Patrick Herwig

Experimental investigation of the linear polarization state of high power fusion cutting with 1 μm laser radiation

An increase of the cut quality or enhanced process efficiency is still an aim for cutting of thick metal plates with 1.07 μm laser radiation. Nowadays, linear polarization is well investigated for CO2-lasers as an approach to a solution. The same attempt is not explored as much for laser beam fusion cutting of thick metal plates with high power solid state lasers. For this case, the present letter examines the linear polarization in contrast to statistically polarized cuts.

Welding and cutting of copper with high brightness lasers

When using a fiber laser for the processing of copper or other high reflecting materials, we have to take care of the back reflection. If we used a polarized laser with wave lengths in the range of 1 µm, it would be relatively easy to build up an optical diode to block optical feedbacks by using the Faraday isolator (rotator) or the λ/4 window. That system can also be used in order to increase the beam power and power density at the workpiece. The presentation will show the effect of optical feedbacks during cutting and welding with the fiber laser, how those feedbacks could be reduced and how they have to be used to optimize the cutting or welding process. On the other hand the presentation will show the influence of the Brewster effect for applications with the fiber laser. Those effects will be explained from the physical basics to industrial applications.When using a fiber laser for the processing of copper or other high reflecting materials, we have to take care of the back reflection. If we used a polarized laser with wave lengths in the range of 1 µm, it would be relatively easy to build up an optical diode to block optical feedbacks by using the Faraday isolator (rotator) or the λ/4 window. That system can also be used in order to increase the beam power and power density at the workpiece. The presentation will show the effect of optical feedbacks during cutting and welding with the fiber laser, how those feedbacks could be reduced and how they have to be used to optimize the cutting or welding process. On the other hand the presentation will show the influence of the Brewster effect for applications with the fiber laser. Those effects will be explained from the physical basics to industrial applications.

Transient beam oscillation with a highly dynamic scanner for laser beam fusion cutting

Abstract Sheet metals with thicknesses >8 mm have a distinct cutting performance. The free choice of the optical configuration composed of fiber diameter, collimation, and focal length offers many opportunities to influence the static beam geometry. Previous analysis points out the limitations of this method in the thick section area. Within the present study, an experimental investigation of fiber laser fusion cutting of 12 mm stainless steel was performed by means of dynamical beam oscillation. Two standard optical setups are combined with a highly dynamic galvano-driven scanner that achieves frequencies up to 4 kHz. Dependencies of the scanner parameter, the optical circumstances, and the conventional cutting parameters are discussed. The aim is to characterize the capabilities and challenges of the dynamic beam shaping in comparison to the state-of-the-art static beam shaping. Thus, the trials are evaluated by quality criteria of the cut edge as surface roughness and burr height, the feed rate, and the cut kerf geometry. The investigation emphasizes promising procedural possibilities for improvements of the cutting performance in the case of fiber laser fusion cutting of thick stainless steel by means of the application of a highly dynamic scanner.

Laser remote cutting and surface treatment in manufacturing electrical machines—High productivity, flexibility, and perfect magnetic performance

From industrial electrical machine production, it is well known that processing of nonoriented electrical steels causes changes in the lattice and microstructure that also affect the magnetic structure. While applying these manufacturing techniques (punching or laser fusion cutting), mechanical and thermal stresses are induced due to elastic and plastic deformation or temperature gradients within the material. For more than 15 years, fusion cutting with CO2-lasers enabled a flexible and wear-free production but mostly for prototypes and small batches. Ten years ago, the development of diffraction limited solid-state lasers started and thus enabled laser remote cutting (LRC). Nowadays, industry demands sheet thicknesses between 0.35 and 0.5 mm due to the fact of eddy current loss reduction. Concerning this context, best choice is LRC. Within this work, latest results are presented in terms of resulting cutting speed, cutting edge quality, and magnetic properties. Cutting speed of LRC beats laser fusion cutting keeping the high rate of flexibility. The magnetic material properties of laser remote cut laminates are identical or even better to conventional punched parts. Therefore, the manufacturer has been given the possibility to tweak his process toward perfect magnetic behavior or high output volume. All in all, it will be possible to produce high efficient electrical machines regarding the application demands of the costumer.From industrial electrical machine production, it is well known that processing of nonoriented electrical steels causes changes in the lattice and microstructure that also affect the magnetic structure. While applying these manufacturing techniques (punching or laser fusion cutting), mechanical and thermal stresses are induced due to elastic and plastic deformation or temperature gradients within the material. For more than 15 years, fusion cutting with CO2-lasers enabled a flexible and wear-free production but mostly for prototypes and small batches. Ten years ago, the development of diffraction limited solid-state lasers started and thus enabled laser remote cutting (LRC). Nowadays, industry demands sheet thicknesses between 0.35 and 0.5 mm due to the fact of eddy current loss reduction. Concerning this context, best choice is LRC. Within this work, latest results are presented in terms of resulting cutting speed, cutting edge quality, and magnetic properties. Cutting speed of LRC beats laser fusion cut...

