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Thread: New project: Fire sensing laser cut out system - and maybe more later.

  1. #31
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    It seems to me using a inert gas like nitrogen or co2 for the air assist would be the simplest and easiest thing to minimize flare-ups when cutting prone to catch fire materials. Perhaps it's not so simple, but I do know ULS has a computer controlled air assist dual system for my laser that allows using air, or inert gas. Perhaps that alone wouldn't be fool poof but with the possibility of fire on both sides of the material I can see where it would be hard to monitor the bottom side especially when the cutting table is likely filled will smoke while cutting. My laser has a battery powered thermal sensor in it. If the battery dies or gets weak the laser will not operate. I think the thermal sensor is mounted on the rear wall and will shut the laser down if it detects "excess" heat to prevent the laser from feeding the fire. However it seems to me by directing a stream of inert gas directly at the cut and using that to blow out the debris you are letting the laser cut the material but minimizing lingering flames by preventing or limiting the o2 needed to support the combustion.

    What I get from Dan and Scotts comments is that if you make something that can detect "any" possible occurrences it is going to likely generate a lot of false alarms that will create more problems as far as productivity is concerned. My computer is 2 feet from the laser. I cannot go much farther away because ULS says to limit the USB cable to 6 feet max length. The port is about 1-1/2 feet from the right rear corner so by the time I come around the rear of the cabinet and to the front corner the 6 foot length is used up. So, I am always right there so to speak, and while I don't stand and watch every second the laser runs (depending on what is cutting) I am a one man show with our laser. We don't do near the volume that some of you do but I have over $60K invested in the laser and the small building we have it in. IMO the safeguards built into it hopefully would prevent a calamity but I think the first line of defense is me - the machine operator.
    Universal Laser ILS 12.150D (48"x24") 135 watts total, with 60 watt and 75 watt laser cartridges. Class 4 Module (pass thru ability). Photograv 3.0, Corel X6, Adobe Design Standard CS4 Suite, Engrave Lab laser Version 8, Melco Single Head Comercial Embroidery Machine, The Magic Touch System with Oki C711WT printer, and Graphtec CE6000-60 plotter.

  2. #32
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    Quote Originally Posted by Bill George View Post
    As a commercial HVAC tech who worked in many large computer rooms I saw systems that worked. If its good enough for a multi million dollar data center it should work for a $20k laser. The room is vacated (before) and ventilated after the dump.
    Those systems cost more than a $20k laser, too.
    And a total flooding system brings in a whole alphabet soup of government
    agencies with their own regulations.. not something to be taken lightly.

    And as you know, comparing suppression systems to extinguishers is similar to
    comparing Big Three US laser engravers to the $459 Ebay imports ;-)
    Avatar courtesy of the awesome Frank Corker
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  3. #33
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    Quote Originally Posted by Mike Lassiter View Post
    I think the first line of defense is me - the machine operator.
    You are a smart man Mike!

  4. #34
    Quote Originally Posted by Graham Facer View Post
    Scott: Do you have some more details on what you tried (what sensors if you recall, where you had them - even your arduino sketch?).
    I don't Graham. I have a customer that makes electronic things for a living. My vision was to create and sell an aftermarket kit that we could sell. I had a number of meetings with them (Electronic and software Engineers), and they did a lot of research on the sensors, etc. Every time we'd meet or talk about it, they'd talk to me about the parameters and at no point could I say anything was 100%, which meant it would be riddled with false positives and it wouldn't actually detect some really bad things (fire under material, which is far more dangerous than a flare up on top). The visual flame detectors were the direction we were going, but some times you get a flare up on many materials, when vectoring, that only lasts a second or two.

    The situation sounded like it would just send false positive after false positive, and you'd be running back to the laser to check that.

    In the end, we all agreed that it wasn't something we wanted to invest any more time or money into.
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  5. #35
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    Scott A simple time delay adjustable would take care of the flare ups on starting a cut. And nothing said you couldn't have more than one method. I will trust your judgment, but it seems like something that worked could really speed up production.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  6. #36
    That was the problem Bill, some flare ups are okay. A flare up in the Y axis when cutting Rowmark might last 3 seconds, and I might have paper mask on it so it's okay. A 3 second flare up un unmasked acrylic might lead to a terrible fire. A flare up on wood, I might ignore to some degree, but again, on acrylic, not so much.

    People a lot smarter than me were on the project and after I told them the conditions, they said we were chasing a moving target, which it is. There is nothing that works or could be filtered out that easily, and like I said, if you're getting buzzers going off for false positives (there's no way for the system to know if a fire is okay to leave or set an alarm because there's no way to know the difference in looking at it, since all fires start the same), then you're going to be constantly running back to the laser anyway. If every time I get 10 feet from it, it goes off and I have to walk back to it (or run), then I might as well just sit there and be around it when it's cutting.

    If I had the OP's situation, I'd do like I used to do, and how someone else has mentioned, I'd put a webcam on it, I'd open that webcam stream on a computer where I talk to customers, and I'd just casually scan the monitor while talking to customers. You could have that running in 20 minutes and it works great.

    (I didn't do it and go to another room, I watched it in the corner of my monitor while I did other computer tasks).
    Lasers : Trotec Speedy 300 75W, Trotec Speedy 300 80W, Galvo Fiber Laser 20W
    Printers : Mimaki UJF-6042 UV Flatbed Printer , HP Designjet L26500 61" Wide Format Latex Printer, Summa S140-T 48" Vinyl Plotter
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    Real name Steve but that name was taken on the forum. Used Middle name. Call me Steve or Scott, doesn't matter.

