## 2 Background Work
### Review from the Literature of Decision Methods in AM Adoption  
A design process targeting AM consists of a digital dataflow that precedes the transformation of the raw materials into final parts [1]. The development of complex and organic shapes is based on traditional geometric modelling in CAD systems, even if new emerging tools and Topology Optimization (TO) systems are also used for this purpose [15]. The 3D CAD models are exchanged with other tools using STL, or better, by AMF, 3 MF, STEP and STEP-NC formats, which are all geometric exchange file formats which provide appropriate set of data [16]. Simulations with specific Computer Aided Design (CAE) software are usually necessary to foresee manufacturing distortions due to thermal effects and improve the surface quality by operating on part orientation and production parameters. Then, slices and the tool paths (G-CODE) are generated and sent to the machine. At this stage, it is possible to manage further parameters to optimize the geometric, finishing, and mechanical characteristics of the final piece. Post processing activities, such as post-curing, cleaning, successive machining, and treatments, must be carefully assessed since they strongly influence the resources needed to obtain the parts. The depicted workflow reveals that, at an early stage, there are many heterogeneous aspects a designer must consider and anticipate when deciding to adopt AM. Before starting such activities and investing considerable time, the design requirements must be carefully \begin{table}
\begin{tabular}{l l} \hline \hline
**Strengths** & **Limitations** \\ \hline Possibility of freeform parts with limited additional cost & Parts need surface finishing in coupling faces \\ \hline Possibility of hierarchical complexity (i.e., lattice structure) & Low dimensional and geometrical tolerances \\ \hline Customized performance by multi-material structures & Low building volume \\ \hline Material usage only where it is needed & Long processing time \\ \hline Possibility of light weight parts & Need of support structures for overhanging portions \\ \hline Reduction in logistic costs & High energy consumption \\ \hline Reduction in lead time & Lower mechanical properties compared to other processes \\ \hline Consolidation of assemblies & Residual thermal tensions and distortions in the parts \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Strengths and limitations of Additive Manufacturing (AM), on a general basis. assessed against the possibilities and constraints given by the manufacturing technology to finally succeed in the AM adoption. In this context, Design for Additive Manufacturing (DFAM) guidelines [17] and some related standards [18; 19; 20] are just at the beginning and more studies are needed to obtain a more complete view [21]. Design methods and tools are needed whereby functional performance and/or other key product life-cycle considerations such as producibility, reliability, validation and costs can be optimized and subjected to the capabilities of AM technologies [17]. In the industrial practice, the absence of clear DFAM patterns and guidelines often still results in occasional and unstructured usage of AM at the design stage. Additionally, there are only a few software programs that fully support the specific AM digital process, since most tools cover just limited aspects of the whole process, such as geometric modelling or thermal distortion simulations. Moreover, there are a few procedures to establish that a product is manufacturable with additive techniques. As a matter of fact, there are numerous product development approaches in the literature for various design contexts. Additionally, tools have been developed to support the designer to select the most suitable approach according to requirements [22]. However, there is a need to develop specific tools for AM product design in order to guide engineers and designers to understand this novel production method. For example, [PERSON] et al.