# Emerging Trends in Hybrid Additive and Subtractive Manufacturing
## 3 Results and Discussion
### Articles Analysis
#### 3.2.2 Areas and Sectors  
Hybrid manufacturing combines the advantages of additive and subtractive manufacturing. Therefore, it allows, on the one hand, to produce parts with high precision and good surface finishes, taking advantage of the great capacity of machining processes to finish parts with a high level of detail and, on the other hand, to optimize the material by combining both techniques, as waste is reduced by allowing additive manufacturing to generate parts of complex shapes with dimensions very close to those included in the design plans which, subsequently, by means of subtractive manufacturing, will be brought to the final dimensions of the part. Therefore, it finds a direct field of application in sectors such as aeronautics and aerospace, automotive, and medical, where complex parts with high precision are required [1; 2; 5; 11; 21; 40; 41; 46; 48; 52; 54; 58; 59]. In their work on the influence of the anisotropy of near net shape parts manufactured by LPBF on milling parameters, [PERSON] et al. [1] point out the manufacturing of aircraft engine parts and power system components as the natural application of hybrid additive and subtractive manufacturing (LPBF-milling). In this regard, they reinforce their statement by highlighting the capability of the process to ensure the assembly of the manufactured parts in complex systems. The work of [PERSON] et al. [2] clearly identifies a sector of application and development, with great importance in the manufacturing industry in general, by pointing out the use of hybrid additive and subtractive manufacturing (L-PBF and milling) in the manufacturing of conformal cooling channels in molds, as an alternative to manufacturing with straight-drilled cooling channels. Once again, the aerospace sector is pointed out in the work of [PERSON] et al. [40] as a current field of application and future development of hybrid additive and subtractive manufacturing. Moreover, it is specified in the production of titanium alloy parts, for which it is confirmed that machines are already available. [PERSON] et al. [41] present a different perspective when locating the field of application of hybrid additive and subtractive manufacturing, since they do not link it directly to any industrial or research sector, although they model the manufacturing of Ti-6 Al-4V parts, which are of great importance in the aerospace sector. On the contrary, they contextualize it in what could be considered a \begin{table}
\begin{tabular}{c c c c c c} \hline
**Ref.** & **Q** & **Cit.** & **Year** & **AM Subprocess** & **SM Subprocess** & **Material** \\ \hline
[1] & Q1 & 128 & 2021 & LPBF & Milling & Inconel 718 \\
[2] & Q1 & 103 & 2021 & LPBF & CNC milling & 316L stainless steel \\
[40] & Q1 & 57 & 2020 & PAW-WAAM & Milling & Ti6 Al-4V \\
[42] & Q1 & 45 & 2021 & Laser Hot-Wire & Milling & 316L stainless Steel \\
[44] & Q1 & 38 & 2021 & DED & High-speed milling & Inconel 625 \\ \hline \end{tabular}
\end{table} 
Table 7: Additive and subtractive subprocesses in five most cited articles. transversal sector, such as sustainable economy, with a clear environmental vision: cost reduction, energy savings, recyclability, and reduction of material waste. In turn, [PERSON] et al. [3] state that, at the time of their study, it is the company Airbus that uses most of the aircraft parts designed and manufactured through hybrid manufacturing. Once again, the aerospace sector is presented as the field with the greatest potential for the development and application of hybrid additive and subtractive manufacturing. [PERSON] et al. [44] also point to the aerospace sector, specifically to the manufacturing of monolithic structures, as a field of application for hybrid additive and subtractive manufacturing, and they do so by highlighting the challenge that distortion and residual stresses caused by machining in additively manufactured parts represent for its applications. The study by [PERSON] et al.