ROBUST IN-PROCESS MONITORING OF PULSED-LASER SPOT-WELDING USING A POINT INFRARED-SENSOR

Many manufactured goods employ pulsed laser spot welding in joining an d it is important to monitor the weld quality. The weld quality is hig hly related to the thermal history of the weld and there have been man y trials to monitor the quality using an infrared (IR) sensor. Though the emitted thermal radiation is a function of the emissivity and the surface temperature, the measuring condition has an important influenc e on the detectable radiation. To increase the reliability of monitori ng, it is useful to find the robust feature that is immune to the chan ge of measuring condition. This paper suggests an in-process monitorin g method using a point IR sensor for the pulsed laser spot welding of thin metal sheet. The suggested monitoring method is robust to the cha nge of the measuring condition and it can detect the variation of the absorbed energy as well as any serious defect in the weldment.