Under extrusion,: material retracted from nozzle?

[dayta 0]

Hi all,

Hoping someone can help us troubleshoot our Ultimaker 2 Extended.

Most commonly during long prints, 20hrs + we have been experiencing a material extrusion problem.

Often it appears that the material has retracted from the nozzle and you can see the end of the material hovering in the Bowden tube. maybe 10-15mm from where it should be. This will happen 60-70% of the way through a print.

When I investigated I have found I can push the material through the feeder at the back so it was then coming through the nozzle, only to find that with reduced material flow the nozzle has become slightly blocked and needs to be cleared.

There is no evidence of grinding on the material from the feeder.

I'm was curious if it was a retraction problem but I tried different settings and had the same results.

Do you think there is maybe a problem with our material feeder? Has anyone had problems similar before?

Thanks for your help.

[Nicolinux 288]

Maybe the filament is odd and does not have a uniform diameter of 2.85mm.

[yellowshark 153]

Are you near the printer when it happens or in bed? You really need to be there so you can get some idea of what is going on, otherwise it becomes a bit like looking for a needle...

Is the filament sticking in the reel perhaps.

Can you post your speed/extruder temp/retraction settings. What makes it strange is that you are seeing no grinding on the filament. If the filament is meeting resistance then one would expect the drive wheel to cut into the filament and leave evidence!

Does the geometry change significantly where the problem occurs - a pic might help us.