The assist gas consumption calculator estimates how much nitrogen, oxygen or compressed air your fiber laser uses, and what it costs. Enter nozzle size, pressure and working hours to get the flow rate, daily and monthly consumption, cylinders per day and monthly gas cost.
Pressure as shown on the machine (gauge pressure).
Arcus CNC fiber lasers can be configured for nitrogen, oxygen or high-pressure air. Ask which gas setup fits your parts, or see our fiber laser cutting machines.
How gas consumption is calculated
At laser cutting pressures the gas leaves the nozzle at the speed of sound (choked flow). The flow then depends only on the nozzle area and the absolute pressure upstream, not on the material being cut:
The mass flow is converted to normal cubic meters (0 °C, 1.013 bar) or standard cubic feet. Because flow scales with the nozzle area, going from a 2.0 mm to a 3.0 mm nozzle raises consumption by about 2.25 times at the same pressure.
| Symbol | Meaning |
|---|---|
| Cd | Flow coefficient of the nozzle (about 0.9) |
| A | Nozzle exit area, π × d² / 4 |
| P₀ | Absolute pressure: gauge pressure + 1.013 bar |
| γ, R | Heat capacity ratio and gas constant (N₂: 1.40, 296.8 J/kg·K; O₂: 1.40, 259.8; air: 1.40, 287.1) |
| T | Gas temperature, taken as 20 °C |
Typical pressures by gas
| Gas | Typical pressure | Used for |
|---|---|---|
| Nitrogen | 10 – 25 bar | Stainless steel, aluminum, thin mild steel with oxide-free edges ready for welding or painting |
| Oxygen | 0.5 – 3 bar | Medium and thick mild steel; low gas use, oxidized edge |
| Compressed air | 8 – 16 bar | Thin and medium sheet where a slightly darker edge is acceptable; lowest running cost |
Choosing a gas supply
- Cylinders and cylinder bundles suit low use, up to roughly 50 Nm³ per day.
- A liquid nitrogen dewar or bulk tank is usually cheaper once you use several hundred Nm³ per day.
- An on-site nitrogen generator or a high-pressure air system can pay back quickly for shops cutting thin sheet on two shifts. Run the numbers above with your local prices.
Frequently asked questions
How much nitrogen does a fiber laser use per hour?
With a 2.0 mm nozzle at 15 bar, about 30 Nm³ per hour of beam-on time. With a 3.0 mm nozzle at 18 bar, about 80 Nm³ per hour. Gas only flows while cutting, so multiply by beam-on hours, not shift length.
Does laser power change gas consumption?
Not directly. Consumption is set by nozzle size and pressure. Higher-power lasers cut faster, so they use less gas per meter of cut even when flow per hour is the same.
Why is oxygen consumption so much lower?
Oxygen cutting runs at 0.5–3 bar instead of 10–25 bar. Since flow is proportional to absolute pressure, oxygen flow is often less than one tenth of nitrogen flow.