Laser-based powder bed fusion of metals faces limitations in accuracy, surface quality, and minimal structure size resulting from the inherent melting process. To address these challenges, a novel approach integrating additive and subtractive laser processes at the layer level has been developed. This quasi-simultaneous manufacturing process enables the fabrication of small structures with high aspect ratios, including narrow slits below 50 μm in width. The implications of this advancement are promising, particularly in the fields of electric drives and fuel cells, where accuracy and freedom of design are crucial. In this work, the latest results of the production of narrow, inclined slits in components made of pure iron will be shown. Characteristics like groove-to-groove distance and groove width were analyzed, achieving successful production of continuous slits with varying inclination angles of up to 30° within the manufactured components.
The comprehension of microhole formation during percussion drilling of metals using ultrashort laser pulses is still limited. The shape of a microhole can be impacted by factors like heat accumulation, the emergence of side channels, bending, and bulging. Understanding these defects is challenging due to constraints in conventional diagnostics. To address this issue, high-speed synchrotron x-ray imaging was employed to capture the spatial and temporal evolution of the microhole shape during laser percussion drilling of stainless steel. The recorded images reveal that heat accumulation leads to the creation of a melt film on the microhole walls, exhibiting dynamic fluctuations throughout the drilling process. Furthermore, a transversal widening or bulging of the microhole can be seen later in the process. Additionally, the emergence of side channels was observed in the region of maximum drilling depth, where the overall fluence on the microhole walls falls below the threshold fluence.
We describe how to improve micro-processing using Second Harmonic Generation of a Ultra-Short Pulse laser combined with a Multi-Plane Light Conversion beam-shaper.
Manufacturing at 515nm presents advantages compared to 1030nm : extended depth of field, higher sharpness, and higher ablation efficiency for some materials. The beam-shaper provides a square top-hat with a 1/10 sharpness and an extended depth of field up to 10 times higher compared to other beam-shaping technologies.
We describe process results of different metal samples: LIPSS generation with a 100µm square targeting a period down to 0,5µm and holes drilling holes of a diameter smaller than 10µm.
Ultra-short pulse laser machining has been applied to the polishing of polycrystalline diamond (PCD) wafers in order to generate a smooth surface finish and reduce mechanical polishing time. Past studies were first carried out with a 5W laser highlighting the difference in ablation rates between PCD grades and the possible graphitization of diamond on the surface of micrometric PCD grades over a fluence threshold. Some upscaling work was undertaken at 80W with a 3-pulse burst reducing the Sa of a micrometric PCD grade lapped surface by 50% with a volume removal rate double that of the conventional mechanical polishing technique. From these previous base investigations, an ultra-short pulse laser delivering an average power of 1kW at 500fs via state-of-the-art thin disk multi-pass amplification is implemented here to achieve a higher ablation rate for high throughput processing. This is the first time that such an average power is applied on polycrystalline diamond in the ultra-short pulse regime. A burst mode is also implemented which is demonstrated to reduce the Sa by 10% and 55% on fine and coarse grade surfaces respectively compared to single pulse processing. From 80W to 1kW, the ablation rate is increased by a factor of 70 on micrometric PCD grades while the Sa of the initial lapped surface is reduced by 14% without any graphitization of the diamond structure. However, no improvement of the Sa is performed on the initial surface of coarser grades due to the formation of cavities (~5μm wide) potentially caused by the spallation of diamond grains.
Laser ablation with ultrashort pulses allows to create precise and flexible geometries on various materials. However, the generation of complex surface geometries with low surface roughness, high contour accuracy and defined depth still represents a challenge on porous and inhomogeneous materials such as additively manufactured parts or carbon fiberreinforced plastics (CFRP). In the present work, optical coherence tomography (OCT) was utilized for high-resolution optical distance measurement. The measurement beam of the OCT-based measurement system and the processing laser beam were superimposed with a dichroitic mirror. Combining both beams allowed online, time-resolved recording of the ablated depth during laser processing. The comparison of actual ablation depth with the target ablation depth was used to select areas that had to be processed in the subsequent pass. This closed-loop control of the ablation process was used to generate complex 3D geometries in stainless steel. Furthermore, the closed-loop controlled ablation was utilized for postprocessing of additively manufactured aluminum parts in order to remove support structures and to significantly reduce the surface roughness. Moreover, the OCT-based measurements allowed to determine the orientation of the fibers during controlled laser ablation of CFRP for layer-accurate laser ablation, which served as preparation for repairing damaged CFRP parts.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.