How I Cut Acrylic Sheet on a CO2 Laser (Without Melted Edges or Cracking)

Who This Checklist Is For

I run purchasing for a small fabrication shop—about 15 people, mostly makers and small-batch production. We bought a Thunder Laser CO2 unit (the Nova 24) in 2023, and within the first month, I learned that cutting acrylic sheet is not as straightforward as the YouTube videos make it look.

This checklist is for anyone who has a CO2 laser (maybe a Thunder, maybe something else) and needs to cut acrylic cleanly. Not the theory. Just what works.

Five steps. That’s it.

Step 1: Confirm You Have the Right Material

This is the step I screwed up first. I ordered "acrylic sheet" from a supplier without specifying cast vs. extruded. Big mistake.

Cast acrylic cuts cleanly. Extruded acrylic melts, bubbles, and leaves frosted edges. The difference is how the material is made—cast is poured, extruded is pushed through a die. And the price difference is maybe 15-20%.

Most buyers focus on per-sheet pricing (like I did) and completely miss that the wrong type of acrylic costs you time, material, and rework—easily 30-50% more in hidden costs.

Checklist:

• Is the acrylic labeled "cast"? (If it doesn't say, assume it's extruded.)
• Do you have a small test piece? (Always test before cutting the full sheet.)
• Is the protective paper still on both sides? (Leave it on—it helps with edge quality.)

(Note to self: I still kick myself for not verifying material type on that first bulk order. Cost us about $300 in wasted sheet and a weekend of re-cutting.)

Step 2: Set the Correct Focus and Speed

The assumption is that more power cuts faster. The reality is that speed and focus matter more than raw wattage. I've seen people crank their 80W tube to max and still get burnt edges because they were running too slow.

For a standard 1/8" (3mm) cast acrylic on a Thunder CO2 laser:

• Speed: 15-20 mm/s (900-1200 mm/min)
• Power: 40-60% (not full power)
• Frequency: 500-1000 Hz (higher frequency = smoother edge)

Focus is critical. The focal point should be at the middle of the material thickness. If you focus on the surface, the bottom edge will be rougher. If you focus too deep, the top edge burns.

What I mean is that this isn't a "set and forget" thing—you need to adjust focus for each material thickness. I've been using a manual focus gauge, but we're planning to upgrade to an autofocus head eventually (note to self: actually submit that purchase request this quarter).

Step 3: Configure Air Assist and Exhaust

This is the step most beginners ignore. And honestly? I did too, at first.

Without air assist, the laser creates a flame that melts the acrylic unevenly. The edge gets that cloudy, frosted look—exactly what you don't want. With air assist at 20-30 PSI, the flame is suppressed, and the cut edge comes out clear.

People think air assist is just for preventing fires. Actually, it's primarily for cut quality. The fire prevention is a bonus.

Exhaust is also underrated. If fumes aren't pulled away fast enough, they condense on the lens and mirrors—reducing cutting power and leaving residue. We vacuum our exhaust line every 40 hours of operation (I really should schedule that more consistently).

Quick tip: If you see yellow smoke or smell a strong burnt plastic smell, your exhaust is struggling. Stop and check the vent path.

Step 4: Use a Honeycomb or Slat Bed (Not a Flat Sheet)

Wait—this is the step that surprised me.

When I first set up the machine, I figured a flat metal sheet would work fine. The laser would cut through the acrylic and hit the metal. Wrong.

The reflected laser beam bounced off the metal and scorched the bottom of the acrylic. Plus, the melted acrylic stuck to the flat surface and needed to be chiseled off. Not ideal. Not workable.

Use a honeycomb bed (or a slat bed) that elevates the material. The laser passes through the gaps, minimizing reflection and sticking. Our Thunder came with a honeycomb bed, but I almost didn't install it. (Thankfully, I read the manual—finally.)

If you don't have a honeycomb bed, you can use a scrap sheet of MDF or plywood as a sacrificial layer. The laser will cut into it instead of hitting the metal bed. Less clean, but better than nothing.

Step 5: Test Cut and Adjust Settings

You need a test piece. Not a full sheet. A small corner piece, maybe 2"x2". Cut a square or a circle, then examine the edge.

What to check:

• Is the edge clear? (Good) or cloudy/frosted? (Bad—adjust speed or power)
• Any scorch marks? (Bad—reduce power or increase speed)
• Is the cut all the way through? (If not, increase power slightly or slow down)
• Are there bubbles near the cut line? (Material may be extruded, not cast)

In my experience, a clean cut on cast acrylic should look like glass—transparent edges with no discoloration. If you see any yellowing, you're burning the material.

The question everyone asks is: "What's the perfect setting for my machine?" The question they should ask is: "What's my baseline, and how do I adjust from there?"

(Mental note: I've been running 16mm/s at 55% power on our Nova 24 for 3mm cast—that's our sweet spot. But every machine is slightly different.)

Common Mistakes and What I Learned the Hard Way

Mistake 1: Cutting too fast. The material doesn't cut through fully, and you have to run it again—which wastes time and creates a double-burn mark. Cost me about 30 minutes per failed cut.

Mistake 2: Not cleaning the lens regularly. The lens gets coated with residue from acrylic fumes. A dirty lens reduces cutting power by 20-30%. Clean it after every 10 hours of cutting acrylic.

Mistake 3: Ignoring material thickness calibration. 1/8" and 1/4" acrylic require very different settings. Don't assume you can just double the power.

Like most beginners, I thought laser cutting was simple: hit "go" and walk away. The reality is that preparation and settings make or break your results. Spend 15 minutes on setup, save 2 hours of rework.

Prices as of February 2025 (verify current rates): Cast acrylic sheet (1/8" x 24" x 48") runs about $25-40 per sheet from major suppliers. Extruded is $18-30. The upgrade to cast is worth the 30% premium for clean cutting results.