Ablation, Drilling and Micro-Cutting (LiM 2017)

Zero taper, fast drilling of high thickness metal parts
Mincuzzi, Girolamo; Faucon, Marc; Hamoudi, Thomas; Fleureau, Marie; Kling, Rainer

For material thickness up to nearly 1 mm, use of high average power, high repetition rate, ultrashort lasers jointly with
trepanning head (enabling both beam rotation and inclination) has been shown to be an effective tool to obtain holes
with high machining quality, zero or even negative taper, aspect ratio as high as > 10 and high throughput.
Nevertheless, this technological approach shows its limitations when material thickness higher than nearly 1 mm is
considered. Here a novel approach is proposed consisting of a top-down, hybrid (sequence of trepanning, drilling and
trepanning) drilling process. By systematic variation of process parameters (beam inclination angle, focus re-positioning,
etc.) this approach has been optimized to drill zero tapering holes in stainless steel 316 L having a thickness varying from
0.9 mm to 2 mm. Importantly, a zero-tapering hole with aspect ratio of 10 was obtained in a 2-mm thick sample with a
processing time which has been reduced to 32 s. We believe these results not only show the full potential of the
technological approach we utilised but can open the way for high power high repetition rate ultrashort laser to gain an
ever-ubiquitous diffusion into an increasing number of industrial fields.

Keywords: trepanning head, drilling, zero taper, high aspect ratio, femtosecond laser


Excimer lasers micromachining of low density inorganic material
Geoffray, Isabelle; Bourdenet, Rémy; Chicanne, Cédric; Théobald, Marc

CEA designs , s tudies and manufa ctures targe ts de dica te d to lase r e xpe ri ments . A ta rge t is composed of a wide range of
ma te rials tha t a re often thin, fra gile and requi ring hi gh -le vel mi cro-te chnology means . In this conte xt, las er mi cro-
ma chining processes offer re liable and accurate solutions, able to fulfill demanding s pecifications.
This presenta tion deals wi th tantalum oxide ae rogel (Ta 2O5) machining. This inorgani c nanoporous ma te rial, combining a hi gh-Z ele ment and a qui te low density (0.5 g.cm-3), is of grea t inte rest for laser e xpe rime nts. This pape r shows how we a chi eved to shape this material with excimer laser, i n UV nanosecond re gime. The fi rs t pa rt of the s tudy consisted in compa ring the ablation ra tes obtained wi th A rF or KrF lasers , revealing slight differences of the ma te rial beha vi our and phenomena like incuba tion or sa tura tion. The n pa rame tri c opti mization has been performed, and will be described, resulting i n sub-millimetric 3D shapes (example of high -aspect ratio holes).

Keywords: excimer laser ; pulsed laser ; micro-machining ; target


Multi-axis positioning approach for precise sharpening of monolithic cutting tools by USP laser processing
Cermák, Adam; Kozmin, Pavel

Laser processing of monolithic cutting tools is widely discussed in many research papers, where complete monolithic
cutting tool (from stock material to final cutting tool) were processed. This kind of complete tool manufacturing is
suitable only for microtools due to big processing durations.
Therefore, a new multi-axis positioning approach using a tangential laser processing was designed. This approach
consists of algorithms for detecting of flute parameters for multi-axis trajectory and laser processing. Superstructure of
multi-axis positioning approach lies in its automation, where a recognition interface is used. This extended property of
flute detection, using features of analytical geometry, makes implementation of USP laser processing into production
chain more convenient. This multi-axis positioning approach is suitable for precise sharpening of cutting edges of ground
monolithic tools made of cemented carbides, where cutting edge radiuses are limited by grain size of substrate. It is also
applicable on preparation of thin coated layers (e.g. CVD-D). Cemented carbide as a cutting material, CVD-D layer as a
thin coating and different approaches of laser beam to the cutting edges were considered. A lot of variables of tangential
laser processing were examined in experiments. After optimal setting of laser parameters prepared cutting edge radius
rβ could be reached under 2μm and roughness of new facet is smaller than Ra < 0.2μm.

