Complete comparison of assist gas types for fiber laser cutting — cost per meter, edge quality, pressure settings, and material-specific recommendations.
If you own a fiber laser cutting machine, the gas you use matters more than most people think. Pick wrong and you're burning through cash on every meter you cut. Pick right and you save thousands a year while getting better edges.
I've been working with laser cutting setups for years now, and the one thing I still see shops get wrong is assist gas selection. They either default to whatever their supplier pushes, or they stick with one gas for everything. Neither approach works well. Here's what I've learned.
Before we get into numbers, here's a quick rundown of how each gas behaves during cutting.
Oxygen feeds an exothermic reaction. The laser heats the metal, the oxygen ignites it, and the extra heat lets you cut thicker material with less power. You get a faster cut on carbon steel but the edge oxidizes — turns dark, sometimes rough. The oxide layer can be an issue if you're welding after cutting.
Nitrogen is inert. It displaces oxygen from the cut zone, so the edge stays clean and bright — no oxidation at all. That's why stainless steel and aluminum almost always use nitrogen. The downside: nitrogen costs more per cubic meter than oxygen or compressed air.
Compressed air is mostly nitrogen — about 78% — mixed with 21% oxygen. Plus some water vapor and oil if you're not filtering it. It's the cheapest option by far. Edge quality lands somewhere between oxygen and nitrogen. Slightly oxidized, not perfectly bright. Good enough though for plenty of jobs where the edge won't be seen.
Here's where the math gets interesting. I put together these estimates based on typical industrial gas pricing and consumption rates for a 6kW fiber laser cutting 3mm stainless steel:
| Gas Type | Pressure (bar) | Flow Rate (m³/h) | Cost per m³ | Cost per Hour | Cost per Meter* |
|---|---|---|---|---|---|
| Nitrogen (cylinder) | 12–18 | 15–25 | ~$0.30 | $4.50–$7.50 | $0.038 |
| Nitrogen (bulk liquid) | 12–18 | 15–25 | ~$0.05 | $0.75–$1.25 | $0.006 |
| Oxygen (cylinder) | 3–6 | 5–10 | ~$0.12 | $0.60–$1.20 | $0.005 |
| Compressed air (on-site) | 6–10 | 10–18 | ~$0.01 | $0.10–$0.18 | $0.001 |
* Based on 3mm stainless steel at 6kW, ~200 m/min cutting speed. Prices vary by region and supplier. Cylinder N₂ pricing from industrial gas distributors; bulk liquid N₂ pricing from Praxair/Linde published rate sheets. Compressed air cost is electricity only.
This one trips people up. Buying nitrogen in cylinders costs about 6 times more than bulk liquid. Six times. Shops that switch to a bulk tank usually get their money back in under 18 months.
Compressed air is almost free by comparison — about $0.10–$0.18 per hour in electricity. But you have to factor in the compressor cost and the air dryer. A good screw compressor with a refrigerated dryer runs $5,000–$12,000 depending on capacity.
This table tells you which gas to reach for, depending on what you're cutting:
| Material | Thickness | Recommended Gas | Edge Quality | Alternative |
|---|---|---|---|---|
| Carbon steel | 1–6mm | Oxygen | Good, oxidized edge | Compressed air (thin) |
| Carbon steel | 6–25mm | Oxygen | Fair, heavy oxide | — |
| Stainless steel | 1–3mm | Nitrogen | Excellent, bright edge | Compressed air (non-critical) |
| Stainless steel | 3–8mm | Nitrogen | Good, slight striation | — |
| Aluminum | 1–6mm | Nitrogen | Good, bright | Compressed air (thin) |
| Copper / Brass | 1–3mm | Nitrogen | Good | — |
One thing that catches people: compressed air works surprisingly well for thin stainless steel (under 2mm) and thin carbon steel (under 3mm). The edge won't be as clean as nitrogen, but if the part is getting welded or painted anyway, who cares? That's where most of the savings live.
Your gas supply method matters almost as much as the gas itself. Here's how the options stack up:
Best for low-volume shops or shops cutting less than 20 hours a week. Cylinder nitrogen typically runs $0.25–$0.35 per m³. You pay for convenience. Downside: you're swapping cylinders constantly at higher volumes, and the per-unit cost is brutal.
