Materials, Thickness and What a Laser Can Cut
Which materials cut, engrave or must never be lasered, an energy-balance estimate of cutting speed, and power against thickness.
Which materials, and how
| Material | CO₂ laser | Diode / fiber | Notes |
|---|---|---|---|
| Solid wood, plywood (thin) | Cuts and engraves well | Diode cuts thin; engraves well | Charred edge; glue in plywood can slow or flare; check the glue (see below) |
| MDF and chipboard | Cuts, with heavy smoke and char | Slow | Binder gives formaldehyde and a dirty edge; wear on optics; extract well |
| Cast acrylic | Cuts to a clear flame-polished edge; engraves frosted | Clear: passes through; dark: cuts slowly | The best plastic for lasers |
| Extruded acrylic | Cuts well; engraves less white | As above | Cheaper; more stress cracking |
| Leather (vegetable tanned) | Cuts and engraves, strong smell | Diode engraves; fiber no | Chrome-tanned leather can give off toxic chromium compounds: avoid |
| Paper, card, cardboard | Cuts with little power | Diode cuts thin | Fire risk: air assist and low power |
| Fabric | Natural fibers cut and seal; synthetics melt a sealed edge | Slow | Cotton, felt, polyester, nylon (not coated or vinyl) usually fine |
| Rubber and foam | Some cut (EVA foam, laser rubber); many do not | Slow | Polyurethane foam gives toxic fumes and burns fast: avoid |
| Glass and ceramic | Engraves (frosts); does not cut | Diode and fiber: no | Thermal stress can crack large pieces |
| Stone, slate, tile | Engraves | Diode engraves dark stone | Dust; light-colored stone marks poorly |
| Bare metals | Does not cut or mark | Fiber cuts and marks; diode marks coated metal only | See the metals section |
| Coated and anodized metal | Removes the coating: engraves | Fiber and diode mark | Used for plates and labels |
Materials never to laser
Some materials give off gases that are toxic, corrosive or explosive, or burn uncontrollably. If you cannot identify a material, do not cut it. Use stock sold as laser-safe, keep the supplier’s safety data sheet, and when in doubt ask the supplier or the machine maker.
| Material | What goes wrong |
|---|---|
| PVC, vinyl, imitation leather, anything with chlorine | Releases hydrochloric acid and chlorine, which are toxic and corrode the machine, its optics and the extraction |
| Polycarbonate (PC) and Lexan | Absorbs poorly, burns and discolors, gives off toxic fumes; a sooty, brown edge |
| ABS and polystyrene | Melts and burns with a smoky flame; ABS can release hydrogen cyanide |
| Polyoxymethylene (Delrin, acetal) | Gives off formaldehyde |
| Polyurethane foam and some rubbers | Burns fast, giving isocyanates and cyanide-containing smoke |
| Fiberglass, carbon fiber and coated or resin composites | Toxic and irritant fumes and dust, and the fibers damage the extraction |
| Chrome-tanned leather, treated wood with arsenic or copper salts | Toxic metal compounds in the fume |
| Materials with halogenated flame retardants or PTFE (Teflon) | Releases fluorine or bromine compounds |
| Beryllium copper, lead and unknown metals | Toxic fume and dust |
| Anything of unknown composition | Cannot be judged |
The protection against fumes is in Laser Safety, Fire and Fumes and Workshop Safety: extraction does not make a forbidden material safe.
An energy-balance model of cutting speed
A cut removes a strip of material of width equal to the kerf and depth equal to the thickness. The beam must supply the energy to heat that volume to its cutting temperature and to melt or vaporize it. A simple balance gives an upper bound on the cutting speed:
Ev = ρ (c ΔT + L) v ≈ η P ÷ (Ev × kerf × thickness)
where Ev is the energy per cubic millimeter, ρ the density in g/mm³, c the specific heat, ΔT the temperature rise, L the latent heat or effective decomposition heat in J/g, P the laser power and η the fraction of the power that goes into the cut (absorption and thermal losses). Real cuts are slower; the model shows the pattern.
Worked example: 60 W CO₂ in 3 mm sheet, 0.2 mm kerf, η = 0.6 (illustrative data)
| Material | Density | Energy per mm³ | Upper-bound speed | Realistic (about half) |
|---|---|---|---|---|
| Basswood plywood | 0.55 g/cm³ | 1.11 J/mm³ | 54 mm/s | 27 mm/s |
| Cast acrylic (PMMA) | 1.18 g/cm³ | 1.84 J/mm³ | 33 mm/s | 16 mm/s |
| Leather (vegetable tanned) | 0.95 g/cm³ | 1.84 J/mm³ | 33 mm/s | 16 mm/s |
| Cardboard | 0.70 g/cm³ | 1.09 J/mm³ | 55 mm/s | 28 mm/s |
| Felt and fabric | 0.30 g/cm³ | 0.44 J/mm³ | 138 mm/s | 69 mm/s |
- The order is what matters: card and felt cut fastest, wood next, then leather and acrylic. Acrylic is slower than its low density suggests because it must be vaporized, not charred.
