JEC COMPOSITES MAGAZINE - Issue #135 - July/August 2020 - 30

FEATURE
maintenance

Automated adaptive machining
of aircraft composite structures

Dr. Henrik Schmutzler,
Head of Composite Manufacturing
Lufthansa Technik AG
Bernd Mann,
CTO
iSAM AG

L

ufthansa Technik is the leading provider of aircraft maintenance, repair,
overhaul and modification services
for civil aircraft, from commercial to VIP
and special mission aircraft. The Airframe
Related Components (ARC®) business
unit repairs and overhauls thrust reversers,
radomes and other structural composite
components. Serving all commercial aircraft
and nacelles, the variation in work scopes
is vast even though some specific parts are
repaired frequently. However, the variations
in part geometry after longer flight cycles
vary to a significantly higher degree than the
tolerance requirements to repairs, which in
some cases are in the range of 0.1 mm. To

The use of automation is not widespread in aircraft maintenance
due to the challenges that arise from the complexity of the tasks
for structural components. Different composite components are
in use for each aircraft type and engine configuration. In service,
they exhibit different damage zone geometries in different
locations. An adaptive automated machining system was
developed by Lufthansa Technik AG and iSAM AG to meet this
complexity and still meet challenging accuracy requirements.

handle this complexity, a high-accuracy
robot was equipped with a 3D scanner and
a spindle in order to perform a multitude of
adaptive repair operations.
Current situation
Repairs of composite aircraft structures are
currently conducted manually.
This is very labour-, cost- and time-intensive, with limited accuracy and repeatability.
As a result, bonded repairs of primary
aircraft structures (e.g. fuselage) are limited
in size. Furthermore, the manual processes
used limit the repair strategies, leading to
technically unnecessary high material usage.
The solution
The developed automated adaptive robot
system can be applied to a multitude of
repair processes in aviation maintenance,
repair and overhaul (MRO). It covers the

Intuitive programming
and use of the adaptive robot system

30

jec composites magazine / N°135 July - August 2020

following processes:
-	 scarfing;
-	 removal of one skin and honeycomb
core material from sandwich structures;
-	 transfer of drill holes and edges to oversized and undrilled replacement parts.
All of these generic processes take the part's
specific geometry into account through
an adaptive algorithm that plans the robot
path based on 3D scan data. Due to the
geometric and operational versatility of
the system design, these processes can be
transferred to further aircraft parts easily
as the key functions have already been developed. The developed stationary system
can thus be employed in any larger MRO
facility dealing with composite parts. The
system changes milling tools and drills in
an 18-piece tool changer. Labour efficiency,
reduced material use, faster turnaround
times and reduced numbers of spare parts in
combination with higher safety for workers
and products make the developed system
cost effective on a holistic level.
In the course of the project, Lufthansa
Technik detailed all part-specific repair
processes down to single process steps, parameters and tolerances considering repair
process alterations from manual processes
which became feasible in an automated
solution. iSAM AG designed, developed
JEC COMPOSITES MAGAZINE - Issue #135 - July/August 2020

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