WO2020253930A1

WO2020253930A1 - Method and device for drilling components

Info

Publication number: WO2020253930A1
Application number: PCT/EP2019/000186
Authority: WO
Inventors: Wolfgang Schulz; Torsten HERMANNS; Stefan Janssen; Ryu SUZUKI; Hideki Moriai
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.; Rheinisch-Westfälische Technische Hochschule Aachen; Mitsubishi Heavy Industries Aeronautic Engines Limited
Priority date: 2019-06-17
Filing date: 2019-06-17
Publication date: 2020-12-24
Also published as: JP2022548343A; DE112019007467A5

Abstract

The invention relates to a method for drilling components made of metal materials and components made of coated metal and dielectric materials. The spatial distribution of the Poynting vector assigned to the laser radiation is set differently in an overlap region of the bore to be produced, which is assigned a bore axis, a bore wall, and a bore base that is advanced as the bore depth is advanced, than in an edge region of the bore to be produced, wherein the overlap region is defined as the region which is irradiated using laser radiation with a high energy flux density during a single-pulse drilling process, and the edge region is defined as the region which lies outside of the overlap region and which is irradiated using laser radiation with a low energy flux density, lower than the energy flux density used in the overlap region, during the drilling process. The invention also relates to a corresponding device.

Description

description

"Method and device for drilling components"

The present invention relates to a method for drilling components made of metallic materials and components made of layered, metallic and dielectric materials by means of laser radiation. The present invention also relates to a device with which a corresponding method can be carried out.

Laser radiation is used in particular for ablating and drilling metallic materials and composite materials made of dielectric (e.g. ceramic) and metallic layers, known as fusion drilling. Particularly in applications in automotive technology, aviation technology, medical technology (machining of fine or central sheets) and energy technology (machining of so-called central sheets), high removal rates are required to create bores, consequently high productivity and high quality, especially good Conicity K = r _{B, t} op / r _{B, offered} ^uhe * the avoidance of a recast, desired. The conicity K = r _B, top / rB _, bot of the bore is defined as the ratio of bore radius b _{, / o} at the bore entry to bore radius re, bot at the bore exit. The geometric shape of the bore (e.g. cylindrical, conical) and the morphology of the bore wall (e.g. solidified melt / recast) are essential features that should be avoided.

Various requirements have to be met in fusion drilling. These include reproducible diameter of the bore, a defined taper of the bore, defined taper when drilling multilayer systems, no reduction in the adhesive and shear strength of coatings, no deposits of solidified melt (recast) on the bore wall, no burr formation at the bore exit, defined expulsion of the melt and a large curvature of the trailing edge in the area of the bore opening.

CONFIRMATION COPY State of the art

Known techniques for drilling with laser radiation are distinguished on the basis of the dominant mechanism for removing the material from the hole being formed. The removal can take place predominantly through expulsion of melt or predominantly through expulsion of evaporated material.

The group of drilling techniques with dominant melt expulsion include single pulse drilling (drilling with a single pulse), percussion drilling (multiple pulses with a fixed position of the beam axis of the radiation relative to the workpiece) and trepanning drilling (multiple pulses with the moving position of the beam axis of the radiation relative to the workpiece) . The individual drilling techniques have both advantages and disadvantages.

Percussion drilling is a technique in which laser light is irradiated without changing the irradiation position in order to create a hole or a bore at this irradiated position. The percussion drilling requires a small machining time because the irradiation position of the laser light is not moved.

Single pulse drilling and percussion drilling have the advantage of high removal rates (high productivity). Disadvantages are too small maximum achievable bore diameter, which is limited by the beam diameter of the laser radiation, poor quality of the bore due to incomplete melt expulsion, due to deposits of solidified melt on the bore wall and / or at the bore inlet and outlet as well as poor precision with regard to the Bore diameter.

In the so-called trepanning drilling, a percussion hole is first made in the material of the component and then a hole with a defined radius is cut out. Trephination drilling is a technique in which the laser light is moved along a circumference of a hole to be formed, the laser light having a spot diameter or beam diameter that is smaller than the hole to be made or the bore to be made in order to thereby forming an opening along this circumference and so the hole or the To create a hole. During trepanning, the shape accuracy of the hole is great, since the irradiation with laser light takes place along the circumference of the hole to be created.

