Load to extruder failed #04108 (MMU)

What happened?

While loading to the extruder, as soon as the filament sensor detects a filament the printer performs an automatic loading check. If the check fails, this error is shown. Each failed load might be accompanied by the printer beeping.

The printer’s automatic loading check loads approximately 40mm of filament and then unloads 30mm of it. If the filament sensor stops detecting a filament at any time during the process, the error is shown. This process is very sensitive, so making a precise Filament sensor calibration is needed in order to prevent print defects.

While your MK3S+ is performing the loading check, solid blocks should be generated on the bottom of the LCD representing the IR filament sensor detecting a filament during the process.

If there is a line instead of any blocks (drop in the sensor’s reading), this means that the sensor stopped detecting filament at that moment, resulting in a failed loading check. The printer then retries the load. If the cut function is enabled, the MMU tries to cut a filament tip. If the drop while loading persists even during the retries, the printer unloads the filament and shows the error.

How to fix it?

Redo the IR filament sensor calibration (MMU3, MMU2S).
While the printer is Idle, you can use the Loading test in LCD menu -> Settings -> Loading Test to verify the filament is able to load properly.
Undo the PTFE tube from the FESTO fitting and pull the filament out by hand to inspect it. The last 40cm (15") of each should have no dents in it, or the gears won't be able to grab the filament. Cut off part of the filament with defects such as indentation or a deformed tip. Make sure the filament end is straight and has a sharp tip at the end. Reattach the PTFE tube and hit Retry.

Inspect the extruder to rule out a hardware fault such as misaligned Bondtech gears or Extruder Idler shaft not inserted correctly.
In case the issue continues to happen over multiple unloads, check the extruder for clogging.
Inspect the filament spool and the buffer for excessive friction or filament jam. Make sure the filament is able to move freely.
Use only high-quality filaments. Certain poor-quality filaments or very specific types of material might not work correctly with the MMU.

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5 comments

ChrisL

•

I received this error on a MK4S with MMU3 today. Nearly everything on this guide including the suggestions for how to fix the error are written for a MK3S+. I suggest that updated guidance be produced for MK4S (and CORE One if the fault is still used on that model whenever MMU support is released).

annswims

•

I was getting an inconsistent set of lines and boxes with this message
None of of the above things fixed it for me. What did work was adjusting yhe axel on the idler door. https://forum.prusa3d.com/forum/postid/608180/

David B.

•

Hi! Thanks for sharing. A similar case has been reported before. A note about this has been added to the article.

Fabian

•

Really sad to say, but I just should have bought the Bamboo combo on Black Friday instead of the MMU3 update.
I've got the feeling, that Prusa stopped quality control for the old printers and delivers just a mess with the new firmwares. My printer runned without issues, until I've updated to the newest firmware and installed MMU3. Now I've got such issues with the MMU.
Sorry, but I'm really frustrated, how bad also the new MMU3 works compared to the AMS, this feels like making fire with sticks and stones in the rain, while looking to the sky and seeing Bamboo building a space station.
Why riding on a dead horse and even try to improve it? Porsche did it great with the car layout and the engine in the back, but maybe Prusa needs to accept, that they are not Porsche.

beyond3dprints

•

I feel your pain. I've been struggling with the MMU2 for quite some time and the MMU3 probably suffers from the same things. What started to work was adding more cooling moves in the slicer. This drastically reduced the filament stuck errors I kept getting. The voltage issue is another issue that requires a mod for the MMU2. I hope they fixed that w the 3.

dave2007

•

i will be moving to bamboo labs on my next purchase, always used Prusa but they are getting left behind i think

OldGuyAdventure

•

Yah, I was hoping to make some money with the MMU3 and my MK3S+ and then buy a Bambu Lab printer with an AMS. But it is looking kind of bleak. Unless I can get the system to run reliably, I might be saving for a Bambu yet. I think Prusa has lost sight of their customer base.

KonstisSFX

•

After the first printing attempts with the MMU3, I have the assumption that the chimney will shift slightly due to the vibrations if it is not attached well. As a result, the sensor is no longer triggered.

OB1

•

Typo:
The last 40cm (15")
Should say 1.5", instead of 15".

David B.

•

The number is correct. Examine a 15" section of the filament for any indents. If there are indents along the filament length between the MMU and the extruder, the MMU pulley might face difficulties in moving it.