Stereo analysis on the keyhole and weld pool behaviors in K-PAW with triple CCD cameras

A synchronous visual sensing system was established to observe the topside weld pool, keyhole entrance and keyhole exit at the same time during keyhole plasma arc welding (K-PAW). Complete topside weld pool was captured by a common CCD camera perpendicularly to the welding direction. Meanwhile another two cameras were employed to monitor the keyhole entrance from the rear view and to capture the keyhole exit from the substrate backside, respectively. The evolution process of the weld pool and keyhole behaviors and shapes along with the heat input accumulation were observed. The mechanism of the interactions were discussed and analyzed. Image registration was conducted fusing the weld pool, keyhole entrance and keyhole exit in the same coordinate system. The geometrical dimensions were measured and could reflect the interior intense interactions. Comprehensive investigation of the complicated physical process provided some fundamental and profound understandings.