Trephination drilling has the advantage that hole diameters that are larger than the beam diameter of the radiation used (hole diameter = 1, 2 x spot diameter) can also be achieved with a better quality of the hole wall compared to single pulse drilling and compared to percussion drilling . Trephination drilling has the disadvantage, however, that long drilling times are required, since a large proportion of the radiation used shines through the component through the existing hole and is not used.

For single-pulse and percussion drilling, measures are known which aim to drive the melt out of the hole as completely as possible in order to achieve a defined, mostly cylindrical shape of the hole. These measures include increasing the spatial mean value or the maximum value of the intensity or the energy flux density (with the unit of power per area

[W / m ² ] or with the unit energy per volume times speed

[(J / m ³ ) (m / s)]) of the laser beam used with increasing depth of the drilling and a temporal modulation (percussion) of the intensity with a large number of individual pulses during the entire drilling time.

DE 10 2004 014 820 B4 (corresponds to US 2007/193986 A1) describes a method for producing bores with a large aspect ratio in metallic materials and in layered metallic materials and those that have at least one ceramic layer. From this publication it emerges that for percussion drilling a radiation generating the bore can be designed in such a way that a complete expulsion of the melt in the direction of the radiation with an orientation against the propagation of the radiation or against the direction of the drilling progress from the bore with less Deposition of solidified melt on the bore wall can be achieved up to a maximum depth of the bore.

Percussion drilling is only used industrially when, regardless of the state of the art, the still existing poor quality of the drilling tion, ie incomplete melt expulsion with layer thicknesses of an adhering, solidified melt of typically more than 100 μm and thus a low precision of the hole shape, which does not restrict the function of the product.

In addition to percussion and trepanning drilling, the drilling techniques with a dominant evaporation also include helical drilling and laser eroding.

In helical drilling, in addition to trepanning, the radiation is rotated around the beam axis in order to compensate for any deviation of the spatial distribution of the laser radiation from a circular symmetry over time. An approximation to the required geometrical shape and the required quality of the bore is currently ^'only reachable by the helical drilling or a sequential combination of percussion and helical drilling.

DE 101 44 008 A1 describes a method for producing a hole in a workpiece by means of a laser beam. In a first step, a borehole is drilled with a first diameter which is smaller than the final diameter to be achieved, and in a second step or in further steps the borehole is widened to the diameter to be achieved. Consequently, a percussion bore produced with predominantly melt expulsion is widened to the desired diameter in a second process step by removing material as steam, so that almost no residues of solidified melt remain on the bore wall. Such drilling techniques have the disadvantage that the drilling time is too long or the productivity is too low as a result.

Furthermore, in known methods, the expulsion of the melt is generated by the evaporation of material and is thus controlled solely by the intensity of the laser radiation, which does not allow targeted control of the bore diameter and avoidance of melt deposits, also known as recast. In such methods, a second method step for smoothing the bore wall by evaporation removal of material is then required, as is indicated in the above-mentioned DE 101 44 008 A1. The prior art, which relates to drilling with dominant melt expulsion, as is also described in DE 101 44 008 A1, teaches that a rough and crack-prone layer of re-solidified melt (recast) can occur on the bore wall and to Deviations from the desired, geometric shape of the hole leads. Therefore, according to DE 101 44 008 A1, a recast and the deviations from the required bore diameter are to be removed by reworking and the bore wall to be smoothed by removal by means of evaporation removal.

US 5837964 describes a laser machining method in which percussion drilling and trepanning are used in succession. This document describes an aspect ratio greater than 10 and a sequential, successive processing of first percussion drilling and subsequent trepanning.

task

Based on the prior art described above, the invention is based on the object of specifying a method for drilling metallic Werkstof and of layered materials made of metallic and dielectric materials, in which at least some of the disadvantages described above with reference to the prior art avoided and, in particular, the required machining time is shortened without reducing the machining accuracy. According to a further object, a device is also to be specified with which the method can be carried out.

According to the method, this object is achieved by a method having the features of independent claim 1 and according to the device by a device having the features of independent claim 12. Advantageous embodiments of the method and the device emerge from the dependent claims.

