Screwless Cube Gears
by emmett, published
UPDATE: For anyone without access to a 3D printer, you can now buy these from caesia on her Etsy store: etsy.com/shop/PlasticFusion
UPDATE: New version uses tbuser's new pin connectors V2: thingiverse.com/thing:10541, is much stronger, and prints right-side-up. This is practice for making a heart-gear version.
This design also incorporates a couple of tricks that others may find useful. The center block has two very narrow slices through it, which cause interior walls to form, which help keep the tops of the holes from sagging during printing. Likewise, a cylinder is cut out of the interior of the gears, which serves two purposes. First, it makes a strong internal support for the pin. Second, it makes for less stringing between parts when you print four gears at once, because Skeinforge makes the head go from the center of one to the center of the other, so that the perimeters wipe off the nozzle.
UPDATE: By popular demand, a new version of the center block has been uploaded (BcenterFlat.stl), which doesn't have any internal slits and is oriented to print on a large face. This one is significantly easier to print, though the top and bottom holes do end up a touch tighter than the rest.
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You're describing exactly the reason I switched from ABS to PLA. It is possible to print these with ABS, but it's very difficult and failed prints from corner curling are common. PLA's lack of shrink makes it much better for steep overhangs and dimensional accuracy. Plus you don't even need a heated bed.
I have to say these gears have become my taunting nemesis. I've tried at least a dozen times to print the gears in ABS, but the 'tips' of the overhang curl up as the nozzle departs. After a few layers, it looks like upward flower petals, and eventually the nozzle will fold them over into globs or whack the part off the print bed.
The center prints fine, and if I run a bit of fan, I can sometimes get a useable print, but it's not nearly as nice as the pictures seen here.. the gear teeth are lumpy.
Would these print easier if the cube corners were lying flat on the bed, instead of hole-side-down?
I saw a few other people having problems with the gear tips in these comments. I posted a picture of a failing print.
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UPDATE: The new gear pieces all start with 'B', and correspond to cubeGears3.scad. The pin tolerance worked great for me the first time, but if you have trouble, you can just print out new pins, perhaps scaled slightly. The short pins are for the small faces on the center block and the long pins are for the large faces. The pins should fit tightly into the center block and loosely into the gears so they spin freely.
The SCAD file is fully parametric, so feel free to adjust as desired.
UPDATE: Just added two plates for those of you who don't like to use the multiply feature. These are courtesy of Nick Starno.
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