SUCCESS STORY – Good Vibrations for Die-Sinking EDM-- Steffen Arnold --Good Vibrations for Die-Sinking EDM
Piezo Actuators Accelerate Microstructuring

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

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SUCCESS STORY – Good Vibrations for Die-Sinking EDM-- Steffen Arnold --Actuators based on the piezo effect move heavy loads withresolutions in the sub-nanometer range and response times
below one millisecond, enabling dynamic operation at highscanning frequencies. Moreover, since they have no moving
parts in the conventional sense, piezo actuators are not only
very reliable, but also are maintenance-free. Diverse
applications, ranging from medical and metering technology,
to photonics, semiconductor technology, automation andproduction technology benefit from these characteristics. In
all these applications, piezoceramic actuators contribute toadvances in technology. For example, when die-sinking EDM
is used to produce precision components, piezo actuators
help to drastically shorten the production times.

Fig. 1

Sonodrive 300 vibratory spindle (Figure: ICT-IMM)

Fig. 2A hole 64 µm in diameter produced with a die-sinking EDM
machine equipped with a vibratory drilling spindle. The deviationfrom concentricity and cylindricity of the hole is in each case only
1 µm (Figure: ICT-IMM)

Fig. 3A hole only 20 µm in diameter produced with a die-sinking EDM
machine equipped with a vibratory drilling spindle (Figure: ICTIMM)

The increasing complexity of products and processes requires
the production processes to constantly increase throughput,precision, geometric diversity and accurate repeatibility. At
the same time, the trend in automation is toward
miniaturization.
So it is hardly surprising that also in the field of die-sinking
EDM, microstructured precision components are now
manufactured, often in large piece quantities. Examples
include the manufacture of filter elements or injection
nozzles for the automotive industry. This in turn drives theneed for economizing production processes associated withmicrostructuring: Cost and resource efficiency play importantroles in this context.

Faster Die-Sinking EDM Operationswith a Vibratory Spindle
This topic has been taken up by the Institute forMicrotechnology in Mainz (ICT-IMM), which has become partof the Fraunhofer Gesellschaft in 2014. The Sonodrive 300(Fig. 1) is a serial-production vibratory spindle, which, in highprecision microdrilling operations, can cut machining times byup to 60 %, compared with standard equipment, employing apatented process (Fig. 2).
The spindle rotates and vibrates simultaneously, preventing
the particles produced in EDM from being deposited in thehole, thereby eliminating the need to machine them again. In
conventional methods, this is unavoidable, because the small
electrode distances do not allow any flushing in themicrometer range. Depending on the material to bemachined and the job at hand, the vibration path can be set
and adjusted at any time during the process.

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

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SUCCESS STORY – Good Vibrations for Die-Sinking EDM-- Steffen Arnold --Compared with conventional methods, this delivers
substantial speed benefits, accelerating the entire production
process (Fig. 3). With a 0.2 mm diameter blind hole in a
1.0 mm thick VA material, the machining time in a test on a
EA12 die-sinking EDM machine from Mitsubishi Electric wasreduced from 200 to slightly below 80 seconds. On an Agie
Compact die-sinking EDM machine, the 0.2 mm diameter
through-hole in a 0.4 mm thick VA material was also obtained
60 % faster through the use of a vibratory spindle (Fig. 4).

Fig. 4

The new spindle principle combines high concentricity
tolerance of 1 to 2 µm absolute at a revolution of up to 3,500
min-1 with a high-frequency vibration of max. 300 Hz and astroke of up to 15 µm. The spindle fits in with allcommercially available die-sinking EDM machines as "Plug &Play" solution. The matching miniaturized wire pay-off device
likewise developed by ICT-IMM can also be easily integrated.
This allows the concentricity tolerance to be reduced to 1 µmabsolute.

With a 0.2 mm diameter blind hole in a 1.0 mm thick VA
material, the machining time in a test on a EA12 die-sinking EDM
machine from Mitsubishi Electric was reduced from 200 toslightly below 80 seconds (Figure: ICT-IMM)

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

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SUCCESS STORY – Good Vibrations for Die-Sinking EDM-- Steffen Arnold --Fig. 5On an Agie Compact die-sinking EDM machine, the 0.2 mm
diameter through-hole in a 0.4 mm thick VA material was alsoobtained approx. 60 % faster through the use of a vibratory
spindle (Figure: ICT-IMM)

Piezo Actuator Ensures Vibration
This technological leap for microstructuring has beenachieved by combining just the right amount of know-how
with components of high technical quality. A piezo actuator(Fig. 5) from the wide product range of Physik Instrumente(PI), headquartered in Karlsruhe, Germany, ensures vibration.
There are several good reasons why PI was chosen. The
creation of vibrations virtually is a classic piezo application,
because the piezo element starts to oscillate when an AC
voltage is applied. This means that piezo actuators convert
voltage directly into mechanical displacement. They achieve
typical travel ranges of a few hundred micrometers and highdynamics with frequencies of up to several hundred hertz.
The short response times of the piezos naturally also benefit
the application as a vibration drive.

Fig. 6

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

Compact piezo actuator: The generation of vibrations is a classic
piezo application (Figure: PI)

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SUCCESS STORY – Good Vibrations for Die-Sinking EDM-- Steffen Arnold --With its height of 25 mm at a diameter of 50 mm and its inneraperture of 25 mm, the selected actuator could also easily be
integrated in the vibratory spindle (Fig. 7).

