THE INFLUENCE PATTERNS OF NOZZLE DESIGN AND TECHNOLOGICAL PARAMETERS OF GAS-ASSISTED LASER CUTTING ON THE STAGNANT PRESSURE OF ASSISTING GAS

The paper proposes and implements a methodology for experimentally measuring the size of the action zone and the magnitude of the pressure that ensures the removal of the liquid phase during gas-assisted laser cutting and is created by the flow of the assist gas on the surface of the part. During the research, based on a serial LTS-PRO-6000-1530-LD machine from Aramis, serial singlechannel and two-channel nozzles from Thermacut with an outlet diameter of 1.5 mm were installed in the optical head of the machine. In the experiments, air with a gauge pressure at the nozzle inlet of 0.5 MPa and 1 MPa was used as an assisting gas. The regularities of the influence of the nozzle design, the stand-off between the nozzle and the workpiece, and the gauge pressure at the nozzle inlet on changes in the diameter of the supersonic jet of the assist gas and the amount of pressure it creates exerting the surface of the workpiece under the technological conditions of gas-assisted laser cutting were established. The obtained array of experimental data showed that the traditional approach to using the existing range of serial nozzles makes it problematic to effectively design gas-assisted laser cutting processes for maximum productivity and reproducibility of cut quality. This is related to complex phenomena in the supersonic jet, which determine the high sensitivity of the pressure value on the part's surface to changes in the nozzle geometry and process technological parameters. As a result, there is no understanding of what kind of pressure is created by the jet of assist gas in the cutting zone under certain technological parameters of the process. The methodology proposed in this paper makes it relatively easy to create "passports" for the nozzles that each machine is equipped with. Thus, it becomes possible to take into account the real value of the assisting pressure field in the cutting zone when designing a specific technological process. As a result, productive high-quality cutting is more reliably ensured on a given technological installation and the level of process reproducibility is improved. Experimental verification has demonstrated a fairly good correlation between the local stagnant pressure of the assisting gas jet and the maximum laser cutting speed and cut quality.