Prints remain sticky

Hi everyone!

I’m having strange issues with most of my prints. I’ve gotten quite good with printing, now having over 90% success rate with the prints, but the post curing seems to be quite problematic.

Most of my prints remain somewhat sticky/tacky after post processing. Some more than others, even though they might have been exactly similar prints, right after each other (literally just pressing “print” again after removing the previous print from the build plate).

I’m using Peopoly NEX clear, Photocentric Hard black and Photocentric Flex clear resins and i’m having similar issues with every resin.

Playing with laser power between 52-58 as needed and since the prints are over 90% succesful without layer lines etc. I don’t think there would be an issue before the post processing.

For post processing, I’ve tried almost everything with different combinations. If i would list every workflow separately, this message would be very, very long, so i’ll just settle to list the ways I’ve tried.

Rinsing with IPA, Ethanol, Water, Distilled water, Water with mild detergent, Water with strong detergent.
Washing with paint brush with all the solutions above.
Ultrasonic cleaner, 2min, 5min and 10min with the solutions above.

Curing (in a bucket with aluminium foil on the inner surfaces) with 50W 405nm UV light, 100W 405nm UV light, 100W 365nm UV light and 100W 385nm UV light and combinations of the mentioned (prints seem to get quite hot when exposed with 300W of UV light… xD) and curing in the sunlight. Everything between 10min and 8hrs I’ve tried. Tried also curing the parts submerged in water and once i filled the bucket with argon. The argon didn’t seem to make a difference.
And by the way, the mentioned wavelenghts are correct, they have been measured by the Finnish radiation authorities for eye safe exposure distances and times (different topic, but I’m in kinda deep in the UV light industry)

Anyway, still the prints remain sticky!

Best results so far i got by 5min ultrasonic wash in ethanol, then brushing with IPA, drying, 2h post cure with 100W 405nm UV. The print was still sticky at this point, but another 5min in ultrasonic (ethanol), IPA rinse and then washing with warm water + soap and another 30min in UV.

There must be a more simple workflow? Or are resin prints just always sticky?

Anyone else having similar problems? What’s your workflow? Please help me out with this one!

I’ve also tried lowering the UV power (to about 30W with 405nm) since i was wondering if i had too powerful lamps, but it didn’t make a difference either…

The resins are stored in a dark, cool closet when not in use and this problem has occurred since my first prints so at least then the resins weren’t too outdated. Would try other resins, but availability is kinda bad at the moment…

At the very least I can confirm that the print probably shouldn’t be sticky at that point. Normally after a good clean mine don’t seem sticky or glossy, even before post cure.

That’s with just IPA (100% ipa). For the sake of cutting down variables it might be worth trying with some fresh IPA and nothing else. Hopefully peopoly has some other ideas that might help.

Hey Sampsa

I´ve got the same problem. I use standart peopoly grey/blue resin most of the time and use a laser power of 60
My workflow is washing with IPA, cleaning with tab water and in my curing bucket with the peopoly uv lamp for a few hours.

after that they are always sticky but when they lay around for a few days in indirectly sunlight they get solid.

I hope we can find a way for this problem

Use at least 90% ethanol for cleaning. If the resin is very sticky and adheres to the model, you can infiltrate the model first, and then gently brush the model with a brush or use ultrasonic cleaning. After cleaning, blow dry the model immediately, and then complete the second ultraviolet curing.