(EDIT: pressed publish too early and couldn’t edit to finish the descriptio of my problem.)
I’m trying to fix a Makerbot rep2 with 2000 hours on it but I have never come across something like this before. It seems to be extruding filament in a semi-regular pattern, by which I mean it extrudes for about 10seconds and then doesn’t for a few seconds before extruding, but not an exact repitition. You can see the effect in the picture below, this creates a textured pattern which is interesting but now how it is supposed to be. This can also be seen in the beginning of the raft as it extrudes and then pauses extrusion but keeps moving. I have verified this by loading filament and watching the back of the shaft of the extruder motor pause and then resume.
Is the stepper dying? My understanding of steppers is they work or don’t work, not that they stagger on. Or is this something completely different?
I have also tried several different rolls of filament from different manufacturers and checked for consistency in diameter.
Have you taken apart the extruder and taken a look at the knurled feed wheel? It can get clogged with filament dust and prevent “grabbing” the filament. An old toothbrush and some isopropyl alcohol can sort that out quickly.
I also check the diameter of the filament, just cut a length off say a meter and check the dia along its length, if you cant measure it, then run fingers along and see if there are any small bumps. Make sure build plate flat and compley clean. Also, just run extruder like feeding new filament, see if it extrudes fine.
I also never have seen something like this. Did you ever changed extruders and hot ends? May be some kind of intermitent clogging until pressure inside hotend becomes enough to unclog.
Obviously the problem is your feed system. Either the toothed gear is stripped in parts and needs to be replaced, the motor isn’t connected well, or there’s something wrong with the stepper motor on the feed system. The feed system is fairly simple, so there’s not much to check.
