Shrinkage issue on my Form 2

Hello everyone,

Its been a week I have received my Form 2. I’m using Grey V4 resin.

I have printed bottle cap prototypes and have noticed a 0.2 mm shrinkage on the ID.

I’m new to SLA printing. Any help would be appreciated.

Please find below images & STL for reference.

Thanks in advance.

Best regards,

Dear Siddhartha:

I had terrible deformation from using tough resin.

The first and only time I had good fit and dimension stability was when I

  • Used white resin from 2018
  • cured in IPA for EXACTLY the time in guide (I think it was 10 minutes each tank).
  • used weak UV finishing - about 20 minutes of low-angle sun on each of two sides.

With previous resins I had slimy parts, and as noted above for some resins, very distorted parts. The distorted parts were thick solids - the form2 is not very friendly to such types of parts.

I propose you start with the three bullet points above including new white resin, (or if they now have a fancy UV curing system, follow those directions making very sure they are specific to your white resin). Having gotten that to work, I propose you change only one thing at a time (part, IPA finishing, UV curing) until you learn what you need for successful printing. (In our lab, we tried many different resins and finishing and wasted a LOT of time. If we had started from simplest, best known case and incrementally went from there, it would have been much faster.)

The support folks are very kind and good about follow up… but my own experimentation was at least as important.

It’s typically hard to measure any finished part to 0.2 mm that doesn’t have ideal large flat faces, so I have never tried. Certainly our fit was better than 0.5 mm, but I can’t claim it was better than 0.2. Let me know if bullet points above end up with good dimensions or not.

Here’s hoping I was helpful,


0.2mm is not that bad for 3D printing, but still it could be better. Are the other dimensions as intended? If not, and if this is reproducible across models and resins, you could use the X/Y/Z fine tuning to calibrate your printer. If the other dimensions are as specified, and its only the inner diameter, I’m afraid you have to correct for this in your modeling application.

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Thank you so much for your suggestions.

I tried printing the caps in a different orientation (snap attached) and now the results are much better.Form2CapRPT1

I had a lot of problems with parts not matching the dimensions of the drawing.
Now, in every design I include a 10mm x 10mm x 10mm cube, that I can check the dimensions of before trying to assemble the printed pieces.
For me, temperature has a massive influence on the shrinkage of parts.

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Good strategy, this (including measurement prints) is also what a lot of Metal SLM printer operators do in order to quickly detect when something has gone wrong.

Which temperature do you mean, by the way? Room temperature, where the printer is in? Resin temperature (this should, at least for FormLabs resins, be managed by the printer), Cure temperature, or something else?

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Room temperature had a big influence on my prints.
We had a lot of trouble with an air conditioning system that I always had turned off when I printed and when another user had turned on while printing.

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IPA is bad for parts. I have stopped using it ages ago.


Thanks again for your advise,

The 3 points suggest by you worked perfectly for me. I used grey v4 resin and a nail curing lamp for 15 mins.

Best regards,

Wow - learning a lot here! Temp, resin and UV all important.

Grey sounds really ugly to me. Can anyone who has tried both white and grey comment on relative merits/demerits of either?



Interesting Updates on Temp, UV exposure, and water found after my last post: Formlabs has more information posted on “post-curing”: They recommend curing at 60C in 405 nm UV for 15/30/60 minutes for clear/opaque/fancier resins.

Now, our really first successful print was cured far below normal room temp, 4-8 C, but they want 60C!!! So, I have no idea what the sensitivity to Temp or importance of that is.

And then there’s water: The user groups seem to like water, sometimes warm water, sometimes after the first wash, and sometimes they like UV curing in water.

Testing IPA, Yellow Magic and RTX with castable resin and in between UV curing with LED array doesn't seem to do anything.

That all segues into the discussion of replacing IPA.
People want to find alternatives to IPA (flammable and harder to find now in EU). I would be careful about the comments on replacing IPA. I have read of tests of part of these ideas, I’ve seen people have the first solution last longer if it is something other than IPA, but I have NOT seen a straight comparison between IPA and “Yellow Magic” or other solutions. Just search the user forums for “IPA replacement” if you are interested in pursuing this.

I’m going to see how far I can get with warm water, seems pretty harmless, and UV light strips for when I can’t get ideal sunlight.


To be fair that information has been available for years and is being updated with every new resin, as each type requires different curing settings.

Temperature is critical especially for thicker parts as it helps for reticulation to occur deeper into the material (as per Formlabs word). If you look at this page and download the PDFs, you’ll see that mechanical characteristics change dramatically depending on the temperature.

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