Fire detection and suppression

[coryatjohn]

I am concerned that my new ShopBot will burn down my house.

I have an idea on placing smoke detectors in the exhaust path of my vacuum hold down and dust collection systems and wire them to shut down power to the ShopBot and vacuum systems in the event that smoke is detected.

For suppression, I was thinking of adding CO2 bottles that will flood the ducts of the vacuum hold down when smoke is detected.

Does this sound way overboard? Does anyone else have something along these lines?

Thanks.

-John Coryat

[chiloquinruss]

Sounds a little overkill to me. There are thousands of ShopBots and many more brand 'X' machines out there and I have only heard of a few fires. That is not to say don't be cautious by all means, just I think what your are proposing is just a bit over the top. I have four extinguishers in the four corners of my shop and one under each end of the Bot. I don't go in the house when the Bot is doing a job (I never leave completely unattended). When I'm working in my adjacent office I have a video monitor setup to watch what's happening. I sweep on a regular basis and don't have a great deal of sawdust, but some. Russ

[zeykr]

If you do a search here for 'smoke detector' you'll find a number of threads on the subject going back to a least 2005. Don't think anyone's ever found an ideal 'automatic' solution.

Most smoke detector work by detecting particles in the air that are part of smoke, unfortunetly fine wood dust is nearly indistinguishable from smoke particles rendering most detectors unreliable for use in a wood shop, let alone in the vacuum system. When I installed my alarm system in my shop, we put in heat detectors in the workshop portion as they told me normal smoke detectors would give false alarms.

Doesn't hurt for a new set of eyes to review whats new in the smoke detection field every so often though as something workable may come along. If you find something that works, I'm sure many here will be interested.

[Brian Harnett]

I stay in the shop while mine is running and have fire extinguishers in the shop for general safety. Been running mine for ten years without an incident.

There are plenty of good reasons not to leave the bot alone.

[dana_swift]

@John

Automatic suppression is not needed.. What I do is make sure I have two fire extinguishers around. Grinding is much more likely to start a fire than routing.

The risk with routing is that the gantry will stop but for some reason the router/spindle doesnt. If this happens when bit is in a hole deeper than the CEL fire starting becomes a real possibility. Routing in normal channels does not seem to be very risky. I have had the above scenario happen and it just sits there and spins, no smoke.

I have had too aggressive a cut on a drill toolpath without adequate chip retract clear cycles.. smoke has happened, but never flame. Drill toolpaths get a little extra supervision as a result.

In roughly 6 years of operation I have never had a fire, nor felt like anything close to ignition was occurring. I have used the emergency stop to kill the router/spindle when it is in a cut and the motion has stopped.

Get a couple large extinguishers, and that should do.

Good luck, expect to make much sawdust, some broken bits, and no smoke.

D

[coryatjohn]

The thing that really concerns me is that my shop is attached to the house. It's off the garage (we have a U shaped house) but shares a roof with upstairs gameroom. If a fire started in the shop, it would probably take out the entire house.

I have a cyclone type dust collector with a HEPA filter. Wouldn't that screen out any dust that might cause a false alarm in a smoke detector? The vacuum holddown also has a filter and there (in theory) shouldn't be any particulate matter entering into that stream.

From what I've read, a fire can quickly get out of control with all that air circulating around. A total shutdown of all systems when smoke is detected would certainly slow that down some.

It might never happen. It might happen once in ten years. If it happens ever and I can't stop the fire in time, it could be a life changing (or ending) result.

[coryatjohn]

I found this to be interesting:

http://www.slideshare.net/odinhuang/smoke-detection-in-challenging-environments

This image looked useful:

http://usnaviguide.com/shopbot/fire-detector-filter.png

[gene]

Hey John,
I think that you are thinking overkill. I caught my bot on fire but i was right there when it happened . All i did was dump a biggie tea on the spot right after i shut off the vac hold down . as long as you do not leave the machine runnung unattended you will be fine with 1 or 2 fire extinguishers , Thats what i keep in the shop as well as others that do the same . It isnt like it bust into raging flames immediately , it starts slowly but it unattended could grow fast. Are you new to the shopbot family?

