CO2 — poorly
PC, Lexan, Makrolon
Everyone
Thin sheet at best
Polycarbonate cuts badly in a CO2 laser, and the reason is specific: it absorbs 10.6 µm very strongly right at the surface, so energy concentrates there instead of driving through the material. The result is a yellow-to-brown discoloured edge, charring, and a real tendency to catch fire. It gets rapidly worse with thickness — thin film is workable, and heavier sheet generally isn’t worth attempting. It is not a safety prohibition like PVC: no corrosive products, no machine damage. It’s simply the wrong material for the tool, and the most common reason people meet it is that they thought they’d bought acrylic.
1 · Why it behaves so differently from acrylic.
Acrylic and polycarbonate look the same and are both clear rigid plastics, so the difference in laser behaviour surprises people. It comes down to where the energy goes.
Acrylic absorbs the beam and goes more or less straight to vapour at the cut front, carrying the heat away with the removed material — which is what leaves a polished edge. Polycarbonate absorbs even more strongly, but degrades thermally instead of vaporising cleanly. The energy stays in the surface layer as heat, and the polymer discolours and chars rather than clearing out of the kerf.
So the same property that makes acrylic excellent — strong absorption at 10.6 µm — works against polycarbonate, because what the material does with the absorbed energy is different.
2 · What you actually get.
| Symptom | Cause |
|---|---|
| Yellow or brown edge | Thermal degradation of the polymer — inherent, not a settings error |
| Charred, sooty kerf | Burning rather than vaporising |
| Flame at the cut | Polycarbonate sustains combustion readily |
| Incomplete cuts on thicker stock | Surface absorption means the beam struggles to reach depth |
| Rapid deterioration with thickness | Same mechanism, compounding — thin film is fine, sheet is not |
If you must cut it
Thin stock only, lower power with higher speed to limit dwell, strong air assist, and expect to accept a discoloured edge. Test on scrap and decide whether the result is genuinely acceptable before committing material. For most jobs the honest answer is to use acrylic instead — and if the part specifically needs polycarbonate’s impact resistance, that’s a good reason to cut it by another method.
3 · Telling acrylic and polycarbonate apart.
This matters more than the cutting advice, because the usual way people meet this problem is by accident.
| Test | Acrylic (PMMA) | Polycarbonate (PC) |
|---|---|---|
| Label / data sheet | PMMA, Plexiglas, Perspex | PC, Lexan, Makrolon |
| Flex a scrap piece | Rigid and brittle — cracks or chips | Tough — bends without breaking |
| Tap it | Sharper, ringing sound | Duller sound |
| Edge appearance | Often slightly bluish on the cut edge | Often faintly yellowish |
| Price | Lower | Noticeably higher |
The flex test is the practical one: if a clear sheet survives being bent hard, treat it as polycarbonate. None of these is a substitute for a data sheet, but they’re enough to stop a job before it wastes material.
4 · Where it sits on the risk scale.
Worth being precise, because polycarbonate often appears on “never laser” lists alongside PVC, and that’s misleading. It doesn’t release corrosive products and it won’t damage your machine chemically. The concerns are ordinary ones: fire risk from charring and flaming, and the fumes of any burning plastic, which extraction handles.
So: a quality decision, not a prohibition. The distinction matters because treating everything as equally forbidden makes the genuinely forbidden list easier to ignore. The list that is a prohibition →
5 · FAQs
Frequently asked
PolycarbonateQCan you laser cut polycarbonate?
Thin sheet, poorly. It absorbs 10.6 µm strongly at the surface so heat concentrates there instead of cutting through — the edge yellows, chars and often flames. It worsens quickly with thickness.
QWhy does it turn yellow?
Thermal degradation of the polymer. It’s inherent to the material at this wavelength, not a settings error you can dial out.
QHow do I tell it from acrylic?
Label or data sheet first (PC vs PMMA). Physically, acrylic is brittle and cracks when flexed; polycarbonate bends without breaking. If a clear sheet survives a hard bend, treat it as polycarbonate.
QIs it dangerous?
Not in the PVC category — no corrosive products, no machine damage. Fire and ordinary burning-plastic fumes are the concerns. It’s a quality problem, not a prohibition.
6 · Related in this series.
Part of Materials & Safety:
- Acrylic — what to use instead, nearly always
- Which plastics cut well — the ranked guide
- What must never go in a laser — the real prohibition list
Keep exploring
One idea leads to the next.
Knowing how a material behaves under the beam is most of the job. Follow the rest of the series, or talk it through with someone who runs these systems.