Introduction: CAD a D20

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About: Thingiverse: https://www.thingiverse.com/theengr42 GitHub: https://github.com/TheENGR

The goal of this instructable is to CAD a D20 (icosahedron) with only 1 parameter


Link to my object

Supplies

CAD Software, I use OnShape as it is free

Step 1: Inscribed Pentagon

  1. Make an inscribed pentagon on the "Top" plane
  2. Make a point of the pentagon be connected to the "Right" plane
  3. Add your one dimension to say how big the circle is
  4. Add a construction line from the constrained point down along the "Right" plane
  5. Make the construction line be equal (same length as) the side of the pentagon
  6. Add a construction line from the bottom of the pentagon to the outside of the construction circle

Step 2: Find the Top

  1. Make a construction circle from the top of the pentagon to the end of the construction line
  2. Draw a construction line up from the center point of the pentagon to the circle

Step 3: Find the Center of the Object

  1. Make a construction circle from the outside of the pentagon's construction circle to the top of the D20
  2. Make a construction line from the outside of the pentagon's construction circle to the construction circle you just drew
  3. Force that line to be "vertical"
  4. Create a construction line from the midpoint of the last line towards the middle of the D20
  5. Constrain the end of this line to be under the top of the D20

Step 4: Loft the Pentagon

  1. Loft the pentagon up to the top point found
  2. Loft the pentagon down to the bottom point found

Step 5: Rotate and Mirror the Shape

  1. Rotate the object 5x evenly around one of the edges on the "bottom" of the shape
  2. Mirror the object about the face of the shape to fill the resulting hole

Step 6: Boolean Merge

  1. Merge together all of the parts to make a single part

Step 7: Finish!

You now have a "blank" D20!


Feel free to add numbers to it or whatever else you want!