From time to time and for various reasons, I revisit older designs. This thing, the PLA / PVA Spring Motor Demonstrator, is a revisit and redesign of my original PLA Spring Motor Demonstrator.

Yes, the redesigned version is smaller, and is only printed in one color, however, the most important feature is that it was printed in place and fully assembled, using PLA for the structure and water soluble PVA for supports. When printing is complete, just throw it into a water bath for a few hours and it's ready to run, no assembly required!

While I had heard of dual extrusion printers before, I had never heard of PVA until I saw the release of the Ultimaker 3 (I must lead a "sheltered" 3D printing life...). After many discussions with the wife, and the onset of Christmas, I received an Ultimaker 3 Extended which included the PVA filament. I am not a fan of PLA "supports" as they tend to leave a rough surface at the point of contact with the component being printed. However, the Cura slicer and Ultimaker have solved this with the use of PVA supports, as the point of contact surfaces are remarkably smooth leaving no visual hint that support was used.

The first photograph shows from left to right, the original PLA Spring Motor Demonstrator, the redesigned PLA / PVA Spring Motor Demonstrator encased in PVA, and the PLA / PVA Spring Motor Demonstrator after it's water bath.

Video of prototype is here: https://www.youtube.com/watch?v=6w0yKowwVEk.

Video of prototype in the water bath is here: https://www.youtube.com/watch?v=jeWeDsPPoC8. Note I'm using a printed circuit board etching tank with a bubbler and heater to expedite the PVA dissolve.

Designed using Fusion 360, sliced using Cura, and printed in PLA / PVA on an Ultimaker 3 Extended.