Design Make Share: Foldable Tetrahedron Example

How does the Design Make Share method work? Here is an example.

PROBLEM/CHALLENGE: How can an object be printed that has smooth sides?  (3D printed object can have a layered surface texture as an artifact of the printing process.)

DESIGN: I was brainstorming and realized that by printing an object flat on a smooth surface, the object could be folded into shape and have a smooth surface on all sides. I decided that I would design a tetrahedron. I created the design in a program called FreeCAD. Designing a flat object that could be folded into a tetrahedron required careful examination. What are are the angles for the triangles on the face of a tetrahedron? How many faces does a tetrahedron have? What are the internal angles where faces meet? What are the angles of the folds (bisected internal angles)? How to connect the faces so the object would fold into the right shape? I saved an .STL file of the design for use.

MAKE: I used Slic3r to slice the model for 3D printing. Right away I found out there was a problem with my 3D model and I had to use a program called Netfabb Studio Basic to repair it. I was then able to use Slic3r to create a gcode file with the instruction on how to print the tetrahedron. I used Repetier-Host to send the gcode instructions to my Printrbot LC. The result was a very tiny model that could fold into a tetrahedron but quickly fell apart. I went back to FreeCAD and scaled the part up and made the first layer a little thicker. I then repeated the steps to get a foldable tetrahedron with smooth sides!

SHARE: I shared my design and photos of my tetrahedron at and on this blog. Now others can benefit from my idea on how to print a 3D object with smooth sides.

I could have read about high resolution printer that produce smooth prints. Instead I learned about digital design software, the construction of a tetrahedron, fixing STL files, 3D printing, blogging and publishing open source designs. Which experience do you want for your students?