The primary consideration is the nozzle's inner diameter (Aperture), followed by nozzle type and quality.
1. Selecting a Nozzle Aperture Based on Material Thickness
The nozzle aperture directly determines the gas flow rate, airflow pattern, and pressure range.
| Nozzle Diameter | Applicable Material Thickness | Features and Applications |
| Φ1.0mm - Φ1.2mm | Thin Plate (<3mm) | Concentrated airflow and high speed make it suitable for high-speed cutting of thin plates with narrow kerfs. However, it consumes a lot of gas and requires high gas pressure stability. |
| Φ1.5mm - Φ1.8mm | Medium Plate (3mm - 8mm) | A versatile choice. This balances airflow speed and flow rate, offering the widest applicability and serving as the standard for most fabricators. |
| Φ2.0mm - Φ2.5mm | Thick Plate (8mm and above) | High airflow and high pressure make it more effective in removing large amounts of molten metal generated by thick plate cutting and preventing dross buildup. However, the airflow is relatively dispersed. |
| Φ3.0mm+ | Extremely Thick Plate/Special Applications | Extremely high flow rate. Suitable for oxide cutting of carbon steel or nitrogen cutting of very thick stainless steel, which requires extremely high gas pressure. |
II. Selecting a Nozzle Type Based on the Cutting Process and Gas
1. Standard Single-Layer Nozzle
Structure: Most common, with a single layer.
Applicable Gas: Oxygen (O₂).
Applicable Process: Oxidation cutting of carbon steel.
Features: Low cost. Oxygen cutting inherently generates a lot of heat, requiring relatively low airflow protection.
2. Dual-layer Nozzle (Zoom Nozzle)
Structure: Two inner and outer layers create a "Venturi effect."
Applicable Gases: Nitrogen (N₂), Air.
Applicable Processes: Bright surface cutting of stainless steel and aluminum alloys, and non-metallic cutting.
Features:
The airflow is more concentrated and stable, tightly enveloping the laser beam like a "sleeve," effectively preventing air from entering and ensuring optimal protection of the cutting area.
It generates higher gas pressure and enhances slag removal.
It is the preferred choice for high-quality nitrogen cutting. Although slightly more expensive, it delivers far superior performance compared to a single-layer nozzle.
III. Other Key Selection Factors
1. Nozzle Height (Stand-off Distance)
This refers to the distance from the bottom of the nozzle to the surface of the plate.
It is generally set between 0.5mm and 1.5mm. The height can be increased appropriately for thicker materials. Too high a height will cause airflow dispersion, reducing protection and slag removal capabilities; too low a height can create a collision risk.
2. Nozzle Concentricity
This is the most important quality indicator! It refers to whether the nozzle bore and the laser beam are absolutely coaxial.
Inspection Method: Install the nozzle, place a transparent plastic sheet at the nozzle opening, and shine a red light (indicator light) to observe whether the red dot is centered in the bore.
Consequences of poor concentricity: This can lead to an asymmetrical cutting surface, slag buildup on one side, or even laser reflection and damage to the cutting head.
3. Material and Manufacturing Process
Red Copper: The most commonly used material, with good thermal conductivity and resistance to slag splashing.
Brass: Lower cost, but slightly less durable and less thermally conductive.
Ceramic Nozzles: Used in applications prone to collision (such as cutting mesh plate). Ceramic will shatter in the event of a collision, thus protecting the more expensive cutting head.
IV. Selection Process Summary and Practical Recommendations
1. Clarify Requirements: What material do I want to cut? What is the thickness of the stainless steel/carbon steel/aluminum? What gas should be used for thin/thick plates? (N₂/O₂)
2. Select the aperture:
Stainless steel/aluminum (N₂ cutting): Choose Φ1.5mm for medium-thick plates and Φ2.0mm or larger for thick plates.
Carbon steel (O₂ cutting): Choose Φ1.0mm - Φ1.2mm for thin plates and Φ1.5mm for medium-thick plates.
3. Select the type:
Nitrogen cutting/high-quality cutting: A double-layer nozzle is preferred.
Oxygen cutting of carbon steel: A standard single-layer nozzle is sufficient.
4. Test and check concentricity on the machine: This is an essential step. After installing a new nozzle, its concentricity with the laser beam must be checked.
5. Set parameters: Based on the nozzle aperture and material, find the recommended gas pressure and set the appropriate nozzle height in the machine's cutting parameter table.
Finally, consider the nozzle a consumable item. If you notice any wear, deformation, or slag damage on the nozzle tip, replace it immediately; otherwise, the cutting quality will be severely affected. Having several high-quality nozzles of varying apertures on hand is a key investment to ensure production efficiency and product quality.