<jats:p>This article describes the design of a high cadence laser micro-drilling machine fo... more <jats:p>This article describes the design of a high cadence laser micro-drilling machine for the manufacture of large micro-drilled panels, which will form part of the leading edge of tail stabilisers on future commercial aircraft. This type of microperforated surface will be of great interest mainly in the aeronautical field, since it will improve the aerodynamic performance of the aircrafts supposing a fuel saving of up to 10 %. Manufacturing requirements demand through-holes of around 0.1 mm at a cadence equal to or greater than 300 holes per second. The quality of each of the holes, as well as the precision of the distance between them has been decisive in the design phase. The machine will be equipped with on-site measurement and defect detection systems to ensure the quality of the holes. Keywords: microdrilling, laser, titanium, machine, HLFC</jats:p>
Este articulo describe el diseno de una maquina de microperforado por laser de alta cadencia para... more Este articulo describe el diseno de una maquina de microperforado por laser de alta cadencia para la fabricacion de paneles microperforados de grandes dimensiones, que formaran parte del borde de ataque de los estabilizadores de cola de los futuros aviones comerciales. Este tipo de superficie microperforada sera principalmente de gran interes en el ambito aeronautico ya que mejorara el rendimiento aerodinamico de las aeronaves suponiendo un ahorro de hasta un 10 % de combustible. Los requisitos de fabricacion exigen realizar orificios pasantes de alrededor de 0.1 mm con una cadencia igual o superior a los 300 orificios por segundo. La calidad de cada uno de los orificios, asi como la precision de la distancia entre ellos ha sido determinante en la fase de diseno. La maquina dispondra de sistemas de medicion y de deteccion de defectos in situ para asegurar la calidad de los orificios. Palabras clave: microperforado, laser, titanio, maquina, HLFC
Hybrid Laminar Flow Control (HLFC) ist eine Schlüsseltechnologie, durch die der Luftwiderstand be... more Hybrid Laminar Flow Control (HLFC) ist eine Schlüsseltechnologie, durch die der Luftwiderstand bei Flugzeugen durch Perforation der Vorderkanten von Leitwerken und Tragflächen reduziert werden kann. Für eine qualitativ hochwertige Perforation von Blechen mittels Laser ist die Bohrzeit ein entscheidender Einflussfaktor. Durch eine Auswertung des Prozessleuchtens beim Laserstrahlbohren kann die für den Anwendungsfall geeignete Bohrzeit ermittelt werden. Hybrid Laminar Flow Control (HLFC) is a key technology for reducing air resistance in aircrafts by perforating the front edges of tails and wings. Drilling time is a decisive factor for high-quality perforation of sheets using lasers. By evaluating the process light during laser beam drilling it is possible to determine the appropriate drilling time for the application.
IOP Conference Series: Materials Science and Engineering
For conventional laser shock peening, the positive influence of compressive residual stresses on ... more For conventional laser shock peening, the positive influence of compressive residual stresses on fatigue strength is well understood. To protect the material’s surface from ablation, a sacrificial layer is applied. This, however, leads to an additional process step, which deteriorates its economic efficiency. Thus, laser shock peening without coating (LPwC) is more frequently investigated for industrial applications. However, LPwC increases the thermal impact on the material, which may provoke tensile residual stresses in the surface region. In this regard, understanding the influence of LPwC on the residual stress state and deriving a suitable state, e.g., for subsequent applications or forming operations, result in a design of experiment with numerous residual stress measurements. Residual stress-depth-profiles obtained by X-ray diffraction are time-consuming and cost intensive. Hence, a model is proposed to predict the residual stress-depth-profile of LPwC-processed thin sheets. ...
