[RESOLVED] Job failure from apparent static discharge

I am trying to resolve a major issue with my 1000 mm X-Carve with regard to persistent random stops

Description of Problem
Whenever I run a new job there seems to be a 50/50 shot that the machine stops mid-job and I have to restart. Sometimes this behavior immediately follows a static shock to the frame, other times it happens after turning the spindle on/off, but the majority of the time it happens when I am out of the room, sometimes very shortly after i leave the room.

1000 mm X-Carve with the X-controller
Universal GCode Sender (Nightly build 1.2.2018) to great success until recently
Standard shop vac/dust shoe collection system

Steps taken so far
My first thought after getting shocked was that this was a grounding issue. I bought a static dissipating mat for where I stand in front of the machine. I attached wires to the router and each axis arm, routing them to my building’s Earth ground. This seemed to work at first, but I soon had another failed job. I then added another grounding wire to the chassis of the X-controller, but now the failures happened within a minute every time. If anything, my extra grounding steps made the problem worse.

I have put both my desktop computer and the X-controller on a UPS to mitigate any power fluctuations from the router, air conditioner, or other high amp appliance.

I have upgraded to a better, shielded, USB cable from my desktop to the x-controller

I have switched back to the latest stable release of Universal GCode Sender (1.0.9)

I disconnected the ground wire to the x-controller.

Currently the main grounding line is no longer attached to Earth ground

I have finally gotten this one job to finish, but to do so I had to leave the room and do everything remotely on the computer. It had already failed once before with this setup, so I think I just got lucky this time.

Is this even a static problem anymore? I never had these problems when using Easel, but it can’t handle all the functions I use. Is there a better setup within UGS to make the job more stable?

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Are you are using automatic spindle control, on and off thru a relay?
Are you doing the same with the shop vac?
I have similar issue trying to operate both thru 2 separate relays. However if I operate the spindle only thru relay and the shop vac from a remote switch the issues is 99% resolved.
I also tried grounding the dust collection components with aluminum tape as a grounding method. That did not resolve the issue.
I think my shop vac is creating noise that back feeds into the controller somehow?

I had this happen once and it was a result of static build-up in the vacuum hose. I could feel the static on the hose and it was a pretty obvious cause-effect. It just happened the once and freaked me out … I can’t imagine the pain of it happening all the time. You’ve taken a lot of good steps … anything you could do with the humidity level?

I’ve heard of static in a dust collection system also being a fire hazard. Don’t know how true that is but it does sound plausible enough to keep in mind.

I am not using any relays, and the shop vac is on a separate breaker as the X-Carve and Computer. I will move the router to the same as the shop vac just to take it off the X-carve breaker. Thank’s for the suggestion!

The closest thing to grounding I have for the dust collector is that the hose wraps around electrical conduit that is connected to Earth ground. I will try wrapping the length of hose with wire or metal tape.

So you put your grounding inside the vacuum hose?

Google it to see examples … but basically you run bare copper wire either inside the hose or wrapped around it, and then ground it on the machine end. There is debate on if the static can cause an explosion, but I think Mythbusters disproved it. I haven’t done it to my system, but may do so now due to the new CNC.

I went to home depot and bought bare stranded copper wire. Very similar (if not exactly) like this:


You wrap that around the outside of the hose and it’ll dissipate the static if you ground it. I’ve been lazy and not done it but I also haven’t had any issues with it either.

Or you could step it up and go with something like this:


Here’s a good video that explains how to properly do it;

Also, if you are using PVC do NOT simply run wire outside the PVC pipe. Yes it will remove the static on the outside, but NOT on the inside of the pipe (as PVC is a insulator). Follow the video above for the best way to get around this.

As xfredericox has mentioned, dust collection can be a fire hazard, so even if this doesn’t solve your issue you still need to do it.

Also, if grounding the dust collection doesn’t solve the issue, look into EMI filtering.

