Droplet transfer control for gas metal arc welding

Conventional pulsed current gas metal arc welding (GMAW) does not precisely control the droplet detachment instant and droplet size. For 3D welding based rapid prototyping, the droplet detachment instant and droplet size need to be precisely controlled. In the proposed approach, an oscillation of the droplet is excited as an active action by switching the current from the peak level to the base level. The excited oscillation of the droplet is monitored by a high-frame rate vision system. When the droplet moves downwards, the current returns back to the peak level. The droplet is detached by a combination of a downward momentum of the droplet and an increase in the electromagnetic force, which serves as a detaching force. Hence, the droplet detachment can be precisely controlled. Experiments show that the droplet can be accurately controlled by the proposed approach.