Community notes to read alongside the official guide.
1. Cast, not extruded
Cast acrylic (PMMA) cuts with a polished edge and engraves frosty white. Extruded cuts fine but engraves dull and clear. The price difference is small; the visual difference is the entire job. For anything visible, cast.
Never polycarbonate. It melts, flames, yellows and blocks the beam. "Lexan" is polycarbonate.
2. One slow pass beats three fast ones
Multiple fast passes reheat the edge repeatedly and give you a cloudy, sometimes crazed finish. A single slower pass at high power leaves the flame-polished look people buy acrylic for.
3. Gentle air assist
Enough to keep flame off the surface, not enough to chill the cut edge. This is the difference between clear and frosty on an otherwise identical cut.
4. Film management
Leave the protective film on the top face while cutting — it protects against flare marks. Take it off the bottom face, or it traps smoke against the sheet.
5. Measure your kerf
Typically 0.15–0.20mm in 3mm cast, and it widens in thicker sheet as the beam diverges. Cut ten parallel lines 10mm apart, push the strips together, measure the shortfall, divide by ten. Then use that number in your file rather than sanding joints later.
LaserPecker publish their own documentation on this topic — worth reading alongside these community notes.
Official article