How Many Passes Does It Take to Cut 6 mm Plywood?
Cutting 6 mm plywood usually takes 1 pass on a 60–100 W CO2, 1–2 slower passes on a 40 W CO2, roughly 4–10 passes on a 20 W diode and often 8 or more on a 10 W diode, if it cuts at all. These are typical numbers. Test on scrap, keep the sheet still and refocus if your machine allows it.
You went from 3 mm plywood, which cuts like butter, to 6 mm, and suddenly the laser takes forever, the smoke thickens and the cut still does not go through. Welcome to the surprise of thick material: doubling thickness takes much more than double the work.
For 6 mm plywood, the number of passes depends mostly on laser power. A strong CO2 does it in one pass, a 20 W diode needs several, and a 10 W diode is at its limit.
Typical passes for 6 mm plywood
These are common starting ranges with air assist on and a good focus. Plywood quality has a big effect, so test on scrap.
| Laser | Typical speed (mm/s) | Power | Passes for 6 mm | Comment |
|---|---|---|---|---|
| Diode 10 W optical | 1–3 | 100% | 8–15, or not recommended | Heavy char, high fire risk |
| Diode 20 W optical | 2–5 | 100% | 4–10 | Possible with patience |
| CO2 40 W | 3–7 | 80–100% | 1–2 | Slow, use air assist |
| CO2 60 W | 5–12 | 70–95% | 1 | Comfortable |
| CO2 80–100 W | 10–20 | 70–90% | 1 | Fast and clean |
Why 6 mm is so much harder
- The beam has to burn through twice the wood, and also clear a deeper, narrow slot where smoke gets stuck.
- The beam is a cone, so deeper cuts mean the focus is right only at one depth.
- Plywood layers of glue add hard spots.
- Slow speeds create heat that chars the top, so quality drops.
| Thickness | Relative cutting effort (very roughly) |
|---|---|
| 3 mm | 1x |
| 4 mm | 1.5–2x |
| 6 mm | 3–5x |
| 8–10 mm | 6–12x, CO2 strongly advised |
A worked example
You have a 20 W diode and want to cut a box panel in 6 mm plywood. Start with 3 mm/s at 100% power, air assist on, focus on the top surface. After 6 passes the panel is still attached at spots, so you add 3 more at the same settings. It drops out, but the edge is brown and tapered. Total time: roughly 9 times the length of the path. For a box, a 3 or 4 mm sheet would have been far faster, and you could use the finger joint box generator with a thinner setting.
Pro tip: If your machine supports it, lower the Z axis 0.5 mm after every two passes. This keeps the beam focused on the new bottom of the cut.
Tips for multiple passes
- Never move the material. Use clamps, pins or magnets, and do not open the lid during the job if you can avoid it.
- Do not let the head lose position. Use the same origin for all passes (LightBurn passes are done in order on the same path).
- Use air assist, and watch the cut for flames.
- Cut a small test shape first, for example a 20 mm square, to check how many passes are really needed.
- Plan for taper: parts cut from 6 mm are slightly larger at the top. Check how to measure kerf if fit matters.
Common mistake: Leaving a multi-pass job unattended. Several slow passes build heat in the cut, and a smouldering line can flare up on pass six. Stay with the machine.
Alternatives to cutting thick plywood
If your laser struggles, consider using two 3 mm layers glued together, buying 4 mm plywood, or sending thick parts to a local shop with a stronger CO2 machine. See laser cutting plywood for types and thickness, and why a laser is not cutting through if something fails.
Questions and answers
Can a 10 W diode cut 6 mm plywood?
Sometimes, with many slow passes on good material, but results are often poor: heavy charring, a tapered kerf and a high fire risk. A 20 W or CO2 laser is far better for 6 mm.
Should I refocus between passes?
If your machine lets you, lowering the focus by about 0.5–1 mm per pass or two helps on thick wood. If not, keep the same focus and slow down.
Is it better to use more passes or a slower speed?
On diodes, several faster passes often burn cleaner. On CO2, one slower pass is usually best until the speed gets so low that it chars.
Why is the edge tapered or burnt on 6 mm?
The beam is cone-shaped, so the kerf is narrower at the bottom. Slow speeds add heat, which also chars the top edge. Air assist and good focus reduce it.
Does 6 mm plywood cut differently from 3 mm?
It takes much more than twice the energy, because the beam has to clear a deeper kerf and the plywood has more glue layers. Expect roughly 3–5 times the time.
What about 6 mm MDF?
MDF cuts a bit differently, with more smoke and a very dark edge. Number of passes is similar, but check ventilation. See [laser cutting MDF](/learn/laser-cutting-mdf).