Replicator Extruders not Extruding

[Busybotz]

I cancelled a large print mid way, using the keypad, because it was curling. Then I cleaned the platform and selected a different file from the SD card, one which I had printed successfully several times before. Same card, same file.

Everything worked properly, except the extruder would not produce filament. I watched a few ghost layers being produced, then cancelled and tried it again with the same results. I then turned off the Replicator, and removed power to the power supply. I waited a minute and then tried again, with the same results. I cancelled that print, and ran the script to load filament on both sides, and they did feed. Then I tried printing again from the SD card, and it is now working properly.

What would cause this to happen? I have perhaps 15 prints on this Replicator, and this is my first Makerbot, so I'm not sure what to expect.

[Shawn]

Every once in a while, I'll catch the extruders not extruding. I
usually just pop up the black tube at the top of the motors to expose
the filament, then apply some gentle pressure down (as if I were loading
it again). It starts extruding almost right away.

I *think* the filament may have just warmed up enough that the motor
isn't being effective and needs a little help. But I don't have any
emperical evidence of this yet. For now my prints are small enough that
starting over isn't a problem.

[Busybotz]

Thanks, I can see how that might happen. I'm not going to worry about it unless it happens too often.

[66tbird]

I just had one quit a few hours into a long print. Total print time on the extruder is 3.5hrs. I heated and pulled out the filament and reloaded but only by force. The stepper is not grabbing the line nor do I feel the stepper run like I can on the other . So its time go to MBI I guess and get the testing procedures to track the issue.

[66tbird]

Update:  I pulled the extruder from the set screw on the drive wheel had backed out. I reset it with blue loctite and it now works fine. There was no witness mark from the set screw on the shaft flat so I'll check them all. Use blue loc-tite only and let it do its job, meaning don't crank down on those set screw or the many strip. That's decades of rc heli experience there, trust me.

[Busybotz]

I have yet to disassemble an extruder, but I hear you on the loc-tite. I fly RC helis as well, and would not feel safe without thread locker.

My bot has at least 8 hours on it since my first post, and the problem has not resurfaced. It is cranking through two sets of the Lightcycle kit by cbabbage: http://www.thingiverse.com/thing:22858 . 

 I am having a blast learning how the Replicator works, my bot has quite a personality! It (she?) might need a name.

[66tbird]

  I needed to pull the extruder off again with the same issue 6 hrs into a new build.and noticed the drive wheel again loose. This time there was a witness mark on the shaft from the earlier setup. It was off the flat because the flat did not extend deep enough down on the shaft for the drive wheel and parts to line up spot on. It was off by a mm. A gentle touch with a Dremal and it is correct now.  I'm figuring a fluke of stepper production because this problem would be quite numerous if not.