Wooden Icosahedron Earth Puzzle

thingiverse

This 20-piece earth puzzle will test your geography knowledge! It is also a great challenge to make. The model pictured here is made with Eastern Maple. This puzzle is a wooden version of the printable Earth Puzzle found here: https://www.thingiverse.com/thing:4153383 These .stl files are modified for use with a CNC router. The files are grouped in to "N," "NE," "S," and "SE." Each group contains five puzzle pieces. Pieces labeled "N" share a vertex that lays roughly at the north pole near the Bering Strait. "NE" pieces all share an edge with an "N" piece. Pieces labeled "S" share a vertex near the south pole. "SE" pieces all share an edge with an "S" piece. The files are provided separately and can be grouped and arranged in whatever way best suits your software and router set-up. I recommend milling the pieces in such a way that the wood grain wraps around the globe like lines of latitude. If you look closely at each .stl file, you will notice that one vertex has a greater fillet than the others. The edge opposite this vertex should be oriented in the same direction as the grain. I used a 1/4" end mill bit for adaptive clearing followed by a 1/4" round nose bit for the contours. Once milled, it is important to be precise when cutting the edges or the pieces will not fit together to form an icosahedron and the land masses may not line up. The inner triangular edges of the finished pieces should end up being exactly 50mm at an angle 69.1 degrees from horizontal (the dihedral angle of an icosahedron is 138.19 degrees). The pieces are designed with a few millimeters of overlap that you will be removed when you make the angled cut. I recommend using a tablesaw and sled to position and hold the pieces, and I have included two .dxf files to assist with this. These files are designed to be cut with 1/8" MDF using a laser cutter. The "Cut marker and Adapter insert" file has two pieces. The outer triangle is placed over the back of the wooden piece. Score the piece through the slots to indicate where the cuts should be. This will help you position the piece the appropriate distance from the blade. The inner triangle is attached to the piece with double sided tape and used to hold and rotate the piece within the sled adapter for each cut. The "Sled Adapter" has a triangular hole that accepts and holds the triangle that is attached to the wooden piece. The surrounding shape is what fits my tablesaw sled, you will likely have to modify this as needed. The magnets form the support structures that hold and align the pieces, so it is critical that they are all precisely placed and normal to the edge surface. The "CNC Earth Magnet Hole Drill Jig" .stl I've included can help with this. It is made to accept drill guide inserts such as these: https://www.leevalley.com/en-ca/shop/hardware/jig-and-fixture-parts/101378-drill-guide-insert. The inserts can accept guides for a variety of holes. I used a 1/8" bit and corresponding 1/8 x 1/8" cylindrical magnets. It is important to pay attention to magnet polarity or the pieces won't snap together. The pair of magnets on each edge are inserted with opposite polarity. Maintain the same pattern around each edge and across each piece. Use dab of glue to hold the magnets in place. The finished pieces will need some sanding. I finished the pieces with a few coats of shellac. You can see a video of the piece here: https://youtu.be/wrwjbiOyeqo If anyone ends up doing this project, please let me know and share your pictures!