United States

Brass represents a large part in the production of components within the copper alloy group. Laser beam welding of this alloy offers great potential for many applications in terms of achievable seam quality and productivity. However, there is a very high tendency of the process to produce irregular seam surfaces, ejection of the molten metal and pore formation. These are due, among other things, to instabilities of the keyhole, which is favored by the evaporation of the alloy component zinc. Furthermore, near-infrared laser beam wavelength can couple poorly into the material due to the low absorption level of brass, whereas absorption jumps during the melt transition. In recent years, high-brilliance near-infrared laser beam sources with adjustable beam profiles have been developed that can lead to keyhole stabilization.&lt;br&gt;
The experimental process investigations are on deep penetration welding of different brass alloys (CuZn37 and CuZn39Pb3). A multi-kW laser beam source with combined core and ring beam is used for this purpose. Main process parameters are identified and systematically varied. The produced seams are analyzed and evaluated using different methods (including micrograph analysis and topography images). The results are correlated with the process parameters. Line Energy per unit length, spot size and process gas supply have a significant effect on the weld seam resulting. Process parameters were found to produce high quality bead on plate and butt welds for sheet thicknesses of 2 mm.

ICALEO 2023

Laser Beam Welding of Brass With Combined Core and Ring Beam

core and ring beam

brass

laser beam welding

Brass represents a large part in the production of components within the copper alloy group. Laser beam welding of this alloy offers great potential for many applications in terms of achievable seam quality and productivity. However, there is a very high tendency of the process to produce irregular seam surfaces, ejection of the molten metal and pore formation. These are due, among other things, to instabilities of the keyhole, which is favored by the evaporation of the alloy component zinc. Furthermore, near-infrared laser beam wavelength can couple poorly into the material due to the low absorption level of brass, whereas absorption jumps during the melt transition. In recent years, high-brilliance near-infrared laser beam sources with adjustable beam profiles have been developed that can lead to keyhole stabilization. 
The experimental process investigations are on deep penetration welding of different brass alloys (CuZn37 and CuZn39Pb3). A multi-kW laser beam source with combined core and ring beam is used for this purpose. Main process parameters are identified and systematically varied. The produced seams are analyzed and evaluated using different methods (including micrograph analysis and topography images). The results are correlated with the process parameters. Line Energy per unit length, spot size and process gas supply have a significant effect on the weld seam resulting. Process parameters were found to produce high quality bead on plate and butt welds for sheet thicknesses of 2 mm.

technical paper

**General Chair Welcome**

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Welcome to ICALEO® 2023!
	
We were excited to host the world’s leading international conference on Lasers and Electro-Optics in Chicago. The Laser has been shown to have the potential to revolutionize solutions for major global challenges like energy usage and supply, global warming, and CO2 footprint. Even the fusion energy breakthrough is based on laser technology. The conference, with peer-reviewed scientific and technical presentations, focused on the newest results in Micro Applications, Macro Applications, Additive Manufacturing, Beam Shaping and Frontiers in Laser Applications. Additionally, the Battery-Manufacturing Track gave an overview of the process combined with the newest advances in laser application results. 

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Whether this is the first time you are hearing about ICALEO or you are a longtime attendee, you will find something of interest, new ideas, and an excellent opportunity to network with other laser specialists worldwide. 

**Klaus Löffler **  
ICALEO General Chair   
Managing Director, Precitec GmbH

**What is ICALEO?**

ICALEO® brings together the brightest minds, seasoned professionals, and pioneering researchers from around the world. With a laser-focused agenda, ICALEO offers an exceptional platform to delve into the cutting-edge advancements, diverse applications, and transformative research that define lasers and electro-optics.

Participants will be immersed in a dynamic environment that fosters collaborative learning, networking, and idea exchange. Through engaging plenary presentations, technical sessions, an industry business panel, and networking events, attendees gain insights into the forefront of laser technology. From industrial applications to medical breakthroughs, additive manufacturing to materials processing, ICALEO covers the entire spectrum of laser-related disciplines. Moreover, the event serves as a launching pad for synergistic partnerships, paving the way for professionals to forge connections that shape the future of our industry.