With the method according to the invention, components made of metallic work materials and components made of layered metallic and dielectric materials by single pulse / percussion drilling and trepanning with laser Radiation and drilled with dominant melt ejection. The single pulse drilling is to be regarded as a non-pulsed process, since the energy flux density of the laser radiation is not interrupted in time until the drilling has been completed or the drilling has taken place. Trephination drilling can also be performed both pulsed and non-pulsed without time interruptions (pulse pause). According to the invention, the individual pulse / percussion drilling and the trepanning drilling are carried out simultaneously in terms of time.

The spatial distribution of the Poynting vector (<S>), which is assigned to the laser radiation (LS), which has a beam axis (B _A ) and a beam diameter (Ds), and is defined as the vector whose direction at positions next to the beam axis deviates from the direction of the beam axis (B _A ) and points in the direction of the local radiation propagation and whose amount is the energy flux density of the radiation, defined as the energy per volume multiplied by the speed of light, is in an overlap area (O) (overlap area ) the hole to be produced (H), which is assigned a hole axis (H _a ), a hole wall (H _w ) and a hole bottom (H _b ) that progresses with increasing hole depth, and is set differently in an edge region R of the hole to be produced. The energy flux density with the unit [J ms ^"1 m ³ ] (energy ^« speed / volume, J ms ¹ m ^"3 = W m ² ) is also referred to as the intensity of the laser radiation.

With the method according to the invention, a high energy flux density of the radiation is set in the overlap area (O) and a low energy flux density is set in the edge area. This spatial division of the energy flux density of the radiation results in the simultaneous application of a fast one in terms of time

Drilling in the overlap area (O) and high quality removal of the hole wall in the edge area. The method according to the invention combines the advantages of the known drilling methods, namely the high productivity of single-pulse or percussion drilling and the high quality of trepanning drilling.

The combination of the known drilling methods, so that the advantages of both methods are achieved, requires compliance with an interval with maximum and minimum nimal values for the intensity of the laser radiation, with the maximum and minimum values to be observed both in the overlap area (O) and in the edge area R being of different sizes. According to the invention, the setting of the two different intervals for the intensity of the laser radiation is achieved by using pulsed laser radiation with a moving laser beam axis, the movement of the laser beam axis having to take place in such a way that an overlap area (O) is created which is irradiated by each pulse of the laser radiation, and an outer edge area R which is not irradiated by every pulse. However, the setting according to the invention of the two different intervals for the intensity of the laser radiation is achieved by suitable beam shaping even without moving the laser beam axis.

The overlap area is defined as the area that is irradiated with each pulse of the laser radiation. The edge area is defined as the area that lies outside the overlap area and within the laser beam radius.

According to the method has a maximum value A _ma x of an aspect ratio A, defined as the ratio of bore length and bore diameter, with A = d / (2 re _op), where d with a vertical hole (H) relative to the surface or upper side of the material the material thickness of the material to be drilled through or, if the hole axis is inclined relative to the top of the material, the hole length is, and r _B , top is the hole radius of the hole (H) at the hole inlet, defined as the radius measured in the direction perpendicular to the hole axis (H _a ), den value

This restriction for the aspect ratio A <A _max is relevant, since for a larger aspect ratio A, greater than 10, in addition to the radiation set according to the invention with which the bore wall (H _w ) is directly irradiated and removed at a point A, also from the borehole wall (H _w ) at another point B contributes radiation reflected to the ablation at point A. As a result of the reflection and multiple irradiation of the bore wall (H _w ), the setting of the laser radiation (LS) according to the invention on the bore wall (H _w ) is changed by the reflected radiation and the method can no longer be carried out. Measures as are required according to the state of the art and are described, for example, in DE 10 2004 014 820 B4, which relates to single-pulse or percussion drilling, in order to generate radiation that forms the bore for a complete expulsion of the melt against the incident laser radiation It is not necessary to produce solidified melt deposits on the wall of the bore from the resulting bore.

Another advantage of the method according to the invention can be seen in the fact that, for example, subsequent trepanning drilling for subsequent removal of deposits of solidified melt on the bore wall (H _w ) is not required.

An essential measure of the method according to the invention is also to be seen in the division of the bore (H) to be created into a central area or overlap area (O) and an edge area (R). The spatial distribution of the radiation (LS) perpendicular to the bore axis (H _a ) of the bore to be reached (H) is set differently in the overlap area (O) and in the edge area (R).

