RE: Core One crash/restart
I'm feeling confident that Prusa did no real world testing with the C1L, only in house. All of their reviewers are still receiving the printer. I'm finding dumb stuff that should have been noticed. Like the cable/ptfe support arm is held by a post with a tension cap on both ends, didn't take long for the arm to drop, allowing the ptfe tube, which was installed wrong to hit the top of the fan housing, as the arm moved. I fixed the tube and then the wire harness was hitting, replacing the post with a real M3 and lock nut solved the issue, keeping the arm in alignment.
RE: Core One crash/restart
Juste to give a fast feed-back, since I fix the ground problem of both motors, I never had the reboot! it was the problem. Every onw must do the modification!
RE: Core One crash/restart
Had today morning the same problem, got mine 2 weeks ago. The first "larger" print, had 4 reboots, luckily found this thread and measured the resistance from the X-Motor, which was not good. So this afternoon i brought serrated washers (Fächerscheibe in german) installed them and now the resistance seems good. Will see it when i print the same file from today morning again.
But thanks for the people that found this problem 😀 👍
RE: Core One crash/restart
Have been struggling with this issue for months. This fixed worked for me. Thank you for all who worked through this and did the troubleshooting. Yall are legends
RE: Core One crash/restart
Picked up an assembled Core One the week of Christmas and it had been running perfectly (other than having to pay extra for a camera and hardened nozzle). The first large surface area print (9.75 hours) failed 3 times in the first 20 minutes. Thankfully I was near but had planned to leave the printer running over night…. I took off the left panel tonight and can confirm the left motor was not grounded at all.
The issue is this a longer shoulder bolt, so it nearly passes through the frame and threads into the motor. So the flat under the head is the easiest and more straight forward way to ground. Used a flat drill bit for a couple revolutions to clear the coating and confirmed it was grounded. Hoping this fixes the issues and will report back.
This is a design miss and I was so pumped because my printer is in a finished (carpeted) basement and I’ve been having to ground myself before I touch my MK3 for 3 years. So fingers crossed the Core One is back in action tomorrow.
Picture after modification, can’t even tell… other than with a multimeter. And picture of the print that was causing the rebooting.
RE: Core One crash/restart
Reran the same g code and it printed flawlessly. Ran a few other large files without issue. It appears that grounding was the issue. Solved thanks to the folks here.
RE:
I have had a Core1 since late November 2025. For the most part been very satisfied, although a few challenges with the MMU3 to get the hang of it vs running without the MMU3. My Core1 was factory assembled , and I had to build the MMU3 from the Prusa kit of parts which was a bit of fun but time consuming to do it properly and carefully.
Initial prints were fast and super satisfying.
In the past 2 weeks I noticed my prints degrading with resonance symptoms wavy lines, and also very regular crash reboots (with 10 beeps)
I discovered the resonance lines were due to the entire print head being loose on the gantry linear rail carriage , this must have worked loose. I tightened the cap screws to fix it to the carriage properly and then did the belt resonance tightening and gantry alignment.
The reboots continued and I did a number of actions incl connecting to aa better wifi network in our building, checking all connectors I could within the printer, fw was already up to date. No better.
Although the room humidity is reading about 55% I did take the warnings about static seriously. I reduced my print speeds but that didn't help.
Today I removed a stepper motor screw off each motor and removed the power coat back to bare metal as recommended.
Voila! Printer seems stable at this stage , fingers crossed this issue is sorted.
Thank you to the clever folk who troubleshooted and recommended this adjustment. I am a little bit disappointed that Prusa let this sort of issue slip through on a relatively pricey , albeit "Prosumer grade" machine.
Have any other folks had problems with factory assembled machines and loose gantry carriage screws ? Or other issues ?
Thanks, Richard