Hello everyone. As of today, FRC team 2815 has created our own in-house Note. This process started the week of kickoff and lasted until today because of modeling, testing, improving, and wait times. Me and a few others on our team originally started this project because we only had 1 Note and needed more but couldn’t get them. Now, we no longer need this but we still have it for incase we need spares or just want them for testing.
Testing and Materials
To begin with, we decided we were going to make the Note using expanding/spray foam since it would be able to fill a mold and be able to have similar properties to the actual Note. We tested different types of expanding foam to find one that was both flexible and durable. we ended up using the GREAT STUFF flexible spray foam to get the flexibility we needed. This foam is not the most durable though and breaks easily when it is pulled on. To fix this issue and make the Note have a similar rubber texture to what the real note has, we used Plasti Dip. This part we haven’t done yet with our larger Note or with this exact kind but we tested it before on a 1/4 scale version and it helped fix these issues. Of course, before any of this happened we needed to make a mold. For this, I used Onshape to create the models and test them which you can see here. We used 2 of each type of piece to create the 8 part mold that was needed to make the Note. We 3D printed each of these 8 pieces and each one took close to a day on the settings we had so if you plan to do this yourself, it will take more than a week for the full process if you only use one printer. We originally tested on a smaller mold that gave us the values we needed for our larger mold and other valuable information like that you need about 4 kilos of filament and a can of spray foam (2 is better as i mention later). One thing we learned was that the spray foam requires air to cure which you couldn’t have in this mold. To solve this issue we sprayed water in to allow for it to cure. We sprayed water on both the inside of the mold and on the foam after we put it in to allow for better curing. We also needed a way to make the Note not stick to our mold. We did this by putting black lithium grease on the entire inside of the mold. We also learned that the spray foam gives off a smell while it is curing so there is no need to open the mold to check if it cured, you can just smell it and if there is no smell, it is fully cured. This is everything we had to buy to get the mold to work and the basic ideas we learned through our testing. To keep the mold together, we used 8 1in bolts on the sides, 8 3.5in bolts to keep the top and bottom together, 32 washers to put on both sides of every bolt, and of course, 1 nut for every bolt. The process we used to put the foam into the mold takes multiple people.
Creation process
We first assembled the top and bottom of the mold and put the 8 3.5in bolts in the bottom pieces so we could set the top one into the bolts to line everything up. We then put down the grease followed by spraying a layer of water on top. We then had one person spray the foam into the top pieces and another person spray into the bottom. We then sprayed water on top of the foam and put the two halves together. We then bolted the 3.5in bolts down to hold the 2 halves together and squeeze out any excess foam. We then cleaned off the outside of the mold and left the mold to sit for about 2 days before opening it. To open it, we went very slow to not break the Note and removed the mold in 8ths.
Results
We then had a foam Note that was the exact size of the real Note. Of course, the fabricated Note had grease on it when it came out so you can try to clean that off if you feel like it. Next, we plan to use the plasti dip to make the Note stronger and more rubbery like the original. If anyone is curious, the fabricated Note is about 1/2 the weight of the original but everything else is basically identical. If anyone else wants to do this, feel free as i have linked everything we used except the grease because i don’t know the exact one we used. If you have any questions, feel free to ask.
I wish everyone the best of luck with their season builds and hope to see some amazing feats of engineering during this season.
