Measurement and estimation of weld pool surface depth and weld penetration in pulsed gas metal arc welding

The weld pool surface may contain sufficient information to determine weld penetration. In this study, a high-speed camera-based vision system was used to image the weld pool surface during gas metal arc welding (GMAW). To calculate the depth of the weld pool surface from the acquired image, a calibration procedure is proposed to determine the parameters in the calculation equation. Welding parameters were designed to conduct a series of pulsed GMAW (GMAW-P) experiments. Modeling using experimental data shows that the change of the weld pool surface depth during the peak current period can predict the depth of the weld penetration with adequate accuracy. However, a direct application of this result is complicated by the need for a vision system. To find a method that can be used to monitor the weld penetration using signals that are easily measurable in manufacturing facilities, a possible relationship between a change in weld pool surface depth and a change in arc voltage was analyzed. The analysis suggested that the change in arc voltage during the peak current period may reflect accurately the change in weld pool surface depth during the peak current period. As a result, it is proposed that the depth of the weld penetration be determined from the change in arc voltage during the peak current period. The modeling result shows that the change in arc voltage during peak current can indeed provide an accurate prediction for the depth of the weld penetration during GMAW-P.