# Cutting unattended



## Rusty Nesmith (Feb 1, 2020)

How many of you get your CNC started cutting and then leave it? I designed a clock for my wife and the center has a 3D design that will take around seven hours to cut. Being new I hate to leave it but that is an awful long time to stand there and watch it.


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## OCEdesigns (Jan 31, 2019)

For me it depends. I have left it several times during the 3D machining. I never leave for long or I try to stay close to at least be in hearing distance. If I'm using a very small bit I try to be closer. Honestly the worst thing is the bit breaks and the spindle just keeps moving in air and you need to start over. But that can also happen as you are watching it.
Otherwise with normal machining I try to be next to it or at least in the shop in case something happens besides an end-mill breaking. I have had the clamps a bit loose and the wood started to shift. That is very upsetting!!


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## difalkner (Jan 3, 2012)

Most of what I cut is very short and fairly aggressive, so I stay in the shop. Often, like the two 10" Longworth chucks I cut this morning, it's over before I can go freshen up my coffee. The longest time I have cut is my radius dishes and those were about 45 minutes each. I walked away a couple of times but it was one of the first jobs I ever cut on the CNC so I was pretty close the whole time. 

Maybe if I did some of these long 3D jobs I would walk away more often but as of yet the longest 3D job I have cut was less than 20 minutes.

David


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## Gaffboat (Mar 11, 2012)

For me, lit depends. I have often worked in another room, keeping an eye on the CNC via a video cam. Today, I encountered a good argument for NOT leaving the CNC unattended. I had finished cutting out one of the sides for a step stool I'm building, and was sanding the edges on it while the other side piece was being cut. I heard a little bump in the sound of the router and walked over to check. The machine was starting a new path to cut out the outline of the piece, and it was quickly apparent it was not cutting correctly. I was a able to immediately stop the machine before it cut the entire shape incorrectly.

I went back to my CAD program to make sure I hadn't changed something. It was fine, but when returning the machine to zero, the X axis had moved by 1/2". I don't know why. When I re-ran the tool path it ran correctly. Something unknown caused the problem as the machine moved from cutting the openings in the piece to cutting the outline.

So ... maybe it's a good idea to stick close the machine after all.


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## RainMan 2.0 (May 6, 2014)

There was a story on this very subject at CNCZone . A guy left his cnc running and it caught fire .
Rare situation,but possible just the same. I think Mike Aka MT Stringer has a video camera so he can monitor what his cnc is doing from his house


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## PhilBa (Sep 25, 2014)

My machine is in the basement and I can hear it running when I'm upstairs. I never leave it alone for very long but often do chores, bathroom break, quick bite and such.

And, like oliver I get occasional gremlins. Can never figure them out though, never in the G-Code. Had a very weird one yesterday - it started a slot in the wrong place - about 20 mm off in X and Y. Fortunately it was outside the boundary of the part so no harm. I figure I need to redo my electronics and add a lot more shielding but that's just a stab in the dark.

Bottom line - you need to keep an eye on your machine. Otherwise a small problem could become a big one.


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## Rusty Nesmith (Feb 1, 2020)

Thanks for the replies. Sounds like I should stay close. I can always rough out a few bowls on the lathe so shouldn’t be too bad.


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## honesttjohn (Feb 17, 2015)

I stay in the area doing something else while my unpaid helpers twirl and whirl. There's always something to do, be it sanding, finishing, making more blanks, among other things in the shop. On a long cut I will come upstairs and do computer and other stuff. After a while you can judge by the sound if something's not right. I've even left the house with it running but the wife was around to shut things down when the cut was done or something didn't seem right. Always try to be somewhere close by. Nothing worse than to see a 24 x 24 inch piece of oak get ruined or watch it go round and round if the clamps didn't hold.


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## RainMan 2.0 (May 6, 2014)

honesttjohn said:


> I stay in the area doing something else while my unpaid helpers twirl and whirl. %*There's always something to do, be it sanding, finishing, making more blanks, among other things in the shop. * On a long cut I will come upstairs and do computer and other stuff. After a while you can judge by the sound if something's not right. I've even left the house with it running but the wife was around to shut things down when the cut was done or something didn't seem right. Always try to be somewhere close by. Nothing worse than to see a 24 x 24 inch piece of oak get ruined or watch it go round and round if the clamps didn't hold.


I could always insulate while mine is running


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## difalkner (Jan 3, 2012)

Gaffboat said:


> Something unknown caused the problem as the machine moved from cutting the openings in the piece to cutting the outline.


Skipped steps? Static electricity?



