Acoustic and Optical Monitoring of High-Power CO₂ Laser Cutting

Abstract

In this paper, the development of a monitoring system for high-power CO2 laser cutting of thick steel plates (>15 mm) is reported. The aim of this system is to increase the robustness and autonomy of the laser cutting process of thick plates, which is still characterized by more narrow process windows compared to cutting of thin sheets. The applicability for monitoring purposes of two types of sensors is investigated: the acoustic microphone and the photodiode. For both types, correlation between the sensor output and the cut quality is investigated. Both contour cutting and piercing are covered in the study. The full penetration of the piercing can be monitored by both sensors. Furthermore quantitative relations between cut quality parameters and photodiode signal parameters could be determined: the mean level of the photodiode signal correlates well with the drag of the striations and dross formation, whereas the standard deviation proves to correlate well with the occurrence of burning defects and the cut edge roughness.

Analysis of Photodiode Monitoring in Laser Cutting

“…In addition, acoustic signals have also been employed for laser cutting monitoring. For instance, De Keuster et al [17] employed both acoustic and optical signals, for ensuring the full penetration of the laser beam. Kek and Grum [18] also employed acoustic signals for monitoring laser cutting, after the application of the appropriate band filter to avoid the contribution of the assist gas flow.…”