Spectroscopic closed loop control of penetration depth in laser beam welding process

Eckhard Beyer (Editor), Teresa Sibillano, Antonio Ancona, Timothy Morris (Editor), Domenico Rizzi, Francesco Mezzapesa, A.R. Konuk, Ronald G.K.M. Aarts, Bert Huis in 't Veld, Pietro Mario Lugara

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In-process monitoring and feedback control are fundamental actions for stable and good quality laser welding process. In particular, penetration depth is one of the most critical features to be monitored. In this research, overlap welding of stainless steel is investigated to stably reproduce a fixed penetration depth using both CO2 and Nd:YAG lasers. Plasma electron temperatures of Fe(I) and Cr(I) are evaluated as in process monitoring using the measurement of intensities of emission lines with fast spectrometers. The sensor system is calibrated using a quantitative relationship between electron temperature and penetration depth in different welding conditions. Finally closed loop control of the weld penetration depth is implemented by acquiring the electron temperature value and by adjusting the laser power to maintain a pre-set penetration depth. A PI controller is successfully used to stabilize the electron temperature around the set point corresponding to the right penetration depth starting from a wrong value of any initial laser power different than the set point. Optical inspection of the weld surface and macroscopic analyses of cross sections verify the results obtained with the proposed closed-loop system based on a spectroscopic controller and confirms the reliability of our system.
Original languageUndefined
Number of pages8
Publication statusPublished - 2012
EventHigh Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications - San Francisco, CA, USA
Duration: 24 Jan 201226 Jan 2012


ConferenceHigh Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications
Other24-26 January 2012


  • IR-79403
  • EC Grant Agreement nr.: FP7/222279
  • Laser welding
  • closed loop control
  • plasma spectroscopy

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