The experiment did not go as I had hoped.
Although the substrate mix is good – a good sand / starch / soil balance – it was too dense to be pushed from the large tube into the small tube, resistance forces overwhelmed the pumping action.
Some substrate was squeezed from the storage cylinder into the rubber tube and I was able to test my new idea of using a network of rubber tubes. The substrate squeezed easily from the rubber tube.
I will be building it manually if the device cannot keep up. One ring every day. My idea is to do this by filling the rubber tubes, and squeezing it out from these. I can fill and empty the tubes manually, but via this process I will be able to develop the tube squeezers, and also the print head – because both are developable even though the rest of the process is manual.
Basically the idea is to create a motorised tube squeezing process. I can fit a metal tube key to a motor and wifi arduino and control what color is used from a central processor.
Pictures show state of device tested on 14 April 2013.