Fire - A Cautionary Tale

[Belinda Barfield]

If you are cutting closed cell foam, do not walk away from your laser, don't look away from your laser, don't even blink. If you must blink make sure that you have someone standing by who is not blinking. :eek:

As we all know, it's never a good idea to leave your laser unattended. But, hey, it's just for a minute . . . nothing will happen. Wrong! I was cutting foam yesterday and realized that I had left my glasses on my desk in another office. I checked and everything was cutting fine. This was the 7th sheet I had cut with no problems so far. I walked to the other office, found my glasses, took a swallow of my soda left over from lunch, and that's when I heard a sort of popping noise. I ran back to the laser to find flames scorching the top and foam on fire. I quickly turned the laser off, extinguished the foam and got it out of the machine. Not, however, without having done about $500 worth of damage. The good news is that then lens, mirrors, control panel, and wiring are all intact. The air nozzle melted and the air line is damaged. Other than that the honeycomb grid is trash and there is some major cleaning left to be done.

Many thanks to McKenzie at Jorlink who answered my call at 4:45 yesterday. He reminded me that there is a set screw that secures the air nozzle. I could not remove the melted remains of the nozzle and at the time I could not remember that there was a set screw because the voices in my head were singing, "You're an Idiot. You're an Idiot. You're an I-di-OT!" I have no idea why the voices chose the Hallelujah Chorus to get the point across! McKenzie also quickly pulled together the parts I need and shipped them to me overnight.

Things could have been much worse and I am very thankful that other than some minor parts to be replaced, some minor burns to my right hand, and a little scarring of the machine, all is well.

[Jerry Hewett]

Belinda,

Glad you caught the fire when you did! Hope all goes well with the laser repair, the Jorlink folks are awesome in their response.

[Ron Chapellaz]

Wow Belinda, that was a close one! Glad to hear that your quick actions saved the laser, as things could have turned out worse! It is amazing how fast things can happen. Your experience is a great reminder to us all on why it is important to watch the machine carefully. Take care of your hand and thanks for posting your story!

[Mike Null]

Belinda

Glad you were able to avoid too much damage.

Thanks for the reminder!

[Martin Boekers]

Belinda, this reminds me of a saying that a friend who rode motorcycles told me.

There are two kind of bikers, the ones that have accidents and the ones that will.

This is sort of fitting with engravers also, the ones that have had flare ups and the ones that will!

It will happen to all of us at least once, and it is so easy to get compacent. It is amazing thought
it always seems the one time something happens is the one time you don't follow your own protocol!

Glad it wasn't worse!


Newbies take notice, it literally does happen in a blink of an eye!

[Dee Gallo]

Wow Belinda, amazing what can happen in a split second. This must be where they got "a watched pot never boils over"... And we're all guilty of the "I'll only take a second" side trip away from the laser, but it only takes one time to create a disaster. I know I've done it once (yeah right) or twice. I'm glad you didn't get hurt more than you did and the laser is going to be okay too.

Thanks for the reminder and hopefully the newbies will take note... although it's probably the old pros who become more complacent with time.

cheers, dee

[David Fairfield]

Mr. Murphy is always waiting. http://www.freesmileys.org/smileys/smiley-devil16.gif (http://www.freesmileys.org/smileys.php)

[Belinda Barfield]

Thanks for the reminder and hopefully the newbies will take note... although it's probably the old pros who become more complacent with time.

cheers, dee

I think you are right about this Dee. I remember when I was a newbie and I was fascinated watching the machine run. Now I catch myself thinking "do I really need to stand here and watch this?"

Fed Ex was here at 9:30. I replaced the autofocus mechanism and the air nozzle. Now up and running and finished this phase of the job. I limped by with the air hose I have but need to pick up some hose today and replace that. In the next phase of the job I only have to cut 400 sheets of foam. I'm going to have to force myself to pay attention.

Thanks all for your support!

[Frank Corker]

Glad you managed to save yourself an awful lot of upset. Good cautionary tale to post too, I have always watched mine working like a hawk after the first week of having it when I saw a piece of acrylic catch fire. I thought that'll be the last time that happens on my watch. Touch wood.

[Gail LaPorte]

I am so glad that it was just a small fire and you was not far away and that you did not get a lot of it on you to burn you badly. I have burned a rubber stamp or two in mine it's like one section is okay and the next was a different matter altogether.

