I’ve been getting this sound with my printer lately.
I’ve narrowed it down to the retraction motion. If I change my retraction speed in slicer from 30 mm/s to 20 mm/s I do not hear this sound and get much nicer prints – although they take a lot longer & are bit more blobby. I find a retraction speed of25 works well, but I still hear the sound from time to time.
I’ve experimented with various retraction lengths (when retraction speed is still at 30) and get the same sound.
I’ve experimented will various tension screw distances and also cleaned the hobbolt.
http://www.youtube.com/watch?v=2h9hrUHDYOg - see time points: 0:00,0:05, 0:012-0:15,0:27
hot end: 230
slicer - fast profile on lulzbot website
ABS (I’ve tried 2 different colors with the same result)
This is typical for any model i print. Obviously more so with models that require more retration.