There are still further arguments that speak for the use ofpiezos: Since the motion is based on crystalline solid-state
effects, there is no danger of abrasion with this technology
and there are no cogwheels, bearings or other mechanicalparts subject to wear.
This makes the piezo actuator maintenance-free. This is an
important characteristic, given that the piezo actuator
operates throughout the entire machining operation. It has
already proven its reliability, for example, in prototypes of thevibratory spindle, which has been operating at ICT-IMM forabout four years now, where it has by now completed
approximately 100 million operating cycles.
The piezo actuator is driven by an efficient, pulse-widthmodulated high-power voltage amplifier, also from PI (Fig. 8).
This amplifier is especially designed for the demands of lowvoltage piezo actuators. At a peak output power of up to 280
W and an average output power of up to 100 W, it can supply
and consume a peak current of up to 2,000 mA. This allows
dynamic operation of piezo actuators of high capacity at abandwidth up to the kilohertz range, more than is required
for micro EDM.

Fig. 8Fig. 7

The piezo actuator could be integrated into the vibratory spindle
in a space-saving arrangement (Figure: ICT-IMM)

Since piezos are also suitable for large loads, the permanent
motion of the spindle, whose weight varies between about
250 and 450 g, depending on the electrode, was no problem
for the small drive. If need be, it can lift more than one
kilogram. In contrast, electromechanical components forvibration generation were not an option for this application.
Due to their structure and larger dimensions, it would nothave been possible to integrate them into a useful unit forpractical use.

At a peak output power of up to 280 W and an average output
power of up to 100 W, the amplifier especially designed for thedemands of low-voltage piezo actuators can supply and consume
a peak current of up to 2,000 m (Figure: PI)

A vibration-supported electrodechuck also saves time
Piezo actuators have also been tested and proven in a
vibration-supported electrode chuck, which is also suitable as"Plug & Play" solution for all commercially available diesinking EDM machines and clamping systems and has a very
compact structure of 80 × 80 × 150 mm (Fig. 9).

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

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SUCCESS STORY – Good Vibrations for Die-Sinking EDM-- Steffen Arnold --These product areas are supplemented on the technologicalside by know-how in mechanical precision machining
processes, spark erosion, laser material machining and by aseries of chemical and physical structuring methods for use inclean rooms.

About PIFig. 9Thanks to the piezo actuator likewise vibration-supported: Theelectrode chuck Microvibe 300 for micro EDM (Figure: ICT-IMM)

Here, too, the 300-Hz vibrations at an adjustable stroke of up
to 15 µm accelerate the production process considerably:Thus, a long-term experiment with a hard-metal electrode(0.2 × 5 mm) and a sinking depth of 7 mm resulted in a timesaving of 70 %. Production time was reduced from 17 hours
and 20 minutes to 5 hours and 15 minutes. This can benefit
many areas of application. Typical examples aremicromachining, tool-making and mold-making and themanufacture of components for medical technology,
metrology and machine technology. Piezo actuators used as
vibration generators have thus made a substantial
contribution to advancing the technology of die-sinking EDM
to the lowest micrometer range.

About the Fraunhofer ICT-IMM inMainz

In the past four decades, PI (Physik Instrumente) with
headquarters in Karlsruhe, Germany has become the leading
manufacturer of nanopositioning systems with accuracies in
the nanometer range. With four company sites in Germanyand fifteen sales and service offices abroad, the privately
managed company operates globally.
Over 850 highly qualified employees around the world enable
the PI Group to meet almost any requirement in the field ofinnovative precision positioning technology. All key
technologies are developed in-house. This allows thecompany to control every step of the process, from design
right down to shipment: precision mechanics and electronics
as well as position sensors.
The required piezoceramic elements are manufactured by its
subsidiary PI Ceramic in Lederhose, Germany, one of the
global leaders for piezo actuator and sensor products.
PI miCos GmbH in Eschbach near Freiburg, Germany, is a
specialist for positioning systems for ultrahigh vacuum
applications as well as parallel-kinematic positioning systems
with six degrees of freedom and custom-made designs.

Authors

Fraunhofer ICT-IMM is building a bridge between basic
research and application, since the developments passthrough the institute from the concept stage to basic andapplication-oriented research and onto their implementationin customer-specific solutions with product relevance. In
doing so, they combine several thematic areas in which thereplies to economically and socially relevant problems of thefuture are worked out.
Fraunhofer ICT-IMM conducts research and development in
the core competences of Decentralized and Mobile Energy
Technology, Continuous Chemical Process Engineering,
Medical Sensors and Technical Sensors, Microfluidic Analysis
Systems and Nanoparticle Technologies. The knowledge anddevelopments gained from these fields are mainly applied in
the business divisions of Energy and Environment, Chemistry,Process Engineering, Aerospace, Safety and Industrial
Analytical Applications.

Dipl.-Phys. Steffen Arnold, Head of "Marketing and Products"
at PI (Physik Instrumente)
Dipl.-Ing. Frank Neumann, Department Head of Production
Processes at the Fraunhofer ICT-IMM in Mainz

Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws, www.pi.ws

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