[Robert Walters]

Belinda,

Sorry to hear about the fire, especially on the 7th item.



Since it seems that these fires have happened somewhat at random, and within 180 seconds or so, I started looking into fire suppression systems.

While this is intended for marine engine compartment use, it is a "clean" agent (leaves no residue or condensation) so safe for electronics. These automatically dispense the agent once the temperature reaches 175F.

Now, I have an inquiry into them to see the cost to get one at 150F instead. When I asked why their "off the shelf" is rated at 175F, the head of engineering says that the engine room of most boats can normally be 140F and don't want to have any accidental discharges, thus 175F.

Our lasers, especially with blowers running, will never get anywhere near that ambient temperature, and since there is limited space to actually mount the extinguisher, it would seem that a lower (than 175F) would be appropriate here.

The 150F rating is just a random value at this point. If anyone has some resource to what the laser compartment temperature is (in the corners) during a fire, that would be helpful in determining what a safe discharge point would be.

Model MA2-025-227 is what I'm considering for it's size and coverage of 25 cubic feet:
http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=96210&catalogId=10001&langId=-1&storeId=11151&storeNum=10107&subdeptNum=10562&classNum=10564

They said that this floods the compartment and empties the bottle in less than 4 seconds (at this rate of discharge, a larger cubic foot capacity may be needed).
It has a NC (normally closed) switch on it that is connected Coast Guard REQUIRED indicator. This could be connected to a safety relay to use to remove power from the blower, air assist compressor, and laser itself.

Since this empties in 4 seconds, there is the question of the exhaust pressure venting the agent during this time. One thought was to use an electrically operated blast gate that would immediately close upon activation. So even if the dust collector is "winding down", it wouldn't remove the agent from the main compartment and let it do it's job.

To be effective, the agent needs to remain in the compartment for a minimum of 15 minutes.

I also came across an article at NIST: NITROGEN GAS AS A HALON REPLACEMENT
http://www.bfrl.nist.gov/866/HOTWC/HOTWC2006/pubs/R0000296.pdf

This whole setup could be done for under $400 is what I'm estimating so far.

This is just a rough draft and if you have something better/cheaper/more effective please share the wealth. Primarily compartment temperature info is what's needed at this point.


Sidenote: I think this and/or the older laser fire with photos post should be made sticky again. Seems it got lost in the upgrade shuffle.

[Paul Brinkmeyer]

Glad your OK.
I have been tempted to do the same more than a few times, usually with metal plates running, but then I think that there might be fumes from the plastic or wood I just cut drifting around some place and fight the urge to leave it running without me right there.
Your post just helps me stay put in the room with the laser. Thanks for that.
I even setup my shop so I can cut, edge and finish parts while sorta facing the laser. And of course, I set my computer so it forces me to be right in front of the laser.

One question I would like to ask is...would you have seen the fire out of the corner of your eye if you were in the room with the laser running, but not really watching the laser?

[Kay Bengtson]

I am glad that you caught the fire before it got too far. It is a very scary proposition to run a laser at times. I cut contest quality balsa which is really light and as such prone to catching fire particularly at sharp corner cuts. As a result, I stand and watch every cut with a wet paper towel in hand should the wood catch fire. If one does happen, I quickly douse the burn with the towel and that takes care of it. It has happened three times in six months but two of those times were because I had PPI settings that were fast. Now, I cut with the lowest frequency setting possible and if necessary cut twice at a faster speed to reduce the possibility of fire. Still, there are times when the phone rings or I get distracted and only after the job is well underway, I find that I have ignored it. Standing there for hours on end is really tiring too. I didn't see this as a requirement when I got the laser cutter so it is quite an adjustment. It also changes what I can do to maximize profit. I can't design while the machine is cutting a model airplane kit and that really ties my time up.

Kay

[Belinda Barfield]

Robert, thanks for doing the homework on this. I look forward to your input, and the input of others on this.


One question I would like to ask is...would you have seen the fire out of the corner of your eye if you were in the room with the laser running, but not really watching the laser?

I've run a lot of metal with Cermark, Paul, and usually don't watch the laser that closely with metal. I think that spoiled me. As to your question, yes, had I been in the room I would have seen the fire. The "design" computer that runs the laser sits on a desk right beside the laser. I can reach out and touch the machine from my chair. I would have noticed the initial flare. There isn't really anywhere to stand in that room that the laser is sitting right in front of me.

