There’s a lot to like about resin 3D printing. The smooth finish of the surface, the simplicity of the printer compared to FDM. Resin printing has its downsides. Not least is the toxic waste it generates. What’s one to do with all that resin-tainted alcohol left over from curing prints?
What about putting it through a home-made filtering apparatus? [Involute] likens this process to dialysis, and while we see the similarities, what’s going on here is a lot simpler than the process used to filter wastes from the blood in patients with failing kidneys — there are no semipermeable membranes used here. It’s not that the idea is flawed by its simplicity. Instead, it removes the resin unpolymerized from the isopropyl ethanol rinse using the same process as used for printing.
[Involute] I did some experiments to see how used IPA would react when exposed UV light. The video below shows the results — the unreacted resin quickly clumps, making it easy to filter out of the IPA. It was more difficult to turn this into a real process. A pump is needed to push the resin through the UV LED-wrapped vinyl tubing where the cross-linking takes place. From there the plastic-IPA mixture passes through two filters, 5 microns followed by 0.5 microns, after which it’s ready for reuse. [Involute] also added a timer to control the pump, making this a walk-away process — although since IPA is pretty flammable, we’d probably stay close by.
At more than seven times the price of gasoline, 99% IPA isn’t something you want to be throwing away. Resin-tainted ethanol should not be flushed down the drain. Something like this will not only save resin printers money but also make the entire process greener. Kudos to [Involute] For that.