CO2 — EVO · LS · HP
PMMA, Plexiglas, Perspex
Everyone
Fire, not fumes
Acrylic (PMMA) is the material CO2 lasers handle best. It vaporizes cleanly rather than melting or charring, which is why a correctly-set machine leaves a glossy, flame-polished edge with no secondary finishing. The critical distinction is cast vs. extruded: cast gives the polished edge and the bright frosty-white engraving people expect; extruded is cheaper, cuts acceptably, and engraves to a dull nearly-clear mark that no setting will fix. They’re visually identical, so you buy by specification. The main hazard isn’t fumes — acrylic is comparatively benign — it’s fire.
1 · Why acrylic cuts so well.
Acrylic absorbs 10.6 µm strongly and, crucially, goes more or less straight from solid to vapour at the cut front rather than melting into a pool. Very little molten material is left behind to re-solidify as a rough edge, and the heat that remains briefly re-flows the surface into a gloss.
That’s the flame-polished edge — a genuine physical result of the material’s behaviour, not a finishing step someone added. For an industry that used to saw and then flame-polish acrylic by hand, it’s the reason laser cutting took over.
2 · Cast vs. extruded — the decision.
| Cast | Extruded | |
|---|---|---|
| Cut edge | Glossy, clear, flame-polished | Acceptable, softer; more prone to a melted look |
| Engraving | Bright frosty white — high contrast | Dull, nearly clear — low contrast |
| Cutting speed | Slower — generally needs a little more energy | Faster; cuts more readily |
| Thickness consistency | More variation sheet to sheet | More consistent — better where focus is critical |
| Cost | Higher | Lower |
| Use it for | Signage, displays, awards, anything engraved | Cut-only parts where the edge isn’t the feature |
The single most common acrylic complaint
“My engraving looks clear instead of white.” That is extruded acrylic, essentially always. It isn’t a settings problem and there’s no setting that fixes it — the white frost is a property of cast material. If engraving contrast matters to the job, specify cast when you order and check what actually arrived.
3 · Settings — where to get real numbers.
Acrylic is forgiving enough that most machines cut it well across a broad range, but the difference between a polished edge and a slightly frosted one is real and worth dialling in.
Boss publishes its own cut-and-engrave settings by material for CO2 machines, including acrylic across power classes — that’s the right starting point, rather than a generic figure from a forum. CO2 settings by material
General principles that hold regardless of the numbers: enough power to cut in one pass usually beats multiple passes on acrylic (re-cutting a kerf tends to dull the polish), and slightly lower speed with adequate air assist gives a cleaner edge than brute power.
4 · Protective masking — remove it or not?
Acrylic ships with paper or film masking, and it’s a real decision:
- Leave it on for cutting where you want the face protected from smoke residue and handling marks.
- Take it off for engraving — you’re removing surface material, and masking interferes and can leave adhesive behind.
- Watch what the masking is. Paper masking burns and adds smoke; some films are fine and some are vinyl-based, which puts them straight onto the never-cut list. If the masking is unidentified, remove it. Why that matters →
5 · The real risk is fire.
Acrylic sustains a flame readily
Acrylic is chemically among the more benign laser materials — no corrosive products, no acid. But it burns, and it will keep burning after the beam has moved on if conditions allow. That makes it one of the more common causes of laser fires, precisely because people relax around a “safe” material. Air assist running, extraction running, machine never unattended. Small flames at the cut are normal and self-extinguishing with proper air assist; a flame that persists after the head moves away is not, and needs immediate attention.
Beyond fire, ordinary good practice applies: extraction handles the vapour (which is unpleasant to breathe even though it isn’t corrosive), and a clean bed keeps offcuts from becoming kindling under the work.
6 · Watch for lookalikes.
Clear rigid sheet is not automatically acrylic. Polycarbonate looks nearly identical and behaves badly under a laser; PETG is another common substitute; and some “acrylic-look” display sheet is neither. The consequences range from a disappointing edge to a genuinely bad idea.
Buy from a supplier who states the material, and treat unlabelled clear sheet from the offcut bin with the same suspicion as any unknown plastic. Telling acrylic and polycarbonate apart →
7 · FAQs
Frequently asked
AcrylicQCast or extruded — which should I buy?
Cast if the job is engraved or the edge is visible; extruded if you’re cutting parts where the edge isn’t the feature and cost matters. Cast engraves bright white and polishes clear; extruded engraves nearly invisibly.
QWhy is my engraving clear, not white?
It’s extruded acrylic. The frosty white is a property of cast material, and no setting change produces it on extruded stock. Buy cast.
QDoes laser-cut acrylic need polishing?
Not on cast acrylic with a correctly set machine — the edge comes off glossy and flame-polished with no secondary finishing.
QIs acrylic dangerous to cut?
Chemically it’s one of the safer materials — no corrosive products. The real risk is fire, since acrylic sustains a flame. Air assist and extraction running, and never leave the machine unattended.
8 · Related in this series.
Part of Materials & Safety:
- Polycarbonate — the lookalike that behaves nothing like it
- Which plastics cut well — acrylic in context
- What must never go in a laser — including some maskings
- Vaporization cutting — why acrylic polishes
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.