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Increasing the efficiency of material removal using dual laser micromachining
摘要： A continuous wave melting laser combined with a nanosecond ejection laser has been shown to improve the material removal efficiency by a factor of 2 to 8 compared with laser ablation processes reported in the literature. The decrease in the energy required for the combined lasers is primarily due to the optimisation of the irradiation time in the melting process, which is responsible for the majority of the total energy. For the laser used in this study, the optimal interaction time corresponding to the highest melting efficiency was found at 9-ms melting time, and this value is compared with results derived from a one-dimensional heating model. Metallurgical images of only melting and the produced hole after introducing the ejection pulse for the most efficient melting were presented as evidence of melt ejection. The results show that approximately 90% of the melt pool is ejected with little redeposited material at the periphery of the hole.
关键词： Beam-matter interaction,Short pulsed lasers,Laser material processing,Laser melting
更新于2025-09-23 15:21:01
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Laser-Induced Periodic Surface Structuring of Poly(trimethylene terephthalate) Films Containing Tungsten Disulfide Nanotubes
摘要： We report the study of the formation of Laser Induced Periodic Surface Structures (LIPSS), with UV femtosecond laser pulses (λ = 265 nm), in free-standing films of both Poly(trimethylene terephthalate) (PTT) and the composite PTT/tungsten disulfide inorganic nanotubes (PTT-WS2). We characterized the range of fluences and number of pulses necessary to induce LIPSS formation and measured the topography of the samples by Atomic Force Microscopy, the change in surface energy and contact angle using the sessile drop technique, and the modification in both Young’s modulus and adhesion force values with Peak Force-Quantitative Nanomechanical Mapping. LIPSS appeared parallel to the laser polarization with a period close to its wavelength in a narrow fluence and number of pulses regime, with PTT-WS2 needing slightly larger fluence than raw PTT due to its higher crystallinity and heat diffusion. Little change was found in the total surface energy of the samples, but there was a radical increase in the negative polar component (???). Besides, we measured small variations in the samples Young’s modulus after LIPSS formation whereas adhesion is reduced by a factor of four. This reduction, as well as the increase in ???, is a result of the modification of the surface chemistry, in particular a slight oxidation, during irradiation.
关键词： nanocomposites,ultrashort pulses,laser material processing,nanostructures,LIPSS
更新于2025-09-23 15:21:01
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Latest developments of laser cutting
摘要： Laser cutting was one of the first applications of laser material processing. Today, laser cutting is the most widespread laser material processing besides laser marking. Meanwhile, nearly each material can be cut by means of a laser, in particular since ultra short pulse lasers are available in the power range of up to 100 W. The to be cut material can come with thicknesses from a few microns till tens of millimeters as flat stock or as free form shapes. The paper will concentrate on cutting with high power cw lasers in the near and far IR range. Latest developments in terms of thick plate fusion cutting of metals, in particular the positive impact of dynamic beam shaping, will be discussed. The state of art of laser cutting of thin sheet metal without assist gas will be described as well. In the case of non-metals, latest results of laser cutting of composites like fiber reinforced plastics by using two different wavelengths at the same time are introduced and discussed. First results of cutting by means of a novel green cw laser will be presented. Finally, an outlook of future trends of laser cutting will be given in terms of further process improvements and first steps of process control.
关键词： fiber reinforced plastics,green cw laser,laser cutting,dynamic beam shaping,material processing
更新于2025-09-16 10:30:52
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Metal Polymer Connections: Laser-Induced Surface Enlargement Increases Joint Strength
摘要： The trend towards hybrid materials consisting of metals and polymers is strongly driven by requirements such as weight reduction and improved functionality. A crucial step towards new hybrid materials is the advancement of joining technology. While metals and polymers are currently often joined using adhesives, this technology has major drawbacks such as long process cycle time, low robustness with regard to changes of the material composition, and are almost impossible to recycle, a point which is becoming increasingly important. A promising joining method is thermal direct joining of metals and thermoplastic polymers due to its fast cycle time, its robustness of the process and the absence of duroplastic adhesives. Direct joining requires surface treatment of the metallic joining partner prior to the thermal joining process to achieve a sufficiently high contact strength. It is known that laser-induced topologies on the metal surface are beneficial with regard to contact strength of the joints. Designing a joint based on laser structured metals requires a fundamental understanding of the interface interactions. The present paper focuses on the influence of surface enlargement on the joint strength. Laser pretreatment was utilized to generate surface structures with specific surface enlargement on the metallic joining partner. The pretreated metallic parts were subsequently joined with a thermoplastic polymer by injection molding. The joint strength was investigated in single lap shear tests. The key finding is that the contact strength increases almost linearly with the surface area within the tested parameter range, while the structure geometry parameters have only a minor influence. This may help as a design guideline for future adhesive-free hybrid material joining technologies.