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ICALEO® brings together the brightest minds, seasoned professionals, and pioneering researchers from around the world. With a laser-focused agenda, ICALEO offers an exceptional platform to delve into the cutting-edge advancements, diverse applications, and transformative research that define lasers and electro-optics.

Fast oscillation of the laser beam is an established and proven method for beam shaping to improve laser material processing in terms of machining quality, process stability, and time. In the first part, an overview will be given for available and already proven oscillation devices as 
well as equipment under development. Solutions for beam oscillations in x and y direction as well as solutions for oscillations of the focal plane along the beam propagation direction (z direction) are introduced. Advantages and disadvantages of the various concepts are considered and 
evaluated. 
In the second part, examples will be provided to demonstrate the profitable use of fast laser beam oscillations for the applications of cutting, welding, hardening, and cladding. Finally, opportunities of 3D beam shaping provided by oscillating the beam focus in three spatial directions 
simultaneously or opportunities utilizing x/y oscillations of the laser focal point like a jigsaw are discussed. Consideration is given to whether beam oscillations have the potential to eliminate the need for ever higher laser powers or different wavelength.

Fast Beam Oscillations Improve Laser Material Processing

Automotive lamps have not only functional roles but have highly aesthetic purposes in the design of a car. As such, they use complex three-dimensional shapes to implement various designs. The main manufacturing challenge comes from the plastic bonding process of the complex components which currently is done by thermal bonding, ultrasonic bonding, and laser welding. Laser welding processes with a narrow joint area are preferred since they require minimal joint area and produce no burr. In this study, an optimization study for simultaneous bonding of lamps is carried out using multiple light sources generated by connecting specially manufactured bundle optical fibers with a diode laser source. The diode laser beams with a wavelength of 915 nm and a power of 80 W, each, were simultaneously delivered through a 30-optical fibers bundle. The fibers were integrated within the mold that holds the lamp achieving transmission welding through the overlapped upper transparent polymer PMMA (IF850) and the lower nontransparent polymer ABS (HL121H). The process parameters investigated were the laser power, duration time, waveguide gap, and clamping pressure. We present optimized process parameters that achieved no pores and relatively uniform melting. In the shear test, the average load was approximately 1300 N, and the base sheet fractures along the welding joints were observed.

Experimental Evaluation of PMMA-ABS Transmission Welding Using Mold-Integrated Simultaneous Laser Welding Technology

Endless carbon-fibre reinforced plastics (CFRP) are important lightweight construction materials. While the majority contains a thermoset matrix material, latest developments see an increase of CFRP with a thermoplastic matrix (CFRTP). This is due to their enhanced machinability and versatile material characteristics. However, high-performance thermoplastics and endless carbon fibres are both expensive resources. During the production of parts made from CFRTP, scrap-pieces and left-overs from the cutting process are usually disposed of. To increase the resource efficiency, a process is developed that includes the autonomous laser cutting of such CFRTP remnants to chips of unified dimensions, which can then be reused in the production of long-fibre reinforced CFRTP laminates. 
This study focuses on the laser process development for the cutting of CFRTP with a polyether ether ketone (PEEK) matrix. The development aims for short processing times and minimum thermal alteration of the PEEK. Laser cutting of semi-finished CFRTP is especially challenging, because although most fibres within a carbon fibre roving might be cut, individual fibres might still be intact and may cause fibre pull-out that would severely reduce the cutting-edge’s quality. Therefore, to verify that the CFRTP was completely cut, an optical process monitoring system is developed. 
In this investigation, process parameters are evaluated in terms of cutting time, surface appearance, and the completeness of the cuts. Surface analysis shows colour changes of the PEEK on an area of less than 1mm from the cutting edge. The monitoring system for cut completeness was introduced and showed good detection results.

