Laser-cutting Plywood: What Thickness Can Your Laser Handle?

The short answer

For laser-cutting 3 mm birch plywood, you'll need at least 20 W of optical power with a diode laser, or 30 W with a CO₂ laser. For 6 mm birch, that's 50 W diode or 60 W CO₂. For the thickest sheet, 9 mm birch, you'll cut it with a CO₂ laser from 80 W. You can't cut wood with a fibre laser.

But wattage is only half the story. The wood type, the adhesive, and the flatness of the sheet are just as important. So, two 6 mm sheets can cut very differently on the same machine.

We've been laser-cutting daily for 12 years ourselves, through our sister company Snijlab, and test all our plywood on our own diode and CO₂ lasers. In this blog, you'll find out which thickness suits your laser, why, and how to get clean cuts through thicker sheets.

Laser-cutting Triply and Plywood: Why it Cuts Differently from Solid Wood

Triply consists of three thin wood layers, plywood of more than three. In practice, the terms are used interchangeably. The layers are glued cross-wise, making the sheet strong in all directions and less prone to splitting than solid wood. For your laser, this construction means three things.

1. Each adhesive layer requires extra energy. Wood vaporises easily under the laser beam, but adhesive much less so. A thicker sheet has more adhesive layers, so a sheet that's twice as thick will cost your laser more than twice the effort.
2. The adhesive determines what your cut edge looks like. DIY store plywood and aircraft-grade triply are usually bonded with waterproof exterior adhesive (WBP). This cuts slowly and leaves a black edge that will smudge your hands. Laser-ready plywood is interior-bonded: with an adhesive that vaporises cleanly, leaving a honey-brown edge. This adhesive is intended for indoor use, not outdoor.
3. Knots block the laser. A knot is a hard, resin-rich spot in the wood where the beam often doesn't get through in one pass. A thicker sheet has more layers and thus a greater chance of a knot appearing exactly on your cut line. That's why we select plywood with as few knots and voids in the inner layers as possible.

Plywood Thickness per Laser Type: Minimum Power

This table shows you the minimum power you need per thickness to cut through the sheet in a single pass at 8 mm/s. This is the slowest speed at which the edge still remains clean. The values come from our own cutting settings.

Got less power? Then you can cut slower or make a second pass. That works, but the edge chars more and the risk of flames increases. 

Bamboo requires a bit more power than birch for the same thickness: it's denser and harder. Also, note the diode column: a diode of 50 W optical power or more is rare. In practice, 6 mm birch and 5 mm bamboo are jobs for a CO₂ laser, and 9 mm birch is too thick for any diode.

How much power does your diode laser really have?

Manufacturers often state the electrical power in the product name. What comes out of the laser head, the optical power, is usually much lower: a “40 W” diode often only delivers 5 to 10 W optical. So, check the specifications before you use the table. You'll find which sheets are suitable for your machine under materials for diode lasers.

Why does a CO₂ laser cut so much deeper?

Wood absorbs light from both well: the infrared of a CO₂ laser (10.6 µm) and the blue light of a diode (around 450 nm). The difference lies in the power. A CO₂ tube quickly delivers 40 to 100 W, a diode usually 5 to 20 W. A fibre laser (1064 nm) is made for metal and marking; wood chars under it, but you can't cut plywood with it. If you're working with a CO₂ laser, check out all materials for CO₂ lasers.

Can you laser-cut 18 mm plywood?

18 mm is the most popular thickness at DIY stores, but it's too thick for almost any laser cutter. A heavy-duty CO₂ laser of 150 W or more can sometimes get through it, with a slanted cut and a heavily charred edge. For thick parts, you're better off milling, or gluing thinner sheets together.

Which plywood suits your laser?

The denser and harder the wood, the more energy your laser needs per millimetre. Birch and bamboo are both strong and quite dense, but they each cut in their own way.

Birch plywood: strong, with a clear grain

Birch plywood is hard and strong, with a light colour and a clear wood grain. We supply it as thin triply in 0.5, 1, and 2 mm and as plywood up to 9 mm, in two variants.

European birch is the strongest and FSC®-certified in 3 and 6 mm. Due to internal stress, a sheet often warps. Asian birch is flatter and more affordable, but breaks a little faster.

If you're looking for maximum strength, choose European birch. If you're cutting 4 mm or thicker and are close to the minimum power from the table, the flatness of Asian birch helps: the focus remains constant across the entire sheet.

Bamboo plywood: even and strong per millimetre

Bamboo plywood is 100% FSC®-certified and available from 0.5 to 5 mm. Bamboo is dense, but the thin, cross-bonded layers make the sheet even and free of knots. This allows your laser to cut through it uniformly, without areas where it gets stuck.