The static caused fire issue has been circulating for a long time but has, for the most part, been shown to be a non issue. and there has never been a proven, documented incident to the contrary, The amount of suspended dust required to support combustion coupled with the fact that in a DC system it’s in motion, really makes it unlikely that a static spark could ignite it.
More likely is the possibility of a spark from a bolt or other ferrous metal item being picked up and creating a spark when it meets the impeller on the DC itself that could start a smoldering burn in the dust bag that could eventually escape and take the whole shop down.
Also, wrapping a wire on the outside of the DC pipe wont drain off most of the static charge like a wick on a candle. It will only remove the charge where the wire touches the pipe.
Static charge will only build to a certain level, it then becomes stable at that level until it is discharged in a small area like where you touched the pipe just before inventing new words to add to Webster’s dictionary of colorful and creative language.


Many firefighters, like the one who wrote the article below, feel differently. Lots of good information in this thread;


A valid point,and you make your case very well and cite seemingly credible sources.
However, my point is in reference to a static charge igniting sawdust WITHIN a dust collection system is highly unlikely.
There are situations where airborne dust particles will ignite, but the ignition source is most often a hot surface situation such as a hot roller bearing or the like. which can then cause a fire in standing sawdust, on the floor for example, which may in turn light off a cloud of suspended dust of the right concentration causing an explosion.
But one would not be able to see through such a cloud much less work in one. And not to discredit the author of the link you posted, but do you realize the physical volume of space 1 pound of sawdust fine enough to explode occupies?
And then to get it all suspended in the air?

Part of my comment was directed specifically at a static discharge and the inability to completely eliminate a static charge from dust collection piping. (Note, I could be mistaken but, an all metal ducting system would alleviate a static issue if grounded properly. )
Near the start of this thread it was mentioned that static charge may be a contributing factor with the OP’s difficulty with his machine. I believe that is a real possibility.
Lets get this thread back on that track , shall we?

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Everyones system will of course be different, but even a small spark is still a spark (ignition source). As Phil has mentioned vacuums are a known source for making large amounts of static. To be clear, we’re not talking about the sawdust that can easily be seen igniting. It’s the dust particles that are around .5mm (or smaller) that will ignite. This video shows some examples, and also shows how surprisingly little is needed to ignite;

You are not mistaken. A metal ducting system could easily be grounded, but PVC is a insulator.

Safety issues are important to mention but yes, I agree, back on track. Hopefully the OP has solved his issue.

That is what it looks like if you empty your dust collector into an existing fire.
Believe me you do not want to be down wind.
I am guessing Phil can confirm that.

Sorry to interrupt your discussion on sawdust safety, but it appears my problem is solved!

Over the past day I rewired my grounding line to bypass the controller entirely, use copper instead of aluminum, and created two independent grounding points across the machine. I also used bare copper wire to ground the vacuum hose. Pictures below!

Approximately $12 of wire and 45 minutes of winding. McMaster wanted over $150 for a static resistant hose that I couldn’t even ground without damaging!

The foam that I’m cutting creates a LOT of static, and was the job my machine kept failing on.

The wire wrapped around the electrical conduit is “temporary” until I can be bothered to buy a real ring bracket. I’m also considering using plastic shrink wrap to sheath the grounded tube just to protect the wire.

Not pictured here is the externally powered USB hub that I’m now using and multiple ferrite beads on the USB cable. I was able to finish a 2 hour job without ANY issues, and I even taunted it a bit by touching the frame, playing with the router, and brushing the hose. I believe my issue is resolved!

Thank you everyone for your input as I worked through this problem!

Lastly, I hope it will give you comfort knowing that I don’t cut much wood on my machine, mostly foam and metal, so I won’t be starting any dust fires.


Just throwing gas in the fire of this discussion though!

Good to hear it’s resolved and was a simple fix.

McMaster is good for a lot of things, price isn’t one of them always.

I don’t know about foam, but I know dust from metal is also just as dangerous as from wood according to the National Fire Protection Association (NFPA) and OSHA. Dust from plastics is also dangerous, and foam could be similar, but I would check with NFPA and/or OSHA.

Many things that don’t normally burn, can and do when in dust form.

Very happy to hear that you solved your issue Stephen. Glad you got away from aluminum wire :wink:

Yes, metal dust is worse because metal dust burns at a higher temperature than wood dust does, and that can cause an explosion if water is used to extinguish it.

Stephen, find out what your foam is made out of and look it up here to see what its explosibility rating is.