Industrial Laser Cutting: Metals, Gas and Process
Fiber cutting of steel, stainless and aluminum, oxygen and nitrogen, pierce, nozzle and standoff, quality, nesting and gas cost.
What an industrial cutter is
An industrial laser cutter is a fiber laser (1 064 nm, 1 to 20 kW and more) mounted on a rigid flat-bed or tube machine with servo drives, a motorized cutting head, a high-pressure gas supply and a CNC that adjusts the process as it goes. The fiber wavelength is absorbed by metals far better than 10.6 µm: steel absorbs roughly 35 % at 1 µm (an indicative value that varies with surface and temperature) and the beam is delivered through a flexible fiber with no mirrors to align.
| Hobby CO2 / diode | Industrial fiber | |
|---|---|---|
| Power | 5 to 150 W | 1 000 to 20 000+ W |
| Material | Wood, acrylic, card, fabric | Steel, stainless, aluminum, copper, brass |
| Thickness | Up to 10 to 20 mm (organics) | Up to 25 mm and more (steel) |
| Assist gas | Air, a few kPa | Oxygen, nitrogen or air, 0.5 to 2 MPa (5 to 20 bar) |
| Cutting head | Fixed lens | Autofocus, height sensor, protective window |
| Safety | Class 1 enclosure | Full enclosure with a viewing filter for 1 064 nm; see Laser Safety, Fire and Fumes |
Assist gas: oxygen, nitrogen, air
| Gas | What it does | Pressure | Edge | Best for |
|---|---|---|---|---|
| Oxygen (O2) | Burns the iron (an exothermic reaction adds heat) and blows out the oxide | 0.05 to 0.2 MPa (0.5 to 2 bar) | Oxide film (dark); may need removing before paint or welding | Mild steel, thicker plate; lower laser power |
| Nitrogen (N2) | Blows the melt out; no reaction | 1 to 2 MPa (10 to 20 bar) | Bright, oxide-free edge | Stainless, aluminum, thin steel for welding or painting |
| Compressed air | A mix: some oxidation, much cheaper | 1 to 1.5 MPa (10 to 15 bar) | Slight oxide | Aluminum, thin steel; low cost |
Worked example: how much nitrogen a cut uses
- A 2 mm nozzle bore has an area of 3.14 mm². At 12 bar gauge (13.01 bar absolute) the flow is choked (it reaches the speed of sound at the throat), so the mass flow is ṁ = Cd A p0 √(γ ÷ R T0) × (2 ÷ (γ+1))(γ+1)/(2(γ−1)).
- With Cd = 0.9, γ = 1.4, R = 296.8 J/(kg·K) and T0 = 293 K: ṁ = 8.5 g/s = 26.4 m³/h of gas at normal conditions (0.44 m³/min).
- At $0.30 per m³ (a typical bulk price; yours will differ) the nitrogen costs about $7.9 per hour of cutting. A large nozzle or a high pressure raises it quickly, and for thin stainless it can rival the electricity.
- Oxygen at only 1 bar through the same nozzle flows 3.8 m³/h: roughly a seventh of the gas, one reason mild steel is still cut with oxygen.
Speed against thickness and power
Cutting speed falls steeply as the plate gets thicker, because the beam must melt (and, with oxygen, burn) a thicker section and the melt must be pushed out of a deeper, narrower kerf. A simple model fitted to one typical data point is v = k P ÷ t1.5; the figure shows it for mild steel with oxygen and stainless with nitrogen. Real tables from the machine maker are always better than a model; use the model to understand the trends and to check a quote.
Worked example: what the model says
- Power: doubling the laser from 3 to 6 kW doubles the speed in 6 mm mild steel: 1.5 to 3.0 m/min.
- Thickness: doubling the thickness (6 to 12 mm) cuts the speed by 2.83 times: at 6 kW from 3.0 to 1.06 m/min. The same 12 mm plate with 3 kW is 0.53 m/min.
- Gas: 3 mm stainless with nitrogen at 3 kW runs at 6.0 m/min (12.0 m/min at 6 kW). Melt-cutting with nitrogen needs much more power than burning with oxygen, so 6 mm stainless at 6 kW is only 4.2 m/min.
