Direct Laser Interference Patterning (DLIP) is an established technology for producing textured and functional surfaces using beam-shaped laser radiation. It consists of producing high-intensity interference patterns by overlapping two or more laser beams at the material surface. In this work, new possibilities for producing textured surfaces on metals and polymers using high-throughput concepts for DLIP are presented. The first concept describes the development of a new DLIP optical head (called xDLIP) with an outstanding depth of focus of approximately 10 mm, which can be equipped with fs, ps or ns pulsed laser systems. This approach makes this device ideal to treat large areas as well as three-dimensional parts. In particular, a setup using an industrial robot system is shown. The second approach includes the combination of a new DLIP optical system with a polygon scanner, showing the possibility to treat metallic and polymer surfaces. This includes configurations for reaching 7.0 and 21.0 μm spatial periods at throughputs beyond 1 m2/min. Finally, DLIP is implemented into a roll-to-roll process using a high-power picosecond pulsed laser source, in which the main laser beam is shaped into two elongated beams which go through a scanner system. Using this setup, aluminum and copper foils with thicknesses of 20 μm and 9 μm, respectively, are processed.
Improving processes sustainability to address upcoming demands in metal processing industries such as innovative and hard to process materials has become a major topic for many manufacturers. Therefore, new tool material compositions or surface coatings are continuously developed. In this context, surface functionalization of cutting tools is foreseen as a convenient approach for minimizing material losses and thus energy consumption. In this work, laser induced periodic surface structures (LIPSS) are used for manufacturing quasi-periodic line-like patterns on tungsten carbide inserts. The textured tool surfaces show low spatial frequency LIPSS (LSFL) with spatial periods of 500 nm to 600 nm as well as high spatial frequency LIPSS (HSFL) with a spatial period of ~100 nm. Furthermore, the texturing is applied on rake and flank faces of the cutting tools with different offsets to the edge between 0 and 0.2 mm. The wettability analysis reveals a decrease of static contact angles for the used cutting fluid (CIMSTAR) from 38° to 12°, suggesting an improved cooling process during the machining step. In addition, turning experiments under lubricated conditions are carried out on Al 6061 T6 parts to investigate the tribological performance. The used LIPSS-functionalized cutting tools could effectively decrease the main machining forces by 10 %, the feed force by 21 % and the passive force by 9 %. Furthermore, the laserprocessed tools generate thinner chips, which leads to a decrease in surface roughness by 31 % of the aluminum work piece.
Nowadays, improving processes sustainability has become a major topic for many manufacturers in metal processing industries. Next to the challenging rise of costs of raw material and tools, innovative and hard to process materials enter the market. Here, surface functionalization of cutting tools is devised as a convenient approach for reducing energy consumption as well as material losses. In this work, direct laser interference patterning (DLIP) is used for manufacturing periodic line-like structures with spatial periods of 5.5 μm on tungsten carbide. The texturing is applied on rake-flank faces of the cutting inserts, leading to texture depths up to 1.75 μm by controlling the amount of used laser pulses. Moreover, turning experiments under lubricated conditions carried out on Al 6061 T6 parts with structured and untreated tools are performed to investigate the tribological performance. In result, the used DLIP-functionalized cutting tools could effectively decrease machining forces up to 12 %. This is caused by the corresponding improvement in frictional and improved lubrication behavior at the tool/chip interface. Furthermore, the laser-processed tools generate thinner chips, which leads to a decrease in surface roughness by 31 % of the aluminum work piece. This work thus offers insight into the viability of improving cutting tools by laser surface micro patterning for upcoming innovative materials designed for improving tool wear resistance, energy efficiency and surface quality.