- Speed falls in proportion to thickness. For a constant power, double the thickness takes half the speed: an acrylic cut at 15 mm/s in 3 mm sheet runs at about 7.5 mm/s in 6 mm. (See the table below.)
- Power for a target speed. To cut 6 mm acrylic at 15 mm/s with a 0.25 mm kerf: P = v Ev × kerf × thickness ÷ η = 15 × 1.84 × 0.25 × 6 ÷ 0.6 = 69 W (before allowing for the real speed being lower): a 60 W laser would be slow, a 100 W laser comfortable.
| Sheet thickness | Speed (proportional model, 40 mm/s in 1.5 mm) | Time for a 100 mm cut |
|---|---|---|
| 1.5 mm | 40 mm/s | 150 s per 100 mm |
| 3.0 mm | 20 mm/s | 300 s per 100 mm |
| 6.0 mm | 10 mm/s | 600 s per 100 mm |
| 10.0 mm | 6 mm/s | 1 000 s per 100 mm |
Cutting time is length divided by speed: a 600 mm outline in 3 mm acrylic at the realistic speed of 16 mm/s takes 37 s; in 6 mm sheet at 8 mm/s it takes 74 s (twice as long). Add the time for the head’s acceleration at corners and the travel between cuts (see Files, Software and Toolpaths).
Metals and the fiber laser
Metals melt at a high temperature, conduct heat quickly and (at first) reflect much of the light, so the absorbed fraction η is small. The same energy balance applies, with the melting temperature and latent heat of fusion, but the melt is blown out by a gas jet rather than vaporized.
Worked example: 1 kW fiber laser on 1 mm sheet, kerf 0.15 mm
- Mild steel (density 7.85 g/cm³, c ≈ 0.5 J/g·K, heated by 1 480 K to melting, latent heat 270 J/g): Ev = 0.00785 × (0.5 × 1 480 + 270) = 7.9 J/mm³. With η = 0.35 (absorbed, effective fraction): v = 0.35 × 1 000 ÷ (7.9 × 0.15 × 1) = 294 mm/s = 17.7 m/min.
- With oxygen the iron burns and adds heat, which can raise the speed by about 40 %: 24.7 m/min. Real machines reach about 8 to 12 m/min for 1 mm mild steel at 1 kW, so the model is an upper bound within a factor of two.
- Aluminum (ρ = 2.70 g/cm³, melting at 640 °C, latent heat 397 J/g): Ev = 2.6 J/mm³ but η is only 0.08 because it reflects most of the light and conducts heat away: 12.2 m/min. Aluminum needs nitrogen and more power than the energy alone suggests.
- Copper and brass reflect and conduct so well (η ≈ 0.08) that 5.8 m/min is an upper bound at 1 kW: they are difficult to cut and need a high-power, well-focused fiber laser and pierce carefully, because of reflection into the machine (see Industrial Laser Cutting: Metals, Gas and Process).
Power against thickness
The maximum thickness a laser can cut cleanly rises with power, but slowly, because the energy per millimeter rises with thickness and the beam has to stay in focus and keep the melt flowing through a long, narrow kerf. The ranges below are typical values for good-quality cuts; the limit for a rough cut is thicker.
| Machine | Wood / plywood | Cast acrylic | Mild steel (O₂) | Stainless (N₂) | Aluminum (N₂) |
|---|---|---|---|---|---|
| Blue diode 10 W | to 3 mm (slow) | dark only, 2 mm | – | – | – |
| CO₂ 40 W | to 5 mm | to 6 mm | – | – | – |
| CO₂ 100 W | to 12 mm | to 15 mm | – | – | – |
| Fiber 1 kW | – | – | to 6 mm | to 4 mm | to 3 mm |
| Fiber 3 kW | – | – | to 15 mm | to 10 mm | to 8 mm |
| Fiber 6 kW | – | – | to 25 mm | to 16 mm | to 15 mm |
| Fiber 12 kW and over | – | – | to 40 mm and more | to 30 mm | to 25 mm |
The maximum depends on gas, lens, nozzle and the quality accepted; see Industrial Laser Cutting for the metal cutting process.
Wood, plywood and MDF
- Wood chars: the cut edge is brown to black. Fast speed, less power and air assist reduce it; masking tape on the top surface keeps the face clean; sanding or a wipe with a damp cloth removes soot.
- Resin and knots in softwood make cuts uneven and flare. Hardwood plywood with a uniform core cuts best; poor plywood has voids and glue pockets where the beam does not cut through (the “laser-grade” boards are made for it).
