When using Gas Metal Arc Welding in spray transfer mode, what critical parameter must be controlled to prevent stubbing and ensure stable droplet detachment?

The critical parameter that must be controlled to prevent stubbing and ensure stable droplet detachment when using Gas Metal Arc Welding (GMAW) in spray transfer mode is Voltage. Gas Metal Arc Welding is an arc welding process where an electric arc forms between a continuously fed consumable wire electrode and the workpiece, with a shielding gas protecting the weld pool. In spray transfer mode, molten metal detaches from the electrode tip as a continuous stream of fine, small droplets that are propelled across the arc to the weld pool. Stable droplet detachment refers to the consistent and smooth formation and transfer of these molten droplets, which is essential for a steady arc and high-quality weld. Stubbing occurs when the consumable electrode wire physically contacts the weld pool or workpiece due to an excessively short arc length, leading to an erratic arc, increased spatter, and poor weld quality. Voltage directly controls the arc length in GMAW. If the voltage is too low for the set wire feed speed, the arc length becomes too short, causing the electrode tip to contact the molten weld pool prematurely, resulting in stubbing. Conversely, maintaining the correct voltage ensures an optimal arc length. This optimal arc length provides sufficient space and time for the molten metal to detach as uniform droplets and transfer efficiently across the arc, preventing physical contact with the weld pool and thus ensuring stable droplet detachment and a consistent spray transfer.