RE: Core One crash/restart
I got my CORE One a couple of months ago and have only printed relatively small parts so far. Today I tried to print the TOTEM BLE Travel Case from Printables (22 × 15 cm) and ran into the same issue. I just saw your post — I hope the fix works for me too. Thanks for sharing!
What really bothers me is that Prusa hasn’t provided a solution, given how frequent this problem seems to be.
Thanks a lot to all who where involved in fixing that problem.
I ran into that issue after 6 weeks using my printer without any problems.
It was the first time I printed a plate of 190x190 mm.
The printer rebooted several times printing the first layer leaving nice blobs.I did not want to pollute my printer by milling the powder coating, so I went to a different solution which works fine.
I added two short cables to connect the motors to a definitely grounded screw.
The whole process took three hours, two hours for research and reading and one hour for fixing the problem.I have printed four of the plates mentioned above without any problem.
Thanks a lot again!Cheers
Ralf
RE: Core One crash/restart
Thanks for posting this (especially the photo). I just applied this mod to my C1L. I turned out to be easier than I expected.
My reboots were happening when I inserted or removed the smooth print sheet. So far, three sheet movements ad no reboots.
RE: Core One crash/restart
I'd love to hear from someone with a newer CORE One or especially CORE One L to see if it has been fixed in newer revisions.
It seems to be a matter of luck whether the pre-assembled printers are the stepper grounded or not. It doesn't appear to be actively checked or addressed. The Prusa instructions for the kits don't mention checking this.
On my factory-assembled Core One from May 23, 2025, the stepper motors are grounded by chance (I measured it).
RE: Core One crash/restart
I had the printer reboot in the middle of a print about three weeks before I sold my core one and divested myself of anything Prusa.
I did not have any subsequent issues but I did install a lock washer on one screw of each of the stepper motors so that it would ground to the chassis. it’s winter time here and the humidity is effectively 10% if that which will lead to more static electrical buildup.
Between that and the crappy experience with the MMU3 and any sort of manner to be able to properly use it with dry boxes, it was time just to go all Bambu, especially after the Customer Service experience with Prusa. (I had always been told that it was a good experience, but it turned out not to be a good experience. - if I’m gonna have to go through that crap, I’m might as well have a single ecosystem.)
RE: Core One crash/restart
Before trying what @ralgre suggested, I ran a few checks. It turns out the steppers weren’t grounded. I implemented a temporary fix (not as professional as @ralgre’s) just to verify whether it would solve the issue, and I wanted to share what I found.
I bought my CORE ONE+ factory-built, so I expected a professional assembly. However, I’m not sure this is acceptable — the screws labeled A and B, along with the symmetrical ones on the right side in the picture, were almost loose. This proves that @etadriver is absolutely right: Prusa did not follow its own instructions.
I kind of regret not buying the printer as a kit, like I did years ago with the MK3 and later the MK3S — amazing printer that still run smoothly and reliably.
Anyway, I took a Cat 6 cable and used one conductor, forming two small rings at the ends to connect the screw that secures the guide to the frame to the screw that holds the stepper in place. Damn! it worked — I printed the large object I wanted yesterday. Thanks again to @ralgre!
RE: Core One crash/restart
Received my C1L Jan 2 2026; been printing around 35% duty cycle since then. Have had this happen 3-4x to date, all when removing the satin print sheet. The last time it seems to have generated a crash log, filed bug and sent the log to Prusa. The first few times I wondered if the cable to the PSU wasn't seated properly, although I've had thousands of datacenter servers with no issues, but ??? So reseated it a few times.
Now wondering if it's the static issue you guys are bringing up.
Either way, definitely has happened on a 'new' C1L.
I'd love to hear from someone with a newer CORE One or especially CORE One L to see if it has been fixed in newer revisions. Seems like a tiny adjustment to the powder coating and possibly a washer are all that would be needed.
RE: Core One crash/restart
The simpler, the better!
Honestly, I am relly shocked by the poor response of Prusa support.
This problem came up about 11 months ago and was solved by the community 8 months ago.
Pusa's reaction: None!
I've bought my kit in December 2025. Enough time to fix for Prusa if they would have listenend!
But hey didn't!
Regarding support, it is worse than buying some Chinese stuff.
Why?
Buying Chinese, you normally don't expext any support, so you do not write about problems.
In this case, you rely on "Everything produced in Europe" and expect something.
So you spend your time sending your observations and expect something to happen.
But nothing happens.
Frustraded? No!
I am proud of being part of a really great community of amateurs and professionals, who are able to solve almost every problem!
And by the way, it is the best printer I ever had.
RE: Core One crash/restart
Even after grounding all of my steppers, I had another crash/reboot while inserting the smooth sheet back into the printer. They don't happen as often, but they still occur. Later, I had the machine off and the lights were low in my office and I could actually see the sparks between the sheet and the guide posts at the rear of the bed. This happens almost every time I lift the smooth sheet off of the bed. I can post a video if needed.
My workaround, to protect the electronics, is in the future I will just turn the machine off whenever I need to move the sheet.
RE: Core One crash/restart
Hey everyone, I had the EXACT same thing as Gregg. I walked across the room and touch the print plate the the heat bed and had a crash. It doesn't seem like Prusa has resolved this yet. I had already bonded and grounded the X and Y motors. Today after the incident I checked resistance betheen the bed assembly and ground and got 11M ohms. I bonded the entire bed assembly and now have 2 ohms. Running the same print for a test.
RE: Core One crash/restart
Hey everyone, I had the EXACT same thing as Gregg. I walked across the room and touch the print plate the the heat bed and had a crash. It doesn't seem like Prusa has resolved this yet. I had already bonded and grounded the X and Y motors. Today after the incident I checked resistance betheen the bed assembly and ground and got 11M ohms. I bonded the entire bed assembly and now have 2 ohms. Running the same print for a test.
