Failed print- stange residue on hot end and extruder printing above heatbed

[paulrhee2002 2]

Finished a 3.5 hour print and started a 2nd print.  First layer was fine but when I came back to check on the print, the z axis was way above the bed and was printing into air.

There was no more filament coming out of the nozzle so there was not a huge stringy mess of filament even though it was printing in air.  I guess the filament stopped coming out and then the z axis changed.  

There was some weird residue all over the hot end and I attached some pics.  I just shut off the machine the instant I saw it was a failed print but forgot to check what the screen said before I shut it down.

It's a tevo black widow printer with stock parts except I changed to a 1mm nozzle.

Was printing flex filament at 220 degrees

Anyone have any idea what happened and where that residue is coming from?  

Thanks for any help!!

[watermeleon 0]

Hi paulrhee2002,

I have the same issue on my ender 3 printer, could you tell me what was wrong with yours or how you fixed it?

[GregValiant 1,344]

My guess is he had a blockage at a gap between the nozzle and the bottom end of the heat break.  With a 1mm nozzle he was pushing a lot of material so heat creep doesn't seem as likely but is still a possibility.

 

The black marks are filament and there may have been a bit of a leak of plastic past the nozzle threads (although that usually results in loose globs on the print).  As the extruding slowed and stopped then any oozing plastic could get blown around by the fans and the strings just ended up getting stuck to the heat block.

 

Take it apart and clean it up (careful of the wires and don't burn yourself).  Make sure the nozzle is seated against the bottom of the heat break (if you also have an all metal), or that the bowden tube has a nice square cut and is mashed against the back end of the nozzle when you tighten the nozzle.  The hot end should be near operating temperature when you tighten the nozzle.  Oh...and tighten the nozzle with a socket.  Only a hack would use pliers.