I was thinking about this kickstarter project where they print circuit boards, and later they show it printing solder paste. I've seen other liquid or paste dispensing systems like this too, maybe for medical or chemical uses.
My question is how do you make a system that dispenses a known amount of paste like that? I get that I can run a motor and put pressure on top of a syringe and goo will come out of it. Maybe a stepper with some gearing?
Is there a feedback mechanism? It seems too small to have some kind of flow meter there. Are these kinds of things just open loop and you calculate the volumes ahead of time and just crank down the motor accordingly?
You must have to get it to some baseline first though, like a home position where paste is at the bottom of the nozzle.
Just curious how these things work.