Abstract
A new procedure of in-process monitoring and adaptive control is developed for micro-spot welding of 0.1-mm-thick copper sheets with combined beams of an AO Q-switched second harmonic YAG laser and a pulsed fundamental YAG laser. The objective of this method is to consistently produce fully penetrated welds stably. The pulse width of the fundamental YAG laser is controlled at 0.15-ms intervals during laser irradiation according to the neural network judgment of reflected beam and heat radiation from each processing area. This is accomplished by using a database of these values corresponding to the diameters of spot-weld fusion zones on the back surface. Through investigation of 200 samples, incomplete melting was detected in 7 samples under the laser irradiation conditions used conventionally. On the other hand, fully penetrated spot welds were stably produced in 200 samples subjected to the proposed in-process monitoring and adaptive control.
