Sticky parts toxic?


I am new to Formlabs printing. I got a few parts from someone else, that are printed in the Form 2 printer with Tough V4. But somehow the parts are sticky on the surface. Is it safe to tough the parts without gloves? Is this toxic? Furthermore, is there a way to remove the stickyness from the parts?


The parts were washed improperly. Ether in polluted IPA or were sunk in it for less time than were supposed to. Usually the first case due to cheaper production.
Touching it with hands may cause some skin irritation. But it will not be the case considering the amount that’s left on it. You ought to have very sensitive skin for this to happen.
To remove the stickiness you should wash the part properly using solvents. Preferably Isopropyl alcohol. (Acetone and strong acids might ruin the print) After washing the part stick it in UV light (Ether sunlight or some sort of device) for 1 to 2 hours and you’re golden.
If you don’t own any alcohol based solvents you might as well try doing the UV part without washing.
*Note sunlight ought to be direct, since glass blocks UV radiation.

I would soak it in IPA for like 5 minutes, and then rinse it in room temp water. Then submerge it in a container of water and let it cure for like 10 minutes and dry it off after that.
Sometimes the outside of a print doesn’t cure as well, oxygen inhibits curing so curing it in water for a little bit blocks oxygen and can get the outside cured.

When I do the soak in the IPA I use a little brush to clean the surface off with in the IPA. I then do the second soak in clean IPA and blow dry off before curing. With this process I have way better outcomes and the parts are nowhere near as sticky as they were with just soaking them.



the stickiness might WEAR off if its handled a lot over time- but it won’t go away entirely unless you can isolate the part from oxygen.

if you just place the part in a large tray of water deep enough to submerge the entire thing, with an open top wide enough for sunlight to hit the part without going thru the glass, for an hour or so- the stickiness should be eliminated entirely.

If the part is thick enough to be not very transparent- or printed in a pigmented resin, then be sure to turn the part over a few times in the water to ensure ever bit of its surface gets illuminated.

Don’t stick it out in the sun for an hour, that will heat it up and can warp it. You don’t need much time to get the outside cured, just 5-10 minutes can do it just fine

Sculptingman, curing parts under water is definitely not required. Formlabs is filled with thousands of printed parts that are tack free and we never use underwater curing (except in some testing). Proper washing with clean enough IPA is usually the main thing people get wrong in getting to a tack free surface. The general purpose resins can even reach a tack free surface without post cure, but post curing properly is required for the best surface.

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that is certainly true- generally, I do not water cure most parts now that we have the curebox- as long as they are fresh from the printer a sufficient flux of UV under heat will eliminate the stickiness if they have been cleaned properly.

But when parts have not been properly cleaned, and the layer of uncured resin has been around for a while… when the parts are weeks old and still sticky… I usually find a water exposure will force the resin to cure enough to eliminate tack. And I find that after days or weeks of being sticky they simply are nearly impossible to entirely clean. The oxygen inhibited surface is not liquid, and will not wash off-

Understand that I am talking about parts that HAVE been exposed to daylight for days and are STILL tacky.

Its kinda like when folks make fiberglass parts using polyester laminating resin… and don’t top it with a finishing resin. When we get parts like that in shop we have to wax them so that the surface will fully polymerize.

I suppose you could do the same with UV exposure in a 100% nitrogen environment.
But having been getting prints made from service bureaus for 20 years, we have seen every imaginable combination of parts not being exposed or finished properly.

I would be interested in Formlab’s take on how long AFTER a part has been printed that post curing will still optimize material properties.

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I tried to put the parts in a bucket filled with water and placed them in the sun for areound 45 min. Thereafter I dryed them by sunlight. I think that this did help to remove a bit of the stickyness (good advice).

I noticed that there were/are some tiny wet looking (glittering) sticky points on small gabs or holes on the part, that are really hard to wipe away with tissues. What are these left wet looking spots? Is this resin, polymer, some kind of carriersubstance for the polymere? It seems that this substance does not get dry/hard, even with UV light.

Yes, for parts that have been left out for a while, it is harder to remove the tackiness. I don’t think we’ve studied that much. We are focused on making it as easy as possible to post process them correctly the first time through.

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I’ve had success with running them back threw the wash and cure station a second time. usually after I file off the burrs left from the supports I rewash the parts it soften the surface just enough to clear off the sanding marks.

I had same issue, new IPA fixed it. I was being cheap on the IPA.

make sure that you don’t have any water on the print before you put it out to cure, spots of water will cause the area underneath to start curing already and can cause an uneven finish.
What I do for everything is:
Turn down the lights
Soak in IPA container for 10 minutes, rinse in clean IPA
Rinse off in room-temp water, fill a container of water enough to cover the part, place the part in the water and put in curing box for 5 minutes.
dry off carefully as much as I can with paper towel, put back in curing box for 45 minutes.
And that always works fine with a very nice non sticky finish.
If the IPA isn’t clean enough, then you’ll get bits off stuff and residue on the print.

if you see Glossy spots, that is likely simply where the liquid resin was most liquid when it cured… a puddle of uncured resin will have surface tension that makes the surface very glossy- and as the UV cures it, that glossiness is cured in… this is exactly how Gloss paints achieve a glossy surface.

The trick is to CHECK if these glossy spots are cured or still tacky— generally, tacky resin is NOT glossy…touching it leaves the surface looking like a meringue, microscopically… so take a very fine pointy tool and Touch the glossy spots to see if they are still soft. Chances are, you will find them cured.

IF they are not- if they are puddles of semicured resin that will not cure under water- then this resin is oxidized to the point that it will no longer cure no matter what you do… the best you can do is Literally to SCRAPE this resin off the surface with the edge of a xacto blade. ( drag the blade sidewise across the surface to literally PLANE the resin off, with the blade edge tangent to the surface. )

Sorry to tell you but this is really the only thing you can do with resin that is fully oxidized.

There is a reason why your resin cartridges have an expiration date, and why that date gets shorter once you open the cartridge to air.
After a while the resin loses the ability to fully cure… this is why it is critical to clean and cure printed parts as soon as possible after printing.

beyond that- any residual tackiness you can try and remove with a more aggressive solvent. We use acetone- you want to use a solvent that will flash off fast enough to not soak into the hard resin and damage its structure or cause swelling.

Another final trick you can use is to dust the part with talc- this will literally do nothing but clog the tacky molecules with particles of talc- like rolling chewed chewing gum in flour…
But it will make the surface feel less sticky because there will be a layer of talc molecules coating the outside-

( this is the same thing they do to latex gloves and balloons that are still tacky on the oxygen exposed side so that when they invert them, the latex will not bond with itself… )

Soft toothbrush and brand new IPA 99%, get as much liquid resin off straight away. Soak for 10 mins in used IPA, soak for 5 more in pretty new IPA 99%, final slosh in fresh IPA and airline dry. Absolutely no more than 20 minutes in IPA total, or they might go soft, especially thin walled items. I use a collection of plastic take away food trays as wash basins, easy to keep clean, easy to replace.

I’ve managed to get an old 3D Systems temperature controlled oven and am rigging some UV lights in it so hopefully should have a fully operational curing system soon; it will be interesting to see how the right UV, right temperature and right timing helps with the cure!

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