Spool Rotator

Update: I've centralized most of the information in a new web site here:

https://3ddoodle.com/spool-rotator/


I like tricolor, co-extruded filaments. I have been working on a way to rotate the spool so the filament twists as it is fed into the extruder. It would make a spiral pattern if printed on a cylinder.

I could, of course, have used some kind of motor, but I wanted to use the energy from the spool's rotation to drive the twisting action. I didn't want to damage my extruder by putting too much twist into it, nor did I want it to have to work too hard to pull on filament.

I needed a mechanism that used very little energy. My energy “budget” was the amount of friction on a cardboard spool as it rotates on the plastic stand that came with my printer.

I use several 608 bearings, some 8mm and 4mm hardware, and pair of 8mm x 120mm threaded rods and some nuts. And a #64 rubber band, used as a belt.

Six 608zz bearings:
https://www.amazon.com/dp/B08YN6WQXR
Two 8x120m