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View Full Version : F2 Laser Fire - Don't leave laser unattended!!!



John Blazy
01-22-2019, 10:59 AM
Hi All,

Been a long time, but thought I'd show up with a warning we all need to hear. I was cutting some epoxy-based laminate samples - section only 3" x 14" into dozens of little 3/4 x 2" rectangles. Cut this material many times before, no flame. Calling an "F2" on tornado scale, because it could have been much worse, but still ceiling damage, entire room needs emptied, cleaned, and redone. Went through three large fire extinguishers to get the fire out.

Many contributing factors:


Running a business, not a hobby, so pressure to get stuff done, hit deadlines etc, always pushes one to do other things during auto machine cycles, oven cycles, curing phases, etc, so I often leave the laser room, but not anymore.
Lasering small pcs causes lots of concentrated heat / gas buildup within tight area, even though exhaust is always on.
lasering near an edge.
No big fire extinguishers immediately near laser, just a small one, and it was too close to laser to grab anyway.


What to change:


Never leave laser room during operation - Bring small jobs into laser room to do while monitering (shipping, labeling, packing, computor work, etc)
Make sure blower pre-filter is cleaned often for better exhaust
keep large extinguisher right at entry door, and more
replace lid window with tempered, laminated glass instead of plastic like it had. I think it was polycarbonate, which is the most flameproof of all plastics, but still melted allowing flame propagation. Tempered glass would be a great indicator of a fire, because its explosion will be heard across shop. Laminated would keep it together during fire (a little).


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Julian Ashcroft
01-22-2019, 11:08 AM
Is that grid what you were cutting or your base? It looks like it's made of plastic.

Gary Hair
01-22-2019, 11:25 AM
All good observations but a glass lid would be a bad idea - acrylic and polycarbonate absorb the beam that our lasers generate but glass does not, not fully anyway, so you would open yourself up to a reflected beam exiting the cabinet through the glass. The other thing is that glass would be so heavy that the door would be extremely difficult to open and the shock-absorber lifts wouldn't keep it open.

John Blazy
01-22-2019, 11:48 AM
Is that grid what you were cutting or your base? It looks like it's made of plastic.

Its a non-reflective grid from MDF, kindof burns if constant heat, but mostly is a good grid, as the laser does not reflect off it when cutting acrylic (which leaves lines in edge with honeycomb aluminum). I ran steel rods through it for magnet holds.


All good observations but a glass lid would be a bad idea - acrylic and polycarbonate absorb the beam that our lasers generate but glass does not, not fully anyway, so you would open yourself up to a reflected beam exiting the cabinet through the glass. The other thing is that glass would be so heavy that the door would be extremely difficult to open and the shock-absorber lifts wouldn't keep it open.

Totally correct with the weight. I was hoping to work around that with 1/8" temp glass - similar weight to 1/4 lexan. As far as the safety of stray, reflected laser light - not really concerned, as the beam never reflects up with enough intensity to go through glass, as its all reflected down. I think the lid is just CYA for the laser mfrs. Not one operation that I do reflects intense laser light up in a dangerous way. I do agree that glass is pretty much transparent to lasers. .030" Lexan is more opaque to UV and IR than 1/2" glass - tested that back when I was a UV chemist, and tested "opacity" of clear materials over a UV / IR Radiometer (power puck). Laminated glass, however is just as opaque to the beam as lexan / PC, which is my plan. The EVA laminating resin is high heat resistance, high radiation opacity, and thin. Planned to laminate .030" EVA to 1/8" glass (since I have glass laminating ovens and tech). Should be fine. I appreciate your response though.

Kev Williams
01-22-2019, 12:06 PM
Sorry for your loss, and very glad it wasn't worse (a friend of mine had a faulty battery charger take out a 10-plex set of garage shops, $10mil in damages, and no insurance :( )

for what it's worth-- this is a piece of 1/32" thick polycarb, very thin, that I just hit with a propane torch-
While the edges would flare up slightly, I could not make it catch on fire, all it would do was melt--
401835
And this just came to me as my furnace just kicked on--- a much better indicator of fire (than exploding glass ;) ) would be to install a heat switch, like those installed in furnaces above the combustion chamber to activate the blower... it would be a piece o' cake to mount one right in the plex lid, they require no power, just a couple of wires to trip a relay to set off a loud alarm. Any type of thermocouple switch like used in kitchen ovens should work too...