The setting of the direction of the Poynting vector <S>, which is assigned to the laser radiation (LS), in the edge area (R) of the bore to be reached (H) can be done by setting the focus position and Rayleigh length of the laser radiation (LS).

For the method according to the invention, the energy flux density of the radiation in the edge area of the bore to be created must be measured and adjusted very precisely, since the removal takes place at very low values for the energy flux density. According to the invention, a threshold value is defined for the minimum energy flux density required for ablation, which is defined as a number with the dimension Wem ² for a pulse duration longer than one nanosecond or Jcm ² for a pulse duration shorter than 10 picoseconds (corresponds to 10 ⁴ Wm ² or Jm ² ), which replaces all otherwise known parameters relevant to drilling for characterizing the material to be drilled (melting temperature, heat capacity, thermal conductivity, etc.) and which has a typical value of 10 ⁴ to 10 ⁵ W ^» cm ² or 1 for metallic materials to 10 J ^"cm ² takes. The measurement with commercial devices, which have a limited range for the energy flux density to be measured and cannot simultaneously record any large differences in energy flux density, can only take place if z. B. the area of high intensity in the laser beam is hidden and so the outer area of the laser beam can be measured with high resolution and the setting must be checked by a measurement.

The laser radiation (LS) is preferably guided during drilling in such a way that its beam axis (B _A ) moves along at least one closed trajectory (C) to be traversed once. Here, half the beam diameter (D _s ) is selected to be at least as large as half the diameter (De) of the trajectory (C). The movement of the laser radiation (LS) during drilling takes place, for example, with the aid of a scanner.

In a further measure, the energy flux density of the radiation (LS) in the overlap area (O) and in the edge area (R) of the borehole (H) to be created can be set differently in terms of the time average. This means that the laser radiation is pulsed while the beam axis (B _A ) runs through a closed trajectory curve (C), as well as the time between two consecutive pulses (pulse pause) is changed, and that the path speed v _{c is changed} in terms of the time average.

In order to ensure that the maximum value A _max according to the invention for the aspect ratio is increased by undesired reflections of the laser radiation (LS) within the bore (H) having a sufficiently small value, which means that the reflected energy flux density assumes values that are smaller than

The Poynting vector (<$>) is set in the edge area (R) of the bore (H) with a directional component that points to the bore wall (H _w ) of the bore (R) to be created. This measure increases the absorption of the incident radiation (LS) and the reflection of the radiation (LS) on deeper areas of the bore wall (Hw) of the bore (H) being formed is avoided or at least reduced to such an extent that the threshold value for the Removal is not exceeded and there is no uncontrolled removal. The limit fluence F _th , that is the threshold value for a pulse duration shorter than 10 picoseconds, is reached or even fallen below during the formation of the bore or after a finite number of periods of passes, since the bore wall becomes increasingly steeper with each pulse and so the fluence of the radiation incident on the bore wall falls on an increasingly larger area or extent of the bore wall. If the limit fluence F _{th is} reached or undershot, then no further removal is possible and the asymptotic geometrical shape of the bore is achieved. This is the definition and the measurement rule for the values for the limit fluence F _th determined from the comparison of simulation and experiment. The geometric shape of the hole approaches a final or asymptotic shape, also referred to as the end shape, and can then not be removed any further. An approach to an asymptotic always means that the result of the drilling, when the asymptotic is reached, no longer depends on the irradiation time, or only weakly when it is approached, and is thus assumed to be reproducible.

In order to ensure high reproducibility of the geometric shape of the bore (H), it is advantageous to ensure that the asymptotics of the bore wall (H _w ) are reached. For this purpose z. B. several bores (test bores) with a growing number of pulses (pulsed laser radiation) or with increasing exposure time (cw laser radiation) are made and exposed to the laser radiation (LS) for an unnecessarily long time, and it is observed that the hole (H) is not continues to progress. The bore diameter achieved is determined experimentally by making cross sections. The asymptotic is reached when the bore shape or the bore diameter determined experimentally from the cross-sections no longer changes. If the asymptotics of the bore wall (H _w ) has been achieved, further bores can be produced with particularly high reproducibility or with technically negligible deviations - smaller than a few micrometers - from one another.

