AC pulsed MIG welding is an appropriate process to join aluminium alloy sheets for its great gap tolerance and low heat input to avoid burn through. However, in case of very high speed welding the low heat input is no longer an advantage since lack of penetration becomes a problem. Irradiating laser beam to the vicinity of arc can solve this problem and adjustment of the laser power can control the penetration. As a result, thin aluminium alloy sheets can be jointed at a high speed of 4 m/min with sufficient gap tolerance. Moreover, investigation of the effect of laser beam diameter on the welding result of thin sheets indicates that the defocused laser beam with a diameter of several millimetres can further improve the bridging ability for joint gap and tolerance for torch aiming deviation. Consequently, high power diode laser with relatively thick beam waist is suitable for this application and a diode laser/AC pulsed MIG hybrid welding robot system has been developed.
