Sticky & Slimy prints?

[aronai]

I'm very new to SLA printing (and all 3D printing really), and I've been trying various resins.

One thing they all seem to have in common is that even after curing for 10-15 minutes under a 6w (marketed as effectively 60w) UV light at close range on a turntable, in a UV-reflective grow tent, they remain sort of 'sticky'. Enough so to gain textured fingerprints if squeezed slightly. Is that normal? Is that indicative of the parts not actually being cured, or...? They don't appear to be actually wet even though they feel sort of wet.

Also, after washing (I've tried 99% IPA manually and Mean Green in an ultrasonic for 8 minutes on different prints), it seems like the prints always have some slick substance on them, which I assume is resin (if it was one of the cleaning agents I assume it would rapidly evaporate and not be so 'slick')... so what am I doing wrong?

[fromFDMtoSLA]

what resin do you use? and show us your UV light (may be it's not 405nm).
how is your processing: printing -> washing (IPA) -> curing ?
and - please - show us your exposure times from the slicer

[aronai]

what resin do you use? and show us your UV light (may be it's not 405nm).
how is your processing: printing -> washing (IPA) -> curing ?
and - please - show us your exposure times from the slicer

I've tried various resins. From the Elegoo clear/translucent, the Anycubic Eco translucent, Anycubic Eco blue translucent, "SainSmart Rapid UV 405nm 3D Printer Resin" grey, going to try Anycubic grey now.

The light I'm using is here: Amazon Link
It claims to be a 405nm light.

In the slicer, I'm not at my PC right now, but I've just been using 70s base and 12s for each layer after for every resin I've tried. Seems to be within what's suggested on the sides of the bottle.

For my process, I've tried different things. What I'm doing right now is just taking the print off the plate with a plastic tool onto some paper towels, rinsing the part with IPA into a plastic waste container to get a lot of it off, then I've tried both using Mean Green in an ultrasonic cleaner for 8 minutes, or manually swishing the part in an IPA container (not on the same part, I've tried those things on different parts). Then, I cut the supports off, and then stick it into a UV reflective grow tent with that UV light hung from the ceiling (at about a 20 degree angle from the direction it's aimed), aimed at a solar powered rotating stand thing, and leaving it for 5-10 minutes.

[Boonie]

what resin do you use? and show us your UV light (may be it's not 405nm).
how is your processing: printing -> washing (IPA) -> curing ?
and - please - show us your exposure times from the slicer

I've tried various resins. From the Elegoo clear/translucent, the Anycubic Eco translucent, Anycubic Eco blue translucent, "SainSmart Rapid UV 405nm 3D Printer Resin" grey, going to try Anycubic grey now.

The light I'm using is here: Amazon Link
It claims to be a 405nm light.

In the slicer, I'm not at my PC right now, but I've just been using 70s base and 12s for each layer after for every resin I've tried. Seems to be within what's suggested on the sides of the bottle.

For my process, I've tried different things. What I'm doing right now is just taking the print off the plate with a plastic tool onto some paper towels, rinsing the part with IPA into a plastic waste container to get a lot of it off, then I've tried both using Mean Green in an ultrasonic cleaner for 8 minutes, or manually swishing the part in an IPA container (not on the same part, I've tried those things on different parts). Then, I cut the supports off, and then stick it into a UV reflective grow tent with that UV light hung from the ceiling (at about a 20 degree angle from the direction it's aimed), aimed at a solar powered rotating stand thing, and leaving it for 5-10 minutes.

My penny worth........
I would guess the UV is not 405! I bought a strip that claimed to be but was not. I now use a finger-nail box but have to give it a lot more time - like an hour - and then I leave the model on the window sill for a couple of days before it loses that sticky felling. I have read others quoting 20 mins but if it is for a component that needs real hard surfaces, I leave it days before using as it seems to have a softness to it for a long time. I use elegoo grey resin.

[cliffyk]

I have that same UV lamp--checked it with a cheap spectrometer having a claimed ±5 nm accuracy, the lamp was spot on, just kissing the "North" send of the 400 nm scale marker.  I was a bit surprised.  I have found that a good 2-3 minuter wash-down with 70% IP; aka "rubbing" alcohol ($2.00/qt at Dollar General, and a bit less at Walmart); then a quick wash with HOT water and dish-washing liquid before the post-process UV session; results in much less sticky prints.

If I am in a rush to paint, I use a cheap hair dryer ($10, also from DG) to knock any remaining moisture/alcohol from the item--I was getting a lot of fish eyes with rattle-can enamel before i used SWMBO's¹ hair dryer to dry 'em out--she was not happy about that²--and made me buy my own...

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¹ - She Who Must Be Obeyed
² - But not as bad as when I used the kitchen oven to cure powder coating.

[zemerick]

Simple solution, as long as you are not using water washable. ALWAYS post-cure while submerged under water. Prints should only take a few minutes to cure. Anything more than that, and something is going wrong.

In this case, specifically it's oxygen inhibiting the curing process. Submerging under water blocks the oxygen and allows the resin to quickly and thoroughly cure.

And yes, slimey means it still has liquid resin. Sticky means not fully cured. It should be a smooth, hard, matte surface when all done.