# Five-Axis Finish Milling Machining for an Inconel 718 Alloy Monolithic Blisk
## 2. Machining of Blisk Blades
### Experimental Equipment  
The milling machine was a five-axis machining center CT-630 (Tongtai, Kaohsiung, Taiwan) equipped with a Siemens 840 Dsl CNC controller.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Property** & **Values** \\ \hline Outer diameter of the blisk (mm) & 364 \\ Outer diameter of the hub (mm) & 331.5 \\ Length of the blade (mm) & 16.25 \\ Thinnest part of the blade (mm) & 0.23 \\ Thickest part of the blade (mm) & 1.59 \\ Groove width (mm) & 6.46 \\ Number of blades & 78 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Blisk geometry.  
Figure 4: Dimensions of monolithic blisk (unit: mm).  
The material of a cutting tool considerably influences the machining of Inconel 718 alloy blisks. The tool must have high thermal hardness, good ductility, high wear resistance, and high impact resistance. In this study, a tapered ball-nose end mill (Jen Wu Cheng Shun Turning Tools, Kaohsiung, Taiwan) was used for machining, as displayed in Figure 5. Several studies on the machining of nickel-base alloys have shown that TiAlN-coated tools have better tool life in high-speed milling than other coatings, such as TiN and TiCN [17]. Therefore, this study used TiAlN-coated. The specifications of the tool are presented in Table 3[18]. We used water-soluble cutting fluids during the cutting process.  
A sensory tool holder (pro-micron, Kaufbeuren, Germany) was used to measure cutting force signals [19]. The sensory tool holder collected the axial cutting force, cutting torque, and \(X\)-axis and \(Y\)-axis bending moment during the finish machining of the blisk blades and wirelessly sent the collected data to a computer. The \(X\)-axis and \(Y\)-axis bending moments are defined as the bending moments in the XZ plane and YZ plane, respectively, where the \(Z\)-axis is the axial direction of the spindle. Because the tool axis was set to side milling during the cutting process, the bending moment was selected as the primary observation parameter. Polar diagrams of the bending moment in the \(X\)-\(Y\) direction were used to observe the force in real time [20]. The specifications of the sensory tool holder are presented in Table 4.  
A digital microscope (VHX900F, Keyence, Osaka, Japan) with depth-of-field synthesis and multiple illumination functions was used to examine the milling cutters during the experiments. The microscope was used to examine the wear of the cutting edge and the  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Property** & **Values** \\ \hline Measuring frequency (Hz) & 2500 \\ Maximum allowable speed (rpm) & 18,000 \\ Operating temperature (\({}^{\circ}\)C) & 0–50 \\ Collet size & ER20 \\ Spindle taper & BBT-40 \\ Total length (mm) & 155 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Specification of sensory tool holder.  
Figure 5: Tapered ball nose end mill.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Property/Composition** & **Values** \\ \hline Shank diameter (mm) & 6 \\ Tool nose radius (mm) & 1.5 \\ Over length (mm) & 75 \\ Cutting length (mm) & 20 \\ Taper angel (degree) & 3 \\ Rake angle (degree) & 2 \\ Flute helix angle (degree) & 30 \\ Flutes & 2 \\ Material & Tungsten Carbide \\ Coating & AITIN \\ \hline \hline \end{tabular}
\end{table}
Table 3: Specification of tapered ball nose end mill.  
side edge after machining. The magnification of the microscope ranges from 20\(\times\) to 1000\(\times\); we set the magnification to 100\(\times\) to examine the tools.