The foam I was cutting originally came on a roll. It still had a bit of "cupping" to it so I had to tape it down. As best I can determine a piece of the foam that had been cut free curled up and somehow blocked the air assist. Without air the foam ignites when the laser beam hits it. Bascially, I had several cuts that were all on fire at the same time. Why this didn't happen on any of the other runs was apparently just sheer dumb luck on my part.

Kay, it was sort of an adjustment to me as well realizing that I had to basically stand over the machine when cutting some materials. It definitely isn't a "start it up, leave it running, and - voila' - you have cut parts when you return" kind of business.

[Amy Shelton]

Belinda, thanks for sharing your experience. And the Hallelujah chorus in your head... I've heard the idiot song in my head as well. lol

I'm glad it wasn't worse... hope your hand heals soon. Burns can sure hurt.

[Robert Walters]

Robert, thanks for doing the homework on this. I look forward to your input, and the input of others on this.

Belinda,

I've been on the phone all day. Spoke to the owner of a fire sprinkler company (who happens to have a laser engraver too) and had some really good ideas to be able to install a fire suppression system in a laser engraver that can be removed for servicing the laser as needed and inexpensively be recharged.

Need to run some measurements on temperature in the laser compartment to determine the proper sprinkler head and a couple of other factors. Mind you, this is not UL or FM approved by any means, so you probably wouldn't get any discount on insurance, but might give some peace of mind that if a fire did start, the system would put it out and not damage the engraver in any serious way.

I'm waiting for him to send me an email with more info and pricing on a few components. When I find out more, I'll let you know.

[Kim Vellore]

One could have small thermocouples or any temperature sensor that is real fine and attached to the lid, if the temperature increases (rate or raise) is sudden you could set off an alarm and also have a absolute setting to set off an alarm. I would personally prefer this over a extinguishing system. In this case you could set the lid temperature for alarm as low as 100F and intervene before any damage. The additional piping for dumping that high volume of suppressant suddenly inside will be quite large and also the lid is light enough in most cases that it will just pop open on discharge. These are just my thoughts I am sure you will calculate the real numbers or test to make sure. Kim

[Robert Walters]

One could have small thermocouples or any temperature sensor that is real fine and attached to the lid, if the temperature increases (rate or raise) is sudden you could set off an alarm and also have a absolute setting to set off an alarm. I would personally prefer this over a extinguishing system. In this case you could set the lid temperature for alarm as low as 100F and intervene before any damage. The additional piping for dumping that high volume of suppressant suddenly inside will be quite large and also the lid is light enough in most cases that it will just pop open on discharge. These are just my thoughts I am sure you will calculate the real numbers or test to make sure. Kim

Hi Kim,

I personally prefer a mechanical device over electrical, but a temp sensor is not out of the question at this point. Lots of testing to be done, that's for sure =)

As far as suppressant goes, we've already discussed capacity and rate of discharge and just need to test the numbers. One of the issues that I had with the system that I linked to above is that it completely discharges the agent in less than four seconds.

What we've come up with allows us to "dial in" the discharge rate which would give the system time to shut down the exhaust system and to continue discharging the agent for 20+ seconds. Having the compartment maintain a flooded condition for 10 minutes is best, but will depend on the vents of the laser, airflow, etc.

We can also regulate the discharge pressure, but will keep the lid in mind during any testing as well.

[Ted Calver]

Let's see....would the laser manufacturers make more money from selling replacement parts to repair fire damage, or from selling fire supression systems as an accessory to prevent fire damage?? Maybe it's a more difficult task to design a reliable supression system than it seems.

[Paul Phillips]

Belinda,
glad to hear your OK and didn't see worse damage, fires are always a scary thing to deal with. I've only had my laser for about 7 months now and after 4 months of no flare-ups or fires thought I was fine with my high volume dust collector but, one day I was cutting some 1/2" acrylic letters and all of the sudden I had several spots that decided to flare-up, fortunately I was keeping a close enough eye on it to catch it quickly.
I'm sorry you had to be the one to get caught by it but, by sharing your experience you help remind us all just how serious our responsibility is when operating our machines-thank you!
This also brings up a great question about fire safety and suppression, why is it not standard issue on new machines, or at least an option? Manufacturers, are you listening? I know I would pay for a fire suppression option. I know my ULS comes with an alarm built in and that does offer some warning at least.
Robert, thanks for the info on the fire suppression, I'm sure there are many here that would like to have that info and make use of it, please keep us updated on what you come up with.
Thanks,
Paul

[Richard Rumancik]

I doubt that the laser manufacturers want to profit on someone's misfortune of having a fire. I think part of the problem might be the legal issues associated with any sort of suppression system. What if there is a fire and the suppression is not triggered? What if there are false alarms which cost money for chemical, cleanup, damaged material, downtime etc? How are you going to convey the benefits of this device to the customer - that it allows unattended operation? That may be a risky claim to make. By what method does the customer test the system for proper operation - and how often should it be tested? Lots of issues for a laser manufacturer to deal with.