In 3 and 5 mm, bamboo is stronger than wood plywood of the same thickness. So you can often choose a thinner sheet, and that saves cutting time. You can read more about this in What's so Special About Bamboo as Plywood?

All our plywood is interior-bonded with laser-ready adhesive and tested on our own machines. You can see if a sheet is suitable for diode or CO₂ by the LaserGrade icon on each product.

Laser-Cutting Thicker Plywood: How to Get the Most Out of Your Machine

Are you pushing your laser's limits? With these six points, you'll get a clean cut instead of parts you have to break out:

1. Start with the right sheet. Never test your limits with DIY store plywood: because the exterior adhesive makes it cut slower and gives you black edges. Then it seems like your laser can't handle it, when it's actually the sheet.

2. Use a flat sheet. A warped sheet lies a few millimetres higher in places. With thick wood, the focus falls outside the material there, and you won't cut through. Also read Where Can I Find Flat Wood for Laser Cutting?

3. Place the focus inside the material. A laser beam is shaped like an hourglass. For 3 mm, that doesn't matter much, but from 6 mm, you'll cut straighter and further through if the focal point is 1 to 2 mm below the surface.

4. Turn on air assist. An airflow blows smoke and vaporised material out of the kerf, cools the edge, and prevents flames. Without air assist, you won't achieve the values in the table.

5. Allow smoke to escape from the bottom. Place the sheet on a honeycomb bed or on support points. This prevents soot stains and flashback on the reverse side.

6. Find your setting with a test cut. Cut a small square and gradually reduce the speed until it drops out on its own. Note down the setting per wood type and thickness. You can read how to do that in How to Find the Perfect Setting for Your Laser?

A second pass can finish a cut, but each extra pass further chars the edge and increases the fire risk. If you consistently need multiple passes, it's better to choose a thinner sheet.

Safety with Thick Wood

Always stay with your laser when cutting thick wood. The slower the laser moves, the greater the chance of the wood catching fire. Keep the extraction on and make sure you can stop the machine immediately.

Frequently Asked Questions about Laser-Cutting Wood

How thick of plywood can a 10 W diode laser cut?

With 10 W optical power, you'll cut 0.5 and 1 mm birch and 0.5 mm bamboo cleanly at 8 mm/s. For 2 mm, you need 15 W, and for 3 mm, 20 W. With 10 W, you can also get through it if you cut slower or make two passes, but the edge will char more heavily.

Can a diode laser cut plywood?

Yes. Wood absorbs the blue light from a diode laser well, as long as the plywood is interior-bonded. At Lasersheets, you can see which sheets are suitable by the LaserGrade Diode icon.

What is the maximum thickness for laser-cutting wood?

That depends on your power and the wood type. In our range, 9 mm birch plywood is the thickest sheet; for that, you'll need at least an 80 W CO₂ laser. DIY store 18 mm plywood is too thick for almost any laser cutter.

What's the difference between triply and plywood?

Triply consists of three wood layers, plywood of more than three. For laser cutting, the adhesive is more important than the name: choose triply or plywood that is interior-bonded.

Why does my plywood cut edge turn black?

Usually due to exterior adhesive (WBP) in DIY store plywood or aircraft-grade triply, or by cutting too slowly without air assist. Interior-bonded plywood gives a honey-brown edge that won't smudge.

Can a fibre laser cut wood?

No. A fibre laser is made for metal and marking. The wood chars on the surface, but you can't cut plywood with it.

Which plywood thickness is most commonly used for laser cutting?

3 mm. It cuts on any CO₂ laser from 30 W and on diode lasers from 20 W optical, is sturdy enough for enclosures, models, and boxes, and fits most design files with finger joints.

Choose the Sheet That Suits Your Laser

How thick you can cut depends just as much on the sheet as on your laser. With a diode laser of 10 to 20 W optical, you're good up to 2-3 mm. With a CO₂ laser from 60 W, you'll also cut 6 mm birch and 5 mm bamboo, and 9 mm birch requires 80 W. DIY store plywood won't achieve those results, due to the adhesive and knots.

In our collection of triply and thin plywood, you'll find birch and bamboo plywood from 0.5 to 9 mm, in sizes that fit your machine and from just 1 sheet. Unsure which thickness your laser can handle? Test it yourself with the Material Sample kit.

Further Reading

• How to Find the Perfect Setting for Your Laser?

• Where Can I Find Flat Wood for Laser Cutting?

• What's so Special About Bamboo as Plywood?