Blisk Production of the Future - MTU Aero Engines

Linear friction welding (LFW) has proven to be
a suitable method to produce the highly
stressed joint between the blades and the disk
and is now used in production. Further development
efforts in this field are mainly targeted
at the machine technology to achieve higher
flexibility with respect to the various component
geometries to be joined.
Since the LFW technique calls for highly engineered
machinery and presupposes certain
geometric conditions regarding the components
to be produced, the next generation of
blisk joining techniques is presently being developed:
the inductive high-frequency pressure
(IHFP) welding process.
Figure 6: Detail parts and
blisk joined by LFW
Here, the energy required to heat the materials
to be joined is produced by high-frequency
alternating electromagnetic fields so that the
complicated machinery needed in the LFW
process to produce the mechanical vibrations
and high joining forces is no longer required.
Another benefit of the technique is that the
component proper is subjected to lower
stresses during welding.
1
4
3
2
1= HF generator
2= Welding equipment
3= Hydraulic system
4= CNC control unit
Figures 7 IHFP welding machine
1
Figure 8: section through a IHFP welded joint.
Figure 9: Simulation of the heating process
during IHFP welding
Presently, the technology is being matured for
common joints on titanium materials and crosssections
from the fan area to the low-pressure
compressor. In the process, a capable simulation
of coil / alternating field is used which is
particularly suited for the component geometry
and significantly reduces parameter testing.
3.2.2 Milling
At MTU Aero Engines, milling is the most
commonly used technique to produce blisk
airfoils. In this field, a holistic approach to the
milling process—machine, setup, milling strategy,
tooling, tool holders, coolant-lubricant,
etc.—helped achieve considerable savings. A
significant contribution came from the MTUpatented
circular stagger milling process.
While with conventional milling the angle of
contact may be up to 180°, this angle is limited
to 30° to 60° with circular milling. This reduces
the cutting forces and increases the material
removal rate by means larger cutting depths
and higher cutting speeds.