I suddenly had a very poor result while performing a high precision offset calibration, I had underextrusion, bad layer adhesion etc things that never happened before.
The only thing I did before this was trying the 0.2 nozzles and this happened after I switched back to 0.4 nozzles.
I redid the calibration and the only strange thing was some creaking sound during the flow calibration of the process that I had not noticed before, calibration failed again with same results.
I checked nozzles, try other filaments, different AMS, remove the back splitter thinking the sound was coming from there, same results. At my 5th or 6th attempt, I finally had a fault message for an extrusion issue.
I then decided to dismantled the hotend and check everything. Apart from some filament residues that were not in contact with anything which would have caused an issue, I checked the gear remembering one of the user that had experienced slippage between gear and extrusion wheel and voila!
I did not exactly find it like that but although the extrusion wheel was still on the shaft it was a little tight but not tight enough that it couldn’t slip relative to the gear. That was the creaking noise I experienced when there was micro slippage between gear and wheel.
I suppose it was OK until I used the 0.2 nozzles which may have required higher pressure which exacerbated a certainly existing condition.
If you hear strange creaking noise during auto flow calibration or you have bad adhesion, underextrusion, bad surface quality, missing layers in your print, check your gear!
Edit: I opened a support ticket but in the meantime I just put a drop of superglue on the shaft, my prints are perfect again
Seems like a bad design to me, these two parts should be “pressed” together. While they may have been press fit originally, it’s obvious that the tolerances of the fit was too loose. Loctite 603 would be a great choice to really lock them together again if the CA fails.
Thanks for the heads up, I haven’t experienced it yet. I do have a couple of .20 nozzles that I intend to put to use so I’m going to pay close attention when I change over to them.
Isn’t it too soon for such things to fail? And people call me crazy for freaking over the belts grinding themselves to dust while almost derailing from the rollers.
It was a poor design. I called it out a while back and guessed that it would be an issue once people got more hours on them. My laser edition is still down because of it. Ill probably just order a new toolhead and use some permanent loctite. After a couple back and forths with support, I remembered why I hated bambu support. Its a pressure fitted part in a machine that constantly heat cycles. Pretty obvious this would be an issue over time. As the part starts to slide off, it pinches the filament in its path. Probably what causes extruder issues for people in this forum. They just havnt realized yet.
@LarryCnAZ has the right idea. CA glue weakens when heated
I had some misses on my prints that I put on glitches or slicing issues, when I re-sliced and reprinted they were then perfect but I wonder now if it was not it. You may not even notice the gear loosens until it develops enough to become obvious. I think the pressure advance calibration put more pressure on the gears than regular printing flow and if you don’t use it or only once in a while because you calibrated your filaments or always use the same it might just go unoticed.
The thing is if you include dynamic flow cal in your print and there’s micro slippage of the wheel, PA will be way off and you get under or over extrusion. If I knew firsthand I would have tested with and without PA cal before I fixed the gear.
I’m the second user on this board to experience it as far as I know but I wonder if it’s not a wider issue given the poor printing some experienced, it might be more common.
If it is (not reported on the board but with @supportassistant) bambu will come up with a better design or advise the manufacturer to improve the press fit.
Looking at this thread, it looks like 4 or 5 users have already had the same issue and on at least 2 occasions, support asked about it, might be more widespread than just a couple of users…
At least if there is an issue with manufacturing, it’s an easy fix in the long term, they just release a better version to either buy or warranty replace. I’m not to worried overall.
