CNC monitoring and protection

[jimandi5000]

Hello all,

I hope everyone is staying safe and healthy.

The other day, my wife showed me a video of a unattended CNC mill that was malfunctioning and basically caught fire (link below) and she asked me Could this happen to us?. Well, after watching the video multiple times, I responded with, yes dear, but we can put some protection in the shop to prevent this type of (CNC Mill, 3D printer) runaway. I do have to walk away from my machine and leave it unattended, but I'm definitely not interested in installing a camera system for remote monitoring.

This morning I've designed and ordered the parts to assemble a 240v - 60Amp CNC master power shut off if smoke is detected. This solution would drop the power to my complete system (controller, spindle, and PC) in the event of smoke being detected. As of now, I'm using off-the-shelf parts from Amazon at a cost $36 USD. I should have a working prototype in about a week or two. Let me know if you're interested in the parts list and the design drawing to build your own. The way I see it, it's a pretty cheap insurance policy.

https://www.youtube.com/watch?v=D2xoxPlDnW4&t=31s

Share your thoughts.

[highpockets]

Jim, I'd be interested....

[TReischl]

Jim, I think it is a good idea, BUT. . . . . (not trying to be negative here, just some food for thought)

By the time the smoke detector does it's job may be too late. Here is why I say this:

The dust collector is running, lots of oxygen and embers, dust in the hose and the DC. Turning off the power may or may not stop the fire.

Our machines are very different from cnc machines that run 24/7 in an industrial environment "lights out". They are made out of steel/aluminum/cast iron. They are not cutting wood. They do not have a flammable spoil board.

My shop is quite a distance from our home, so if I do get a fire the whole house will not burn down. That said, I do not leave it running unattended for more than maybe a bathroom break, and even then I feel stupid for doing it so that will probably change. So what if I lose maybe 5 or 10 minutes cutting time? I have way too much time and money invested in my shop to start all over if it burns down. Insurance be damned, I have spent years making tools, jigs, etc that I use.

Frankly, I cannot see any justifiable reason to leave a cnc router running because something is more important than the shop burning to ground.

When it comes to wives? Her shop is in the other half of the building, all her glass stuff, kiln, wheel, pottery molds, etc. If I burned that down the next thing I would really need to build is a small storage shed to live in for the foreseeable future.

But yea, I am going to look at your stuff because it would be handy if I were doing something and did not see it start to burn.

[Rcnewcomb]

While cutting the power will be helpful, what about dealing with the source of the smoke/fire? You would need some sort of waterless fire suppression system.

[TReischl]

Jim, thanks for posting that.

It reminded me to take a look at my old fire extinguisher here in the shop. YIKES!

Just placed an order for a new one and I will see about getting the old one recharged.

[4DThinker]

You're on the right track, but although cutting power may keep a machine from destroying itself, it doesn't guarantee that a fire will go out once started. Throw in a sprinkler system that will put out any fire when smoke is detected and you can start to rest a bit. I've seen a fire start in a tablesaw, as well a smoke generated from an improperly used router bit on our CNCs which alone does suggest fire was just a split second away if not noticed.

Although I want to believe I'm talented in clamping down parts and creating toolpaths enough to start a CNC job and walk away, the potential danger that could happen keeps me in the same room within 2 steps of the E-switch and 3 steps from a fire extinguisher. I don't mind as I usually can find post-CNC and pre-CNC work to do along with cleanup while a job is in progress.

4D

[Rcnewcomb]

I will see about getting the old one recharged.

Check with your local fire department. Mine recharges them for free.

[Adrian]

I use a remote camera when I'm at the office desk or I'm in the workshop with the machine doing other things. Not a chance I would leave it running otherwise. Any automatic system can have failures and the risks are just far too high.

[mtylerfl]

I use a remote camera with sound, too (an old Baby Monitor set).

However, I am always within 20 feet of the workshop while monitoring and go into the shop about every 10 minutes or so to check on things in person.

[SteveNelson46]

I use a remote camera with sound, too (an old Baby Monitor set).

However, I am always within 20 feet of the workshop while monitoring and go into the shop about every 10 minutes or so to check on things in person.

Michael,
This is a sensible solution. However, in my experiences, Murphy was an optimist.

[mtylerfl]

[highpockets]

I have fire extinguishers (need to be checked) in both my shop and garage, but I also installed AFO fire extinguisher balls on the ceiling in both in case something happens while I'm not there.

[jimandi5000]

Hi All,

Wow, really great discussion and I really like all the feedback and suggestions.

I agree with everyone, it's always best to keep your eyes on the machine and generally I always do. but... sometimes you have to go get something to eat or go wash your hands. It only takes a few seconds for something to go south. I don't know about anybody else's machine, but my CNC mill is dumb as a rock and has no concept of right and wrong. So any little protection is a great investment.

The wife did not what me to wait, so she went to Wally-land and got me a "Kidde FireX Smoke Alarm" for a whopping $11.59 USD +tax. This unit is powered with 120v AC and has 9v DC Battery backup. This unit has a 3 wire plug; White and Black neutral and line (120v) and a Red wire. The red wire is utilized to link multiple units together.

Did some testing here in the house and oh my goodness smoke detectors are super loud... Especially when it's only a few feet from your face. As a result of my test the Red wire is sending 5 to 8v DC to the other units and they all trigger. I will be using the red wire back to an Arduino to handle the opening and closing of the 240V digital relay. I've added the Arduino because of some of the suggestions. It would be very easy to add multiple items such as infrared sensor for flame detection, a solenoid valve for CO2 fire suppression, calling my cell phone, sending a text message, etc..., etc..., etc...

Thanks Rcnewcomb for posting the video, I watched it several times and I have a lot more thoughts on how to manage a situation that I had not thought of before. Addressing the dust collection/gate valve so that it will stop the evacuation of smoke/fire, especially, if I
incorporate a CO2 suppression methodology.

Keep sharing your thoughts.

[garylmast]

It's not "IF" what "WHEN". A couple of years ago I decided to go to HomeDepot while I left the machine to do the job. Didn't turn out well.

viewtopic.php?f=27&t=29131

If I need to leave for more than a few minutes, I will ALWAYS turn the dust collector off. I do like the idea of a smoke detector shutting down the machine. In the case of the fire I had, it was mainly MDF dust in the dust collector that was smoldering and no flames. If there were flames, my fire sprinkler system would of went off, but I would still have major damage.

Gary

[GEdward]

A word of caution regarding CO2 fire suppression. When the system actuates it replaces ALL of the oxygen in the affected area with CO2. If you, or anyone else, are in the area the time you need to have a clear path evacuation strategy in place to avoid accidental asphyxiation. The insurance company for a shop I worked in a number of years ago mandated the removal of our CO2 system in the heat treat room for that very reason in spite of the fact that there were 3 egress options available.

I'd personally go with a dry fire retardant rated for all three fire classifications. Yeah, they make a mess...but messes can be cleaned up.

Just my two cents,
Ed