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Gezz
 Gezz
(@gezz)
Active Member
Nozzle cleaning fail

The continued Core One nozzle clean fail with PETG filament, after a couple of prints normal is a fail - manual nozzle clean and restart print - very frustrating. My MK3S+ - MK3.5 I press print and feel confident of a trouble free print.

With my Core One (factory assembled) can I not press print and feel confident about the result - don't get me wrong, I am blind to all other printer brands - this has to be fixed by Prusa.

The alternative is reputation damage to the Core One

Posted : 10/06/2025 2:25 am
Koen Kooi
(@koen-kooi)
Trusted Member
RE: Nozzle cleaning fail

Which firmware are you running?

Posted : 10/06/2025 7:00 am
Gezz
 Gezz
(@gezz)
Active Member
Topic starter answered:
RE: Nozzle cleaning fail

Hi.

firmware 6.3.3

Posted : 10/06/2025 7:37 am
Raaz
 Raaz
(@raaz-2)
Reputable Member
RE:

My current idea about this:

Search for Custom Start G-Code, that disables the hotend heating during probing. Apparently, the heater is interfering with the loadcell and the "Nozzle Cleaning" G-Code command is simply to probe a little area at the front, not fancy G-Code that "cleans". 

When I disable the heating during Homing, then heating back up, disable for the Nozzle Cleaning, heating back up and then again disable heating during the real print bed probing:

Short Homing, no Nozzle cleaning fails, probing every point just a single time.

I guess PETG Nozzle Cleaning fails more often due to the hotend having to spend more energy for the higher temperature. 

Sadly, the mesh bed leveling suffers a tiny bit, due to the nozzle becoming a bit shorter, when dropping in temperature. But I didn't encounter issues or an ugly first layer yet.

Hopefully Prusa can implement something in the Firmware that disables the heating only for the Z-Moves during probing commands, so the hotend stays at its temperature. 

Posted : 10/06/2025 11:06 am
boomboom21
(@boomboom21)
Active Member
RE: Nozzle cleaning fail

Support told me it's a known bug and a fix is coming. Workaround was some custom g-code. See attached screenshot.

Posted : 11/06/2025 12:14 am
1 people liked
Gezz
 Gezz
(@gezz)
Active Member
Topic starter answered:
RE: Nozzle cleaning fail

Thanks for the feedback - great to hear Prusa is on it. I will try the GCode fix in the interim

Posted : 11/06/2025 12:32 am
boB
 boB
(@bob-3)
Active Member
RE: Nozzle cleaning fail

I stick a small strip of thin tape (FrogTape Yellow) in the nozzle cleaning area, the failures have been rare since then.

Posted : 11/06/2025 2:01 pm
Throttlebottom
(@throttlebottom)
Active Member
RE: Nozzle cleaning fail

Interesting.  I recently raised a support issue about failed nozzle cleaning as well as failed bed probing.  While they did supply code without the heating during nozzle cleaning (but did not explain at all what they were doing), they also did send a new load cell and main cable.  With some help on the forum I figured out how to disable heating during probing/cleaning, and have been able to print in the meantime.

I also noticed that my load cell values changed a LOT between finger taps.  I mean at first it's somewhere around 800 or so, and a tap brings it down to -100 or so, but then a minute later we have a single digit baseline and it goes way negative.   This is not normal behavior for a load cell.  But it's also concerning to me that disabling heating would impact anything for anyone.  I have personally assembled from bare strain gauges literally thousands of load cells, wired and calibrated them.  If heating is impacting the load cell signal someone did not do their hardware homework designing this part. These things are a tiny signal, and massively susceptible to noise, not planning for this is pretty bad.  I would imagine that the only software fix possible would be a more advanced turn off heater only during the actual touch move.   But if it is influenced to that degree it is straight up a bad design.  

Have not yet changed out the cable and load cell on mine, but the disabling heaters does work at least for the moment.   

 

Posted by: @boomboom21

Support told me it's a known bug and a fix is coming. Workaround was some custom g-code. See attached screenshot.

 

Posted : 12/06/2025 1:01 am
Gezz
 Gezz
(@gezz)
Active Member
Topic starter answered:
RE: Nozzle cleaning fail

GCode file  change certainly improves reliability ....... 

 

Posted : 12/06/2025 2:03 am
boomboom21
(@boomboom21)
Active Member
RE: Nozzle cleaning fail

I thought the gcode "fix" was working but still having issues. Support says they're still working on a firmware fix. Oddly, it seems to happen more with my textured sheet than the others. Could be coincidence.

Posted : 21/06/2025 1:51 pm
Gezz
 Gezz
(@gezz)
Active Member
Topic starter answered:
Nozzle cleaning fail

I use the GCode fix when printing PETG (usually on the textured sheet) resulting in less fails - not perfect but a noticeable improvement.  I expect results may vary as no two machines will not be exactly  the same -  variations like machine tuning, filament brands, nozzle  etc may play a part.......

Posted : 21/06/2025 3:41 pm
Chocki
(@chocki)
Noble Member
RE:

Check and adjust your heated bed leveling. The core one doesn't have a perfectly level bed after a Z homing but relies on mesh bed leveling compensation to get a flat print, you can see the Z axis screws turning as the print head moves across the bed.

Use a piece of card (business card is ideal) and with the power off, adjust each Z axis screws to get the same drag on the card between nozzle and print sheet, just keep going round the three positions moving the print head close to each screw and testing the friction between nozzle and card until you get the same for the three points.

Turn power back on and home the printer. Note: Not Z homing.

It will retain this until such time as the print bed drives down against the stops and you will find that nozzle cleaning is now reliable. If it Z homes, then repeat the manual leveling.

This post was modified 2 months ago 3 times by Chocki

Normal people believe that if it is not broke, do not fix it. Engineers believe that if it is not broke, it does not have enough features yet.

Posted : 22/06/2025 11:07 am
Raaz
 Raaz
(@raaz-2)
Reputable Member
RE: Nozzle cleaning fail

Turn power back on and home the printer. Note: Not Z homing.

*calibration.

Z-homing happens at every start of a print, when the bed moves against the nozzle. Calibration is when the bed is moved against the bottom with a lot of noise.

Not meant as being a smarta**, I just confused the two things myself so want to clarify. 

If you want to permanently fix this, there are mods for the bottom of the Core One to level the bed during Z-calibration. Not sure that's time well spent, but there are nice dust/filament-pieces cover combinations. 

Posted : 22/06/2025 12:33 pm
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