I am glad you haven’t had a flare-up. Have you cut cardboard under something else? Are you aware that the air assist and exhaust will not affect the cardboard under the acrylic in the same way as if you are cutting the cardboard directly? I have cut material elevated and seen the embers build up underneath. Since the air assist can’t blow it out and the exhaust pulls air across the embers at a much slower speed, they continue to smolder much longer than anything exposed to the air assist. There is too much risk for me to even consider something like this.
It doesn’t matter if you are there if you get a fire going under the target material because you can’t see it. Not worth it. Leave a cutout as mentioned in one of the replies, but don’t cut directly into a layered material with air pockets unless you can see it.
Glowforge requires us to confine discussion of manual settings in their forums to the Beyond the Manual category. The current preferred practice is to either move the entire thread to Beyond the Manual or, to start a new thread there and, link to it from this one.
@ben1, I don’t stack dissimilar materials and concurrently cut them - that seems really ill-advised, as the beam can only be tuned for one material at a time. I confirmed as much when I tried putting on some thick paper stock under the acrylic - it was a fire hazard and it gunked up the acrylic cut.
Simply elevating the acrylic at least 1 mm off the build tray seems like a decent alternative to inserting a shield material under the acrylic, IMHO. As for the material to use for elevating the acrylic, cardboard was a cheap and convenient source for me - but it could have been anything else, since it wouldn’t be in the beam path.
I have had bad things happen when covering the bed holes. The exhaust pulls smoke down into the bed to help clear it. When I cover the holes with tape, etc. I find that the smoke builds up under it, and the tape acts like cardboard; it can catch and burn because it isn’t cleared by the air assist.
If it works for you, great, just adding my experience.
I’ve always wondered if glass would be the ideal flashback-eater. It absorbs laser energy, it’s very flat, it has a high thermal and physical mass, it doesn’t gas out or make much if any debris when lasering 1 , it seems like it’s a good option. I’ve yet to hear of anyone using it, maybe because of the difficulty in cinching down your material. IMO tape would work very well here, it’ll adhere well to the glass and keep your material from moving… I wonder what it would do to the cutting to have zero pathway for the smoke/gases to go down.
1 (yes yes silicosis, but we’re not pulverizing it, just lightly scoring it, I don’t think you’re blasting glass chips everywhere)
I used some scrap acrylic, but it could be any material less than 4 mm thick. The eensy risers elevate 3mm, which is plenty high enough to avoid flashback, low enough for my magnets to still work well, and be easy to pluck out afterwards. I’ve attached the .svg (or at least I think I did…)
If you edit your post there will be a size next to the link (something like [image|1x1]), if you edit that to something in the hundreds it’ll be easier to see
The laser ablates the acrylic, and that hot gas has to go somewhere. If not down, then up, spraying all the debris, gas, etc. all over the cut edge. The result is a significantly duller edge.
Dumping a 40W laser beam into a glass plate seems really dangerous. There was chipping, and I imagine the heat buildup could lead to the glass shattering at some point - probably just as I lift up the lid and lean over to pick it up. So I think this is past my “Jackass meets Glowforge” limit.
My vote is for a black hole in sheet form, so I can send the beam off into another part of the universe
@deirdrebeth, bumped it to 1000x1000 - still looks tiny, but hopefully more clickable. It still doesn’t appear as a downloadable .svg to me however, so I think I’m not getting how to post files correctly. Sorry, but fortunately the design is really simple and easy to duplicate.
