Laser-Driven Programmable Metal Transfer in GMAW

Conventional pulsed laser-enhanced gas metal arc welding (GMAW) employs a single fiber laser focused and aimed on the droplet neck position to produce a laser recoil force and thus ensure the droplet detachment despite the amperage of the welding current. One drop per laser pulse metal transfer is obtained, and the droplet deflects away from the wire axis along the laser incident direction. This implies that the droplet trajectory may also be controlled if the direction of the laser recoil force can be adjusted. Such a controllability is expected to bring an entirely new capability to the GMAW process: active control on the weld beam geometry. To this end, double-sided, laser-enhanced GMAW was proposed and experimentally verified in this paper. The two lasers were symmetrically positioned, and both aimed at the droplet neck. The laser pulse peak power, duration, and pulse phase of the two lasers can all be programmed to regulate the laser recoil forces. The metal transfer under twin laser irradiations (same laser pulses and phases) was first verified. Then the effectiveness on controlling the droplet trajectory of three proposed control strategies — peak power matching, peak width matching, and phase matching of the two lasers — were evaluated. The results showed laser peak power matching is optimal for obtaining desired droplet trajectory. Since the laser can be easily controlled in real time, the transfer frequency, droplet size, and trajectory can all be adjusted in real time, and the metal transfer evolves into programmable transfer.