Abstract
This paper presents a new procedure for in-process monitoring and adaptive control that has been developed for micro-spot lap welding of A3003 aluminum alloy sheets of 0.1 mm and 1 mm in thickness. The objective of this process is to consistently produce sound laser partial-penetration welds. Observations revealed that the reflected laser beam and the heat radiated from the weld area were effective as process-monitoring signals in detecting melting, keyhole formation and hole generation during laser irradiation. Laser pulse width and peak power during the irradiation of a fundamental YAG laser beam were controlled at regular 0.15ms intervals on the basis of the heat radiation signal being employed to detect hole generation. Investigation of 20 samples revealed that only four non-bonded welds with holes were formed under conventional conditions. In contrast sound partially penetrated spot welds were produced in all 20 samples subjected to laser lap welding under the proposed in-process monitoring and adaptive control method.
