This week, we had to design a mold and use it to cast a part. This proved to be significant to furthering my final project. I prototyped a medium for seeds using Ecoflex 00-30, and I used the protoype to test the germination potential of silicone.
First, I designed a 3D model of the proposed mold. It was tricky to do correctly, since I was creating a negative of the casting. The goal was to have a small silicone pocket with various sizes for different seeds. I wanted the piece to be a single unit, so I creating a bit of overhang. Designing in Fusion was helpful, because I was able to identify points of failure during the milling process and adjust my design (I made it shallower so that the bit wouldn't collide with the edge of the wax).
Errors in Fusion.
After designing the mold, I tried to find a wax block -- unfortunately, I got there a bit late and there weren't any clean blocks left. Thankfully, my mold was shallow, so I just used the other side of a block. I had to adjust the orientation of my design so that it would work properly in mods. Eventually, it looked accurate, so I sent it off to the shopbot.
Shopbot toolpath (hover to expand)
Because I checked in Fusion first, I was confident that there wouldn't be any issues during the printing process (and there werent!)
Milling the mold
In the end, I was left with a good mold for my seed medium.
Final Mold
Next, I had to decide the type of material that I would use for the medium. We had several options within the shop, but I knew that I wanted something that was flexible enough for a seed to push through during germination, and clear so that I could monitor its progress. Ecoflex 00-30 was the best option:
Ecoflex Box
I mixed equal parts A and B, and then poured it into the mold. I tapped it a bit to get the bubbles to release. During the curing process, the Ecoflex looked milky/cloudy, but that was most likely the bubbles.
Curing the silicone
I left it overnight in the shop, and when I came back the next morning, it had fully cured. I am extremely happy with how it turned out!
Silicone medium
Finally, I had to do a bit of DIY building at home. I placed a cucumber seed in one of the pockets and then wrapped the silicone in foil (to block light during germination). I then suspended it with some string in a mason jar and punched a small hole in a plastic cup to allow water to slowly drip onto the cavity. It'll be about a week until I see any results.
Bootleg hydroponic germination
