settings · acrylic · cutting
Acrylic Cutting Settings (Opaque Only — Clear Acrylic Cannot Be Cut by Diode Lasers)
On a 20W diode laser, cutting opaque cast acrylic (3mm) requires 95% power, 800 mm/min, 3 passes. Confidence is low — acrylic absorptivity varies significantly with color and dye formulation. Dark colors cut more readily than light ones. Confirm all settings with a test grid before production cuts. Settings normalized from community reports via the Laser Tinkerer Energy Index.
- High energy needed: EI ≈ 1.07 J/mm — roughly 10× more than basswood cutting, with low confidence due to color dependency
- Opaque colored acrylic absorbs 450nm light; dark pigments absorb more readily than pastels or white
- Cast acrylic is far easier to cut than extruded acrylic — extruded tends to melt and re-fuse on the cut path
- Air assist is critical — it clears molten acrylic from the kerf and dramatically reduces recutting of already-melted material
Cutting settings — opaque cast acrylic, 3mm
| machine class | speed (mm/min · mm/s) | power | passes | EI (J/mm) | air assist | source |
|---|---|---|---|---|---|---|
| 10W | 300 · 5.0 | 95% | 4–5 | 1.14 | required | |
| 20W ★ | 800 · 13.3 | 95% | 3 | 1.07 | required | community reports, r/lasercutting |
| 33W | 1,000 · 16.7 | 85% | 2–3 | 1.02 | required | |
| 40W | 1,200 · 20.0 | 80% | 2–3 | 0.96 | required |
Technique for diode lasers on opaque acrylic
Air assist is not optional. Cutting acrylic produces a molten kerf. Without airflow, the material re-melts and fuses back together between passes, and the result is no cut at all. Use medium air assist pressure (6–12 PSI) directed precisely at the focal point.
Cast vs extruded acrylic. Cast acrylic (CAST or GS on the manufacturer label) cuts better than extruded (XT, EX). Extruded acrylic tends to melt unevenly and can chip or crack rather than cut cleanly. Always prefer cast for laser cutting.
Multiple slow passes are better than one fast pass. Start with 3–4 passes at the table speeds. The first pass ablates; the second removes debris; the third cuts through. Speed up once you have a cut to find the minimum pass count.
Color matters significantly. Dark black or dark-colored acrylic absorbs 450nm light more readily than light-colored or pastel acrylic. You may need 50–100% more passes for white or bright-colored acrylics compared to black.
fume safety note
Acrylic (PMMA) generates methyl methacrylate and acrylic polymer fragments when cut. These are irritants, not acute toxins, but ventilate well. Never confuse acrylic with polycarbonate (Lexan) — polycarbonate releases bisphenol A (BPA) and irritating fumes when lasered and should never be cut. Acrylic and polycarbonate have different physical properties: acrylic is more brittle and shatters; polycarbonate is tough and bends without breaking. If in doubt, do not laser it.
FAQ
Why can't my diode laser cut clear acrylic? The 450nm blue wavelength emitted by diode lasers is transparent to clear PMMA (polymethyl methacrylate). The beam passes through the material without being absorbed, so no heating occurs. A CO₂ laser at 10.6µm is absorbed by acrylic — that is why CO₂ lasers are the standard choice for acrylic cutting.
Can I use dark paint or tape to cut clear acrylic? Partially — black masking tape or black spray paint on the surface creates an absorbing layer that the beam can ablate. But this only marks or partially scores the surface; it does not enable through-cutting of thick acrylic because the laser energy is still reflected or scattered by the clear bulk material below the absorbing layer.
What about engraving clear acrylic? Surface engraving of clear acrylic is possible — TiO₂-based marking compounds (like Cermark or Brilliance Laser Ink) applied to the surface create an absorbing layer that fuses into the surface when lasered. This leaves a white or frosted-looking mark on clear acrylic. See the full capability guide for more on engraving vs cutting.
- Opaque/colored cast acrylic sheets — ensure these are cast acrylic (PMMA), not polycarbonate; cast cuts cleaner than extruded
- Air assist pump — critical for acrylic cutting to keep the kerf clear and reduce re-melting
- Honeycomb cutting bed — prevents the acrylic from resting on a solid surface, which causes melt-back on the underside
As an Amazon Associate I earn from qualifying purchases. Links are to search results — no specific product is tested or endorsed.