I have some concerns with any "automatic" release of chemical or gas. A system that sounds an alarm is one thing; something that releases fire suppression material is another.

I highly doubt that a thermal type switch is the optimum way to detect a fire of this sort. What is the temperature in the laser chamber during a fire? Well, it depends on where the flame is relative to the detector. If the detector is many inches away it may NEVER actually get up to any significant temperature beyond air temperature. I will bet that you could have considerable damage yet much of the laser never really gets warm. I would suggest that an optical device that detects the presence of flame would be needed.

But there are many materials that may put off a small amount of flame here and there, and it will self-extinguish within seconds. So you don't want the system to decide there is a fire when you are standing right there watching with no concerns.

A suppression system may add some protection, but to me it should be manually operated based on a decision of the operator, once the operator is alerted via an audible alarm.

The other concern I have with this is that it may give a false sense of security. If I install this, can I go for coffee break while my laser works away? How do I really know how it will act under fire conditions, unless I run some tests to see how it performs. I'm not sure I would like to do those tests on my laser . . .

I think the best compromise is an audible alarm triggered by an optical detector. If you want to plumb in a manually-triggered suppression system instead of using an appropriate extinguisher, that might help get the fire out a few seconds earlier.

[Robert Walters]

Paul,

Fire suppression being offered as an option holds a lot of liability.
If there is a failure in the system and burns the house/shop down, who's responsible for that?


Richard,

There are pros/cons in everything and not everyone is going to see eye-to-eye on this.
This is the second smaller laser fire that I'm aware of. The bigger one is here:
http://www.sawmillcreek.org/showthread.php?125121-For-Sale-CHEAP!-Epilog-Legend-36-EXT (http://www.sawmillcreek.org/showthread.php?125121-For-Sale-CHEAP%21-Epilog-Legend-36-EXT)

They went to the restroom and came back to that. Now, if I happen to have had lunch that didn't agree with me (or whatever) and then an alarm goes off which I can't get to it fast enough I'd personally want something to "cover my back" for those what if scenarios is how *I* see it.

I doubt I would ever use 'optical flame detection', just the normal laser operation periodically produces flare ups that could be seen as flame and give a false positive.
Same goes with smoke/fume detection as those are things that are produced regularly.

This has NEVER been intended to let the operator leave the laser unattended. But if a job takes 20 minutes to run, and there's a knock on the door, etc. it would give an added layer of protection. Common sense still prevails.



All,

As I get further along with testing I'll try to keep everyone informed of my progress.
The system I linked to in a prior post is intended or marine use, which can be a life-safety issue. A boat dead-in-the-water is far better than one at the bottom of the ocean. Maybe a suppression system for a laser is not feasible, though it does look good (so far) on paper, won't know for sure till I run some tests and give it a try.

[Mike Mackenzie]

All of the new Universal laser systems have built in devices and protection already. Heat sensor that will sound an audible alarm and shuts down the system is standard on all systems. Also the top door window this believe it or not is more important than the alarm what the window does is contain any fire inside the system. Yes damage will happen inside the system but your bldg, home are better protected because of this window.

The very bottom line here is that the end user must take responsibility for what they are doing with the laser systems. These machines only do what the operator tells them to do. The users should always be aware that lasers can cause flame and should pay attention to what they are doing.

I may be wrong with this but working with lasers for more than 20 years I have never seen major fires in systems that were only 10-15 seconds.

Materials take time to ignite and start burning maybe 2-3 minutes and in most cases that I have dealt with they were left UN attended and or trying to exceed the capacity of the system (cutting 1" acrylic with 30 watts).

This is the real issue not the laser system or laser manufacturer.

[Amy Shelton]

I am trying to get in the habit of pushing "pause" on the laser when I have an interruption, then "resume" when I can get back to it.
Or having someone else come watch it for a few minutes.

