Trim-cut technique for analysis of melt flow dynamics in industrial laser cutting machine

Abstract

Several studies in laser cutting literature have demonstrated that quality aspects of the laser cut edge, such as dross attachment, surface roughness and striation pattern, are highly influenced by the melt flow dynamics. Therefore, in order to visualise the laser cutting process, the trim-cut technique was conceived several decades ago and has been continuously improved by different authors. This tool provides great opportunities to enhance the understanding of the process, such as the origin of quality deterioration, and might help to identify solutions for process improvement. Nevertheless, investigations on laser flame cutting of mild steel are scarce. Within this paper, the design aspects of a setup for high-speed process observation are discussed in detail. The influence of trim-cut parameters on the quality of an obtained cut edge of 15 mm mild steel is investigated. Since the combination of the replacement edge distance and trim-cut width considerably influences the quality of a cutting edge, the similarity of a trim-cut edge with a normal cut edge is examined. A replacement edge distance of 500 µm and a trim-cut width of 50 % are defined as the most suitable set of trim-cut parameters for further high-speed observation of mild steel cutting. The melt flow dynamics of the laser flame cutting process using a commercial 4 kW industrial fiber laser cutting machine are visualised by means of a high-speed imaging system with a frame rate of up to 15 000 fps which allows estimating the velocity of the melt flow inside the cutting front as 5 m/s.