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In Situ Reflectivity Measurement Applied to the Cutting of Metals with Infrared Laser Beams
F. Breaban, J.F. Coutouly, P. Deprez and P. Vantomme

Current industrial requirements concerning the quality of laser cutting of materials like metals, polymers or composites have reached such a level that they suppose a global control of the process. In the field of the cutting by infrared (IR) laser beam, many parameters can influence the quality of the finished product. One key-parameter is the reflectivity, it is the subject of our study. This parameter is very fluctuating. In fact, it depends on the wavelength of the beam, its power, its electric field vector but also it depends on the material itself (chemical composition, roughness, temperature). In that paper we have chosen to study the reflectivity and its changes because among all the thermo-physical quantities it plays a major role, and its influence echoes on the performance of cutting machines as well as on quality of final products. In this study we present the principles of an original device for measurement of reflectivity, device which works in situ conditions, therefore well adapted to the particular problem of laser cutting. Accurate values of reflectivity for various types of steels are determined using this device and will be given.

Keywords: Laser cutting, steel, reflectivity, real-time measurement, infrared, CO2 laser

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