Quality detection and control during laser cutting progress with coaxial visual monitoring

A system of coaxial visual detection and closed-loop control is developed in laser cutting to automatically optimize cutting speed to obtain best cutting quality. The sparks behavior is observed under different cutting speeds by side visual monitoring. It is proved that the maximum number of pixels of various radiation brightness ranges of the coaxially detected sparks corresponds to the optimal cutting speed, represented by the lowest bottom roughness on cut face. By coaxial visual monitoring of cutting front and sparks, the standard deviations of shape parameters of cutting front and the average length of certain brightness range of sparks are, respectively, used as the signals for cutting defects and the bottom roughness. The results show that the optimal cutting speed for free defect and low bottom roughness could be determined and kept on-line by the developed system.