Copper is the hardest metal to laser mark: it reflects nearly 95% of the infrared beam and conducts heat almost instantly. A fibre source is mandatory, and even then copper needs more power and more passes than steel.
Settings: what really matters
Work at full power and low speed: around 300 mm/s at 100% with a 20 W fibre, at a low frequency (20 to 30 kHz) that concentrates energy per pulse. A 30 W or stronger fibre is clearly preferable.
Several passes beat one very slow pass: heat dissipates between passes and the line stays crisp. For deep marking, expect 5 to 10 passes.
A MOPA source changes everything: by tuning pulse duration it produces a contrasted black mark where a standard fibre only gives shiny grey.
Common thicknesses and pitfalls
Copper is worked as 0.5, 1 and 2 mm sheet: dedication plates, jewellery, coasters, technical labels. Cutting is out of reach for a marking fibre: keep it for marking and engraving.
Main pitfall: reflection. A beam bounced off a polished surface can damage the lens and the fibre itself. Tilt the part very slightly, never work mirror-polished copper with an entry-level fibre, and check your machine is rated for reflective metals.
Copper oxidises fast: marking an already tarnished surface gives uneven contrast. Degrease with alcohol immediately before the run.
Risks and finishing
The metal particles produced by marking are fine and breathable: extraction is mandatory, along with glasses rated for 1064 nm — not those supplied with a diode engraver, which do not filter that wavelength.
After marking, very fine steel wool around the design removes oxidation without touching the mark. An acrylic spray varnish then stabilises the tone; otherwise the piece browns within weeks.
Every figure on LaserSettings comes with the machine, the laser source, the material and the thickness it was tested on. A setting published for a 10 W diode says nothing about a 40 W CO2, and a setting for 3 mm says nothing about 6 mm: check those four things before you copy any number.
Settings are confirmed or disputed by the members who reproduce them, so reliability comes from cross-checking rather than popularity. Photos of the result — cut edges, engraving shades, scorching — tell you more than a single number found on a forum.
Whatever the material, treat a published setting as a starting point: run a small power/speed test grid on an offcut, clean the lens, redo the focus, work with fume extraction and air assist, wear glasses rated for your wavelength and never leave the machine unattended.