3D printing of empty inner volume

Is there a way how I could design inner volume above outer volume? I would like to design it for 3D printing purpose and I tried Boolean difference and I got the nothing is intersect. This may be true I need my inner volume to be designed certain thickness (offset) from outer surface volume as on picture in clipping plane attached.

Slicer options will handle that.

If you really want to make your own thickness, then you can either have a tiny hole somewhere connecting the inside to the outside, or you can manually Mesh your inside object and then flip the normals on it.

Well, indeed I rather design it to control thickness individually. But I did not find a proper way avoiding to use Rhino mesh tab functions.

Okay. I told you what to do in that case then. Rhino does not support calling one closed solid entirely inside another a single ‘object.’

I see. So at nurbs level it is not possible to design.
Could you please describe mesh option in more detail?
Both volumes must be mesh type?

Hi Mateas -
I guess Jim’s main point is still that your slicer will most likely take care of this. Have you tried sending the model to the 3D printer?

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not yet, I tried _MeshBooleanDifference from both mesh volumes and it didn’t make it.

And for slicer I do not know how to tell it make a hole from inner volume even when inner volume is separate as a mesh inside the bigger mesh.

No it’s not impossible to design, it’s just not a feature of Rhino to call such objects “one,” it’s treated as “bad” geometry, it’s called “non-manifold.”

Option 1: When ready to make your STL, just manually run the Mesh command first to make your STL mesh. Then all you have to do is run “Flip” on the inside mesh and the slicer will know it’s the ‘inside’

Option 2: Connect your inside and outside using a small cylinder somewhere.

Anyway, the more important point is that the slicer will handle this, doing this at the ‘model’ level so that you can ‘tune’ it is a waste of time compared to using the slicer wall thickness and infill settings.

Here, I align both meshes correctly for slicing position. But it did not work after slicing. The slicer ignore the small volumes.

I manily use Siplify3D as a slicer but I do not know where to find the FILP command. There is normals check direction command only, I guess.

If you know which slicer can make the mash normal flip please let me know the name of it. I will test it. Thank you.

I meant to do that on the interior mesh in Rhino.

Well, it is not technically perfect but I could do it in Blender by Boolean difference of two meshes.

I wish Rhino could make it on NURBS level. I use mesh operation in case there is no other choice.
Thank you all.
Have a nice day.

dear @mateas

i hope @JimCarruthers solved this topic.

to check wether the normals are correct, use the _dir command.
also check if the polysurface / mesh is solid (in properties) or with _showEdges.

please mark the topic as solved / Jim s post / answer as solution. so others don t need to dig into this.

kind regards - tom

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Thank you all.