Unlike clear acrylic, black or coloured acrylic absorbs blue light: it therefore cuts with a diode as well as a CO2. It is the most versatile plastic in the workshop, and the one that gives the most legible engraving.
Settings: what really matters
For CO2 cutting the rule matches clear acrylic: one slow high-power pass for a clean edge. On a diode you often need two or three passes on 3 mm, and the edge stays matt — that is normal, a diode does not melt the material the same way.
When engraving, black acrylic gives instant contrast: the engraved area appears milky white on glossy black. Stay at low power: the goal is to frost the surface, not to carve it. Too much energy melts the edges and the artwork loses its crispness.
Cast acrylic whitens strongly, extruded much less: for an engraved plate meant to be read, choose cast.
Risks and finishing
Acrylic melts into burning drops and can ignite on a slow cut: supervision is mandatory and extraction must run. It does not release chlorine, unlike PVC — but never confuse the two: an unlabelled black sheet could be either.
Leave the protective film on while cutting. After engraving a dry microfibre cloth is enough: alcohol-based cleaners attack the surface and leave a permanent white haze.
To lift an engraving, a little acrylic paint worked into the recesses and wiped flat looks very clean on glossy black.
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.