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• 

  Created by

  pmoews
• Created on Jan 25, 2012
• Featured on Jan 25, 2012

Johnson polyhedra have faces composed of regular polygons: triangles, squares, pentagons,hexagons, octagons and decagons. There are only 92 such polyhedra. Instructions for making paper models are available, but with stl files one could print more durable examples.

I recently came across the netlib library of polyhedra at

netlib.sandia.gov/polyhedra/

which includes the Johnson polyhedra. I was pleased to see that it would be easy to convert the files to openSCAD polyhedron comands. Polyhedron commands are
a compact way of describing a polyhedron and, when executed, output an stl file.

I wrote a fortran program to convert the files; however a few files had errors. I had corrected most errors with openSCAD's unusual, but marvelous, "thrown together" mode when I was informed that the errors had already been noticed and corrected by George Hart

georgehart.com/virtual-polyhedra/netlib-info.html

There is a link on the George Hart page to a set of VRML files which display the Johnson polyhedra with color coded faces. References are also given.

Using the corrected files I was able to finish the conversion. You will find the 92 scad files in Johnson_Scad_Files.zip and the 92 stl files in Johnson_Stl_Files.zip.

To get a large version of the polyhedra it is best to print a hollow structure. Five examples of hollow polyhedra stl files are included here together with a sample openSCAD file, hollow_j03.scad.

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