System technology for dynamic beam shaping

Since the power of continuous wave laser sources have reached one kilowatt, beam shaping is an important topic in the sector of laser material processing. The high intensity allows the increase of process speed, but the extreme local overheating often decreases the quality. Typically beam shaping solutions use a static beam adaptation by optical elements. For laser cutting for example, the increase of sheet thickness requires larger Rayleigh length what will be achieved by adapting the conditions of the incident ray at the focalization element. In this case the cutting quality increases but the cutting speed decreases. The advantage of high intensity gets lost. The dynamic beam shaping is known from the electron beam, and already applied in laser hardening and welding applications using galvanometer scanners. While the galvo-systems reached the physical limitations, the frequency is not high enough to achieve the desired effects. Resonance galvanometer scanners are limited by the atmosphere damping, too.This paper will introduce a new possibility of dynamic beam shaping, using MEMS technology in a low pressure atmosphere. It describes the reached steps to transfer the technology from display and sensor applications with low apertures and laser power to laser material applications with large apertures and high laser power. Finally, the technology possibilities are disclosed for the complete field of laser application.Since the power of continuous wave laser sources have reached one kilowatt, beam shaping is an important topic in the sector of laser material processing. The high intensity allows the increase of process speed, but the extreme local overheating often decreases the quality. Typically beam shaping solutions use a static beam adaptation by optical elements. For laser cutting for example, the increase of sheet thickness requires larger Rayleigh length what will be achieved by adapting the conditions of the incident ray at the focalization element. In this case the cutting quality increases but the cutting speed decreases. The advantage of high intensity gets lost. The dynamic beam shaping is known from the electron beam, and already applied in laser hardening and welding applications using galvanometer scanners. While the galvo-systems reached the physical limitations, the frequency is not high enough to achieve the desired effects. Resonance galvanometer scanners are limited by the atmosphere damping, too.T...

Laser manufacturing of electrical machines

Laser remote cutting for electrical machine application and a new surface treatment method in order to heal manufacturing related magnetic degradation will be presented and discussed. In comparison to the state of the art laser remote cutting utilizes a brilliant high power solid-state laser producing less thermal and magnetic degradation in the processed part. A process integrated surface treatment additionally reduces the manufacturing related magnetic degradation by up to ten percent. Matter under consideration will be the control of cycle time of exemplary stator tooth geometry as well as the magnetic properties in comparison to conventional techniques.

The most filigree structure made by remote laser cutting

It is well known that the global climate change is the largest challenge for the society of the 21th century. In order for us to manage the resulting consequences, innovative materials for energy efficient applications become more and more important. Open cell metal foam contributes promising solutions to the light weight design, battery applications and renewable energy harvesting. Still, challenges are present concerning the cutting into a defined shape. The remote laser cutting offers a solution for decreasing the production costs as well as the needed component accuracy. Our investigations consider that this technique has a high potential concerning cutting speed which was increased by more than 500 %, compared to state of the art laser separation. Next to that, the contour accuracy was improved as well, resulting in tolerances with less than 30 μm. Together with the forceless process of remote laser cutting, the possibility is given to generate filigree components with a wall thickness less than 0.75 pore sizes. This paper offers insight into the viability of remote laser cutting in overcoming the challenges dealing with mechanical milling or grinding. Investigating the process concerning thermal stress input as well as particle attachments will be the next steps in the future.

Experimental investigation of cutting performance for different material compositions of Cr/Ni-steel with 1 μm laser radiation

Best edge quality for thick metal plates is one of the current main challenges to create a unique selling proposition for laser cutting machines. Various approaches have been used to optimize the cutting performance of different materials. The reported results show in general that when a new material batch is loaded to the laser cutting machine, even of the same material type, diverse results are obtained. These differences have been attributed to fluctuations in the chemical composition of the used alloys. This letter analyses the influence of five different material compositions of Cr/Ni-steel (X5CrNi18-10/1.4301/SUS304/stainless steel) and compares achievable qualities and process windows using a solid state fusion cutting system. A larger process window is observed by increasing sulfur content of the material in this study.Best edge quality for thick metal plates is one of the current main challenges to create a unique selling proposition for laser cutting machines. Various approaches have been used to optimize the cutting performance of different materials. The reported results show in general that when a new material batch is loaded to the laser cutting machine, even of the same material type, diverse results are obtained. These differences have been attributed to fluctuations in the chemical composition of the used alloys. This letter analyses the influence of five different material compositions of Cr/Ni-steel (X5CrNi18-10/1.4301/SUS304/stainless steel) and compares achievable qualities and process windows using a solid state fusion cutting system. A larger process window is observed by increasing sulfur content of the material in this study.

Inline High Speed Laser Cutting of Band Material

Laser cutting is introduced as an alternative technique to manufacture typical metallic punching and bending parts. Assets and drawbacks of high speed laser cutting technologies like Remote Laser Cutting and laser fusion cutting by means of a high dynamic form cutter are discussed. Finally, the concept of the world´s first industrial inline reel to reel laser cutting machine for metal strips is presented.