Laser Cutting of Semi-finished CFRTP Products for Better Resource Efficiency

Glass materials with higher indices of refraction are being developed for use in augmented reality (AR) and similar immersive reality eyewear.&nbsp; Benefits such as lighter weight, larger/better display, and reduced power consumption are being realized through the development of new types of glass having refractive indices above 1.7 and approaching 2.0.&nbsp; As the AR eyewear market continues to grow, there is a growing need to cut these materials with good quality and at high throughputs.&nbsp; AR glass materials present additional challenges for kerf-less laser cutting, as these methods depend on the propagation of light through the bulk of the material which can be impacted both by the material index as well as any coatings present on the glass surfaces.&nbsp; In this work we demonstrate the use of tailored picosecond infrared (IR) pulse bursts to improve the quality of high-throughput Bessel beam-based glass cutting processes, with noteworthy results including roughness improvements of ~40%, overall throughputs in the meters-per-second regime, and cutting of corner radiuses as small as 500 µm.&nbsp; Furthermore, because AR eyewear incorporates active glass for image projection, various glass surface coatings need to be applied.&nbsp; As such, we also present cutting results with the Bessel beam passing through a slit aperture located proximal to the glass surface, which represents processing through an opened channel in such coatings.

Cutting High-Index of Refraction AR Glass with Tailored ps IR Pulse Bursts and Surface-Proximal Slit-Apertured Bessel Beams

In today’s manufacturing, additive manufacturing processes enable the production of complicated three dimensional structures that are hard to be manufactured with traditional manufacturing processes. Due to its high build rate, the Directed Energy Deposition (DED) process is an attractive and versatile process to manufacture these kind of components. In addition to the production of components, DED is used for repair or coating applications. The DED process consists of a multitude of complex thermal mechanisms with high heating and cooling rates of 103 up to 105 K/s. For materials with a high hardness or a low thermal conductivity like tool steels, cast iron or tungsten carbide these high cooling rates can lead to defects in the microstructure like cracks, pores or delamination between the substrate and the deposited structures. By preheating the substrate, the cooling rates can be reduced, and defects can be eliminated. In this paper a preheating cycle was developed, which uses the laser of an DMG MORI LT 65 DED hybrid machine as a moving heat source for the substrate preheating. For this cycle, process parameters, a tool path strategy and a temperature control system were developed. The impact of the elaborated concept was shown by welding tungsten carbide in nickel matrix on S235 steel substrate.

Development of a Laser Preheating Concept for Directed Energy Deposition

This paper provides quantitative information about the paths taken by powder particles which do not enter the laser generated melt pool during laser cladding (DED). These wasted powder particles bounce off the melt pool and the surrounding solid areas. This wastage reduces the productivity of the process. In this paper specially developed software was used to analyze High Speed Imaging videos of the cladding process, to monitor the directions of powder particle flight away from the melt pool area. This information has been correlated to the geometry of the melt pool zone for three different cladding techniques; single track cladding (A tracks), standard overlapping track cladding (AAA cladding) and a recently developed technique called ABA cladding. The results show that the melt pool geometry has a strong influence on powder catchment efficiency and the trajectories of powder particles which bounce away from the laser-material interaction area. ABA cladding was found to have considerably better powder catchment efficiency than standard AAA cladding and this improvement can explained by consideration of the geometries of the melt pools and surrounding solid material in each case. As powder costs are an important factor in industrial laser cladding, the adaption of the ABA technique could have a beneficial effect on the profitability of the process

Laser Cladding (DED); A High-Speed-Imaging Examination of Powder Catchment Efficiency as a Function of Melt Pool Geometry

With recent technological advances in additive manufacturing, laser-directed energy deposition (L-DED) is frequently chosen as a manufacturing process of Inconel 718 (IN718), which is a precipitation hardening alloy that exhibits excellent mechanical properties at elevated temperature after various heat treatments. However, undesirable recrystallization occurs during the post-heat treatment, resulting in the growth of equiaxed grains, which offset the advantage of columnar grain structure from the layer-by-layer deposition. Induction heating-assisted L-DED, which uses induction heating during the deposition, has the potential to skip the first step of the heat treatment by maintaining the deposit temperature at the heat treatment temperature. In this study, three cube-shaped IN718 were deposited using the induction heating-assisted L-DED system at the holding temperature of homogenization, solution, aging heat treatment, respectively. The temperature conditions were selected according to the standard heat treatment specification of IN718 product. In the induction heating-assisted L-DED, microstructure of the deposits strongly depends on the holding temperature of induction heating during deposition. For each deposit,&nbsp;the secondary phases were analyzed by using a scanning electron microscope and the grain structures were studied using electron backscattered diffraction. Additionally, the mechanical properties of each deposit were evaluated. The results of this study can provide the guide for selecting the proper holding temperature during the induction heating-assisted L-DED to achieve the desired microstructure and mechanical properties.

