X Axis Stepper Grinding

Boot up the machine to do some work, homed machine no issue, drove the machine to workpiece to probe and after setting XYZ on my work piece I noticed the probe wasn’t quite where it needed to be, so I went to drive the machine back to the probe and re-do the XYZ. All of a sudden the X axis started grinding and stalling out, making a terrible noise.

I turned the machine off and was able to turn the X axis ball screw with zero resistance or grinding… So it doesn’t seem to be a mechanical issue. I checked the ball screw to stepper connection the front and rear X rail leg, all good. So I removed the X axis stepper and when I use the controller to ‘jog’ the stepper free of the union and just in free air it just is jittery and doesn’t spin.

Any thoughts? Bad stepper? Something else?

Hey Tyler,

this is a cable / connector problem. See point 3A in the first link below.

See these Support documents in the FAQ section:

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@Aiph5u Thanks for pointing me here… I will take a look. Has anyone decided to run all their cabling external to the tubes for serviceability? Having to disassemble the entire unit, lose square, lose tram, lose registration elements on the table, etc just to CHECK a wire is beyond ridiculous.

Besides stating the obvious of not being able to wrap my head around how a cable just goes bad in the span of 15 seconds no stressor or event to cause it.

But apparently Murphy really hates me if I do have to take the unit apart, cause I just cancelled my Elite Upgrade order this week for that exact reason. I can’t have the CNC down that long and lose all my registration elements to take it apart to do the Elite upgrade… And now I may have to take it apart just to check a wire and then NOT have the Elite upgrade.

I have no words right now.

Hey Tyler,

probably everyone who decided to retrofit drag chains to the machine.

But it is also a question of design. The Onefinity CNC is absolutely unique in its design. It rather looks like a piece of art than a hobbyist CNC machine. Or can you say this was no point in deciding to buy it? Unlike other CNC machines, the linear rails are the axes. It’s these chrome-plated, hardened steel hollow shafts that make the difference to the competitors which produce CNCs that are without exception ugly. So hiding the cables is part of the concept.

Drag chains will be on the outside of the rails, but they usually are on the back of the X rails and drag chains can at least look better than raw cables attached all over the machine.

As cables and connectors rather fail where they are moved and less inside a tube, I think disassembling everything would not have been necessary. If you had found the help documents and also e.g. the postings Retrofit strain relief to your machine, which the machine unfortunately lacks (and maybe also in this case you may want to procure what is needed to make new cables) before beginning to disassemble something, your problem would probably have been solved by servicing, repairing or exchanging one of the connectors or cables that are subject to permanent motion (what these connectors are not made for, since they are made for internal electronics), but are easily accessible and visible. So I would have a look at the cable that goes from the the beginning of the X axis on the left to the controller, and also have a look at the socket in the left X axis foot, which is where the people linked above retrofit strain relief – exactly for the reason that failures appeared.

A bipolar stepper turns when four signals on four wires appear in a specific order. In case one of them fails and one of these signals is missing, the stepper does what you have shown in the video.

that is perfectly possible. These connectors are only tin-plated, which either leads to corrosion, but they are also made to be put together exactly once (and not disassembled multiple times) which can lead to the extremely thin tin layer to be scraped away and the bare copper to be exposed to air humidity which can make him corrode rather quickly. Also if you use the wrong crimping insert or the wrong cable gauge or your employee that makes the cables is not fit, you get pins with wires that come out on motion (remember, motion is not what these connectors are made for). And what do you think why they are so prominently appearing in the help document above.

Wire connection issue.
In the 10s of thousands of machines we’ve sold, we’ve seen 1 motor go bad. We can say with 99.99999% confidence it’s a wire:

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@OnefinityCNC @Aiph5u Glad that we are 99.99999999% its a wire issue…. But it doesn’t change the fact to REALLY check the wiring based on everything in the support doc and videos the entire machine needs to be torn apart.

I’m probably just going to buy all new replacement cables and then I have to figure out how to get to the X axis cable inside the tube without tacking it all apart. I haven’t started disassembling anything yet, but have checked the accessible connection points and wires and see no issue, no corrosion, no strains in my drag chains or indications of where the issue might lie.

Hey Tyler,

And I hope this time you will try to figure it out by consulting the FAQ section before you start to do something :slight_smile: