Jim Foltz's 'simple_shell' will work on a manifold [solid] form [needed for 3d printing anyway?] - however, the wall thickness of a 3mm shell isn't exactly 3mm all round - it might do though [it uses scaling about a center]... Fredo's JPP [JointPushPull] has been recently updated to give a more constant thickness 'shell' - however, an exact constant shell thickness for multiple facets at a vertex is impossible to calculate... Note that you might have problems making very small faces [<~1mm] so scale x10 and then do the 'shell', then scale down x0.1 before exporting [small faces can exist but making them is the trip-hazard...]

yeah rich, I noticed it slowed down immediately. my computer is an old old man. StilTeg, I think you might have something there. I didn't realize I could change all that stuff in the file info thingie. This guy is pretty small. I'll play with it a bit and see if I can break it further.