Monitoring the laser cutting process by IR thermography

Metal cutting by computer assisted laser is more and more utilized in advanced manufacturing. The increased accuracy, the non-contact processing, the higher productivity and the decrease of energy demand are some of the benefits that make competitive this technology in respect to the most traditional ones like the rotating tools or sewing. Typically, such systems are composed by a powerful diode sourcing light in continuous mode or periodically pulsed. The light is collected by an optical fiber and focused by the optical system on the manufact to be cutted. The optical system, on its turn, is mounted on a 2/3-axis head. Typical wavelength is around 1064 nm and average power ranges from 1 to several kW. Notwithstanding those appealing features, there is the concern on the effects of the high temperature developed during the melting of the metal on the cutting zone, and the surrounding as well, that can lead to the degradation of the mechanical characteristics of the final product. Several authors have proposed different kind of analysis on the Heat Affected Zone (HAZ): measure of the tensile strength, Vickers hardness, SEM and optical microscopy analysis. Correlation have been drawn with the speed of the laser head and the power of the source with the extension of the HAZ. The paper propose to utilise an IR camera to monitor the temperature in the surrounding of the cutting zone and a model to fit the data collected by the IR camera itself.