Problems post-cutting/painting PMMA

[Mike Null]

My view is that the paint is the primary culprit. Depending on the area I have to cover I use acrylic craft paints or for larger areas spray paints for plastics. Here we have a brand called Krylon for plastics and I've found it works very well and dries almost instantly.

[Dan Hintz]

not too sure if it did yet, but my reasoning was if the beam temperature was different on each of the three cuttings, perhaps that would in some way anneal the edge more.

Annealing is a slow, controlled process... you cannot recreate it with a fast-moving laser.

[Steve Crawford]

Annealing is a slow, controlled process... you cannot recreate it with a fast-moving laser.

Thanks for clearing that up Dan... appreciated.

Well in the end all of the pieces where the solvent based paint was used, no matter how lightly applied, all cracked in the end, some only literally a couple of millimetres, but a crack non the less. Ive now tried two pieces with water based acrylics and all seems fine so far two days on. So from now I'm going to start spraying water based paints for my signs.

Thanks for all your help and advice people. If there are any further developments on this story I'll report back. But it seems the simple solution is not to use solvent based paint with PMMA/Acrylic Sheet.