Cast acrylic is the material that gives the most beautiful CO2 laser results: a clear, glass-like polished edge with no finishing at all. But it demands the right source — and it does not cut with a blue diode.
The question of the source
Clear acrylic lets a diode's blue light straight through: the beam crosses the sheet without being absorbed and nothing cuts. The source is at fault, not your settings — raising power will not help. Only CO2 sources (10.6 µm) cut clear PMMA cleanly.
Black or coloured acrylic does absorb blue light: it cuts with a diode, but with a matt, unpolished edge.
Grade matters too: cast PMMA gives a clear edge, extruded (XT) gives a milky edge and distorts more. For a visible part, choose cast.
Settings: what really matters
For a polished edge you need the opposite of what most people assume: a single, slow pass at high power. The material must melt through the whole thickness at once. Several fast passes give a striped, matt edge.
Turn air assist off (or way down) when cutting: the airflow cools the molten material and clouds the edge. It is the one material where you deliberately disable it.
When engraving, cut acrylic appears opaque white. Stay at low power and high speed: too much energy melts the edges of the path and the artwork smears.
Risks and finishing
PMMA is not chlorinated and cuts relatively cleanly, but it melts into burning drops that can ignite: never leave it unattended, especially on slow high-power cuts.
Never confuse acrylic with polycarbonate. Polycarbonate does not laser-cut: it yellows, sticks and gives off acrid fumes. When in doubt about an unlabelled sheet, do not run it.
Leave the protective film on while cutting and peel it at the very end. An already-matt edge can be re-polished with a quick pass of a gas torch — practise on an offcut first, the margin is thin.
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.