Spoilboard Fire

[gene]

I had a small fire on my bot and need help to keep this from happening again. What happened is when the bot slows to cut around a corner it all but comes to a stop, with a blower pulling a vac it dont take but a second for the bit to get very hot, i know there is a way to speed this up ,but i cant seem to find it anywhere . I have spent hours going over old post and must be looking over it . i am glad i only stepped out of the shop for a few seconds or this could have been much worse. Thanks for the help..

[bleeth]

Gene it sounds like either your xy ramp speed or your slow corner speed is too low.

[elcruisr]

Gene, spoil board fires can happen, even with big machines. Normally this only happens during a malfunction and the feed stops while the tool is running.

What are you cutting, what kind of tool, feed speed and tool rpm? Is the tool really sharp? If that's in line then software tuning is the next step.

I've had two fires from hitting trash in particle board that wrecked the cutting edge and caused so much heat from the dulled tooling we started a weenie roast.

[harryball]

I've never had an official "fire" but I've had a few instances where things started smoking. Once while cutting my little bats I forgot to change the spindle speed to 12k instead of 18k. In every case it has pretty much been my fault so far.

I agree with Dave, I would be interested to see how your ramp and slow corner speeds are set.

Robert

[gene]

Dave ,
What is the setting for the values and how do i find the place to change the corner speed ? now the values are set at .4 down the list .
Eric,
I was cutting 3/4 plywood at 12000 3/4 depth at 6 ips the cutter has only a few sheets on it and is a 3/8 frued upcut spiral . it feels sharp . All the settings are .4 with the 3d at 100 , the minium dist to check at .15 and the slow corner speed at 65, Thanks for the help ...

[bleeth]

Gene: Those are factory settings and you shouldn't be generating that much heat at that speed and rpm (I would probably be using a higher RPM). Now it is starting to sound like some "pitchy" ply or the bottom of the bit is dull. You could be dulling that part of it by plunging too aggressively if you are doing the whole 3/4" in one pass. I've never used Freud bits on my bot so can't really comment on how good the carbide is for cnc use. For that kind of aggressive plunging and cutting I do use solid carbide bits designed for it from Whiteside, Onsrud, Centurian or Guhdo. Many standard carbide tipped router bits don't cut across the whole bottom as they are not designed for plunging and that would definately create a bunch of heat. Hope this helps. You're settings have eliminated the easiest most obvious answer.
Dave

[tomb]

Gene: I would like to thank you for starting this thread. I have needed a new extinguisher for some time next to my router and used this as an inspiration to go buy a new one and mount it. How many other of you guys are putting off getting an extinguisher??

[harryball]

I have 2 extinguishers mounted in my shop and a total of 12 in the house. They are all the larger ones, not the tiny ones. I also have them in the vehicles. All of us, kids included, have practiced using one. Why so paranoid you may ask? I've experienced fires in various situations and a good fire extinguisher is a good idea. If you don't have one... get twelve.

I've used Freud bits in the past, I personally consider them over priced, over hyped and of medium to low quality. I think its been over 2 years since I've touched one.

Robert

[gene]

Robert
I have drawn the same conclusion , the bit form frued is a 3/8 solid carbide and was about 35.00. I dont think i'll be using them anymore . I tryed their 3.25 hp routers in the past and smoked two of them within 25 minutes combined, and this was NOT on a bot. it was on a legacy mill machine. Also you can not ever have too many fire extinguishers..Thanks to all

[jamesgilliam]

I agree on the extinguishers and have a couple in the shop and one in the truck. Also joined the local volunteer fire department so I know they will show up if it is bad enough.

[elcruisr]

First off let's hear it for fire extinguishers! I have twice the capacity in my shop that the fire code demands. Then I added a 15 lb CO2 on the Shopbot frame. CO2 is much kinder to equipment than dry chem and there's no residue to clean up. Just make sure it's big enough to do the job. I know it's not rated for wood fires but a good sized one will due the job if you do yours, trust me!

As for tooling I won't touch Freud tools or sawblades any more. They just don't have the quality they once had years ago. Make sure your tooling is designed and balanced as a CNC tool from the get go and you'll have much better luck. Also, sharp means if I drag it across my finger nail the edge tries to "bite" not just slide across.

I wonder if you are by chance cutting import core plywood? I refuse to cut it any more. It destroys tooling at an amazing rate and I hit so many pieces of steel and other tool destroying trash that it is now banned from my shop. The only exception being Arauco and Elliotis. Two south american cores that have proven to be stable and safe. NO CHINESE OR INDONESIAN! An incident with import core plywood burned a 1' diameter hole in my spoiboard before my operator got the machine stopped and we extinguished it.

As for the variables under the "VR" command I have tweeked them to do a better job of cutting my typical parts order which is usually complex shaped small to medium sized parts nested into full sheets using a "Single Sheet" material strategy.

Move ramp speed .4
Move ramp rate .235
3D Ramp threshold 750
Min distance to check .13
Slow corner 40

Cutting nothing but cabinet parts might change these settings some as would extensive 3D work. I typically cut poplar core 3/4" ply in a single pass at 18,000 rpm with a feed rate of 7 to 8 IPS with a single flute compression spiral. Another very good choice is a single flute polished O flute up spiral.

[bcammack]

Fire extinguisher -> car = good idea.

As a journalist once wrote: "There's nothing worse than watching your $30,000 car burn to the waterline because you didn't have a $12 fire extinguisher with you."

[bob_lofthouse]

Fantastic post by Eric...

Changing my variables solved my issues. Until they were changed I had the same problem you have but 10 times a day on 3 machines.

I have to cut the chinese and have discovered the weirdest stuff in the wood however I always found that the spoilboard went first before the wood.

On my worst day I lost the filter from my vacuum setup.

Where possible on my products I try to put a radius in slightly bigger than my cutter rather than using a 90 degree corner so that the machine doesn't come to a standstill in any point.

Be careful using a CO2 extinguisher in a non ventilated enclosed space...

[gene]

Robert
Where did you find the settings to slightly round the corners,

[bob_lofthouse]

Hi Gene,

In partswizard we used fillet vector with an arc..

[elcruisr]

Robert, have you checked if the Arauco product is available in your area. It's not much more than the chinese stuff here and vastly better. Many people here are switching over. One local importer is starting to bring in a south american product with an okoume face that the furniture guys are warming up to but I haven't run any yet.

[harryball]

I'm cutting Arauco 1/2" ACX. For the most part I'm pleased with it but I find that the C side often more closely resembles what I'd call a D. Out of 20 sheets all have surface voids and at least 5 had vast surface voids. One was completely unusable, about 30% of the C face was missing.

Robert

[elcruisr]

I think we're getting AB and AA here. It's pretty good for the price. Don't think I've seen the ACX. Even with the elliotis ply you never want the c/c-. Looks like what we used to call CDX 15 years ago. The c+/c is good for upholstered furniture parts though.

Ahhh, the never ending search for decent plywood. Surely shooting at a moving target isn't it!

[harryball]

My 1/2" ACX is $24/sheet. The only AB grade I can find is Marine Ply and I can't use that 1) it costs about $50/sheet and 2) it has chemicals in it that would harm the bats.

I've never been successful finding just Exterior (not Exposure) grade AB.

Robert

[elcruisr]

I see your point! I believe this stuff here is an interior grade. AB exterior, that's a tuff one! Most of the marine grade stuff I've seen in the last few years hardly meets the true marine grade standards I was used to in boat building 20 years ago anyways. Just win the lottery and buy your own press?