RE:
Based on the other posts here, I improvised a way to ground the X-Axis motor yesterday. 24 hours of successful prints without a single restart! 😎
Special thanks to @darkmattermaker and @noumenonsense. I would never have figured this. 🤣
Am I right to assume that this is a Quality Control issue and the Prusa needs to replace the motors for the affected machines? Surely the wiring running to the main board, should include a ground for the whole motor unit?
I also agree with @N8&Joey, it would be helpful to see how you've ground your units. As one of the posts mentioned the silver screws at the top of the motor, I connected a wire to each that then connects the grounding "thing" (very formal technical term there... 😐 ) on the frame underneath the X-Axis motor. I suspect this is overkill and I probably just needed one wire to the metal casing of the motor?
It feels so good to be able to get back to printing! 😆 I mean other than this restart issue the CoreOne has been great!
RE: Core One crash/restart
I'm happy to share pictures. I actually meant to take some while I had it apart but completely forgot in my haste to get to testing. I've got a busy next couple of days coming up so it might be a few days before I can pull it apart again. Those plastic rivets are a huge pain in the butt.
For what its worth, I didn't mess with the screws visible on the top of the stepper. I used the mounting screws on the bottom of the stepper. There's four M3x35 screws that hold the stepper, face down, onto the printed motor mount. Here's a picture from the assembly guide that shows the ones I'm talking about:
I removed both side panels so I could get access to the screws shown above towards the rear of the Core One. When the gantry is installed in the Core One these screws are facing down. I removed one screw, slotted it through the hole my old MK4S heatbed cable and reinstalled it in the hole I removed it from.
I connected the other end of the cable to either the key-hole screws holding the power supply to the back cover, shown above. On the other side I used the key-hole screws holding the xBuddy box in. These screws are only visible with the side panels off because they're hidden behind the rear angled corners. I didn't muck about with the existing chassis grounding cable or connectors.
I know all that doesn't make a lot of sense without pictures of it. Ill try to get some taken soon.
RE: Core One crash/restart
Thanks @darkmattermaker, that makes good sense!
As you mentioned in an earlier post, a quick and clean alternative would be to remove the powder coating from the CoreXY frame under one of the four screw heads in your first picture. I would just remove the screw and try a few turns (by hand) with a large drill bit to scrape off the paint. Maybe insert a toothed washer as well for good measure, to make sure good contact is retained long-term.
RE: Core One crash/restart
Am I right to assume that this is a Quality Control issue and the Prusa needs to replace the motors for the affected machines? Surely the wiring running to the main board, should include a ground for the whole motor unit?
No, it is a design issue. Before powder-coating the CoreXY frame, Prusa need to mask off the areas where the motor mounting screw heads meet the frame, at least for one screw per motor.
The motor connection wires just go to the motor windings (2 windings, 2 wires each). That's standard on all stepper motors of this kind. If you need to ground the motor chassis, you do that via its mounting points.
RE:
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
Following up on my own post here. I've got the printer going on a 12 hour print. It's 4 hours in and hasn't crashed/restarted once. Last time I tried this print it crashed repeatedly, every few minutes. I'm going to say that grounding the stepper housings has definitely resolved the issue on my machine.
RE: Core One crash/restart
I'll chime in as well. Since I grounded the X motor, I've had multiple successful prints over many days of operation and to my knowledge the printer hasn't rebooted once.
I let Prusa support know what I found, and they thanked me for the help, but they are sending me a new X motor and want me to send the old X motor back. Based on my understanding of the issue, I don't believe they are going to find anything wrong with my current X motor. Maybe they know something I don't? I feel like my static theory makes more sense than an internal motor defect based on how well the fix works and the other information in this thread.
RE: Core One crash/restart
Thanks for all of the helpful hints! I took the path of clearing a bit of the powder coating on the two stepper motor areas and after some other major issues in bringing the printer back to a print state, I’ve managed to successfully (so far) print a few small jobs and one medium one that was giving me problems at the onset. However, in reviewing the telemetry for the print job I see “events” logged where normally a reboot would happen - though it’s not happening now. Would it be safe to say that the root issue is still happening, but the grounding is stopping the power panic reboot? See the telemetry image below:
RE: Core One crash/restart
Is it this cable you move to ground to the chassie?
RE: Core One crash/restart
Is it this cable you move to ground to the chassie?
No, don't do that. That's the negative end of the heatbed cable, your printer won't work without it. The cables shown above are new, not already installed in the printer. If you're not familiar with electronics and basic wiring it might be better to just work directly with support. If you connect something wrong you could badly damaged your printer.
RE: Core One crash/restart
I think my issue is, I dont get where the mounting should go from the steppermotor.
I get you place the cable on the frame shown on both pictures. What i dont get is where the two cabels go.
RE: Core One crash/restart
I think my issue is, I dont get where the mounting should go from the steppermotor.
I get you place the cable on the frame shown on both pictures. What i dont get is where the two cabels go.
It's not two cables. It's one cable. It probably looks like two because the cable was too long and I pushed the excess cable through the hole with the rest of the cables. One end to the stepper motor screw, one end to the xbuddy mounting screw. That's it.
RE: Core One crash/restart
Really, it is easier to scrape off some paint from the CoreXY frame -- such that one of the mounting screw heads touches bare metal. No additional cable and connector required. If you do it e.g. with a drill bit, you can scrape off just the area below the screw head. It will be invisible once you put the screw back in, and you will ground the motor body to the CoreXY chassis in the most direct and reliable way.
RE:
Shame this fix did not work for me :/ I still get it but now its even worse. When the print starts the first crash results in re-crashing when zeroring...
RE: Core One crash/restart
Just finished my core one kit yesterday and had several small prints be fine. But now am on a 7h print and it’s doing this. On firmware 6.3.2.
is the “fix” at this point this grounding change, or have people found other fixes/causes?
RE: Core One crash/restart
Just finished my core one kit yesterday and had several small prints be fine. But now am on a 7h print and it’s doing this. On firmware 6.3.2.
is the “fix” at this point this grounding change, or have people found other fixes/causes?
I haven't seen anyone chime in with any other fix. I've only got one Core One machine and I spent a ton of time troubleshooting this issue. The only thing that fixed it for me was grounding the stepper housings for both x- and y-axis motors. To be fair, I didn't ground them one at a time and retest in between. I just wanted it fixed so I grounded both motors while I had everything apart. It's possible grounding just one stepper would have been enough, I can't be sure.
RE: Core One crash/restart
Did the work yesterday after repeated crashing. Removed one screw per stepper, scrapped some paint away with a drill bit, and then put screw back. Both steppers seem well grounded now. Prior, X stepper was grounded, but Y was spotty. Both have a good ground now. Also replaced power cable with one that fit much more snuggly.
So far so good, but need to try a larger print with more non-print jogs. Thanks!