Very large prints fail due to filament clogging

[UrsLoher 2]

I have made several attempts to print some really large parts on my Ultimaker 3. I tired it in PETG, PLA and ASA and I always see the same problem. The parts are really very big and printing time is more than 2 days. Shortly before finishing the print I get clogging of the filament and end up with an unfinished print. When I restart the print without doing any maintenance other than re-feed the filament, then everything works fine again. The print head is still free and doesn't need any maintenance. Also, the print quality of the stub is simply perfect. After such a failure the filament shows a grinded section and it is obvious that somewhere between the feeder and the print head it somehow clogged. I can't figure out where the problem comes from. It happens with brand new filament and with old filament as well. I have changed the print head but still have the same problem. Small prints with printing time below 1 day always work perfectly with the same settings.

The only work around at the moment is to split the parts into several sub-parts and the glue them together afterwards. This is not very efficient and accurate though. I'd appreciate any hint to resolve this (expensive) problem. Thanks in advance.

[GregValiant 1,409]

Put a "Pause at Height" (or two) in the Gcode file.  Make the pauses below where you would anticipate the clog.  It's a stupid workaround but it would allow the model to finish.  I have been working on this same problem on my Creality machine for 2 weeks and haven't come up with a solution yet.

[UlrichC-DE 115]

Hello

 

I guess.

 

(Possible cause but not the problem)
Enviroment. The printer is close to a wall. Or is at home. The filament warms up over time and becomes soft.

 

(Probably not possible here)
The feeder is squeezing the material too much.

 

(Most likely)
The PTFE coupler on the nozzle is worn out. The diameter is enlarged. A plug forms when the head warms up. [Edit: You often only notice this when the Enviroment of the printer and filament are warmer. Cooling with the fan behind the print head is then no longer sufficient.]

 

 

Best wishes
Christian

Edited July 4, 2020 by UlrichC-DE

[Torgeir 280]

Hi UrsLoher,

 

Welcome in here.

First, I do not have an UM3, but with all the thing you've done to in order correct this -it's sure kind of strange..

I'm just wonder could this grinding of the filament occur due to high number of retraction? As there's some load on the feeder and in combination of a little lo pressure setting at your feeder.

It might be one of these two issues or the two in combination that can grind down the filament, then the feeder wheel start spinning but cannot move the filament anymore. (I'll think this have happen before.)

 

Just a thought, because of the fact your printer do not need any maintenance after this fail..

 

Good Luck

Regards

Torgeir

 

 

Edited July 4, 2020 by Torgeir
More info.

[UlrichC-DE 115]

That's right, it's a UM3. I had left that up. So it cannot be the PTFE coupler. Would be too easy.

Then it can be the other two points.

[UlrichC-DE 115]

looks like this

[UlrichC-DE 115]

I disassembled a UM3 Printcore today. Other problems and ideas. But. There is also a PTFE tube in there. So in that case I would also try a different printhead.