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Verfahren zur Materialabtragung sowie Vorrichtung zur Durchfuehrung des Verfahrens

Method for material ablation over desired erosion depth of a work piece by laser beam having partial beams, which have defined beam axis, comprises mutually guiding the axis of the laser beam or axes of the partial beams along erosion line
 
: Schulz, W.; Petring, D.; Schneider, F.; Niessen, M.

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Frontpage ()

DE 102007024701 A: 20070525
DE 102007024701 A: 20070525
B23K0026
G02B0027
Deutsch
Patent, Elektronische Publikation
Fraunhofer ILT ()

Abstract
(A1) Die Erfindung beschreibt ein Verfahren zur Materialabtragung ueber eine vorgegebene Abtragstiefe eines Werkstuecks mittels Laserstrahls, der aus einem oder mehreren Teilstrahlen besteht, die jeweils eine definierte Strahlachse aufweisen, wobei die Achse des Laserstrahls oder die jeweiligen Achsen der Teilstrahlen gemeinsam entlang einer Abtragslinie mit einer vorgegebenen Verfahrgeschwindigkeit gefuehrt wird/werden und der Laserstrahl eine vorgegebene raeumliche, einen Poyntingvektor S definierende Energiestromdichte, mit einem Betrag I0f(x) und einer Richtung s, aufweist, wobei die raeumliche Energiestromdichte eine Abtragsfront, mit einem Scheitel als dem in Abtragsrichtung am weitesten fortgeschrittenen Teil der Abtragsfront, erzeugt, mit der eine Abtragskante erzeugt wird, das dadurch gekennzeichnet ist, dass die jeweiligen Einfallswinkel L der Abtragsfront, die von den Normalvektoren n auf der Abtragsfront und den Richtungen s der Poyntingvektoren eingeschlossen sind, so eingestellt werden, dass die einen Maximalwert L?max? in einem vordefinierten Bereich um einen Scheitel der Abtragsfront nicht uebersteigen, wobei das Ueberschreiten des Maximalwerts dadurch erfasst wird, dass ein Wechsel von kleiner Riefenamplitude in einem oberen Teil der Abtragskante zu einer grossen Riefenamplitude in einem unteren Teil der Abtragskante auftritt. Weiterhin beschreibt die Erfindung eine Vorrichtung zur Durchfuehrung des Verfahrens.

 

DE 102007024701 A1 UPAB: 20081212 NOVELTY - The method for material ablation over a desired erosion depth of a work piece by a laser beam having partial beams, which have a defined beam axis, comprises mutually guiding the axis of the laser beam or the axes of the partial beams along an erosion line with a given process speed. The laser beam has a given spatial energy current density defining a Poynting vector (S) with an amount of l0f(x) and a direction (s). The spatial energy current density produces an erosion front (11) with a vertex as the part of the erosion front in erosion direction. DETAILED DESCRIPTION - The method for material ablation over a desired erosion depth of a work piece by a laser beam having partial beams, which have a defined beam axis, comprises mutually guiding the axis of the laser beam or the axes of the partial beams along an erosion line with a predetermined process speed. The laser beam has a given spatial energy current density defining a Poynting vector (S) with an amount of l0f(x) and a direction (s). The spatial energy current density produces an erosion front (11) with a vertex as the part of the erosion front in erosion direction. An erosion edge is produced with the part of the erosion front. The angles of incidence ( alpha ) of the erosion front are enclosed by the normal vectors (n) on the erosion front and the directions (s) of the Poynting vectors and are adjusted, so that they do not exceed a maximum value ( alpha max) in a predefined region around the vertex of the erosion front. The exceeding of the maximum value is seized. A change of small scoring amplitude in an upper of the erosion edge rises to large scoring amplitude in a lower part of the erosion edge. The scoring amplitude in the lower part is reduced, in which the predefined region comprises a larger ablation of the vertex. The Poynting vector on the erosion front is rotated with a laser internal- or laser-external beam-forming optics. Gaseous and/or fluid media and diffractive, refractive, reflecting and/or strewing optics are used as the beam-forming optics. The distribution of the amount of l0f(x) is adjusted to the spatially varying energy current density with larger diameter. The angles of incidence is reduced the cause of the fluctuation amplitudes of the erosion parameters during a temporal occurrence of system dependent fluctuations. Laser capacity, distribution of intensity, gas pressure and/or directions and amount of the process speed are considered as the erosion parameters. The angles of incidence are adjusted, in which the amount of a positive or negative spherical aberration or a chromatic aberration is produced or increased in the optics. The aberration in the optics is reached by fixing the combination of concave and convex lenses and by implementing optical elements having non-spherical surfaces. The combination of the lenses produces the aberration and simultaneously the collimation and/or the focusing of laser beam are carried out. The optical elements are implemented as axicon or Fresnel lens. The aberration in the optics is produced by gradient index optics. The optics is implemented as adaptive optics, so that the amount of the aberration is adjustable. Before and/or during the processing, the adjustments are controllably or regulatedly undertaken for the readjustment of the processing parameters such as materials type, material thickness, cutting-speed and laser capacity. The laser beam has the amount of l0f (x) of the energy current density, where l0 is the maximum value, f(x) is the distribution, x is unperturbed value and f is 0-1. The width of the distribution is increasingly adjusted with the predefined erosion depth in monotonous manner. The angles of incidence are adjusted on the vertex of the erosion front, in which an elliptical beam cross-section is produced with a beam formation within or outside of a laser resonator thus exhibiting large half-axis in the direction of the erosion line. The boundary regions of the distribution of f (x), where small values of the energy current density are present, are strongly suppressed by the optics within or outside of the laser resonator, so that no erosion takes place. Several laser beams are applied for adjusting the angle of incidence or the laser beam is divided into partial beams with beam-splitting optics. The individual laser beam or individual partial beam is adjusted with different focus depths and with increasing focus depth having a smaller beam radius and a larger Rayleigh length. The position of the beam axis of the individual laser beam or the partial beam is movably adjusted with increased focus depth against the erosion direction in monotonous manner. The part of the distribution spatially falling with the x is adjusted in constant manner. The spatial distribution is increasingly adjusted in the region of the erosion front. Several axicons are used for beam formation. An INDEPENDENT CLAIM is included for a device for material ablation over a desired erosion depth of a work piece by a laser beam having partial beams. USE - Method for material ablation over a desired erosion depth of a work piece by a laser beam. ADVANTAGE - The method is capable of economically removing the material over the desired erosion depth of the work piece with high quality, high productivity, reduced material thickness and less-operating time in improved manner, and avoids improper adjustment of the erosion parameters thus avoiding unnecessary large scoring amplitude with the erosion depth.

: http://publica.fraunhofer.de/dokumente/N-86190.html