We recently sat down with Joe Frost, an engineer at the University of Michigan, who was part of the university's Human-Powered Submarine Team, a student-run team focused on designing, building, and testing underwater vehicles solely powered by one person. We wanted to learn more about this interesting project and how they used 3D printing to help manufacture the human-powered submarine and how Essentium's Copolyester PCTG+ filament played a part in the project.
Joe Frost: The project was a human-powered submarine. Think a torpedo powered by bicycle pedals. A pilot sits in the submarine and uses the pedals to move it forward. I was the design lead, I took care of anything that moves on the submarine, like the control services or the chain drive.
3D printing was an easy choice for us as it was the fastest and easiest method to produce the hydrofoil profiles of the control surfaces.
3D printing allowed us to change the shape and size of the control surfaces and test their performance in roughly 15 hours--and 14 hours of those were spent actually printing the surfaces. This is compared to 30-40 hours of labor that the process used to require.
In the past, we used molding processes and urethane foam to make the control surfaces. Producing a new mold involved hours of CNC programming, work setup, machining, plus sanding and priming before we could even start the molding process.
I was looking for ways to help speed up our processes and for a material that was impact resistant, stiff and able to hold its shape underwater. We do most of our testing in chlorinated pools and couldn't use materials that would break down when exposed to water and pool chemicals. The rudders themselves take a beating during testing when the submarine hits the bottom of the pool, so we needed something that wasn't brittle and could absorb multiple impacts without fracturing. Essentium's Copolyester PCTG+ filament was perfect for the job.
We looked into other commonly available 3D printing filaments such as ABS, PLA, and Nylon, however, none of them could meet the impact resistance requirements while being repeatedly subjected to underwater conditions. Cast urethane works well, but any deformation to the produced parts resulted in significant fracturing.
The material was initially recommended to me by a colleague at the University of Michigan that was also using PCTG+ for a project. He showed me how to utilize the material for end use parts and I was convinced it was the right choice.
I used PCTG to manufacture components for the submarine control system and control surfaces, like the rudders and the components inside the sub that move them.
I never had any problems associated with the filament. Build plate adhesion was fantastic to the point where it was difficult to pull parts off of the printer.
The most significant advantage Essentium's PCTG+ brought the team was that it allowed people without machine training to produce end use components. We are always bringing new members on and training them in conventional manufacturing techniques, however, to produce any parts with complex geometries requires CNC training, which involves months of experience and training. PCTG allows new members to produce submarine components as soon as they can design them.
To learn more about the University of Michigan's Human-Powered Submarine Team, click here.
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