In short: On nitrogen-cut stainless, research points first to focal position, then to speed; gas pressure often matters less than shops assume.
Check the nozzle and optics before you change settings, then move one setting at a time on an offcut. Results depend on material and thickness, so treat any fixed rule as a starting point.
What measured studies show
Most online fault tables come from machine sellers and disagree with each other, especially on focus. Measured studies are a better guide, though each covers one setup:
| Study | Setup | Finding |
|---|---|---|
| Mahrle et al., 2021 (source 1) | 10 mm AISI 304, 4 kW fiber laser, nitrogen | Focal position was the dominant factor for kerf width, roughness and maximum speed. Gas pressure, nozzle diameter and stand-off had only secondary effects |
| Mahrle et al., 2021 (source 1) | Same, with circular beam oscillation | Oscillation nearly eliminated underside dross in the best test, at slightly lower maximum speed |
| Duspara et al., 2022 (source 2) | 3 mm austenitic steel, fiber laser, nitrogen | Burr height depended on the cutting parameters, and fell as nozzle height and focus value were reduced |
| Duspara et al., 2022 (source 2) | Same | Higher nitrogen pressure lets settings stray further from optimum and still cut burr-free; pressure was still cut by 22.9 % after optimization |
| Scientific Reports study, 2025 (source 3) | 4 mm AISI 304, 2 kW fiber laser, 14 bar | Roughness Ra fell with higher speed: 5.4 µm at 1.5 m/min, about 4.0 µm at 3.5 m/min at the settings tested |
Results apply to the materials and machines tested.
Two practical points follow. Raising gas pressure may hide a focus problem while using far more nitrogen, so do not treat it as the first fix. And too slow can be as harmful as too fast: in source 3, the slowest speed gave the roughest edge.
Check in this order
- Consumables and optics: nozzle damage and centring, and a clean protective window. These are quick to check and change the result of every other test.
- Material: rust, scale or oil can look like a parameter fault. Try a clean sheet.
- Gas: the right gas, purity and pressure at the nozzle, and no leaks. Published purity advice is in our nitrogen guide.
- Focus: the first setting to test on stainless with nitrogen, given source 1. Move it in small steps.
- Speed: try both directions.
- Nozzle height: source 2 links it to burr height.
- Pressure and power: change these last.
Change one setting at a time, cut a test piece, and write down what changed. Interactions are real, so a change that helps at one thickness may not help at another.
Symptom guide
| What you see | Start with | Why |
|---|---|---|
| Dross on the lower edge (nitrogen) | Focal position, then speed | Poor melt blow-out causes lower-edge dross (source 1) |
| Burr on thin stainless | Focus and nozzle height | Both affected burr height (source 2) |
| Rough striated edge | Speed and focus | Roughness changed with both (sources 1, 3) |
| Melt build-up at the top edge | Focus position | Seen at lower focal positions (source 1) |
| Colour change on stainless | Gas purity and leaks | Purity prevents colour change (source 2) |
| One-sided fault | Nozzle centring and beam alignment | A direction-dependent fault points to the machine, not the recipe |
| Fault only at the end of the sheet | Heat build-up | Change the cut sequence, and check the skeleton |
Summary by Halcyon Laser. Starting points, not machine settings.
Oxygen cutting of carbon steel works differently, because the gas reacts with the metal and adds heat. The studies above used nitrogen, so do not carry their conclusions over. For oxygen work, follow your machine maker's parameter tables, keep the plate clean, and test small changes. See nitrogen vs oxygen laser cutting.
Judge the edge by a standard
ISO 9013:2017 grades thermal cut edges into tolerance classes and quality ranges (source 4). Agree the range with your customer, so that you are not chasing a finish no one asked for. Thick material shows more striation in any case.
Prevent it
- Keep a daily routine: nozzle, centring, protective window and focus check.
- Save proven parameters by material, thickness, gas and nozzle.
- Log every change and the result.
- Ask about beam oscillation on thick stainless, given source 1.
If the fault stays after these checks, record the settings and photos, and contact your supplier. Our HL-F fiber lasers include remote diagnostics, and you can report a fault here.
Frequently asked questions
Why does my laser leave dross on the bottom edge?
Dross forms when melt is not blown out cleanly. On nitrogen-cut stainless, research points first to focal position, then speed. Check the nozzle, then change one setting at a time on an offcut.
Will raising gas pressure remove dross?
Sometimes, but it may not be the main factor. One study on 10 mm stainless found pressure had only secondary effects, while focal position dominated. Higher pressure also uses more nitrogen.
How do I reduce burrs on stainless laser cuts?
A study on 3 mm stainless found burr height fell as nozzle height and focus value were reduced. Start there, in small steps, after checking the nozzle.
Does cutting slower give a better edge?
Not always. On 4 mm stainless, roughness was highest at the slowest speed tested and lower at higher speed. Find the best speed for your material.
Why is my stainless steel edge discoloured?
Check gas purity and leaks first. A university study says nitrogen purity of at least 99.99 % prevents colour change on the sheet.
Sources
- A. Mahrle, M. Borkmann, P. Pfohl, “Factorial Analysis of Fiber Laser Fusion Cutting of AISI 304 Stainless Steel”, Materials 14(10):2669, 2021 (Fraunhofer IWS, TU Dresden) — pmc.ncbi.nlm.nih.gov (accessed 2026-11-01)
- M. Duspara, W. Matysiak, I. Vidaković, S. Sedmak, “Optimization of Nitrogen Use Efficiency in Cutting of Austenitic Stainless Steel by a Fiber Laser”, FME Transactions 50 (2022) 745–751 — www.mas.bg.ac.rs (accessed 2026-11-01)
- “Characterization of AISI 304 stainless steel based on laser cutting process optimization”, Scientific Reports, 2025 — www.nature.com (accessed 2026-11-01)
- ISO 9013:2017, Thermal cutting — Classification of thermal cuts (catalogue entry) — www.iso.org (accessed 2026-11-01)
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