The steps in the current additive manufacturing processing sequence are: conceptualization and CAD, conversion to STL, transfer and manipulation of STL file on an AM machine, machine setup, prototyping (additive manufacturing) of part, removal from machine and clean up, post-processing of the part. Modifications can be then made to satisfy the criteria of shape, stress and strain state and temperature distribution during processing. An example of this procedure is presented for a cup holder printed in 2 polymers. Modification to this procedure for metal printing is now presented: initially printing a polymer prototype. The methodology of planning the prototyping process and of closed die forging technology by applying 3D printing are described. For a con rod: preform, die and the forging models, based on CAD documentation and STL file, were initially 3D printed from a polymer in processing steps. Optimization was carried out prior to the expensive metal printing. It is shown that to optimize shape of the manufactured part, simulation is a key step of planning prototyping and forging technology.