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Laser driLLing
F R A U N H O F E R I N S T I T U T E F O R L A S E R T E c H N O L O g y I LT
DQS certified by
DIN EN ISO 9001
Reg.-No.: DE-69572-01
Fraunhofer-Institut
für Lasertechnik ILT
Director
Prof. Dr. Reinhart Poprawe M.A.
Steinbachstraße 15
52074 Aachen, Germany
Phone +49 241 8906-0
Fax +49 241 8906-121
www.ilt.fraunhofer.de
Fraunhofer ILT - Short Profile
With about 370 employees and more than 11,000 m² of usable
floorspace the Fraunhofer Institute for Laser Technology ILT
is worldwide one of the most important development and
contract research institutes of its specific field. The activities
cover a wide range of areas such as the development of
new laser beam sources and components, precise laser based
metrology, testing technology and industrial laser processes.
This includes laser cutting, caving, drilling, welding and soldering
as well as surface treatment, micro processing and rapid
manufacturing.
Furthermore, the Fraunhofer ILT is engaged in laser plant tech-
nology, process control, modeling as well as in the entire system
technology. We offer feasibility studies, process qualification
and laser integration in customer specific manufacturing lines.
The Fraunhofer ILT is part of the Fraunhofer-Gesellschaft with
more than 80 research units, 20,000 employees and an annual
research budget of over 1.8 billion euros.
Subject to alterations in specifications and other technical information. 09/2012.
Process Development
A high-intensity laser beam is capable of drilling holes with
great precision in virtually any material, from metals, ceramics,
semiconductors, diamond, and polymers to multilayer systems
fabricated from these materials. On the basis of fundamental
investigations, we develop new industrial laser drilling
processes with adapted energy deposition characteristics and
application-specific solutions for our partners. In particular
our activities are focused on processes that generate low
melt film thicknesses, such as helical drilling or the use of
material specific pulse burst techniques. Applications for these
processes include the drilling of cooling holes in turbine com-
ponents such as combustion chambers and rotor blades, the
drilling of vehicle fuel filters, and the perforation of nozzles
and vent holes in injection molding tools used in machine
tools and manufacturing systems.
Process Monitoring and Quality Control
The quality of laser-drilled holes can be monitored online using
a process control system developed by Fraunhofer ILT, which
uses coaxial sensors to observe the drilling progress of the laser
beam. It enables the operator to determine the breakthrough
point and other factors affecting quality such as recast or
closure of the hole. The laser output can also be regulated to
avoid damage to the rear wall when processing hollow parts.
Plant and Systems Engineering
In addition to its work on processes, Fraunhofer ILT also develops
special laser drilling systems to support the industrial implemen-
tation of the drilling processes. The institute’s activities in this
domain range from the development of special drilling optics
with high-speed spatial laser beam modulation to their integration
in existing manufacturing plants. The services provided include
customized machining solutions complete with process monitor-
ing and control, and extend to qualification of the customer-
ready process on the basis of short manufacturing runs.
Laboratory Equipment
• 7 ps laser (P = 50 W, λ = 1030 nm), 8-axis machine
• 10 ps laser (P = 50 W, λ = 1064/532/355 nm), 6-axis machine
• 10 ps Laser (P = 50 W, λ = 1064/532/355 nm), 5-axis machine
• 600 ps laser (P = 67 mW, λ = 532 nm), desktop system
• 10 ns laser (P = 36 W, λ = 532 nm) with helical drilling optics
• 10 ns excimer laser (λ = 193 nm), 4-axis machine
• 20 ns laser (P = 10 W, λ = 355 nm), 6-axis machine
• 40 ns laser (P = 10 W, λ = 355 nm) with interference optics
• 0.7/1.5 μs laser (P = 700/60 W, λ = 1030 nm), 5-axis machine
• Fiber laser (P = 1000 W, P = 300 W, λ = 1070 nm)
• Fiber laser (Ppeak = 6000 W, taupulse = 0.1 - 10 ms, λ = 1070 nm)
• 0.1 - 20 ms laser (Epulse = 100 J, λ = 1064 nm)
• 100 - 500 µs laser (Epulse = 1.5 J, λ = 1064 nm)
• High Perfomance Cluster with 612 CPUs and 2944 GPUs
contacts
Dipl.-Ing. (FH) Claudia Hartmann (Drilling Processes)
Phone +49 241 8906-207
Dipl.-Phys. Urs Eppelt (Simulation)
Phone +49 241 8906-163
The holes and the processes used to produce them are
subject to numerous, demanding quality requirements relating
to characteristics such as precision of the hole geometry,
reproducibility and productivity of the process. For this reason,
Fraunhofer ILT not only investigates the physical principles of
laser drilling. Aditionally we analyze and optimize the drilling
processes before implementing them in existing plants or
system technology. The investigations are supported by sensor
based process monitoring and diagnoses.
Laser Drilling Process
Depending on the required quality (precision) and throughput
(drilling time), different methods are used to produce
holes in the mm-to-μm range in different materials. These
drilling methods are single-pulse drilling, percussion drilling,
trepanning, and helical drilling. Laser drilling provides an
alternative to techniques such as electron beam drilling,
electrical discharge machining (EDM), electrochemical drilling,
and ultrasonic drilling. The laser is the tool of choice when
holes are required with a diameter of < 100 µm and a high
aspect ratio, machinig under difficult operating conditions like
defined angle of inclination, for holes in hard materials or for
the generation of special geometries. The advantages of laser
drilling are reproducibility, drilling speed, and the ability to
achieve high aspect ratios, i.e. the ratio of a hole’s depth to its
diameter. Challenges are the need to minimize recast, prevent
burring, and reduce the number and length of micro-cracks in
the wall of the drilled holes.
Physical Basis of the Process
The modeling and simulation of the laser drilling process
mainly serves two objectives. The first is avoiding recast on
the hole wall at pulse durations in the microsecond range.
The second is increasing the drilling speed at pulse durations
in the pico-second and nanosecond range. By analyzing the
drilling process at long (microsecond) pulse durations, the ILT
researchers are able to identify various phenomena that act
together to trigger and influence the formation of recast on
the hole wall. Additional factors that need to be taken into
account when the laser is operating at short pulse durations
and high intensity are the inertia of the melt, the reconden-
sation of the vapor, and the reflection of the laser beam
on the hole wall. The methodological approach involves
different types of numerical simulation. As well as studying
the analytical data and performing numerical calculations, the
researchers develop reduced models that are easier to analyze
and compute. Different methods including ray tracing, BPM
(beam propagation method), and FDTD (finite-difference
time-domain) analysis are used for the simulation of the
ablation process, the flow and condensation of vapor, and
the beam propagation.
Laser driLLingLasers can be used to dri l l holes ranging in diameter from several mil l imeters to less than one micro-meter.
The Fraunhofer Inst itute for Laser Technology ILT develops new laser dri l l ing techniques from the fundamen-
tal principles to their implementation in systems for use in industr ial-scale processes. Laser-dri l led micro
holes have many appl ications, including injection nozzles, venti lat ion and cool ing holes, metal l ized via
contacts, and f i l ters.
2 531 4 6
1 Laser drilling of a nozzle guide vane.
2 Shaped holes produced by 5-axis-trepanning.
3 Laser-perforated brass foil (thickness: 50 µm).
4 Laser-perforated thin glass.
5 Helical drilling optics.
6 Simulation of drilling with VoF methods,
(red: melt volume).