  7. #37
    Quote Originally Posted by Dan Hintz View Post
    My daily driver cost $50k... but it doesn't drive itself. I could spend $1 million and it still wouldn't drive itself. Just because a machine is expensive doesn't mean responsibility for operation falls out of the window.

    Several of us have given you a list of potential pitfalls in your solution, it's up to you to determine how to get around them. If you won't listen to those of us who have been there, done that, I don't see how much more help we can be. You're determined to make a fire prevention system that is likely doomed to not prevent fires, so I'll wash my hands of it now and just hope you don't get harmed in the process.
    Hi Dan,

    Well I hope you don't feel as if I've not listened. But its not a fire prevention system I am looking for - we seem all agreed that is impossible but can be limited by the operator/setup - this is a damage mitigation system.

    Fire prevention would be to create a system that prevents combustion, the design of this will be to prevent continued combustion.
    Last edited by Graham Facer; 02-24-2015 at 4:03 PM.
    Graham Facer
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    48" Generic Vinyl cutter, Roland engraver, and a dalhgren and vanguard on the project table.

    ...My pet peeve is a good thread with no conclusion because the OP solved the issue and disappeared. Either that or bus fatalities are much higher than reported.

  8. #38
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    I think some good ideas have been presented. Scott the webcams might be a good option. If the object was to save the machine it might not be feasible, but to prevent the building from burning to the ground might be.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

  9. #39
    Thanks Rodne... hard to see how that GCC system mounts and what sensor they use (though Dan sounds like he might be right) but thanks for the link.
    Graham Facer
    1530 Omni CNC router (run with Vcarve), Shenhui 1200 x 900 150W reci laser cutter (now with EFR F6 hopefully)
    48" Generic Vinyl cutter, Roland engraver, and a dalhgren and vanguard on the project table.

    ...My pet peeve is a good thread with no conclusion because the OP solved the issue and disappeared. Either that or bus fatalities are much higher than reported.

  10. #40
    Graham: What about a wireless remote that can activate the system by cutting the power and/or activating fire suppression from across the room? I would imagine a sensor/alarm setup used in conjunction with the video monitoring I suggested, would allow the operator to keep an eye/ear on the laser and quickly determine if the trigger is valid or a false-positive.

    1) Hear the alarm
    2) Check the monitor
    3) Decide to let the machine continue or hit the switch.

  11. #41
    Hi Matt,

    A remote kill switch would be relatively easy though the wireless communication issues would need to solved, but once it got the command the shutting off of the laser part should be easy.

    For now I'll call that plan B. A camera/alarm/cutoff would help but might be too far on the unattended side for me though I'd be happy to work on that at the same time if others are interested. I have a wireless IP cam handy so it would not be that big of a deal (in theory).

    Anyhow, until I get the sensors I don't have a lot more to add but I'd still be interested to get details on Scott's attempt. I ordered up a bunch more sensors on DX last night and a 1/4" air solinoid so now I wait for parts and maybe work on the program a bit.

    Graham
    Graham Facer
    1530 Omni CNC router (run with Vcarve), Shenhui 1200 x 900 150W reci laser cutter (now with EFR F6 hopefully)
    48" Generic Vinyl cutter, Roland engraver, and a dalhgren and vanguard on the project table.

    ...My pet peeve is a good thread with no conclusion because the OP solved the issue and disappeared. Either that or bus fatalities are much higher than reported.

  12. #42
    RF might be an option. I could even envision using this system to monitor in another part of the building.

  13. #43
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    Quote Originally Posted by Bill George View Post
    As a commercial HVAC tech who worked in many large computer rooms I saw systems that worked. If its good enough for a multi million dollar data center it should work for a $20k laser. The room is vacated (before) and ventilated after the dump.

    If using a CO2 extinguisher is hazardous then are dry powder ones safer? Choosing not to put out a fire because of the hazards of using an extinguisher would be a tough choice.

    There are many ways to detect a fire, UV detectors, flame flickering and temperature sensing that does not rely on melting a link or capsule. I have an Omron controller setting on my workbench that with a RTV or thermocouple sensor can pick up a temperature change in a manner of seconds.
    Bill, have you bothered to read the thread from the beginning? We've already discussed these points before. Sensors for house fires are different than those needed here. A system designed for a server room is significantly different than that for a small laser system (not to mention orders of magnitude more expensive).
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  14. #44
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    In the server rooms I worked in the sensors were linked together and it took 2 or more the set off the Halon fire suppression system

  15. #45
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    Graham, CO2 cylinder pressure is as I recall around 900 PSI. You can get small R size tanks which are 20 CF filled at any welding supply house. The companies like Pepsi or other local fountain distributers can also sell and fill the larger tanks.

    Does your sensor monitor exhaust fan intake temperature? Seems like if you had a fire the temperature would rise quickly, not gradual. Perhaps a comparison between ambient air and exhaust air temperature or just exhaust air temperature.

    Check here, we ordered a lot from these folks> http://www.kele.com/temperature-sens...nsmitters.aspx

    RADIANT ENERGY FIRE DETECTORS Retail > http://www.koetterfire.com/fire-detection-systems/

    and of course Honeywell makes them, http://www.honeywellanalytics.com/en...Flame-Detector
    Last edited by Bill George; 02-24-2015 at 4:13 PM.
    Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10

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