Study on water jet stability and processing morphology of groove cutting using water jet guided laser

In order to reveal the formation process of straight grooves using water jet guided laser (WJGL) technology and analyze the reasons for the formation of straight groove morphology, the stability of water jet in the straight groove were studied and the internal morphology of the straight groove obtained by WJGL processing was characterized. Firstly, the stability of water jet moving in straight grooves with different depths (0.5–50 mm), lengths (1–20 mm), widths (0–200 μm), inlet velocity (100–300 m/s), bottom shapes (flat, inclined), and types (through grooves, blind grooves) were studied through numerical simulation. Subsequently, the influence of water jet stability on the removal of material from the groove bottom was analyzed based on the guiding effect of water jet on laser. Then, different types of straight grooves (long blind groove, long through groove, short blind groove, short through groove) were processed using WJGL technology with different cutting cycles (2–10 times), and the internal morphology of the grooves was characterized through industrial computed tomography (CT). Finally, the reasons for the formation of the morphology inside the groove were analyzed based on simulation and experimental results. The results indicate that the fracture of the water jet in the blind groove includes when the water jet moves to the side wall, when the water jet reaches a stable length, and when the liquid is discharged from the narrow groove. The phenomenon of “inclined propagation” occurs when WJGL passes through the intersection of the flat and inclined bottom surfaces of the groove. The phenomenon of “inclined enhancement” occurs when WJGL is used to process the inclined bottom surface of the groove. This article reveals for the first time the flow morphology of micro water jet in straight grooves, and analyzes the reasons for the formation of groove morphology, which has guiding significance for the process optimization and practical application of WJGL technology in straight groove processing.