Model Based Metal Transfer Control

In pulsed gas metal arc welding (pulsed GMAW) current pulses are used for detaching drops at the tip of the electrode. To obtain a high weld quality one drop should be detached for every pulse, and moreover, the amount of energy used for detachment should be kept at a minimum. Thus, each pulse must be strong enough to detach each drop, but on the other hand, each pulse should be as low as possible. The minimal pulse required to detach a drop depends on the size of the drop, but during welding the size of the drops change with disturbances in the process. Traditionally, in pulsed GMAW a fixed pulse frequency and a fixed pulse shape are used. Because of disturbances strong current pulses are used to obtain the one drop per pulse objective, but minimal pulses are not obtained. In this work a novel approach is presented which provides minimal pulse energy and one drop per pulse. A variable time interval between the pulses is used to ensure a fixed drop size at initiation of each pulse, and this makes it possible to minimize the pulses.