International Congress on Applications of Lasers & Electro-Optics
An important challenge for all processes based on laser material removal is the control of the pr... more An important challenge for all processes based on laser material removal is the control of the precision of the shape. This is so, because all methods are non-contact methods and the removal rate underlies certain influences depending on the exact processing conditions and material properties, making only limited prediction and control of the removal rate possible. In laser chemical machining the radiation locally initiates on a metal surface a thermo chemical etching reaction, which leads to selective material removal at high resolution. To achieve an intensive mass transport and also cooling of the work piece the etch liquid is injected co-axially to the laser beam directly into the irradiated area. Measurements of the electrochemical potential against a reference electrode show a cathodic shift of the potential as a function of laser power and feed rate while processing. These functional dependencies of the chemical potential on the processing parameters can be used to control the temperature driven reaction and therefore the removal rate, as the chemical potential can be more easily and instantaneously measured than the temperature.An important challenge for all processes based on laser material removal is the control of the precision of the shape. This is so, because all methods are non-contact methods and the removal rate underlies certain influences depending on the exact processing conditions and material properties, making only limited prediction and control of the removal rate possible. In laser chemical machining the radiation locally initiates on a metal surface a thermo chemical etching reaction, which leads to selective material removal at high resolution. To achieve an intensive mass transport and also cooling of the work piece the etch liquid is injected co-axially to the laser beam directly into the irradiated area. Measurements of the electrochemical potential against a reference electrode show a cathodic shift of the potential as a function of laser power and feed rate while processing. These functional dependencies of the chemical potential on the processing parameters can be used to control the temperature driven re...
Abstract To reduce the fuel consumption of large passenger aircrafts the hybrid laminar flow cont... more Abstract To reduce the fuel consumption of large passenger aircrafts the hybrid laminar flow control is a key technology. For drag reduction, several millions of holes with diameters around 50 µm at the leading edges are needed. In this paper, the perforation of such titanium sheets using the laser processes of single pulse and percussion drilling is presented. The single pulse technique is an “on-the-fly” drilling process using a pulsed fibre laser in combination with a drilling optic with coaxial gas supply. The percussion technique is a flexible drilling process using a q-switched fibre laser combined with a galvanic scanner.
Fourth International Symposium on Laser Precision Microfabrication, 2003
In this treatment method laser radiation, which is guided from a coaxially expanding liquid jet-s... more In this treatment method laser radiation, which is guided from a coaxially expanding liquid jet-stream, locally initiates a thermochemical etching reaction on a metal surface, which leads to selective material removal at high resolution and quality of the treated surface as well as low thermal influence on the workpiece. Electrochemical investigations were performed under focused laser irradiation using a cw-Nd:YAG laser with a maximum power of 15 W and a simultaneous impact of the liquid jet-stream consisting of phosphoric acid with a maximum flow rate of 20 m/s. The time resolved measurements of the electrical potential difference against an electrochemical reference electrode were correlated with the specific processing parameters and corresponding etch rates to identify processing conditions for temporally stable and enhanced chemical etching reactions. Applications of laser-induced liquid-phase jet-chemical etching in the field of sensor technology, micromechanics and micrmoulding technology are presented. This includes the microstructuring of thin film systems, cutting of foils of shape memory alloys or the generation of structures with defined shape in bulk material.
Laser-induced technological chemical processes can significantly contribute to the development of... more Laser-induced technological chemical processes can significantly contribute to the development of new methods for micro treatment of materials and hence to the broadening of the application spectrum of laser microtech-nology. In this paper three typical laser-activated chemical technological methods in liquids, gases and solids and their possible applications are presented and discussed: First, laser-induced liquid-phase jet-chemical etch-ing of metals. In this method, laser radiation which is guided from a coaxially expanding liquid jet-stream initiates locally on a metal surface a thermochemical etching reaction, which leads to a selective material removal at high resolution (< 1 µm) and quality of the treated surface. Second, local photon-plasma induced synthesis of thin film coatings. This technological method is based on thermochemical CVD processes taking place in a photon-initiated stationary plasma maintained in the electromagnetic optical field of a high-power cw-CO 2 la...
In this paper we report on a new method for the generation of shaped holes by dynamical variation... more In this paper we report on a new method for the generation of shaped holes by dynamical variation of the beam shape with a special optical system. It is based on using a q-switched Nd:YAG laser with 100 ns pulses at a wavelength of 1064 nm and an optical setup producing a photon tube. By variation of the beam divergence the shape of the photon tube can be variably modified. The optical system consists of a specially designed Galilean telescope and a focusing objective. The beam divergence can be changed in-situ by the Galilean telescope while processing. This enables to control diameter, length and angle of the photon tube. Shaped controlled structures are processed applying in-situ different optical fields which have been previously defined by simulations including aberrations and diffraction effects. As an example, the variable beam shaping resulted in through-going cylindrical bores as well as such ones with a defined conical inlet with respect to its taper angle and depth. Taper angles between 1 and nearly 50 degrees were realized by varying both the beam divergence and laser power. Furthermore, the variable beam shaping leads to improved and almost debris-free machining efficiency.
