United States

During laser fusion cutting, burr forms when the molten metal does not sufficiently exit the interaction zone. When it forms on the lower edge of the cut flank, burr becomes a factor limiting quality. Previous research has shown that a temporally regular and spatially localized melt flow can prevent the formation of burr. However, the high dynamics of the sub-processes involved can cause intrinsic instabilities that disrupt the flow and reduce the efficiency of the melt ejection. This paper presents a study on the correlation between process parameters, melt flow properties, and burr formation. It includes an experimental observation of the melt-flow dynamics using high-speed videography. In addition, a numerical CFD model was set up to examine fundamental flow properties, some of which are not observable experimentally. The dependency of the burr formation on the liquid Weber and Reynolds numbers is analyzed and it is demonstrated how the magnitude and allocation of vapor pressure gradients in the kerf decisively affect melt ejection and burr formation. Additionally, a previously unknown melt ejection regime is identified in the thick section range, which occurs at feed rates close to the maximum cutting speed under specific high-power process conditions. This regime is characterized by a significantly increased process efficiency that could open up a new high-speed process window.

ICALEO 2023

Numerical and Experimental Investigation of the Melt Removal Mechanism and Burr Formation During Laser Cutting of Metals

transient process simulation

high-speed schlieren-videography

compressible supersonic gas jet

melt flow dynamics

technical paper

**General Chair Welcome**

![](https://assets.underline.io/markdown_image/1/image/d6e6dddc08bf2371b9136ea9c18dc5ab.png)              

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. 

The Business Session brought the business aspect and environment of the laser to the audience and the possibility to discuss with seasoned industry leaders from around the world. 

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.

Join us in Chicago and be part of an unparalleled gathering that challenges the boundaries of possibility within lasers and electro-optics. As we convene to share knowledge, explore innovations, and cultivate collaborations, ICALEO stands as a pivotal force driving the evolution of this transformative technology.

**Who attended?**

ICALEO is tailor-made for professionals, researchers, academics, and enthusiasts who are deeply passionate about the world of lasers and electro-optics. If you're an industry trailblazer, an academic luminary, an aspiring expert, or a postgraduate student looking to dive into the latest developments and trends, this is an event you won't want to miss.

Industrial leaders seeking to stay ahead of the curve in their fields, engineers working on laser applications, and manufacturing experts interested in additive manufacturing and materials processing will find ICALEO to be an invaluable platform. Researchers and scientists exploring the forefront of laser technology, from fundamental principles to groundbreaking applications, will also discover a wealth of knowledge and networking opportunities.

Medical professionals investigating laser-based medical advancements, entrepreneurs seeking to innovate with lasers, educators aiming to stay updated with the latest in laser education, and policy makers shaping the industry's landscape are all essential attendees. Whether you're an established expert or a rising star, the 42nd annual ICALEO promises to offer a diverse ecosystem of expertise, connections, and knowledge sharing that caters to the laser and electro-optics communities.

**Fields Represented:**

* Entrepreneurs and Innovators
* Manufacturing Experts
* Students and Graduates
* Policy Makers and Regulators
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Please register for the ICALEO 2023 Conference to join the event.

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.

This study investigates the influence of wire preheating on the Laser Directed Energy Deposition (L-DED) process during material deposition. To achieve this, an induction wire heating system and a wire feeding system were integrated into a 10 kW fiber LASER on an experimental bench, and 1020 steel bars were used as specimens with ER70s-6 wire as the filler material. The depositions were performed to examine the effects of preheating and laser parameters on the strand characteristics. The deposition characteristics were analyzed using temperature measurements obtained from a thermographic camera, and a macrographic analysis was conducted to evaluate the penetration and bead width. The preliminary results of this study indicate that preheating with the induction heating system of the feeder enhance the stability in the dilution, width, and height profiles of single strands at temperatures around 450 °C and a wire speed of 0.8 m/min. The integrated equipment techniques also demonstrate the potential to improve the geometric profile of coating height for ER70s-6 samples. The findings of this study suggest that preheating of the wire using the induction heating system can significantly affect the L-DED process by improving the stability of the deposition profiles. Furthermore, the integration of the wire feeding system and the fiber LASER technology can enhance the overall process control, leading to improved deposition quality. These results contribute to a better understanding of the L-DED process and provide insights into the optimization of the process parameters for various materials and applications.

