It seems most of you old hands on this forum have tried most things with your lasers - has anyone managed to cut shapes cleanly out of CDs? One might want to ask why.... it is a long story for another day. My understanding is that they are made out of polycarbonate, and having had a shot at it, I have managed to cut some shapes out, and it has taken more power than the equivalent acrylic (perspex/plexiglass) would have done. However the cuts are not as clean as acrylic, presumably because of the difference in the material, and the fact that there is a layer of aluminium in there too, confusing things. However, is there a guiding principal as to how I might adjust things such as PPI? I mean is it just a question of trying different settings, or should I be thinking along the lines of "more PPI means smoother edges..." Could lower PPI conceivably give me smoother edges? Or have I just to find that optimum setting....?

And finishing acrylic and polycarbonate - I have previously used Brasso (silverware polish, spirit based with fine abrasive suspension in it) to polish the edges of acrylic (I needed a bevel which I did by paring it down with some scissors....) without any knowledge of the possibility of stress cracks appearing. So far this hasn't happened, but when I cleaned up the CD pieces with Brasso, stress cracks appeared immediately all along the cut edges (sort of perpendicular to them). You could actually hear them forming!

Whats the thinking on this? Is polycarbonate more prone to stress cracks, maybe due to the extra power needed to cut it and its re-setting in a stressed way? Or does acrylic just not get stress cracks? Or not as easily...... or what?

Any help please. .... and the weird text sizing thing happening here is a bit confusing too....

Pete Andrew