A novel controlled high-dynamic braking effect-driven droplet transition in GMAW

Abstract

As a conventional arc-depositing process, limited by the strong heat-mass coupling characteristics, gas metal arc welding (GMAW) is difficult to adapt to precision deposition requiring low heat input. To solve this problem, a novel high-dynamic locking-releasing wire feeding method driven by linear actuator was proposed and a compact mechanical structure was developed. The braking effect of the high-dynamic locking-releasing action of the wire feeding allows the molten droplets to acquire additional stronger drive forces, including the inertial force induced by the sudden locking of the wire and the elastic potential energy induced by the bending of the wire, both of which facilitate the droplet transition. The results show that the indirect ‘energy storage’ effect of the high-dynamic locking-releasing wire on the droplets enabled a stable one-droplet-per-pulse (ODPP) spray transfer with a transition frequency of 60 Hz at low heat input. The dynamic transition mechanism of the above ODPP process was revealed by kinetic simulations of the droplet. In addition, a new non-stationary re-locking (NSRL) control strategy was introduced, which further empowered droplets with greater inertial force through the sharp braking effect, thus significantly increased the transition frequency of the molten droplets (~150 Hz). Further, by combining the above strategy with the growth characteristics of droplets under the specific pulsed currents, ODPP spray transfer with frequencies up to 190 Hz was achieved. These promising results indicates the promise of this method for precision arc deposition and even wire arc additive manufacturing at low heat input.