## 3 Main Concerns in AM Quality Control  
Additive manufacturing technology was first introduced in the USA during the 1980s. The AM term encompasses all methods which shape the final product using a layer-by \begin{table}
\begin{tabular}{c c c} \hline \hline
**Qualification Step** & **Conventional Manufacturing** & **Additive Manufacturing** \\ \hline \multirow{6}{*}{Technology assessment} & \multicolumn{1}{c}{Mature} & \multicolumn{1}{c}{Immuture} \\  & Normally repeatable & Not-repeatable \\  & Homogeneous microstructures & Inhomogeneous microstructures \\  & Properties are isotropic & Properties are anisotropic \\  & Dense structure & Porous structure \\  & \multicolumn{1}{c}{Mature} & \multicolumn{1}{c}{Immuture} \\  & \multicolumn{1}{c}{Many successful experiences reported in the} & Less experienced in the industry \\  & \multicolumn{1}{c}{industry} & Mostly in the form of liquid, powder, wire, \\  & \multicolumn{1}{c}{Mostly in rod and biller form} & \multicolumn{1}{c}{filament, sheet, etc.} \\ Manufacturing & Most of the parameters remain unchanged for & Drastic changes are required when a \\  & \multicolumn{1}{c}{different vendors} & \multicolumn{1}{c}{manufacturer changes} \\  & \multicolumn{1}{c}{Sufficient field data is available} & Less experienced in the industry \\  & \multicolumn{1}{c}{Failure modes and types well studied} & Failure modes and types are still under question \\  & \multicolumn{1}{c}{Test methods are normally mature and reliable} & Test and evaluation methods are not standardized. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Qualifications features of additive and conventional manufacturing process. layer addition of materials. In the last 30 years, AM processes and equipment showed fast growth, and nowadays, more than 20 AM processes have been introduced. AM techniques can process a wide range of materials, including polymers, composites, and metals. In the case of metallic products, there are two main branches of AM processes, powder bed fusion-based technologies (PBF) and directed energy deposition (DED) based technologies, however, binder jetting has also shown limited capability in producing metallic parts. The main subcategories of DED are laser-engineered net shaping, direct metal deposition, electron beam freeform fabrication, and arc-based AM. Furthermore, the subcategories of PBF technology are selective laser sintering (SLS), electron beam melting, and LaserCUSING. These techniques can differ in terms of principle processing material, heat source, and economic advantages. Research is still ongoing to minimize the operational cost, increase the quality of the final product, and increase the production speed and flexibility of the individual AM machine to produce parts with versatile material types and geometries. Rapid growth in AM techniques, equipment, and the introduction of new generations of AM processes implies that the qualification procedure shall be dynamic and flexible to cover all new equipment and technique types. The additive process is a kind of micro-welding that uses powders and beam power to melt the powders and produce a track weld [28]. Figure 1 shows the schematic of track production in the SLS manufacturing method. The quality of the track directly affects the quality of the final product. Therefore, the qualification of the build can be compared with the qualification process of the conventional welding process. In an additive manufacturing system, the parameters such as powder quality, heat input in the melt pool, beam power, beam diameter and intensity, beam scan pattern (spiral, meander, etc. ), bead cooling rate, powder preheat, track height, track overlap, track width, post-processing, etc., affect the quality of the micro-welding process. In addition to the process and machine type, the quality of the feedstock is of significant importance for producing high-quality additively manufactured samples.