LASER BEAM 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. Reinhart Poprawe

Steinbachstraße 15

52074 Aachen, Germany

Phone +49 241 8906-0

Fax +49 241 8906-121

info@ilt.fraunhofer.de

www.ilt.fraunhofer.de

Fraunhofer ILT – Short Profile

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

technology, 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.

Subject to alterations in specifications and other technical information. 04/2016.

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At pulse durations of less than 10 ps, the material evaporates

completely, and there is almost no heat transfer into the

workpiece. With proper movement of the laser, drill holes can

be created without leaving melt layers on the drill hole wall.

Through the use of related systems technology, high quality

cylindrical and conical drill holes can be created that feature

high aspect ratios.

Application Areas

Due to the high intensity of the laser pulses, nearly all materials

such as metals, ceramics, semiconductors, CFRPs, plastics,

as well as multilayer systems made using these materials can

be drilled with great precision. Areas of application include

the making of air-cooling holes in turbomachinery components

such as blades or combustion chambers, drill holes for fuel

filters or injection nozzles, and ventilation holes for injection

molds in tool manufacturing.

Plant and Systems Engineering

Aside from its process technology work, Fraunhofer ILT

also develops the systems necessary for the industrial

implementation of these drilling methods. This includes

the development of specialized helical drilling optics with

high-speed local laser beam modulation, in addition to drilling

process integration within automated production systems.

Equipment

Fraunhofer ILT has a number of modern laser systems

used for laser drilling. These include:

• Long-pulse lasers (pulse durations µs - ms) such as

- IPG fiber lasers with 6 kW peak output power

- IPG single-mode fiber lasers with 1.5 kW peak

output power

• Short-pulse lasers (pulse durations ns - µs) such as

- Edgewave double-pulse laser with 2 x 40 W mean output,

pulse duration 2 - 10 ns, 50 kHz

• Ultrafast lasers (pulse durations fs - ps) such as

- Amphos 500 with 400 W mean output, pulse duration

0.7 - 8 ps, repetition rate up to 54 MHz

- Trumpf TruMicro 5270 with 60 W mean output,

pulse duration 7 ps, repetition rate 400 kHz

For optical beam formation, Fraunhofer ILT also offers drilling

optics with focal lengths of 70 to 300 mm, helical drilling optics,

and various scanning systems.

Contact

Dipl.-Ing. Hermann Uchtmann

Telephone +49 241 8906-8022

hermann.uchtmann@ilt.fraunhofer.de

Dr. Arnold Gillner

Telephone +49 241 8906-148

arnold.gillner@ilt.fraunhofer.de

The Method

Depending on component thickness as well as required

quality (precision) and productivity (drilling duration), holes

of approximately 1 µm to several millimeters in diameter are

drilled into the workpiece by means of single pulse drilling,

percussion drilling, trepanning, and helical drilling. The follow-

ing table shows the distinctions among the various drilling

methods with respect to diameter, depth and duration.

Diameter Depth Duration

Single-pulse drilling 40 - 700 µm < 2 mm < 1 ms

Percussion drilling 50 - 700 µm < 20 mm 0.1 - 20 s

1 - 50 µm < 1 mm < 1 ms

Trepanning 0.3 - 10 mm < 10 mm 1 - 20 s

Helical drilling 10 - 200 µm < 2 mm > 10 s

Single-pulse drilling can be performed “on the fly,” so that

up to 300 holes per second with a diameter of 60 µm can

be drilled into metal sheets of 1 mm in thickness. Trepanning,

which involves relative movement between the workpiece

and the laser beam, is used for drill hole diameters larger than

approximately 300 µm. Helical drilling is used to create holes

that have both highly precise geometry and superior

metallurgical quality. Laser drilling is an alternative to methods

such as electron beam drilling, electrical discharge machining,

electrochemical drilling and ultrasound drilling. The use of

“light as a tool” is preferred when the manufacturing process

requires drill holes with diameters of approximately 1 to

500 µm and high aspect ratios (> 1:20) to be made under

difficult conditions, such as those involving large inclination

angles to the workpiece surface, or materials of high hardness

(e.g. nickel-based alloys). Challenges exist with respect to the

minimization of melt layers and the avoidance of micro cracks

in the drill hole wall.

Physical Basis of the Process

Laser drilling methods can be distinguished into melting-

dominated and evaporation-dominated methods. At pulse

durations ranging from microseconds to milliseconds, the ma-

terial is largely melted by the laser, a small portion evaporates.

The resulting steam pressure expells the melt out of the drill

hole. This drilling process is highly productive; however, melt

layers with thicknesses of up to 100 µm still adhere to the

drill hole walls.

LASER BEAM DRILLINGBy laser radiation holes can be dri l led with diameters ranging from less than one micrometer to several

mil l imeters while maintaining the same dri l l ing depths. The Fraunhofer Inst itute for Laser Technology ILT is

developing several drill ing processes ranging from fundamental research to industrial systems implementation.

Application areas for laser dri l l ing include injection nozzles, venti lat ion holes, air-cool ing holes, contact

dri l l ing and f i l ter holes.

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3 Laser-drilled coupling element.

4 Fraunhofer ILT helical drilling optic.

5 Individual drill hole in CFRP

preform for functional elements.

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Cover: Laser drilling of a jet-nozzle segment.

1 Laser drilling of a nozzle guide vane element.

2 Helical drilling of nozzles

for CO2 air conditioners.