Product Code: ICA11_203

Closed Loop Control of Laser Welding Using an Optical Spectroscopic Sensor for Nd:YAG and CO2 Lasers
Authors:
Ali Riza Konuk, University of Twente; Enschede Netherlands
Ronald Aarts, University of Twente; Enschede Netherlands
Bert Huis in t Veld, University of Twente; Enchede Netherlands
Teresa Sibillano, CNR-IFN UOS Bari; Enschede Italy
Domenico Rizzi, CNR-IFN UOS Bari; Bari Italy
Antonio Ancona, CNR-IFN UOS Bari; Bari Italy
Presented at ICALEO 2011

Recent developments in laser joining show the applicability of spectral analysis of the plasma plume emission to monitor and control the quality of weld. The analysis of the complete spectra makes it possible to measure specific emission lines which reveal information about the welding process. The subsequent estimation of the electron temperature can be correlated with the quality of the corresponding weld seam. A typical quality parameter, for laser welds of stainless steel, is the achieved penetration depth of the weld. Furthermore adequate gas shielding of the welds has to be provided to avoid seam oxidation .
In this paper monitoring and real-time control of the penetration depth during laser welding is demonstrated. Optical emissions in the range of 400nm and 560nm are collected by a fast spectrometer. The sensor data are used to determine the weld quality of overlap welds in AISI 304 stainless steel sheets performed both with CW Nd:YAG and CO2 lasers. A PI-controller adjusts the laser power aiming at a constant penetration. Optical inspection of the weld surface and microscopic analysis of weld cross sections were used to verify the results obtained with the proposed closed-loop system of spectroscopic sensor and controller.
In this paper monitoring and real-time control of the penetration depth during laser welding is evaluated. Process emissions in the range of 400nm and 560nm are collected by a fast spectrometer. The sensor data are used to determine the weld quality of overlap welds in AISI 304 stainless steel sheets performed both with CW Nd:YAG and CO2 lasers. A PI-controller adjusts the laser power aiming at a constant penetration. In order to prevent oxidation the performance of the shielding gas supply is monitored and lack of shielding gas is indicated by the controller. Optical inspection of the weld surface and microscopic analysis of weld cross sections verify the results obtained with the proposed closed-loop system based on a spectroscopic sensor and controller.