# Emerging Trends in Hybrid Additive and Subtractive Manufacturing
## 3 Results and Discussion  
Before analyzing and discussing the selected papers, a summary is presented, sorted in descending order by total number of citations, with the intention of highlighting those that are most relevant to the research community at the time of the study. Table 3 shows the quality criteria (Q1, Q2, PP), the year of publication, and the country of the first author. The column corresponding to the first author's institution of affiliation is highlighted, as it can serve as a guide for future selective searches for research on additive and subtractive hybrid manufacturing, using methods other than traditional search platforms and databases. Of particular importance is the last column, which presents in a summarized, formula-like \begin{table}
\begin{tabular}{c c c} \hline \hline
**Selected Articles** & **Number** & **\%** \\ \hline Total & 27 & 100\% \\ Q1 & 18 & 66.67\% \\ Q2 & 7 & 25.93\% \\ Proceeding Papers & 2 & 7.40\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Selection data. Figure 5: Flowchart of selection process of works for review (PRISMA). manner the additive and subtractive hybrid workflow addressed by each paper, either individually or as the main flow of the study. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Ref.** & **Q** & **Cit.** & **Year** & **Institution** & **Country** & **Hybrid Flow** \\ \hline
[1] & Q1 & 128 & 2021 & University of the & Spain & LPBF + Peripheral milling (Inconel 718) \\
[2] & Q1 & 103 & 2021 & University of Groningen & Netherlands & LPBF + CNC milling (316L stainless steel) \\
[40] & Q1 & 57 & 2020 & TECNALIA, (BRTA) & Spain & PAW-WAAM + CNC milling (T16 Al-4V) \\
[41] & Q1 & 54 & 2020 & University of Palermo & Italy & — \\
[3] & Q1 & 46 & 2022 & Karabük University & Turkey & — \\
[42] & Q1 & 45 & 2021 & Oak Ridge & USA & Laser Hot-Wire Deposition + CNC milling (316L stainless steel) \\
[43] & Q2 & 42 & 2020 & Palo Alto Research Center & USA & — \\
[44] & Q1 & 38 & 2021 & The University of Texas & USA & DED + High-speed end milling (Inconel 625) \\
[45] & Q1 & 38 & 2021 & University of Calabria & Italy & DED + CNC turning (IN718 powder) \\
[4] & Q1 & 38 & 2020 & University of Applied & Germany & SLM + 3-axis milling (Maraging steel 1.2709) \\
[46] & Q2 & 36 & 2023 & Ahsanullah University of & Bangladesh & — \\
[47] & Q2 & 34 & 2020 & University of Patras. & Greece & DLM + Milling + Vision (316L stainless steel) \\
[48] & Q2 & 35 & 2020 & Material and Beam & Germany & LMD + Cryogenic milling (T1-6 Al-4V powder) \\
[49] & Q1 & 32 & 2021 & Shenzhen University & China & DED + Dry milling (PEEK, CF/PEEK) \\
[50] & PP & 32 & 2020 & Technical University & Germany & WAAM + Robotic spindle machining (AlSi12) \\
[5] & Q1 & 29 & 2022 & Oak Ridge & USA & DED + CNC milling (316L stainless steel) \\
[51] & Q2 & 28 & 2021 & Hamburg University & Germany & PBF-LB/M + CNC milling (316L stainless steel) \\
[52] & Q1 & 28 & 2021 & Inspire AG, Zurich & Switzerland & Casting + CNC milling + DMD (Inconel 718 powder) \\
[53] & Q2 & 26 & 2022 & Palo Alto Research Center & USA & Powder Bed Fusion + Multi-axis CNC machining \\
[21] & Q1 & 23 & 2022 & University of the & USA & LMD (Hastelloy®X sobre \\
[54] & Q1 & 22 & 2023 & RMIT University, Melbourne & Australia & Inconel®718) + 5-axis milling \\
[11] & Q2 & 22 & 2022 & ISEP—Polytechnic of Porto & Portugal & — \\
[55] & Q1 & 21 & 2023 & City University of & China & (PDMS + ZrO2/AION) + Laser \\  & & & & & & engraving/cutting \\
[56] & Q1 & 21 & 2023 & Laboratories for Materials & Switzerland & machining (pyramid \\  & & & & & & profile shaping) \\
[57] & Q1 & 20 & 2021 & Harbin University of Science & LMD + Side Milling (316L stainless steel) \\ \hline \end{tabular}
\end{table} 
Table 3: General results. Table 4 lists the journals or conferences in which the selected articles have been published. This table has a double interest. It shows the significant dispersion of the works, as most of the top-tier publications have only one work among the selected ones.