.

Doug Fisher
01-22-2019, 12:12 PM
Sorry about the fire, John! I am glad the fire didn't spread into your structure. About how long would you guess the fire was burning before you discovered it?

We all have stepped away from the laser and just been lucky. It is often so inefficient to babysit a laser! I am looking into camera options where I run a monitor I can watch if I step into the room next door. LightBurn has some camera functionality built into it. A camera inside my machine might actually be better because I am often sitting down and having to turn my head to peer through the vent hole grid on the front of the machine to look for flames.

Scott Shepherd
01-22-2019, 2:21 PM
Been there, done that. Except I never left the room. I was sitting next to the machine and had just looked at it. The fire started below the surface so it was gaining strength without my knowledge. Seconds later, it was a fire.

Universal lasers use glass lids with a metal frame.

John Blazy
01-22-2019, 4:04 PM
Sorry for your loss, and very glad it wasn't worse (a friend of mine had a faulty battery charger take out a 10-plex set of garage shops, $10mil in damages, and no insurance :( )

for what it's worth-- this is a piece of 1/32" thick polycarb, very thin, that I just hit with a propane torch-
While the edges would flare up slightly, I could not make it catch on fire, all it would do was melt--
401835
And this just came to me as my furnace just kicked on--- a much better indicator of fire (than exploding glass ;) ) would be to install a heat switch, like those installed in furnaces above the combustion chamber to activate the blower... it would be a piece o' cake to mount one right in the plex lid, they require no power, just a couple of wires to trip a relay to set off a loud alarm. Any type of thermocouple switch like used in kitchen ovens should work too...



.

Thanks Kev for the idea - great idea on the heat sensor. Was concerned that it would go off wayyy too often with normal use, but hey. Another reason I like my glass idea is because once the lid lexan melted through, the fire spread way more, and hoping glass would stay intact longer, but once it shatters, even with EVA laminate, it still would slump in, opening up for air to breathe.


Sorry about the fire, John! I am glad the fire didn't spread into your structure. About how long would you guess the fire was burning before you discovered it?

We all have stepped away from the laser and just been lucky. It is often so inefficient to babysit a laser! I am looking into camera options where I run a monitor I can watch if I step into the room next door. LightBurn has some camera functionality built into it. A camera inside my machine might actually be better because I am often sitting down and having to turn my head to peer through the vent hole grid on the front of the machine to look for flames.

Thanks Doug! I think it was burning at least five minutes before I saw smoke pouring from the room. Could have been more. Five minutes for a fire is eternity - plenty of time for the animal to eat (Backdraft reference).


Been there, done that. Except I never left the room. I was sitting next to the machine and had just looked at it. The fire started below the surface so it was gaining strength without my knowledge. Seconds later, it was a fire.
Universal lasers use glass lids with a metal frame.

This was my first serious fire. Had at least two before like yours, that I caught - was in the room monitoring it. It builds under the material where you can't see it. Plenty of times have I shot the little fire with water bottle then air hose, then water bottle, etc. Acrylic cuts near edges or tight are the worst. I was cutting these dichroic acrylic pcs and had to space the parts and internal cuts 1/2" from any edge, otherwise cuts within 1/4" of edge seem to love to catch fire. Thin areas get hot quick, coupled with air flow being higher near edge.

