Technical reference

Fiber Laser Cutting Parameters Chart (Starting Points)

Updated 2026-10-12 · 5 min read

Every fiber laser ships with a parameter library, and every parameter library is a starting point. The numbers below are the ranges our machines are set up with before tuning, and the logic behind them, so you can get to a usable cut quickly and then refine it on your own material.

Quick answer: For carbon steel use oxygen assist and focus slightly below the surface; for stainless and aluminium use nitrogen at high pressure and focus near the surface. Set power from thickness, then tune speed until the bottom edge is dross-free, then adjust focus in 0.5 mm steps. The tables below are starting points — always confirm on your own material and machine.

The six parameters that decide the cut

Parameter	What it controls	Typical starting range
Laser power	Energy delivered per second	Set by thickness; 60–100% of rated power
Cutting speed	Energy per unit length	Material and thickness dependent
Focus position	Kerf width and energy density	−0.5 to −3 mm for thick, near 0 for thin
Assist gas type	Chemistry of the cut	O₂ for carbon steel, N₂ for stainless and aluminium
Gas pressure	Kerf clearing and cooling	0.3–1.5 bar O₂; 8–18 bar N₂
Nozzle diameter and stand-off	Gas flow quality	1.2–2.5 mm single or double; 0.5–1.5 mm stand-off

Changing one parameter usually requires adjusting another. If you increase speed, you may need more power or a focus tweak to keep the same edge quality.

Carbon steel with oxygen

Oxygen assist makes carbon steel cutting fast because the oxidation reaction supplies additional heat. It also leaves an oxidised edge, which is fine for painted or welded parts and not suitable where the edge must be clean.

Thickness	Power	Speed (starting)	Focus	O₂ pressure
1 mm	1 kW	8–10 m/min	−0.5 mm	0.8–1.2 bar
2 mm	1.5 kW	4–6 m/min	−1.0 mm	0.7–1.0 bar
3 mm	2–3 kW	3–4 m/min	−1.5 mm	0.6–0.9 bar
6 mm	3 kW	1.5–2.0 m/min	−2.0 mm	0.5–0.8 bar
10 mm	6 kW	1.5–2.0 m/min	−2.5 mm	0.4–0.7 bar
12 mm	6 kW	1.2–1.6 m/min	−3.0 mm	0.4–0.6 bar
20 mm	12 kW	1.2–1.6 m/min	−4.0 mm	0.3–0.5 bar

Note the trend: as thickness increases, focus goes further negative and gas pressure comes down. Lower pressure on thick material prevents the oxygen from over-burning the kerf and rounding the top edge.

Stainless steel with nitrogen

Stainless is cut with nitrogen at high pressure. There is no exothermic help, so the laser supplies all the energy — hence the lower speeds and the need for higher power at the same thickness. The reward is a clean, oxide-free edge that can be welded without pickling.

Thickness	Power	Speed (starting)	Focus	N₂ pressure
1 mm	1–1.5 kW	5–7 m/min	−0.3 mm	8–10 bar
2 mm	2 kW	2.5–3.5 m/min	−0.8 mm	10–12 bar
3 mm	3 kW	2.0–2.5 m/min	−1.2 mm	12–14 bar
5 mm	3–4 kW	1.3–1.8 m/min	−2.0 mm	14–16 bar
8 mm	6 kW	1.5–2.0 m/min	−3.0 mm	16–18 bar
12 mm	6–8 kW	0.8–1.2 m/min	−4.0 mm	18–20 bar

Nitrogen purity matters as much as pressure. Cutting-grade nitrogen at 99.999% gives a bright edge; lower purity leaves a slightly oxidised cut. Where the edge will be machined or painted, lower purity is a legitimate cost saving.

Aluminium with nitrogen

Aluminium reflects the beam and conducts heat away quickly, so it cuts slower than stainless at the same thickness and needs tighter gas control.

Thickness	Power	Speed (starting)	Focus	N₂ pressure
1 mm	1.5 kW	5–6 m/min	−0.3 mm	10–12 bar
2 mm	2 kW	2.5–3.5 m/min	−0.8 mm	12–14 bar
3 mm	3 kW	1.8–2.5 m/min	−1.2 mm	14–16 bar
5 mm	4–6 kW	1.2–1.8 m/min	−2.0 mm	16–18 bar
8 mm	6 kW	0.8–1.2 m/min	−3.0 mm	18–20 bar

Aluminium also benefits from a slightly larger nozzle and a higher stand-off than steel, because the kerf ejects more material.

