Think (in faucet analogy) of the pressurized syringe time/pressure system as trying to control your kitchen faucet water flow all the way up at the water tower. This types of valves would make a nice addition to the previously discussed pressurized syringe systems by switching the on/off action to the nozzle side of your system instead of pushing the whole body of material. So it boils down again to two other 'controlling' parameters, time of opening and feed pressure and we know those two from the last episode. One can regulate these valves only with set screws which increase or decrease the diameter but this is a fixed setting, not something you control during operation.
They are all operated by air pressure and follow digital logic, open or closed. The Poppet and Spool valve seem the most suitable for high viscosity paste materials, even abrasive and filled pastes (what clay is). They differ in working principle and therefore are better suited for different applications. In this basic valve category we can find fine apparatuses like the Poppet, Needle, Diaphragm, Spool and Pinch Tube valve.
