Filament not feeding but just moves up and down

I'm trying to print with my Makerbot Replicator 2. This issue has started happening just in the last 2/3 days. I have a problem where the filament isn't coming out of the extruder. It happens when the printer starts with the infill. The first 2 layers are usually fine.

I really started to notice the problem when I put a little mark on the filament to see if it was being pulled into the extruder. Here's what I saw

https://www.dropbox.com/s/no9jk61kqr...45823.mp4?dl=0

The filament isn't going in, but every now and then it's pulled back up into the extruder. I know this retraction is normal when the head moves when it doesn't need to print. But why isn't it pushing filament through?


Steps I've already tried:
1. I've checked to make sure the extruder isn't clogged
2. I slowed down the print speed by half
3. I've increased the extruder temp by 5 degrees

No changes.

Are you printing at a larger layer height? Be aware that the print speed is limited by the number of CUBIC mm per second (mm3/s) of filament you are pushing through the nozzle. If you increase the layer height from say 0.15 to 0.30 mm, you are effectively pushing twice the volumetric amount of plastic per second at the same 'printing speed' (expressed in mm/s). A very good post explaining this can be found here: http://www.extrudable.me/2013/04/18/...ty-and-limits/

When doing an infill, in most slicer profiles the extruder is putting out more plastic at higher speeds (expressed in cubic mm per second, not mm/s), than for example the perimeters or bottom layers. What you describe seems to point at too much volumetric extrusion for the infill (more than your extruder can handle for that filament/nozzle_ID/temperature combo).

You still may be printing too fast and/or at too low temperature, or have done so and the point where the filament is pinched in the extruder has ground away. The effect of the latter is that the extruder cannot put enough torque on the filament to push it through the nozzle as the filament is thinner because of the grinding.

Another possibility is that the grooves of the extruder wheel have clogged with bits of plastic dust.

Try unloading the filament (help and pull it by hand if necessary) and check it. If you see a ground-away section cut it off and reload the filament.

If that doesn't help you may need to clean the extruder wheel. Remove the fan from the extruder and check it for debris/dust/clogged material. Clean and re-assemble.

I checked the drive wheel. It's free of any debris or plastic.

The thing that makes me unsure what's happening is that if I pause the print while it's failing (i.e. not extruding like i described) and then immediately navigate to "load filament" it starts flowing just fine. So this must mean that the nozzle is not clogged and the filament isn't grinding, right?

That is weird.

What slicer settings are you using?

I started with the Makerbot Desktop "standard" setting and then bumped the speeds down to 50 mm/s

Proof that the drive wheel isn't cloggedAttachment 8333