- Glue matters: plywood adhesives (urea-formaldehyde or phenolic) add about 8 % of the mass in the sheet. Phenolic glue is harder to cut; formaldehyde is released in the fume.
- MDF cuts with heavy smoke and a dark edge; the dust and fume clog the extraction and the optics. It is cheap but needs the best extraction.
- Moisture and warp: a bowed board changes the focus across the bed (see Power, Speed, Focus and Assist Gas); store flat and dry.
- Fire risk: thin wood and especially thin offcuts flare. Keep the bed clear, watch every cut, and keep the air assist on.
Acrylic and plastics
- Cast acrylic cuts with a flame-polished edge and engraves white and frosted. Extruded acrylic cuts well too, engraves less white and cracks more at engraved lines.
- Leave the protective film on (paper is best; a polyethylene film also burns but may leave residue) to keep the face clean, and cut with the film on the face up.
- Acrylic burns with a bright flame and drips: watch it, air assist on, and never leave the machine.
- The fumes of cutting acrylic include the monomer methyl methacrylate, an irritant with a strong smell; extract them.
- Other plastics that are generally acceptable: polyester (PET, Mylar), polyimide (Kapton), nylon (thin), laser-grade engraving plastics, and some acrylic-like sheets. Read the supplier’s data sheet. Not PVC, polycarbonate, ABS, acetal or polystyrene (see above).
Leather, paper, fabric, foam, glass and stone
| Material | Notes |
|---|---|
| Leather | Cuts at low power with a brown edge; engraves dark. Choose vegetable-tanned leather; avoid chrome-tanned or coated leather and imitation leather (PVC) |
| Paper and card | Very low power, high speed and air assist; they flare easily. Good for stencils, models and packaging prototypes |
| Fabric | Natural fibers cut and the edge can char; synthetics seal the edge as they cut. Hold flat with a light vacuum or weights |
| Foam | Closed-cell EVA and polyethylene foams may cut; polyurethane foam must not |
| Glass | A CO₂ laser frosts the surface (engraving). Cracks may start from heat: use low power, defocus slightly, and avoid thick or tempered glass |
| Stone and tile | Engraves dark or white; dust needs extraction |
| Cork and rubber | Natural cork cuts; rubber varies (laser-rated rubber stamp sheet is made for it) |
Buying and preparing sheet
- Buy laser-grade sheet where there is a choice: flat, uniform, with a known adhesive and no voids.
- Keep the data sheet of every material and note its batch.
- Test a scrap piece from each batch before a big job; the same nominal material differs between batches.
- Flatness: clamp or weight sheet on a honeycomb bed or pins; a bow of 1 mm changes the focus by about as much as the whole depth of focus of a short lens (see How Laser Cutting Works and Laser Types).
- Keep the bed and the honeycomb clean; residue is fuel (see Running a Laser Shop: Costs, Maintenance and Troubleshooting).
- Label offcuts, so that the next user knows what they are: an unidentified scrap is a hazard.
Related
- Laser Cutting: the overview of this guide.
- Power, Speed, Focus and Assist Gas: turning a material and thickness into settings.
- Laser Safety, Fire and Fumes: fumes, fire and forbidden materials.
- Industrial Laser Cutting: Metals, Gas and Process: cutting metals with a fiber laser.
- Workshop Safety: ventilation and fire precautions.
FAQ
Which materials can a laser cut?
A CO₂ laser cuts wood, acrylic, leather, paper, fabric and some foams; a fiber laser cuts metals. Never cut PVC, vinyl, polycarbonate, ABS, acetal, polyurethane foam, fiberglass or anything of unknown composition.
Why is acrylic slower to cut than wood of the same thickness?
It must be heated and vaporized cleanly, which takes more energy per cubic millimeter than charring wood, and a clean flame-polished edge needs a slower cut.
How does the cutting speed depend on thickness?
Roughly in inverse proportion: double the thickness at the same power needs half the speed. At some thickness the laser can no longer cut through at any useful speed.
Can I cut aluminum with my CO₂ laser?
Not usefully. Bare aluminum reflects the 10.6 µm light and conducts heat away. It can be engraved when anodized or coated. A fiber laser cuts it with nitrogen.
References
- Steen, W. M. and Mazumder, J., Laser Material Processing, Springer; Powell, J., CO₂ Laser Cutting, Springer.
- Laser makers’ material guides and approved-materials lists (for example Epilog, Trotec, Universal); the HSE guidance on laser processing hazards.
- Safety data sheets of the materials; the Health and Safety Executive and OSHA information on fumes from heated plastics.
Last reviewed: October 2026. Material properties and speeds are typical and illustrative: test on your own sheet.