Googly Eye Button

To Print:

• 0.2mm layer height
• 0.4mm nozzle width
• Needs strong bed adhesion
• No supports
• Infill: at least 30%, triangles or grid recommended.
• Bridging: Remember to turn down the flow for your bridges. Most of the bridges here are going to be visible, so turn on your best settings. (For instance, I had my filament set to 95% flow, and bridges set to 90%.)
• Removing from bed: There are two interlocked pieces here you want to free from the bed separately, to prevent breakage. From the top, you should be able to see a bit of the central (pupil) piece, and there is space to use tweezers and carefully pop it off the bed. 
• Optional: If you pause and switch filament color a couple layers in (I switched between 0.4 and 0.6mm), the outline and pupil of the eye can be a contrasting color.

Sewing:

• The holes are big enough for regular weight yarn and smaller yarn needles.
• Make sure your fabric and stitches aren't bunching up underneath and interfering with the exposed part in the middle. 
• You could hot glue these instead, but you'll want to make sure the glue doesn't get on the inside.

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The filaments shown in the photos are Fillamentum Luminous Green PLA and Printed Solid Jessie Blue Ice PLA. (And a white PLA that is old and not performing quite as well anymore :P)

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Misc

So, this design turned out a bit more complicated than I was expecting:

1. PLA at this scale is way too light to run the track/axis around the outside of the pupil piece; gravity won't move that piece. So the axis had to be at the center.
2. The moving piece needs to be offset from where the button will contact the fabric, so the button must be printed face down (to avoid supports and minimize post processing.)
3. The center of gravity of the pupil piece needs to be close to the center/axis vertically, but horizontally favor the direction of the visible pupil. Some elements of the pupil piece are there to nudge the weight distribution in the right direction.
4. The farther up the column of the pupil piece goes, the more mass you place below where you want the center of gravity to be. So shorter is best.
5. This means bridges, and visible ones. Which means planning so the bridges will look nice enough/not stand out too much.
6. This also means some very precise modeling so that the slicer can handle a bridged over area with a hole in the middle. Here, I build up to it layer by layer with triangle shapes, and finally transition back to a circle.
7. Bridges are always at least a little messy, and not reliably going to give you the mathematical precision you need for moving parts this small. So the hole that the bridges work up to is offset so it can then work up more reliably in a cone shape.
8. We also need the pupil piece to have minimal vertical wiggle room, thus multiple cones.
9. When I enclosed the button at the top, so the pupil piece was entirely covered, I was having at best a 50% success rate for getting the whole thing off the bed without breaking the pupil piece. So I've left it open, and the top of the pupil piece has flat sides for grasping and clearance around it. The back of the body piece then continues up so that the top of the pupil piece won't touch whatever material the button is attached to.