# Manufacturing Processes of Integral Blade Rotors for Turbomachinery, Processes and New Approaches
## 2 Monolithic Components: Manufacturing Processes
### Conventional Machining Process: 5-Axis Milling  
The conventional milling process consists in a rotary cutting tool that removes material from the workpiece surface until achieving final desired geometry [41]. It was in 1795 when [PERSON] used the first milling machine for the clock industry [42], but it was not until around 1810 when the milling concept was considered independent from turning technology [43]. This process suffered a drastic evolution thanks to Computers and CNC improvements in the 80's [44]. Nowadays, the milling process embraces numerous capabilities for complex geometry generation and multiple materials, offering flexible solutions.  
Related to IBRs manufacturing processes, for medium-sized impeller and blisk manufacturing, 5-axis milling is the conventional material removal process most commonly used. Thus, a complete component is machined from a solid block, obtaining a monolithic piece without discontinuities between the different elements, so junctions are avoided, obtaining superior mechanical properties. These advantages are critical for turbomachinery rotary components because they are exposed to elevated temperatures from exhaust gases (900-1400 \({}^{\circ}\)C) and extreme working conditions, so heat resistant superalloys are required such as Inconel(r)718 or Inconel(r)615. Comparing blisks with assembled discs, the weight is reduced up to 20%, increasing the efficiency considerably, reducing at the same time the fuel consumption and gas emissions. Nonetheless, this process presents some difficulties: elevated machining times, tool costs and a surface integrity dependent on machine kinematics.  
As it was mentioned previously, Ti and Ni alloys are the materials used for these types of components, and they are characterized by their low machinability, so Figure 8 shows the expected material removal rates and cutting conditions ranges recommended for these materials and components [4; 21].  
Figure 7: Impeller blades repairing process through hybrid manufacturing.  
Even though the principal impeller application manufactured by this process is the aeronautical engine, there are many applications not as popular that should be highlighted: high-speed watercrafts and motorboats, washing machines, vacuum cleaners, water propellers and ventricular assist devices.  
In the case of medium-sized blisks, milling is the most usual manufacturing process, especially for titanium alloys and Inconel(r)718. These components are commonly placed in the medium- and high-pressure turbine compressors for aeronautical engines. Being located in the compression areas, both the high- and the low-pressure zones from the engines, materials need to present good resistance properties to high temperature and pressure; therefore, they are made of difficult-to-cut materials, such as forged materials, cast blades, monocrystalline materials, etc. At this time, new challenges are presented related to materials because the traditional Ti6 Al4V tends to be replaced by Ti6242 and Ti6246 alloys, as well as the Inconel(r)718 by the DA718.