LaserCanvas
Plywood and MDF: choosing and cutting sheet wood
Buy laser ply — birch or poplar with a uniform, light-coloured glue and no voids. Construction and exterior plywood use dark or waterproof glues that resist the beam, so the cut stalls at the glue line. MDF cuts very evenly but smells strongly and produces fine dust that clogs extraction.
Not all plywood is laserable
Plywood is thin veneers glued in alternating grain directions. The wood cuts predictably; the glue is what decides whether the sheet works. Interior-grade urea glue is light and cuts with the wood. Exterior and marine glues are formulated to resist heat and moisture, which is exactly the wrong property here.
| Type | Cuts? | Notes |
|---|---|---|
| Laser ply (birch/poplar) | Yes, cleanly | Sold specifically for this. Uniform glue, void-free, consistent thickness |
| Interior birch ply | Usually | Variable. Check for voids; may have the odd dark glue line |
| Exterior / marine ply | Poorly | Waterproof glue resists the beam; cuts stall mid-thickness |
| Construction ply | No, in practice | Voids, knots and mixed glue. One sheet cuts, the next does not |
| MDF | Yes, very evenly | No grain or glue lines, so the most consistent cut of all — but see below |
MDF: even, smelly, dusty
MDF is wood fibre and resin pressed into a board. Because it has no grain and no glue lines, it cuts with unusual consistency — the same settings work everywhere on the sheet, which plywood cannot promise.
The costs are real, though. MDF contains urea-formaldehyde resin, and cutting it releases formaldehyde along with a strong, persistent smell. It also produces very fine dust that coats the inside of the machine and clogs filters faster than wood does.
- Use MDF only with extraction that actually vents outside, not a recirculating filter.
- Expect to clean the machine more often, and the lens especially.
- The cut edge is fuzzy and soaks up finish unevenly — seal it before painting.
Settings, as a starting point
These are places to begin a test grid, not answers. Machines differ by more than the numbers below.
| Material | Diode (~10 W optical) | CO2 (~50 W) |
|---|---|---|
| 3 mm laser ply — cut | 100% power, 200–350 mm/min, 2–4 passes | 60–70%, 900–1200 mm/min, 1 pass |
| 3 mm MDF — cut | 100%, 180–300 mm/min, 3–4 passes | 65–75%, 800–1000 mm/min, 1 pass |
| Engrave, either | 15–30%, 2500–4000 mm/min | 15–25%, 3000–6000 mm/min |
Getting a cleaner edge
- Multiple fast passes beat one slow pass. Less heat accumulates, so less charring, and each pass clears debris for the next.
- Air assist blows smoke out of the kerf and keeps flame off the surface. It is the single biggest improvement to edge quality on wood.
- Masking tape on the surface takes the smoke staining instead of the wood. Peel it after cutting.
- Raise the work on pins or a honeycomb so the beam is not reflecting off the bed back into the underside.
Common questions
Why does my plywood cut through in some places but not others?
Usually voids or glue lines. Cheaper plywood has internal gaps and patches of darker, more heat-resistant glue, and the beam behaves differently at each. Laser ply is manufactured to avoid both, which is what you are paying for. If it fails uniformly rather than in patches, that is focus or power instead.
Is MDF safe to laser cut?
It is cuttable, and the fumes need respecting. MDF is bound with urea-formaldehyde resin and cutting it releases formaldehyde plus very fine dust. With extraction ducted outside and the lid closed it is routine; with a recirculating filter in a small room it is not a good idea.
What thickness of plywood can a diode laser cut?
Around 3 mm reliably with multiple passes on a 10 W optical diode, and 5–6 mm slowly and with a rough edge. Beyond that the kerf chars faster than it deepens. A 50 W CO2 handles 6 mm comfortably and 9–10 mm with care.
How do I stop the edges coming out black?
Air assist first — it clears the smoke that does the staining. Then masking tape on both faces, more passes at higher speed rather than fewer slow ones, and keeping the lens clean. Some darkening on the cut edge itself is inherent to burning through wood.