The nozzle tip, which actually is a copper welding tip, is purchased at Princess Auto. It has a roughly 0.6mm (0.023") hole in the middle. It's about 6.1mm (3/16") in diameter and 2.4mm (1") long. It also has an M6 thread (6mm-long). Oh, and most importantly, it costs $5.99 for six of these.
The barrel is made with a half-inch think aluminum rod. There's nothing much to say about it, really.
I'm not certain about the heater barrier, tough; PTFE seems to bulge after prolonged use, and PEEK is hard to obtain (at least here in Ontario, Canada). Eric proposed using layers of Kapton tape; I don't know if it'll work out well, but I guess there's only one way to find out.
Well, that's our physical progress so far. There still is a long way to go to get our own 3D printer up and working, but it's pretty exciting to see tangible things coming together. Next time, I'll share some CAD drawings of the feeding mechanism.
Until next time,
Watrapter Project Co-Lead