Please use this website for the latest and greatest information about the spool rotator: https://3ddoodle.com/spool-rotator/
The web site includes troubleshooting information, additional models for pulleys and much more.
The info below is for previous revisions and is no longer complete, because I can't add more models to the Spool Rotator record anymore. And, there is no way to incrementally import from elsewhere, so the Thangs record for the spool rotator is deprecated. I cannot maintain it here. All the files are on Printables here:
https://www.printables.com/model/523118-spool-rotator
Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:6114566.
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 8x120mm threaded rods (or longer): https://www.amazon.com/dp/B0BLGTH8K5 8mm hardware kit: https://www.amazon.com/dp/B0B4FPBP8D 47 6x2mm neodymium magnets: https://www.amazon.com/gp/product/B0C5M8QPQ1
There are "gears" but they use 6x2mm magnets instead of teeth. That way, if there is too much force building up they just slip instead of passing those forces back down the filament to the extruder. It works as a torque limiter. The failure mode is simply to not rotate: not damage the printer. Beware: do not use weak “refrigerator” magnets. The ones I recommended are fine.
I had some 608RS bearings sitting around with grease in them. They are for higher loads like a person on a skate. They had so much friction the bolts just slid over them and the bearings never turned. Do not get grease-filled bearings! But, you should use metal shielded bearings to prevent dust and debris from getting inside them. 608zz are perfect if they are good quality. These are skateboard and skate bearings (among other things) so you might even have some around. They must operate very smoothly with very low friction.
I tried a chain link to transfer rotational energy but it had too much friction. Gears are problematic because they also have friction and require precise alignment, and they can deliver way too much force, pushing any problems to other parts of the system.
Magnets require less precise alignment, and modeling detents to glue 6x2mm magnets is much easier than modeling gear teeth.
The parts are all designed to print without supports and any kind of filament should work except for a flexible one like TPU. For that to work some of the shapes you'd expect to be round have a pointy hat - that makes them print without sagging.
You'll need to hang this from something like a shelf over the top of your printer. The bolt hole should be roughly 10cm in front of the extruder's input hole when it is in the middle of the print bed. The filament should not bump into the upper frame of the printer or it could prevent it from rotating.
There should be at least 45cm over the top of the printer frame so that the length of the filament between the rotator and the extruder is not too short. The shorter it is, the more the stiffness of the filament will prevent the rotator from working consistently. I tried mine at about 35cm and one of my filaments didn't work very well because it was stiff enough to impede rotation and cause the mechanism to fall backward. That led to a repeating loop which didn't rotate the filament.
You can see it working here: https://youtu.be/Q3Z1XhZC2ro
Photos:
You can see the stripy Gridfinity vanity base with a lighter holder on it. The stripes are uniform on the top part except for a strip of black. One of the magnets from the pulley gear came out and it stalled there. I glued it back in without interrupting the print and it resumed its rotation.
The 1x1 vase mode bin really shows of how the filament rotator adds something special to even simple shapes.
One photo shows my magnetic outrigger, which helps psh the magnetic gears together to prevent slipping.
The last photo shows that you can remove the spool and leave the pulley gear with its rubber band still engaged.
Assembly All assembly details are now here:
https://3ddoodle.com/assembly/
Tube-type Filament Guide You should really print and use a tube-type filament guide and position it right under the center of the spool.
https://www.printables.com/model/535748-mk3-adjustable-tube-filament-guide
Pulleys:
You can use different sized pulleys to cause the spool to twist the filament faster or slower. There is a limit to how much the filament can be twisted, and using a larger pulley will not change that. The torque is limited by the magnetic gears.
But you can use pulleys of different sizes to bring it up to the maximum or down below it. Generally a vase print cycles between the colors slower than a print with infill. You might find the smallest wheel is best for anything large.
You only need one pulley - all the others and the pulley base are optional. I use the one called SpoolPulleyFlange.
The smallest two pulleys are printed with their own flange. The others fit onto a flange base that accepts ⅔ of a bearing. About ⅓ of the bearing stands above and engages with any of the various pulleys. All the larger pulleys simply fit onto the bearing with some friction. No glue is needed. The flange and the pulley are both stuck on the same bearing exterior and they don't slip. It lets you print a single flange base and use it with any of the different sized