Week 9

Molding and casting

Machine: monoFab SRM-20 (Software: Vpanel for controlling the end mill’s position, Modela Player 4 for creating the tool path)
Material: Clean wax , Silicone rubber and stiffening agent, Resin cast
Software: Fusion 360 for 3D modelling

First try: Fablab Kamakura Logo

Making the data

I couldn’t think of anything particular to make, so I made a simple shape with Fablab Kamakura’s logo on it. (all photos can also be viewed here. View/download the 3D data here)

Making the molds and casting

(all photos can also be viewed here)
I milled the wax to create the positive mold, poured in rubber to create the negative mold and cast the resin part.


Mistakes

  • I added two holes (2mm in diameter) in the mold : one to pour the resin in the mold, and the other to vent air while pouring. But since they were too close to each other I couldn’t mill the space between them.
  • To save time I started milling just the logo section several times with different end mills.
    At the end I forgot to do the “finishing” (that's why there are circular rough cuts around the logo).
  • After milling the wax, I poured in the rubber and left it in the Fablab to cure for a couple of days. The rubber didn’t settle into the dents in the logo. Though I did tap the mold as I poured to release bubbles, I should have been more careful and poured smaller amounts of rubber at a time around the logo.
  • I had a hard time pouring the resin in the rubber mold. I learned that I should make wider holes.
  • The resin cast was a little sticky and it didn't cure completely. The liquid ratio (1:1) must have been a bit off.

Second try: Sakura (Cherry blossom)

Making the Data

I decided to make a different mold (with a wider pouring hole) to cast sakuras which are currently blossoming in Japan. (all photos can also be viewed here. View/download the 3D data here)
I made enough room in the center of the flower to insert an LED. Since the petals where going to be thin, I added venting holes at the tip of each petal.

Making the Molds

(all photos can also be viewed here)

The First Sakura

  • The LED sank to the bottom.
  • The resin cast didn’t cure that well again. This time I didn’t stir the liquid enough.
  • (I cut off the resin that leaked with scissors. )

The Second Sakura

  • I folded the legs of the LED when inserting it in the cast, so that it won’t sink to the bottom and it worked!
  • This time I carefully measured the liquids and stirred it well and the resin cast finally cured completely.
  • But after pouring in the resin, I pressed the mold which made it leak around the petals.

The Third Sakura


The third cast was pretty successful, but I still have to improve the mold’s data so that the silicon molds fit together and the cast won’t leak.

(all photos can also be viewed here)

What I’ve learned

  • Consider the tool before designing: How detailed the designs are. How deep to mill (The milling depth should not be too deep or the collet might hit the the material).
  • Drafting the walls will make it easier to take out the mold.
  • If possible make the pouring hole of the mold in the shape of a cone not a cylinder.
  • Add registration tabs so that the molds fit together and don't shift.

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