RE: Instant cloning...check this out !
We (my former employee) used 3D prototyping extensively. It produced working models to the extend that our customer(s) wanted to submit the prototypes to real testing, to which treatment of course they could not stand up.
Through the years the prototyped plastic got tougher, and could even withstand my hands doing the looking for me. Yet it still is not possible to protototype a plastic with toughness properties like nylon, or glass fibre reinforced plastics as need for strength.
Like WD said, the process needs accurate 3D data, best provided by skilled draftsmen. A X-ray scan will do for an image, but is not all that accurate to produce a 100% prototype copy.