Exploring the Influence of Hot-Wire Power Density on Wire Melting Behavior in Laser Directed Energy Deposition (L-Ded)

For insulting layers in multi-layer printed circuit boards, Ajinomoto build-up film (ABF) is one of the most crucial component in manufacturing of high-performance electronic devices. The ongoing demand for miniaturized electronic components with advanced functionalities requires a higher power density in packaging and interconnect technology, in turn demanding for a reduction of the diameter of laser drilled microvias. 
Recently, ultrashort pulsed lasers have gained considerable attention for microdrilling owing to a negligible heat material interaction and the possibility of small focal diameters by a wavelength in the ultraviolet regime. In order to evaluate its full potential for laser microvia fabrication, we report on a comprehensive study of laser microvia percussion drilling of ABF using a high-power laser system with a wavelength of 355 nm and a laser pulse duration of 10 ps. For the optimization of the laser drilling quality, which in turn is defined by the fabricated taper and the diameter of the microvia as being evaluated by laser scanning microscopy and materialography, laser bursts containing of a number of intra-burst pulses between 1-6 at an intra-burst pulse repetition rate of 82 MHz, different number of laser pulses, laser pulse fluence and laser burst repetition rates, respectively, are varied. In addition, diffractive optical elements are used to transform the Gaussian beam into a round uniform-intensity laser spot within the focal plane of the telecentric f-theta lens to influence the drilling process.

UV Picosecond Laser Drilling of ABF Material for Printed Circuit Boards Using Laser Burst Mode and Beam Shaping

The topic of this research is the reduction of the amount of radioactive waste generated by the decommissioning of nuclear power plants. By removing the contaminated portion of the concrete surfaces prior to the dismantling, the amount of radioactive waste can be expected to be significantly reduced. There are various methods for removing concrete surfaces. In this study, laser is used since it can efficiently remove concrete surfaces while reducing the generation of by-products. The scraping efficiency of the laser was examined by varying the laser parameters and the concrete strength. The amount of the concrete removed could be significantly increased by lowering the laser irradiation speed and increasing the number of outputs. It was also found that the concrete strength has no influence on the amount of concrete removed using this method. This suggested that laser concrete removal methods can be adapted on a wide variety of concrete structures. Compared to the other removal methods reported in the previous studies, the laser removal method can remove the same amount of concrete in just half amount of time. These results indicated that using laser does not only reduce the generation of radioactive by-products, but also it is a more efficient method for removing concrete surfaces. Additionally, since its effectiveness does not depend on the concrete strength used in the structure, it might be widely applicable for various types of concrete structures.

Study of Efficient Removal Method of Concrete Surface by Fiber Laser

Silicon carbide, an emerging material with outstanding semiconducting and electrical properties, is increasingly triggering scientific and industrial interest for the development of cutting-edge high-power and high temperature electronics as well as ultrafast electronic devices. However, due to its high hardness mechanical processing is very difficult and its chemical inertness results in challenges in wet etching. Therefore, laser processing appears to be a promising approach for micromachining, cutting or drilling. 
As a result of recent developments in laser and optics technology, frequency tripled ultra-short pulsed laser systems emitting in the ultraviolet spectral region with high power and pulse energy, and at the same time high beam quality and durability, motivating new applications of laser micromachining. 
Against this background, we report on novel ultraviolet ultra-short pulsed laser processing of silicon carbide. Laser ablated cavities are evaluated with respect to their ablation rates, surface roughness and overall quality. In addition to pulse fluence variation, the influence of repetition rate and focus diameter are investigated. Besides to shaping of sophisticated geometries, functional surfaces are generated. The comparison with infrared wavelength underlines the advantages of the ultraviolet wavelength. Significant differences with respect to the measured ablation rates and roughness as well as generated micro- and nanostructures appear. While infrared ablation is dominated by a chipping mechanism above a critical threshold, higher ablation rates are observed with strong quality losses at the same time. In comparison to the infrared emission wavelength, in general, a significantly higher processing quality is achieved with the ultraviolet emission wavelength.

UV-Femtosecond-Laser Structuring of Silicon Carbide

Laser-based production systems have become more and more popular in recent years due to their potential to achieve high precision and accuracy in a wide range of different applications. However, the kinematic systems used for laser material processing are often inherited from other production technologies such as milling. The use of mobile robots equipped with laser processing optics could disprove the current paradigm of adapted kinematic systems: scaling the size of the material processing system with the size of the components being processed, and thus the resources used. The trend of autonomous mobile robotic systems replacing classical kinematic systems in the field of material handling in industrial applications has been evident for years due to their higher flexibility, efficiency and lower operating costs. In this paper, the prototype of a corresponding mobile robot system is presented. In addition, the general design of the mobile robot is presented. One challenge is the accuracy of a mobile robot system, for a common LMP process such as laser cutting, the mobile robot must be able to follow a predefined trajectory as accurately as possible. For this purpose, two different measurement systems are presented and compared. To demonstrate the potential of the mobile robot, an exemplary laser material processing is also performed and evaluated. Finally, possibilities for improvement or further development, such as the integration of scanner optics or the use of several autonomous mobile robots to increase productivity, are shown.