RE: Core One crash/restart
Hey everyone, I had the EXACT same thing as Gregg. I walked across the room and touch the print plate the the heat bed and had a crash. It doesn't seem like Prusa has resolved this yet. I had already bonded and grounded the X and Y motors. Today after the incident I checked resistance betheen the bed assembly and ground and got 11M ohms. I bonded the entire bed assembly and now have 2 ohms. Running the same print for a test.
In this case the charge was probably not built up during a print, but you were carrying it? I assume you did not touch any frame part before you touched the bed?
Still, the printer should tolerate this; I am pretty sure that robustness against electrostatic discharges is part of the required compliance tests. Since all bed mounts (trapezoidal nuts and linear bearings) are attached via printed plastic parts, I think it's a safe bet that every Core One has a non-grounded heat bed. The discharge pulse may have found a way through the heater/sensor cable right to the xBuddy board.
Where does the ground wire you installed go? Is it a long cable, attached to a stationary frame part on the other end?
RE: Core One crash/restart
I'm not entirely sure and don't have the printer in front of me. Is the Core One's door handle made of metal? If so, I'm trying to figure out how to connect it to the frame so it automatically discharges when you touch the handle, eliminating the need to manually touch the frame before removing the print sheet. It's just a workaround; the Z-carriage also needs to be grounded.
RE:
I'm not entirely sure and don't have the printer in front of me. Is the Core One's door handle made of metal? If so, I'm trying to figure out how to connect it to the frame so it automatically discharges when you touch the handle, eliminating the need to manually touch the frame before removing the print sheet. It's just a workaround; the Z-carriage also needs to be grounded.
The idea of grounding the handle had crossed my mind too while I was writing the reply above. But with the large polycarbonate sheet to bridge, that would end up looking a bit messy, I think.
A dedicated ground wire from bed to frame, which is included in the bundle of heater wire and temperature sensor connections, it probably the best solution. Prusa should really have provided this -- ESD immunity is part of the IEC 61000 compliance requirements. As far as I know, the required test involves zapping all parts of a device which the user would normally handle with an ESD gun and checking that the device continues to operate normally.
RE: Core One crash/restart
I understand, but in mechanical engineering, appearance should play a subordinate role to function and safety. Let's see, maybe a contact between the door and frame at the handle. Perhaps copper tape on the handle. It doesn't have to be perfect, it just needs to provide support.
RE: Core One crash/restart
Personally I have not encountered this static discharge issue: My Core One lives in the basement, where the air is not that dry and the concrete floor does not induce charge buildup. But If I wanted to ground the print bed, I would just add a ground wire to the "umbilical cord" with the heatbed connections.
No need to disconnect the existing heater and thermistor cables; the textile sleeve is open along the side so you can just slip in another wire. On the heatbed side, guide it into the plastic connector cover and out on its side again, together with the thermistor cable. On the opposite end, you will have to cut and reinstall the cable tie which secures the umbilical cord to the chassis. Then it should be no problem to guide the wire into the back compartment and find a suitable grounded mounting point there.
RE: Core One crash/restart
Just a FYI, I gathered up all the feedback in a report and submitted it to our product team to review.
Shane (AKA FromPrusa)
RE: Core One crash/restart
Just a FYI, I gathered up all the feedback in a report and submitted it to our product team to review.
Great, thank you! Just to clarify, the thread is discussing two separate issues:
- The printer can build up static charge on its own, via extended, rapid belt movements, eventually resulting in crashes mid-print. The X/Y motors need to be grounded to avoid this. Grounding is easily achieved via the motor mounting screws, by ensuring that at least one of them has electrical contact with the CoreXY frame. Just masking off the area around one screw head during powder coating, and then adding a star washer beneath the screw head, would do the trick.
- The more recent issue, where the printer crashes when the user touches the heatbed, is different. The charge is probably "brought in " by the user, after walking on synthetic carpet, sitting on an office chair covered with synthetic fabric or whatever. But under the applicable CE standards, the printer should tolerate discharges up to a certain level. Again, grounding the heatbed to the frame seems advisable and should address this issue.
RE: Core One crash/restart
I submit that there is a third scenario: Removing and inserting the smooth print sheet. When I remove the smooth print sheet, I see and hear a spark at one of the guide posts at the rear of the bed. This happens any time, whether the machine is off or on, whether its been printing and just sitting there all day. It seems that the act of bending the sheet generates the electrical charge. I can provide a video of this happening if needed.
RE: Core One crash/restart
The wire follows the loom and grounds to the ground screw at the bottom right in the wiring box. Static electricity can go through anything, not just metal. The print sheet should have a way to discharge. I just added another bond. It goes from the other bond point I put in to the bottom of one of the two round headed screws that the print plate aligns to when you put it in. I 3d printed a tiny adapter that fits on the top of a spring. The bond wire goes through the spring, through the middle of the adapter, then the conductors fan out over the top of it and are held in place by the spring fitting snug over the adapter. This conductive, spring loaded assembly sets under the bed and bonds the little nub under the heat plate. The top of that is a threaded rod that we all have sticking up to align our print plates to. The edge of the print plate is touching this all the time (if you put your bed on right). The movie attached is of a Foreign Voltage Detector touching the plexiglass side cover during a print. It shows just how electrically active these printers are. Have done a few prints since adding the bonds. So far, no issues.
RE: Core One crash/restart
I've had this happen once when inserting the build plate. I chalked it up to accidently hitting the rear lead screw and static discharge. I've been careful to avoid that and (knocks on wood) it's never happened again. IMHO, the Core One could use some attention to what they call "ground bond integrity" because the powder coat is so good.