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Scott Shepherd
01-22-2019, 5:08 PM
Oh, mine wasn't little :) Did $3,000 worth of damage to the laser. We put a camera in one laser and it's plugged into a 32" monitor that swivels on the wall. We can see it cutting from anywhere in that room. If I'm running the CNC router, I can leave the door to the shop open and see it from about 50 ft away.


https://www.youtube.com/watch?v=33uWTYtE9SI

Kev Williams
01-22-2019, 6:46 PM
one like this should work dandy, on at 120 off at 105, would require nothing more than a small holesaw--
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it will be very rare IMO that the inside of the cabinet would get to 120 in normal use due to ambient air being drawn in by the blower. These sensors come in many temp variations, and many that are adjustable, you could test actual box temps with any thermometer; if it never gets any higher than 85 in the cabinet, get a 90-on switch, pretty much any extra unwanted heat would be found in short order...

A REAL good place to mount one would be right at the blower exhaust exit--

Rob Damon
01-22-2019, 10:12 PM
Thinking about a couple of these for inside my laser or similar.

https://stovetopfirestop.com/product/rangehood/

It is magnetic so it will easily attach to metal lid.

Scott Shepherd
01-23-2019, 8:16 AM
Universal's also have a temperature sensor with an alarm on them. If the temp raises inside the cabinet, it sounds an alarm. If the 9V battery that runs it goes bad, the machine won't work. If you are trying to make it safer, then looking at what Universal does is probably a good place to start. Metal framed lid with glass and temperature sensors inside the cabinet would get you some level of protection.

John Blazy
01-23-2019, 10:15 AM
one like this should work dandy, on at 120 off at 105, would require nothing more than a small holesaw--

it will be very rare IMO that the inside of the cabinet would get to 120 in normal use due to ambient air being drawn in by the blower. These sensors come in many temp variations, and many that are adjustable, you could test actual box temps with any thermometer; if it never gets any higher than 85 in the cabinet, get a 90-on switch, pretty much any extra unwanted heat would be found in short order...

A REAL good place to mount one would be right at the blower exhaust exit--

Thanks for the reference - will get to it. Great location - near exhaust, inside the hose, or the lower pan where hose attaches.


Oh, mine wasn't little :) Did $3,000 worth of damage to the laser. We put a camera in one laser and it's plugged into a 32" monitor that swivels on the wall. We can see it cutting from anywhere in that room. If I'm running the CNC router, I can leave the door to the shop open and see it from about 50 ft away.
Nice. Need a camera that feeds into my glasses at top corner, like the spy glasses Arnold wore in True Lies.


Thinking about a couple of these for inside my laser or similar.

https://stovetopfirestop.com/product/rangehood/

It is magnetic so it will easily attach to metal lid. That is a great cordless, simple add in conjunction with all these great ideas. Need to do that.

John Lifer
01-23-2019, 8:56 PM
Glass isn't as heavy as you think. My 1300x900 Chinese has tempered glass in both parts of the lid and polycarbonate is within a pound. Opens and closes with no problem. Temp sensor shouldn't go off without a fire unless it is small laser. Probably not a bad idea to put one in.

Gary Hair
01-23-2019, 8:56 PM
I'm not sure a sensor by the exhaust would work out so well as the fast moving air would be much cooler than anywhere else. I think I'd rather put it in a corner where there isn't much air moving instead. Just a thought, could be wrong.


Thanks for the reference - will get to it. Great location - near exhaust, inside the hose, or the lower pan where hose attaches.

Nice. Need a camera that feeds into my glasses at top corner, like the spy glasses Arnold wore in True Lies.

That is a great cordless, simple add in conjunction with all these great ideas. Need to do that.

Larry Frank
01-24-2019, 7:12 AM
Interesting thread and applies to shops without Lasers. Every shop should have adequate fire extinguishers in multiple locations. With a Laser you need even more protection. Shops should have some fire detection system. I have heat sensors in my shop hooked to a monitored system.

I am glad that those with Laser fires did not have total losses. But, it would seem that a lot more needs to be done for fire protection.

Mike Null
01-24-2019, 9:05 AM
A fire blanket would help to contain the damage. I've been lucky--for over 20 years I've not had a sniff of a fire. But I stay with the machine whenever I'm cutting anything.

I have two fire extinguishers in reach.

