## 5 Conclusions  
This research successfully investigated the possibility of effectively using barrel tools on 3-axis CNC machines by designing and validating a pioneering specialized device. The designed device uniquely ensures the precise orientation of the semi-finished product in relation to the barrel tool, thereby fundamentally overcoming the limitations inherent to 3-axis CNC machines for this advanced machining technique. The validation of the device, through detailed metrological inspection using a Hexagon RA-7312 3D measuring arm (as presented in Section 3.8), demonstrated high dimensional and angular accuracy. Specifically, surface flatness values were between 0.002 mm and 0.012 mm, and angular non-closure was merely 0.006\({}^{\circ}\), indicating its effectiveness and precision in positioning the workpiece for machining with barrel tools.  
The designed device proved to be effective in enabling the machining of inclined planes with barrel tools on a 3-axis CNC machine. By using an interchangeable locating element, the device can be adapted for different programming angles of the barrel tools. The validation results indicate that the device ensures precise positioning of the semi-finished product, compensating for the limitations imposed by the lack of additional machine tool axes and allowing for accurate results.  
This paper presents an innovative method to extend the applications of barrel tools to 3-axis CNC machines, which are significantly more accessible and widespread in industry. The designed device provides a breakthrough solution that can be utilized in various industrial applications requiring the machining of complex surfaces, such as in the aerospace industry, the automotive industry, or mold production, contributing significantly to the optimization of machining processes and the reduction in production costs by making advanced techniques more broadly available.  
To extend the applicability and efficiency of the proposed method, further research directions could include  
* Evaluating the performance of the device with different materials and barrel tools.
* Integrating sensors for monitoring and optimizing cutting parameters.
* Automating the process of changing locating elements.
* Designing a universal device, adaptable to a wide range of programming angles.  
Figure 29: Barrel End Mill Profile: Characteristic Radii (r1 and r2).  
* Conducting Finite Element Method (FEM) analysis to further optimize the fixture's structural performance and dynamic behavior.  
Conceptualization, S.R.-N. and A.B.P.; methodology, S.R.-N. and A.B.P.; software, S.R.-N. and A.B.P.; validation, S.R.-N., A.B.P. and A.M.T.; formal analysis, A.B.P. and A.M.T.; investigation, S.R.-N. and A.B.P.; resources, A.B.P. and S.R.-N.; data curation, A.B.P. and S.R.-N.; writing--original draft preparation, A.B.P. and S.R.-N.; writing--review and editing, A.B.P. and A.M.T.; visualization, S.R.-N., A.B.P. and A.M.T.; supervision, A.B.P. and S.R.-N.; project administration, A.B.P.; funding acquisition, A.B.P. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Technical University of Cluj-Napoca, through the project \"Development of Advanced Technologies with Barrel End-Mills for Efficient Machining of Titanium Alloys in Aeronautics\" (ID 1508), project number 28/01-07-2024, awarded via the National Grant Competition--GNaC ARUT 2023. The APC was funded by the Technical University of Cluj-Napoca.  
Not applicable.  
Data are contained within the article.  
This work was supported by the \"Development of Advanced Technologies with Barrel End-Mills for Efficient Machining of Titanium Alloys in Aeronautics\" grant funded by the National Grant Competition--GNaC ARUT 2023.  
The authors declare no conflicts of interest.