Correct Selection and Use of Laser Air Assist Nozzles

During the laser cutting process, the laser air assist nozzle collects the capacitance signal and transmits it to the signal processor through the ceramic ring, thereby maintaining the laser head tracking the distance of the workpiece during the cutting process, guiding the gas to pass through the workpiece smoothly, and forming high pressure near the nozzle outlet to speed up the cutting speed, take away the slag, and protect the internal lens of the laser head.
The coaxiality between the laser air assist nozzle outlet hole and the laser beam is one of the important factors affecting the quality of cutting, especially when the workpiece is thicker, its influence is greater. Therefore, the concentricity of the nozzle center and the laser must be adjusted to obtain a better cutting section.

The Impact on Cutting Quality when the Nozzle Center is not Coaxial with the Laser Beam Center

1. The cutting gas is ejected from the center of the laser air assist nozzle and acts on the cutting plate. According to the positive and negative directions of the X-axis and the Y-axis, the laser spot can be divided into four areas. When the laser is not in the center of the nozzle, the four sections are prone to inconsistent effects. For example, when cutting a thick carbon steel plate with a small nozzle, some surfaces have bright surfaces, some surfaces have rough stripes, and even slag or can't be cut.
2. The bright surface effect of 10,000 watts of carbon steel cutting is currently achieved by using a small nozzle combined with a high focus process. The laser is not in the center of the nozzle, which can easily cause the nozzle to heat up slightly, affecting the follow-up, and cannot be processed stably. In severe cases, the nozzle will be directly burned.

Nozzle Type

Generally, laser air assist nozzles are divided into single and double layers. Single-layer nozzles are used for melting cutting, that is, nitrogen is used as an auxiliary gas, usually used for cutting stainless steel, aluminum alloy, brass, etc.; double-layer nozzles are generally used for oxidation cutting, that is, oxygen is used as an auxiliary gas, usually used for cutting carbon steel.

Nozzle Size Selection

The diameter of the nozzle determines the shape of the airflow entering the incision, the gas diffusion area, and the gas flow rate, which affects the removal of the melt and the stability of the cutting. The larger the gas flow entering the incision, the faster the speed, and the proper position of the workpiece in the airflow, the stronger the ability to spray and remove the melt.
Users choose the laser air assist nozzle size according to the power of the laser used and the thickness of the metal sheet to be cut. In theory, the thicker the sheet, the larger the nozzle should be used, the greater the pressure set by the proportional valve, the greater the flow rate, and the pressure is ensured to cut a normal cross-section effect.

Selection of nozzles with different powers

• Laser power ≤ 6000W

For cutting carbon steel, the nozzle specification diameter is generally double-layer S1.0~5.0E; for cutting stainless steel, select a single-layer nozzle with ordinary specifications;

• Laser power ≥ 6000W

For cutting carbon steel, 10~25mm carbon steel bright surface cutting, the cutting nozzle specification diameter is generally double-layer high-speed E-type S1.2~1.8E; the single-layer fan-shaped diameter is generally selected from D1.2~1.8; for cutting stainless steel, select a single-layer nozzle with ordinary specifications;

Summary

Correctly selecting and using llaser air assist nozzles is the key to achieving efficient and high-quality cutting. By considering the type and size of the nozzle, and matching it with the type and pressure of gas used, cutting efficiency and finished product quality can be significantly improved.

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