Valentines day may be a "Hallmark holiday" to most, but that doesn't mean that it can't be a fun one. I happen to be a big fan of chocolates, but virtually all chocolates come in cheesy overpriced heart-shaped boxes. This simply would not do. I decided that any valentine I would give must be personal, unique, and preferably, have a unique story behind it. It was then that I decided: I was going to 3D print my valentine.
Amazingly, there don't seem to be any companies that offer small-batch 3D printed valentines, with the exception of one company that 3D prints your face in chocolate, which I think is just weird. This only strengthened my resolve: I decided to design and print the chocolates myself. I loaded up some CAD software and began working. I had to keep the design relatively simple since I had concerns about the maximum resolution available to me, so made some pretty basic designs in Microsoft 3D Builder. Side note: 3D builder is a surprisingly powerful and easy tool, and a great alternative to AutoCAD or SolidWorks for basic projects like this. Since this was my first time working with a 3D printer, I decided to also make some additional Valentines designs for fun (the interlocking gears would be impossible to create a mold for)
Now that I had a design, I needed to print it. Some people have experimented with directly 3D printing chocolate, but have had mixed results from the extrusion process because of the low melting temperature of chocolate and its high viscosity. Instead, I decided that the best method to print chocolate is to create a mold. Formlabs has a tutorial on this, but they use vacuum forming instead of mold making, and completely gloss over the method. While Formlabs has a superior printer in many ways, their resin is toxic and a skin irritant if not properly cured. Even with excessive curing and safety precautions, I would not feel comfortable using this resin with items that interact with food.
Instead, I decided to use the LulzBot extrusion printer with PLA filament to print a positive mold of the chocolate. Because of the limited resolution of extrusion printing, I had to make the chocolates a little larger than I had initially planned, but managed to avoid using too much filament by using a 20% fill rate. This filament is food-safe, but as an extra precaution, I chose to thoroughly wash my prints before moving to the next step.
Next, I needed to create the negative mold. After doing a good deal of research, I decided to use SortaClear 40 food-safe silicone mold because it is easy to work with, food-safe, and transparent. I glued down my positive molds to a plastic container I had lying around, then started mixing the silicone. The silicone has a 10-1 mix ratio, and needs to be de-gassed in a vacuum chamber before pouring. This degassing ensures there are no bubbles in the silicone, so it can form a tight mold around my positives. SortaClear 40 can also cure without requiring an oven, which is very important for my use case, since I didn't want my PLA prints to melt during the curing process.
After letting the mold cure in place for 36 hours (only 24 are required, but I decided to give it a little extra time) I removed my PLA prints, washed the mold, then put the silicone mold in the oven for two post-cure cooks to help strengthen it. After washing the mold third time (I want to be really careful about anything that I ingest, despite whatever assurances the labels give me) I made my first trial run of a chocolate... and it was delicious! (also, I didn't get poisoned, so I felt ready to start making them for friends)
To turn chocolate chips into custom chocolate bars requires melting and pouring. Although milk chocolate is easier to melt and pour, I happen to be blessed with functional taste buds, so dark chocolate was the only real option. The trick is to constantly mix the chocolate as you melt it in order to keep the components from separating. The best way to do this is through slowly melting them on a stovetop, but microwaving for 10 sec at a time, then mixing, is another option for the lazy. Once the chocolate is melted, I carefully poured it into the molds. After pouring, I used a toothpick to prod at the interface of the chocolate and the mold to make sure there weren't any air bubbles that would interfere with the shape of the chocolate. I then put the chocolate in the fridge for a few hours to harden, and then removed and wrapped them. Success!
Note: the large heart chocolate has personal information printed on it. To protect the privacy of my friends, I am not showing details of the chocolate, but it looks even better than the key!