Laser Fire

[Joe Hillmann]

I just had a pretty major laser fire. The fire started on the inside of a jig I made to hold wood for cutting. It must have been burning on inside for several minutes before I noticed it.

When I noticed something was wrong there was no fire just more smoke than normal I opened the lid of the laser and it erupted in flames. first I tried to beat and blow the fire out. When I realized that wasn't going to work I grabbed the fire extinguisher. Even though the extuinguisher was only 6 feet away that extra time allowed the fire to get much bigger(I also forgot to pull the pin on the extinguisher before trying to spray it, so that added time to).

In the aftermath it the x&y controls still appear to work. The x belt is melted, the plexi in the lid is charred through. The entire shop is covered in soot. I am waiting for the lens to cool so I can clean them and see if they were damaged. There are two ribbon strips that are partially melted but the electronics appear to work so they may be ok.

[Steve Busey]

Ouch! Glad you came through unscathed (if not a little perturbed), Joe.

Which laser was it?

[John Bion]

Mmmm...note to myself....remember this warning! I'm off to order some more extinguishers.
Hope repairs don't come to too much. Regards, John

[Bruce Dorworth]

Not to self, have fire extinguisher ready when I open lid!! It sure could have been worse...

Bruce

[Mike Mackenzie]

Joe,

What system was it?

I would say if it was me I would use water or smother it or the new halon extinguishers. I have rebuilt several fire victims and the worst thing is cleaning out all of that dust it gets everywhere and I mean everywhere.

If it is the universal and need some help you can send me some pictures and I will give you my two cents on what I would do.

[Kevin Groenke]

We have a small fire extinguisher sitting on top of each laser for just such instances (at least 2 corrugated cardboard fires just last semester but no damage beyond cutting grid distortion)

We've been using "Tundra" cans which seem to knock things down pretty quickly. These are more of a liquid spray than dry chemical or foam so they're a bit less of a mess to clean up. Of course there is also a CO2 extinguisher 6-10 feet away in the event that the cans don't do the trick. The small cans are also less expensive to replace.


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[Ross Moshinsky]

For everyone talking about fire extinguishers, I'd suggest simply upgrading your exhaust system. Fire cannot exist in a vacuum.

[Rich Harman]

For everyone talking about fire extinguishers, I'd suggest simply upgrading your exhaust system. Fire cannot exist in a vacuum.

I nominate the above for the worst advice ever. :-)

I do agree that a good exhaust system can reduce the chance of fire, as will a good air assist. I would even suggest that the air assist is more important in that regard. But having good fire extinguishers ready at hand is certainly not less important. I have three next to my machine. A halon, AFFF and dry-chem.

Aslo, no exhaust system will create a vacuum - not even close. Not even close to close. Not even anywhere approaching what can be considered in any way close. At best, a very strong exhaust will drop the pressure inside the machine by a very small amount.

[Ross Moshinsky]

I nominate the above for the worst advice ever. :-)

I do agree that a good exhaust system can reduce the chance of fire, as will a good air assist. I would even suggest that the air assist is more important in that regard. But having good fire extinguishers ready at hand is certainly not less important. I have three next to my machine. A halon, AFFF and dry-chem.

Aslo, no exhaust system will create a vacuum - not even close. Not even close to close. Not even anywhere approaching what can be considered in any way close. At best, a very strong exhaust will drop the pressure inside the machine by a very small amount.

Vacuum is anything below atmospheric pressure. Are you suggesting that an exhaust system can't create an environment where the pressure inside the laser is less than the pressure outside it?

My theory is proven by this post. No fire when the exhaust system is on and when the lid is closed. The lid is open and magically the piece bursts into flames. Now imagine if there was even less oxygen available in the laser to begin with.

I'd rather prevent the fire then reduce the damage.

[Rich Harman]

Vacuum is anything below atmospheric pressure. Are you suggesting that an exhaust system can't create an environment where the pressure inside the laser is less than the pressure outside it?

My theory is proven by this post. No fire when the exhaust system is on and when the lid is closed. The lid is open and magically the piece bursts into flames. Now imagine if there was even less oxygen available in the laser to begin with.

I'd rather prevent the fire then reduce the damage.

Vacuum is anything below atmospheric pressure.

No. That would be a partial vacuum. Fire can indeed exist in a partial vacuum.

Are you suggesting that an exhaust system can't create an environment where the pressure inside the laser is less than the pressure outside it?

I said "At best, a very strong exhaust will drop the pressure inside the machine by a very small amount."

My theory is proven by this post. No fire when the exhaust system is on and when the lid is closed. The lid is open and magically the piece bursts into flames. Now imagine if there was even less oxygen available in the laser to begin with.

I don't think so. A laser's exhaust system only works because there is both a path for the air to go out and a path for new air to enter. With any exhaust system you are constantly resupplying the oxygen from outside air. There is no way for the fire to use up the oxygen when the exhaust system is drawing fresh air in. The more powerful the exhaust, the more fresh air is drawn in.

If you had some form of fire suppression system in your laser then I agree, it would be wise to not open the lid. It would also then be wise to turn off the exhaust so as not to continue to supply the fire with fresh air.

[Rodne Gold]

The fire probably flared up cos when raising the lid, the air assist stopped and a huge amount more oxygen was added "Woosh" - like when you crack a vacuum...
At any rate , when I drag raced , we used the non powder (Halon?) extinguishers mounted in the engine bay and operated via a cable in the cabin , maybe a system like that would work in the laser , a cable operated extinguisher fixed on the outside of the machine with a tube from the nozzle to the inside?
Maybe something like an adjustable heat/smoke sensor linked to an alarm right at the cutting nozzle , might give false alarms , but rather that than a fire
I dont think there is any really foolproof system to stop laser fires apart from having a human watch..which is a bit of a schlep

[Dan Hintz]

For everyone talking about fire extinguishers, I'd suggest simply upgrading your exhaust system. Fire cannot exist in a vacuum.

Personally, I would suggest against this line of thinking. You may have a partial (slight) vacuum in the chamber, but you're also pulling in fresh air from the shop and racing it across the burning material. Fires burn almost as easily at the top of a mountain as they do at the bottom, so the slight difference in pressure isn't the saving grace you're hoping it would be. That fast-moving air is likely to flare the fire up rather than keep it suppressed. YMMV...

[Mark Ross]

Its for this reason and the fact that no system auto senses fires or excess smoke that we have a large TV screen with a camera hooked up and pointed down at our two Epilog 36EXT's. Somebody glances up at the monitor and we have actually caught a couple of fires starting and stopped damage from occuring. It's frustrating but worse case, you have to pay somebody to watch the machine.

[Albert Nix]

Check out this link to fireade 2000. I have been fighting fire for over 30 yrs and it is the best I have ever seen.http://www.firesupplydepot.com/quick-order-page.html

[Mike Null]

I will join the others in advising against increasing or even operating the exhaust system during a fire. I have a blast gate on my system to shut down the exhaust and keep flames from spreading.

The best fire prevention is to pay attention to the laser when you are cutting.