S3 stopped in the middle of a pocket operation

New user, new machine, finished setup and testing 2 weeks ago (including a cover for the PCB), started a project for a bench rest last week and was having fun milling T6-6061, but today the S3 simply stopped moving at about 65% of the pocketing task. This has happened before, so i reset the computer and tried to re-enter the task. All looked ok, but could not jog the spindle, tried again, but Carbide Motion simply quit. Tried re-loading Carbide Motion but the program displayed “Machine Parameters are invalid”. Shut everything down for 10 minutes and tried again - Carbide Motion displayed “GRBL Error: Cannot open port for Nomad”. I guess it believes that its a Nomad now.

Has anyone seen this condition before, is there any advice on where to start trouble shooting?

Make sure you unplug the usb cord from the arduino. Usb power is keeping you stuck in your problem.

Thank you Sir, i give it a shot, but no joy. Still returns the message “GRBL Error: Cannot open port for Nomad”

Did notice that the PCB/controller is taking longer to lock the stepper motors when powered on, than before (originally took approx 1 second, now taking approx 7 seconds) - am wondering if i have done some damage to the GRBL Firmware or PCB/controller on the S3?

Just for clarification, when I get these errors I have to do all of the following at the same time to reset everything.

  • Close Carbide Motion
  • Power off the mill (nomad in my cade)
  • unplug the usb to reset the controller
  • manually move the spindle to the middle of the 3 axes (in case any limit switch is triggered)

Only then I can replug and power up successfully, but that seems to work 100% of the time.

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Thank you Sir, have tried this course with still no joy - Carbide Motion doesn’t seem to see the S3. Have sent an email off to Carbide 3D, will keep you posted on the outcome

I had a crash once result in a corrupted driver installation — uninstalling the device and reinstalling it got things working again.

On my Win7 laptop, when I get a communication error I need to reboot both the Nomad and the PC. Just shutting down the Nomad and restarting CM isn’t enough in my case. It must be something about initializing the USB controller.


Thank you all for your contributions (its wonderful to be able to talk to folk experiencing similar issues), i wanted to close out this string with an update on where things stand at the moment.

No further on with fault finding the error and 2 days later, i decided to try re-flashing the PCB. Reconnected the S3 and laptop, was surprised to find that they were now communicating (why 2 days later and no different to the initial unplug and re-connect events?) - was also able to jog the machine.
In testing all functions, find that now, Y2 stepped was not responding. Finding nothing obvious, I re-seated the connect, and voila all working as it should.
Re-entered the pocket to continue the operation and the S3 stopped approx 10% into the operation, coincidentally with plugging the laptop power supply into an new source.
In summary, i have not found the fault, i have not replaced any parts, but the S3 is now operating as it should.
The possibility exists that;
There may have been a power hick-up that affected the initial process and possibly the re-entry operation.
I may have inadvertently disturbed and restored a connection in the last attempt to reconnect to the S3

Sorry to not have a definitive answer to the initial problem, but happy to be up and running again


this may help: https://www.youtube.com/watch?v=JPj1EyQUkGw

Thanks Nick, this is very interesting.
I am using a Mac to communicate with the S3 (the power supply is not grounded) and coincidentally in previous hick-up’s, i did notice that after switching off the Dewalt 611, loading a new operation, i was not able to jog the S3, eventually requiring the rebooting both the Mac and S3 in order to start a new operation. There might be something in this power sensitivity issue?
Might be worth while to get an oscilloscope out to monitor the power and communications lines? I am currently working on other projects, so it may be a while before i get back to this one.

Thanks again.

Yes oscilloscope will definitely help you see any noise around the system,

I would recommend (as in the video) get a crocodile clip or something and connect the chassis of the mac to ground!

Before doing any of this, are you sure that the ground and neutral of your 110VAC socket is correct?

There are cheap checkers available. If you haven’t checked it I would start there. If these are not correct, many kinds of mayhem will result, including things much like you’re reporting.


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I had this happen to my Nomad twice.

First time: I shocked myself on the aluminum rail of the S3 (while it was off) and it some how caused my Nomad to stop cutting.

Second time: I ran my bandsaw and looked over at my Nomad and saw it stopped.

All of these were sharing the same power strip. Seems like it is sensitive to power. My vacuum runs fine from the same power strip.

In a machine shop, each machine is on a separate circuit - to prevent things like this.

