Circle sections are linked together with snap hinges. Sections come in radii of 1, 2, 3 and 4 whatever units. Regardless of radius, all sections are of the same area and volume.* Connect enough sections together (number required = radius squared) and you can turn the chain into a circle or stretch them out lengthwise to find the circumference. Wedges also snap into place vertically to create volumes. *Skeptical students? Use hollow versions of the wedges and fill with sand or water, then measure required amounts for each radius size. They should all come out to be pi times whatever your radii are scaled to.AutoCad drawn object exported as a stl file, imported to makerware and printed on a replicator 2. Raft, no. Supports, yes. Four walls and 20% infill. Lesson works best if radii correspond to one of something. Inches or centimeters are good so i have the files scaled both ways. Inch models feel good in the hands but centimer wedges are cute. The smaller ones don't stack as cleanly as the big ones, but you can turn them out a lot faster (I wonder why that is). I tried two hinge types: c-clip and ball and socket. C-clip seemed more certain to latch, but ball and sockets are easier to clean up the support material on. I included files for hollow versions of the wedges so that their volumes can be measured and proved to be equal.