There’s a lot to like about resin 3D printing. Detail, smooth surfaces, and the simplicity of a resin printer compared with an FDM. There are also downsides to resin printing, including the toxic waste generated. What’s one to do with all that resin-tainted alcohol left over from curing prints?
Why not send it through the filtering apparatus made at home to prepare it for reuse? [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. The idea is not hampered by its simplicity; the photopolymerization method used in printing removes the unpolymerized residue from the alcohol rinse.
[Involute] I did some preliminary experiments to see what used IPA would do when exposed to ultraviolet light. The video below shows the results — the unreacted resin quickly clumps, making it easy to filter out of the IPA. The actual implementation of this process is a little more complicated. To achieve the desired cross-linking effect, the resin must be pumped through UV LEDs wrapped around a clear vinyl tube. 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. It’s also a bad idea to flush resin-tainted ethanol down the toilet. Something like this will not only help resin printers save money but also make their process greener. Kudos to [Involute] This is what I’m saying.