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Besides water jet pressure and velocity, another crucial factor affecting water jet velocity is nozzle diameter. These three factors combined have a significant impact on water jet cutting, directly affecting its efficiency. Therefore, to better utilize high-performance waterjet cutting tools, let's understand the extent of the nozzle diameter's influence.

While cutting speed and depth increase as nozzle exit diameter decreases, reducing the nozzle diameter under certain pressure will cause the jet to atomize near the nozzle due to air entrainment, resulting in a loss of cutting ability. However, as the nozzle diameter increases (0.1mm to 0.4mm), the cutting depth decreases. A nozzle exit diameter of 0.1–0.3mm is recommended for cutting. Additionally, while cutting speed and depth decrease with increasing nozzle diameter, the kerf width increases, meaning the amount of material damaged per unit time increases.

Under the same pressure conditions, comparing the cutting quality of materials processed with nozzles of 0.1 mm and 0.4 mm diameter, it was found that as the nozzle diameter increased, the kerf widened, the chip size increased, and the kerf quality (roughness) also increased significantly. It can be assumed that the total energy relationship of increasing material fragmentation with increasing jet power remains unchanged. Although both increasing jet pressure and nozzle diameter increase jet power, their effects are quite different. The former significantly improves cutting speed and depth of cut, while the latter only increases the amount of broken material (n), while decreasing cutting speed and depth of cut.

However, due to the increased nozzle diameter, the contact area of the jet on the processed material increases, which increases the material's crush resistance, leading to a decrease in cutting speed and depth of cut. Therefore, when using jets for cutting operations, increasing jet pressure is an effective way to improve efficiency. However, for jet cleaning, rust removal, and delamination operations, the depth of cut coefficient is almost negligible, and the more important factor is the jet area. Therefore, when the jet pressure meets cleaning requirements, increasing the nozzle diameter will increase the operating speed more effectively.