The use of fibre optics for in-process monitoring of laser cutting

Abstract

Laser cutting is a thermal process. Thus the melt pool temperature is likely to be an indicator of cut quality and may be useful for the control of the process. Since light intensity emitted from a radiant source is proportional to the temperature to the fourth power, the light intensity signal could be a sensitive control signal. Special techniques using fibre optics and photodiodes were used to directly monitor the light emitted from the melt front at the cut face. These signals were analysed and related to the edge striation pattern, dross adhesion and kerf width. The design of an alarm system for the in-process inspection of laser cut quality is discussed.Laser cutting is a thermal process. Thus the melt pool temperature is likely to be an indicator of cut quality and may be useful for the control of the process. Since light intensity emitted from a radiant source is proportional to the temperature to the fourth power, the light intensity signal could be a sensitive control signal. Special techniques using fibre optics and photodiodes were used to directly monitor the light emitted from the melt front at the cut face. These signals were analysed and related to the edge striation pattern, dross adhesion and kerf width. The design of an alarm system for the in-process inspection of laser cut quality is discussed.