Preparing a 3D model for 3D printing inner geometry questions

[Anonymous]

Hello,
So Im new and trying to make a model to be printed. I was wondering about interior geometry. I was wondering for example if i wanted to make a box with a cylinder sticking out from the top. Could I just make a box and add a cylinder on top going threw the box's top face and then joining them to one object, will it be ok for printing? I know In Blender it was ok, but I was watching videos that show you how to prepare models for printing by welding and having no inner geometry.

[dgorsman]

That's going to depend on a lot of factors e.g. what type of printer, what material you are printing with, whether the rod should be removable/free moving/etc, size of box/rod/etc.  In some instances you want to have an interior shell for the box to avoid wasting material.  In others an interior support structure to get a combination of less waste and highest strength is required.  In others you may want to print the walls of the box separately with indexing features so they snap together.

[Anonymous]

As you've described it, no not likely. You do need to combine the object, but you also need to combine the topology. Merely interpenetrating faces is not sufficient. 

I would do a Boolean>union (thats what its called in 3dsmax) to both combine the meshes and the topology. 

The next consideration, as was previously mentioned, is should it also be hollow to save on materials. That's up to you, but its not a bad idea. For that you can simply add the "shell" modifier in 3dsmax and adjust the inner amount. 

But either way, the main thing is to make sure your box and cylinder are one object and one topology. 

[Anonymous]

In regard to your first question about creating a box, then adding a cylinder through it: It depends on the 3d printer and slicing software you have.  If you use a service with advanced printing capabilities like Shapeways, then yes, this may be possible.  For example, when you export both objects as a .STL, it will be treated as a solid shape.  To verify this, simply open the STL in Netfabb, and you'll see the shape is considered 1 part with orientable, closed surface.  This should be legal for printing.  The same would be true if you uploaded the object to Shapeways.  Their software would see the .STL as one solid volume, and ignore any of the interpenetrating geometry (I think).  The downside to this technique, obviously, is you can not have an inner shell when you have two interpenetrating objects, unless you boolean them together, as Chris mentioned above.

[Anonymous]

Ok I understand what should be done now, thank you all for the helpful info! I will go ahead and use the union boolean to join objects.

Thank you again