RE: Core One crash/restart
I had this issue as well. when the printer goes from rear right side to front left side, I notised that the left rear motor moves but the other one almost stay still, when the printer restarted like a power cut. Grounded the left rear motor, problem solved. I fastend a cabel on one screw that fastend the motor. and other side a random spot on the frame
RE: Core One crash/restart
I added the star washers to both my X and Y axis motor, verified I have continuity from the frame to each motor with a Fluke Voltmeter. I have been printing for over 10 days without the issue popping up.
RE: Core One crash/restart
I had two prints fail this weekend with a ton of travel and crashing. While I wait for my 3mm washers to arrive I cut a test lead up and that same print ran last night without issue. Seems like the answer. I’m going to set up my o-scope and try to measure this someday. 
RE: Core One crash/restart
I had two prints fail this weekend with a ton of travel and crashing. While I wait for my 3mm washers to arrive I cut a test lead up and that same print ran last night without issue. Seems like the answer. I’m going to set up my o-scope and try to measure this someday.
In my case I just scraped away some powder coating from around the screw hole. That was enough to get a decent ground connection.
- Bob Marley
RE: Core One crash/restart
I ran into this issue and fixed it with star washers as well. What's odd to me is how the printer ran fine for months after assembly and then suddenly started crashing almost every time I ran a print. I did just change the filament spool before that but it was a new spool of the same material I had already been using. Maybe the belt tension has changed over time which somehow leads to this problem happening more often or earlier in a print with diagonal movements?
RE: Core One crash/restart
Same problem here: sudden blackout of the machine during print while performing diagonal movements. Grounding the motor solved the issue for me as well (see image for the dirty hack 😉
Problem can be replicated by printing a flat square covering almost the complete bed. Error occurs at the first layer. I also tested printing a small square at each corner at the same time to test whether the motion to the edges of the print bed cause any problems. No problems here.
Belt tension has been configured using the app. Worked for me and prints look awesome. Seems like the grounding really does the trick. Thanks a lot for sharing this solution!
RE: Core One crash/restart
Hey all,
Firstly, I wanted to thank the people in this thread for discovering the cause of the rebooting problem. I'm sharing my experience with this issue and showing some photos of how I fixed mine just in case others run into the same problem. I did read all eleven pages of this thread and did see people asking for photos, and perhaps like me, it maybe isn't super clear which screws need to have the powdercoat removed, so I'll provide photos.
A bit of background: I had about 5 jobs on my preassembled Core One print just fine, some of them even using the full X and Y dimensions of the build area with no issues. Most of these projects weren't super complex, just caddies for things. Most of these projects had rectilinear features and most had rectilinear supports (one had grid supports I think) and so the printer was generally moving in one axis most of the time. All were printed with PLA with 0.15mm layer height.
Then a family member asked me to print this caddy for their bathroom:
Prusaslicer sliced it in a way where pretty much most of the infill of the print is on the diagonals (e.g. using both X and Y motors at the same time). Even the thin bits at the front and back were infilled diagonally which resulted in a lot of sharp movements of both motors. This can be seen from a screenshot I took of the buddy camera below while it was printing (the image is of the successful one after I applied the powdercoat scrape mod):
I had multiple failures in printing this part. I tried at 0.15mm 30% infill twice, then 80% infill, then I tried 100% infill at 0.2mm layer height.
I was getting the dreaded rebooting with the 8 - 10 beeps every couple of layers. The machine would restart, go back to printing after a minute or two, but the material would gunk up in this period and it blocked the print head once which I cleared by heating the nozzle 20 degrees above PLA melt temp. When I tried at 0.2mm layer height and 100 percent infill, the machine eventually did finish the 18 hour job (in Stealth mode - I print everything in Stealth mode), but it finished it about 4 hours late due to all the restarting and the quality of the print was not fantastic due to the semi cooled plastic screwing with the consistency of the print. There were also a bunch of PLA guzzies sticking out of the side which I had to sand off.
