molding and casting

• Assignment
  design a 3D mold, machine it, and cast parts from it

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• This is what I made this week. I describe how to make it below.

• Design What I Wanted to Make
• I decided to make a icosahedron（正20面体）.
  Here is how I modeled it on Rhinoceros.
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• Mold Design
• I modeled a positive mold in order to make a negative mold.
• I modeled a box which is as large and long as the modeling wax I bought.
  Then I made two ditches and put each half of the icosahedron.
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• Here is my mistake I found later.
  The top of the box and the top of the icosahedron are at the same height.
  The top of the icosahedron should have been under the height of the top of the box.
  This mistake made a poured silicon not cover the top of the icosahedron well. (Actually, later, I managed to do it with surface tension of silicon.)
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• Machine the Positive Mold
• Here is the instruction of Modela and Modela Player 4 I wrote before. (Sorry, only in Japanese for now)
• Here is the result. Very good!
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• Here, I found another mistake.
  The top edge of the ditch was shaved and curved a little.
  This was because the endmill length was too short for this design and not-the-edge part touched the edge of the ditch.
  Next time, I need to change the design of the mold or to use a longer endmill.

• Cast a Negative Mold
• I tried to use OOMOO 25 but worked very bad. Here is the result.
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• It seemed the part-A liquid is too viscous.. is it?
  I don't know the normal of it, I uploaded a video of it, please let me know if this is not in a normal condition.

• After 4 trials and failures, I gave up using OOMOO 25.
  I used ブルーミックスソフト(Blue Mix Soft) instead. It worked very well.
  It cures in about 30min.
• Tap the mold after pouring the silicon like this video (from 6:15) to let bubbles go out.
• Here is the result.
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• Cast a icosahedron
• I used a Smooth-Cast 300.
  It worked very well but it cures very fast, you need to do the process quickly.
• 1st Trial (Failure)
• Firstly I tried to let the mixed liquid go into the mold with a tooth pick, but it is already viscous just after mixing the liquid part A and B, it didn't go well.
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• 2nd Trial (Sucess)
• The successful solution was this.
• Firstly, I poured the mixed liquid to each part of the mold, separately.
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• Then, waited until the liquid started to cure.
  It starts to be white when it starts to cure, so it is easy to recognize when it starts to cure.
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• Then, the liquid doesn't fall out so easily, combine the parts of the mold, then wait until it cures thoroughly.
• Here is the result below.
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