Investigation on the Inert Gas-Assisted Laser Cutting Performances and Quality Using Supersonic Nozzles

In the present work, three different supersonic nozzles were designed and manufactured to operate at various stagnation pressures during laser cutting. Several cutting experiments were performed on stainless steel samples of various thicknesses (2, 4, 6 mm) using a fiber laser of 3 kW with a head adapted to fit with both the proposed supersonic nozzles and a commercial reference conical nozzle. The flow through these nozzles was numerically modeled and compared with the Schlieren visualization measurements. The mass flow rate, the Mach number, and the pressure distributions were selected in detail in order to analyze the dynamic characteristics of the exit jet and to comparatively assess the achieved cutting quality (roughness perpendicularity) and capability (maximum thickness, cutting speed). The numerical and the experimental results were found to be in high agreement in terms of the flow structure and mass flow rate. In addition, a significant reduction of the assistance gas consumption of up to 65% on average was achieved by using supersonic nozzles as opposed to conical ones, accompanied with the decrease of the operating pressure and the increase of the cutting speed.