My xtool s1 Melted My Acrylic: The Real Settings That Saved My 48-Hour Rush Order

You have to know exactly what you're doing with the xtool s1 and acrylic, or you'll end up with a melted mess. Here's what saved my rush order.

Last Thursday, 34 hours before a client's trade show, my usual acrylic cutter gave out. I grabbed our xtool s1 20 watt module from the shelf, thinking, "It's a desktop laser, how bad could it be?" Bad. I ruined three $40 pieces of cast acrylic before I got it right.

In my role coordinating custom sign fabrication for a small events company, I've learned that the xtool s1 acrylic cutting settings are not the same as your CO2 laser's. This is the biggest mistake I see. People assume the 20-watt diode module behaves the same. It doesn't. Here's what actually works, based on a weekend of controlled burns and exactly why my first three attempts turned into puddles.

The settings that saved my deadline

For a clean cut through 3mm cast acrylic with the xtool s1 20 watt module: Speed: 15mm/s, Power: 100%, 3 passes. That's it. Don't try to do it in one pass at 5mm/s; that's what causes the melt.

I'm not 100% sure this is the absolute fastest, but it gave me a flame-polished edge with zero crazing. For 5mm extruded acrylic, I had to drop the speed to 10mm/s and go 4 passes. The key difference is that cast acrylic needs faster movement to prevent heat buildup. If you stay still too long with the diode laser, it just melts.

People assume the lower wattage means slower speeds are fine. The reality is that a 5-watt diode and a 20-watt diode concentrate heat very differently. The xtool s1 20 watt module has a small, intense spot—stay in one place, and it's a blowtorch.

Why my first pass was a disaster

I started at 10mm/s, 100%, 2 passes. The first pass looked promising—a clean line. The second pass? The acrylic started bubbling around the cut. On the third piece, the kerf filled with molten plastic and the laser head dragged through a puddle. That's when I realized the surface illusion: the lower power didn't mean the xtool s1 was gentler; it meant the heat had less time to spread before it was gone. I needed to move faster, not slower.

A friend in the industry once told me, "5 minutes of verification beats 5 days of correction." After ruining $120 of material in 15 minutes, I created a small test grid. I cut a series of 2-inch squares with different settings. The 15mm/s, 3-pass combo was the only one that gave me a consistent cut without the backside frosting over. The 40W module (which we didn't have on hand) would probably cut it in 2 passes, but I couldn't test that.

Setting up the xtool s1 for acrylic: It's not just speed

Honestly, the software setup is just as critical. In LightBurn, I had to enable the "Overcut" option for the acrylic, or the corners would be rounded. I also set the laser mode to "Constant Power" instead of "S-Power" to keep the beam steady during the cut. This is counterintuitive: you'd think a pulsed mode would reduce heat. But on the xtool s1, S-Power can cause inconsistent burns on clear acrylic.

If I remember correctly, the official Xtool guide recommends 25mm/s for 3mm acrylic. That worked for engraving, but not cutting. The engraving settings are fine for vector scoring, but for a full through-cut, you need to be more aggressive with power and slower (but not too slow) with speed.

The air assist is non-negotiable

I cannot stress this enough: running acrylic on the xtool s1 without air assist is a fire hazard. The focused heat of the 20W module on clear material can ignite the vapor if there's no airflow. Our setup has a small compressor running 15 PSI straight into the nozzle. Without it, my first test piece charred around the edges. With it, the edge was clean enough that the client didn't need any post-processing.

We paid $80 extra for the compressor—on top of the $150 for the air assist system—but that saved the $600 project. The client's alternative was no signage at all, which would have cost them their booth placement at the expo. Looking back, I should have tested the xtool s1 acrylic cutting settings a week before the rush job. But given what I knew then—that we had a working CO2 laser—my choice was reasonable. The CO2 laser broke, and we learned.

What the xtool s1 can't handle

Here's the honest truth: you should not use the xtool s1 20 watt for anything thicker than 6mm acrylic. It will technically cut it, but the edge quality degrades fast. For thick pieces, you need a 40W or 60W CO2 tube. The xtool s1 is a desktop machine; its power output (20 watts optical, not electrical) is designed for light industrial and hobbyist use. It is not an industrial laser cutter. If you need thick, production-ready cuts, get a bigger machine.

Also, forget about cutting clear acrylic without a honeycomb bed. The xtool s1's standard honeycomb is fine, but if you try cutting clear acrylic on the solid metal bed, the reflected laser beam will burn the bottom side of your material. We learned that the hard way. The bottom of our first test piece looked like it had been dragged across a hot stove.

My final checklist for acrylic on xtool s1

I created this checklist after that rush order and now keep it taped to the machine:

• Material: Is it cast or extruded? Use cast for better edge finish.
• Thickness: 3mm max for single-pass if you want speed, but I recommend 3 passes at 15mm/s.
• Air assist: On and at least 10 PSI.
• LightBurn setting: Constant Power, Overcut enabled, Scan Gap 0.08mm for fine lines.
• Test first: Always cut a 2" square on the scrap edge before cutting the final piece.

The third time we messed up a rush job on clear acrylic, I finally created this checklist. Should have done it after the first one. But that's how we learn, I guess.

Note on the 40W module: I haven't personally tested the xtool s1 40 watt on acrylic, but based on the power curve, I'd estimate it cuts 3mm in 2 passes at 20mm/s. Don't hold me to that.