Article
Laser Cutting Explained (2026): Fiber vs CO2, Kerf, Materials & Nesting
Cutlistor Team5 min read
Introduction
Laser cutting uses a focused beam to melt, burn, or vaporize material along a programmed path. For sheet metal fabricators, it is the default process for thin to medium gauge parts that need tight tolerances, clean edges, and fast cycle times on stainless, mild steel, and aluminum.
This guide explains how laser cutting works in a fab shop, compares fiber and CO2 platforms, lists practical thickness and material limits, covers kerf and edge quality, and shows where rectangular cut planning tools like Cutlistor fit before parts go to SigmaNEST-class CAM.
How laser cutting works
A laser cutter generates a high-power beam, focuses it through optics onto the sheet, and moves the head (or table) along X and Y axes. Assist gas, usually nitrogen for stainless and aluminum or oxygen for mild steel, blows molten metal out of the kerf and protects the lens.
The controller reads NC code from CAM software. That code includes lead-ins, pierce delays, power ramps, and contour toolpaths. Nesting software upstream decides how many parts fit on each sheet and how skeleton waste is handled before the laser ever fires.
- Pierce: the beam drills a start hole before contour cutting begins
- Cut: constant or ramped power follows the part outline
- Traverse: rapid moves between features with the beam off
- Tabbing: small bridges hold parts in the nest until unloading
Fiber laser vs CO2 laser
| Factor | Fiber laser | CO2 laser |
|---|---|---|
| Wavelength | Around 1 µm, absorbed well by metals | Around 10.6 µm, versatile on organics |
| Efficiency | High wall-plug efficiency, lower running cost | Lower efficiency, more cooling and gas |
| Speed on thin steel | Very fast on gauge sheet | Competitive on thin sheet, slower on thick |
| Reflective metals | Modern fibers handle aluminum and brass better than early units | Can struggle with highly reflective alloys without care |
| Maintenance | Fewer consumables, long diode life | Mirror alignment, tube replacement, more downtime |
| Typical shop role | Primary sheet cutter for fab and job shops | Legacy installs, mixed material shops |
Materials and practical thickness limits
Laser cutting handles most metals used in fabrication, plus some plastics and composites on CO2 systems. Thickness limits depend on laser power, assist gas, and the quality bar your customer expects.
Common metals on fiber lasers
- Mild steel: excellent cut quality from thin gauge to roughly 25 mm on high-power fibers, with oxygen assist on thicker plate
- Stainless steel: nitrogen assist gives oxide-free edges on 304/316 up to roughly 20-30 mm depending on power
- Aluminum: nitrogen cutting on 5052, 6061, and tread plate; watch reflective pierce settings on polished surfaces
- Galvanized steel: cuttable with process tuning; zinc vapor needs extraction and can affect edge coating
Thickness sweet spots
Job shops most often laser-cut 1.5 mm to 12 mm mild steel and 1 mm to 8 mm stainless or aluminum on 4-6 kW machines. Above that range, plasma or waterjet often wins on cost per meter, even if laser could technically cut thicker.
Edge quality and kerf
| Process | Typical kerf (sheet steel) | HAZ / dross |
|---|---|---|
| Fiber laser | 0.1-0.3 mm | Small HAZ, low dross when tuned |
| CO2 laser (metal) | 0.15-0.4 mm | Similar to fiber on thin sheet |
| Plasma | 1.0-3.0+ mm | Wider kerf, visible HAZ, more dross |
| Waterjet | 0.8-1.2 mm (abrasive) | No thermal HAZ, matte edge |
Cutlistor applies a single kerf value when building rectangular 2D nests for sheet estimating. True-shape CAM (SigmaNEST, TruTops, etc.) handles contour toolpaths, lead-ins, and variable kerf on arcs separately. Use Cutlistor for BOM sheet counts and yield planning; use CAM for machine-ready laser programs.
Laser speed vs plasma
| Thickness (mild steel) | Typical winner | Why |
|---|---|---|
| 0.9-3 mm | Fiber laser | High speed, tight nests, minimal cleanup |
| 3-12 mm | Fiber laser (most job shops) | Balance of speed, edge quality, and tolerance |
| 12-25 mm | Mixed: laser or plasma | Laser if tolerance matters; plasma if cost per kg matters |
| 25 mm+ | Plasma or waterjet | Laser capital and running cost rise; kerf and HAZ grow |
When fab shops choose laser cutting
- Tight tolerances on holes, slots, and outer profiles without secondary machining
- High mix, medium volume jobs where tooling-free flexibility beats punching
- Stainless and aluminum parts that need clean, paint-ready edges
- Fine features, small radius corners, and intricate flat patterns
- Jobs where narrow kerf directly saves material on expensive alloys
Nesting implications and cut planning
Laser profit depends on sheet yield as much as feed rate. Common sheet sizes (1250 x 2500 mm, 1500 x 3000 mm, 5 x 10 ft) should be loaded with as many parts as kerf, grain direction, and handling tabs allow. Rectangular nesting estimates how many sheets a BOM needs before CAM spends time on true-shape nests.
Rectangular planning vs true-shape CAM
Cutlistor nests rectangles in the browser: part length, width, quantity, kerf, and trim margins. It exports PDF cut plans for estimating and quoting; DXF export is available on paid plans. It is not a machine controller and does not replace laser CAM for pierce strategy, common-line cutting, or fly-cut ordering.
Where SigmaNEST-class tools fit
Production laser lines use CAM nesting with part-in-part, remnant tracking, and machine post-processors. Cutlistor complements that stack for early quoting, purchase orders, and rectangular what-if layouts. Compare approaches in our SigmaNEST alternatives and Cutlistor vs SigmaNEST articles if you are evaluating software spend.
Conclusion
Laser cutting delivers narrow kerf, fast cycle times on gauge sheet, and excellent detail on stainless, mild steel, and aluminum. Fiber lasers dominate new equipment purchases; CO2 remains relevant in mixed and legacy shops. Plan rectangular sheet counts and kerf-aware yield in Cutlistor before CAM builds machine programs, and reserve true-shape nesting for production laser CAM when contours, lead-ins, and machine posts matter.