Contributo in atti di convegno, 2012, ENG, 10.1117/12.906778

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

Sibillano T., Ancona A., Rizzi D., Mezzapesa F., Konuk A.R., Aarts R., Huis In 't Veld B., Lugarà P.M.

CNR-IFN Istituto di Fotonica e Nanotecnologie, Bari, via Amendola 173, 70126 Bari, Italy Dipartimento Interateneo di Fisica, Università degli Studi e Politecnico di Bari, via Amendola 173, 70126 Bari, Italy University of Twente, Laboratory of Mechanical Automation, 7500 AE Enschede, Netherlands

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 CO 2 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.

High Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications, pp. 82390S–?, San Francisco, CA; United States, 21-26 January 2012

Keywords

Closed-loop control, Cross section, Emission lines, In-process monitoring, Laser power, Macroscopic analysis, ND : YAG lasers, Optical inspection, PI Controller, plasma spectroscopy, Sensor systems, Setpoints, Weld penetrations, Weld surfaces, Welding conditions, Carbon dioxide, Closed loop control systems, Electric welding, Electron temperature, High power lasers, Optical testing, Process monitoring, Spectrometers, Stainless steel, Welds, Laser beam welding

CNR authors

Rizzi Domenico, Mezzapesa Francesco Paolo, Lugara Pietro Mario, Sibillano Teresa, Ancona Antonio

CNR institutes

IFN – IFN - Sede secondaria di Bari