Keywords: axes synchronization, precise microgeometry, cutting edge preparation, USP Laser


Heat accumulation effects on efficiency during laser drilling of metals
Förster, Daniel Johannes; Weber, Rudolf; Graf, Thomas

Pulsed laser materials processing with pulse durations <10 ps might lead to direct sublimation or evaporation of the material resulting in very small thermal damage. However, it was shown that for Cu, Mg, Au, and Si the thermal load might be significant even for 60 fs pulses. The thermalized energy after the ablation process which remains within the material normalized by the applied energy is the so called "residual heat". The residual heat in multi-pulse processing of different materials with ultrashort pulses was investigated at low repetition rates for Al, Zn, and Pt and under influence of different environment. As multi-pulse processing is gaining importance in the industry, recent studies of the effects of residual heat concentrated on the processing of steel with respect to heat accumulation at higher repetition rates. Results of residual heat measurements during laser drilling of steel sheets of up to 1.5 mm thickness are discussed in the following. The pulse duration of the laser system was 10 ps, the repetition rate was varied in the range from 10 kHz to 300 kHz at constant pulse energy.

Keywords: Residual heat; Heat accumulation; Percussion drilling; Steel


High-speed process observation of pulsed laser drilling in non-transparent materials
Arnold, Thomas; Götter, Patrick; Wanke, Dominik; Weber, Rudolf; Graf, Thomas; Spörl, Johanna; Ota, Antje; Hermanutz, Frank

In previous studies dielectric or semi-conducting materials like silicon were used to get an insight into the pulsed laser drilling process. The process was analyzed at a wavelength at which the material is transparent. This method was very successful providing time-resolved information a bout the drilling progress or the formation of side-channels. However, at the moment there is no diagnostics a vailable which allows time- and space-resolve d observation of the drilling process in metals and other non-transparent materials. Within this study a method which allows to observe the pulsed laser drilling process when drilling in non-transparent materials is introduced. A glass plate is put in front of a sample. The laser is focused from top into the interface of these two pieces to process both, the sample and the glass plate. The drilling process is observed through the glass plate using a high-speed camera. With this setup it was possible to observe the drilling process in steel and to investigate the drilling progress. The formation of a side channel was observed during drilling of a ceramic sample.

Keywords: micro processing; laser drilling; process observation; non-transparent materials


High precision drilling with ultra-short laser pulses
Russ, Simone; Führa, Benjamin; Kahmann, Max; Andreev, Andrey; Hesse, Tim; Diego-Vallejo, David; Hammers-Weber, Patricia

Micro processing with ultrafast lasers has become a well-established technology during the last few years due to the availability of reliable and affordable industrial lasers and variety of processes for which they can be applied. Drilling of injection nozzles is of great interest for the automotive industry. Laser drilling of fuel injection nozzles has already been established in production lines. Injectors for diesel engines are more complex and have to withstand higher pressures than injectors for petrol. For the drilling process this means increasing requirements concerning the wall thickness and the hole diameter, which in turn leads to a more challenging processing. Taper free or even negative conical holes are of interest whereby the diameter should be smaller than 100 μm. To meet these needs the laser beam has to be moved and inclined during the drilling process. This can be reached by using a 5-axis system together with an USP laser. In this paper we report on high precision drilling with a TRUMPF TruMicro5070 (Femto Edtion) femto-second laser together with the SCANLAB precSYS 5-axis micro-machining sub system. In a first step, different drilling strategies were investigated regarding their advantages and disadvantages for the process. To reach holes with a high aspect ratio and high quality different drilling strategies were combined. During the research, two different challenging bore geometries were studied: cylindrical and negative conical holes. Additionally to the geometry of the holes the material thickness was varied from 0.5 mm to 1 mm. Furthermore, the processing limits regarding the smallest possible diameter were investigated.

Keywords: high precision drilling, femto-second laser, 5-axis micro-machining, high aspect ratio, cylindrical and negative conical holes


Picosecond-laser drilling limits for deep precision microholes in tool steel
Zahedi, Ehsan; Weber, Ruodolf; Freitag, Christian; Graf, Thomas; Wörz, Christoph; Umlauf, Georg

