Can you laser cut acrylic?

Key facts

• Laser type: CO2, at 10.6 µm (some run at 9.3 µm). Acrylic absorbs it whatever the color, clear included.
• How fast it's absorbed: PMMA (acrylic) has an absorption coefficient of about 500 to 540 per cm at 10.6 µm. That means about 99% of the beam is absorbed in the top 0.1 mm (0.004 in.).
• Edge: glossy and clear straight off the machine. No sanding or polishing.
• Thickness: 1/16 to 1/2 in. is routine. Perspex rates its cast sheet for laser cutting up to 25 mm (1 in.), with testing needed above 12 mm.
• Power rule of thumb: about 10 W per 1 mm (0.04 in.) of thickness for a polished cut at a reasonable speed (Trotec).
• Accuracy: typical tolerance about ±0.005 in., kerf about 0.006 to 0.010 in.
• Lasers that don't work on clear acrylic: blue diode lasers (about 450 nm) and fiber lasers (1064 nm). Clear acrylic transmits about 92% of visible light and about 90% of near-infrared light.

Why do CO2 lasers cut acrylic so well?

A laser only cuts what absorbs its light. CO2 lasers emit far-infrared light, and acrylic is close to opaque at that wavelength. Measured absorption coefficients for PMMA at 10.6 µm are around 500 to 540 per cm. The beam's energy goes into the first few hundredths of a millimeter of plastic, which heats and vaporizes. Plaskolite's fabrication guide calls this ablation and says it leaves a clean, square, polished edge.

The edge melts for an instant and then sets smooth. That's why a laser-cut acrylic edge comes off the machine glossy and clear, close to a sawn edge that's been flame polished by hand. Wood chars under a laser. Acrylic turns mostly to vapor, so it doesn't.

How thick can a laser cut acrylic?

It depends on the laser's power and how much edge quality you'll accept. Epilog's published single-pass guide is roughly 1/8 in. at 30 to 40 W, 1/4 in. at 50 to 60 W, 3/8 in. at 80 to 100 W, 1/2 in. at 120 W, and 3/4 in. at 200 W. Here's what that looks like in practice:

Laser makers say one pass is best. Trotec notes that each extra pass leaves visible lines on the edge. We laser cut up to 1/2 in. thick. For 3/4 and 1 in. sheet we CNC route it instead and can flame or diamond polish the edges afterward.

Cast vs extruded acrylic on a laser

Both cut well. The differences are small but real:

• Engraving: cast acrylic engraves to a bright, frosty white. Extruded engraves clear, with little contrast. Trotec and Epilog both describe it this way. For anything that will be engraved, choose cast.
• Cut edge: both leave a glossy edge. Extruded cuts with a little less power, and Epilog says it gives the most flame-polished look. It also melts more readily, so very small features can soften. Results vary by maker and grade.
• Stress: laser edges carry some built-in stress. Perspex and Plaskolite both warn it can lead to crazing if solvents touch the edge. See why laser-cut acrylic sometimes cracks later.

More on the two types in cast vs extruded acrylic.

Can a diode or fiber laser cut acrylic?

Mostly no. It's the most common surprise for people who buy a hobby laser.

• Blue diode lasers (about 450 nm) are visible light. Acrylite's data shows clear sheet transmitting 92% of light from 395 to 1000 nm, so the beam mostly goes through. Thin black or dark opaque acrylic can be cut slowly, because its pigment absorbs the light. Blue acrylic is especially hard, since it's made to pass blue light.
• Fiber lasers (1064 nm) are built for metal. Clear acrylic transmits about 90% of light from 700 to 1400 nm. Some colored sheet can be marked, but fiber lasers aren't a practical way to cut acrylic.

The full explanation is in why diode lasers can't cut clear acrylic.

Why is a laser the best way to cut detailed parts?

• No tool radius. A focused CO2 beam is about 0.004 to 0.007 in. across with a standard 2 in. lens, so inside corners come out sharp. A router bit always leaves a radius equal to its own size.
• No clamping force. Nothing pushes on the part, so thin, delicate shapes don't chip or chatter.
• Accuracy. Typical laser tolerance is about ±0.005 in., with a kerf of about 0.006 to 0.010 in. (more on laser kerf).
• Finished edge. The edge is already polished, which saves a whole step on signs, displays, and gifts.
• Engraving in the same setup. Text, logos, and fill engraving happen on the same machine as the cut.

When is routing better than laser cutting?

A laser isn't always the right tool. We route the part instead when:

• The sheet is thicker than 1/2 in. Routing keeps edges square instead of tapered.
• The edges will be solvent-bonded into a box or case. The Plexiglas fabrication manual says not to flow solvent cement onto laser-cut edges, because they carry the most fabrication stress. A machined edge is the most forgiving for bonding.
• The part will see solvents, cleaners, or flexing in service, where laser-edge stress could lead to crazing.
• You want a satin edge or a diamond-polished one, rather than the laser's glossy, slightly rounded look.

The trade-offs are laid out in laser-cut vs router-cut acrylic edges.

Getting your parts laser cut

Send us a DXF or SVG drawing and you'll see a price instantly: upload your file. If you're not sure which process fits, tell us what the part does and we'll pick. You can read more about our laser cutting service.

Questions

Sources

• Plaskolite: OPTIX-L Continuous Cast Acrylic Sheet Fabrication Guide (laser section)
• Perspex: Design Guide, laser cutting and engraving
• Trotec: Working with acrylic, Laser Processing Guide
• Epilog Laser: Acrylic laser cutting and engraving
• Acrylite: Light Transmission and Reflectance, Extruded Sheet
• Canestri, Photomedicine and Laser Surgery (2011): absorption coefficient of PMMA at 10.6 µm