The introduction of additive manufacturing allows to picture a new supply chain for spare parts. In this new model the concept of digital spare parts is defined. The only information needed to reproduce a part using additive manufacturing technology is a ready-to-be- produced 3D model, that already contains manufacturing instructions. The scope of this work is to present reverse engineering methodologies to obtain a ready- to-be-produced 3D model from each of the possible single and combined input data available of a spare part: 2D paper drawing, 2D digital drawing, the physical spare part or the physical mold/tool used to produce it and nominal 3D model and their combinations of interest.