A printed spur gear driven extruder for Mendel or Darwin.
Construction and testing details on the RepRap wiki here:
This is a new extruder design based on Adrian\'s geared nema 14 extruder, with some ideas from Nophead\'s extruders. During testing it produced over 16 kg of pulling force on the filament. Hot end development is still ongoing, but it should plug and play with any existing 16 mm thermal breaks.