LaserCanvas
CO2, diode, fibre and galvo: which laser does what
For cutting wood and acrylic, CO2 is the workhorse and diode is the affordable entry point that cannot cut clear acrylic at all. Fibre marks and cuts metal but is useless on organics. Galvo describes how the beam moves, not what it is — a fast mirror scanner, usually paired with a fibre source. The deciding factor is wavelength, not watts.
Wavelength decides what is possible; power decides how fast
This is the single most useful idea in the whole topic, and it explains nearly every surprising result people hit. A laser only does work when the material absorbs its wavelength. If the material is transparent at that wavelength, the beam passes straight through and nothing happens, no matter how many watts you throw at it.
That is why a 10 W diode will not touch clear acrylic while a 40 W CO2 cuts it like butter, and why a fibre laser that engraves stainless steel effortlessly does almost nothing useful to plywood. Wattage only becomes the question once absorption is established.
The four types
| Type | Wavelength | Good at | Cannot do |
|---|---|---|---|
| CO2 | 10,600 nm (far infrared) | Wood, acrylic, leather, paper, card, fabric, glass marking | Bare metal cutting; most metals reflect it |
| Blue diode | ~450–455 nm | Wood, dark and opaque acrylic, leather, card; marking coated metals | Clear and light acrylic — transparent at blue. Bare metal |
| IR diode | ~1,064 nm | Marking bare and coated metals, and many plastics — including some a blue diode cannot touch | Cutting. It is a marking module, and it chars wood rather than cutting it |
| Fibre | ~1,064 nm (near infrared) | Metal marking, engraving and cutting; some plastics | Wood, paper and most organics — poor absorption, and it chars rather than cuts |
| Galvo | Usually fibre, sometimes CO2 | Very fast marking over a small field | Not a wavelength at all — see below |
Why "galvo" is a different kind of word
CO2, diode and fibre describe the source — how the light is made, and therefore its wavelength. Galvo describes the delivery: instead of moving the head on rails, two galvanometer mirrors steer the beam, which is dramatically faster but limited to a small field set by the lens. A galvo machine still has a source, usually fibre. So "should I get a fibre or a galvo?" is not quite a question — most galvos are fibre.
What this means if you are choosing one
For the hobbyist work this site is about — boxes, signs, decorations, models, gifts — the realistic choice is between diode and CO2.
- Blue diode, from around 5 W optical on small machines up to 40 W and beyond on current ones — a long way from the 5 W units the category started with, and worth knowing if your reference points are a few years old. No chiller, no tube to replace. Still will not cut clear acrylic at any power.
- IR diode at 1,064 nm, increasingly offered as a second module on the same machine. It marks bare metal, which the blue one cannot, and marks plastics the blue one ignores. It does not cut — treat it as a marking head that shares your gantry, not an upgrade.
- CO2, roughly 40–100 W. Cuts faster and thicker, handles clear acrylic, gives a polished acrylic edge. Needs cooling, extraction and space, and the tube is a consumable with a life measured in thousands of hours.
- Fibre, if the work is metal. It is a different hobby, not an upgrade path from wood cutting.
Does the firmware depend on the laser type?
No, and this catches people out in a useful way. The controller firmware — GRBL, FluidNC, Marlin, Smoothie — is about moving the machine and switching the beam. It does not know or care what makes the light.
That is why the same software drives a cheap diode and a large CO2: both take G-code, both understand M3/M4 and a PWM power value. A GRBL diode machine and a GRBL CO2 machine differ in their settings, not in how you talk to them.
The surprises worth knowing in advance
- Clear acrylic on a diode does nothing. Not "cuts badly" — nothing. Blue light passes straight through it. Use cast acrylic in a dark colour, or a CO2.
- CO2 will not cut bare metal, but it marks coated and anodised metal well, because you are removing the coating rather than the metal.
- Fibre on wood chars and smells and does not give a clean edge. It is the wrong tool, not a weak one.
- Glass cannot be cut by any of these. CO2 frosts the surface, which is engraving, not cutting.
- Mirrors and polished metal are a hazard on a CO2, because they reflect the beam somewhere you did not intend.
Common questions
Can a diode laser cut clear acrylic?
No. Clear acrylic is effectively transparent at the ~450 nm blue wavelength a diode emits, so the energy passes through without being absorbed. More power does not help. Use dark or cast tinted acrylic, apply an absorbing coating, or use a CO2 laser.
Is a 40 W diode the same as a 40 W CO2?
No, even when both figures are genuine optical watts. The two emit at different wavelengths, and a material that absorbs one may be nearly transparent to the other — clear acrylic is the standard example, cut easily by CO2 and untouched by a diode. Equal power does not mean equal result, so the comparison only means something once you name the material.
Why do two lasers both described as "40 W" perform so differently?
Because the number may not be measuring the same thing. Some diode modules are rated by electrical input, so a "40 W" module can be around 10 W of actual optical output, while genuine 40 W optical diodes are also sold now. Look for the word optical, or for a stated cut result on a named material and thickness — the headline figure alone tells you nothing.
Can I cut metal with a CO2 laser?
Not at hobby power levels. Industrial metal cutting CO2 machines exist but run at kilowatts with assist gas. A hobby CO2 will mark coated or anodised metal, which is removing the coating rather than cutting the metal.
Which type is safest for a home workshop?
Neither is inherently safe, and enclosure matters more than type. An enclosed CO2 with interlocks and ducted extraction is safer than an open-frame diode sitting on a desk, even though the diode is lower power — an open frame puts scattered light in the room and vents smoke into it.