- A ceiling: melting a 0.2 mm kerf in 6 mm steel takes about 7.8 J/mm³ (ρ(cΔT + L)), so at 70 % coupling a 3 kW beam could never exceed 13.4 m/min: the real speed above (1.5 m/min) is 11 % of the ceiling, the rest being lost to heat conduction, reflection and the need to eject the melt.
Model speeds against laser power (illustrative; compare your machine’s tables):
| Laser | 10 mm mild steel, O2 | 5 mm stainless, N2 |
|---|---|---|
| 1 kW | 0.2 m/min | 0.9 m/min |
| 3 kW | 0.7 m/min | 2.8 m/min |
| 6 kW | 1.4 m/min | 5.6 m/min |
| 12 kW | 2.8 m/min | 11.2 m/min |
| 20 kW | 4.6 m/min | 18.6 m/min |
Piercing, nozzle and focus
- Piercing is making the first hole before the cut starts. Thick plate takes seconds, spatters melt onto the lens protection and the plate, and is the point where most failures happen. A ramped pierce (rising power, falling pulse frequency) and an oxygen pierce are standard.
- Standoff is the gap between the nozzle and the plate, typically about 1 mm; a capacitive height sensor holds it as the sheet moves. Too large and the gas jet spreads; too small and the nozzle touches the work and can arc.
- Nozzle: single (oxygen, bore about 1.5 mm) or double (nitrogen, bigger bore). A damaged or dirty nozzle gives a lopsided jet and a rough, slanted cut.
- Focus position is set relative to the surface: for oxygen on thick steel near or just above the surface, for nitrogen on stainless below the surface (here about -2 mm), so that the kerf is wide enough for the gas to clear the melt.
- Protective window in the head takes the spatter; check it every shift (see Running a Laser Shop: Costs, Maintenance and Troubleshooting).
Worked example: pierce time and a part
- With the illustrative rule tpierce = 0.1 × t1.5 s, a 3 mm sheet pierces in 0.52 s and a 12 mm plate in 4.2 s.
- A 12 mm plate part with 40 holes spends 40 × 4.2 = 166 s just piercing, against 226 s to cut 4 m of line at 1.06 m/min: piercing is 42 % of the time. Fewer holes, or one large hole instead of many small ones, saves real money.
- A 6 mm part with a 1.2 m perimeter and 8 pierces at 6 kW takes 24 s cutting + 12 s piercing = 36 s (plus travel).
Cut quality (ISO 9013)
ISO 9013 grades a thermal cut by its perpendicularity or slope (range 1 to 5, 1 the best) and by its mean roughness Rz5 (also range 1 to 4). The drag lines on the cut face lean back from the beam; the more they lean, the faster the cut is running compared with its best quality. Other things to judge: dross (resolidified melt on the bottom edge), burrs, a rounded top edge, heat-affected zone and the squareness of corners.
| Defect | Likely cause | Fix |
|---|---|---|
| Dross on the bottom | Speed too high or low, gas pressure low, nozzle damaged, focus wrong | Check the nozzle; slow slightly; raise the pressure; move the focus |
| Rough or wavy face | Oxygen pressure or purity, speed too high, dirty lens | Reduce speed; check the gas and optics |
| Burned corners | Heat builds up in a sharp corner | Reduce power at corners, add a small loop, lengthen the lead-in |
| Taper | Focus position, thickness too great for the power | Adjust the focus; use higher power |
| Pierce spatter | Pierce too fast or at too high power | Ramp the pierce; use a fast-pulse pierce |
| No cut through | Window dirty, power low, gas empty, speed too high | Check window, power, gas supply |
Steel, stainless, aluminum, copper
| Metal | Gas | Notes |
|---|---|---|
| Mild steel | O2 (thick), N2 or air (thin) | The standard. Oxygen cuts fastest on thick plate; the oxide edge may need grinding before paint |
| Stainless steel | N2 | Bright edge; needs high pressure and power; oxygen leaves a dark, oxidized edge that loses corrosion resistance |
| Aluminum | N2 or air | Reflective and conductive; melts and flows easily, so thick sheet leaves dross; a clean, dry surface helps |
| Copper, brass | N2 (O2 for some brass) | Very reflective: at 1 µm copper reflects about 97 % when cold (only 3 % absorbed), so a pulsed pierce and back-reflection protection in the head are needed |
| Titanium | Argon or N2 | Must be shielded or it burns and embrittles; special practice |
| Galvanized, coated, painted | As the base | Zinc fumes and coatings require strong extraction (see Laser Safety, Fire and Fumes) |
Cost per meter and per part
Worked example: machine and gas cost per meter
- 3 mm stainless, nitrogen, 3 kW: speed 6.0 m/min. A machine hour of $80 (depreciation, power, labor, space; see Running a Laser Shop: Costs, Maintenance and Troubleshooting) costs $0.22 per meter; nitrogen $0.02 per meter; total $0.24 per meter.
