I found it on another forum where the author of the topic provides a document of his own authorship which gives several tips for laser cutters.
The text of the original topic:
[quote]I’m new user Mike. I’ve been using a CO2 laser since 2002 and have created a tips and techniques document on what I’ve found (and wish I knew before). I’d like to share it. It’s really a work-in-progress. I work at Microsoft Research Hardware Lab where our two lasers get more use than a screwdriver.
Here’s the document
LaserCutterTipsHero.pdf
It describes methods for precision bending thermal plastic, welding, creating smooth beveled edges and much more.
Thanks for sharing this. One thing that jumped out at me as I perused the document was that he indicates that the kerf when cutting plastics is smaller at the bottom of the cut than the top. I haven’t done a lot of work with various plastics, just a limited experience with acrylic, but this is counterintuitive to me.
I think cutting too much foam has melted my brain. My experience has been the exact opposite to this. Wider kerf at the bottom. I suspect based on this new information is that what’s happening is that the top areas, where focus is best, is getting vaporized but that the lower portions, with worse focus, are melting instead of vaporizing. This is causing the material to contract to either side of the beam, thus creating a wider kerf at the bottom.
I’ve aimed midway through material for the same purpose of improved cut and straightening out the kerf but it compromises surface quality which is paramount for what I do. Ironic that the same technique addresses both conditions.
My experience with wood and acrylic did not show any appreciable difference in kerf width top to bottom but I generally work with thin materials <3mm.