On one occasion during one of the failed prints I saw the red 'power panic' page, which made me think it had something to do with the electronics. I went searching online and found this thread thankfully. I don't have a multimeter, but I figured it was the problem described here - either the X or Y motor belts (or perhaps a combination of both) causing a build up in static. I also went looking in the Prusa construction manual to isolate which bolt holes had to be worked on on either side. Only one of these four bolts with the arrows below needs to have the powdercoat removed underneath it as all you're trying to do is to create a ground path:
I took a trip down to the local Bunnings (hardware store) as I was looking for a little Dremel bit to scrape the powdercoat off. Strangely enough, the moment the helpful older chap heard I was trying to scrape off powdercoat around a drill hole, he exclaimed "Ah! You're trying to chase down a short." Bingo. In another conversation I had with a friend, apparently this is a common problem with powdercoated parts and automotive electronics - something is shorting and it's difficult to figure out what it is. Powdercoat is an insulator. This is the dremel bit I used to shave the powdercoat off:
Here is the most accessible bolt on the left hand side of the Core One if you're looking at it from the front on the inside (shown after powdercoat removed and star washer attached). You can remove it with a small allen key, but be careful, it's a tedious process and the allen key likely will slip out of your hands, so have a magnetic-tipped thing (screwdriver) handy:
A slightly more zoomed out image showing the hole in relation to the rest of the body:
The bolts are pretty long - they attach into the motor (the top most black cube in the image above). I attached a zinc plated star washer as per recommendations:
Here is an image of the bolt hole I worked on on the other side of the machine (the other stepper motor, once again with the powdercoat already removed and star washer inserted):
After doing this powdercoat scraping mod, I reprinted the exact same gcode with the exact same material and the print finished on time (indicating there was no hold up due to reboots). I watched the print through several phases of it and where it failed before, it sailed right on through without a hitch. Here is an image of the final print after the mod - it printed pretty much as good as I could hope for:
To be 100 percent transparent, I replaced the power cable and the extension cord to the printer at the same time I did this mod, so there is the possibility that one of those other things fixed it, but I'm just sharing what I did. Perhaps start with replacing those items first, and if that doesn't work, then you know...
RE:
Thanks for this sollution.
I was staring to wonder If my hardware was just faulty and about to contact prusa support.
I have installed the groundings yesterday on both X and Y steppers and grounded them via the top screw of the power supply.
I am currently running a job that would reliably trigger the restart / crash condition.
About 2 hours into the print and no problems yet.
I will update this post when the print finishes (total print time about 1 day) but I hope to report that no crashes occured.
RE: Core One crash/restart
Hmm I seem unable to edit my post.
Maybe to much time has elapsed.
But to get back on subject.
My print (A gridfinity box) has finished without any problems.
So I would say this solved the problem.
RE: Core One crash/restart
I guess my question is how is this different from the grounding provided by the grounding pin an inch to the right of the screw you selected? Would it not be sufficient to simply validate that at least one contact point makes ground to that pin? What resistance are you seeing to ground on the pin vs your solution?
Here's three pictures of how I handled grounding the stepper housings on my Core One.
This is the X-axis stepper motor on the left side of the printer when looking at it from the front. The camera is looking up from below with the left side panel removed. You can see the plastic top panel in the background. The green arrow shows which screw I removed and attached the old heatbed cable to. I used that cable because it has ring terminals on both ends. I reused the same screw and there was enough length to still secure the stepper motor even with the ring terminal on it.
This is one of the xBuddy box mounting screws, also on the left side. This is the other end of the above mentioned cable. Again I reused the screw here and still had plenty of length left over to secure the xBuddy box.
This picture shows an overview of both of the above photos. The stepper motor and the xBuddy box with the wire connected between. There's a decent amount of spare cable here so I shoved the excess through the hole with all the other cables you see there. When I was all done I verified continuity between the stepper motor and the chassis ground using my multimeter. I repeated this procedure on the right side to ground the y-motor stepper housing. It looks basically the same so I didn't take any pictures of that side.
Again, this isn't the only way to ground the stepper motor housings. You could (in theory) simply remove the screw shown in the first picture, sand off, or somehow remove the powder coat from the gantry down to the bare metal and reinstall the screw. That should be enough. A toothed washer might also work if tightened enough.
RE: Core One crash/restart
I guess my question is how is this different from the grounding provided by the grounding pin an inch to the right of the screw you selected? Would it not be sufficient to simply validate that at least one contact point makes ground to that pin?
As discussed in various other posts here, it is sufficient that at least one of the four mounting screws (for each X/Y stepper motor) has contact to ground. That can be achieved by a dedicated ground strap attached to the screw and to some mounting point on the chassis, as shown e.g. by @darkmattermaker. Or, more easily, by scratching away some paint from the CoreXY frame beneath one of the screw heads, and/or inserting a toothed washer.
The CoreXY frame is already grounded in all Core Ones via a factory-installed ground strap. It's the fact that in some units all motor mounting screws (and hence the motor chassis) are isolated from the frame which causes the static charge problems.
RE: Core One crash/restart
On my machine, the powdercoat on the frame isolates the motors from that grounding post, there's no continuity between them. I tested this with a multimeter.
At the time I installed this grounding strap it was unclear whether or not this was the cause of the issue. With that in mind I didn't want to make any permanent modifications to the printer (i.e. scraping off powdercoat) so I chose this method instead.
I hope that clarifies why I did it this way and not another.
I guess my question is how is this different from the grounding provided by the grounding pin an inch to the right of the screw you selected? Would it not be sufficient to simply validate that at least one contact point makes ground to that pin? What resistance are you seeing to ground on the pin vs your solution?
Here's three pictures of how I handled grounding the stepper housings on my Core One.
This is the X-axis stepper motor on the left side of the printer when looking at it from the front. The camera is looking up from below with the left side panel removed. You can see the plastic top panel in the background. The green arrow shows which screw I removed and attached the old heatbed cable to. I used that cable because it has ring terminals on both ends. I reused the same screw and there was enough length to still secure the stepper motor even with the ring terminal on it.
