Endless Loop - Load Filament 1 fails despite sensors seeing the filament.  

RE: Endless Loop - Load Filament 1 fails despite sensors seeing the filament.

Is your Extruder jammed?

The final sensor is before the Extruder.

The last problem I had on the MMU2S was a small chip of filament in the Extruder preventing loading.  

Had a plugged nozzles several times, always a slightly different issue - but all Extruder blockages.

First one was a free a failed print (air print) the heat creep caused the filament to melt onto the PTFE tube.

Second one was not the PTFE tube, just two large chunks of broken plastic in the lead to the PTFE tube.  That was from using up old brittle filament.

Third and final one was similar. Didn’t actually find the plug when I disassembled the head - It seemed to be clean.  But there was a tiny chip of filament on the deck when I was finished. So I assume that was the culprit. It was definitely plugged before I dismantled the head. The MMU2S kept ramming and retracting the filament - to the point where the gears had damaged the filament.  I tossed that section.

RE: Endless Loop - Load Filament 1 fails despite sensors seeing the filament.

Hi Rob, 
the MMU2 can be quite finniky.... 

Please check filament over about 600mm, make sure there are no chunks chewed out by either the extruder bondtech gears or the MMU pulley hobbed gear. 
these thinner sections of filament can momentarily trigger either the finda, or the filament sensor. and cause lots of irritation. 

I have an LED on my filament sensor, and I noticed a similar incident, where the filament would feed to the filament sensor I would see the LED indicate that the sensor had triggered, and a moment later the LED would extinguish and re illuminate... the Printer saw this flicker as a filament failure. and cause a cycle of the feed function... 

to resolve this I cut off the length to the damaged section, and re inserted the filament, this time the filament fed properly. 

Might work for you.

joan

RE: Endless Loop - Load Filament 1 fails despite sensors seeing the filament.

Thanks, Joan.  I have about half a meter of 10cm snips where I've tried putting a pencil end, a flat end, make sure there are no ridges on the filament.  That wasn't the problem
However - I did manage to resume the print by performing an act of desperation.  I started taking the extruder apart without cancelling the print.  There was some black plastic string in the gear assembly area.  Of course, doing a visual inspection for black strings/dust when I'm printing with bright colors was not on my list of troubleshooting actions.  The black strings are odd, because there have been many (Several dozen, including 24+ hour jobs) successful prints in colors other than black since I last used it.  The MMU load filament process never failed until this timid attempt to do a single filament change.  I doubt the extruder itself is starting to fall apart.
Anyhow, I'm now happily printing again.
Is there any way to get an indication that your filament path is more contaminated than a Silicon Wafer Production Facility via sensors?  Otherwise, I'll have to add "Partial Disassembly of MMU and Extruder, Clean and reassemble" to the list of actions before a print.

RE: Endless Loop - Load Filament 1 fails despite sensors seeing the filament.

How do you clean your MMU2S gears?

I am doing something like:

1. a small brass wire brush,
2. open the idler to expose the filaments
3. Check the filaments and cut off any damaged lengths
4. Push the filaments to expose the gears.
5. Trigger a feed steps so the gears rotate perpetually
6. Brush the embedded plastic off the gears.
7. stop the feed.
8. Manually reload the filaments past the gears
9. Close the idler
10. Re-tension the idler.

turn on the 

Posted by: @joantabb

Hi Rob, 
the MMU2 can be quite finniky.... 

Please check filament over about 600mm, make sure there are no chunks chewed out by either the extruder bondtech gears or the MMU pulley hobbed gear. 
these thinner sections of filament can momentarily trigger either the finda, or the filament sensor. and cause lots of irritation. 

I have an LED on my filament sensor, and I noticed a similar incident, where the filament would feed to the filament sensor I would see the LED indicate that the sensor had triggered, and a moment later the LED would extinguish and re illuminate... the Printer saw this flicker as a filament failure. and cause a cycle of the feed function... 

to resolve this I cut off the length to the damaged section, and re inserted the filament, this time the filament fed properly. 

Might work for you.

joan

 

RE:

Not to be too pessimistic, but it may be a lost print.

On my first MMU2S print, a week ago, (the sheep - Baaa). I started getting jams after 50%.  I made it to 94% before the printer gave up.

What took me out was ‘bed adhesion’.  

Eventually the bed got cold.

The automatic release triggered.

So the wipe tower started to slide around !

If you continue to try to finish (the restart works impressively well!) consider if you need to glue the pieces to the board.

Posted by: @rob-w5

I have absolutely no idea what's going on here. I am sitting here with 43 minutes of a 5 hour print left, and I just need one more filament switch.

RE: Endless Loop - Load Filament 1 fails despite sensors seeing the filament.

It finished.  I'm trying a second one, with everything clean.  So far this time, it retracted the first filament and attempted to load that same filament in again.  I'm going to guess I have a sensor that blinks to OFF when it shouldn't.  I'm going to guess that I need to adjust the Filament Sensor to be less sensitive.  -- That it err on the side of being in a State of 1 instead of erring on being a state of 0.