In-process monitoring of the cutting front of CO₂ laser cutting with off-axis optical fibre

A new method is presented in this study to test a way that can effectively provide detailed information on the surface morphology during CO₂ laser cutting by directly measuring the emitted light from the cutting front. The system consists of a copper tube, glass fibre, polymer fibre and photodiode sensor. In this study, the laser power was modulated from 50 Hz to 300 Hz to disturb the natural burning cycle during gas assisted CO₂ laser cutting. The optical fibre was set at 75° to the cutting direction. The wave frequency of the detected signal was very close to the striation frequency of the cut surface, which shows that the sensing system designed and developed in this research can effectively in-process monitor the CO₂ laser cutting process.