Kev Williams
01-24-2019, 11:36 AM
I'm not sure a sensor by the exhaust would work out so well as the fast moving air would be much cooler than anywhere else. I think I'd rather put it in a corner where there isn't much air moving instead. Just a thought, could be wrong.
You're right of course that the exhaust air would be cooler, but it would for sure be warmer than normal if a fire is brewing underneath the work, for the exhaust an 80-on sensor should work (assuming a 75-ish degree climate-controlled shop)... And since these sensors are cheap insurance and require only 2 wires and no outside power source, my thoughts are that putting in 2 or 3 sensors would be easy enough; one in a corner, one in the lid, one in the exhaust, $40 and a couple hours work :)

Bert Kemp
01-24-2019, 12:50 PM
Sorry for your loss John I've been there done that twice, first time I was a newbee and left it unattended second time I was sitting right next to it and it stilll caught fire, lucky I was next to it and got it out with out to much damage. I really like that fire stop Idea, but thinking it might give you a reason to walk away instead on watching the cut.:eek:

John Lifer
01-24-2019, 9:05 PM
Wanted to make one more point. Guy on another site posted some pictures of his setup. Had made a box of mdf to capture small rounds that he was vector cutting. Bottom of box was about 2 inches below his cut. The laser was still close enough to deeply char the mdf after cutting through his material. If anything but mdf, it would have caught fire. I could very well see acrylic cutoffs being burned by laser after dropping below your sheet.

In other words, it is very likely that it isn't the laser cutting the main material that starts the fire, but inadvertent burning below.
Just a thought....

John Blazy
01-25-2019, 11:22 AM
Thanks for everyone's replies! Very informative. Ray from Rabbit Laser came by to pick up the laser to take to his shop to work on. He was on his way back from delivering a laser in NY, so it worked out, but I was up til 2AM cleaning it up, vacuuming fire extinguisher dust etc. Nice thing about buying a laser from an importer like Ray, is that he can service it (helps that I am from Ohio like him).

402003

Todd Heide
06-12-2019, 2:11 PM
I'm a complete Newb when it comes to laser cutting, and joined to glean information of the experts. Running across this thread gave me thought. My workshop is in my basement, but I work with flammable materials such as Nitrate and Butyrate dopes, and the associated thinners/reducers. I build RC planes in there, so have a really good ventilation system to pull the fumes out, and have fire extinguishers handy everywhere, but may reconsider where to actually put the laser.

What I was wondering that could prevent this from happening, maybe it works, maybe not, but when welding metal together, especially thin materials, the welds are not done in a continuous line, but rather done a small section at a time, jumping back and forth to keep the metal cool. Could the same be done with the cutting, cut a small section, jump to another point, then come back and maybe cut it in reverse toward the already cut section? Would doing this help alleviate the heat buildup and prevent fires? I know it may take longer to cut, but if it prevents heat build up, would it be worth it?

Bert Kemp
06-13-2019, 12:35 AM
I'm a complete Newb when it comes to laser cutting, and joined to glean information of the experts. Running across this thread gave me thought. My workshop is in my basement, but I work with flammable materials such as Nitrate and Butyrate dopes, and the associated thinners/reducers. I build RC planes in there, so have a really good ventilation system to pull the fumes out, and have fire extinguishers handy everywhere, but may reconsider where to actually put the laser.

What I was wondering that could prevent this from happening, maybe it works, maybe not, but when welding metal together, especially thin materials, the welds are not done in a continuous line, but rather done a small section at a time, jumping back and forth to keep the metal cool. Could the same be done with the cutting, cut a small section, jump to another point, then come back and maybe cut it in reverse toward the already cut section? Would doing this help alleviate the heat buildup and prevent fires? I know it may take longer to cut, but if it prevents heat build up, would it be worth it?

hat type of laser do you have? and what are you going to be cutting with it.
W

Gary Hair
06-13-2019, 5:54 AM
The solution is very simple - watch your laser while it is running.