A novel approach using liquid CO2 for lubrication during the deep-drawing process requires conical microholes with
smallest diameters < 100 μm in > 6.7 mm thick tool steel. Ultrashort laser pulses are a very promising tool for drilling of
such deep, precision microholes. The capability of Femto- and Picosecond lasers for drilling microholes in virtually any
material is state of the art for holes with a depth of up to about 2 mm. However, to extend the depth it is crucial to know
the drilling limits with respect to depth. Furthermore, a significant part of each laser pulse is converted to heat, which
remains in the material. This heat is accumulated from pulse to pulse depending on the process parameters. If the
resulting temperature increase exceeds the melting temperature the hole quality is significantly reduced, which is
another important limit for laser drilling.
To determine the above-mentioned limits, we used near infrared laser pulses with a pulse duration of 10 ps to drill
through holes in tool steel samples up to a thickness of 8 mm. We will present the limits of ps-laser drilling regarding the
maximum achieved depth for a given pulse energy in the range from 250 μJ to 2 mJ and repetition rates in the range of
15 kHz to 300 kHz. Furthermore, forming tools were successfully drilled and used for CO2-lubricated deep drawn steel

Keywords: laser deep drilling; heat accumulation; high energy picosecond laser pulse; CO2 lubrication.


Ultrafast z-scanning for high efficiency laser micro-machining
Chen, Ting-Hsuan; Fardel, Romain; Arnold, Craig

The growing demand for micro-machined elements in scientific research and industry has created a need for high-efficiency laser micro- machining. A laser’s machining efficiency is highly sensitive to the relative locations of the beam and surface. Real-time control for beam delivery is time consuming and financially prohibitive for practical applications. Here, we propose an economical solution for high-efficiency micro-machining by combining rapid scanning of focal positions with rapid laser-firing.

Keywords: high efficiency micro-machining ; ultrafast z-scanner; TAG lens


Influencing the ablation efficiency in ultra-short pulse laser micro structuring by using a deformable mirror for beam shaping
Smarra, Marco; Dickmann, Klaus

The increasing average laser power and especially the increasing pulse energies of ultra-short pulse laser systems
enhance the demand of new processing strategies for an efficient ablation process. Polygon scanners were developed to
offer high scanning speeds which are often required in combination with a high pulse repetition rate. An increase of the
pulse energy raises the formation of substructures and therefore roughness on ablation ground instead of enhancing the
amount of removed material. The optimal laser fluence for material processing can be determined by material
properties like the optical penetration depth and the threshold fluence. In this study it is shown that the laser fluence
can be optimized by using a beam shaping tool. The tool used in this study is a deformable mirror with 35 individual
controllable segments and a closed mirror surface. These type of beam shaping elements are one of the most suitable
tools for high power laser applications due to the absence of intensity losses due to diffraction or absorption. The mirror
deformation leads to a modulation of the incident wavefront and therefore to a variation of the beam shape in the focal
plane. These spot shapes were used for micro structuring of metal sheets. The structured areas were analyzed
considering the depth, roughness and edge angles. Based on this information a high precision determination of the
ablation efficiency is possible. Finally, these results were used to demonstrate various practical structuring examples

Keywords: micro processing; ablation; system technology; deformable mirror


Fabrication of PMN-PT piezoelectric actuators with ultrashort pulses
Piredda, Giovanni; Stroj, Sandra; Martín-Sánchez, Javier; Trotta, Rinaldo; Rastelli, Armando

Lead-magnesium niobate lead-titanate (PMN-PT) crystals have outstanding piezoelectric properties, which make novel
applications in acoustics or as transducers possible.
In the literature several methods for PMN-PT devices fabrication have been proposed, such as chemical etching, excimer laser ablation and ion milling. We demonstrate the use of green femtosecond laser pulses for the fabrication of PMN-PT actuators, and show several
key features of the fabrication method; absence of cracks, vertical and smooth device walls are essential requirements
for device functionality. We show optimized fabrication parameters that allow the fabrication of actuators in a short
time; finally, we present working devices which make clear the role of each fabrication requirement.

Keywords: piezoelectric crystals; ultrashort pulses; ultrafast; laser; cutting; microfabrication; actuators;


Incubation effect during laser irradiation of stainless steel with bursts of fs-pulses
Giannuzzi, Giuseppe; Gaudiuso, Caterina; Ancona, Antonio; Lugarà, Pietro Mario

A thorough experimental investigation of the incubation effect influencing the ablation threshold during irradiation of
steel samples with bursts of femtosecond laser pulses is presented. The bursts were generated using a cascade of
birefringent crystals splitting pristine 650-fs laser pulses at 1030 nm wavelength into a tunable number of up to 32 sub-
pulses with time separations in the picosecond range.
In Burst Mode (BM) processing we found that the threshold fluence strongly depends on the burst features. These results have been compared to the case of multi-shot ablation in Normal Pulse Mode (NPM), finding that the models describing incubation in NPM are not applicable to BM. In particular, while the threshold fluence estimated in NPM has a unique value, in case of BM we found different values of ablation thresholds according to the total number of sub-pulses impinging on the sample surface. Therefore, a modified incubation model has been introduced fitting the results obtained in BM, where the incubation coefficient depends on the burst composition.

