Filament melts and covers the small tube at the “Dual Extruder Filament Guide”
This causes the left blade holder to get stuck and as a result the extruder cannot switch heads.
This is a brand new printer with about 300h it happened already several times. I have replaced the “Dual Extruder Filament Guide” but it happened again. The filament is PA6-GF by SUNLU …
Also when I do a cold pull and get notification to pull out the cleaning filament I hear the servo ticking again and again. Like it is trying to extract the material ?
I reported this to Bambu and so far they have no idea. I was told that it can happen because I was using a 0.4mm nozzle and as pressure increases it can happen. The suggestion was to change to 0.6mm nozzle.
We have 3 H2D printers with over 1000h on the older ones. So far we have lots of hours printing time with 0.4 and numerous materials (PA, ASA and PPS all with CF) without issues so I do not think that the 0.4mm is causing it.Yes we have more blockage due to the fibers and print slower !!.
When printing a different model (same material) we had no problems. Printed about 15 pcs…
I started thinking that maybe it is related to the prime tower. The model that was printing OK was printed with only PA-GF, versus the model that caused the material creep had a prime tower. I used PC as interface material.
I think that when I triad to use two material (left head with PA-|GF, right head with PC) we had the material creep because of the way the prime tower is created. The extruder builds pressure in order to get a smooth printing and that what cause the material creep.
When printing a part without support there was only one material, no prime tower, no change in flow or pressure (continues printing) and worked fine. Once we had a prime tower and maybe several cloned item the print was interrupted. Also on every layer the extruder jumps to the prime tower and those we got interrupted printing, pressure build up etc… When the extruder print the prime tower it runs very slow, meaning we may get heat creep and it causes the problem.
One way to get better results may be slowing down the flow or maybe better handling of the prime tower but that is at Bambu settings.
Just a side note. As we did not have a profile for SUNLU PA6-GF I created a custom one based on Bambu own PA-GF. I reduced the flow to 9.5, raised the printing temperature to 275 and maybe reduced cooling, I need to check the profile.
See attached images.
Any ideas are welcomed 
