The assist gas used during fibre laser cutting affects the cutting process, the finished edge and the cost of production. Choosing between nitrogen, oxygen and compressed air therefore starts with the component you need to deliver, rather than the price of the gas alone.
Material, thickness, laser configuration and the next manufacturing operation all influence the decision. The gas and cutting parameters must be approved for the machine and application; one workshop’s successful setup should not be assumed to suit another.
What the assist gas does
The laser heats the material and the assist gas helps clear it from the cut. Different gases also change what happens at the edge. Nitrogen supports a fusion-cutting process without providing the oxidation energy associated with oxygen cutting.
The practical result is a balance between cut quality, process capability and resource use. Ask for sample parts in the actual material and thickness you process, using the proposed gas arrangement.
Inspect more than the top surface. Check the full edge, underside, small features and consistency across the sample. Then assess whether the component meets the requirements of your next operation.
When nitrogen is useful
Nitrogen is commonly selected where an oxide-free cut edge is required, particularly for suitable stainless steel and aluminium applications. The laser supplies the cutting energy, while the gas clears molten material and shields the edge.
An oxide-free edge does not guarantee that every part needs no further finishing. Burrs, surface condition and customer specifications still matter. Confirm acceptance using representative samples and your own downstream process.
Review the required purity, pressure and flow with the machine supplier. Gas demand can change considerably between jobs, so a supply system should be sized for the intended workload rather than a convenient average.
When oxygen is useful
Oxygen supports an oxidation reaction that contributes energy to the cutting process. It is often used for suitable mild-steel work, subject to the machine’s cutting specification and the required edge quality.
The resulting edge can carry an oxide layer. Where coating, welding or another process has specific surface requirements, establish whether cleaning or additional preparation is needed. That labour belongs in the cost comparison.
A gas choice that makes an individual cutting operation economical may create extra work later. Evaluate the route from raw sheet to accepted component, including any finishing required by your customer.
When compressed air is an option
Compressed air can be a useful cutting option on machines and applications designed for it. Because air contains oxygen, it should not be expected to produce the same edge condition as a nitrogen process.
The supply must meet the machine manufacturer’s requirements for cleanliness, dryness, pressure and delivered flow. An existing workshop compressor is not automatically suitable, especially when other equipment draws air at the same time.
Air also has a production cost. Include compressor electricity, treatment equipment, maintenance and any additional finishing. Compare actual accepted parts rather than describing compressed air as free cutting gas.
Compare the complete gas supply
For nitrogen or oxygen, consider delivery arrangements, storage, regulation and the capacity available at the machine. Peak flow and sustained production demand both matter. Interruptions caused by inadequate supply can outweigh a small difference in unit price.
For nitrogen generation, review the required purity and delivery conditions alongside compressor, treatment, storage and electrical requirements. Generation can be attractive for an appropriate workload, but the installed system and operating costs must be assessed together.
Explore Selmach’s nitrogen generators when reviewing supply options. Ask for a proposal based on your anticipated material mix and cutting hours.
Compare cost per accepted part
Run a controlled comparison using the same representative component. Record cutting time, measured gas use, electricity where available, consumable use and required finishing. Count the parts that meet the agreed quality standard.
If one process cuts faster but creates more rejected parts or extra cleaning, its apparent saving may disappear. Equally, a more expensive gas may be justified where it helps deliver the required finish without an additional operation.
Keep the nozzle and other process consumables appropriate to the approved setup. Our plasma and laser consumables selection guide provides a useful starting point for discussing these requirements.
Choose around your actual work
Send Selmach your material grades, thicknesses and finished-edge requirements. We can discuss the fibre laser range and suitable gas supply arrangements, then help you assess samples against the complete production process.
Published 6th October 2026