Problems printing flat surface

Hey guys, trying to print flat “clipsable” surfaces and I can’t manage to have consistant results afer several tries.
I tried to illustrate with as many pics as possible.
Here is the STL of the 2 parts :

I printed in 2 different ways one with support, and one directly on the base.
I did this because I noticed that the end results were different… You will see.
Here is how it came out, before curing but after a 5 min wash (the resin is dental SG) :

Both parts are pretty flat, and seems to fit well:

(I didn’t push those all the way down because it would be stuck at this point)

Then comes the curing, 30 min at 60°C as advised for Dental SG :

As you can see the “on the base” printed parts fit nicely as expected, but the supported one seems distorted. I need to apply some pressure on it so the 2 parts fits perfectly.
It seems like they bent.
Also, the parts printed with support is thicker…?!

I removed the support AFTER curing on those pics but I had exactly the same results if I removed them BEFORE curing.
Same things happened with Dental LT clear (20 min 80°C cure)

Any ideas how I can print parts with supports without having this distorsion on flat surface? It seems related to the curing, but I can’t skip this part…?
Those are just “test” parts and i’m planning to print more complicated structures with flat surfaces on it so i’ll need to use support but I can’t afford having this distorsion. Those structures are too complicated to be printed on the base directly unfortunately.

Thanks for your help !

I’ve recently found a simple method to make warped parts flat. Just attach a flat metal plate to your print, fix it with something to the plate. And put it into the oven. We had very good results, putting dental SG plate into the autoclave at 121°C, 1bar, 1hour. Let it cool down slowly remove the metal plate.

Another option is to print the part at 45° angle. Cure, autoclave it with supports, this should reduce warping.

Hey there @PlacidFly!

Thanks for taking the time to post!

Do you mind if I ask whether you’ve tried printing these parts at an angle? Typically with SLA printing, this will really contribute to cleaning up dimensional accuracy in a significant way. You might notice that whenever you hit the “Auto-Orient” button in PreForm, it will put it at or near a 45-degree angle, and that’s the reason for this behavior!

To oversimplify things a bit, the reason we suggest an angle on printed parts is so that the part can act as it’s own growing support structure.

Let’s imagine we’re printing a simple cube with one face pointing down, exactly parallel to the Build Platform. Once the printer works it’s way through the supports, it will get to the first layer of the cube. Now you have a 25-100 micron thick layer of resin, the width of a human hair, being held up by just a few very small support touchpoints. The areas between these supports will inevitably sag, just through the force of gravity, and now you have a warped face. This effect will be similar, maybe slightly less pronounced, on the topside of the model(the side without supports).

When you print at an angle, the part will usually build out of a corner, which means the part is supporting itself as it gradually builds upwards throughout the print.

I hope this explanation was helpful, but please don’t hesitate to ask if you have additional questions you’d like me to address here!

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