Additive Manufacturing methods enable the fabrication of complex 3D components for a wide range of applications, ranging from prototyping up to part manufacturing in industrial several sectors including aerospace and medical industries. In particular, the surface quality of these parts have to be improve in order to reach standard qualities or to obtain specific surface functions. In this frame, this research work reports on laser-based surface finishing treatments of additive manufactured specimens consisting on a new innovative aluminum-alloy (Scancromal®). The experiments are performed with a picosecond pulsed-laser system operating at a fundamental wavelength of 1064 nm, aiming the fabrication of functionalized surfaces with improved properties through topographical features in the micrometer range. To characterize the surface topography, the specimens are analyzed using Confocal Microscopy (CM) and Scanning Electron Microscopy (SEM). Contact Angle measurements are used for the determination of wetting and icing-repellent characteristics of lasertreated AM substrates. Additionally, surface free energy (SFE) is determined and compared with the reference samples. The results show a significant influence of the laser treatment on the surface quality of the treated samples and its resulting wettability behavior. For instance, the water contact angle (WCA) could be increased from 62° to 134°, while the freezing time is also increased from 11 to 25 s after laser treatment, which can be an advantage for some applications and extend the feasibility of AM components beyond the current state of the art.
Additive Manufacturing (AM) processes enable the fabrication of complex three dimensional lightweight parts in a simple way, making these technologies attractive and viable for a wide range of applications in industrial sectors such as aerospace and medical industry. However, it is well known that surfaces of AM components have a relative high roughness level, which can limit their applicability in industrial fields. This study describes the surface modification of AM parts by Direct Laser Writing (DLW) and Direct Laser Interference Patterning (DLIP) to improve the surface quality of additive manufactured specimens made of Titanium 6Al 4V (Ti64) and an Al-Mg-Sc based alloy (Scalmalloy®). The experiments are carried out with an Ytterbium fiber laser and a Nd:YVO4 solid-state laser for DLW and DLIP process, respectively. The DLW laser process enabled the reduction of the initial surface roughness as well as facilitating the fabrication of defined periodical textures with feature sizes in the micrometer range, implemented by DLIP. These textures permitted to control the wettability of the surfaces. The laser treated and non-processed parts are characterized using White Light Interferometry (WLI), Confocal Microscopy (CM) and Scanning Electron Microscopy (SEM). Additionally, the wettability behavior was analyzed through long-term water contact angle measurements over a period of 50 days.
Nature provides many examples of surface structures with multiple functionalities. Some of those, such as light management and self-cleaning, are of interest for increasing the efficiency of optoelectronic devices, such as OLEDs, and for adding new surface functions. However, mimicking and transferring these textures to polymers over large areas often requires complex processes at high costs. Here, we demonstrate a low-cost strategy to fabricate hierarchically textured polyethylene terephthalate (PET) films by plate-to-plate hot embossing. Laser-machined stainless-steel plates with doublescaled hole-like textures were used as master for hot embossing. The larger structure with a period between 30 µm and 70 µm and depths up to 8 µm was produced by direct laser writing (DLW), whereas the smaller structure featuring a period of 3 µm at a depth up to 2 µm was fabricated by direct laser interference patterning (DLIP). The textured surfaces of stainless steel were then molded onto PET films at a pressure of 42 MPa and a temperature of 85°C using a hydraulic press. Topographical characterization was performed by confocal microscopy and scanning electron microscopy. Experiments have shown an increased static water contact angle up to 105°. Furthermore, the hierarchically microtextured foils were studied as out-coupling layers in OLEDs, showing a potential increase in device efficiency of up to 57%. The results thus indicate a good suitability of the developed surfaces for use in highly efficient OLEDs with easy-to-clean properties.
The fundamentals of laser remote cutting will be introduced as well as a comparison to the conventional laser fusion cutting process. The opportunities and limitations of this alternative laser cutting technology will be discussed in detail by means of recent application examples. Here to name cutting of typical punching and bending parts, battery foils, metals foams and electrical steel sheets. Questions that are concerning the cutting thickness, the cutting quality, the cycle time, and the impact on the material will be answered. Finally, conclusions and an outlook on future developments will be presented.
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