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Doug Griffith
01-25-2017, 1:07 PM
I was cutting a job yesterday from 1/16" thick Delrin and it caught fire. First it flared up and dripped beneath the grate. From there, it caught fire beneath the grate and fed itself from the dripping sheet above. This all took maybe 10 seconds while I was standing next to the laser looking a different direction. The first thing I did was open the lid and attempt to blow it out with my mouth but all that did was feed the flame with more drips. 2 seconds later, I reached down and grabbed the CO2 fire extinguisher that's been sitting there for about 10 years and gave it a tiny blast. After about 15 minutes of cleaning the melted Delrin from the grate and changing out the aluminum foil I keep beneath it, I was cutting the job again. Luckily, there was no damage to the laser except some slag stuck on the grate. I'm surprised because the flame was well above the grate and about 6" in diameter. Having a powerful fume extraction system probably helped here beause the flame was going sideways towards the exaust ports.

So... had I not spent the extra hundred bucks or so way back when, I'm sure the damage would have been pretty ugly. Being that it was a CO2 fire extinguisher made for very little cleanup and allowed me to immediately move forward with the job.

If you don't have a fire extinguisher next to your laser, I suggest you do it now.

I also keep another about 20 feet away by the door in case things get out of hand.

John Lifer
01-25-2017, 3:48 PM
yes, one is sitting 4 ft away,good thing you were close by! but what else did you learn about delrin? and it applies to all thermoplastic materials and lasers!

not trying to be nasty, btw.

Doug Griffith
01-25-2017, 4:31 PM
I've been laser cutting plastic for 10 or so years now and never had an actual fire. Just typical flare-ups and smoldering MDF. I didn't really learn anything except that Delrin is more flammable than I thought and not self extinguishing. It WAS my favorite material to work with until this happened.

Tim Bateson
01-25-2017, 4:34 PM
My Insurance forces me to have two extinguishers... and that they are certified annually. Have not used one yet, but like you, glad they are there... just in case.

Bill George
01-25-2017, 5:32 PM
I tried to purchase one locally but only the commercial places for industrial use sold them. Got one off Amazon and to my door I was pretty reasonably priced. Yes I have used CO2 in real life in working situations and it sure saves a lot of clean up work.

Mike Null
01-25-2017, 6:20 PM
Mine are ready to be replaced which I will do today. Thanks for the nudge.

Kev Williams
01-25-2017, 6:21 PM
While honeycomb tables are okay, I'd much rather do my cutting on my solid-top tables...

All 3 of my solid table machines pull air from the back of the machine, right at table level. So there's always a good flow of air right across what you're cutting. Add a LITTLE air assist, and the fact there's very little air under what you're cutting and it's nearly impossible for a material fire to get out of hand. (nearly ;) ) -- I've had some loose transfer-tape catch fire a couple of times, but with no air below to feed it, the air assist and blower airflow simply blow the fire out. Any plastic I've seen flare just goes out.

Not so on the Triumph with the honeycomb table. Plastic tends to stay on fire once it starts... With the exhaust below the table and what I'm cutting being in the way of the airflow, the air pulled into the machine above the table just feeds the fire rather than put it out! I have my air assist tube disconnected from the valve, so it's just the bare 1/4" tubing, and I let it run full blast while I'm cutting just because it will blow out flare ups. Most of the time. ;)

John Lifer
01-25-2017, 6:43 PM
Yep, it is flammable and keep your power down to the bear minimum. Melting plastic is not only dangerous because of the fire, much of it will release VERY toxic fumes.
Things such as Polycarb will smoke you out of a building quickly if they catch on fire.
Other than that, I'm being a smart ....


I've been laser cutting plastic for 10 or so years now and never had an actual fire. Just typical flare-ups and smoldering MDF. I didn't really learn anything except that Delrin is more flammable than I thought and not self extinguishing. It WAS my favorite material to work with until this happened.

Bert Kemp
01-25-2017, 7:10 PM
that reminded me to check mine, its a dry chem but I keep a spray bottle on the laser also. Hopefully I never need either again.

Doug Fisher
01-25-2017, 9:25 PM
I have had to clean up a dry chemical extinguisher before. It is NOT fun. FWIW, www.Zoro.com had the best price (as of the first of the month) on a 2.5 lb Buckeye halotron (no white powder) extinguisher once you factored in what others charged for shipping and the fact it was actually in stock.

Doug Griffith
01-25-2017, 10:16 PM
I hate to bring it up but 12 year olds using a GF in the kitchen crossed my mind. That machine has a grate as well.

Wilbur Harris
01-25-2017, 11:15 PM
Bert - bite the bullet and get a fire extinguisher that won't goof up your laser. You can always grab the dry chemical deal as a last resort.

Joseph Shawa
01-28-2017, 11:01 PM
I always have an opened beer ready just like I do at the BBQ. :D

John Blazy
01-28-2017, 11:48 PM
While honeycomb tables are okay, I'd much rather do my cutting on my solid-top tables...

All 3 of my solid table

Hey Kev, What are your solid tables made from? corian seems to be a good choice. Something that ablates a bit, doesnt warp or catch fire.

Kev Williams
01-29-2017, 2:07 AM
They're all aluminum. The LS900 table is 3/4" thick, but the actual aluminum is .062" thick, formed over a corrugated core. The hollow core allows for the blower to vacuum smoke from UNDER the work... The ULS table is 1/2" thick I think, and it's solid. The GCC is approx. 1/4" thick, with approx. 1/2" x 3/4" alum. bars running lengthwise as support, spaced about 3" apart.

Flashback on the bottom can create problems, especially cutting plastics, but I've found using wet paper between the table and the material helps a lot with the flashback. I just lay paper down and drown it with a spray bottle. I save all the large format blueprints my customers give me with their parts just for this reason ;)

In case wet paper won't work, I have a LOT of small lockwashers for #6 screws, I'll just pour out a bunch from the jar and spend a half minute spacing them out. They provide about a mm or so of space between the material and the table, which might as well be a mile, because once the laser hits the aluminum, it's done, no flashback other than the occasional tiny bits from the lockwashers-

John Blazy
01-29-2017, 6:07 PM
Sweet pc of info - thanks. I will try some alum plate - doesnt hurt to try

Tim Bateson
01-30-2017, 11:02 AM
While honeycomb tables are okay, I'd much rather do my cutting on my solid-top tables...

I use the Seklema Hold Down Mat from JDS for about 99% of my Rowmark cuts. Great product. Most of the time I really don't cut completely through anyway. Just enough that the Name Plates fall apart.

Bruce Clumpner
01-30-2017, 5:27 PM
Here's a good deal from the mighty Amazon... 5lb Co2 with free shipping in US... $128
https://www.amazon.com/gp/product/B009WUGO9A/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A3UH5POVVBAKR8

Brian Leavitt
01-30-2017, 6:01 PM
Just had ours re-certified earlier this month. :)