Understanding Supports

For hypothetical discussion, if I were to print a hollow sphere like the picture attached, would it require internal supports? Since the geometry is self supporting, something like this would not need internal supports on a FDM printer.

Would it likely come out without internal supports in a Form?

Easy enough to try, no? But no, it wouldn’t need internal supports. There’s nothing that internal supports would need to support if you only have half the sphere… And depending on wall thickness and maybe the size of the sphere, you might get away with printing it without any internal supports at all.

There’s a checkbox for that, and I always leave it “off” unless I have a specific reason to turn it on. I’ve found that internal supports often provide at-best cosmetic improvements to the print (they don’t keep the print from completing successfully) and since they’re internal areas, who cares if they don’t look perfect? Fewer supports makes it easier to get the print separated from the base…

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Easy enough to try - but machine time and resin is valuable.


Thought it was best to have a basic understanding too and might learn more by asking than just running the experiment.

Note that I was talking about a complete sphere - I have like half the layers showing so the supports are visible.

So long as the print is continuous and supports itself it sounds like they aren’t needed? That was my hunch.

I think could print it without internal supports, but unlike FDM, you do need at least one hole to let the uncured resin out.

Thanks Macro, Yes of course - I would think probably two holes at a minimum.

Or, one hole and a syringe.


I actually don’t mind the holes - they are easy enough to fill before molding.

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And so - without internal supports it highlights some of the model red. I suppose that is an indication that it thinks it needs internal supports?

Yes, I would try using manually adjusted internal supports - way fewer than were in your original image, maybe 6 or 7.

Thanks. I am just trying to grasp a general understanding.

In the way I am used to thinking about prints, the sphere itself is all the support it would need. I guess I don’t understand why the shell of the sphere wouldn’t be adequate support then?

you should add a few heavier supports to the exterior.

I’m wondering; what would be the best way to print a simple hollowed cube? I have printed one previously but it came out horrible. There were many visible lines on the sides and the top didn’t close perfectly (there were two tiny holes or so). Of course I added an escape hole so that resin can escape. Thickness used was 2mm.

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