What is laser power?
Laser power is the output of a cutting laser's source, measured in kilowatts (kW) or watts (W), so a 3 kW laser is also sold as a 3000 W laser. It sets the thickest material a machine can cut and how fast it cuts each thickness.
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What does laser power mean in fabrication?
When shops talk about a 3 kW or a 12 kW laser, they're describing the power of its laser source. More power puts more energy into the cut, so the machine can cut thicker material and, up to a point, cut faster.
Power isn't the only thing that decides what a machine can do. The cutting head, beam quality, assist gas and motion system all play a part, so two lasers with the same rating can perform differently.
How is laser power used?
Power decides which jobs a shop can take and which feed rates apply. A job in 20 mm plate isn't one a 1.5 kW machine can quote for. A job in 3 mm stainless will cut on both a 3 kW and a 12 kW machine, but at different speeds, so the quote has to use the speeds of the machine that will cut it.
Shops with more than one laser keep separate feed rates and pierce times for each, because the same part takes a different time on each machine.
Why does laser power matter?
Power is the biggest single factor in what a laser costs to buy, so it's the first decision when choosing one. It also drives running costs: higher-powered machines use more electricity and, when cutting with nitrogen, larger nozzles and more gas.
More power doesn't speed up everything. On thin sheet with lots of short moves and small features, the machine's acceleration and cornering limit how fast the head can go, so extra kilowatts add little. On thick plate cut with oxygen, cutting speed barely rises with power either. Power pays off most on mid-range thicknesses, and in letting high-powered machines cut mild steel with nitrogen or air at speeds oxygen can't match.
Laser power and thickness
As a rough guide to the maximum thickness a fibre laser can cut (everyday production thickness is lower):
- 1.5 kW: mild steel about 12 to 16 mm (1/2 to 5/8 in), stainless about 5 to 6 mm (3/16 to 1/4 in)
- 3 kW: mild steel about 16 to 22 mm (5/8 to 7/8 in), stainless about 8 to 12 mm (5/16 to 1/2 in)
- 6 kW: mild steel about 22 to 30 mm (7/8 to 1 3/16 in), stainless about 12 to 20 mm (1/2 to 3/4 in)
- 12 kW: mild steel about 25 to 40 mm (1 to 1 1/2 in), stainless about 20 to 30 mm (3/4 to 1 3/16 in)
Mild steel figures assume oxygen cutting, and aluminium is similar to stainless or a little less. The maker's cutting charts give the real numbers for a specific machine, and it's worth planning around the lower end of each range.
Laser power and quoting
A quote has to use the speeds of the machine the job will run on. If a shop has a 3 kW and a 12 kW laser, the same part needs different feed rates, pierce times and possibly a different hourly rate, depending on which machine cuts it. In Tempus Tools, each machine can be set up as its own cutting technology with its own rate table (feed rates, pierce times and an hourly rate for each thickness), so quotes match the laser doing the work.
Further reading: Tips for new laser owners
Related terms
Know what your assist gas costs per hour
Higher-powered lasers cutting with nitrogen get through a lot of gas. Our gas cost calculator works out consumption and cost per cutting hour from your gas, nozzle size, pressure and supply price.
FAQs
What does kW mean on a laser cutter?
It's the output power of the laser source in kilowatts. 1 kW is 1000 watts, so a 3 kW laser is the same as a 3000 W laser.
What laser power do I need?
Work from the thickest material you'll cut regularly, not occasionally, and leave some headroom. As a rough guide, 3 kW covers mild steel to about 16 mm (5/8 in) comfortably and 6 kW to about 25 mm (1 in). If most of your work is thin sheet, extra power adds less than you'd expect, because machine motion becomes the limit.
Does higher laser power cut faster?
On mid-range thicknesses, yes. On thin sheet with lots of detail, the machine's acceleration limits speed, so extra power adds little. On thick plate cut with oxygen, speed barely changes with power.
How thick can a 3 kW fibre laser cut?
Roughly 16 to 22 mm (5/8 to 7/8 in) of mild steel with oxygen, and 8 to 12 mm (5/16 to 1/2 in) of stainless steel with nitrogen. Everyday production thickness is usually a little below the maximum.