can I print a Hollow cube within a hollow cube?

is it possible to print a hollow cube within a hollow cube?
IE, Build a 100mm cube with a 5mm walls, then enclose it in a 200mm cube with 5mm walls.
One side would be common to both cubes so there is no support required.

Slic3r wants to interpret the space between the cubes and the inside of the internal cube as fill space and only print 1 cube with fill.

any ideas how to make Slic3r see what I see?

here is what I am actually trying to create. Basically I want one wall = 1mm and the rest = 2mm

onewall.skp

BTW, this is one side of the whole model, There rest of it butts up to the 1mm side so it can't be printed with the 2mm side down and reduce the top solid fill.

Edited 3 time(s). Last edit at 03/29/2017 04:24PM by ruggb.

In the lower right corner Slic3r will tell you if the model is manifold. If it's not, Slic3r tries to repair the model, with usually poor results. With a .skp extension, it's a pretty safe bet you're not generating a manifold STL. If that's the case, run it through a more robust mesh repair program like Netfabb or Meshmixer (and for the long term, find a different CAD program).

As has been said, Slic3r will certainly do that, so it is your STL which is faulty.

Dave

Well, the stl is solid. Noeither Sketchup or Slic3r has a problem with it. I removed all the inside structure and the slice was exactly the same in time and material for both models. Did anyone try slicing the model and looking at the result? If not, why did I post it?

I was on my phone and gave the most likely answer (especially when starting with a Sketchup file). Even had I been home I don't have Sketchup on any of my machines right now.

Quote
ruggb
Well, the stl is solid. Noeither Sketchup or Slic3r has a problem with it. I removed all the inside structure and the slice was exactly the same in time and material for both models. Did anyone try slicing the model and looking at the result? If not, why did I post it?

Post the STL rather than a file that needs an application that many of us do not have. You now say that Slic3r does not have a problem with that file, so what's the issue?

Dave

Sorry, I thought it was the stl I uploaded. I just picked the wrong file.

Let me try again, because after re-reading that I think it isn't right.
I am trying to make a part that has one wall = 1mm and the opposite wall = 2mm with the walls infilled but no infill between the walls.
I thought Slic3r would do that with this model, but it wants to infill the whole thing.

Loading that into OpenScad shows a part that has 3 solid sections separated by an extremely narrow buried gap = probably less than 0.25mm. All outside surfaces are solid. The gaps can be seen only by cutting the object.

If a gap is significantly less than the extrusion thickness then it will often be filled - if not by Slic3r then by the perimeters touching and fusing when printed due to the fact that the outer perimeters will always bulge slightly on the unconstrained side. What's the purpose in having such narrow gaps buried inside an otherwise solid object?

Dave

@dmould thx. I am not sure why you are seeing that. I have not used OpenScad, but I have it loaded. I will try to open it with that out of curiosity.
The problem was that the inside faces of the internal box were reversed. Rather impossible to see in Sketchup the way I had things colored (default).
When I reversed the faces, Slic3r cut it the way I intended. At first I punched a hole into the center and slic3r worked.
Apparently when I did that Sketchup automatically changed the faces. this file shows the intended result.


this is the stl with the faces corrected. I wonder if that affected what you see in OpenScad.
onewallr.stl

Many 3D design applications do not like fully enclosed hollow spaces - including OpenScad.

Dave