Gear-Heart Necklace
For an anniversary present, I planned to make a heart necklace with gears that spun when the chain moved.
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Starting the project, I designed a CAD for the overall model. First, I designed the heart shape and extruded it to form a 3D shape. Next, offsetting the outer contour inward, I created an inner heart-shaped cavity where the gears could sit. I then carefully planned the locations for the gears, taking into account their specific geometries with the ball chain I bought. With the CAD completed, I wasn't sure how to make it. 3D printing it would be easy, but it didn't look as nice as a metallic one.
Thus, I learned to waterjet, and after converting my CAD to .dxf files, I decided to create 3 layers for the heart necklace: the aluminum base, the gear and outer shell, and an acrylic cover. After cutting my pieces on a waterjet and examining their size, I found that they came out too big for a necklace, at about 1.75 inches in length.
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Going back to my CAD, I scaled everything down and tried again, but this time, the gears were too small for the ball chain to properly wrap around and catch each tooth of the gear.
Redoing my CAD once more, I optimized the size of the heart and gear and moved on to the final assembly. Like before, I cut out an aluminum base and outer cover for the first two stages of the necklace. Then, using a laser cuter, I cut out the cover and the gears. The cover had holes which I tapped so screws could be used to hold the assembly together. With clearance holes in the gears, they sat and spun freely about the screw. Finally, I drilled countersinks into the base of the necklace so the screws would sit flush with the base.
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Before assembling the necklace, I took the finished aluminum pieces to the metal shop, where I polished the surface to leave a metallic luster.