Recently someone at work got me thinking about 3D printing a yo-yo. I had lying around an unused Ball-Bearing Yo-Yo Kit from Lee Valley. This kit includes all the hardware and instructions to make a wooden turned yo-yo. I never got around to making a wooden yo-yo with this kit so I thought it would be great to use it as the internals of a 3D printed yo-yo.
The first step of this build was to model the yo-yo plastic half in a CAD program. My CAD software of choice is the free PTC Creo Elements/Direct Modeling Express 6.0. The kit from Lee Valley comes with instructions suggesting the hole for the aluminum hubs should be about 1.375 inches in diameter. For the outside diameter I based it off of a Duncan Imperial yo-yo that measured around 2.25 inches. I wanted this yo-yo be a butterfly style so I modeled it as such.
Knowing that 3D prints tend to shrink slightly I adjusted the inside diameter for the hubs in the 3D model. I chose an arbitrary amount, about 0.020″ based on some past experience with my particular printer. I knew I would still need to do a few experimental prints to get it just right.
The 3D printer I am using is a XYZ Printer Da Vinci 1.0 with ABS black filament. I uploaded the STL model to the software, pressed print, and waited 1 hour for it to finish. Partial success; the print quality was good with no lifting from the bed since I used a ABS acetone slurry. The only issue was that the inside diameter for the hub was too small, it measure 1.368 inches, a bit too small for a press fit. With some effort I was able to press the hub inside but ended up cracking the print in the process. After playing with that diameter in CAD and sending it to the printer two more times I finally got it so that the press fit is just right at 1.410 inches.
Assembly is super easy, press one hub each in the plastic halves, insert the ball bearing axle, screw the two halves together, and then add string.
I am very happy with how this project turned out, it was supper simple to model up the yo-yo halves. The yo-yo performs ok, it is very light at 60 grams since the 3D print has only a 10% infill. The kit from Lee Valley is also good but for a future build I would consider making my own. The o-ring gap adjustment system is not as good as using shims would be and tends to come loose during use. Also making the hubs out of stainless steel should add a little more weight to the yo-yo.
The 3D files can be downloaded here: http://www.thingiverse.com/thing:756455