Motors are notorious for “hashing up” power such that it really screws up computers.

Many CNC machines have two wires - one for the computer element and one for the motor element. This allows the elements to go on separate circuits to isolate any power issues.

The Nomad has a one power inlet to power the motor and the internal processor that runs things and handles the USB. Based on this and some other reports, it appears that the Nomad has some power sensitivity issues.

I’m suspicious that the reports are due to noise induced by RF in the air but it could be an issue. Most likely, it is voltage variation and “chop” in the power lines.

I suggest running a wire connected to the metal frame to earth ground.



hmm I would have to find a good place to attach the Nomad’s frame to the ground. There are some metal exposed underneath.

I would first try a simple contact ground. Take the copper wire, run some sandpaper of it to remove any oxidation, pick up the Nomad and lower it on the wire. Run the wire to earth ground.

If that is an improvement, then think about a more permanent attach method.


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I woke up this morning and I was disappointed in myself. Before playing with grounding wires, let’s check the basics.

If you don’t have a ground/neutral checker, get one - they are inexpensive - and check all of the wall sockets. It makes no sense to debug these kinds of issues if there are problems like reversed ground/neutral (which can kill!) or no ground.

Next, determine how many independent circuits there are. As I pointed out, in a machine shop, each machine is on its own circuit. Can you move the big motor stuff off of the circuit that the Nomad is on? Can you put your computer on a circuit that is independent of all motor driven equipment?

Surge suppressors - they tend to use Metal Oxide Varistor (MOV) components - are important to protect computers but do you know they wear out? That the cheap ones wear out quickly (1-3 years is common, live in FL and they may be gone in under a year)?

Protecting from surges does nothing to filter the “chop” in the power, nor does it provide voltage regulation.

High end surge suppressors have additional circuitry to protect the MOV and often do more. More on this later.

In a shop setting it is best to have any computer behind a UPS. The UPS needs to be a good one - cheapies can keep the power going but do little to protect the wave form and voltage. Ideally, it should be one that generates a pure sine curve - but this may be prohibitively expensive. The running time on battery is not the primary issue - it’s the power quality. A good UPS provides a huge amount of isolation between the raw power and the computer and provides both voltage regulation, filtering and sine wave forming (approximation).


I use Schneider Electric - AKA APC - for UPSen when I consult for CNC setups.

I’ve also used Tripp. CyberPower passes all of my research but I haven’t used them as yet.

Typically, I install APC Back-UPS XS 1300 or 1500; Smart-UPS when high end stuff is necessary. Something like the APC Back-UPS BE750G is a fine choice.

Outside of known quality, replaceable and recyclable batteries are important both in term of cost saving - they do wear out - and for the environment.

The Nomad should, ideally, be behind some sort of filtering - not just a surge suppressor. Most UPSen have two sides - battery and filtered, the former having the highest quality power as well as battery back up - but I’m sufficiently paranoid that I wouldn’t put a Nomad on a UPS (due to the motor element) even on the filtered side. I would call APC (or the UPS company you choose) - and ask them if they are OK with a motor element (small) on the filter side.

A power conditioner is the common choice for protecting equipment with “high tech” stuff inside (e.g. the Nomad is a small motor and a small embedded computer, audiophile equipment, flat panel TVs, game consoles). They provide filtering, isolation and surge suppression that protects the MOVs from wear.

Fuhrman and Panamax are my usual choices for power conditioners. The Nomad is pretty small so high end equipment is unnecessary. A Furman M-8X2, Fuhrman M-8Dx, Panamax MR4000 and Panamax MR4300 are appropriate.

Start by verifying your power is wired correctly in the wall. Isolate equipment on separate circuits - when possible - and put your computer behind a quality UPS. Add a power conditioner to the Nomad. Finally, grounding the frame of the Nomad - it makes a fine antenna - is something to try.

If you’re using a laptop to run your Nomad - they have pretty good power isolation due the the battery charging circuit (essentially a UPS) - I’m tempted to recommend using a power conditioner on the Nomad before a UPS on the computer.


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I’m running a macbookpro so I don’t think that causes any issues. But everything is out of my garage coming from the same outlet. I think the Nomad or whatever machine that are sensitive should have some kind of filter for spikes.

Or I should just run an extension to my big motor item from my hallway (if really needed). I’ll just keep in mind that I shouldn’t run both machines at the same time.

Laptop? Then go for power conditioning on the Nomad first.