Precautions For Using High Speed Laser Cutting Nozzles

Due to the small size and susceptibility to damage, the laser nozzle of the thin sheet laser cutting machine is generally made of copper and needs to be replaced frequently. Therefore, fluid dynamics calculations and analysis are not performed. When in use, a certain pressure Pn (gauge pressure Pg) of gas is introduced from the side of the nozzle, referred to as nozzle pressure, and is emitted from the nozzle outlet, reaching the workpiece surface after a certain distance, with the pressure referred to as cutting pressure Pc. Finally, the gas expands to atmospheric pressure Pa.

Research has shown that as Pn increases, the gas flow velocity increases, and Pc also increases. This relationship can be expressed by the formula V=8.2d2(Pg+1), where V is the gas flow rate in L/min, d is the nozzle diameter in mm, and Pg is the nozzle pressure (gauge pressure) in bar.

Thin sheet laser cutting machines have different pressure thresholds for different gases. When the nozzle pressure exceeds this threshold, the gas flow transitions from subsonic to supersonic speed, forming a normal oblique shock wave. This threshold is related to the ratio of Pn to Pa and the degrees of freedom (n) of the gas molecules. For example, for oxygen and air, n=5, and the threshold Pn can be calculated as 1 bar × (1.2)3.5=1.89 bar.

When the nozzle pressure is higher at Pn/Pa=(1+1/n)1+n/2 (Pn at 4 bar), the oblique shock wave changes to a normal shock wave, resulting in a decrease in cutting pressure Pc, reduced gas flow velocity, and the formation of eddies on the workpiece surface, weakening the effectiveness of removing molten material and affecting the cutting speed. Therefore, nozzles with conical holes and small circular holes at the end are often used for oxygen, with nozzle pressure typically kept below 3 bar.

Hot Tags: precautions for using high speed laser cutting nozzles, China, suppliers, manufacturers, customized, price, cheap, in stock, free sample, 420044 hyp, 220188 hyp, 220819 Nozzle, 220183 Shield, ht220842, Powermax 45xp Fine Cut Consumables