OK, now that I have everyones attention let me tell you what happened. I clamped a glued up table top to my CNC to flatten it. I routinely do this after glue up because its no handling of a large top to flatten after gluing. I use a 2" diameter shell type cutter (or a fly cutter) to accomplish this. I create a simple pocketing tool path slightly larger than the workpiece and take very shallow passes until Ive flattened the entire surface. typically, running the same program stepping it deeper into the material until Ive cleaned up the entire face. all the while, I have a dust boot over the cutter head with dust collection running. The top I was running was running was made of aspen. Aspen is considered a soft wood and tends to get stringy when machining it. The dust boot is just a sheetmetal box that encloses a cavity over the cutter that has brushes that crush to the mating material to create a vacuum seal. Tonight, on my second pass, unbeknownst to me, the stringy material was building up under the dust boot around the cutter starting getting tangled in the brushes. As I was watching it run, I suddenly noticed a spark fly up the DC hose (4" corrugated semi clear hose) , then before I could react, the hose was glowing orange for about 12" up inside!!!!. I slammed the E stop button the CNC and was scrambling for my DC remote control, which was in my pocket to shut it off. The dust boot has a hinged door you can open to inspect and I opened it before the DC had even begun to spin down and saw flames being fanned by the DC air so I pulled the hose off the boot and it went out, but now I was unsure as to how much burning material could have possibly made it to my DC in the next room. Scrambling over there, disconnecting the barrel and the saw dust bag from below the filter, I did have some very hot saw dust in the main bin, but nothing on fire or glowing thankfully. This all transpired within probably 30 seconds time. It happens fast and scares you after the fact when you can imagine the what ifs. I do know I need more than one fire extinguisher, it was way at the other end of the shop 70 plus feet away through a gauntlet of tools, lumber and projects to get to. Stay safe my friends!
CNC FIRE!!!!
- Thread starter chris_goris
- Start date
Eye opening story! Lots of things to think about from CNC isn't start and forget to putting additional extinguishers in places with flammable materials like the DC. Probably took a while before your heart rate was back to normal!
Absolutely!
Scary indeed. Having had a recent electrical fire (incoming main stud arc with loose wire connection) in my breaker box) these things can and do happen even with the best vigilance). Glad things turned out well for you. And thanks for getting this thread going.
Might help, but it just makes more sense when running larger cutters to just go without.
My dust shoe top is clear acrylic and I could not see the stringing inside the shoe.
Maybe since I was cutting Hickory and the pieces where fairly stiff and wanted to stick completely outside the shoe.
Youre right Ray, I dont remember any threads on here about fire safety in the shop. I hadnt really given it much/any thought to this point.
As I mentioned earlier... no more dust shoe when planing!
Shop fire threads seem to usually be about self-combustion of finishing rags. This is the first that I have seen about fire in a CNC. Thank you for sharing and I am very glad that things worked out well for you.
Thanks Ivan! I actually know another person this had happened to but we had never discussed it, nor had I heard of ti until it happened to me. His was basically the same scenario.
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