Planetary Wobble Teeth Gear

Basically a regular planetary or epicyclic gear, but with a novel approach in toothshape. The Background is, that regular 3D printer are working much more precisely when using round instead of sharp edges for a tooth shape. Perhaps even the stress distribution in the teeth is improved, due to the similarity to bones. The gear can easily be modified by changing the parameters of teth on the sun or planetary wheel, the tooth width, the height or the number of planets. Right now the planet holes are setup for regular skate bearings. Design is still untested.

20140309 - Update 1: I noticed some misalignment in the gears, I already fixed that but I wait to upload the next version until I also figured out one misaligned polygon in the turning point between tooth valley and top.

20140309 - Update 2: Okay, the new model is online. Now I fixed the polygon the quick and dirty way. Please make suggestions if you know how to tackle this issue other than adding 0.01mm to the tooth radius.

20140311 - Update 3: after failing to compile in a sufficient resolution as it is (tens of gigabytes of RAM and hours of compile time later...) I am now working on a solution of getting the job done by first generating dxf files and extruding those in 3D. Compiling separate gears also didn't work.

20140313 - Update 4: finally, it compiles using about 130min and 5GB of RAM. Saving as stl takes also quite a while.

20140315 - Update 5: noticed and fixed a bug in calculation of planet rotation for placement, in the center hole calculation as well as a necessary change in orientation when changing the number of planets.

20140317 - Update 6: okay, so I built it. Unfortunately, the tolerance of 0.4 was quite perfect for the distance between the planets and the annular gear, but too much for the sun gear. Further work needs to be done.

20140530 - Update 7: I tried to work with the cutting edge offset function of the experimental openscad build, but it seems the tolerance hast to be calculated in dependance of the gear radius. Further investigation is needed. I also thought about printing the gears one at a time, since otherwise they for sure won't make a perfect fit.

To compile just run create.sh. First it generates .dxf files which will later be extruded and saved as .stl. The parameters are mainly stored in wobblegear.scad which also provides the 2D gear function.

Printable without support. Right now the sun center hole is dimensioned for a M5 nuts/counternut/bolt, the planets for eight regular skate bearings with 22x7.7mm, 5mm distance piece. The image only shows the 2D view of the gears without holes, because it takes a looong time to render.

Right now, it's setup with 20:40:100 teeth, so if the annular wheel is fixed we have a 6:1 ratio.

Please note the following:

-gear radius is calculated via teeth dimension and quantity

-changing the teeth quantity/dimension may result in the need to adjusting gear alignments in multiples of alpha.

-right now I am testing with tolerance increased to 0.4 because 0.2 was too less.