# Surface Quality Evaluation in the Milling Process Using a Ball Nose End Mill
## 2 Materials and Methods/Research Methodology  
A parabolic surface was chosen as the modeled surface to be parametrically described. For the shape surface, the following equation was defined:  
\[y=-0.048\times x^{2}+30, \tag{1}\]  
The CAD system Solidworks 2022 was used to design the model (Figure 4), and the CAM system SolidCAM 2022 was used to select the milling strategy. A 3D model of the test specimen is shown in Figure 4.  
For the experimental research, three test specimens were produced. An aluminum alloy (AlCu4 Mg, Slovalco, a. s., Ziar nad Hronom, Slovakia) with the following mechanical properties was selected for production: tensile strength = 420 MPa; yield strength = 240 MPa; hardness = 120 HB. The reason for the selection of this material is that AlCu4 Mg is one of the most important aluminum alloys. Due to its strength characteristics and resistance to fatigue, it is often used in aircraft airframe structures (airframe, wings) and in the military industry in general. The experimental tests were carried out on an EMCO MILL 155 three-axis machine with a maximum spindle speed of 5000 rpm (EMCO MAIER Ges.m.b.H., Hallein, Austria), which contains a Heidenhain iTNC 530 control system. Roughing, semi-finishing, and finishing operations are mostly used in the machining process for milling free-form surfaces [59; 60]. The machining operations specifically used in the experimental research are shown in Figure 5.  
Figure 4: 3D model of the test specimen.  
The roughing and semi-finishing operations were the same for all three specimens to achieve the same surface texture. Of all the operations, the finishing operation is the most challenging because the cutting speed of tool-material contact and chip formation change during milling [61; 62]. The cutting parameters with the tool used for fabrication are shown in Table 1. A sintered carbide ball-end mill was used for the finishing operation using a fixed BT-40 system with a mechanical collet chuck with a tool overhang of 40 mm. Cutting parameters were selected according to the recommendations of the tool manufacturers. If a parameter was specified by a range, the midpoint of the range was selected. Due to the parametric limitations of the machine used (spindle speed), the usable cutting speed for small-diameter tools was limited by this parameter. The criteria for the surface parameters were based on the requirement to minimize finishing operations, which are often closely related to the production of 3D surfaces. A mineral oil-based emulsion coolant was used for cooling during production. The dimensions of the test specimens were 65 \(\times\) 65 \(\times\) 40 mm. The input data defined for the milling process of shaped surfaces are shown in Table 2.  
The following methods and equipment were used in the experiment:  
1. Comparison and evaluation of surface topography using a Keyence VHX-5000 digital microscope (Keyence International, Mechelen, Belgium).
2. Roughness evaluation using device Alicona InfiniteFocus G5 (Alicona Imaging GmbH, Raaba/Graz, Austria).
3. Evaluation of shape deviations using coordinate measuring machine ZEISS Duramax HTC (Carl Zeiss, Jena, Germany).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Tool Diameter** & **Cutting Speed** & **Feed per Tooth** & **Spindle** & **Tool Producer** & **Tool Code** \\
**[mm]** & **[m.min\({}^{-1}\)]** & **[mm]** & **Frequency [RPM]** & & \\ \hline End Mill D 18 & 270 & 0.125 & 4800 & \begin{tabular}{c} Korloy \\ (Seoul, Republic of Korea) \\ ZPS-FN \\ (Zlin, Czech Republic) \\ \end{tabular} & AMS2018S \\ End Mill D8 & 123 & 0.029 & 4900 & \
\begin{tabular}{c} ZPS-FN \\ (Zlin, Czech Republic) \\ \end{tabular} & 273618.080 \\ Ball End Mill D6 & 92.4 & 0.022 & 4900 &
\begin{tabular}{c} ZPS-FN \\ (Zlin, Czech Republic) \\ \end{tabular} & 511418.060 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Cutting parameters with the tool description.  
Figure 5: Selected machining operations.