This is one of the xBuddy box mounting screws, also on the left side. This is the other end of the above mentioned cable. Again I reused the screw here and still had plenty of length left over to secure the xBuddy box.
This picture shows an overview of both of the above photos. The stepper motor and the xBuddy box with the wire connected between. There's a decent amount of spare cable here so I shoved the excess through the hole with all the other cables you see there. When I was all done I verified continuity between the stepper motor and the chassis ground using my multimeter. I repeated this procedure on the right side to ground the y-motor stepper housing. It looks basically the same so I didn't take any pictures of that side.
Again, this isn't the only way to ground the stepper motor housings. You could (in theory) simply remove the screw shown in the first picture, sand off, or somehow remove the powder coat from the gantry down to the bare metal and reinstall the screw. That should be enough. A toothed washer might also work if tightened enough.
RE: Core One crash/restart
I’ll have to give this a go but I don’t expect much in my case. Just checked my resistance to ground by probing ground at the power connector to the indicated bolts on my x/y steppers. x is 0, y is 0.1-0.3. Suppose I’ll try the gator clip method and see. I have only witnessed my power failure once but I did a print last night which was running good for around 5 hours before I saw the symptoms in the telemetry described here.
RE: Core One crash/restart
Well, after another crash (3rd one) 40% way through a large print I was going insane. Popped off the side plates and probed every stepper to check for resistance to ground. Turns out I checked the wrong screw... I was hitting my rails screws, and not my steppers... Both X and Y had no connection to ground. Connected the steppers to ground and fired up the print again and it completed this time. What a headache.
RE:
Just got a Core One and appear to be having the xy motor crash issue. I was able to capture it on video which hopefully helps to document the issue. Crash happens at 2m 56s and should be directly linked in the embed. Full video just shows a full crash cycle from the end of one crash -> the print going for ~2min before crash again -> printer going black and rebooting.
#t=2m56s
Waiting on some star washers before I ground my motors. Thank you all that contributed to troubleshooting and solutioning the issue!
RE: Core One crash/restart
Thought I'd share my version of the fix.
Firstly, I haven't actually had any reboots (that I noticed). But I confirmed with a multimeter in continuity test mode (it beeps when there's continuity which is very convenient) that my left XY motor wasn't grounded. The right XY and three Z motors were all grounded. So I figured I should pre-emptively ground my motor.
I wanted a quick fix so decided to use spade connectors - these allow you to just loosen a screw and slide in the connector without having to completely remove the screw. My spades were bigger than M3 but fit under the screw heads well enough. The thickest wire I could find is still a bit thin but stranded coper at least, and I checked continuity once crimped before installing. I found 2 screws at the back right of the motor - one that connects to the motor and one that is grounded. Hence I was able to make my grounding wire short, neat, and easy to install.
RE: Core One crash/restart
Indeed a nice, clean solution for those that do not want to scratch away a little of the coating. Even if this works for you (tested with multimeter) I wonder if the "grounded" screw is so by design or simply because, when inserted, it randomly scraped the coating from the thread thus making a connection with the frame. In the latter case it would not work for everybody...
RE: Core One crash/restart
Even if this works for you (tested with multimeter) I wonder if the "grounded" screw is so by design or simply because, when inserted, it randomly scraped the coating from the thread thus making a connection with the frame. In the latter case it would not work for everybody...
That screw just behind the four motor mounting screws goes through a through-hole in the CoreXY frame and is screwed into the plastic mounting block for the motor. So you can't rely on it making contact with the CoreCY frame: Just like with the four motor screws, it will only do so if there is a gap in the powder coating inside the through-holes and the screw touches the frame in that spot.
For a reliable (i.e. available in all printers) ground connection one would need a screw which is actually screwed into the grounded CoreXY frame, preferably with a self-cutting thread. But I don't think there is any nearby. So the ground lug near the left-hand motor is the best connection point for a jumper cable. Or just scrape off some powder coating under a motor monting screw, which is still my personal preference.
RE: Core One crash/restart
Thanks @chmax that's important feedback. There are some clear pictures of those holes in the assembly manual, and indeed the "ground" screw I chose goes through an unthreaded hole which appears to be powder coated. As you say not a good choice for others to follow! The Y bar ends do screw into threaded holes so they're better (just checked mine and they are grounded) but a they're an awkward shape and I'd worry about clearance. So any of the other threaded holes people have already suggested would be best.
Looking at those picture both left and right motors seem to use unthreaded holes so I wondered why most people seem to only have issues with the left... but looking through the thread I did see someone have an an ungrounded right motor too. A star washer and powdercoat scrape on both seems like the most robust solution; I may go back and do that at some point I just don't have any star washers and the scraping seems awkward. I'll wait 'til I upgrade/service something else in there.
Good news though is all these screws are under tension from the core-XY belts so if someone's motor is already grounded that's unlikely to change.