关键词： hybrid joining,laser material processing,metal polymer connection,micro structuring,metal polymer joints,lightweight,adhesion,in-mold assembly
更新于2025-09-16 10:30:52
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[Laser Institute of America ICALEO? 2017: 36th International Congress on Applications of Lasers & Electro-Optics - Atlanta, Georgia, USA (October 22–26, 2017)] International Congress on Applications of Lasers & Electro-Optics - Influence of vapor on hyperspectral imaging for monitoring laser-based material processing
摘要： In this paper a further characterization of hyperspectral imaging (HSI) system that we developed is presented. This camera-based system is meant to be used for temperature determination in laser-based material processing. It comprises a high-speed camera and a self-developed HSI-lens system. It offers a time resolution in the μs-range and a spectral resolution of ~4 nm. In HSI spatial and spectral information upon the object/process to be investigated can be acquired simultaneously. The spectral information reveals spectral features of the process itself and it is used to derive temperature information. For temperature determination, the process emissions are considered to be black/gray-body radiation. Based upon very promising initial HSI results, we present and discuss further HSI-derived observations of the laser-beam welding process within this paper. These results include temperature information as well as spectral characteristics. In addition, simultaneous high-speed camera observations were conducted and the results were connected with HSI-derived findings. This way, the influence of vapor on the measurement is evaluated and the HSI-technique is validated to be beneficial in monitoring laser-based material processing.
关键词： hyperspectral imaging,laser-based material processing,vapor influence,temperature determination,high-speed camera
更新于2025-09-16 10:30:52
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Deriving spectral information upon the laser welding process employing a hyperspectral imaging technique
摘要： In this paper we present results from process observations of deep penetration laser welding using a hyperspectral imaging (HSI) technique. For monitoring different types of laser-based material processing, we developed an appropriate high-speed camera-based HSI system. This system enables us to derive spectra of the deep penetration welding process with high time resolution. These spectra can be used for temperature determination or to extract spectral characteristics, both of which can help to further investigate process dynamics and properties of the vapor. The presented results contain particularly HSI-derived spectral information of the evolving vapor plume that is related to corresponding high-speed images and spectra acquired with a conventional VIS-spectrometer.
关键词： laser-based material processing,deep penetration laser welding,process monitoring,hyperspectral imaging
更新于2025-09-12 10:27:22
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New process of tempering color printed glass by using laser irradiation
摘要： Colored glass products with various printing technologies are becoming more important in industry. The aim is to achieve individual solution in a very short delivery time. Conventional thermal treatment of burning glasses in oven for tempered color printing has predominant issues with high time consumption, energy consumption and manufacturing cost. It requires alternative process development. This paper proposes laser process to overcome issues in conventional treatment with the latest results of tempering colored glass. Samples have been analyzed with the scanning electron microscope (SEM). Two different laser systems have been applied and the glass has been printed with black paste.
关键词： scanning electron microscope (SEM),glass,printing technologies,laser material processing,pigment paste,surface treatment
更新于2025-09-12 10:27:22
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Laser welding of copper using a high power disc laser at green wavelength
摘要： The trend towards renewable energies and electromobility is increasing the demand for copper. Laser welding as a flexible and fully automatable process is being more frequently employed to join copper materials. The use of green laser radiation compared to infrared laser radiation has the advantage of a significantly higher absorption coefficient for copper materials. Therefore, high power laser sources emitting at a green wavelength promise a more stable and a more efficient process. In this paper, experimental investigations with a green continuous wave laser radiation at a maximum power of 1 kW are presented. Using design of experiments, the process limits are determined depending on the laser power and the welding velocity. Furthermore, the potential of heat conduction welding using this laser source is investigated.
关键词： Green wavelength,Laser material processing,Heat conduction welding,Process limit,Copper
更新于2025-09-12 10:27:22
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Surface functionalization under water using picosecond and femtosecond laser pulses – first observations and novel effects
摘要： Functionalization by changing the topography of workpiece surfaces is interesting for many applications. Lasers – especially ultrashort pulse lasers – are flexible tools for this kind of tasks. Besides deterministic structures they allow for processing surfaces in a way that stochastic structures appear. Ripple and spike structures can be fabricated in air. In liquids, however, there are only a few investigations and many open questions. The idea of this paper is to check how water in contact to the workpiece surface affects femtosecond laser surface processing and what kind of structures appear. Results obtained with a picosecond laser are presented for comparison.
关键词： ultrashort pulse laser,surface functionalization,spike structures,material processing in liquids
更新于2025-09-12 10:27:22
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High-precision femtosecond laser beam shaping in material processing
摘要： Laser beam shaping is the process of modulating the amplitude and phase of a laser beam. With the development of the spatial light modulator, laser beam shaping can modulate the light field to arbitrary pattern dynamically via the computer-generated hologram (CGH). Otherwise, femtosecond laser is widely used in material processing owing to its high peak power, low hot effect and nonlinear effects. However, femtosecond laser is not strictly monochromatic, which will introduce dispersion when femtosecond laser diffracted by a spatial light modulator, and deteriorate the effect of beam shaping. Here we present a method of high-precision femtosecond laser beam shaping. Experimental results confirm that the proposed method can be used to shape femtosecond laser beams into arbitrary patterns in the whole field of view (FOV) with the resolution near the optical diffraction limit.
关键词： spatial light modulator,beam shaping,dispersion compensation,femtosecond laser,material processing
更新于2025-09-12 10:27:22