A small toothbrush case, using filament as hinge.

This was an experiment on filament-based hinges, and a great success.
The locking mechanism required more iterations. In the end I integrated it into the inside edge, which finally made it reliable and strong. The final model can be printed without any supports, the holes in the hinge have a sloped top.

The ends of the hinge have a conical recess. Use a piece of 1.75mm filament, melt one end with a lighter, push it flush into the cone using a cold tool, then cut the other end with slight overhang, melt, and push into its cone to lock the filament in place. There is an odd number of hinge bushings, so the ones holding the melted end don't rotate relative to each other.

It's really small, check the inside dimensions (in mm) listed in the images. I postponed turning this into a parametric (Open Scad) model, but will use the hinge for larger projects.

Designed in Rhino3D, the original .3dm, as well as .stl, .obj, .stp, and .igs files, are included. The Rhino3D file and the parts.* files contain the solid-union and solid-difference hinge part solids, before all boolean operations.