# Manufacturing Processes of Integral Blade Rotors for Turbomachinery, Processes and New Approaches
## 2 Monolithic Components: Manufacturing Processes
### Conventional Machining Process: 5-Axis Milling
#### 2.5.2 Manufacturing Strategies  
Manufacturing processes for complex geometries are still for many researchers a subject matter related to the number of aspects involved. In the first instance, it should be outlined that the programming of these complex geometry machining strategies is commonly performed by CAM software, since manual programming is practically impossible. Nevertheless, roughing and semifinishing strategies, before the finishing stages, require special attention because it is at those stages the machining process productivity can be optimized [54; 55]. IBRs manufacturing processes optimization is focused on prioritizing the productivity for roughing strategies and accuracy for semifinishing and finishing strategies. Productivity mainly depends on the machining times and tool cost. Despite the great technological advances related to milling cutting tools, the IBRs manufacturing still requires the use of a lot of milling tools due to the tool wear and breakage. In addition, the increase of productivity with aggressive cutting conditions and strategies implies the rise of tool wear. Therefore, the main objective for roughing stage is achieving a balance between productivity and process costs. Figure 10 shows three of the most applied roughing strategies: slotting, trochoidal milling and plunge milling. Full slotting strategy consists in using the complete diameter as the radial depth of cut (a\({}_{\text{e}}\)). The main advantages of this strategy are the high material removal rates in steady state and the simplicity of the required tool-path. Nevertheless, this strategy causes elevated radial cutting forces, so in some cases, the axial cutting depth needs to be performed in many passes. Trochoidal milling combines the tool linear movement with circular trajectories, implying less tool wear compared with slotting [56]. Moreover, radial cutting forces are smaller, which offers the option of using higher cutting speed and axial depth of cut. The main drawback of trochoidal milling is that it requires higher machine dynamic capabilities to perform the continuous circular movements [57]. At the plunge milling, the tool moves along the tool axis (z-axis); the machining is performed with the secondary  
Figure 9: Sandvik®[45] and Emuge-Franken®[47] milling cutting tool forms for IBRs manufacturing. edge, and lateral vibrations are avoided. Some plunge applications are cited hereafter: deep slots, insufficient stability and materials with low machinability [58]. On the other hand, semifinishing and finishing strategies define final geometry, dimensional tolerances and surface finishing requirements. Milling strategies are categorized as a function of the tool contact surface during the machining, differing two types for complex geometries: point milling and flank milling (Figure 11). The point milling strategy is performed with ball-nose cutting tools, and the material removal is conducted with the spherical side of the milling tool. This strategy's main drawback resides on its high machining time and the extreme tool wear because it is constantly cutting with the same tool region. On the contrary, at flank milling strategy, the machining is performed with the total effective length of the tool, so the productivity of this strategy is higher than the point milling, reducing machining times and making the maximum use of tool cutting edges. Nonetheless, this is not always a useful option for complex geometries because the accuracy of this strategy depends on the surface type being necessarily a developable ruled surface for its adequate application. Moreover, another inconvenience of this strategy is found in the operation stability, since it is much influenced by the defined cutting parameters; if they are not the appropriate ones, there is a possibility of vibrations appearing; leading to inadmissible finishing requirements.