[Brady Watson]

John,
Get an appropriate fire extinguisher and NEVER leave your running CNC unattended. Ever. Problem solved & everyone can sleep well at night.

-B

[gerryv]

If it's an open, common attic, there would be an advantage to adding a firewall(s) between the shop and other sections. The drywall and studs would not be that expensive and no need to paint. That's typically done in multi-occupancy buildings to safeguard against what you're concerned about - well to slow it down a lot at least.

[coryatjohn]

"Never ever leave it running"

That's a good idea but the problem is I am a human being with lots of failings. I know that I'll be lulled into complacency and leave the machine humming along and go do something else. That's just human nature.

It seems a low cost precaution to have at least a system shut down when fire is detected.

Here's another interesting link:

http://www.gaumer.com/Resources/PDF/detect_a_fire.pdf

These heat detector units are about $100 each and are simple switches. They aren't sensitive to dust, humidity or other things that might confuse a standard smoke detector. They are used in ducting and places where there is a rapid airflow. Seems like this would work.

[Bob Eustace]

John, we learnt early on thru the smoke Dana mentioned is to NEVER drill the same size hole as the bit using downcut end mills. You could put your dust collector outside the house and use an auto sprinkler over the canister. We have a dedicated fire hose next to ours. We also have a fire hose 15 foot from the bot as well as extinguishers. One good idea though is we have shut down switches behind the bot but more importantly well away out in the workshop as well, so you can quickly turn the thing completely off. Reckon speed is the most critical thing in any fire. Was involved in two shocking fires in the optical industry during my apprenticeship and it is still quite vivid 60 years later!!!!

[tomwillis]

John - peace of mind may be worth the investment. I say, if you have the money, and will sleep better - go for it! I ve had my bot since 2005 and have had numerous fires. Once - my laser burned right thru 3/4 ULDF spoilboard and into my phenolic top and set both on fire. Fortunately - I was there when it happened and was able to quickly put it out. Mine is my garage which is attached to the house and would have probably burned everything to the ground. Even now, after all these years when I have a long file running - I enjoy watching it and being nearby. Leaving it unattended is usually not wise and those lessons are learned the hard way. my 2 cents...anyways.
Tom

[coryatjohn]

@Thomas - Not only peace of mind for me but for my wife as well.
@Bob - Thanks for the suggestions. I can't put the DC outside due to noise issues. I have good neighbors now and want to keep it that way.

I'm going to get the heat detectors and plant them throughout the system. A few bucks spent in prevention will be worth it.

[myxpykalix]

John,
It never hurts to be a little paranoid. However the flaw in your design description is that if a fire starts it will be inside your table and not inside your dust collection hose.
A failsafe shutdown of all systems wouldn't be a bad idea because like they say what is going to feed the fire is the airmovement of your vacumn system or dust collection.

I don't know if there is any kind of heat sensor that you could imbed into your table or attach underneath that might give you a warning.

This is one reason that i don't use my vacumn table and don't use dust collection much (except when i cut mdf).
Most of my cuts are usually .125 ballnose finishing 3d cuts that don't really generate a lot of heat and i usually don't stay in the shop watching a 6 hour cut file. I have a security camera that is always on when i'm cutting and watching my favorite shows....:rolleyes:

[Brady Watson]

"Never ever leave it running"

That's a good idea but the problem is I am a human being with lots of failings.

Attach a red lanyard between the E-stop & your belt, just like a kill switch on a JetSki.

Problem solved. :D

See? Saving you money already!

-B

[donek]

Wow. 14 years with a bot, vacuum hold down and dust collection and never had a single incident where I even considered fire an issue. Maybe its the fact that I've never enclosed my vacuum hold down motors.

I have had a shop burn down, but it was completely unrelated to any piece of woodworking machinery. Sharp bits aren't likely to start a fire unless you cut at speeds that make no sense. Dull bits on the other hand are potential problems, but they also waste material and your time. Suck a wire through your dust hose and you minimize static. In most cases preventative measures are more effective than systems that attempt to fix a problem after it occurs.

