weird filament clog makerbot 2

[jwheels1]

I went through a kilogram of material without a problem. today, the extruder seems to be collecting filament above the "traction" wheels.I done at least three hours of printing on this filament and then I've had just a headache after headache. Any suggestions about what I should do differently

[Alibert]

The traction wheels seem to be grinding into the filament (in any case, the filament is not moving into the throat), so the backpressure from the nozzle is too high to push the plastic through it.

Most likely problem is a clogged nozzle. Heat it up to 230C, remove it, clean it and put it back. Or simply replace it with a new one. It is wise to have a few spares handy anyway. They cost very little when ordered from china.

If that does not help, less likely is a problem with the temperature, that is the thermistor or the heater. Can you measure the temperature with a probe?

[jwheels1]

good suggestion
I have spare nozzles.
Is the Kamo 0.4mm Extruder Brass Nozzle correct? size