The Role of Nitrogen and Oxygen in Laser Cutting Processes
Interest in laser cutting and its applications continues to grow steadily. However, it is essential to remember that the efficient operation of a laser cutting machine requires an assist gas—typically nitrogen, oxygen, or compressed air. The choice and quality of this gas significantly influence the final result.
The laser cutting process begins with selecting appropriate equipment. One must first consider the type and thickness of the metal to be processed. Once the right machine has been chosen, a common question arises: how to supply the necessary assist gas?
Let’s explore the various assist gas options and the role they play in laser cutting.
Gas Purity Matters
When we speak of gas quality, we typically refer to the purity — i. e., the percentage of the primary molecule in the gas. For nitrogen and oxygen, standard purity levels start at around 93 % and above.Laser Cutting with Nitrogen
Nitrogen plays a critical role in laser cutting. It enables high cutting speeds and excellent edge quality. Other vital factors in the process include laser power, focus spot diameter, and beam quality.
Nitrogen acts as an inert assist gas, helping to blow molten metal out of the cut zone while also preventing oxidation. For this reason, high-purity nitrogen is essential, as even minimal oxygen content can negatively affect the final product. A discoloured cut edge is often an indicator of insufficient nitrogen purity. The purer the nitrogen, the cleaner the cut and the fewer defects on the workpiece surface.
For instance, aluminium is typically cut with nitrogen. Cutting it with oxygen often results in rough edges and burrs. Nitrogen is also preferable when cutting low-alloy steels, as it enhances paint adhesion in post-processing.
The ideal nitrogen purity for laser cutting is approximately 99.99 %. The higher the purity, the better the results.
High-pressure nitrogen, typically in the range of 15 to 40 bar, is used to achieve superior cutting quality. On some Trumpf laser systems, nitrogen is used at 30–35 bar.
Gas delivery methods vary depending on the application and material. Nitrogen can be introduced directly through a nozzle or via a flow distribution system to ensure uniform coverage over the cutting area.
One of the best solutions for on-site nitrogen generation is the Nitrotec series of PSA nitrogen generators. When high-pressure nitrogen is required, a booster compressor is used, offering compression up to 40 bar.
The key advantage of using nitrogen is that it eliminates oxidative and exothermic reactions, which generate excessive heat. Although cutting speed may be lower and the process requires higher gas pressure, these are offset by the improved quality of the finished product.
It’s important to note that nitrogen-assisted laser cutting does not vaporise the metal — it melts it. This enables precision cutting with minimal structural distortion of the material.
In summary, nitrogen provides a more stable and controlled cutting process, free from unwanted chemical reactions and thermal damage. Therefore, when selecting equipment to supply assist gas for a laser cutting machine, both gas purity and delivery method must be taken into account.
Example Parameters for Nitrogen-Assisted Laser Cutting
| Sheet Thickness (mm) | Laser Power (W) | Focal Length (inches) | Nozzle Diameter (mm) | Nitrogen Pressure (bar) | Cutting Speed (m/min) |
|---|---|---|---|---|---|
| 2 | 1400–1500 | 5.00 | 1.40 | 8–10 | 2.00–4.00 |
| 4 | 1400–1500 | 7.50 | 1.70 | 12–15 | 1.00–1.20 |
| 2 | 3000 | 7.50 | 2.50 | 17–19 | 0.30–0.40 |
Laser Cutting with Oxygen
In contrast to nitrogen, oxygen is a chemically reactive gas. Laser cutting with oxygen results in the formation of around 97 % FeO and 3 % Fe₂O₃ and generates substantial heat. This enables cutting of thicker materials at increased speeds.
Example Parameters for Oxygen-Assisted Laser Cutting
| Sheet Thickness (mm) | Laser Power (W) | Focal Length (inches) | Nozzle Diameter (mm) | Oxygen Pressure (bar) | Cutting Speed (m/min) |
|---|---|---|---|---|---|
| 2 | 800–1000 | 2.50 | 0.50–1.20 | 2.50–5.00 | 7 |
| 8 | 1200–1500 | 5.00 | 1.10–1.60 | 0.50–1.00 | 5 |
| 20 | 2200–2600 | 7.50 | 2.10–2.50 | 0.40–0.60 | 0.7 |
When cutting thicker metals, oxygen pressure can be reduced. However, a lower purity level—due to impurities—can significantly decrease cutting efficiency and result quality.
PSA Gas Generators: A Modern Solution
PSA nitrogen and oxygen generators eliminate the need for bottled or liquid gases. These systems operate fully automatically and require no constant operator presence. All process parameters are monitored and displayed via an operator panel.
Demand for PSA nitrogen generators with integrated booster compressors has surged recently — driven by increased adoption of modern foreign laser machines and growing awareness of on-site nitrogen generation technologies. Cylinder gases are still commonly used for smaller-scale needs (5–30 Nm³/day).
Over the past years, our company has manufactured and supplied numerous nitrogen generator systems, ensuring uninterrupted operation of laser cutting machines across Russian manufacturing facilities. These systems offer flow capacities ranging from 3 to 400 Nm³/h with nitrogen purity levels up to 99.9995 %.
