I saw a really amazing modular straw construction set on Kickstarter called LINX, and I wanted to try to create my own using the 3D printer in the Instructables office. The basic idea is to create small plastic parts that can connect to regular plastic straws to create unique geometric 3D sculptures.
I grabbed some straws from a local Chipotle to use for testing. I measured the straw's outer diameter at 0.23" and inner diameter at 0.20". I decided to start my first test connector pieces with a max diameter of 0.21". Following the LINX design, I made the cross section of the piece that actually fits inside the staw an X shape, instead of a full circle. I figured that this would probably allow for easier on/off since air can pass freely through the connection.
I started by created two intersecting ellipses and extruded them into 3D. I added some taper to the extruded ellipses (fig 2) and used mirror3d to create a symmetric shape (fig 3). I copied this shape 17 times (total of 18), and I arranged the shapes so that they are spaced 60 degrees from each other around a central point. This way you will be able to connect the straws in equilateral triangles (no straw cutting necessary). I added a sphere in the center to join all these shapes (fig 6).
I 3D printed the part on an Objet printer (the grand prize in the Make It Real Challenge!) and fit a straw on it to make sure it was the right size (see the image above). The fit was good; secure, but easy pulled apart. However, I decided that the size of the connector was a little too large and decided to go back to the drawing board (AutoCAD) before printing more. Stay tuned for more updates.