Keywords: Ablation; Burst mode; Incubation; Femtosecond laser; Laser material processing


Selective ablation of titanium nitride film on tungsten carbide substrate using ultrashort laser pulses
de Rossi, Wagner; Oliveira, Eduardo Spinelli; Samad, Ricardo Elgul; Vieira Jr, Nilson Dias

Many machining tools use coatings on their cutting surface to improve the machining process and increase its useful life.
Due to damage or wear on the cutting edge, it is often desirable to remove this film for tool recovery. Doing this without
damaging the base material is not easy due to the small thickness of the coating and because its hardness is much
greater than that of the substrate.
In this work, the removal of titanium aluminum nitride (TiAlN) coating on tungsten carbide (WC) was done with the use
of femtosecond laser pulses. Complete film removal was obtained without damage to base material using a fluency far
below that of the film ablation threshold for a single pulse. A decrease in this threshold was obtained by applying a high
number of overlapping pulses with a low fluency until the incubation effects reduced the film damage threshold to a
value slightly below to that of the substrate. With this technique precise and clean results were obtained and are
reported in this work.

Keywords: laser ablation; ultrashort laser pulses; thin film, selective ablation.


Investigations on ultra-short pulse laser processing of ceramics using statistical methods
Friedrich, Maria; Völlm, Kristina; Wächter, Sebastian; Bliedtner, Jens

Since ultra-short pulse lasers have been commercially available, they have proven to be a perfect tool for micro
processing. The precise and gentle processing caused by an almost non-thermal ablation is suited for a wide variety of
materials, even for dielectric, brittle-hard substrates such as ceramics.
However, many questions regarding the beam-material-interactions have still not been entirely clarified. In order to reveal and optimize the processes happening during surface ablation, investigations on alumina have been executed.
The particular aim was to examine a large number of parameters regarding their influences on the ablation process as
well as their interactions among each other. In the case of ultra-short pulse laser processing, there are, in addition to the
material properties, more than ten process parameters, for instance pulse energy, wavelength or repetition rate.
In order to reduce the scope of experiments to a minimum, Design of Experiments (DoE) has been applied to 2.5D surface ablation. Subsequently, a sensitivity analysis of the experimental data has been performed to identify significant parameter correlations. To describe the ablation process in a realistic way, different meta-models of optimal prognosis
were created, which have been evaluated by quality and physical validity.
The results show how the process parameters influence the removal rate and the surface characteristics, such as roughness and morphology. On the one hand, the experiments contribute to the basic process understanding, for
example how the surface evolves as the material deepens or how the threshold fluence shifts with increasing scanning
repetitions. On the other hand, an optimization of the target parameters has been achieved. Whereas the removal rate
has been decisively maximized by a proper selection of the line distance, the roughness could be minimized for a certain
pulse overlap which strongly depends on the fluence.

Keywords: ultra-short pulses; ablation; surface structuring; DoE; ceramics


Laser micro drilling of wing surfaces for hybrid laminar flow control
Uchtmann, Hermann; Haasler, Dennis; Gillner, Arnold

Hybrid laminar flow control (HLFC) technology can lead to a significant reduction of up to 10 % of fuel consumption for
large passenger aircrafts. A reduction of fuel consumption not only decreases the operative costs but it also reduces the
environmental impact of the aircraft. Therefore, areas at the front area of the wings are being perforated by millions of
micro holes with diameter of approx. 50 100 μm. A part of the airflow is sucked through these holes so that the airflow
over the wing surface can be controlled to be laminar instead of turbulent. Another advantage is the anti-icing possibility
on cold winter days wherefore hot air is blown through these micro holes before and during take-off and landing. Thus,
time-consuming manual anti-icing processes of the wings are no longer necessary.
The challenge is the productive manufacturing of millions of micro holes. Fraunhofer ILT developed a high productive “on-the-fly” laser drilling process with drilling rates of up to 200 holes per second in 1 mm thick titanium sheets. A
pulsed singlemode fiber laser source is used in combination with a drilling optic with coaxial process gas supply. Each
laser pulse with durations in the range of 500 μs drills one micro hole. The velocity of the relative movement of the
drilling optic and the work piece and a constant repetition rate of the laser source of e.g. 200 Hz set the pitch between
any two holes. By implementing an interferometric based measurement system for controlling the distance between
drilling optic and work piece the process has successfully been transferred to 3D components such as wing
demonstrators with internal structures.