Effects of Holding Temperature during Induction Heating-Assisted Laser-Directed Energy Deposition of Inconel 718

Current rapid growth of the e-mobility sector is driving demand and innovation in the manufacture of batteries. This is particularly evident in the development of laser-based processes for battery cell manufacturing. Whether its cylindrical, pouch or prismatic all battery cells require foils to be cut. Industrial demands are quite demanding and varied due to complexity of the foil materials as well as the electrode designs, making it a challenge to identify the most appropriate laser technology. Requirements range from the slitting of thin bare metal foils to profiling of coated materials where both bare foil and coated material need to be cut. The materials break into anodes and cathodes each posing different challenges as manufacturers require highest possible processing speeds with the highest possible edge quality. Pulsed lasers are becoming the tool of choice, while many foils can be adequately cut with ns lasers some material combinations benefit from shorter ps pulses. This contribution gives a broad overview of the challenges of laser cutting of battery foils and explores the pros and cons of ns vs ps for different materials. The analysis focuses on achievable processing speeds as well as cut edge quality and looks at a variety of laser parameters such as pulse duration, pulse energy and peak power. The influence of laser parameters such as spot size, working fields and processing strategies are discussed. This work shoes that choices are not always straight forward, and users are left to balance the need between Cost – Quality – Productivity.

Battery Foil Cutting – Should You Use ns or ps Laser Sources?

Laser-based manufacturing has become a key enabling technology in the production of batteries and battery cells for e-mobility applications. Several applications, in fact, have already been industrialized for welding, cutting and stripping with lasers. Cutting, in particular, has to fulfil many very stringent constraints, such as: highly reflective materials (aluminum, copper), very low thickness (6-12 µm), on-the-fly processing, high quality of the cutting surface. According to those considerations, the present paper deals with the application of remote cutting of 8 µm thick aluminum and copper foils by means of a galvo scanner and two different fiber laser sources: single mode CW and nanosecond pulsed ones. The experimental activity is devoted to understanding the feasibility of the process and to point out pros and cons of the two different lasers involved. The cutting edges are analyzed by means of optical and SEM microscopy and confocal profilometry, in order to characterize the quality of the cutting, the presence of burr and the extension of the heat affected zone. The process is also characterized in terms of maximum achievable speed in order to understand the limits of both laser and galvo scanning system and some considerations are drawn on the role of the typical fine tuning parameters of the galvo scanner on the possibility to achieve high cutting speeds in an on-the-fly process.

High Speed Laser Cutting of Ultra-Thin Metal Foils for Battery Cell Production

Temporal beam-shaping is a powerful tool for micromachining of various materials with femtosecond lasers. In this contribution, we present our advances of dielectrics microprocessing with an ultrafast laser source which can operate either in the MHz- or in the GHz-burst regime. We compare top-down percussion drilling in glasses with a Gaussian beam in both burst regimes. The GHz-burst mode allows for obtaining crack-free holes with an outstanding surface quality of the inner walls and featuring an almost cylindrical shape without shifting the beam focus nor the sample. The deepest hole is measuring 3.7 mm length and 25 µm entrance diameter, corresponding to an aspect ratio of 150, which is the highest reported so far with femtosecond GHz-burst drilling to the best of our knowledge. Moreover, we show a combination of temporal and spatial beam shaping for cutting of transparent dielectric materials. A Bessel beam is formed using an axicon, and we compare the cutting results in both burst operation regimes. We illustrate the influence of the laser beam parameters such as the burst energy and the pitch between consecutive Bessel beams on the machining quality of the cutting plane and provide processing windows for both burst regimes. In both regimes, dust- and chipping-free cutting has been achieved for glass samples of up to 1 mm thickness. However, the best cutting plane quality in terms of surface roughness is obtained in the GHz-burst regime.

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Fast Beam Oscillations Improve Laser Material Processing

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Fast Beam Oscillations Improve Laser Material Processing

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