This is an evolution of the Claystruder 1.1 for Rapman.
Simpler, more modular. It does not yet feature a mount for a solenoid valve, maybe I add that in the future.
I made some improvements to the system since the Claystruder 1.1 version I posted on Thingiverse. The main one being the decoupling of the nozzle (a polyprop tapered tip) and the syringe. This simple change solves some issues with swapping syringes on long prints. If you have the nozzle attached to the syringe directly, like on the Frostruder, each time you want to swap a syringe you also remove and refit the nozzle with it and its very hard to get that syringe+nozzle back in the exact same spot again. Your nozzle is also never straight so even a slight rotation can put it a millimeter off. So if you continue your print (on Rapman its fairly easy top pause and restart a print) it will continue in a different spot. The solution is easy, make sure your nozzle stays in its place on the print head carriage when you remove the syringe. I use a small luer-lock male-female extension bit (http://www.dosieren.de/en/shop/products/cat/luer-lock-adapters/pr/luer-lock-special-model.html) that is glued in the printhead (a simple mount). The nozzle is fixed to one end and the syringe screws in the back. This feature should be part of any paste extruder that uses syringes since it solves a lot of trouble with multi-syringe prints. There is also a set of windows in the barrel holder that allow you to guard the level better.
For this extruder I also designed a syringe adapter head that can be easily twisted on syringes and can withstand (depending on print quality) pressure up to 6 bar by adding bolts and washers as reinforcement. This file can be found on thingiverse here: http://www.thingiverse.com/thing:21074
This info was also posted at Unfold~fab: http://unfoldfab.blogspot.com/2012/04/road-to-better-paste-extrusion-episode.html