Keywords: Laser drilling, hybrid laminar flow control


Picosecond laser processing for fast cross sectioning and preparation of TEM lamella prior to ion milling polishing
Sikora, Aurélien; Fares, Lahouari; Adrian, Jérôme; Goubier, Vincent; Delobbe, Anne; Corbin, Antoine; Sarnet, Thierry; Sentis, Marc

Microchips are more and more complex and designed in thick 3-dimensional packages. Direct observation of the inside of the device by electron microscopy in order to check the manufacturing quality or to analyse the origin of failures requires the removal of huge quantity of matter. The current techniques, such as plasma Focused Ion beam, provide high surface quality but at the cost of a low matter removal rate (~104 μm3/s), requiring hours of processing. This problem becomes worse for the realisation of TEM lamella for which double cavities must be engraved. Therefore, other techniques such as laser engraving are envisioned in order to accelerate the process (Halbwax et al. 2007, Kwakman et al. 2013, Sikora et al. 2016). In this work, picosecond laser micromachining at 343, 515 and 1030 nm was investigated for
the realization of cross sections and lamella. By working at a modest repetition rate (200 kHz), much higher matter
removal rates could be achieved (~106 μm3/s) reducing the cavity engraving time to several seconds (
Sikora et al. 2016).
Besides, smooth and almost vertical sidewalls were obtained by tuning the applied fluence and the number of shots. The
method is demonstrated for cross sectioning of highly heterogeneous devices such as microchips and for the realization
of thin lamella in silicon.

Keywords: engraving; picosecond laser; cross section; TEM lamella; silicon;


Compact and ultra-flexible gauss to top-hat beam shaping with aspheres
Moehl, Anna; Wickenhagen, Sven; Fuchs, Ulrike

Two refractive beam shaping designs are presented. Both are characterized in a very compact set-up and a flexible
application area. The input and output beam diameter can be adapted easily to the parameters of an existing set-up.
Furthermore, some valuable results of the characterization of both manufactured systems are shown.

Keywords: laser; beam shaping; gauss; top-hat; focused; aspheres


Towards near-net shape micro-machining of aerospace materials by means of a water jet-guided laser beam
Diboine, Jeremie; Martin, Ronan; Bruckert, Florent; Diehl, Helgi; Richerzhagen, Bernold

Guiding light with a thin, cylindrical water jet provides a range of advantages in laser machining such as reduced heat affected zone, cleaner kerfs, focused light over several centimeters in depth and improved material removal rate (MRR). Pushing the technology further requires a thorough understanding of its behavior, which adds the behavior inherent to water jets to the already complex parameter space of laser machining. In an attempt to simplify process description and to estimate the expected performance, a semi-empirical approach was selected based on physical considerations and experimental observations. The proposed model is fitted using a database of milling and drilling experiments on aerospace nickel alloys and thermal barrier coating (TBC) ceramic materials. It is then tested to mill shapes with controlled depth and angles using arbitrary sets of machining parameters. The experimental results are discussed. The obtained experimental data has provided a strong contribution to both the theoretical understanding and the exploration of actionable optimization measures for the Laser MicroJet® process.

Keywords: laser; water jet; ablation; drilling; modelling


Optimization of key parameters for efficient processing with 100 W femtosecond laser
Audouard, E.; Mincuzzi, G.; Letan, A.; Gaudfrin, K.; Mischichik, K.; C. Hönninger; Kling, R.; Mottay, E.; Lopez, J.

Thanks to high a ve rage powe r, 100 W and more , and high repetition rate , it is possible today to achieve high throughput with femtosecond lasers , providing that the operating parameters are finely tuned to the application. Femtosecond lasers play a key role in these processes, due to their ability to high quality micro processing thanks to their specific shape of deposited energy. A clear unde rs tanding of all the processing steps necessary to optimize the processing speed is a main challenge for industrial development. Indeed, laser parameters are not independent of beam enginee ring devices and their synchronization with the laser (beam deflection, beam scanning and beam shaping). Pulses energies, laser repetition rates have to be precisely settled a ccording to the time and spatial sequences of pulses superposition resulting from beam delivery on the sample. A bad choice of parameters can lead to energy waste and poor process efficiency.

