TY - CHAP A1 - Franz, Daniel A1 - Schuster, David A1 - Schwarz, Simon A1 - Rung, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Ultrashort pulsed laser drilling of through-glass vias for glass core packaging T2 - Proceedings of LAMP2025 – the 9th International Congress on Laser Advanced Materials Processing, Ise-City, Japan, June 2025 KW - Ultrakurzzeitlaser KW - Laserbohren Y1 - 2025 ER - TY - CHAP A1 - Sommer, David A1 - Truetsch, Ben A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Microstructural Fracture Behaviour of PBF-LB/M Inconel 718 Components within different HIP Processes T2 - Lasers in Manufacturing, München, Juni 2025 N2 - We report on a study of different hot isostatic pressing (HIP) cycles, improving the mechanical properties of additively manufactured Inconel 718 components. For this, PBF-LB/M built components are post-processed by different HIP sequences, as gas pressure and processing time are varied, leading to differences in microstructure and material characteristics. Static and dynamic mechanical testing are performed, evaluating the changes in mechanical properties with particular focus on the ultimate tensile strength and endurance limit. Furthermore, metallographic analysis is employed to investigate the achieved density and microhardness. Microstructural analysis, showing the grain boundaries, is used to identify generated phases and precipitations of the material matrix. Moreover, the fracture behaviour is classified by grain deformation during mechanical testing. As the HIP leads to microstructural changes of Inconel 718 components, mechanical properties can be improved significantly, enhancing the ultimate tensile strength and simultaneously the endurance limit. KW - Isostatisches Heißpressen Y1 - 2025 ER - TY - CHAP A1 - Sommer, David A1 - Peters, Maximilian A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Influence of in-situ high-speed milling within a hybrid additive manufacturing approach on the fatigue behaviour of Inconel 718 lattice structures T2 - Lasers in Manufacturing, München, Juni 2025 N2 - As lattice structures in various designs are used in additive manufacturing for lightweight components, the mechanical characterisation and fracture behaviour is of upmost importance for their industrial application. In this study, the fatigue behaviour of Inconel 718 lattice structures is evaluated, comparing sole PBF-LB/M to a hybrid additive manufacturing process combining PBF-LB/M with in-situ high-speed milling. At first, the static and dynamic mechanical load behaviour of different packing densities is analysed, determining the compressive strength and the endurance limit. Secondly, hybrid additive manufactured components are compared to PBF-LB/M built parts with respect to these mechanical properties, revealing improved compressive properties and modified regimes of fatigue. In addition, differences in fracture behaviour are qualified by fractographic and surface analysis. Overall, it can be summarized that the mechanical load characteristics, especially the fatigue behaviour, are improved for hybrid additively manufactured components with a superior surface quality of Ra < 1 µm. KW - Hochgeschwindigkeitsfräsen Y1 - 2025 ER - TY - CHAP A1 - Sommer, David A1 - Hornung, Simon A1 - Esen, Cemal A1 - Hellmann, Ralf ED - Gu, Bo ED - Chen, Hongqiang T1 - Optimization of mechanical properties of additive manufactured IN 718 parts combining LPBF and in-situ high-speed milling T2 - Laser 3D Manufacturing XI KW - Hybrid additive manufacturing KW - High-speed Milling KW - Hot isostatic pressing KW - Fatigue behaviour KW - Hochgeschwindigkeitsfräsen Y1 - 2024 U6 - https://doi.org/http://dx.doi.org/10.1117/12.3000952 PB - SPIE ER - TY - CHAP A1 - Sommer, David A1 - Safi, Abdulrahman A1 - Esen, Cemal A1 - Hellmann, Ralf ED - Gu, Bo ED - Chen, Hongqiang T1 - Additive manufacturing of Nickel-based superalloy: optimization of surface roughness using integrated high-speed milling T2 - Laser 3D Manufacturing XI KW - Hochgeschwindigkeitsfräsen Y1 - 2024 U6 - https://doi.org/http://dx.doi.org/10.1117/12.3000972 PB - SPIE ER - TY - CHAP A1 - Lutz, Christian A1 - Sommerhuber, Ryan A1 - Kettner, Matthias A1 - Esen, Cemal A1 - Hellmann, Ralf ED - Kling, Rainer ED - Pfleging, Wilhelm ED - Sugioka, Koji T1 - Towards process control by detecting acoustic emissions during ultrashort pulsed laser ablation of multilayer materials T2 - Laser-based Micro- and Nanoprocessing XVIII N2 - We report on process sensing using a membrane-free optical microphone to monitor the acoustic emission during ultrashort pulsed laser ablation of multilayer materials. The acoustic emission during ablation is used to detect material transitions, with the specific signatures allowing to create a reliable process control for identifying individual layers. The outstanding properties of membrane-free optical microphones in terms of high bandwidth and high temporal resolution are ideally qualified for characterizing an ultrashort pulsed laser process, with its properties and capabilities being presented in this contribution. In particular, for layer- and material-selective ablation of multilayer printed circuit board components, copper and polyimide layers are ablated and the material transition is detected by analyzing the acoustic signal at different frequency levels, which is a novelty in the field of ultrashort pulsed laser process sensing. The investigations show, that the optical microphone can be used to resolve both the scanning paths and ablated layers by means of interruptions in a time-resolved acoustic spectrogram. Furthermore, as a result of a higher ablation rate