If this is common knowledge I apologize for being the last to know…
I’ve been messing around with acrylic, both cast and extruded. I have been etching pieces and then cutting them (also with the laser).
All looked great coming off the laser but there was some residue associated with the rastering. I cleaned them with that 91% isopropyl alcohol that’s sitting near Big Thunder. It did a great job of removing the residue but then this happened to the extruded acrylic only:
Tiny hairline cracks starting at the edges and propagating inward 1-3mm. These cracks were not there before cleaning with the alcohol.
So I did some reading and it turns out that hot spots, probably from reflections from the honeycomb bed, cause mechanical stresses in the acrylic that normally aren’t an issue. Solvents disrupt these stress points just enough to cause cracks to form.
The solution (no pun), is to use a non-solvent cleaner like this:
I’ve got some on order and will report results.
Again this seems to happen only to extruded acrylic. There is a difference in polymer length between the two products, but I’m not certain of the details. Cast is shorter I think.
ETA: This might be the reason gluing laser cut acrylic is dicey. Gluing cast acrylic might give better results!