On the support page for the flexible resin there is a small paragraph on finishing when using this material:
“If your part still feels tacky after washing in IPA, try post-curing it underwater. Find a clear glass container, place your part in the container, and cover it with water. Leave the container out in the sun until it no longer feels tacky to the touch.”
Post curing underwater? I haven’t seen this being recommended before. Anyone know why this is a benefit? Is it recommended for other resins as well?
“The reason the print is left feeling sticky is due to the outer surface not fully curing. This is because of the presence of oxygen, which stops the curing of the outer layer. By placing the the print in water and exposing it to UV light, you are limiting the amount of oxygen diffusing into the uncured resin, which allows it to fully cure. The water is essentially acting as an oxygen barrier.”
I’m getting ready to try my first print with Flexible resin. This post-curing trick will work great with my budget UV curing jar. UV LEDs on the outside of a clear acrylic jar. Fill it with water, no problem. Perfect, no?
I tried post-curing the black resin under water over the past week – it works amazingly well! I’m not sure why this isn’t more prevalent in the Formlabs documentation.
So… for the black, it actually turns the print grey. You have to use mineral spirits to get it back to black (if anyone is really picky about the color). It also seems to make the prints a lot more chalky versus the standard cure. To me, I like the chalky behavior better – somewhat ironically, they feel sturdier than the non-water’d parts.
(For the life of me, I couldn’t find out how to start a new topic on the forum… so decided to reply to this related one)
We’ve been having great results with the underwater curing, but of course we end up with quite a lot of contaminated water. At least, I assume it’s pretty unhealthy stuff that shouldn’t just go down the drain. Does anyone have a great idea for how to deal with this responsibly?
I suspect it might be ok to pour it down the drain, as the material is fully cured, and it ought to get filtered out. On the other hand, I have been reluctant to do this, as it just feels wrong, and it being summer, I just leave the water outside (somewhere where animals won’t get to it - my printer is in a basement and I have a really handy shaft outside the window with a grate over it) and it evaporates leaving a residue behind; you can pour the water into a plastic container which you can later throw away with normal rubbish which frees up the original curing container; this I rinse with a little alcohol before refilling with water.
I 've noticed you can cure quite a lot with just one jar of water - I just use it until it is so cloudy it feels like UV couldn’t be penetrating anymore. So I’ve been saving up a few jars of ‘formlabs water’ and labeled it and then I bring them along on my trip to the recycling centre every few months. I assume they have a better chance of taking care of it responsibly.
Liquid resin should never be poured down the drain, and cured resin could potentially cause clogs. Straining the water and throwing away the cured resin as normal waste would be my recommended approach.
I have not tried the water cure method yet, as my parts are coming out hard enough after IPA + Water rinse and then letting them sit in a bright room for a day or so…
I also found i did not need to soak the parts long at all… Slosh around in the container of 91% IPA for 2mins, let sit for another 2, then shake again for 30 seconds. Wash parts under water and use a tooth brush with fine bristles to brush the part.
Have been having really good success with this method.
Might depend on your tap water, I just recently tried that method, and we have very hard water. The print started very clearly leeching calcium out of the water, and getting grey spots all over the surface. At least with my tap water, just UV curing without water is the better option.