Laser-based Micro- and Nanopackaging and Assembly V, 2011
In this contribution, we report on a laser-chemical removal method for precise machining of micro... more In this contribution, we report on a laser-chemical removal method for precise machining of micro forming tools. Thereby, a focused machining laser beam is guided coaxially to an etchant jet stream. Since the material removal is caused by laser-induced chemical reactions using this method, machining is achieved at low laser powers. Hence, material stressing involving micro cracks and further parasitic
Zusammenfassung Zur Herstellung von Werkzeugen für das Mikro-Kaltumformen soll ein laserchemische... more Zusammenfassung Zur Herstellung von Werkzeugen für das Mikro-Kaltumformen soll ein laserchemischer Prozess eingesetzt werden. Dieser Ätzprozess ist mittels Laser in der Lage, auch schwer zerspanbare Werkstoffe zu bearbeiten. Für seinen flexiblen Einsatz zur Herstellung qualitativ hochwertiger Produkte wurde eine prozessdiskrete Regelung entwickelt, die auf einem Modell des Materialabtrags in Abhängigkeit der Prozessparameter basiert. In diesem Beitrag werden die Ergebnisse der automatisierten Parameter- und Bahnplanung am Beispiel einer konvexen Verrundung der Kanten eines Mikro-Tiefziehrings vorgestellt.
Cold formed micro parts with dimensions <1 mm show in some aspects characteristics due to scal... more Cold formed micro parts with dimensions <1 mm show in some aspects characteristics due to scaling effects that can be positively used in process chains. Whereas aspect ratios in upsetting processes are limited to l0/d0<2 in the macro scale, a laser induced free-forming process generates droplet shaped pre-forms for consecutive calibrating processes, i.e. micro rotary swaging. Scale effects on establishing and shortening of process chains like free-form heading/rotary swaging/heat treatment are discussed. On the other hand a geometric scale-up approach in the macro range is described to overcome the specific handling problems of miniature parts. This is achieved by leaving the parts in a physical linkage during the processing steps. An effective application of linked micro parts requires intensive modeling and simulation work.
<jats:p>This article describes the design of a high cadence laser micro-drilling machine fo... more <jats:p>This article describes the design of a high cadence laser micro-drilling machine for the manufacture of large micro-drilled panels, which will form part of the leading edge of tail stabilisers on future commercial aircraft. This type of microperforated surface will be of great interest mainly in the aeronautical field, since it will improve the aerodynamic performance of the aircrafts supposing a fuel saving of up to 10 %. Manufacturing requirements demand through-holes of around 0.1 mm at a cadence equal to or greater than 300 holes per second. The quality of each of the holes, as well as the precision of the distance between them has been decisive in the design phase. The machine will be equipped with on-site measurement and defect detection systems to ensure the quality of the holes. Keywords: microdrilling, laser, titanium, machine, HLFC</jats:p>
Este articulo describe el diseno de una maquina de microperforado por laser de alta cadencia para... more Este articulo describe el diseno de una maquina de microperforado por laser de alta cadencia para la fabricacion de paneles microperforados de grandes dimensiones, que formaran parte del borde de ataque de los estabilizadores de cola de los futuros aviones comerciales. Este tipo de superficie microperforada sera principalmente de gran interes en el ambito aeronautico ya que mejorara el rendimiento aerodinamico de las aeronaves suponiendo un ahorro de hasta un 10 % de combustible. Los requisitos de fabricacion exigen realizar orificios pasantes de alrededor de 0.1 mm con una cadencia igual o superior a los 300 orificios por segundo. La calidad de cada uno de los orificios, asi como la precision de la distancia entre ellos ha sido determinante en la fase de diseno. La maquina dispondra de sistemas de medicion y de deteccion de defectos in situ para asegurar la calidad de los orificios. Palabras clave: microperforado, laser, titanio, maquina, HLFC
Hybrid Laminar Flow Control (HLFC) ist eine Schlüsseltechnologie, durch die der Luftwiderstand be... more Hybrid Laminar Flow Control (HLFC) ist eine Schlüsseltechnologie, durch die der Luftwiderstand bei Flugzeugen durch Perforation der Vorderkanten von Leitwerken und Tragflächen reduziert werden kann. Für eine qualitativ hochwertige Perforation von Blechen mittels Laser ist die Bohrzeit ein entscheidender Einflussfaktor. Durch eine Auswertung des Prozessleuchtens beim Laserstrahlbohren kann die für den Anwendungsfall geeignete Bohrzeit ermittelt werden. Hybrid Laminar Flow Control (HLFC) is a key technology for reducing air resistance in aircrafts by perforating the front edges of tails and wings. Drilling time is a decisive factor for high-quality perforation of sheets using lasers. By evaluating the process light during laser beam drilling it is possible to determine the appropriate drilling time for the application.
