Close call today, CNC fire

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Marcel Thibodeau
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Close call today, CNC fire

Postby Marcel Thibodeau » Fri, Apr 06 2018, 1:07PM

Ok, I was cutting some 3/4 euro ply today(the really densely layered stuff). I was cutting 30 inch circles with a 1/4 inch hole in the center. The entire cut took less than 2 minutes. When the CNC machine drilled the 1/4 inch hole the combination of the friction and the pumps drawing air through the hole caused an ember to ignite and CATCH FIRE! Unbeknownst to me, I was going about my routine, turn the dust off, turn the pumps off and clear the table. Clearing the table I was flipping each piece of plywood over to inspect and low and behold on the final piece there was a 3" scorch mark, I look down at the table and it had burned a 3" hole right through my spoil board and partially into my tableboard. I was in complete disbelief, I cleaned everything up, changed the 1/4 cutter, repaired the table board and resurfaced everything. I cut one more piece and stopped the machine immediately after it drilled the hole, looked down inside and could see a glowing red ember, (kinda gross) but i spit into the hole and finished the cut, no damage done.

I was thinking after that its not entirely uncommon for us to finish a sheet and then have lunch or coffee before clearing the table, sometimes leaving the shop as we do every friday. I could have lost everything. From now on its policy to clear the table and be EXTRA diligent when cutting that euro-ply stuff, small incident but gave me a slight scare so i thought I would share it.

I think it was a combination of the dense plywood, which has like a fiber stringy stuff in it, and the pumps drawing air though the hole, go figure.

tim lucas
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Re: Close call today, CNC fire

Postby tim lucas » Fri, Apr 06 2018, 6:58PM

Had it happen to me also, while cutting regular plywood a small part came loose, it rode the bit up and stayed with it while trying to cut the next part. It didn't take long and we had a 2 inch hole burning embers. Had a bottle of water near by, shut everything down and put it out. Can't leave those bots alone they will burn down everything.
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Mike Murray
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Re: Close call today, CNC fire

Postby Mike Murray » Thu, Apr 12 2018, 11:09AM

Hit a nut imbedded in PB one time, got a good fire going....Be careful! My biggest fear is a spark getting into dust collector pipes.

Tommy Wieler
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Re: Close call today, CNC fire

Postby Tommy Wieler » Thu, Apr 12 2018, 2:01PM

Mike Murray wrote:My biggest fear is a spark getting into dust collector pipes.

Especially if its a central dust collection system. Not only will the collector need repair, but you could also potentially be dealing with smoke damage throughout the entire shop... and water damage from the ensuing efforts to douse the fire. We installed a kind of trap door on the main air return outside the building so if we ever have a collector fire, we can run out and swing it open to at least keep most of the smoke out of the shop.

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Jeremy Schiffer
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Re: Close call today, CNC fire

Postby Jeremy Schiffer » Mon, Apr 23 2018, 10:55AM

I've done the "spit on the burning wasteboard" thing too...anything to stop that fire! Curious as to why drilling the 1/4" hole would cause it though, are you using a compression or downspiral bit for that op?

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David Giesbrecht
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Re: Close call today, CNC fire

Postby David Giesbrecht » Thu, Apr 26 2018, 3:21PM

We have had the same issue at one point. Ours was using the 1/4" to pocket the hole instead of the drill bit to drill. That was before we started using tool groups designated to the material. I believe there is a setting in the tooling to only drill a set depth than come up to clean out. If you are using material groups you don't have to waste that time when drilling melamine. For those that aren't familiar with material groups you can setup the machining speeds and tool and tool operations specific to a certain material, then whenever that material is loaded it will use those parameters.

Glad everything was OK!
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