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.
After printing, place the assembly in a water bath. After a few hours (depending on the water temperature, agitation, etc.), remove the assembly and carefully attempt to rotate the gears. If they do not rotate, return the assembly to the water bath for another few hours then try again. If they do rotate, rotate the gears enough to expose the PVA trapped between the gears, the return to the water bath. Repeat until all PVA is removed. Also, changing the water frequently will assist in expediting the PVA dissolve process.
Finally, I posted a video showing the water bath I used; a printed circuit board etching tank with an air agitator and heater. The agitator generates bubbles that better penetrate the tight areas between the gears, supports, etc., that assist in dissolving the PVA. I run the tank heater at 28 degrees celsius (approximately 82.4 degrees centigrade) which also assists in dissolving the PVA.