I am getting my butt kicked by Blender. When I export an STL of a simple cube (the one that comes up by default), it looks right in Meshlab, but if I try to bring it into Slic3r, it reports the size as 0.00x0.00x0.10, volume 0.00, facets 12 (1 shells) and says it’s manifold. If I try to slice it, Slic3r says “No layers were detected. You might want to repair your STL file(s) or check their size and retry”.
I have tried changing the units to metric and setting the dimensions to something sane (10cm cubed) but the results are always the same.
I new to Blender so I’m sure I’m just missing something stupid, but so far haven’t found the right checkbox to click 
Did you check the cube’s actual dimensions in Netfabb? It might just be an odd conversion between Blender’s internal units and real-world millimeters.
In Blender units, 1 unit = 1mm in the reprap universe. I don’t know how/if changing the units in Blender alters that. Try going back to the default units and checking the size. Also, make sure the cube mesh is near its origin, which should in turn be near coordinate 0,0,0.
I had the same issue and worked it out.
Open the scene tab. Under ‘Units’, I’ve got mine set to Metric, so then I change the scale to 0.001, which means that the scale is correct when you export.
If you don’t do this, when you export to STL from Blender, the newer version have an option to specify the Scale in there, which when set to 1000 corrects the scale. But as I said, do that ONLY if you haven’t changed the scale as per the previous paragraph!
That was it @Daniel_Porter . If I set the scale to 1000 when I export, I get what I expect in Slic3r (why I do not know, but I’ll figure that out later 
Thanks!
@Jason_Gullickson Great to hear… but if you export via the 3D Printer Toolbox AddOn, which allows you to check your model, you will need to set the scale in the Scenes tab.
I was wondering about that @Daniel_Porter . I’ll play with it a bit to figure out how one affects the other. I’m still learning my way around the controls and getting a handle on how they interact, so with some luck I’ll get a set of settings that works as expected and I’ll create a template or something
Thanks again!
@Jason_Gullickson the one setting in the Scene tab messed me around to the point I was using the Scale option when exporting. When I was exporting, I didn’t realise the Normals weren’t correct. The Toolbox let me check that and confirm that the model was fine before I exported. But as I mentioned, only change one of those settings, changing the scene then changing the scale when exporting, the objects will be HUGE!
FYI the STL format does not recognize any unit system. It’s the software that exports it or imports it that decides the unit system. For Slic3r a unit = 1mm, so that’s how you need to model it or export it from your modeling software.