Keywords: femtosecond processing, High speed processing, High power processing, beam engineering, processing optimization.


Galvanometer scanning technology and 9.3µm CO2 lasers for on-the-fly converting applications
Hemmerich, Malte; Darvish, Mohammad; Conroy, Justin; Silta, Ray; Vo, Hai; Luo, Xi; Galdamez, Rinaldo; Li, Jin

Digital converting processes are used to transform a roll of material into a different form or shape and provide the
flexibility to deliver unique designs or changes on-the-fly, unlike traditional mechanical processes. Tremendous progress
has been made in the field of digital printing; its increased adoption requires that converting processes also be more
flexible and cost-effective while delivering high cut quality. Due to the high cost of storage and maintenance of a
plurality of conventional dies and long set up time, using CO2 lasers in combination with fast and precise laser scanning
has proven to have great potential in paper and cardboard processing, flexible packaging and label cutting. At the same
time, the capability to control the laser beam power density delivered on the material processed is critical to achieve
high quality finish goods.
In this paper, we are showing the capabilities of an all-digital galvanometer scanner in combination with a highly
frequency stable CO2 laser that provides stable laser power density by modulating the laser power in coordination with
beam scanning speed. Our system also demonstrates high scanning speed of more than 10 m/s and a focal spot size of
less than 150μm.

Keywords: 9.3μm CO2-Laser; Uniform Laser Density; Digital Galvanometer Scanning Technology; Digital Converting; Cutting; Drilling;


Laser manufacturing of carbide micro milling tools
Pfaff, Josquin; Hajri, Melik; Häfner, Claudio; Wegener, Konrad

Pulsed laser ablation is increasingly being used for the manufacturing of cutting tools, both with undefined and defined
cutting edges. The machining of cutting inserts made of ultra-hard material with pulsed lasers is an industrially
established process, while the production of more complex geometries, such as fluted tools is being developed.
Ultrashort-pulsed laser processes, contrary to conventional tool manufacturing processes, are not based on the
mechanical removal of material and are thus free of wear or cutting forces. Especially for the production of micro tools
are cutting forces detrimental: the resulting deformations need to be compensated and can lead to tool failure during
production. The absence of forces make laser processing an interesting alternative to the grinding of micro tools.
In this paper, processes for manufacturing carbide micro cutting tools with defined cutting edges using an ultra-short-pulsed laser are detailed. Processing strategies to machine a tool using a setup consisting of four mechanical and two optical axes are developed. Tungsten Carbide (WC) single-edge micro milling tools-with Ø 200 μm-are machined using a
laser source (τp<12 ps, λ= 532 nm) with an average power of Pmax= 4 Watt. By using self-limiting laser ablation finishing
processes, high surface quality and geometrical accuracy are achieved. No significant thermal damage of the material by
the laser processes can be observed. Milling experiments in low alloyed copper with the laser produced tools
demonstrate the applicability of such technology for the manufacturing of WC micro milling tools.

Keywords: ultrashort-pulse laser ablation; carbide micro milling tools; tungsten carbide; tangential laser processing


Rotary 2.5D pulsed laser ablation
Warhanek, Maximilian Georg; Pfaff, Josquin; Gysel, Johannes; Wegener, Konrad

2.5D volume ablation, i.e. the layer-by-layer material removal of three-dimensional geometries by pulsed laser ablation,
is a widespread process applied in research and industry. It allows for the manufacturing of concave geometries with
little constraints regarding geometric complexity, dimension and workpiece material. This has expanded the limits of
modern manufacturing capabilities especially for micro-features with challenging accessibility and the shaping of hard to
machine, brittle and ultrahard materials, such as diamond.
This paper presents the extension of 2.5D volume ablation process to rotary workpieces. While planar 2.5D volume ablation strategies are subject of extensive research and are supported by a variety of commercial hardware and
software solutions already, rotary applications are limited. To date, e.g. the helical grooves on drilling tools or threads
are processed by stitching planar 2.5D volume segments at different rotary positions. The process-efficiency can be
improved and possible irregularities at the stitching areas can be avoided by continuous cylindrical layer-by-layer
material removal.
A number of different strategies are analyzed with regards to processing time considering the different dynamic
constraints of mechanical and scanner axes. A synchronized control setup for the rotary motion of a cylindrical
workpiece and the scanning motion of the optical axes is implemented to enable the favored strategy. Furthermore, a
comprehensive software tool for the generation of laser-beam paths from the CAD data of arbitrary rotary workpieces is
Experiments show the functionality of hardware and software for rotary 2.5D pulsed laser ablation. The processing
results validate the applicability of the chosen scanning strategy and show significant reduction in processing time
compared to according stitching processes.

