PET-G is the transparent plastic of guards, covers and displays. It cuts cleanly with a CO2 but not with a diode, and unlike acrylic it does not shatter: it bends. Its edge stays slightly milky, never polished like PMMA.
Settings: what really matters
CO2 only: a blue diode passes through clear PET-G without touching it. With a 40 W CO2, expect around 60% at 400 mm/min on 3 mm, in one pass.
PET-G melts rather than vaporises: too low a speed creates a bead along the line. Prefer a higher speed with slightly more power, and strong air assist.
For engraving, stay light (20% at 3,000 mm/min): PET-G whitens at the surface, giving a very clean frosted look, but too strong an engraving distorts it.
Common thicknesses and pitfalls
Common thicknesses: 0.5, 1, 2 and 3 mm. Beyond that, the melt bead becomes hard to control on a workshop CO2.
Pitfall: confusion with PVC. An unidentified clear sheet may be PET-G, acrylic or PVC — and PVC is strictly forbidden on a laser. When in doubt, cut nothing: a flame test on an offcut, outdoors, settles it (PVC gives off a sharp acid smell).
Keep the protective film on during cutting: it prevents smoke marks on the surface.
Risks and finishing
PET-G releases irritant vapours and traces of acetaldehyde: extraction is mandatory, never in a closed workshop without filtration.
For finishing, the edge can be softened with a fine file or 600-grit wet paper. Flame polishing, used on acrylic, does not work here: it distorts the material.
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.