The problem with the old prototype was the nozzle would drip heaps. Pumps now run backwards for a bit when they're done to suck liquid back up the nozzle - stole this idea from 3D printing.
@IVData So like the retract setting on a 3D printer? Cool. Does it make it harder to dispense an accurate amount since you might pull air into the system when it's reversing?
@jmwright exactly. It works pretty well. The tubes go 'downhill' once theyre behind the wall of the machine. I only retract just enough that the liquid would have to go uphill to leak out - so likewise the air would have to travel down into the liquid to mess things up.
It just occurred to me that smaller tubing for the air pumps might mean air cant leak in to let it drip (rely on surface tension).
@IVData Is the dispenser nozzle set up in a way that wouldn't result in cross contamination with this retraction? Also, is there a viscosity limit for what they can pump?
@sexybenfranklin thanks man. Silicone tubes actually run all the way to the tip of the 'nozzle' so there's no contamination. And they pump at least a thick syrup (though at about half the speed of water).
Makerdon is a Mastodon instance focused on Makers, Open Source Hardware (OSHW) and STEM/STEAM. Free and Open Source Software (FOSS) is a likely topic as well. If you're interested in making things, allowing others to build on your work, and/or teaching others about making things, you might like this instance.