I had some small dupont jumper wires fail on me. When I opened them up, they had rusted inside.
It’s really the wire here, even after I entirely remove the connector and get contact directly to the wire’s copper on both sides I’ve got no continuity…
The case I was talking about was inside the insulation. It was rusted inside the wire.
I would definitely be inspecting one of those if you are having repeat issues. It would make me angry if all the wire was rusty, but at least it would explain the problem. You can get probes with really sharp tips and actually poke through the insulation (like a needle) to probe along the wire to try to figure out where to cut it open.
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Ah ok, got it. Yeah it’s possible, I really don’t have any better explanation.
I think I’ll just replace everything, I don’t trust it anymore.
But it really sucks, I’m super angry, so much time wasted.
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I feel bad for you. That does suck.
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It’s still printing right now, as you can see on the pic it did lose continuity at some point during the first layer. I kicked the Y axis cuz I was a bit angry and it fixed it . 
Now it’s printing fine again, for no reason whatsoever.
The continuity loss seem to happen during a short range of positions, so that’s a small cut in the wire I think.
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have you traced the wire path while the machine is in the trouble spots? maybe you have to tight of a turn radius or its pulling over something sharp? I’m sure you have already thought about that but its my first thought when hearing about self cutting wires(but think, now you have a wire cutting machine XP).
generally over current on the wire would cause a short before a break, (the copper can carry a lot more current the you would expect. it just gets way to hot and melts everything around it) so i would be supprise if that was your issue.
the build is awesome and i hope you are able to track down the problem without to much frustration.
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Yeah I tried to trace the wire but saw nothing suspicious really. I’ll try to autopsy one wire using jeffe’s method.
I also share your opinion on wire size vs current. I’ve passed insane amounts of current through tiny wires on my electric motorbike and they didn’t burn yet, so those ones should be fine with just a few amps…
At this point I can’t rule out a “chinese qualitay” issue. Too bad, that was not some cheap wire, I thought it was the good stuff.
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It is stranded wire, right? If it was solid, maybe it work hardened?
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I don’t think I can help in any way, but if it’s any consolation I have been watching you build this thing in absolute awe. Both envyus and inspired by your sheer motivation and constant positive progress. I’m certain you will solve this problem and be producing massive print soon enough. 
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Heh, I once got really mad calibrating my MP3DP and just punched it! 
Luckily nothing broke. 
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Yes, stranded wire, supposedly tinned copper. On my first machine I was using ethernet cable, they were solid wire and despite that they held up much better 
So far it only happened on the Y axis (both sides, one after the other), the X axis is fine.
The issue did happen again at some point while printing the blue part yesterday, so the print didn’t even got completed.
I’m wondering if this issue could come from a defective motor somehow, so first I’ll replace the motors and see if it works. The motors do run very hot, I think they reach 60-70 degree C on the outside, so it’s possible they get too hot, I don’t know. I’m pushing 2.2Amps through each motor, that doesn’t seem crazy to me but I don’t know.
I’ll also need to find a solution to cool the motors if I want to keep those kind of accelerations and speeds (and I do!), the plastic around them starts to soften after an hour. I’d like to avoid using fans, but I don’t see any other realistic solution yet (watercooling would be too complicated to do, plus lots of additional mass to move)
Anyway, first I’ll change the motors, then I’ll try changing the wiring. I’ll change it no matter what anyways, I just can’t trust it anymore.
One thing sucks with motors in series: it’s much harder to diagnose a problem than when the motors are in parallel.
You have a fan on the drivers right?
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Yes, I have a blower fan in the electronics case. It can’t be the drivers overheating because this board is high tech, it gives you a clear alert message in case of overheating driver.
Okay, just checking.
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are the silicone wires ‘too’ flexible? I don’t think I’ve ever had stranded wire fatigue and break in the middle. This is very weird.
It does look like you’re using cable chains, so I wouldn’t expect it to be from a wire being crimped in the middle or something like that.
I would probably have to agree with you that it was broken from the factory. Or it could be that the wire was damaged on the spool somehow.
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Maybe the cable chain has a sharp edge or it catches the wire inside somhow
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Well, some progress today: I’ve redone all the wiring already. Apparently it goes much faster when you’ve already done that twice before 
I started with the Y axis, did both cables and gave it a try: after just 3 or 4 moves the X axis started to show the same symptom.
So I just went all the way and made a new harness for the X axis too.
This time I used some beefy wires, and I made twisted pairs just to follow all good practices in order to definitely be sure that wires won’t be the issue anymore.
I launched a print 30minutes ago, so far no issue whatsoever, so that’s a good sign.
It’s really late here in China now and I have to go to work tomorrow, so I’ll have to shut the printer down, but it’s possible that the problem is solved!
So maybe that was just some crappy wires, hopefully. I’ll have more time to test everything this weekend
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If I’m doing my time-math right… It’s already tomorrow 
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You have a job?! Don’t tell me you got family as well? You are so super fast with your tinkering, I can’t imagine that you even sleep 
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