Keywords: Pulsed-laser ablation, computer-aided manufacturing;


New picosecond laser technology for micromachining in microelectronics manufacturing
Bovatsek, Jim; Patel, Rajesh

The benefits of micromachining with shorter pulse durations (“ultrashort” pulses) have led to their increased use in a
diverse range of advanced manufacturing industries, including microelectronics, photovoltaics, light-emitting diodes,
flat/touch panel display, and medical devices. Picosecond lasers, in particular, are becoming increasingly well known
throughout various industries because of their ability to ablate material with reduced heat affected zones (HAZ) as well
as their ability to generate nonlinear absorption and thereby cleanly machine transparent materials both at and below
the surface. Unfortunately, picosecond laser sources have historically been relatively inflexible, large, costly and
unreliable, significantly limiting industrial adoption.
In this work, we present micromachining results using Spectra-Physics’ IceFyre™ industrial picosecond laser. This laser generates high pulse energies along with TimeShift™ psa versatile programmable burst mode capabilityand has a
wide adjustability of repetition rates in a compact package with industry-leading cost-performance. The benefits of
burst mode machining of stainless steel has been studied. Also, the high energy pulses available with IceFyre are shown
to effectively ablate hard brittle materialssuch as glasses and ceramicswith excellent quality.

Keywords: picosecond laser; ablation; burst; efficiency


Laser based surface and post coating treatment of cutting tools
Michel, Sebastian; Bathe, Timo; Iovkov, Ivan; Biermann, Dirk; Kuhle, Bastian; Kanitz, Alexander; Esen, Cemal

Higher demands on the workpiece quality in the mobility sector result in the necessity to extend the capabilities of
cutting tools when manufacturing parts made of carbon fiber reinforced plastics (CFRP) or Inconel 718. Therefore, an
approach of a laser ablation process was examined to improve the machining behavior of diamond coated tools when
machining CFRP and to adjust the coolant supply of solid carbide drills when machining Inconel 718. To evaluate the
wear behavior and mechanisms when machining CFRP, non-coated tools and also tools with a partly removed diamond
coating were used to examine the abrasive wear mechanisms under orthogonal cutting conditions. Based on the findings
of these investigations, it can be shown that the cutting edge abrades rapidly due to the high abrasiveness of the
imbedded carbon fibers. As a result of this wear mechanism, the rounded cutting edges lead to diminished workpiece
qualities. To improve the machining behavior of those tools, an approach of a laser ablation method, using a
femtosecond based laser beam, was utilized to remove the diamond coating. Additionally, investigations with a modified
flank face for drilling Inconel 718 were carried out. The modified flank face was generated by the same laser ablation
process in order to increase the tool performance significantly. The integrated groove limits the width of flank wear and
allows an improved cooling supply of the thermally high loaded peripheral corner.

Keywords: Cutting tools; laser ablation; CFRP; Inconel 718


Direct laser interference patterning: from fundamentals to industrial applications
Kunze, Tim; Lasagni, Andrés Fabián

Direct Laser Interference Patterning (DLIP) is a method that implements physical phenomena of interference to produce
periodic structures on surfaces by transferring the shape of the pattern directly to the material by selective laser
ablation. Recent developments of the DLIP method will be presented in this talk. The structuring of thin metallic films
and bulk materials using nano- and picosecond laser systems will be introduced by going through different optical setups
and industrial systems which have been recently developed. Several technological applications including tribology,
biological interfaces, thin film organic solar cells and electrodes as well as decorative elements and safety features will
be discussed and summarized in this presentation.

Keywords: Selective Laser Ablation; Direct Laser Interference Patterning; Surface Functionalization; High-Speed Structuring