A plasma cloud charge sensor for pulse keyhole process control

Keyhole plasma arc welding achieves much deeper penetration than do all other existing arc welding processes. Because of its ability to penetrate thicker material, the control of the keyhole in plasma arc welding becomes critical. From an analysis of the physical process., a sensor to detect the state of the keyhole for keyhole process control has been proposed and developed. This sensor measures the electrical effect of the plasma cloud generated during keyhole plasma arc welding. It is found that the plasma cloud, which rapidly decreases to zero upon establishment of the fully penetrated keyhole, can be used to detect the state of the keyhole reliably. The effectiveness of the proposed sensor for detecting the keyhole state has been verified during pulse keyhole plasma arc welding.