- 6 mm mild steel, oxygen, 3 kW: speed 1.5 m/min. Machine $0.89 per meter, oxygen $0.01 per meter; total $0.90 per meter.
- The slow thick cut costs about 3.7 times more per meter than the fast thin one: price jobs by cutting length, pierce count and thickness, not by area.
- These are illustrative; use your machine-hour rate and gas prices.
Nesting, common-line and sheet use
The same nesting ideas as in Files, Software and Toolpaths matter even more here, because steel sheet is the biggest cost. Industrial nesting software handles rotation, grain, remnants (offcuts saved for later), and common-line cutting: two parts that share an edge are separated by a single cut.
Worked example: common-line cutting
Two 6 mm parts sharing a 0.35 m edge are cut with one pass instead of two: at 3.0 m/min the shared edge saves 7 s per pair and one pierce. The gap between the parts need not include a kerf either, so more parts fit on the sheet. The limits: the edge must be straight, the parts must not tip or shift when they are separated, and thin webs between parts can overheat and warp.
Tube, profile and 3D cutting
- Tube and profile machines rotate the tube in a chuck while the head cuts holes, slots, mitres and tab-and-slot joints, so that a frame can be assembled like a kit with no marking out.
- 3D (five-axis) heads tilt to cut formed sheet metal and hydroformed parts, with a small tolerance for the tilt and a long programming time.
- Bevel heads tilt to cut weld preparations on plate.
Worked example: cutting a round tube
Cutting a 60 mm round tube (wall 3 mm) straight through takes a path of π × 60 = 188 mm. At the 3 mm speed of 4.2 m/min (model, oxygen, 3 kW) that is 7.5 s, plus the pierce and the chuck rotation. The wall is thin and curved, so the focus must follow the changing standoff.
Related
- Laser Cutting: the overview of this guide.
- Kerf, Accuracy and Designing Parts: kerf and taper.
- Running a Laser Shop: Costs, Maintenance and Troubleshooting: machine-hour cost and maintenance.
- Laser Safety, Fire and Fumes: the hazards of higher power.
- Structures and Strength of Materials for the metals and Industrial Robotics for loading and unloading.
FAQ
Oxygen or nitrogen for steel?
Oxygen for thick mild steel, because it adds heat and runs with lower pressure; nitrogen for a bright, paint-ready edge or for thin sheet, at a much higher gas cost.
Why is a thicker cut so much slower?
More material has to be melted and then blown out of a deeper, narrower kerf: in the simple model the speed falls as the thickness to the power 1.5.
Why is copper hard to cut?
It reflects most of a 1 µm beam when cold and conducts heat away; it needs high power peaks, a pulsed pierce and protection against back-reflection.
What does ISO 9013 measure?
The squareness (slope) and the roughness of a thermally cut face, in classes from 1 (best) to 5 or 4.
How do I price a job?
Add the machine time (cutting length ÷ speed, plus pierces and travel), the gas, and the material with waste, then the handling and a margin.
References
- ISO 9013, Thermal cutting: classification of thermal cuts, geometrical product specification and quality tolerances.
- Steen, W. M., Mazumder, J.: Laser Material Processing (energy balance of cutting; Springer).
- Makers’ cutting tables for fiber lasers (Trumpf, Bystronic, Amada, Han’s Laser) for real parameters.
- Compressed Gas Association data on gas flow through orifices; EN ISO 14121 for machine risk assessment.
Last reviewed: October 2026. Speeds, gas prices and rates are model or typical values: use your machine maker’s tables.