Warning: Print warping w/ Formlabs resin

To let you guys know, the Formlabs resin can really warp significantly after printing!  Below is a custom Arduino+Shield+Screen case I designed and printed. It came out perfect, but after about 24 hours, the side walls towed inwards about 4-5mm! The dumb thing doesn’t even snap closed anymore.

I’m used to injection molded parts warping and 3D prints in ABS/PLA; however I was assuming since there was no temperature differential in the process there would be no warp. Not true – so now you know!

(FYI: I know you can design ribs to reduce this effect. It’s just more a matter of I didn’t even anticipate the resin would behave like this. So now you know! :wink:

Consider that the hardened resin is a photopolymer(IIRC), so it is still creating cross linkages within the material post print.
If you don’t already know, do some research on plastic part design to stabilize your parts with features (ribs, bosses, etc.), they are very helpful and enlightening.
Please, don’t take this as condescending or mean. Alternatively, create fixtures to place within/around prints so as to force a part from deforming?

The warping has to do with curing also. Looking at your picture, I can see deep yellowing in the middle of the print and towards the walls. Meaning you cured that area too much too fast, therefore the part has warped (It’s Physics!). I suggest curing in a box where you have even UV light that surrounds your entire part.

I usually cure next to a window (out of direct sunlight, which can cure the part too fast and turn it yellow), and I also rotate the part every hour. The part usually cures in 2-3 hours.

Also, the suggestion of putting some kinda ribs, supports, etc, to reinforce the walls is a good one. You can then remove them once the part has cured.