The role of the nozzle
● Through the internal shape of the laser nozzle, adjust the direction of high-pressure airflow and air pressure to maintain the pressure between the workpiece and the nozzle.
● Prevent the molten material of the workpiece from splashing back into the laser head, thus protecting the internal lens of the laser head.
● Provides a capacitive signal to the height adjustment system to ensure stable operation of the height adjustment system.
Types of nozzles
Depending on the gas used, they are generally categorized into single-layer nozzles and double-layer nozzles.
1. Single layer nozzle
● Used for melt cutting, using nitrogen as auxiliary gas, used for cutting stainless steel, aluminum alloy, etc.
● Generally used for melting cutting, using nitrogen or compressed air as auxiliary gas
● For fine cutting with high precision and surface requirements
● For cutting materials such as stainless steel and aluminum alloys with nitrogen or compressed air
2. Double nozzle
● Generally used for oxidizing cutting, using oxygen as auxiliary gas.
● The gas flow is converged and compressed twice, cutting carbon steel with remarkable effect.
● Used for cutting carbon steel and stainless steel with oxygen
After passing through the inner core, the gas of the double-layer nozzle will undergo a second expansion to increase the gas velocity, and then pass through the end hole to reach the working surface. The advantage of this is that it can reduce the generation of shock waves and increase the gas velocity, thus improving the efficiency of the gas involved in cutting, taking away slag and heat.
Nozzle size selection
The nozzle hole diameters include φ1.0mm, φ1.5mm, φ2.0mm, φ2.5mm, φ3.0mm, etc. At present, the nozzle aperture usually adopts two types: φ1.5mm and φ2mm. The difference is:
1. Thin sheets below 3mm: If you use φ1.5mm, the cutting surface will be very thin; if you use φ2mm, the cutting surface will be thicker and the corners will be easily stained.
2. Thick plates above 3mm: Due to the high cutting power and long relative cooling time, the relative cutting time also increases. When φ1.5mm, the gas diffusion area is small and unstable during use, but it is basically usable. When φ2mm, the gas diffusion area is large and the gas flow rate is slow, so the cutting is more stable.
3. The hole diameter is φ2.5mm, which can only be used for cutting thick plates above 10mm. In summary, the size of the nozzle aperture has a serious impact on the cutting quality. Currently, laser cutting mostly uses nozzles with φ1.5mm and φ2mm apertures.
Therefore, the larger the aperture of the nozzle, the worse the relative protection of the focusing lens, because the sparks of the molten material will splash when cutting, and the probability of bouncing upward is higher, making the life of the laser cutting machine lens shorter.
The concentricity between the nozzle center and the laser is one of the important factors that determine the cutting quality, especially the thicker the workpiece being cut, the greater its impact. Therefore, the concentricity of the nozzle center with the laser must be adjusted to obtain a better cutting surface finish.
Note: When the nozzle is deformed or there are stains on the nozzle, its impact on the cutting quality is the same as above. Therefore, the nozzle should be placed carefully to avoid collision and avoid deformation. Melted stains on the nozzle should be cleaned in time. The quality of the nozzle requires high precision in manufacturing, and installation also requires correct methods. If the cutting conditions change due to poor nozzle quality, the nozzle should be replaced in time.
