Laser welding control by monitoring of plasma

Hana Chmelickova; Hana Sebestova; Martina Havelkova; Lenka Rihakova; Libor Nozka

doi:10.1117/12.2021864

13 May 2013 Laser welding control by monitoring of plasma

Hana Chmelickova, Hana Sebestova, Martina Havelkova, Lenka Rihakova, Libor Nozka

Proceedings Volume 8788, Optical Measurement Systems for Industrial Inspection VIII; 87882P (2013) https://doi.org/10.1117/12.2021864
Event: SPIE Optical Metrology 2013, 2013, Munich, Germany

Abstract

Deep penetration welding is a typical industrial application of high power lasers, where plasma can be generated above the keyhole. Thanks to the plasma plume presence welding process can be controlled on-line by means of the plasma intensity measurements. Various on-line monitoring methods have been developed in research centers all over the world. Goal of them is to enable promptly operator action to avoid enormous economical looses if un-expected defect is detected. Our laboratory was participated in project CLET - “Closed loop control of the laser welding process through the measurement of plasma” as a responsible partner for developed system testing both in the laboratory with pulsed Nd:YAG laser and in the real welding facility with high power continual CO₂ laser. Control system is based on the electron temperature computation from the relative intensities of couple of emission lines belong to certain metal ion present in plasma plume. Our experiment was realized using Ocean Optics HR2000+ spectrometer within the stainless steel tube longitudinal welding. Several couples of emission lines were tested to acquire a good signal at actual welding conditions. Then power calibration was made to obtain the electron temperature dependence on increasing power. Samples were prepared for microanalysis and measured by laser confocal scanning microscope to find optimal power range for full penetrations achieving without thermal distortion of the tube or weld humping. Numerical model of the remelted area cross section was made to display temperature distribution dependence on increasing power.

Citation Download Citation

Hana Chmelickova, Hana Sebestova, Martina Havelkova, Lenka Rihakova, and Libor Nozka "Laser welding control by monitoring of plasma", Proc. SPIE 8788, Optical Measurement Systems for Industrial Inspection VIII, 87882P (13 May 2013); https://doi.org/10.1117/12.2021864

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