Last Monday (3/27) we received the 3D printed parts of our updated mold as well as the hard ABS hinge. The print quality and precision was worse than we were hoping, but in light of Skylab being offline, we’ll take what we can get!
Casting the ABS hinge in silicone was a success; both parts came out cleanly, and are ready to be bonded this week! Below are photos are the silicone parts:
As for the finger mold, casting this was less successful. From the get go, the mold print didn’t seem the cleanest or most exact, and we were worried how the lack of precision would effect the small gaps between our hollow channels. Additionally, while pulling the silicone part from the mold, we noticed that the bottom of the part was incredibly stringy/shredded, much more so than the hinge part. In addition to this, there were many air pockets in the part, which will definitely impact the functionality of the part:
We attempted to bond these parts after cleaning up the silicone strings, but the unintentional air pockets impaired the shape too much for them to adequately be flush against one another.
When casting, we made sure to apply silicone to both the top and bottom parts as Garth recommended, to avoid issues. We believe this issue is a result of the print quality; it appeared that silicone sank into the 3D printed part, causing air bubbles.
While designing the new part, one of the biggest design changes we made was modifying the ratio of silicone thickness above and below the hollow channels. Originally, they were roughly the same thickness, but the new design made the bottom 75% thicker than the top. We realized that we could roughly test this innovation by adding a solid piece of silicone to the bottom of our original part from a few weeks ago, making the bottom thicker.
Using a random, simple mold we found at the silicone casting tables, we cast and bonded this piece to the bottom:
This original part has a hole where the tube meets the silicone and, unfortunately after trying to patch it multiple times, we were not able to get it to fully work as intend. That being said, we were able to see a bit of bend when we quickly injected air into the part, giving us some validation to support this design change! The video to this test is linked here 🙂
We’ve re-casted our original part design along with the bottom “extension” so that we can hopefully retry this test without leakage to gain stronger validation on our idea.