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Proceedings Paper

Process control in continuous high-power CO2 laser beam welding
Author(s): Bernd Seidel; Jorg Beersiek; Eckhard Beyer
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Paper Abstract

The use of high power CO2 lasers in welding enables processing with high laser intensities at the workpiece which is connected with the formation of a laser induced plasma at the surface of the workpiece. Therefore the effect of deep penetration welding by formation of a plasma filled keyhole and plasma plume above the workpiece is possible, including the risk of plasma shielding, which means strong absorption of the incident laser beam above the workpiece and thus interruption of the welding process. The conditions for ignition of plasma shielding, which is determined by electron density, are mainly influenced by laser intensity, process gas and material. Variations of these parameters have been conducted in order to find limits for the appearance of plasma shielding. Experimental data are used to verify a model concerning the absorption mechanism of a stationary shielding plasma state. The dynamic behavior is treated by time resolved spectroscopic analysis of the light emitted by the plasma above the workpiece yielding monitoring signals that have a strong correlation with the formation of plasma shielding. Based on these investigations a closed-loop process control in continuous high power laser welding has been developed. Using the intensity of a spectral line of laser induced plasma as monitoring signal and the regulation of laser intensity via laser power, plasma shielding can be suppressed. From the industrial point of view increase in economy and reliability of the laser welding process combined with quality improvements which are induced by the application of the plasma shielding controller (PSC) are of great importance. For this reason three examples of PSC application are presented.

Paper Details

Date Published: 7 September 1994
PDF: 11 pages
Proc. SPIE 2207, Laser Materials Processing: Industrial and Microelectronics Applications, (7 September 1994); doi: 10.1117/12.184737
Show Author Affiliations
Bernd Seidel, Fraunhofer-Institut fuer Lasertechnik (Germany)
Jorg Beersiek, Fraunhofer-Institut fuer Lasertechnik (Germany)
Eckhard Beyer, Fraunhofer-Institut fuer Lasertechnik (Germany)


Published in SPIE Proceedings Vol. 2207:
Laser Materials Processing: Industrial and Microelectronics Applications
Eckhard Beyer; Maichi Cantello; Aldo V. La Rocca; Lucien Diego Laude; Flemming O. Olsen; Gerd Sepold, Editor(s)

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