I have a Clicking Extruder, filament jumps back  

RE: I have a Clicking Extruder, filament jumps back

Try dialing speed back using the front knob when the clicking starts. If that stops it, you can try slower print speeds. Definitely be sure the extruder tension scree(s) are set properly. 

RE: I have a Clicking Extruder, filament jumps back

I think, I print slow (60mm/s) 0.4 Nozzle. The (one) screw's tension I also think is fine, there is no visible grinding. If tension is too low, there will be some grinding-marks in the filament. Is that correct? But, I will try to slow down speed.

For me, it looks like the stepper looses it's strength. He breaks down, looses steps and then it is a chainreaction, that the fillament popps back, then the stepper continues extruding and the force will be bigger and bigger then "explosion" and the circle begins...

And why after 6 to 8 hours? The amount of retractions in this section of the print increases. The slicer wants to fill many very tiny gaps. But this is the job of a 3D-printer ;o)

RE: I have a Clicking Extruder, filament jumps back

Sounds like you've covered the basic possible hardware issues. Yes, there would usually be some grinding on the filament if the tension screw is too loose.

Are you printing in an enclosure or unusually warm ambient temps? The E3D V6 hotend used on the Mk3 is rated to 40C ambient temps. Any higher and the air cooled efficiency drops off, leading to possible heat creep through the heatbreak and into the cold zone. This would explain why it takes time. Many people reported similar problems that were resolved by replacing the Prusa version of the E3D V6 heatbreak with an E3D version. The Prusa version has a slightly larger top bore, and a step from 2.2 to 2mm. Prusa doesn't think this is a problem, but many have found replacement to be a quick fix. Others have had good luck just applying some thermal paste at the top of the heatbreak (NOT the bottom) where it screws into the heatsink.

Other things to check:

• Ensure there is good airflow around the hotend and that the hotend cooling fan (Noctua) doesn't have a cover or other obstruction impeding airflow. If printing in an enclosure, open the door(s) -- particularly for filament with relatively low melt points like PLA.
• Be sure filament feed is free of snags and friction. One guy had issues and found his little filament dust filter was snagging.
• Extruder tension screw(s). You've done this.
• Check the filament feed through the top of the extruder down past the Bondtech gears into the PTFE tubing. Open extruder door and inspect PTFE tubing.
• Open sliced part in slicer preview and check for lots of retractions in problem areas. Try increasing Printer Settings->Extruder 1->Retraction->Minimum travel after retraction.
• If you're sure airflow is good, check the temp on your extruder motor. It can get hot, but should not be too hot to touch. If so, look for friction in the feed path.

Other thoughts: Have you made any hardware changes, added an enclosure or swapped nozzles recently?

RE: I have a Clicking Extruder, filament jumps back

@bobstro

Tanks for all this topics. Much work to check. About the heat creeping up over the heatbrek I have seen, I have also seen a video with this "lip" in the Hotend. Maybe I try to get a normal heatbreak ... I will reply, if something changed :o)    -   Carsten

RE: I have a Clicking Extruder, filament jumps back

I wasn't having the problem, but replaced my heatbreak with an E3D titanium version and it's working well!