I thought that this was a really neat Instructable contest. I wanted my ornament to take advantage 3D printing so I wanted to have multiple interlocking parts that would come out as the ornament was printed. I design many items for my shop on Shapeways, Joy Complex, so I'm pretty familiar with the design guidelines for SLS (Selective Laser Sintering) Nylon. So this ornament is designed with that material in mind (though the model should print using different processes, only you'd have to snap the moving parts in place).
Step 1: Step 1: Drawing
My first step was to come up with a design! When I read about the contest I was about to go to sleep. But just before I did, a design came to me so I turned on a light and quickly sketched out what I had in mind. (Not the best drawing but I was pretty tired).
Basically I saw an ornament that had 50 stars and 13 stripes. I also wanted it to be in a traditional Christmas globe form.
Step 2: Step 2: Bounding Box
I opened up Rhino which is the CAD program I use to design things in 3D and began getting to work!
The rules stated that the ornament could be no bigger than a 3" box. I do all my work using the metric system, so I converted that to about 76 mm and made a bounding box with those dimensions. I made a globe in the middle of that box that was smaller than the minimums because I knew the 13 movable stripes would take up a good portion of the design limits.
Step 3: Step 3: Modeling the Design
Using the globe as a guideline, I created an array of stars on 13 trellis shapes. It worked out that I had 52 stars. However, I knew that they would get replaced with the year (MMXIV) and my initials (JSB). So the stars I arrayed over the trellis worked out!
Step 4: Step 4: the 13 Stripes
I created the stripes to sit on pegs attached to the trellis. Originally they were rectangular but I thought making them more pennant like gave the ornament a sense of movement through the air - like a shooting star. So I tapered them and aligned them to the pegs.