Case fabrication process¶
The case design is made in Rhino and then 3D printed in PLA. It is made up of two parts that are linked together by plastic inserts and screws. The top piece has a space to place the OLED screen and screw it with self-tapping screws. It has a hole to place the button and some bas-reliefs for the PCB, which is screwed to this piece.
I used the same design for the renders but I adjusted the fillets. I used the renders for the final presentation slide.
3D printing¶
I did several tests on the bottom piece to see how the link to the shoe might work better. My initial option was to have a piece that would be attached to the shoe using the laces to support it. Then the device could be taken out and put on easily. The idea was to put a rail to slide it into place and some neodymium magnets. That was a bit complex and in order to simplify the process I decided to try incorporating the holes in the piece to pass the shoe laces.
This ended up being the winning option. The other version that I did was to attach a lace with velcro to place the device around the ankle.
Find the final files here:¶
Molding and Casting¶
After much deliberation I decided to simplify the mold for the molding and casting process. At first, I had thought of making a two-piece wax mold with a heart. But finally I opted to make a one-piece wax mold and a 3D printed inner piece. This option allowed me to make the mold much faster and have time to do several tests and experiment with the amount of glitter.
I made the mold following the processes of Molding and Casting week. The only difference was that when placing the inner piece, I had to see that everything demould and also take into account the tolerances.
Use the quick-drying silicone, which means there are only 8 minutes of work-time and then 25 minutes of curing.
I first tried a colorant that was not specifically for silicone. This made the cure time last longer and the working time less.
Then, I got different glitters and started by adding two glitters to the silicone mix. I added more or less 20% of glitter. The result was a slightly stiffer silicone than the one that did not have glitter but was flexible enough to unmold. The color was homogeneous and there was no need to add colorant to the mixture.
The second test was with the green glitter. I decided to add more glitter, almost 50%. This made the material very hard, made it much more difficult to unmold the part and made the part more brittle.
For the third test I wanted to try with less glitter. I added a single glitter and approximately 10% of the total mixture. The texture was perfect, flexible and soft to the touch. It was slightly more transparent, which goes well with the intense color of the 3D printed case.
