Sunday, March 21, 2010

Working Geneva Wheel

Today I built a functional Geneva-drive wheel , downloaded from here at Thingiverse. The files were shared by user PrintTo3D (Bradley Rigdon) who operates an affordable 3D service bureau. Except for one particular detail it's a perfect model for the SD300 because the flat, smooth surfaces slide nicely over each other and the 2-dimensional contours cut nicely in the SD300's XY build plane. (Click any picture for a closer view.)

The model was built within this 1"x5"x8.5" block. I didn't try to optimize the layout, so there's a lot of wasted volume above move of the parts due to the height of the tallest post. By carefully stacking the parts I think it's possible to build two whole models in the same volume of material.

The one troublesome detail is the thin posts in the center of the caps. They built okay, the post on one cap (bottom center) broke off when I was prying the model apart for this picture. No doubt it would be wise to build the caps with the post parallel to the build plane for greater strength.

Here's a closeup of the text embossed on the driving wheel. I didn't weed out the material inside the letters, but the outlines are nice and sharp.

Here's a short video showing how the Geneva drive works. When the driving wheel is turned continuously the driven wheel turns intermittently.

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