Sphere problems

I am having trouble printing a half sphere-like form. Photos attached. It won’t print the top of the sphere.

I was printing without supports, I made my own - because I wanted a totally smooth, flat bottom (see photo1) and the supports don’t seem to allow this (or help with the problem at the top anyway) - see photo2
I thought it might be a problem with fluid getting trapped into the sphere as it prints - but adding holes didn’t help - see photo3
I then tried printing in two halves - see photo4
I then thickened the walls up to 1/8" and added a ton of support in the middle, I thought the problem was basically overhang when you get to the top of the sphere and the curvature starts approaching horizontal - see photo 5.

Not sure what the problem is here - any ideas?

Post a picture of it from in PreForm so we can see what it’s supposed to look like!

Send us the .form files so we can analyse them.


Hi @Alex_McLean, the hole needs to be in the base area-- the area that gets printed first. The pressure build up causes things to pop when it presses down and the fluid needs somewhere to go. The vent hole in the tip of the sphere does not come into play until the entire print is basically done.

The last picture with a ton of internal supports probably made the situation worse. Now it has multiple pressurized areas instead of just 1 big volume.

Try vent hole in the side of the dome- somewhere close to where it meets the flat bottom part.

150222_globePrint3a.stl (1.1 MB)

This is essentially what i want - without the supports

Thanks for the tips!
I can’t seem to upload further files - but that one is essentially the external form that I want.
I will try with a hole in the base area and the side.
What minimum size hole do you think I need?
Can I get away without a hole in the top?

I do not think the hole on the top matters at all.
I’m not sure if FormLabs has a recommended hole size, but I know Shapeways suggests 2+ 1mm holes or a single hole 2mm or larger.

The holes will need to be in the inner and outer spheres.

Thanks Paul.
So should I include supports of my own or not?

the supports in the last picture are very overkill. I believe it needs some sort support, but I could be wrong.

Getting closer. 4no. 1/8" holes in the outer sphere near the base, a ton in the inner one. I included holes in the base but thinking about it don’t really understand why they make a difference (there are no generated supports so they are essentially holes directly to the base plate)

Limited supports inside, near the center. Still getting problems at the top of the sphere.

Any ideas?
More holes in the side?
Maybe I need a hole in the top after all?


Yea, those holes directly on the baseplate are not going to do anything. That hole on the side is exactly what i was talking about. Since its still failing despite that hole, it is not a problem of internal pressure.

What is your wall thickness?

If it’s internal pressure it usually fails at the bottom not the top.

Hey Alex! You guys are definitely on the right track - hollow prints can be really tricky at times, especially when printing directly on the build platform.

Since this part requires internal supports, it may still be an internal pressure issue. The supports take up space on the inside, making it harder for the resin to flow freely and making a blow-out more likely. The double-shelled version you first posted photos of would increase the likelihood of this as well. If you’d like our support team to take a look at your Form file and make some more specific suggestions, feel free to write in to support@formlabs.com and we’d be happy to help!

Thanks Roxanne!
I sent an email

Any update on this Alex? I’m intrigued to find out what is causing the problem.

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.