It's the question we get most often when a new drawing arrives: should this be laser or plasma? The answer is almost never "one is better." It comes down to three variables: thickness, material and required tolerance.
The underlying difference
Fiber laser cutting concentrates a light beam into a spot a few tenths of a millimeter wide. It melts and vaporizes material in a very small zone, producing a narrow kerf and a minimal heat-affected zone.
Plasma cutting fires a jet of ionized gas at high temperature. It carries far more raw power, but the arc is wider, so the cut is less fine and leaves a larger heat-affected zone.
In short: the laser is a scalpel, plasma is a well-sharpened axe. Both are useful — for different jobs.
Head-to-head
| Criterion | Fiber laser | Plasma |
|---|---|---|
| Optimal thickness | 0.5 – 25 mm | 6 – 50 mm |
| Typical tolerance | ±0.1 mm | ±0.5 to ±1.0 mm |
| Kerf width | 0.1 – 0.4 mm | 1.5 – 4 mm |
| Heat-affected zone | Very low | Moderate to high |
| Edge finish | Smooth, weld-ready | Needs grinding |
| Speed on thin stock | Very high | Medium |
| Speed on thick stock | Low | Very high |
| Cost per meter, thin | Low | Medium |
| Cost per meter, thick | High | Low |
When to choose laser
- Thicknesses up to 25 mm in carbon steel, and up to 20 mm in stainless.
- When the part needs a tight tolerance — parts that will later be assembled or machined.
- Geometries with fine detail: narrow slots, small holes, text, complex profiles.
- When the edge goes straight to welding with no intermediate step. That saves a whole operation.
- Medium and large runs of thin sheet, where speed offsets the hourly rate.
When to choose plasma
- Thick plate, 25 mm and up. Laser becomes slow and expensive here.
- Heavy structures where a ±1 mm tolerance is perfectly acceptable.
- Roughing and plate breakdown for structures that will later be machined or welded with edge preparation.
- When cost per meter drives the decision and finish is not critical.
The most common mistake
Asking for laser on a 40 mm structural plate "because it's more precise." At that thickness the laser is painfully slow, burns gas and wears optics — and the structure is going to be welded to a millimeter-level fit-up tolerance anyway. Plasma does the same job in a fraction of the time and cost.
The reverse mistake exists too: plasma-cutting a 3 mm part that later needs a tight assembly fit. You end up paying for a grinding operation the laser would have saved you.
Practical rule: if the part mates against another with a fit, use laser. If it gets welded inside a structure with clearance, use plasma.
What to ask your supplier for
When you request a cutting quote, don't default to "laser cutting." Send the drawing with:
- Exact thickness and material — A36 is not the same as 304 stainless.
- The tolerance you actually need, not the tightest possible. Every tenth costs money.
- What happens to the edge afterward — welded, machined, or left visible.
- Quantity — it completely changes which process wins.
With those four data points, a serious supplier will recommend the right process, even when it's the cheaper one for them.
How we do it at GITV
At our plant in Cd. Sahagún we run a 6 kW fiber laser for sheet up to 25 mm, holding ±0.1 mm tolerances. For thick plate and structural roughing we use plasma. When a drawing comes in, process selection is part of the quote: we tell you which one fits and why, with the cost of each option.
All under ISO 9001:2015, with batch traceability and documented dimensional control.