An Approach Towards the Application of Mobile Robots in Laser Materials Processing

Exploiting the Potentials of Laser Beam Shaping for Welding Applications via Numerical Simulations

In the attempt to produce lighter battery packs at lower cost, replacing common copper parts with aluminium components has been a popular approach in recent years. With regards to joining technologies, there is a growing interest in applying laser beam welding in battery manufacturing due to several advantages such as single-sided and non-contact access, whilst maintaining a narrow heat affected zone. Motivated by the need to control and reduce weld porosity in AA1060 battery busbar welding with the ultimate goal to enhance durability and reduce electrical resistance, this paper has been developed with the aim to study the mechanisms of porosity formation and implement a novel beam shaping approach to reduce the volumetric pores distribution. Porosity formation is attributed to two mechanisms: metallurgical porosity caused by chemical reactions and process porosity related to the instability of the keyhole and fast solidification rates. In this study, a multi-physics Computational Fluid Dynamics (CFD) model has been developed and calibrated to study the effect of a circular and a tailing laser beam shape on melt pool dynamics and evolution of porosity due to instability of the keyhole, and hence generate knowledge about the underlying physics of the welding process itself. The study will discuss roots of actions for optimisation of weld quality via integration of laser beam shaping lens in “off-the-shelf” welding heads.

Elucidating the Effect of Circular and Tailing Laser Beam Shapes on Keyhole Necking and Porosity Formation During Laser Beam Welding of Aluminium 1060 Using a Multi-Physics CFD Approach

Normally, the phrase "making the invisible visible" is used when sensors/cameras are used for monitoring purposes that operate in a different spectral range than the human eye. 
In this contribution to ICALEO 2023 we will interpret this phrase somewhat differently. 
There are several systems available in the market which capture or measure and analyze physical effects of the process zone and their properties during the laser processing, but none of these effects and properties stand for “seam quality” for themselves, which is typically defined by mechanical, geometrical and metallurgical properties of the solidified seam. The process properties like emitted visible and thermal radiation or geometrical values of the melt pool or the penetration depth of the laser forming the keyhole (penetration depth) only provide indications of how the desired quality might be achieved. It is also well known that the introduction of OCT in laser materials processing has significantly increased safety in both defect detection and process control. 
However, the focus of this presentation is on the use of artificial intelligence algorithms to "see new things." We will discuss how classified, physical properties can be derived from already reliable process information - "making the invisible visible," so to speak. Instead of defining complex rules for algorithms, the use of Data Science and Machine Learning methods uncovers hidden structures in noisy, unstructured data and makes it possible to find the relationships of the data to physical measurements.

Making the Virtually Invisible Visible - Sophisticated AI Models Based on Seamless In-Process Information Enable More Product Safety

In this study, we present the development of an intelligent neural sensor to predict powder clogging during laser cladding by using machine learning techniques. A major factor contributing to these problems is the difficulty in accurately measuring powder mass flow rate, an essential open-loop variable that determines powder output from the nozzle. Accurate measurements of mass flow rate are essential for optimal process control and prediction of clogging events. To overcome these challenges, an experimental design was conducted manipulating factors such as laser power, travel speed, Z-step, N-layers, nozzle-to-substrate distance, and powder feed rate. The powder mass flow rate served as an independent variable to evaluate the neural sensor's predictive ability of clogging. A combination of three cameras and a microphone was used for real-time data acquisition during the experiments. The cameras captured the deposition process from different perspectives and generated thermal images, while the microphone recorded acoustic emissions. Customized cladding equipment enabled seamless data collection throughout the process. The results show that the smart neural sensor accurately monitors clogging during laser cladding, highlighting its importance to manufacturing. The developed models are able to effectively estimate the mass throughput under different parameters and temperature variations of the substrate material. Future studies may address the prediction of more complex coating properties such as porosity, crack formation, and metallurgical grain size distribution, thus expanding the potential of laser cladding and autonomous manufacturing systems.

Leveraging Machine Learning for Predicting and Monitoring Clogging in Laser Cladding Processes: An Exploration of Neural Sensors

Current trends in laser material processing towards higher efficiency, improved quality as well as increased processing of challenging materials and components lead to the objective of integrated process monitoring and control. For industrial laser welding it is thus desirable to obtain data on process stability and to generate information about processing quality or even to build up inline process control. 
The technical approach of a multi-sensor concept is presented, based on optical, acoustic and thermal sensors for the observation of laser welding processes for metallic materials.&nbsp;Basically, high-speed camera recordings and laser acoustic signals are used to classify laser welds of transmission components regarding typical defects. For this purpose, acquired process data were processed in a combined machine learning model, so that promising prediction accuracy can be achieved. 
In current work, a more complex sensor setup is being developed to further improve the prediction quality and enable transferability to a wide range of applications. 
The development of a cyber-physical system for AI-assisted data processing is presented, which will enable real-time response to dynamic process variations in the future. For this purpose, an optical system for 3D spatial dynamic beam shaping for laser welding and cutting is linked to the multi-sensor system. The data are processed via fast logic circuits (FPGA) into AI models using a cloud-based database and fed into a process control loop. 
The technical setup, AI model and database structures are presented as well as first results of the sensor data evaluation.

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Numerical and Experimental Investigation of the Melt Removal Mechanism and Burr Formation During Laser Cutting of Metals

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Exploring the Influence of Hot-Wire Power Density on Wire Melting Behavior in Laser Directed Energy Deposition (L-Ded)