Tom seems to like this: http://toms3d.org/2016/09/06/why-dual-extrusion-matters-first-look-at-the-prometheus-system/
I have to admit, I had the exact same thought. The only "custom" part which may be difficult to source is the peek connection tube. Tom suggested that this was important to remove the swollen end from the retracted filament. So.....is anyone going to try and make one?
So, it looks like you can buy 1/8" OD Peek tubing with either a 1.59 or 2mm id. If the purpose of this tube is to remove the swollen end from the filament, I'm guessing the 2mm OD might be too slack. Might need the 1.59 and open it out to maybe 1.85mm. 4mm OD would have obviously been better as it would then just worked with the standard push fit couplings. I agree the guide where the two filaments come together should be quite easy to print. I think I might look at having a play with this.
I already did a little research and found the Keton HPV PEEK as rods which are machinable. Also not so expensive... 300mm diameter 6 or 8 about 30-40€. I think I am going to go and revive some old contacts. Then I can have it "precisionly machined" (quote from the KS campaign) to fit in a V6 heat sink perfectly and on the other end to fit such a collect. 30cm should be goo for at least three of those parts. Or maybe i am going to make it for the UM2. I can easily add a second extruder and motor and it is already just a Bowden system...
When I saw this I thought why use bowden entirely? You could have a direct setup and use the force there force pulling, then have less beefy motors pull back the filament for the change. Should do nicely.
I'm more excited about using worm gear extruders like the flex3drive personally. The prometheus system will add a lot of print time with lengthy retracts. Especially if you're also doing multi-material prints with different temperature points. Although dual nozzles have there problems, ultimately it is the best system if well calibrated.
It looks like the E3D v6 hot end will work. Anyone backing the kickstarter campaign? With or without the Prometheus hot end kit?
I supported it from day one. Without the hotend from them though. An idea I have is to use it for the second hotend, to have additional material used with this and it can pull those out of the hot zone when not in use. That would be great for those water soluble materials that don't like being cooked.
Currently I am backing with hotend but I am still thinking. Multi material is interesting. But for printing support it may not be the ultimate solution because if the different temps you need for example the recommended combination Edge and Scaffold...
When doing materials of similar temperature I think the Diamond hotend makes the most sense (particularly on Repetier with color mixing and RGB filament). For different temperature materials I think the E3D Chimera looks the easiest to level - not that I have one, but I kind of wish they had sent those out in the dual pack rather than two V6s.
If you can send commands to change the filament, you could also get the system to change temperatures, though it would cost more time again. What I would find interesting is simply the "auto loading" so I'd still use two nozzles but have this on the second one so it would retract material as to not cook it in the hotend while the main material was used. Scaffolding comes to mind there.