Polycarbonate is acrylic's false friend: same transparent look, same thickness, same shelf in the shop — but it does not laser-cut. It absorbs infrared, yellows and burns instead of cutting.
What actually happens
Polycarbonate strongly absorbs the CO2 wavelength: energy stays in the material instead of passing through. The result is a yellow-brown, blistered, often cracked edge, and a sheet that warps over several centimetres.
Beyond 1 mm thick, cutting is simply impossible at any usable quality, whatever the machine.
The fumes are acrid and contain compounds from bisphenol A degradation. Not as corrosive to the machine as PVC, but not an exposure to treat lightly either.
How to tell it apart from acrylic
The simplest test is mechanical: acrylic snaps cleanly and rings bright when flexed or tapped, polycarbonate bends a lot and sounds dull. That impact resistance is exactly why it is used for safety glazing.
On an offcut, a knife score is enough: acrylic splits, polycarbonate resists and deforms.
When in doubt about an unlabelled sheet, do not run it: order cast acrylic (cast PMMA), which gives the clear polished edge polycarbonate will never give in a laser.
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.