[kubotaman]

John, I have talked to you on the phone. I wish you had mentioned your feelings in regards to the possibility of fires caused from your new Bot. I personally spent the best part of my 30 career dealing with fires. Personally I feel there is a very slim chance of fires caused by your new machine. It's possible but I wouldn't bet on it. There is a lot of years that men have here and most if not all have given you very good advice. If you feel it necessary to address this issue then by all means protect yourself and family with a system which would include heat detectors. Smoke detectors will be usless since they will sense the dust in the air which will set them off. Remember that the heat detectors will have to also be included in your home system since they will then be able to alarm everyone in the home and not just the shop! Think safe and don't be careless and you will be more than fine!!

[coryatjohn]

@Daryl - Great advice. Thanks.

[Regnar]

They do make unmanned fire estinquishers that can be ceiling mounted and wall mounted.

http://www.youtube.com/watch?v=3OOUEZuTvZQ

[cabnet636]

listen to Brady

[Simops]

They do make unmanned fire estinquishers that can be ceiling mounted and wall mounted.

http://www.youtube.com/watch?v=3OOUEZuTvZQ

Hey what a neat system.....not just for CNC machines but more so for the workshop in general......even in Homes :eek:

[benchmench]

As Dana Swift mentions, drilling operations can be firestarters if retract, tool depth along with speeds and feeds are not managed well. I will usually switch to an upcut bit if I think there will be a chance of excess friction.

[cabnet636]

at first I got all excited when I saw this single suppression system then I remembered that my entire shop is sprinklered,, still have no business letting the cnc run un attended, now i'd be lyin if I say I don't walk away once in a while, but not far and having caught mine on fire I should still know better...

[feinddj]

Watch your tool work. Don't leave the shop unattended while it is running.

Ground your dust collector. Where I live it is a fire dept regulation for all dust collectors and air compressors to be inspected by the fire dept and tagged.
Keep your shop clean. Nothing can prevent an accident from starting a fire, keeping the fuel away from the ignition is entirely preventable. That means cleaning up sawdust and not storing flammables such as the gas for your mower in the garage.

Most building codes require 5/8th drywall between a garage and living areas. For your purposes, a cheaper way to safeguard the rest of your house is to make sure that you do have at least 5/8th of drywall, and consider adding another layer to walls and ceiling. This will increase the time it will take for the fire to spread.

Talk to your fire department. Their job is to put out fires but they would much rather prevent them.
David

[myxpykalix]

I always watch my machine on rough cuts whether on the table or indexer. I do leave the machine when doing long 3d finishing cuts using a .125 ballnose taking a light cut.

[dana_swift]

A follow-on comment regarding normal operating temperatures. John, there may be an impression that the shopbot doing ordinary cutting generates a lot of heat. That is not so.. when you are operating the machine correctly, after is STOPS, you should be able to put your fingers on the bit and it will just be warm. The chips during cuts are just warm to the touch.

Things getting hotter than that are a sign that things are going wrong. Routing is a "cool" process, unlike milling which is a "hot" process.

As your experience grows, you will discover that anything hot is a strong hint to do things differently. Heat eats carbide- hot bits break. Broken bits happen when the heat dissipation has not been done correctly. What we perceive as "pushing too hard" is really making the bit flex and build up heat until its strength plummets. A broken bit is usually a symptom of a heat problem. The bit breaks before a fire starts. A thermal "fuse".

Yes things can go very wrong, and as people have pointed out, they have seen things go very wrong. But the big risk to me is not fire. Its getting my fingers in the way of the bit. Or pulling muscles somewhere when handling materials. Or dropping something on a foot. Something not held down well enough flying out and causing injury. (Rarely happens, but much more often than smoke), etc.

When things go wrong, I have messed up. The machine just does what I told it to do. ShopBot has done an amazing job of building machines that work correctly, unfortunately they sold one to me, and the biggest safety/reliability problem is visible in my shaving mirror.

After you have used your bot for a thousand hours or so, I would love to see if your position has remained the same, or you wish, after looking back, that you had spent the money on steel toed shoes, hearing protection, or other safety equipment. I do agree however a fire extinguisher is mandatory! The risk is not zero.