RainMan 2.0 said:


> There was a story on this very subject at CNCZone . A guy left his cnc running and it caught fire .
> Rare situation,but possible just the same. I think Mike Aka MT Stringer has a video camera so he can monitor what his cnc is doing from his house


I have a camera on ours, as well. I can view it from my phone, iPad, and/or computer and often do.



RainMan 2.0 said:


> I could always insulate while mine is running


Now THAT would be a loooooooooooooooooonnnnnnnnnnnnnnggggggggg running job!! :grin:

David


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## kp91 (Sep 10, 2004)

I had the coupling on my Z axis fail, so it couldn't raise the cutter, and things got really hot quickly. The cutter got blackened, the wood was smoking and it started drilling into the spoil board.

I had only gone in to the house for a head call for 3 minutes and that is when it decided to break. I keep a close eye on it with my web cam when I have to step away


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## honesttjohn (Feb 17, 2015)

RainMan 2.0 said:


> I could always insulate while mine is running


You gotta put it together first and get it running!!


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## PhilBa (Sep 25, 2014)

kp91 said:


> I had the coupling on my Z axis fail, so it couldn't raise the cutter, and things got really hot quickly. The cutter got blackened, the wood was smoking and it started drilling into the spoil board.
> 
> I had only gone in to the house for a head call for 3 minutes and that is when it decided to break. I keep a close eye on it with my web cam when I have to step away


Wow, that was a close call there. Makes me rethink using that style coupler on Z. Given the stresses on it, I think it's kind of inevitable it will fail though there was probably a hidden fault in yours to start.


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## UglySign (Nov 17, 2015)

RainMan 2.0 said:


> I could always insulate while mine is running



Doesnt it have to get built, wait... _have you started building yours_?


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## difalkner (Jan 3, 2012)

kp91 said:


> I had the coupling on my Z axis fail, so it couldn't raise the cutter, and things got really hot quickly. The cutter got blackened, the wood was smoking and it started drilling into the spoil board.


That's a scary scene, for sure!

David


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## chessnut2 (Sep 15, 2011)

After watching this video, I now pause my cut any time I go to the bathroom, etc:


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## Nickp (Dec 4, 2012)

I'm not a CNC'er but if I were I would not leave it running unattended. I wouldn't consider a CNC as being any different than any other tool with a whirly cutty thing on it...table saw, drill press, planer, jointer, circular saw, etc...


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## The Hobbyist (Apr 25, 2015)

I did a half tone of Sandra Bullock. It has 19,640 individual dimple holes made with a 60 degree V-bit. It took over 10 hours to cut. I watched it for a while, and then went to sleep, but not before surrounding the table with three LOUD smoke detectors. Even out at my shop, I would have heard them go off, and rushed out to handle any emergency. I did worry, but I felt the machine was reliable enough to cut it out without my direct supervision. I was lucky enough to be right ... that time.

Joe


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## MEBCWD (Jan 14, 2012)

I use to set a timer on my phone and go in the house to work on the computer or I'd do things like mow, trim trees, or work on autos. When the timer went off I'd go change bits or set up a new job then restart the timer and go back to what I was doing.

Then I saw a post about an unsupervised CNC catching fire and burning down the whole shop. I stopped working on outside jobs and got a video camera so I could watch it from inside the house when I was on the computer.

One other addition some people had made is to add a remote cutoff, either running wires to the computer room with a stop switch or using a wifi app and switch to stop it if something goes wrong.

Now, most of the time I stay in the shop and work on other projects or do much-needed cleaning. I only leave for bathroom breaks after pausing the CNC. If the run will be much over 5 hours I might just set it up as 2 or 3 toolpaths so I can shut it down overnight and start again the next day.

There are several videos showing burned up CNCs, shops, and businesses. It's not worth taking the chance of losing everything including your shop.


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## difalkner (Jan 3, 2012)

When I built our CNC I added a second kill switch and mounted it in a box connected to the main enclosure with a 10' shielded cable. I will occasionally be at the table saw working on a job and I can take the corded emergency stop with me. When I am on the table saw I am paying attention to the table saw but listening to the CNC and I can hear anything out of the ordinary even with hearing protection. Like most of us with machinery, you know what they're supposed to sound like and when something's off you can tell instantly. If I hear anything odd I can hit that kill switch far faster than I can make it over to the one mounted on the machine.

I like your idea, Mike, of breaking long jobs into several toolpaths to make it easy to stop and pick back up later. About 95% of my jobs are multiple toolpath anyway but that's because of tool changes, zeroing off the top and then the spoilboard, etc.

David


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## Rusty Nesmith (Feb 1, 2020)

Looks like I will be staying with it while it is cutting. Especially after seeing that video.


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