IOP Conference Series: Materials Science and Engineering
For conventional laser shock peening, the positive influence of compressive residual stresses on ... more For conventional laser shock peening, the positive influence of compressive residual stresses on fatigue strength is well understood. To protect the material’s surface from ablation, a sacrificial layer is applied. This, however, leads to an additional process step, which deteriorates its economic efficiency. Thus, laser shock peening without coating (LPwC) is more frequently investigated for industrial applications. However, LPwC increases the thermal impact on the material, which may provoke tensile residual stresses in the surface region. In this regard, understanding the influence of LPwC on the residual stress state and deriving a suitable state, e.g., for subsequent applications or forming operations, result in a design of experiment with numerous residual stress measurements. Residual stress-depth-profiles obtained by X-ray diffraction are time-consuming and cost intensive. Hence, a model is proposed to predict the residual stress-depth-profile of LPwC-processed thin sheets. ...
International Congress on Applications of Lasers & Electro-Optics
An important challenge for all processes based on laser material removal is the control of the pr... more An important challenge for all processes based on laser material removal is the control of the precision of the shape. This is so, because all methods are non-contact methods and the removal rate underlies certain influences depending on the exact processing conditions and material properties, making only limited prediction and control of the removal rate possible. In laser chemical machining the radiation locally initiates on a metal surface a thermo chemical etching reaction, which leads to selective material removal at high resolution. To achieve an intensive mass transport and also cooling of the work piece the etch liquid is injected co-axially to the laser beam directly into the irradiated area. Measurements of the electrochemical potential against a reference electrode show a cathodic shift of the potential as a function of laser power and feed rate while processing. These functional dependencies of the chemical potential on the processing parameters can be used to control the temperature driven reaction and therefore the removal rate, as the chemical potential can be more easily and instantaneously measured than the temperature.An important challenge for all processes based on laser material removal is the control of the precision of the shape. This is so, because all methods are non-contact methods and the removal rate underlies certain influences depending on the exact processing conditions and material properties, making only limited prediction and control of the removal rate possible. In laser chemical machining the radiation locally initiates on a metal surface a thermo chemical etching reaction, which leads to selective material removal at high resolution. To achieve an intensive mass transport and also cooling of the work piece the etch liquid is injected co-axially to the laser beam directly into the irradiated area. Measurements of the electrochemical potential against a reference electrode show a cathodic shift of the potential as a function of laser power and feed rate while processing. These functional dependencies of the chemical potential on the processing parameters can be used to control the temperature driven re...
Abstract To reduce the fuel consumption of large passenger aircrafts the hybrid laminar flow cont... more Abstract To reduce the fuel consumption of large passenger aircrafts the hybrid laminar flow control is a key technology. For drag reduction, several millions of holes with diameters around 50 µm at the leading edges are needed. In this paper, the perforation of such titanium sheets using the laser processes of single pulse and percussion drilling is presented. The single pulse technique is an “on-the-fly” drilling process using a pulsed fibre laser in combination with a drilling optic with coaxial gas supply. The percussion technique is a flexible drilling process using a q-switched fibre laser combined with a galvanic scanner.
Fourth International Symposium on Laser Precision Microfabrication, 2003
In this treatment method laser radiation, which is guided from a coaxially expanding liquid jet-s... more In this treatment method laser radiation, which is guided from a coaxially expanding liquid jet-stream, locally initiates a thermochemical etching reaction on a metal surface, which leads to selective material removal at high resolution and quality of the treated surface as well as low thermal influence on the workpiece. Electrochemical investigations were performed under focused laser irradiation using a cw-Nd:YAG laser with a maximum power of 15 W and a simultaneous impact of the liquid jet-stream consisting of phosphoric acid with a maximum flow rate of 20 m/s. The time resolved measurements of the electrical potential difference against an electrochemical reference electrode were correlated with the specific processing parameters and corresponding etch rates to identify processing conditions for temporally stable and enhanced chemical etching reactions. Applications of laser-induced liquid-phase jet-chemical etching in the field of sensor technology, micromechanics and micrmoulding technology are presented. This includes the microstructuring of thin film systems, cutting of foils of shape memory alloys or the generation of structures with defined shape in bulk material.
