How thick can a laser cut?

Why one number is never the answer

1. One pass or ten? The same 20 W AtomStack lists 9 mm of basswood in one pass at 100 mm/min, and 10 mm in ten passes at 700 mm/min. A thickness without a pass count tells you little.
2. Which wood? Light woods like paulownia and balsa cut far deeper than birch plywood or hardwood. xTool’s 20 W test cut 8 mm solid wood in one pass, but needed 2–3 passes for beech, cherry and bamboo.
3. Table or brochure? Settings tables come with a speed and power; headline claims often do not. AtomStack’s A70 Max page says 25–28 mm of wood in one pass, while its own settings table gives 15 mm of basswood in one pass.
4. Which colour of acrylic? Blue diode light passes through clear acrylic, and white and some blue sheets are hard to cut. See diode vs CO2 vs fiber.
5. Which watts? The numbers here are the makers’ optical output. Some older listings put electrical input in the name; check the real laser power table before comparing.

Why the cut stops

A laser cuts by focusing light into a tiny spot. Above and below that spot the beam widens, so the same power is spread over a bigger area. Near the top of the sheet the beam is narrow and burns fast; deeper down it is wider, so each millimetre takes more energy. Eventually the light at the bottom of the cut is too spread out to burn, and the energy goes into the walls as char instead. That is why extra passes give less and less, and why a ramp test to find the true focus is worth doing — use our focus and ramp test generator.

Plywood adds glue layers that resist the beam, and some glues are not laser-safe at all (see what not to laser cut). Air assist blows smoke and flame out of the cut so the beam reaches the bottom. Some maker figures say they used it — Sculpfun’s 20 mm one-pass plywood figure for the S40 Max is with its 50 L/min air pump — and many do not say either way.

The math behind the simulator

The first line is exact. The second is the shape of a focused Gaussian beam (d₀ = spot at focus, z_f = focus depth, z_R = the range over which it stays near focus). The third is our teaching model: the absorption a, the threshold E_th, the focus range (2.5 mm for diodes, 3 mm for CO2) and the 25 % harder glue lines are assumed values, tuned so that results fall inside the maker figures above. Use the published figures, not the model, when choosing a machine, and a test cut on scrap when choosing settings.

Choosing a machine for thick cuts

If you mostly cut 3–6 mm plywood, the one-pass figures say a 10–20 W diode is enough. For 10 mm and up in one pass, the tables point to 40 W class diodes or a CO2 laser, and only a CO2 laser cuts clear acrylic. Compare optical output, spot size and work area in our machine list, or by brand: AtomStack (whose settings table supplies many of the figures here), TwoTrees and Sculpfun. To move settings from one machine to another, use the power and speed converter, and to size joints for the sheet you cut, the kerf calculator.

FAQ

How thick can a 10W laser cut?

In makers’ own figures, 10–15 W diode lasers cut about 8 mm of wood in one pass: TwoTrees lists 8 mm plywood at 150 mm/min for its 10 W TS3, and Sculpfun lists 8 mm for the 12 W E1 and the 14 W C2. One-pass figures for dark acrylic are 3–5 mm. More passes go further but slowly — AtomStack’s table needs 10 passes for 10 mm acrylic on the 10 W A10 Pro V2. A blue diode cannot cut clear acrylic at any power.

How thick can a 20W laser cut?

Maker settings tables for 20–24 W diodes give 6–12 mm of basswood in one pass (xTool’s support article: 10 mm basswood plywood on the D1 Pro 20 W). Product pages claim up to 20 mm, usually without a pass count or speed. Acrylic is 4.5–5 mm in one pass in the tables (10 mm for the 24 W A24 Pro); the tables do not give a colour, but a diode needs a dark one.

How thick can a 40W laser cut?

One-pass wood figures for 40–48 W diodes run from 11 mm (AtomStack’s settings table for the A40 Pro V2) and 15 mm (Creality’s parameter table for the Falcon2 40W) up to 18–30 mm on product pages. Acrylic is 4.6–5 mm in one pass in the tables and up to 30 mm in one product claim. A 55 W CO2 laser is listed at 15–18 mm of basswood and 20 mm of acrylic in one pass.

Why won’t my laser cut through, even with more passes?

Usually because the beam is no longer focused at the bottom of the cut. A focused beam widens above and below its focus, so deeper in the cut the same power is spread over a wider spot and stops burning; each extra pass adds less depth and more char. Glue layers in plywood, the wrong acrylic colour for a diode, missing air assist and a lens or window covered in soot also stop a cut. Check focus with a ramp test, use air assist, and try lowering the focus a little into thick stock.

Sources

• AtomStack, Material settings (LightBurn rows; speed in mm/min). For the A10 Pro V2 we left out the basswood and pine rows whose pass counts differ between the LightBurn and LaserGRBL tables. The A20 Pro V2’s LaserGRBL basswood rows (12 and 17 mm) repeat the A24 Pro’s values, so we treated them as a copying error and kept the LightBurn rows.
• TwoTrees, Laser engraver material test list (TTS-55 and TS3 columns).
• Creality, Falcon2 engraving and cutting parameter settings.
• xTool support, Choosing a 10W, 20W or 40W laser module, and the product articles linked from each dot.
• Sculpfun, LaserPecker, Glowforge, Bambu Lab and TwoTrees product pages, linked from each dot.
• Laser types and acrylic colours: the sources on our diode vs CO2 vs fiber page.

Last checked 2026-11-01 · Maker figures and a teaching model; no machine was tested to make this page.