Mike, how do we know which ULS machines have heat sensors, etc?

[Mike Mackenzie]

Amy,

All VLS, PLS, & ILS systems are equipped with the sensor and the top door glass.

Your system does not have it and you do the correct thing by utilizing the pause button.

[Dan Hintz]

Materials take time to ignite and start burning maybe 2-3 minutes and in most cases that I have dealt with they were left UN attended and or trying to exceed the capacity of the system (cutting 1" acrylic with 30 watts).
The dust collector's air pull can fan flames to huge proportions in just a handful of seconds (literally). Dry wood thins (or worse, veneers) can go up in a heartbeat.

[Mike Mackenzie]

Dan,

My Point was toward this post http://www.sawmillcreek.org/showthread.php?125121-For-Sale-CHEAP!-Epilog-Legend-36-EXT (http://www.sawmillcreek.org/showthread.php?125121-For-Sale-CHEAP!-Epilog-Legend-36-EXT)

It would still take a while for veneers to get to the point where they are out of control and burning the system up.

The key here is not how fires start it is why they start, If you put something into the machine that you know is flammable then you should not leave it alone thats it.

[Richard Rumancik]

Thanks for your comments Mike on this issue. It appears that the ULS strategy is to attempt to contain the fire and thereby protect the building, which may have a value many times more than the laser. I can see the logic. The non-flammable lid makes sense as well; I always wondered about the use of acrylic lids.

I'm still a bit surprised that they went with a heat sensing device to detect a fire. I would have thought that an optical flame detection system based on UV or IR (or a combination of these) would be more appropriate. I realize heat detection is simple but I doubt it can react fast enough to protect the laser (as Robert wants to do.) I suppose if the objective is to contain the fire, realizing that the laser will be toast, then perhaps it would work well enough. Obviously heat detection is much simpler.

It gets back to my earlier comments - when an OEM designs this (or someone retrofits it to their own laser) it is necessary to have a clear idea of what kind of event you are trying to prevent from happening and what consequences are acceptable. ULS is saying that their implementation will reduce the chance of losing the building.

LaserPro has a SmartGuard fire detector - they are quite reserved as to what they promise. They say that the operator can work more "confidently" and allude to protecting equipment and the safety aspect. But they really make no specific claims from what I see. I can understand why. Also, there are 5 user selectable sensitivity levels - that tells me something as to the difficulty there is in determining that there is a "real" fire.

[Robert Walters]

I came across an after market heat alarm that requires
no batteries, no wiring, no plumbing, or special installation...


http://i51.tinypic.com/18mdfq.jpg

[Chuck Stone]

Even after reading this (and others) I still got caught this afternoon. And I was watching, too.
I'm cutting out some inserts from polyurethane foam and I'm watching it cut. And out of the
corner of my eye I see the flame. And I look over at it, kinda marveling at the way it smokes
and slowly turns the foam a darker color while the laser cuts right through without so much
as a slight color shift when it .. oh, wait a sec ..
.. FIRE!!!!!!
Here I was, watching it cut, thinking about how I have to be careful that it doesn't burn,
and when it actually ignites, it still takes my brain a few seconds to put it together..

[Robert Walters]

Chuck,

Glad you were there to catch it.

I don't know what kind foam you were using, but most of them are petroleum based.
May I ask if it went out on it's own after you shut off the laser or did you still have to put it out?

[Chuck Stone]

Hard to say/remember .. once the brain finally kicked in and realized that it was burning,
I hit Pause, opened the lid and grabbed the foam to pull it away from the lens. With the
other hand I grabbed the water bottle and sprayed as I blew on it. It went out right
away, but not sure if it was because of the water, the air or if it just went out on
it's own. But by the time I opened up the cover, the part that was burning was far away
from the beam and the flame was getting bigger, so I think it would have kept burning.
It was small and I stayed with it, so I wasn't too worried.

After it was over I had time to wonder why it took me a second or two for the brain to
get into gear.. I had time to think about chestnuts, marshmallows and driftwood.

FYI this was urethane foam I got from an upholsterer and he called it Ultra-Soft something..
He uses it for jewelry box inserts and liner padding for sun visors for auto restorations.

[Belinda Barfield]

I can't answer for Chuck, but the foam I was cutting did not self extinguish. I had to put out every piece.

In the coming week I'll be cutting veneer. Fortunately, the veneer comes to me with flame retardant applied, but you can bet I'll still be watching every cut.