I bought a water bottle about two years ago after my old one was stolen (I know, who steals a water bottle!?) While the new bottle was much better, since it was insulated and could keep water cold for more than a day (with ice added in) one of the things I didn’t like about it was a small rubber ring used to seal the cap. The rubber ring had a split in it (maybe to assist with the seal?) and it was difficult to clean, and eventually it broke from attempts to vigorously clean it.
I replaced the sealing ring by 3D printing a small mold and then casting a replacement using Smooth-Sil™ 940 silicone. The silicone is a two part mold, with a volume of 100:1 for part B to part A, which is why you get a giant tub of silicone along with a small bottle of whatever the red stuff is.
This was my first silicone casting at home for a personal project. I’ve done casting at work for prop making, but this time I didn’t have a vacuum chamber, and I was doing a tiny part all by myself.
So how did it turn out? Pretty good! I used a digital scale and filled a cup with 10 grams of part B, then added 1 gram of part A and mixed it all up with a popsicle stick and smeared it into the cavity of the 3D printed PLA mold. I let it sit overnight then used a sharp knife tip to pry it out. There was a thin skin around the piece but it peeled right off.
So how does it fit? It’s good but not perfect. If I make another one I may decrease both the inside diameter and outside diameter. It could fit a bit more snug, and it could have just a wee bit more clearance when inserting into the bottle. (I’m guessing between 0.1mm and 0.2mm, maybe)
I’ve got plenty more silicone, and it is food-safe, so I want to experiment with making some food molds, and yeah, I’ll probably 3D print the objects to create the molds from, taking a page from Anna Kaziunas France.