2-Piece Mold
For this fabrication homework assignment, we decided to create a 2-piece silicon mold of a travel-sized hand sanitizer bottle. We used this video as a tutorial. Initially, we ran into a bit of trouble with setting up the mold and had to seek assistance from Jonathan, who helped us decide on using clay to prop the hand sanitizer up in order to create the top half of the mold. We also started to mix some alginate at first because we saw another group using it, but thankfully before we poured the mold, Jonathan came to the rescue and told us that we needed to use silicon for the mold to be stable enough. After these hiccups, we managed to create the first half of the 2 piece mold as a group.
After setting, we had trouble removing the mold from the plastic container because we had forgotten to use the mold release spray. We decided to cut the plastic cup to remove the mold and use a new one for the second half. Since we needed to pour more silicon to make the bottom half of the mold, Giang cut out the bottom of the new cup. Following the video tutorial, we knew that we needed to stick a dowel on the hand sanitizer bottle to create a hole for the casting process. Nery tried using every available type of glue to secure a small wooden dowel onto the hand sanitizer, but none of them worked, so Giang made a dowel out of clay and pressed it onto the bottle. This worked better than we thought! To make sure that the mold stays secure in the cup, we used more clay at the bottom to support the whole structure.
Once the entire mold was set, Giang and Nery removed it from the cup to begin casting. The two pieces of the mold were stuck together even though we had used mold release, so Giang and Nery decided to use a knife to cut through and try to separate the two pieces. Giang had to cut through quite a bit of the silicon in order to pull the two pieces apart.
Nery also had to use the knife to cut out the holes we had made using dowels previously. We tried to put in new dowels to lock the two pieces together for the casting, but we couldn’t remove enough silicon that filled up the holes that were meant to be for the dowels. Giang and Nery decided to align the pieces back together and begin casting with polyurethane. The part B mixture was running low but we decided to use it anyway, which may not have been a good decision because there wasn’t quite enough mixture to fill the mold. Additionally, we couldn’t secure the two pieces of the mold together as tightly as we had hoped, so some of the casting mixture leaked out of the mold. In hindsight, we should have used tape or other materials to make sure the mold was secure before pouring the casting material in. Additionally, we were not able to take any photos of these errors since both Nery and Giang had the polyurethane mixture all over their hands.
After 24 hours, Giang went back to remove the cast from the 2-piece mold. The mold itself was easily released from the plastic cup, but the two pieces of the mold were much harder to separate from each other due to the fact that the casting mixture was leaking everywhere. Giang used a small flat file to remove the excess polyurethane and expose the cast, but found that the top part of the cast (the section that was furthest from air exposure) was still wet. Due to time constraints and the lack of materials, Giang placed the mold back together and will allow the cast more time to hopefully set.
1-Piece Mold
The one piece mold seemed to be a bit more straightforward because both the mold and the cast could be made in one sitting.
As a group, we decided to create a mold of our original vein finder design, which would be similar to the casing of an Apple Watch. Nery had already created the CAD design for the watch for our Design Review 2, so all we had to do was 3D print.
Because the design was hollow on the inside and had two openings on each side, in order for both the mold and cast to be correct, Zari stuffed the holes with clay.
Zari created our mold with Alja-Safe Alginate and set it to set. One thing that we did notice was that the area in which our class kept our materials probably wasn’t the best place to keep them because it was a bit humid.
Another thing that went wrong during the mold is that a few minutes after a few minutes our 3D print floated to the top. Because more clay was also added unintentionally to one side compared to the other, it floated at an angle. In the future, it would make more sense to glue it down to the bottom of the cup, not use a hollow mold, or just to now use as much of the Alginate to create the mold.
When Zari returned back to the mold two days later, the mold was slightly moist but it had a bunch of water collected at the bottom. In hindsight, it probably would have been better to use tape instead of clay because the clay attached to the mold and it was very hard to get out.
After the 3D print was taking out of the mold and *most* of the clay was removed, Polyurethane was then used to create the cast. You can clearly see here that one side floated more than the other because when looking at it from an overhead perspective, you can only see the handles on one side.
Although Zari measured both Part A and Part B in 1:1 proportions, we still think that the cast was slightly more pink than it should have been. Also, because so much water had evaporated from the mold itself, the mold did not fit snugly into the cup, so some of the cast spilled over on the sides of the mold.
The cast was left in the mold for three days, but when Giang and Nery went to take the cast out of the mold, it was still very wet and crumbly. Because of time constraints and the fact that the class had run out of the Polyurethane and Alginate to start over, we had to just stick with this cast as our final product.
We personally think that keeping our mold and cast near the sink unattended may have caused something to happen to it but we do not know for sure.