Acrylic & Plastic: Diode Limits
Diode + acrylic is a frustrating combination. Clear acrylic is transparent at 450nm, diode passes through with no effect. Opaque colored acrylic works but slowly. Here's what's possible and what isn't.
Clear acrylic
Diode CAN'T cut or engrave clear acrylic. The 450nm wavelength passes through clear cast or extruded acrylic without absorption. Use CO2 instead.
Workaround attempts (limited success):
- Spray with water-soluble paint that absorbs blue light, engrave through it. Messy and unreliable.
- Apply mask with absorber (special blue-absorbing tape). Works but specialty product.
- Use DARK acrylic (black, navy, dark green), the substrate absorbs the beam directly.
Opaque acrylic: what works
Black, dark blue, dark green, dark red, these absorb 450nm well enough for cuts.
| Color | Cut 3mm | Cut 5mm | Engrave (frosted) |
|---|---|---|---|
| Black cast | 100 mm/min · 100% · 4-6 passes | 60 mm/min · 100% · 8-10 passes | 3000 mm/min · 30% |
| Dark blue / navy | 120 mm/min · 100% · 4-5 passes | 80 mm/min · 100% · 7-9 passes | 2500 mm/min · 35% |
| Red / dark red | 150 mm/min · 100% · 3-4 passes | 100 mm/min · 100% · 6-8 passes | 3000 mm/min · 30% |
| White / yellow / light pastel | Doesn't cut, too reflective | n/a | n/a |
Caveats: diode acrylic vs CO2 acrylic
- Edge quality: diode-cut acrylic edges are MATTE / FROSTED. Never flame-polished. CO2 cast acrylic edges are glass-clear from the cut.
- Speed: diode cuts are 5-15× slower than CO2.
- Smell: burning acrylic stinks; ventilate aggressively.
- For premium signage: CO2 is the right choice. Diode acrylic looks DIY.
Plastics that work on diode
- ABS (dark): engraves with light gray foam mark. Cuts thin sheets slowly.
- Delrin (dark): cleaner cuts than ABS. Used for laser-cut gears.
- HIPS (high-impact polystyrene) dark colored: cuts thin sheets reasonably.
- Painted plastic (any plastic with surface paint that absorbs blue light): diode ablates the paint, exposes substrate.
Plastics that DON'T work
- Clear acrylic (transparent at 450nm).
- Clear polycarbonate (same problem; also yellow burn).
- Light-colored plastics in general.
- HDPE / PE, melts before vaporizing.
Plastics that are TOXIC to laser
- PVC / vinyl, chlorine gas. Damages your shop and your lungs.
- Polycarbonate (Lexan), yellows / chars badly; phenolic + CO fumes. Doesn't laser-cut cleanly. (Bromine release only applies to brominated flame-retardant PC, not standard sheet.)
- Foam-core with styrene, toxic styrene fumes.
- Unknown plastics, if you don't know. Don't burn.
The honest verdict
If acrylic and plastic work is a major part of your business, buy a CO2 instead of a diode. The diode can be your secondary "wood and paper" station while CO2 handles plastics. Trying to do all-acrylic on a diode is a productivity dead-end.