Project 06

Project 06

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Molding and Casting

About 10 years ago, I had the chance to work at Gentle Giant Studios and mold and cast prototypes for collectable figures. Given that, the idea of casting a cube seemed like a simple problem, and so I thought I should perhaps attempt something else, but then I thought, a perfect cube… now that is a challenge! And it was!

  1. Modeling
  2. Milling
  3. Casting (a mold)
  4. Casting
  5. Finishing

Modeling

While the die itself was quite easy to model, thinking about how to make a mold that will be best to pour was not an easy problem.

  1. I wanted to make sure only a single corner is at the top for air to rise to a single position
  2. The sprue should be in a position that doesn’t compromise the sharpness of the edges
  3. There cannot be any overhangs when milling with a 3 axis shopbot
  4. There CANNOT be any overhangs when milling with a 3 axis shopbot
  5. Create a nice key/registration mechanism to ensure the cube stays aligned

model_2

model_1

Milling

Notes on some settings coming. I accidentally milled one side with a tolerance of .05mm and another with .001mm. This actually caused a difference in the fidelity of the two molds. Not critical, but not ideal either.

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Casting (a mold)

Oomoo – 1 part A to 1 part B (very easy to mix, pour, cure). Takes about 1.5 hrs to cure (I left mine over night to be cautious)

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Casting

Clear Resin – 1 part A to 1 part B, this is quite easy to measure. Note: let the bubbles settle, the vacuum chamber complicates things… More below :)

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Poured Drystone – 20 parts water to 100 parts Drystone (basically just mix it to pancake batter consistency)

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Finishing

After casting carefully, the sprue and excess need to be removed and I did that first my hand, then a bit of sanding, careful to keep the sharp edges.

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IMG_9724

 

Vacuuming the Resin

The resin bottles said shake vigorously before use, but I believe I shook too hard/didn’t wait long enough for it to settle. I decided to vacuum the resin to get rid of the bubbles, which seemed to work well, initially. While vacuuming the resin, the vacuum is supposed to reach around -29Hg and it was only reaching -27 or -28. Because of this, the bubbles took a while to settle, and I left the resin in the vacuum chamber too long. Just before I was going to pull the resin out of the chamber, I noticed that the cup was melting slightly, and then instantaneously, it seemed the resin had cured, creating some beautiful bubbles locked inside. Here is an image for the resulting cup.

bubble