I'm a complete Newb when it comes to laser cutting, and joined to glean information of the experts. Running across this thread gave me thought. My workshop is in my basement, but I work with flammable materials such as Nitrate and Butyrate dopes, and the associated thinners/reducers. I build RC planes in there, so have a really good ventilation system to pull the fumes out, and have fire extinguishers handy everywhere, but may reconsider where to actually put the laser.

What I was wondering that could prevent this from happening, maybe it works, maybe not, but when welding metal together, especially thin materials, the welds are not done in a continuous line, but rather done a small section at a time, jumping back and forth to keep the metal cool. Could the same be done with the cutting, cut a small section, jump to another point, then come back and maybe cut it in reverse toward the already cut section? Would doing this help alleviate the heat buildup and prevent fires? I know it may take longer to cut, but if it prevents heat build up, would it be worth it?

Kev Williams
06-13-2019, 11:48 PM
I watched a fire about to start in my big Triumph about a week ago. Very interesting- how it happened was I was cutting a crapload of 1/8" w/black Rowmark Ultramatte in the machine like I do about every 3 days. When there's lots of plates I'll have Gravostyle's nesting function pack all the pieces together. GS leaves only about .030" of space between parallel cuts. I was watching while the laser was cutting upward along a previous cut, and I get flareups from the honeycomb occasionally... suddenly about a inch below where the laser had just passed, a flareup lit the leftover sliver of plastic on fire. I just kept watching, waiting for it to go out, but it didn't, the sliver eventually caught he edge of the cut piece next to it on fire. That's when I intervened...

Now that I know the slivers catch, I leave much bigger slivers now! -But I still keep watch, it sure doesn't take much...

Gary Hair
06-14-2019, 6:00 AM
I was watching while the laser was cutting

And Kev reveals the only way to reliably keep your laser from catching fire.

Bert Kemp
06-15-2019, 9:40 AM
I just love it when the newB's come on post 1 question and never bother to return or answer question or even find out if we were a help. guess they don't want to become contributors :(

Glen Monaghan
06-15-2019, 1:44 PM
Jumping around on the cuts definitely helps reduce the fire hazard, albeit at the cost of taking more time.

I cut some snowflake ornaments from 1/8 clear and white acrylic a couple of years ago, with the cut file optimized to reduce head movement between successive cuts and minimize cut time. The design was pretty intricate with lots of small cutouts closely spaced, so the laser spent a lot of time in the same area cutting out small sections and leaving sort of a spider web skeletal snowflake shape. After a couple of flare-ups, I turned on the air assist and thought that did the trick. However, as the laser finished cutting one snowflake and went to the next, I noticed the surface of the just-finished snowflake starting to bubble and then saw a shimmer. At that point, I raised the lid to stop the beam and grabbed the squirt bottle. As I started to spray the area, the clear acrylic was definitely bubbling and I could see a faint flame.

Leaving on the paper mask, using air assist at a higher pressure, and de-optimizing the cut sequence so that the laser jumped around the design to let each cut cool as much as possible before cutting again right next to it, all contribute to not having any more fires cutting these designs. I don't recall the difference, but all the jumping around made a significant increase in overall cutting time, which I find preferable to catching fire...

Todd Heide
06-18-2019, 1:55 PM
hat type of laser do you have? and what are you going to be cutting with it.
W

Don't have one yet, and it will mainly be balsa and plywood for starters, then maybe once I get the hang of the software, other things like engravings. Still working out details of what to get, how much to spend, and what fits etc.

I think you posted in my starter thread too. Thanks.

Bert Kemp
06-19-2019, 9:41 PM
Don't have one yet, and it will mainly be balsa and plywood for starters, then maybe once I get the hang of the software, other things like engravings. Still working out details of what to get, how much to spend, and what fits etc.

I think you posted in my starter thread too. Thanks.
I meant is it a co2 or a fiber. Sounds like your looking to get a co2 tube laser.Engraving risk of fire is pretty low but cutting balsa even jumping around I would never leave it un watched. Balsa is very flammable, Plywood also don't leave it unattended just asking for trouble. :rolleyes:
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