laser radiation}, series = {Proceedings of LPM2023}, volume = {2023}, booktitle = {Proceedings of LPM2023}, publisher = {Japan Laser Processing Society (JLPS)}, year = {2023}, abstract = {Laser surface texturing of metals is usually performed using pulsed laser sources. Short and ultrashort pulsed laser systems offer the highest machining quality and processing flexibility. Most of these beam sources however feature relatively low average powers or high system prices. Continuous wave fiber lasers in comparison feature high average powers at moderate costs. In this work the laser power of a continuous-wave fiber laser is rapidly modulated to investigate the possibilities to improve laser surface texturing processes by periodically changing the interaction between the sur-face tension in the melt pool and the vapor pressure created during high power laser processing. It was found that the intermittent nature of modulated continuous wave laser radiation can improve the melt expulsion from the processing area, leading to high material removal rates and ablation ef-ficiencies while also limiting the heat input into the substrate material.}, language = {en} } @article{SchkutowFrick2024, author = {Schkutow, Andreas and Frick, Thomas}, title = {Laser color marking of stainless steel - Investigation of the fluence-dependent and thermal mechanisms in generating laser induced surface modifications}, series = {Procedia CIRP}, volume = {124}, journal = {Procedia CIRP}, publisher = {Elsevier BV}, issn = {2212-8271}, doi = {10.1016/j.procir.2024.08.196}, pages = {661 -- 664}, year = {2024}, abstract = {Laser color marking is an attractive process to generate functional, aesthetic and durable colorations on various suitable metals such as stainless steel or titanium. The color generation is mainly based on interference effects on thin oxide layers, usually induced by nanosecond pulsed laser irradiation. Due to the large number of mutually influencing processing parameters and different thermal, chemical, structural and topological influences on the coloring results, the process is still not fully understood. Moreover, the reproducibility of the markings and the processing times often do not meet the requirements of industrial manufacturing processes. To improve the understanding of the underlying phenomena comparable colors are generated using different parameter sets. Spectroscopic, microscopic and SEM/EDS analyzes are carried out to investigate the effects of the surface topology, oxide layer properties, chemical composition and heat accumulation on the marking results.}, language = {en} } @article{FrickSchkutow2018, author = {Frick, Thomas and Schkutow, Andreas}, title = {Laser transmission welding of polymers - Irradiation strategies for strongly scattering materials}, series = {Procedia CIRP}, volume = {74}, journal = {Procedia CIRP}, publisher = {Elsevier BV}, issn = {2212-8271}, doi = {10.1016/j.procir.2018.08.118}, pages = {538 -- 543}, year = {2018}, abstract = {In laser transmission welding of thermoplastics the optical properties of the transparent part have great influence on the weld seam quality. Especially scattering, for example at crystalline structures or additives, can significantly affect the intensity distribution of the radiation in the joining zone. Since scattering is a strongly wavelength dependent process the right choice of the laser wavelength can enable laser transmission welding even for challenging materials. It is shown that the necessary optical material properties needed to assess the weldability of scattering materials can be directly obtained from NIR-spectroscopy.}, language = {en} } @article{SchkutowBreitFrick2025, author = {Schkutow, Andreas and Breit, Johanna and Frick, Thomas}, title = {High-speed observation of melt pool-vapor interactions in long-pulsed laser ablation of metals}, series = {Journal of Laser Applications}, volume = {38}, journal = {Journal of Laser Applications}, number = {1}, publisher = {AIP Publishing}, address = {Melville, NY}, doi = {10.2351/7.0001866}, year = {2025}, abstract = {Laser ablation of metals can be performed using cost-effective and efficient continuous wave fiber lasers using the fast power modulation capabilities of these beam sources. Single-pulse laser ablation of steel with pulse durations in the microsecond to millisecond time scale is observed using a high-speed camera setup to investigate the dynamic interactions between the generated melt pool and the vapor phase. Distinct processing regimes were identified depending on the pulse duration, temporal pulse shape, and power density. Pulse durations in the microsecond range can lead to beneficial processing conditions for ablation processes. In this regime, phase explosion and dynamic melt expulsion by melt uplift and coaxial droplet ejection due to the rapid drop in vapor pressure after the laser pulses were observed as desirable mechanisms, leading to effective material removal and high processing quality with little melt adhesion.}, language = {en} }