How Water Soluble MakerBot Printing Works and Why It's Awesome

By Wesley Fenlon

Are you ready to print objects with moving parts using dual extruders in the new Makerbot Replicator?

3D printing fans have a long list of things to be excited about in the MakerBot Replicator. It offers triple the footprint of the previous generation Thing-O-Matic, two-color printing, onboard controls, and comes pre-assembled so you can get right to business without hours of setup. Now here's the best thing about that two-color printing: with dual extrusion, the Replicator can print with two completely different plastics at the same time. Printing with two colors is a perk: printing with a water soluble plastic and a base plastic simultaneously is a game-changer.

MakerBot Thingiverse user Tony Buser gives us a taste of the future with a dissolvable support gearbox made from two types of plastic, PLA and PVA. The PVA plastic melts away after a long, hot bath, leaving enough empty space inside the model for the gears to turn freely.

Buser noted on the gear's Thingiverse page that he had trouble getting ABS and PVA plastic to stick together, but found his solution in the PLA plastic used in the final design. That's a lot of acronyms to process at once, so let's go through them in turn. PLA, or polylactic acid, is a thermoplastic made from renewable resources like corn starch. PLA has a whole page on MakerBot's wiki. It's a solid plastic used for printing and serves as the basic material in the gear build.

PVA, or polyvinyl alcohol, is a water-soluble thermoplastic with a lower melting point than PLA. Obviously PVA can be very useful when combined with PLA, as it can be melted away after printing to create gaps for insertable objects (or moving gears) in MakerBot products.

The third plastic, ABS (acrylonitrile butadiene)--which wasn't used in the gear build--is an alternative to polylactic acid. It's another popular thermoplastic used in MakerBot printing, and the material is even compared to PLA on the wiki:

PLA is a solid; ABS is a gelled liquid (Spacexula)

  • When you heat ABS it slowly transitions from a gel to a liquid: does not go through a state change.
  • PLA on the other hand is like frozen water, moving straight from solid to liquid in one step (extremely energy intensive)
  • ABS (not requiring a phase change) becomes more liquid further it travels down the barrel.
  • Because there is no phase change, ABS doesn't suck heat energy out of the nozzle as aggressively.
  • With PLA, the risk of the phase change cooling the nozzle allows greater risk of clogging.

Buser used a dual-extruder setup on a Thing-O-Matic to print his gearbox and a cool Hilbert cube. The dual-extruder Replicator should be just as adept at printing these sorts of objects, but on a much bigger scale. Complex machines, here we come!

Photos via Tony Buser's Flickr