RE:
I went mk4->mk4s->core one and printed like ~100h without problems (parts for coreboxx) and now I got the reboot feature.
I set 11h print and went out to work, came back and got to see core one all dark, cold but beeping with BSOD on the screen (screenshoot included). The BSOD codes of course won't tell you anything. Though maybe it was once in a time failure. However the next print failed on first layer, heard a beeping and saw Core One rebooting and resuming print.
With the power of google I found this thread, and oh boy, a grounding issue. I scrapped the paint under both screws for X and Y motor, got a normal washer (didn't have a star one at hand for M3 screws) and screw it togheter. Checked with multimeter - it was now grounded and it stopped rebooting.
Thank you noumenonsense for finding out what was the problem.
I am disappointed in Prusa, both with the issue (which should come out in testing and could be easlily solved just by adding star washers) and how it was (not) handled. Issue was reported in the middle of march, so we have 5,5 months without Prusa finding out the root problem, and when the users found out it was a grounding problem with motors in june, Prusa also didn't say anything it or made suggestion to install star washers under motor screws. What is more, this looks like a flaw in design which is pretty bad for a 1049/1349 euro machine (not to mention the VFA issue for which Prusa after 6 months says just tighten the belts more).
RE: Core One crash/restart
I am disappointed in Prusa, both with the issue (which should come out in testing and could be easlily solved just by adding star washers) and how it was (not) handled. Issue was reported in the middle of march, so we have 5,5 months without Prusa finding out the root problem, and when the users found out it was a grounding problem with motors in june, Prusa also didn't say anything it or made suggestion to install star washers under motor screws.
It seems Prusa doesn't monitor this forum, at least it appears that way. Wonder if Prusa knows about it or not? I guess one one to inform them is to add an incident to the firmware github repo.
RE:
The fix really is removing two screws, one for each motor, easily accessible without any disassembly, scrape some paint off, add washers to the screws for better long term results, and install the screws to their original locations.
ps: I took off the bays because I wanted to use a flat pilot drill bit (I used a 1/4" / 6mm bit) that would cut the paint and not the metal... the bit needs to be vertical to work as intended. But the scraping could have been done with an Exacto knife.
RE: Core One crash/restart
I really appreciate the time everyone has put into this thread. I've been dealing with the hot-end noise confusing the loadcell issue which at least doesn't spoil a print ("only" prevents printing). That seems minor in comparison, especially since it can (at least for me) be avoided in g-code.
Here in coastal New England we're heading to Fall/Winter where I'll be dealing with much lower humidity than in the summer so I'm off to scratch some paint and put on some star washers. Thank you all!
RE: Core One crash/restart
I had this problem on a large format print after a week of total successes in printing after building the kit a week ago. I was very surprised to find the printer suddenly powered off every 7 minutes or so - eventually, however, I noticed that it only occurred on one section of the print, and once that bit was finished the last half hour finished without any more crashes. So it may very well relate to static build up caused by very particular sets of movements.
Anyway I had a look in my screw box and sure enough I had a whole pack of unused scratchy star washers. So I popped 2 onto one of the screws on my x and y axis, tightened up and will see if the problem recurs. Has anybody raised this via github?
RE: Core One crash/restart
Anyway I had a look in my screw box and sure enough I had a whole pack of unused scratchy star washers. So I popped 2 onto one of the screws on my x and y axis, tightened up and will see if the problem recurs. Has anybody raised this via github?
Did you check that it really was grounded? There should be 0 ohm resistance between the motor housing and the ground connection on the chassis.
RE: Core One crash/restart
I had this problem on a large format print after a week of total successes in printing after building the kit a week ago. I was very surprised to find the printer suddenly powered off every 7 minutes or so - eventually, however, I noticed that it only occurred on one section of the print, and once that bit was finished the last half hour finished without any more crashes. So it may very well relate to static build up caused by very particular sets of movements.
Anyway I had a look in my screw box and sure enough I had a whole pack of unused scratchy star washers. So I popped 2 onto one of the screws on my x and y axis, tightened up and will see if the problem recurs. Has anybody raised this via github?
There are threads on GitHub but Prusa essentially has dismissed it - the GitHub resource is driven by software types, and since this is a hardware issue... no surprise they want to ignore it.
As Hy suggested, you may want to use your trusty VOM/DMM and measure from that spade lug in the back left corner to the two screws you placed the star washers on and verify the washers got through the paint.
RE: Core One crash/restart
I finally got time to take the side panels off and added some grounding washers. I used a volt meter to confirm that I now have grounds on both the x and y axis motors to the frame.
I'm running tests now. If this works, it would be a simple, lost cost fix to this issue.
RE: Core One crash/restart
Did you check that it really was grounded? There should be 0 ohm resistance between the motor housing and the ground connection on the chassis.
Would you also think that anything <1Ω would be good enough? (It beeps on the DMM's continuity setting.) Without having changed anything from how I built the kit yet, from the spade lug/"faston" connector to the easiest to reach mounting screw on the left-hand motor it's ≈0.733Ω and only ≈0.075Ω to the motor's own screw on top that's nearest the center of the printer. The other motor is also reading <1Ω: ≈0.145Ω at either the motor's own screw or the mounting screw. I'm getting ≈0.04Ω just from the probes.
RE: Core One crash/restart
There's no such thing as zero ohms, but under a couple ohms on most cheap multimeters should be good enough. This accounts for poor connections, cheap leads, etc. Unfortunately, the continuity test can be as high as 100 ohms, I've even seen meters beep at 1k, so those probably don't count as 'good enough.' If you short the test leads and see under an ohm, the motor screw to to spade lug should be no more than an ohm above that base value (on most meters).
RE: Core One crash/restart
Thank you for the additional detail on that testing! Makes sense that an exact "0" is not achievable... I'll hold off on ordering those room-temperature superconducting star washers 😉
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I guess since we are being pedantic "There's no such thing as zero ohms" is not a true statement. But then I suppose since the CoreOne chassis is not a superconductor, yes it's going to be whatever the resistance is of the multimeters probes plus the resistance of the contact point and the resistance of the metal in the chassis. But all-in it will be in milli-ohm range.
There's no such thing as zero ohms
RE: Core One crash/restart
Hello everyone,
First of all, a big thanks to all of you — because spending so much money and then facing this issue alone would have been really depressing.
I tried to go through the whole thread, but it’s not that easy, so let me check if I got it right:
We need to remove one screw from each of the X and Y motors,
Scratch a bit of the paint under the screw head,
Add a star washer,
Then re-install the screw — and that’s it?
Thanks a lot for confirming.