When creating a shell, how does the Thickness value correlate to what unit system is selected? For instance, if mm is chosen, does a value of 1 = 1mm? If inches is selected, does 1 = .1?
When opting for certain materials via Shapeways, they have a minimum requirement of 4mm for wall thickness when selecting a metallic finish. Is there a way to accurately measure this inside ZBrush prior to 3d print export?
Thanks,
-Steve
ZBrush isn’t working with units like you have in most 3D package. For the thickness, it’s in correlation to the object bounding box size. You can’t specify a value with an unit to define it.
Only 3DPrint Exporter can manage units, but it’s only for an export and have no relations with everything else in ZBrush.
It is better to have a larger thickness for 3D printing that having just the minimal thickness value 
sigh That really doesn’t help me out, it’s more like a guestimate then.
ZBrush 5 request - MANAGEABLE UNITS AND MEASUREMENTS PLEASE!
-Steve, offering my services for beta-testing. 
I second that request. I have been dealing with exactly the same thing. I extract shells for 3D printing with Ponoko, and have to just guess at the thickness. It’s created problems with the printing bureaus. I need some way to have the extraction units correlate exactly with the 3d Printer Exporter.
I appreciate the new internal shell feature in Zbrush 4R2.
The shell generation that Zbrush has now is the best that I’ve seen, however frustrating it might be that units can’t be specified. The thing is, as we’re all painfully aware, is that units aren’t ever being specified until the last second when the model is being exported.
It would be nice to have the bounding box dimensions be definable on import - but apparently Zbrush has no units at all incorporated into it’s core engine?
I already often incorporate a 1" x 1" cube into my models for tracking scale, so now I’ve been adding a smaller cube that is the size of my required shell thickness. If nothing else, at least I can eyeball the cube against the generated shell. Maybe that will help you, Steve?