Laser power and speed: what wattage really changes
Wattage is the number everyone compares and the one that explains the least. A 40 W CO2 cuts faster than a 40 W diode because the beam is different; a 20 W fiber marks metal that a 40 W diode cannot touch. Power only means something inside one technology.
What wattage actually changes
More power means more energy per second at the same speed. In practice that buys you one of three things: thicker material, faster travel, or darker engraving. You cannot have all three at once.
Doubling the power does not double the cutting depth. Losses, focus and material all take a share, which is why the depth figures in listings rarely scale linearly.
Engraving versus cutting
Engraving removes a shallow layer; it needs enough energy to mark the surface, not to go through. A lower-power machine at a slower speed usually engraves better than a high-power machine at full speed, because the dot has more time to interact.
Cutting needs the beam to pass through the material, which means repeated passes or more power. Thin plywood on a diode is a cutting job; a photo on the same plywood is an engraving job, and the settings are different.
Reading a spec sheet
| Figure | What it tells you |
|---|---|
| Optical power (W) | Energy output, not wall power |
| Spot size | How fine a line the beam makes |
| Max speed | Travel rate at full power, often unrealistic |
| Passes | How many times the machine repeats a cut |
| Duty cycle | How long it can run before cooling |
Why speed matters as much as power
At twice the speed the beam spends half the time on each millimetre, so the effective energy drops by half. That is why a 20 W machine at 100 mm/s and a 40 W machine at 200 mm/s can produce the same cut. The difference is how long the job takes and how much heat spreads into the material.
Cooling and duty cycle
Diode modules heat up and lose efficiency. Many are rated for a duty cycle rather than continuous use, and an air-cooled module that runs hot will produce inconsistent engraving. CO2 tubes need water cooling; fiber sources are usually air- or water-cooled and tolerate longer runs.
Frequently asked questions
Is 40 W enough for a hobby?
For engraving and thin cuts, yes. For production cutting of thick plywood, no.
Can I upgrade the power later?
Sometimes the module can be swapped, but the frame, cooling and power supply may not support it. Check before buying.
Does more power mean better detail?
No. Spot size and focus decide detail; power decides how fast you can work.
What is optical versus electrical power?
Optical is the energy that reaches the material. Electrical is what the machine draws. They are not the same number.
Do I need a chiller?
CO2 tubes usually do. Some fiber sources do. Diode modules are air-cooled but benefit from a fan upgrade in long jobs.
The short version
Compare wattage only within one technology. Decide whether you are engraving or cutting, look at spot size and duty cycle, and treat maximum speed as a headline rather than a working figure.
The settings you will actually change
Most jobs come down to three dials: speed, power percentage and number of passes. Slower at lower power gives a darker engrave with less heat; faster at higher power gives a lighter mark and more speed. Passes are for cutting, not for engraving, unless you want a very deep mark.
Material thickness changes everything. The same settings that cut 3 mm plywood will scorch 6 mm without going through, and the extra passes deposit heat that warps thin stock.
How to find your starting point
Run a nine-square grid: three speeds across, three power levels down, on the material you plan to use. Label each square with the settings, keep the test piece, and start any new job from the closest match. Every new sheet of material deserves its own test, because density and glue content vary between suppliers.