[hackerspaces] Laser Cutter Fires?

[matt]

Foam Core torched our old epilog at resistor.

Biggest fire we had.   Did significant damage.

And frankly we're occasionally ... adventurous with our burninantion.

-matt

On Wed, Apr 29, 2015 at 3:51 PM, Nathaniel Bezanson <myself at telcodata.us>
wrote:

> Thinkhaus had a small fire back in 2011:
> http://www.thinkhaus.org/2011/04/03/lazzoring-is-serious-business/ and
> their post about it has become part of i3Detroit's standard laser cutter
> training. Thanks, Thinkhaus!
>
> At i3, we've had a few small fires in the chamber, though not by the
> apparently-common tray fires described by others in this thread. For us
> it's the material being cut, remaining aflame after the head moves away. I
> think corrugated cardboard is the usual culprit, since it has channels that
> can sustain "peaceful" combustion, even as the air-nozzle blasts down from
> above. (There's a project idea floating around, to use the oxygen-poor
> exhaust of a medical O2 concentrator, or just a plain old tank of argon, to
> supply the air assist blower with inert gas during the entire cut. I'd be
> super curious if anyone else has tried this and how it went! It should
> reduce edge char too, no?)
>
> Most folks just pause the job and Big Bad Wolf the flames, but the
> extinguisher has come into play at least once.
>
> I don't know how others' cutters are constructed, but on our big machines,
> the platform (tray?) is several inches below the cutting plane (there's the
> honeycomb, and then the slats, and then a gap caused by the slat bracing),
> and while the beam is still focused enough down there to melt through
> adhesive tape, I'm not aware of anything ever having caught fire in the
> tray. That's a good point worth making, though; we should give it a look
> after shutting down the exhaust, in case anything down there is smoldering.
>
> In addition to linking to the above Thinkhaus page from our tool-info
> page, I make a point to discuss the incident during training. (I don't know
> if other trainers do, but operators are supposed to be trained twice by
> separate trainers, so I think most have gotten The Talk.) We have a strict
> "do not walk away" policy, and have recently mounted a phone/intercom near
> the operator's position to help with this. Sometimes when I walk past, I
> make a point to offer to grab a soda for anyone babysitting an active job,
> even though I know they could easily pause the job and get their own, since
> I want to emphasize gratitude for their vigilance.
>
> We have a checklist for operation, which includes "lift the fire
> extinguisher from its spot and set it back down" as the last step before
> pushing Start, with the intent of both confirming that it's always there,
> and building the muscle memory of how to unhook it. That's a 5-pound
> nitrogen unit, which is what the service place offered as a replacement
> when our beloved halon unit went out of date. (That's a tradeoff.
> Nitrogen's environmentally harmless, but pound-for-pound, inert gas isn't
> as effective as halocarbons at actually extinguishing fires.)
>
> In the future if we ever get a tool-auth system going, in addition to
> badging into the laser to prove that you're on the operators list, I'd like
> to rig a switch so it confirms that the extinguisher-mount changes state
> before enabling the machine. For the time being it's all manual.
>
> Also sitting nearby is a 20-pound CO2, which every laser operator is
> encouraged to practice with before getting certified. We blast each other
> with it and generally treat it as nonthreatening, in hopes of building
> familiarity and reducing hesitation in the event of an actual fire. It's
> cheap to refill, and since it's not the "official" extinguisher for the
> area (that would be the nitrogen by your knee), I'm not worried about
> running it empty playing with it. That's happened once already, and I think
> the practice and familiarization was well worth the trivial refill cost. I
> plan to swap it for a 10-pound next time it's due; the 20 is clunky to
> handle.
>
> I've had a LOT of folks say it was the first time they ever actually
> pulled the pin on a fire extinguisher, much less discharged one. I think
> this is important -- we practice CPR on dummies, we practice fire drills by
> walking outside, even the AED has practice pads. Why isn't it more common
> to rehearse with actual extinguishers? They're cheap and fun!
>
> There's another 5-lb clean-agent (halon or nitrogen, I forget) in the
> electronics lab, and the rest of the space has big dry-chemical
> extinguishers everywhere. Most are mounted right near the supply-stations
> (paper towels, tape, pens, markers) in each zone, to capitalize on the
> habituation of turning toward those during other instant needs, such as
> spills.
>
> -Nate B-
>
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