Build Log: A better way to manufacture propellers
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Hello Reader, Welcome back to The Build Log! Since we are planning a new very exciting mission with our autonomous submarine (more info soon), we want to make it as reliable as we possibly can. One of the things we thought would be very useful is to upgrade our propellers. In the original design of the CPS A we have been using resin propellers, which came out to be quite brittle. They are much better than FDM printed propellers in terms of surface finish, but unfortunately they are not as strong. Since our autonomous submarine carries our $3000 DVL and other expensive hardware, we really wanted to make sure that it doesn't get lost just because the propellers give in. So, we started searching for ways to manufacture metal propellers. The most usual way to do it is CNC machining - out of aluminum. It can theoretically be done with a desktop CNC machine (we recently got a Makera Z1), but it will probably not be entirely possible to get the shape 100% right. For that, a more advanced 5 axis CNC machine is needed. See the video below for how propellers like that are usually manufactured: Unfortunately, we don't have access to a machine like that. But there's an easier way. For some time now, online services like JLC3DP or PCBWay have offered 3D printing services out of metal. You can usually choose between titanium and 316 stainless steel as the 3D printing material. Both materials should be suitable for underwater use. We decided to go for titanium - it's theoretically not as strong as steel, but it's much less dense. Here are the propellers we ordered: Because of how the metal 3D printing technology works, the propellers didn't turn out to be super smooth. Fortunately, it was much easier to make them smooth than FDM 3D printed propellers. We just needed to use a rotary tool with a sanding bit. After about 10 minutes of sanding per propeller, the blades started looking much better: It proved to be much more robust than the resin printed propellers we have used before. They will be able to cut through seaweeds, and won't chip on tiny rocks. If you want to build an underwater project, the easiest way to get involved is to build the entire CPS 3 drone with our DIY Kit -> now available!
You don't have to buy any components separately, because they're all in the one box delivered to you. Cheers, Piotrek, CPSdrone PS: You can access all of the previous releases of the newsletter here. |
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