Paste Extruder Stepper Motor Printing Head

This is a screw driven peristaltic Paste Extruder. It is still experimental, so before you decide to build it please check the following videos to see it in action:

- extruding polymer blend (hair gel):
http://www.youtube.com/watch?v=1XWYLSRCcq8

- extruding viscous chocolate glazing:
http://www.youtube.com/watch?v=qIFkw5RNXqQ

- extruding polymer blend at 16mm/sec, 0.5 mm nozzle, 250 micron layer:
http://www.youtube.com/watch?v=axAP0btw4Lk

Some pictures of the printing head: http