Note to self… Lasers are dangerous!
I made the mistake of walking away from the machine for 5 minutes while it was cutting. Don’t repeat my mistake.
feel sorry for you.
As everybody in the community, we are playing with fire.
Don’t leave a working machine unattended.
Gutting, was the machine destroyed or is it cosmetic.
@Anthony_Santoro That’s extremely unfortunate. What exactly were you cutting at the time? Could it have played a role in the destruction?
@Tony_Schelts Looking at the second picture, it looks pretty done!
WHAT happened here ? Your workpiece catched fire ?
I was cutting 3mm acrylic sheet. I was planning on making the cut in 3 passes. After the first pass I opened the lid to take a look, all was okay. Second pass started, I walked away, returned and there was smoke everywhere! I quickly hit the safety switch and sprayed the fire with an extinguisher that I had close by.
The machine is toast. I can probably salvage some parts, but for the most part it’s scrap. My saving grace was a 6mm ply sheet that I sit atop the cutter during cutting, if this wasn’t there then the flames would have come out of the machine and onto the rest of the equipment in the room.
I actually don’t know what caused the fire, I’m guessing maybe the acrylic got too hot and became alight. I don’t have another explanation.
@Anthony_Santoro Possibly the fumes off the acrylic were flammable & not being extracted well for some reason?
edit: I just found that the fumes are a fire hazard. -Fire and explosion hazards:
Heated material can form flammable vapors with air. -
http://www.alro.com/datapdf/plastics/plasticsmsds/msds_plexiglasg.pdf
Also, cutting acrylic needs an air assist to blow down through it, or it will ignite at the surface layer. Did you remove the paper/plastic backing on it?
I am truly sorry for your loss. The best lesson learned here is that you kept a fire extinguisher close by. I am sure it could have been much worse without your quick thinking and keeping the correct safety equipment handy.
This is unfortunate. However, thank you very much for posting your pics and your story here for all to see.This is a good reminder of the danger this machine can be.
Take out the electronic partition and rebuild the gantry with Openbuilds vslot and a linear actuator… you can “re-make” the machine to have an approx 200 X 500mm cutting area
Huh. First: sorry for that. Second idea: could a smoke detector and better, any kind of temperature-activated switch have saved your machine? I feel like it may not be that hard to detect such issue, shut everything down and switch an alarm? Now… I have read that some K40 do not even come with a switch on the lid 
Hindsight is a wonderful thing.
I think I will use the machine structure to rebuild something bigger and better!
I have a spare machine, so I will use that for the standard cutting (once the useless supplier provides me with a replacement for the faulty tube), then use the burnt machine as a project machine.
Air Assist has saved my butt many times. It doesn’t take much air to blow out any fires started while cutting. I also keep a spray bottle handy to shoot spreading ember burns – balsa does it quite a bit. I drilled some 7/8" “gun ports” on the front to stick in the spray bottle. I have gaff tape covering the holes as little lids to break sight lines… They also help with the air extraction since they help pull the smoke to the rear across the work table. I covered up the big hole in the bottom, piece of plaque AL sheeting, then gaff taped that to the bottom. 1/2 conduit hole saw with carbide cuts the 7/8" hole.
My solidarity my friend, hope you can overcome this setback as soon as possible LUCK.