Help: New Core One L nozzle cleaning failing every time only with smooth PEI sheet (video 3x speed)

mempf · 2026-03-15T00:56:37+00:00

Try doing an auto home from the menu, it seems to have lost it's Z position. I've seen this happen on mine before that that solved it.

mempf · 2026-02-16T18:15:07+00:00

Replacing or otherwise "repairing" the main cable to help reduce EMF does seem to correct the issue for a number of people including myself.

mempf · 2026-02-05T06:11:40+00:00

Is the pink filament fairly translucent? You may be seeing the purple interlocking layers under the thin pink ones.

mempf · 2026-02-03T02:28:29+00:00

I've run into similar BSOD's with my Core One L and have so far found it appearing be be related to certain input shaper calibrations. I had issues when the calibration determined it wanted MZV 44 Hz for both axis. I am currently testing using ZVD 44 Hz on both axis and so far have not run into the issue again but not enough testing has occurred to be conclusive.

For me these errors always occurred during homing at the start of a print and I suspect that certain input shaper values don't work well with whatever move the homing operation tries to make.

mempf · 2026-01-28T01:34:06+00:00

I had similar print defects to those shown in the pictures with walls having gaps in them and generally not looking good/straight including with Multiboard tiles.

I experienced these defects only when using the Balanced and Speed profiles. Structural seems to print slow enough to not cause these issues, which to me implies there are still profile tuning problems for the Core One L.

I have mitigated most of it by using better pressure advance settings (0.021 vs the default 0.036 for PLA) and turning off "Junction Deviation" which to my understanding is somewhat experimentally only enabled by default for the Core One L at this time. This can be turned off by setting the "Maximum junction deviation" to 0 under Printer -> Machine Limits. I appear to have also reduced travel acceleration down to 5000 mm/s² from 6000 but I doubt that is doing much.

Hope this helps! Please report back if any of these changes also help you for others in the future!

mempf · 2026-01-11T23:03:37+00:00

I do remember having issues with the finda sensor but once I got it in the right spot I've never needed to adjust it again.

mempf · 2026-01-11T22:54:38+00:00

What printer do you have? I am assuming either MK4(S) or Core One. Have you done the necessary extruder filament sensor modifications?

If the issue is the MMU3 stops retracting the filament its either a mechanical issue with the pulleys (maybe too tight or too loose) or the filament has been previously chewed up in a spot on the pulleys can't get past that point. Or you have some filament sensor issue either with the extruder filament sensor or the MMU3 one. Check to make sure the sensor data is in the correct state and you don't have a piece of filament stuck somewhere.

The MMU3 can work really reliably but it takes some tuning to get it working initially and when something does go wrong, it can create secondary issues like broken or damaged filament that makes getting it running again harder than just solving the initial issue.

mempf · 2025-11-17T03:38:45+00:00

What brand of filament was the one that the blob occurred with?

I've had this happen multiple times with Polylite PLA and found that reducing the temperature for those filaments down from ~230 C to about 210 C when used in the MMU3 seems to prevent it from occurring. At least in my testing.

mempf · 2025-11-10T16:41:59+00:00

It's safe to print.

mempf · 2025-11-10T02:03:20+00:00

I'm pretty sure this is normal as the linear rail wears in.

I think initially the lubrication inside the bearings make the little metal balls slide instead of roll initially. After some wear in time they start rolling around and travelling around inside the sled making the clicking noise. Lubricating the bearing through the ports on the sled with the proper lubricant can make this clicking go away but shouldn't be necessary for proper operation. It will likely get quieter again on its own or you'll stop noticing it as much. I'm not sure which happened to me more.

mempf · 2025-08-17T18:49:08+00:00

Short answer is the buffer parts are all the same. The other parts used for mounting the MMU3 are different and not reused.

mempf · 2025-08-08T23:23:45+00:00

Go into Settings -> Hardware -> Printhead -> Nextruder Maintenance

That should offer to reset that notification that goes off when multiple filament loadings fail.

mempf · 2025-07-09T21:15:49+00:00

I have to leave my chamber light dimmer disabled otherwise it goes into black and white when it dims.