of polyimide compared to copper and thus the increase of the emitted acoustic energy, the material transition between copper and polyimide layers can clearly be detected. The detection of this process event can be used for process control. KW - Ultrakurzzeitlaser Y1 - 2024 U6 - https://doi.org/10.1117/12.3000954 PB - SPIE ER - TY - CHAP A1 - Lutz, Christian A1 - Helm, Jonas A1 - Esen, Cemal A1 - Hellmann, Ralf ED - Kling, Rainer ED - Pfleging, Wilhelm ED - Sugioka, Koji T1 - Computational optimization of borehole sequences for the reduction of heat accumulation in drilling processes using ultrashort pulse lasers T2 - Laser-based Micro- and Nanoprocessing XVIII N2 - We report on laser drilling of borehole arrays using a high-power ultrashort pulse laser with particular focus on reducing heat accumulation in the workpiece by optimizing the drilling sequence, particularly for highly efficient multi-spot drilling. Different optimization approaches are chosen to improve the drilling sequence, also comparing a simplex algorithm and an evolutionary algorithm. From a laser application point of view, we also compare drilling sequences using a single spot and up to 16-fold multi-spots generated by a spatial light modulator, as to accelerate the drilling process in terms of the number of drilled holes per second. To evaluate the temperatures generated during drilling of up to 40,000 holes in less than 76 seconds in stainless steel foil, temperatures are measured by a thermal imaging camera and subsequently compared to a COMSOL-based simulation for all optimized drilling sequences. With respect to an average temperature of 706 °C without optimization, a reduction by 252 °C, i.e., a reduction by nearly 36 % based on the Celsius scale, is achieved using a 4 × 4 beam splitter and an optimized drilling sequence with a drilling rate of 526 holes per second. In addition, using a 2 × 2 beam splitter, a temperature reduction of up to 40.5 % is achieved for a drilling process with a rate of 129 holes per second using an optimized drilling sequence. KW - Ultrakurzzeitlaser Y1 - 2024 U6 - https://doi.org/10.1117/12.3000930 PB - SPIE ER - TY - CHAP A1 - Lutz, Christian A1 - Schwarz, Simon A1 - Marx, Jan A1 - Esen, Cemal A1 - Hellmann, Ralf ED - Kling, Rainer ED - Pfleging, Wilhelm ED - Sugioka, Koji T1 - Combination of an axicon and a spatial light modulator for the generation of multiBessel beams for microdrilling using ultrashort pulsed laser T2 - Laser-based Micro- and Nanoprocessing XVIII N2 - Due to their special beam profile, Bessel beams offer advantageous properties for micro-drilling and internal volume processing, especially for transparent materials. In addition, the laser power of industrial ultrashort pulsed lasers hasnincreased significantly in recent years, offering the possibility of highly efficient processes using multi-spot profiles. We report on optical simulations and an experimental optical setup for generating multi-Bessel beams by combining a refractive axicon and a spatial light modulator. This setup offers a new possibility of multi-Bessel beam generation by functional division of the Bessel beam generation by the axicon and the possibility of separation flexible beam splitting by a spatial light modulator. The beam profiles generated with this setup are analyzed and compared in this study using optical simulations and experiments. In addition to the analysis of the Bessel beams in the machining plane, they are also analyzed in the propagation direction by means of intensity distributions measured by a camera in small-step z positions. Furthermore, the experimental applicability of the module-based beam shaping system is demonstrated by integrating into an existing laser system. KW - Ultrakurzzeitlaser Y1 - 2024 U6 - https://doi.org/10.1117/12.3000946 PB - SPIE ER - TY - CHAP A1 - Bischoff, Kay A1 - Kefer, Stefan A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Towards entirely ultrashort pulsed laser based process chain to manufacture polymer lab-on-chip systems with electrical, photonic, and microfluidic functionalities T2 - The 5th Smart Laser Processing Conference (SLPC) KW - Ultrakurzzeitlaser Y1 - 2024 UR - https://confit.atlas.jp/guide/event/opic2024/subject/SLPCp-22/date?cryptoId=&lo=fin&eventCode=opic2024 ER - TY - CHAP A1 - Bischoff, Kay A1 - Esen, Cemal A1 - Hellmann, Ralf T1 - Acceleration of Femtosecond Reductive Laser Sintering of Copper(II) Oxide for Conductive Copper Patterns on Cyclic Olefin Copolymers T2 - International Congress on Applications of Lasers & Electro-Optics (ICALEO) 2023 N2 - We report on the acceleration of femtosecond reductive laser sintering of copper (II) oxide on the surface of transparent cyclic olefin copolymers (COC) by varying the focus size to generate metallic copper (Cu) layers. By using different focusing conditions, different process speeds are achieved, and the structural accuracies are controlled. The formation of Cu lines is observed for different focus sizes at various scan speeds, which is attributed to laser exposure duration and chemical reaction time. The formed lines are categorized and measured by optical microscopy and provide the basis for two-dimensional Cu surfaces. By hatching, high quality conductive films are produced with an increased focus diameter of up to 400 µm at a scan speed of 400 mm/s and a hatch distance of 250 µm resulting in a multiple increased process speed by a factor of thirteen compared to previous research. Using 4-tip measurement , a low sheet resistance of 0.165 Ω/sq was validated on these Cu films, which have an atomic Cu content of 89.5%. KW - Femtosekundenlaser Y1 - 2023 ER -