LAUSR

Abstract It is known to all that the energy density of laser beam is depended on the laser focus size in laser processing. A stable laser focus size is important to the quality of product either in laser welding or in laser additive manufacturing. The laser focus size closely relates to the laser defocusing distance, and it is necessary to sensor the laser defocusing distance in order to ensure the stability of the laser focus size. But in the process of laser processing, the measurement accuracy of laser defocusing distance by optical and acoustic sensor is easy to be interfered by the laser manufacturing environment. The electrical signals in laser processing are less affected by environment, which can effectively improve the measurement accuracy. In this study, the plasma charge voltage signal in the laser processing is detected and processed to find out the relationship between the signal and the laser defocusing distance, and to identify the variation of laser defocusing distance in processing. The experiment results show that when the laser defocusing distance deviates, the plasma charge voltage fluctuates regularly with the variation of the deviation amount. This work reveal a regular mathematical relationship between laser defocusing distance and plasma charge voltage. The deviation of laser defocusing distance can be identified using this relation. The verification experimental results show that the maximum recognition error is less than 7.1% when the laser defocusing distance is within the range of 6 mm to 8 mm. This result provides the possibility for the application of laser plasma charge voltage signal in laser focusing distance recognition and controlling. Accordingly, higher measurement accuracy can be obtained for laser defocusing distance, which is conducive to more accurate control of laser defocusing distance and more stable laser processing quality.