Laser-induced technological chemical processes can significantly contribute to the development of... more Laser-induced technological chemical processes can significantly contribute to the development of new methods for micro treatment of materials and hence to the broadening of the application spectrum of laser microtech-nology. In this paper three typical laser-activated chemical technological methods in liquids, gases and solids and their possible applications are presented and discussed: First, laser-induced liquid-phase jet-chemical etch-ing of metals. In this method, laser radiation which is guided from a coaxially expanding liquid jet-stream initiates locally on a metal surface a thermochemical etching reaction, which leads to a selective material removal at high resolution (< 1 µm) and quality of the treated surface. Second, local photon-plasma induced synthesis of thin film coatings. This technological method is based on thermochemical CVD processes taking place in a photon-initiated stationary plasma maintained in the electromagnetic optical field of a high-power cw-CO 2 la...
In this paper we report on a new method for the generation of shaped holes by dynamical variation... more In this paper we report on a new method for the generation of shaped holes by dynamical variation of the beam shape with a special optical system. It is based on using a q-switched Nd:YAG laser with 100 ns pulses at a wavelength of 1064 nm and an optical setup producing a photon tube. By variation of the beam divergence the shape of the photon tube can be variably modified. The optical system consists of a specially designed Galilean telescope and a focusing objective. The beam divergence can be changed in-situ by the Galilean telescope while processing. This enables to control diameter, length and angle of the photon tube. Shaped controlled structures are processed applying in-situ different optical fields which have been previously defined by simulations including aberrations and diffraction effects. As an example, the variable beam shaping resulted in through-going cylindrical bores as well as such ones with a defined conical inlet with respect to its taper angle and depth. Taper angles between 1 and nearly 50 degrees were realized by varying both the beam divergence and laser power. Furthermore, the variable beam shaping leads to improved and almost debris-free machining efficiency.
Laser-based Micro- and Nanopackaging and Assembly V, 2011
In this contribution, we report on a laser-chemical removal method for precise machining of micro... more In this contribution, we report on a laser-chemical removal method for precise machining of micro forming tools. Thereby, a focused machining laser beam is guided coaxially to an etchant jet stream. Since the material removal is caused by laser-induced chemical reactions using this method, machining is achieved at low laser powers. Hence, material stressing involving micro cracks and further parasitic
Zusammenfassung Zur Herstellung von Werkzeugen für das Mikro-Kaltumformen soll ein laserchemische... more Zusammenfassung Zur Herstellung von Werkzeugen für das Mikro-Kaltumformen soll ein laserchemischer Prozess eingesetzt werden. Dieser Ätzprozess ist mittels Laser in der Lage, auch schwer zerspanbare Werkstoffe zu bearbeiten. Für seinen flexiblen Einsatz zur Herstellung qualitativ hochwertiger Produkte wurde eine prozessdiskrete Regelung entwickelt, die auf einem Modell des Materialabtrags in Abhängigkeit der Prozessparameter basiert. In diesem Beitrag werden die Ergebnisse der automatisierten Parameter- und Bahnplanung am Beispiel einer konvexen Verrundung der Kanten eines Mikro-Tiefziehrings vorgestellt.
Cold formed micro parts with dimensions <1 mm show in some aspects characteristics due to scal... more Cold formed micro parts with dimensions <1 mm show in some aspects characteristics due to scaling effects that can be positively used in process chains. Whereas aspect ratios in upsetting processes are limited to l0/d0<2 in the macro scale, a laser induced free-forming process generates droplet shaped pre-forms for consecutive calibrating processes, i.e. micro rotary swaging. Scale effects on establishing and shortening of process chains like free-form heading/rotary swaging/heat treatment are discussed. On the other hand a geometric scale-up approach in the macro range is described to overcome the specific handling problems of miniature parts. This is achieved by leaving the parts in a physical linkage during the processing steps. An effective application of linked micro parts requires intensive modeling and simulation work.
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