Week 9

This time I decided to do something tasty. I made casts for molding chocolate gears that you can play with and then eat. Like every time I started with CAD I downloaded a gear generator and made 3 different gears, imported them to Rhino and made a mold for the silicone rubber.

This is the Rhino file I made and this is the stl file for the Modela.
I got a 165/80/38mm wax block. Using the Modela I uploaded my stl file, made if into png, selected the mm, 1/8, wax, rough option and made the path.

I designed my file in away that it can be milled using only the 1/8" mill while still getting clean and smooth surfaces. Milling process took 27 minutes.

By the end of the milling process, the wax mold was left with a few tiny pieces that I had to break.

I used silicone rubber by Smooth-On to cast my mold. I filled my wax molds with water and poured in to a cup to measure the volume of silicone I need to mix, I marked a line and dried the cup.

Mixture is made from two pre-mix A and B, with a 1:10 weight ratio. On a weight scale, I filled the cup with mix A a bit above the line of the water, then added 1/10 from mix B and stirred for 3 minutes before filling the wax mold.

I tried to get rig of the bubbles by shaking and tapping the mold on a table, but it didn't go so well. Next attempt I'll try to find a vacuum chamber. I let it cure at room temperature for about 20 hours before demolding. Once I did I noticed That three of the gear holes had a trapped bubble that prevented from silicone to fill it. Other than that all surfaces turned out smooth as expected.

Now it was time to post cure the silicone casts. I put it in the oven with Katie's casts at 80 degrees Celsius for two hours and then for another hour at 100 degrees.

I found a chocolate recipe, got all of the ingredients, followed the instructions and made the chocolate. Molded it to my new casts while making sure there were no trapped air bubbles and put in the fridge.

After the chocolate cooled I gently demolded it. Because my silicone cast was defected I had to make the gear holes by hand. Everything fits good, the gears are spinning and they are very tasty.

I gave my sister the mold and she made her own chocolate gears. It was a satisfaction to see it made by someone else other than me.