Wine charms are great, but there's there are two problems with them: first, they generally don't celebrate the world's most fun transcendental number. Second, they don't work for plastic cups -- and if you're having a rockin' Pi Day party you probably won't be busting out the glassware. So I decided to make some π-themed beer charms at TechShop.
Step 1: Designing the Charm
The key things I wanted in a beer charm was that it would fit around the lip of a plastic cup and stay there, and that it had some room to write your name on it.
I started in Illustrator and found a font that had the profile I was looking for: Stencil Std - it is curly, with one π leg thicker than the other (giving space to write a name). The legs have to change, however: the should be bend inwards to grip the wall of the cup.
Starting with a 1" x 1" artboard, draw a π and scale it to fit the artboard. Next, turn the text into an outline with Text > Create Outlines.
To rearrange the legs (which sounds like something a mobster would do), you'll have to cut the path: Carefully draw a line across the corners of the leg that you want to cut, then use Object > Path > Divide Objects Below.
Finally, rotate each leg inwards until it creates a pinch at the bottom and leaves a gap at the top, for the cup rim. The only way I found this to get exactly right is to test out each change with a real charm until it works for the cups you have.
Step 2: Make the Charms
I first tried 3D printing the charms, which had a few problems. First, importing the shape from Illustrator > DWG > Inventor was tedious; it came in as an open loop, and it took many many passes of the Close Loop tool to finally get it closed so it could be extruded. Second, printing multiple copies of a part in ABS on a Makerbot Replicator is difficult, at best - when the extrusion nozzle moves the second part it's incredibly hard to get it to stick to the build plate. The solution is to print one piece at a time, which requires too much interactive time for making a party-quantity of charms.
Instead I settled for a handful of 3D printed charms and decided to do the rest in laser-cut acrylic and wood using the vector image from the last step.
If you make sometime like this, experiment with sizes, shapes, and materials - I'd love to see what you come up with!