Best for shops running 40+ hours a week. Liquid nitrogen delivered in a bulk tank drops the cost to about $0.04–$0.06 per m³. That's an 80% reduction from cylinder pricing. You need space for the tank (typically 1,000–3,000 liters), and the supplier installs it free if you commit to a contract.
These use PSA (pressure swing adsorption) to pull nitrogen from the air. Capital cost is $15,000–$40,000 for a system that can handle a 6kW machine. If you're running 60+ hours a week, a generator can bring your cost below $0.02 per m³. Payback is usually 2–3 years vs. cylinder supply.
Compressed air is the cheapest option by far. A 15kW screw compressor with dryer will handle most single-machine setups. The ongoing cost is just electricity — about $0.05–$0.15 per operating hour in power. But you must filter the air properly. Without a good coalescing filter and dryer, moisture and oil residue will damage your laser cutting head lenses.
Let me be direct about this. Nitrogen gives you the best edge, period. The cut face comes out bright, smooth, and oxide-free. That matters for parts that go straight to a customer without secondary processing.
Oxygen cuts faster on thick carbon steel but leaves a darker edge with more roughness. The oxide layer can cause problems if the part needs to be welded or powder-coated afterward.
Compressed air lives in the middle. Decent edge on thin materials, but the slight oxidation means you won't get the same bright finish as nitrogen. For non-cosmetic parts — brackets, structural supports, hidden components — it's more than acceptable.
One thing I'll add: edge striation is more about your cutting parameters than your gas choice. I've seen beautiful cuts on compressed air with the right focus position and nozzle standoff, and I've seen ugly cuts on nitrogen from a worn nozzle. Don't blame the gas for a setup problem.
Setting the correct pressure is just as important as picking the right gas. Here's a practical starting point for a 6kW fiber laser:
| Material | Gas | Pressure (bar) | Nozzle Ø (mm) | Standoff (mm) |
|---|---|---|---|---|
| Carbon steel 3mm | O₂ | 3–5 | 1.5–2.0 | 0.8–1.2 |
| Carbon steel 10mm | O₂ | 5–8 | 2.0–3.0 | 1.0–1.5 |
| Stainless steel 2mm | N₂ | 10–14 | 1.5–2.0 | 0.5–1.0 |
| Stainless steel 6mm | N₂ | 14–18 | 2.0–3.0 | 0.5–1.0 |
| Aluminum 3mm | N₂ | 10–14 | 1.5–2.0 | 0.8–1.2 |
These are starting points, test them. Every machine behaves a bit differently. Nozzle condition, beam quality, focal spot — they all shift the sweet spot. I always tell operators: run a test grid when you switch materials. Takes 10 minutes, saves hours of bad cuts.
Yes, up to about 3mm with acceptable edge quality. The edge won't be as bright as nitrogen, but for non-cosmetic parts it works fine. Above 3mm you start seeing more dross on the bottom edge.
On carbon steel, yes — about 15–25% faster at equivalent power. Oxygen adds exothermic energy. On stainless steel, oxygen doesn't help much and actually makes the edge worse. Stick with nitrogen for stainless.
Oxygen: 3–8 bar depending on thickness. Nitrogen: 10–18 bar for thin materials, higher for thick. Compressed air: 6–10 bar. The thicker the material, the higher the pressure you'll need to clear molten material from the kerf.
Yes, as long as the air is filtered and dry. Moisture in the air stream can crack the focus lens. Oil residue deposits on the protective lens and reduces cutting quality. Use a refrigerated or desiccant dryer with a 0.01 micron coalescing filter.
Cylinder supply: $0.25–$0.35 per m³ ($4.50–$7.50/hour). Bulk liquid: $0.04–$0.06 per m³ ($0.75–$1.25/hour). On-site generator: as low as $0.01–$0.02 per m³. Your volume determines which option makes economic sense.
Some shops mix nitrogen and oxygen for a balance of speed and edge quality. Gas mixing systems are available but add cost. For most applications, sticking with one gas per material type is simpler and more predictable.
Here's the short version:
If you're buying a new fiber laser cutting machine or want to optimize your current setup, our team can help with gas system sizing and integration. Get in touch with us for a free consultation. We'll walk through your material mix, cutting volume, and current gas costs to find the setup that saves you the most money.