Hello,
I have a reprap mendel with sprinter firmware + pronterface + slic3r and stepsticks for driving nema 17 motors and I have experienced couple of issues with my extruder.
First of all, I am using 0.3 mm nozzle and 3 mm kawasaki green filament, what I have experienced is that the temperature I need to use to make the filament come out from nozzle easily is about 270 degrees I would go higher but I don't know if it's a good idea because the filament colour fades , at the default 230 the filament goes veeeeeery slow and does not stick well to heatbed , After tweaking temperature to 270 it's way much better, I could run the printer at maximum 12mm/s print speed and 12mm/s extruder retraction speed with 0.25mm z layer otherwise the printer leaves small blobs every few mm so I guess that the filament was not hot enough, also the extruder was trying to push more filament inside the hot end but then the filament were ripped by the hobbed bolt and I always had to remove it, cut it and stick inside again.
The other issue I have with the extruder is that the motor tends to overheat after about an hour then what happens is that the motors starts to skip steps, and the filament stops to move forward, I don't know if this happens to other people but I started to think about mounting a fan and a radiator on the motor to cool it down.
Thanks for your replies!