A CO2 fire extinguisher can be used carefully so the sudden cold does not warp or break anything, but most useful is a spritzer of water and a cloth towel that will take care of any fire that is likely to come up while you are watching. In the case of some species of wood I even wet them down ahead of time to limit the fire.
A chemical fire extinguisher can do almost as much damage as the fire,
i have cut a crapload (i think 400 sheets or so) of gator board (which is a denser version of what foamcore is) and a little bit of foam core on a laser cutter at work (not the GF, an industrial cutter, but still CO2). we use it for a base in between layers of cans when building canstruction structures.
from a fume perspective, it’s not an issue. it is a flame risk, for sure. but honestly, if you’re monitoring it the whole time (and I was), a spray bottle of water and a towel will take care of any flareups. i saw a few times where we had a sharp corner that there were red spots (like where you would see coals in a fire) but they all self extinguished quickly and we didn’t have to pause the jobs. but if we had, i’d have spritzed it with the water bottle and pressed the towel onto that spot.
so the real key is literally watching it the whole time it cuts. if you can’t do that, i wouldn’t cut foam core.
not quite as much, but you’re still going to get a concave edge. the bigger difference is that the whole board is stiff enough that even those edges hold up if you don’t put too much pressure on them. whereas foamcore is easy to fold/spindle/mutilate. we make 72x30 boards that stand vertically and lean against a wall that have lasted longer than i’ve been with the firm (14 years) and are still going strong. if that was foam core, it would have bowed and folded by now.
I have cut some foam core [I think the brand here is readi-board] and also had worries about the possibility of flare ups. For foam core [and also corrugated cardboard] I tend lower the power and do multiple passes. My theory [which may be unscientific] is that the lower power/higher speed reduces the chance of flare ups. For the foam core I am using 500/45/3 passes [on a basic]. 3 passes does increase the print time.
hah, you actually just reminded me of the one time i did a monster custom cut on gator.
the old assistant managing principle of our office (who’d moved on to manage our atlanta office) was coming in town for a big meeting. he runs our boost mentoring program (special program that a small group is chosen for) and they do four in person meetings in a year. this one was in our office. our executive committee was also in our office that day for their quarterly meeting (matching up with the mentoring program intentionally). i managed to get someone in the atlanta office to take a full head to toe photo under false pretenses. then i printed it out life-size and mounted it to one of those aforementioned 72x30" gator boards (we save some of the old ones just in case we need them for building stuff). then i took a jigsaw and cut him out silhouette style. put a perpendicular base on it and stood it up in the lobby of our office next to the elevators with a “welcome to the office” sign hung around it’s neck.
the mentoring meetings started earlier than i get to the office. so when i walked in and past the main conference room (called the fishbowl because of the glass wall opening into the open space and communicating stairs to the 3rd floor) i saw JP in the conference room giving me the slash across the neck sign.