Now, by just looking at this,

3D Printing
,
1

Now, by just looking at this, your first thought is probably going to be “wtf does this video have to do with 3D printing?”. I’ll tell you what.

This is the same thing that happens to our filament in the nozzles as it’s extruded. This is what makes simply combining filament so difficult. However, this also can also be utilized for some very pretty effects as seen in @Richard_Horne 's blog: http://richrap.blogspot.co.uk/2012/08/3-way-quick-fit-extruder-and-colour.html
http://www.youtube.com/watch?v=p08_KlTKP50

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That’s a very cool demo, I wonder how many revolutions it can still undo from.

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I imagine a theoretically infinite number, under ideal (non-existent) conditions. I imagine the biggest variable is the rotation speed. If that were more tightly controlled (more constant), I bet you could go much further with yet better results. Only speculation though.