研究目的
To investigate the melt flow dynamics and the velocity distribution of melt waves with variation of cutting velocity and assist gas pressure by recording the cutting front with a high-speed camera aligned in cutting direction through the evolving cut kerf.
研究成果
The use of an algorithm for the evaluation of velocity distributions of melt waves on the cutting front apex recorded by in-situ high-speed video-diagnostics enables the correlation between melt flow dynamics and cut flank quality. The results show that the number of melt waves increases with higher cutting velocity and decreases when reducing the assist gas pressure at medium cutting velocity. A high amount of cumulated melt wave counts does not necessarily lead to a low surface roughness. Overall, stable and fast melt waves are beneficial, but not necessarily sufficient to achieve a good cut flank quality.
研究不足
The evaluation of the examined cutting parameters shows that a high cutting velocity (vc=2.8 m/min and 3.8 m/min) while simultaneously using a high assist gas pressure (p=20 bar) is appropriate. However, the study is limited to 6 mm thick stainless-steel samples and may not be directly applicable to other materials or thicknesses.
1：Experimental Design and Method Selection:
The experiments were carried out using a 12 kW disc laser with a wavelength of 1030 nm at an output power of P=5 kW. A Precitec HP SSL cutting head was used and the fiber (? 200 μm) guided laser beam was collimated and focused with focal lengths of 100 mm and 250 mm, respectively. This configuration provides a focal diameter of 500 μm. A conical-cylindrical nozzle with a diameter of 5 mm was mounted and a stand-off distance of 0.7 mm was adjusted. The focus position was set 4 mm below the upper surface of the sample (z=-4 mm). Different combinations of nitrogen assist gas pressures (p) and cutting velocities (vc) were used to cut 6 mm thick stainless-steel samples.
2：7 mm was adjusted. The focus position was set 4 mm below the upper surface of the sample (z=-4 mm). Different combinations of nitrogen assist gas pressures (p) and cutting velocities (vc) were used to cut 6 mm thick stainless-steel samples.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: 6 mm thick stainless-steel samples were used.
3：List of Experimental Equipment and Materials:
A 12 kW disc laser (Trumpf, TruDisk 12002), Precitec HP SSL cutting head, high-speed camera (Photron SA 5), NIKON 200 mm macro lens.
4：Experimental Procedures and Operational Workflow:
The direction of observation was set in cutting direction through the evolving cut kerf. The region of interest of the used high-speed camera was set to 64 x 376 px, to facilitate a frame rate of 140,000 fps. By using a NIKON 200 mm macro lens a spatial resolution of 20 μm/px was enabled.
5：Data Analysis Methods:
An advanced algorithm was developed to extract the velocity distribution of occurring brightly shining melt waves on the cutting front out of the high-speed video-recordings.
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