Development of in-process monitoring system for laser welding

A novel in-process monitoring system employing two detectors set above the work at different aiming angles of 5 and 75 degrees was developed to detect whether or not the CO2 laser welding is of full penetration through the back surface of the steel sheets. The acquired signal involved AC components with frequencies up to approximately 10kHz of the emission of the laser-induced plasma in the plume and in the keyhole. The mean square value of the AC signal obtained by using 75-degree sensor in the full-penetration welding was much larger than that of the partial the full-penetration welding, showing that full penetration welding can be monitored with high accuracy by using 75-degree sensor.A novel in-process monitoring system employing two detectors set above the work at different aiming angles of 5 and 75 degrees was developed to detect whether or not the CO2 laser welding is of full penetration through the back surface of the steel sheets. The acquired signal involved AC components with frequencies up to approximately 10kHz of the emission of the laser-induced plasma in the plume and in the keyhole. The mean square value of the AC signal obtained by using 75-degree sensor in the full-penetration welding was much larger than that of the partial the full-penetration welding, showing that full penetration welding can be monitored with high accuracy by using 75-degree sensor.