Onefinity Controller Stopping Mid-Program (solved: EMI / Static Build up)

I hope this is my issue as well. I had I randomly shut down Saturday night 2.5 hours into a carved I grounded the table (it is an old drafting table so it has metal frame which the controller is screwed too.)

I also grounded all the dust collection back to the unit.

In the last picture you can see I have a grounding point at the stepper, when I connected this ground, the motor started making a humming clicking noise. I disconnected it before operation but it was concerning as I wanted to ground the rails. Hopefully someone more knowledgeable than I could explain this.

Also I should I note that my controller was already fed via a UPS on a separate protected circuit.

Hey John,

the other day there was this issue, the cause was that the stepper wires inside the rail were pinched between rail and rail hole cover, making a short between one stepper wire and the rail. The issue came up when grounding the machine. Usually grounding the machine is not done when following manufacturer’s instructions when assembling, but recommended regarding security and is a result when using a spindle anyway.

See also this.


Seems you posted your message before all pictures were uploaded! :slight_smile:

Fixed, thank you sir.

Sh&&&&&&&&&&t, I do not want to take the whole thing apart for short cable after I got it all squared and dialed in but I may have to. On a side note. I accidentally connected the magnet probe to the rail, and I immediately got a fault. Is that indicative of anything?

Hey John,

You can check if it is this issue the following way if you have a Multimeter:

  1. Unplug all power from the machine (shut down the Controller properly before).

  2. Disconnect all ground wires from the metal parts of the machine. If you use a spindle, or a grounded milling motor, unplug it.

  3. Set Multimeter to “Resistance/Ohms” and attach one measuring tip to the machine (e.g. machine’s foot; ensure good connection on metal).

  4. At the connector on the CNC Controller case, unplug the plug coming from the stepper motor which makes the noise.

  5. On the cable you just unplugged from the Controller, you see a four-contact Amphenol/Molex Plug:

  1. Stick the other measuring tip of the Multimeter into one of these four contacts of the stepper cable plug.
    It should measure no resistance.
  2. Repeat with remaining three contacts of the plug. If any of these show a low resistance, you seem to have a short between a stepper wire and the rail. If this is the case, you can watch the video Support : How to Access the inner tube motor wire and check if you find it.
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If you have a multimeter you can check it the way I described in the other posting.

Probably. Magnet probe is ground. What is the exact error you see?

I will be a couple days before I can get back in the shop but I will test it out and get back to you.

It appear you are correct. See attached video. Two wires appear to have a short. I checked the other Y rail and did not get continuity on that one so that is plus.

Note this video is unlisted and only available via this link.

Also this is the error I am getting. When the probe attached to the rail.

Hey John,

if you are sure that there were no other contacts present (short through your body, (fingers)), you will have to proceed with step 6 :frowning:

What was the Ohms range you’ve set the multimeter?

I think it is automatic :woozy_face: So not sure.

I am not very experienced with a multimeter.

For hunting this issue, I would start with megaohms, and see if the resistance is stable, and then go smaller. If the number shown on display is not stable it is either out of range or you have oil on the rails or something which disturbs contact. Best would be to clamp one measuring tip to rail or foot with a clamp.

Note that like when Darren had this issue, as long as only one stepper wire has a short with rail or foot, the machine still might work without issues. It’s when you ground the machine that the issue shows up. Or when two or more stepper wires have a short through rail/foot. In the first case the motor error shows up when you ground the rail or foot, in the second case possibly always.

In both cases any short between stepper wire and rails is a fault.

Further Reading

How to Wire Stepper Motors
DRV8711 - Texas Instruments

Yes machine seems to work okay for awhile. Since i got it though I have been having issues with interference on the screen since I got the machine. It flickers and goes out. I have also had a lot of issues with disconnections. I contacted support about this previously and they said it was a software issue and the upcoming patch would fix it but the recent patch didn’t fix my issue. They also sent out a new controller for a different issue at one point and I am still getting the screen flickering and disconnections.

Yes I saw that issue Darren had. I wonder how common this is?

Thank you for the light reading material :sweat_smile:. I have contacted support as I am hoping they will send out a new harness that I could swap out. The harness I got with my X-50 rail was an improvement over the original harnesses.

If you don’t mind me asking @Aiph5u what is your day job? You seem very knowledgeable on this subject.

Hey John,

to access Inner Rail Tube Motor Wire only after having received the replacement wire is wise :slight_smile:

Something totally different. But with electronics I got heavily infected during childhood and they haven’t found a vaccine against it since then :slight_smile:

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Hey John,

attaching the magnet probe to the rail should in no case trigger a motor error.

I agree. Support has asked me take the rail a part.

Hey John,

besides cables being pinched between rail and end cap making a short this way it is also possible that a crimped wire became loose from its pin at the connector that is inside the rail.

Hey John,

when I looked at the video describing this (Support : How to Access the inner tube motor wire), it was clear that of course you don’t have the rails lying around like this, but that you have an assembled, working machine. I just had the thought that if there is ever any concern about the cables inside the rail, it would be good when planning a table for the Onefinity CNC to have a service hole under each front foot which would allow access to the screw that loosens the end cap (which allows to remove the cable then).

And my second thought is, why don’t they have light at their film set? (Or at least why doesn’t someone click on the brightening/contrast button in their post-production software?)



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Lol I thought about drilling a hole thru the bottom my table as it is only a temporary table but I am not confident in my drill stops and I am concerned I would plunge it into the bolt making the problem worse.


Hey John,

May I recommend you these ingenious Star-M Depth stops :slight_smile: :

Star-M No.5005 Drill Stopper

The plastic cap rotates freely and stops rotating when you reach desired depth. I use a set of them, from 3 mm (=approx. 1/8″) drill diameter upwards. Picture shows ⌀ 15 mm drill (=approx 19/32″).

Available here or here

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