Spirograph!

thingiverse

A spirograph! for a 3D printer. I used Catarina's Spur Gear Script for a lot of this, then tore out the most interesting parts and put in my own. Thanks/sorry! Included are OpenSCAD files so you can change pretty much anything. OpenSCAD is so cool. If you make one I would love to see it! My 3D printer is unfortunately not done yet. I couldn't make the holes on the gear evenly spaced; they get farther and farther apart from each other, like a curve. It would be great if someone could show me how to fix this. Also, I'm not entirely sure the holes are big enough, but they should be pretty roomy. If not, tell me and edit the OpenSCAD file! Oh, I also put an .stl of a weird little gear that I made with Catarina's script in. It'll make a design though! added: option to make the stator a ring instead of a square, but don't use it yet. There's a weird half solid thing filling a couple of the teeth that i figured was rendering weirdness, but thingiverse is rendering it like that too. Any ideas? edit - it appears that the rendering weirdness is a thin sheet - you might be able to cut it off. Still, I don't know if it will work. caveat maker. added: aron says the fit is too tight, so I edited the defaults on the .scad and changed the .stl. Also, before, the number of teeth on the spirograph was twice the number of teeth on the gear, so it made an oval. Fixed that too. Thanks aron! added: changed the addenda and dedenda for a (hopefully) better fit. No big deal, though. Instructions Print the first part. Print the second part. Place pen in hole. Rotate gear with pen in it. Have hypotrochoidal fun! Some notes on making compatible rotors (gears) and stators (frames): You want the diametral pitch (not to be confused with pitch diameter, the nominal diameter for a gear) of the rotor and the stator to be equal. Diametral pitch is number of teeth over pitch diameter. For example, in the defaults for the openSCAD script, the number of teeth of the stator is 48 and the pitch diameter is 72. The diametral pitch is 48 / 72 = 2 / 3. Coincidentally (?), the number of teeth of the rotor is 22 and the pitch diameter is 33, giving a diametral pitch of 2 / 3, so these will fit. In a perfect universe, gears with the same teeth width will mesh, but I'm guessing printer irregularities and shrinking plastic make them too tight. You might want to make the tooth widths of the rotor a little smaller than that of the stator. Also, as aron pointed out, if the diameter (or teeth number - the are/should be proportional) of the rotor is half that of he stator, you get an oval. There's a lot of math going on here with greatest common factors and whatnot. Try experimenting with different proportions and prime numbers to get different patterns.