I had not come across these designs before.

3D Printing
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1

I had not come across these designs before. I think this is a great way of printing more than two colors/types of filament. I’m not a big fan of the palette in the first link since traditional mounting of multiple nozzles is much more efficient with a software offset.

http://nutbits.blogspot.gr/2013/07/multiple-cam-driven-bowden-extruder-and-the-palette.html#

2

Maybe combining this with the dual carriages in the post ( https://plus.google.com/112051255530119405833/posts/b7sxowghtaY ) would be great. Or traditional hot end mounting with good retraction and a wiper would be ideal. The Stratasys Dimension I used in the past printed with two nozzles on one carriage but wiped whenever the material was switched.