A plasma cloud charge sensor for pulse keyhole process control

Keyhole plasma arc welding achieves much deeper penetration than do all oth er existing arc welding processes. Because of its ability to penetrate thic ker material, the control of the keyhole in plasma arc welding becomes crit ical. From an analysis of the physical process., a sensor to detect the sta te of the keyhole for keyhole process control has been proposed and develop ed. This sensor measures the electrical effect of the plasma cloud generate d during keyhole plasma arc welding. It is found that the plasma cloud, whi ch rapidly decreases to zero upon establishment of the fully penetrated key hole, can be used to detect the state of the keyhole reliably. The effectiv eness of the proposed sensor for detecting the keyhole state has been verif ied during pulse keyhole plasma arc welding.