Brass and copper

Both are highly reflective at 1.07 µm, which is why CO2 lasers cannot cut them and fiber lasers can — but they still need care.

Brass cuts well with nitrogen at high pressure; expect speeds similar to stainless, and use a larger nozzle.
Copper needs substantially more power than steel at the same thickness because so much heat is conducted away. A 3 kW machine will cut thin copper; thicker copper needs 6 kW or more.
On both, protect the optics. Ensure the cutting head has a protective window and check it regularly, because back-reflection is a real risk with these materials.

Defect troubleshooting table

This is the table that saves the most time. Find the symptom, check the likely cause in order.

Symptom	Likely cause	What to change
Dross on the bottom edge	Too much heat for the speed	Increase speed or reduce power
Dross, heavy and bubbly (carbon steel, O₂)	Oxygen pressure too high	Reduce O₂ pressure in 0.1 bar steps
Dross, hard and adherent (stainless, N₂)	Focus too low, or gas pressure low	Raise focus 0.5 mm; raise N₂ pressure
Top edge rounded and burnt	Focus too high, or too much oxygen	Lower focus; reduce O₂ pressure
Kerf too wide	Focus too high, or nozzle too large	Lower focus; fit a smaller nozzle
Cut not through, sparks spraying upward	Speed too high, or focus too low	Reduce speed 10%; raise focus
Rough, striated cut face	Speed too high for the power	Reduce speed until striations disappear
Inconsistent cut, random misses	Nozzle damaged or contaminated	Replace nozzle; check for spatter
Burn marks and heavy oxidation on stainless	Gas purity low, or nitrogen flow insufficient	Check N₂ purity; increase pressure
Piercing takes too long or spatters	Pierce parameters not matched to thickness	Use a longer pierce time at lower power, or a two-stage pierce

Setting up a new material, step by step

Start from the closest library entry. Every machine ships with parameters for common materials. Find the nearest thickness and material and start there.
Get through the material first. Adjust power or speed until the beam cuts through cleanly across the whole part. Do not worry about edge quality yet.
Tune speed for the bottom edge. Increase speed in 5–10% steps until dross starts to appear, then back off slightly. That is your maximum clean speed.
Tune focus. Move focus in 0.5 mm steps and watch the kerf width and the top edge. The sweet spot gives the narrowest kerf with a square top edge.
Check gas pressure last. If the bottom edge has dross at the correct speed and focus, adjust pressure in 0.1 bar steps.
Record it. Write the final parameters on the job sheet or in the machine library. The next person to run this material should not have to repeat the exercise.

Safety and housekeeping

Parameters aside, three habits prevent most problems:

Check the nozzle and protective lens daily. A damaged nozzle changes the gas flow and quietly ruins every parameter you set.
Keep the chiller within range. Power derating above the set water temperature shows up as "the parameters stopped working".
Extraction on, always. Cutting fumes and metal oxide particles are a health issue and also contaminate the optics.

Frequently asked questions

What are the main laser cutting parameters?

Laser power, cutting speed, focus position, assist gas type and pressure, nozzle diameter and stand-off distance. Power and speed set the energy density; focus and gas decide whether that energy removes material cleanly.

Should I use oxygen or nitrogen for laser cutting?

Oxygen for carbon steel - the exothermic reaction adds heat and raises speed. Nitrogen for stainless steel and aluminium, where an inert atmosphere prevents oxidation and gives a clean, weldable edge.

What causes dross on the bottom of a laser cut?

Usually too much heat for the speed, or focus set too low. On carbon steel with oxygen it often means the oxygen pressure is too high. Slowing down or raising the focus usually clears it.

How do I set the focus for a new material?

Start from a focal position slightly below the surface (negative focus) for thick material and near zero for thin, then adjust in 0.5 mm steps while watching the kerf and the bottom edge. Auto-focus heads make this a parameter lookup rather than a manual adjustment.

Machines mentioned in this article

Fiber Laser Cutting Machine — PL-1390 with Raycus source and Raytools head
Fiber Laser Marking Machine — For marking rather than cutting
Thickness and Speed Chart — Maximum thickness by power

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