Blender has its own way handling units that won't play with lots of other software so it seems. Scaling models that are life size in blender down to 1/12th for 3D printing often makes the walls invisible to 3D slicing software and parts of the model just disappear and can't be printed. So you either have to make an unrealistic blender model with super thick walls or stuff around with solid models and waste a roll of filament on a model that should only use a few hundred grams.

It's a shame, Blender is so much better for designing organic shapes in 3D than CAD but it's a real bitch to scale them for printing.