Keep us posted, I for one, am glad to have the chance to review my fire safety precautions and think again about this issue!

D

[cabnet636]

Dana,

as someone who has an almost perfect slice thru the center of his thumb (Twice, same thumb,same saw, same person standing within ten feet of me) I really appreciate your post !!!

[coryatjohn]

I agree that fire is a low probability. The problem is my shop is in my house. A fire can lead to a catastrophic loss. The ShopBot and the associated systems (DC and vacuum hold down) have three elements that can lead to a large fire quickly: A source of ignition, fuel and flowing air. Those three things can cause a minor error to destroy life and property.

I'm adding a few hundred dollars of equipment to help keep things under control. The heat detectors ($150 for 6) will alert me to an immanent threat and shut down power to all systems. A quick release CO2 system (have that in stock = $0) will flood the DC and hold down system to kill any internal fires. The odds that these precautions will ever be needed are very low, I agree with that but in the event that something bad happens, a little investment up front will potentially save a lot of loss later.

I've already spent over $30k on this toy. What's another couple of hundred?

[cabnet636]

I have tried fire alarms,, the dust in the air sets them off to easy,, anyone had this problem

[Brady Watson]

I have tried fire alarms,, the dust in the air sets them off to easy,, anyone had this problem

Yes. This is why they are no longer in the shop...The 'sniffer' attracts ultra-fine dust like a magnet and they are impossible to keep clean.

Also, there is always going to be some inherent danger running power tools. You cannot account for everything. If putting up smoke, fire and heat sensors makes you rest easy at night, then by all means do it!

In the words of the great Walter Sobchak, "There are rules, dude..." - the same rules I tell customers when I train them. If you violate them you WILL ruin your work or worse - get hurt:

NEVER RUN THE TOOL WHEN:

1) You have been drinking alcohol, prescription drugs with the dizzy dude on the label or otherwise not 'walking the line'.

2) You have not eaten a real meal with some form of protein in it to keep your brain awake and alert.

3) You are tired or sleep deprived.

Avoiding these 3 things will bolster your success and your health while running the tool. This of coarse goes hand in hand with safety gear AND operating the tool. When the tool is in motion, you are a tool operator - so no flitting about going inside an watching TV with the machine left unattended. You must always be vigilant and not take the fact that the tool is automated for granted. Any number of things can and will go wrong, including things you could not forsee in a million years. Who would have guessed that a few pieces of scrap plywood could break free, jamb the gantry, and cause the bit to spin in the material creating a fire in under 2 min? This happens more often than you'd think.

You can have the best detectors in the world...but they only detect after some damage has been done. A CNC operator is there to catch these problems in seconds. The fantasy of sipping pink lemonade and suntanning while your robot does all the work is just that...a fantasy. Pour yourself some lemonade in a cup with a lid and stay with the machine. It cuts faster, steadier and better than any one of us...that alone should be good enough.

Running the tool without an operator present IS CHEATING!...and what do we all say about cheaters?

-B

[myxpykalix]

3) You are tired or sleep deprived.
One night working late i put my head down on the table and woke up about 5 minutes later....I wasn't close to the work:eek: but then again i'm in a perpetual state of sleep deprivation.

Running the tool without an operator present IS CHEATING!...and what do we all say about cheaters?

It's not cheating unless you get caught? At least that was what i told the cop last time he caught me speeding....:rolleyes:

[RichE]

Interesting thread. I'm glad the consensus is that fire suppression is not necessary. Not something I had considered even though I actually started a fire strait out of the gate after buying a used shopbot. Turns out I had a VFD setting incorrect and the bit was turning backwards. In a year since then we've had no problems with heat but that just goes to show what kind of mistake has to be made to create enough heat to generate smoke.

FYI, the fire wasn't really a fire, just a smoldering pile of sawdust that I put out by dispersing the dust. We didn't have the dust collector setup yet so I'm not sure what would have happened had the dust been pulled from the table. In retrospect, I'm glad we were just playing around with it and didn't have the dust collector hooked up yet.