Elastic 50A Sticky

I have been having issues with parts printed in Elastic 50A remaining tacky – sticky to the touch. Is this normal?

I use TPM as my washing solvent and rinse with water after. This is done using two Form Wash units, one with TPM and another with water (and 1 tsp of dish soap, as recommended by Formlabs). Both water and TPM are practically fresh.
https://support.formlabs.com/s/article/Washing-prints-with-TPM?language=en_US#tpm-resins

Following the guidelines here: https://support.formlabs.com/s/article/Form-Wash-Time-Settings?language=en_US
I’m washing as I would with IPA, meaning: “10 minutes + 10 minutes”
In my case, 10mins in TPM, quick 2 min rinse in water, then back to TPM for the final 10 mins.

The first article notes a side-affect for Elastic 50A washed in TPM: “Resin remains waxy when printed at any layer thickness. and requires post-cure. Post-curing removes the waxiness.”

However the recommended post-cure of 20 mins at 60 C in the Form Cure did not help.
https://support.formlabs.com/s/article/Form-Cure-Time-and-Temperature-Settings?language=en_US

I also tried the method “Post-curing Underwater”, submerging the part in a glass jar of water and placing in the Form Cure. This too, did not remove the tacky feeling.

Have I missed something? Hoping someone can help. The only reason I’m leading myself to believe the finish should not be sticky to touch, is the raft is not and has no tacky finish. Thanks in advance.

Hi

We use a lot of elastic, and we always post cure under water. Just a large lab beaker and tap water in the UV box. The stickiness goes away totally in a couple of minutes.
It is hard to see why this wouldn’t work for you. I wonder if you are using a container that is blocking the UV?

The only difference in process to what you describe is we use IPA not TPM, but I suspect that is not important.

Thanks Andrew.

Blocking UV light could be a possible explanation. I’ve been using a glass preservative jar (simply due to having a lid). I’ll test another vessel today.

From your experience, I had a couple questions if you don’t mind:

  • Do you let your parts dry off (from IPA wash) before placing in water for cure? And do you cure with heat?

  • Have you ever over-washed parts and it resulted in sticky parts?

Thanks again.

Hi
We use a form wash, and run a 10minute cycle with IPA, then a quick rinse under the tap, into a beaker with warm tap water, then we have a Peopoly UV chamber which takes about 2-3 minute to cure. I’ve never seen a problem with over-washing.
Good luck, I hope that helps!
Andrew

Thanks Andrew! Appreciate your help.

Similarly to the others, I always cure under water in a glass container and the end result is no longer tacky.

You need to make sure all air bubbles are gone otherwise some spots will remain tacky.

Thanks Leon.

I’ve since put the same part that was ‘tacky’ through another 10 mins in TPM with the Form Wash and 10 min cycle in water with another Form Wash. Then water cured for 10 in the Form Cure (no heat). It seems to have lost the ‘tack’ – still feels ever-so-slightly sticky, but I’m now thinking the TPM may not wash the excess resin quite as well as IPA.

Have you had experience with sticky parts and re-washing before curing as a process (with IPA)?

TPM evaporates extremely slowly. I used to use DPM and would follow with a quick IPA rinse to accelerate drying. Can’t say I did much elastic or flexible back when I was trying DPM though.

Make sure your parts are thoroughly dry, it’s possible that if they aren’t it’ll mess with your post cure step.

Thanks for your help Leon, I’ll make sure it’s 100% dry before curing. Do you only water cure? And with heat? The Form Wash cure time article suggests 20 mins at 60 C. Trying to work out whether the water cure is extra or replaces those 20 mins without being submerged in water.

I only do one post cure following instructions but submerged under water with no air bubbles.

Just thought I’d update this thread – after having left the part to dry after washing, I went straight to water curing for 20 mins at 60 C. Previously I’d cured without water for 20 mins at 60 C first and followed by another 20 mins at 60 C submerged in a jar of water.

2 parts have now followed this process and come out perfect.

Thanks again Andrew & Leon for your help. I hope this thread can be helpful for anyone else with a similar issue.