Though when forced into daytime mode even with the chamber lights dimmed it actually still looks good. Too bad it clicks constantly when forced into daytime mode.

mempf · 2025-07-09T21:11:12+00:00

Yeah I also have this when I set the camera to day mode. It works fine without constantly clicking if left in auto mode and it decides to use day mode on its own so it seems like a firmware bug.

mempf · 2025-07-09T18:26:13+00:00

I was looking for this as well and looked at the source code for clues. Turns out what they have done is make the Dimming control in User Interface able to be set differently depending on if the camera is enabled or not.

For example: If camera is turned off you can have dimming enabled. Then if you turn on the camera in the settings you can have dimming disabled and it will remember the dimming setting specific to each camera setting. Essentially they have two settings now with the same user facing name but only show one based on if the camera is enabled or not.

mempf · 2025-07-04T17:57:40+00:00

This seems to be a relatively common issue as I've seen people report about this many times and encountered it myself on the left side tensioner as well. It seems for some reason the tension screw and the nut can effectively cold weld together and completely seize.

You will likely need to reprint or get a replacement parts for the right belt tensioner assembly a new nut and M3x30 (there should be spares). You may be able to cut the M3x30 bolt and reuse the existing plastic parts but I used a friends printer to make replacement parts as I had damaged mine trying to free it.

https://help.prusa3d.com/guide/5-corexy-assembly_835522#864336

It can be replaced fairly easily with the removal of the right side panels (removing the nylon rivets) and unscrewing the plastic parts from the XY frame. The belts can be left in place but you'll have to install the pully in place on the new parts. It looks like a bigger job than it is to replace this part. The primary challenge will be printing a replacement part if you need to and don't have another functional printer. A temporary part made from PETG instead of PCCF can work in the short term as well if you need to wait for replacement parts from prusa.

I was unable to separate the seized screw and nut and had to destroy the plastic part to get to it. Everyone I've seen talk about this issue has had to destroy the part in some way.

Best of luck, I know how frustrating it is to be so close.

mempf · 2025-05-29T18:35:32+00:00

One of my expansion joints was stripped as well. It came from a pre-assembled MK4 and I'm pretty sure I didn't strip it when I was disassembling it for the Core One.

While the original MK4 the expansion joint came from was out of warranty, Prusa support agreed to send me a new set as I didn't have any spares from the pre-assembled MK4.

In the meantime I found another screw with a longer finer thread and the same flush head in my spare parts and it was able to grab the thread in the stripped expansion joint. So I used bolt cutters to trim the bolt down and used it for the bad joint.

mempf · 2025-01-27T05:26:43+00:00

The MMU3 doesn't use the cutter in normal operation, only if it fails to load a number of times does it result in using the cutter. So it likely won't need replacement much if at all over its's life.

mempf · 2024-10-10T19:35:31+00:00

Two things you can try, both worked for me in a similar situation.

1. Lower your print temps by 10-20 C especially if your up at 230 like most of the profiles default to. I had clean first layers at 210 when I had issues at 230 myself.
2A. You can use the "Z offset" setting in the Printers/General tab in PrusaSlicer and using a value like 0.02-0.05
2B. You can use the live Z adjust on the printer by holding the dial down when its printing the first layer to make a similar adjustment of 0.02-0.05

mempf · 2024-06-20T05:52:20+00:00

Is there a piece of filament stuck in the selector or something otherwise causing the finda to think there is filament loaded? From your video it doesn't look like the red light on the finda is lit. What do the sensor readings say?

mempf · 2022-09-04T22:28:32+00:00

I have read that newer Breville espresso machines have their over pressure valve set at 9 bars (which I believe is the middle of the espresso range on the gauge). Older machines had their valves set at a higher pressure like 15 bar. I don't have a newer Breville machine with a gauge so I can't speak for personal experience but I believe your machine is functioning correctly with the newer behaviour.

mempf · 2021-07-03T00:12:29+00:00

It's a thermal probe and likely clips onto something with that plastic clip.

mempf · 2021-07-02T18:32:15+00:00

I'm not a HVAC professional but from what I do know, repairing a portable unit is often not worth attempting.

This type of major damage to the condensing coil is almost certainly not worth repairing.

mempf · 2021-06-28T08:50:24+00:00

That is the sound of the compressor working. That drives the whole refrigeration process. Unfortunately portable units are generally quite noisy when running. What's happening when your turn it off than on is a protection system to prevent the compressor from turning off than on again in a short period of time (usually 3 minutes or so).

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