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I have a STL file with a rather large roughly-spherical object. I'd like to 3D print it to be fairly large, and hollow inside. Since the printer I'd be using has a max size of (18–20 cm)^3, I'd have to print this in pieces and then reassemble them into the sphere-like shape. The textured surface of the object is important, but small seams would seem unavoidable.

My Question

How could I 3D print a hollow sphere or sphere-like object that's too large for the available basic 3D printer?

Because this would need to be done in parts, it's more complicated than the designs I've made. Because the final product is roughly spherical and hollow (i.e. nothing is nicely angular), it's trickier than some other designs.

(I have little experience with 3D modelling/CAD, so I'd somewhat prefer solutions with minimal advanced steps such as designing my own joints and whatnot...but advanced steps are definitely okay if part of a great solution!)

My Ideas So Far

I know I could cut the sphere roughly in (e.g.) eighths via planar slices, print the eight pieces individually, but then the question is how to attach them. I am also concerned that the seams might be too noticeable. (Perhaps there's a better way?)

I could just glue the pieces together. My fear then is that it would lack internal structural support if they were attached only at the outer layer (unless the skin thickness were excessive, at least near the boundary).

I imagine I could give the pieces internal supports with dowel joints or snap-fit joints (e.g. these), but I lack knowledge of how to do that and don't know whether that would even work well.

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  • $\begingroup$ You can also look around to see if you can find bigger printers available for use. Depending on where you live, you might find a Fablab with printers free to use on a first-come first-served basis, or fond a shop that has a bigger printer and would let you use it against a fee. $\endgroup$ – Sava Dec 21 '18 at 23:27
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A sphere can be put together quarters easily, but those need support in the center. However, there is a slightly different cut is more economic:

  • Cut a top and bottom "plate" off, print them separately, the lower one "upside down"
  • Cut the remaining piece into quarters
    • For more equal printing, maybe even cut them along the equator too and print the lower half "upside down"

A simple sphere, cut off top and bottom, then quartered

This way, the support material can be reduced to a minimum - only the top and bottom will need any support, and it is easily accessible to smooth it away.

If the walls would be something like one millimeter thick, any good glue should work. If you want to reduce the visible seam, you might bevel the faces, so that the wall has a little gap on the inner wall. As most glues shrink as they harden, it will flatten into the "gap", evening out the internal face.

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  • $\begingroup$ I don't really understand what you mean by 'plate'? $\endgroup$ – Sava Dec 21 '18 at 23:27
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    $\begingroup$ @Sava I added a picture what I meant $\endgroup$ – Trish Dec 22 '18 at 0:14
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    $\begingroup$ Upvoted, very smart way of printing a big sphere! $\endgroup$ – Sava Dec 22 '18 at 0:17
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    $\begingroup$ if the sphere is really big, more divisions might be needed. My cut keeps the print orientation the same for all parts, no "turns" $\endgroup$ – Trish Dec 22 '18 at 0:20

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