I built a prototype of the clay syringe pump some time ago, and yesterday was printing with this. Volumetric feeding is something excellent. Stable and accurate with no worries about safety and extrusion speed. But requires some initial test printing (2-10 g of clay) to reach "working pressure" in the pump. Here is the setup.
More images and discussion see here: https://plus.google.com/u/0/communities/103324258900608601175
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