Coaxial camera-based monitoring of fiber laser cutting of thick plates

Abstract

Laser cutting is a conventional and well-established industrial process within the sheet metal working domain. However, processing of thick plates remains a major problem due to the limited process window. Real-time monitoring for adaptive control might significantly decrease the risk of a cut fail. Up to this point, most studies were mainly focused on the design of monitoring systems for laser cutting with CO2 lasers and limited to either fusion or flame cutting. Nowadays, laser cutting by means of fiber lasers has become the industrial method of choice, however, no tailored generic monitoring solutions for this process have yet been reported in the literature. This paper investigates a coaxial camera-based monitoring system for 4 kW ytterbium fiber laser cutting of 15 mm mild steel and 12 mm stainless steel plates. Experiments at various cutting speeds, resulting in different cut edge quality outcomes, have been conducted. Intensity, geometrical and variability features of the obtained images have been calculated and analyzed. The correlation between the cut specimen quality and process images obtained by means of a high-speed visual camera is discussed for both fusion and flame cutting.