An asymptotic shape of the bore or asymptotics is understood to mean that bore shape which occurs after a certain number of pulses of laser radiation (pulsed laser radiation) or after a certain irradiation duration (cw laser radiation) and which occurs with all subsequent pulses or subsequent irradiation no longer changes, which is also referred to as a removal stop. The number of pulses of the laser radiation after which the asymptotic is present or an asymptotic is approximated depends on the values of the material, beam and process parameters. An approach to an asymptotic therefore means that the hole shape achieved does not change any more as the irradiation time progresses, or that the result of the hole shape changes only very slightly as the irradiation time progresses, so that the present hole shape is assumed to be reproducible and thus reaches a final shape.

According to a measure according to the method, reaching the final shape of the hole is determined by setting the laser radiation (LS) to the edge area (R) and a threshold value is defined for reaching the final shape of the hole (H), which is defined as a number with the dimension W ^» cm ² for a pulse duration longer than one nanosecond or cm ² for a pulse duration shorter than 10 picoseconds (corresponds to 10 ^-4 W * m ² or J * m ^{~ 2} ), which are all otherwise known parameters relevant for drilling Replaces characterization of the material to be drilled and which assumes a typical value of 10 ⁴ to 10 ⁵ W ^« cm ² or 1 to 10 J * cm ² for metallic materials.

Since the borehole wall becomes increasingly steeper as the drilling time progresses, an increasing proportion of radiation hits an increasingly larger partial area of the borehole wall (H _w ), and thus the fluence (F) of the radiation incident on the borehole wall (H _w ) becomes smaller. In this way, the shape of the bore approximates reproducibly and with great accuracy a final shape that cannot be removed any further.

For a pulse duration or a time of interaction of the laser radiation with the material shorter than 10 picoseconds, the laser radiation deposits the absorbed energy only in the free electrons of the material without noticeable heating of the atoms of the irradiated material. Instead of the energy flux density [J ^« m ² s ¹ ], the fluence (F) [J * m ² ] is defined as the integral of an energy flux density over time, with the fluence being the proportion of energy in the laser radiation (radiation energy) that per Area the material is irradiated, defined and has the SI unit J * m ² . The radiation energy per area with which the material of the component is irradiated can also be referred to as fluence (F) with F = bA t, where the energy flux density is also referred to as intensity / and At indicates the duration of the irradiation of the component.

If a threshold value (limit fluence F _th ) for the fluence (F) is undershot, removal is no longer possible and the asymptotic, geometric shape of the bore is reached. This is because the geometric shape of the bore approximates a final or asymptotic shape and can then no longer be removed. It is therefore necessary to ensure that the asymptotics are achieved for a high degree of reproducibility of the geometric shape of the bore, as has already been explained above.

When drilling through the material, the bottom of the hole opens, with part of the laser radiation shining through the hole and not being absorbed by the material to be drilled. The bottom of the hole (H _b ) is defined here as the progressing end of the hole (H) that forms during drilling. In a hole (H) opening at the bottom of the hole, the melt is accelerated less strongly from the area around the hole and is no longer completely expelled from the hole and solidifies on the hole wall. In order to prevent the melt to be expelled during drilling from solidifying on the wall of the hole, an advantageous measure for drilling with pulsed laser radiation is that when drilling with several pulses (up to the last pulse) the melt is countered before drilling through the overlapping area (O) the direction of propagation of the laser radiation (LS) is driven out of the bore (H). This is achieved by setting the energy flux density of the laser radiation in the overlap area (O) in such a way that the bottom of the hole reaches the material thickness and there is still no through hole. In this way, the remaining volume in order to achieve the final shape of the bore and that still has to be removed and that at least partially remains in the bore as an undesirable recast is as small as possible.

The method enables the melt to be expelled from the bore that is being formed without the use of a gas nozzle and only due to the evaporation pressure respectively. The energy flux density in the overlap area, ie the area that is irradiated with each pulse of the laser radiation, and the pulse duration are set so that the bottom of the hole reaches the bottom of the component at the end of the pulse without having reached the above-mentioned asymptotics. The success of a small recast thickness can be determined by measuring the recast thickness, i.e. the thickness of the enamel deposits that solidify on the bore wall and cannot be expelled and that are typically less than 100 μm for non-rotating components and typically less than 50 for rotating, accelerated components pm should be determined. The intensity and the pulse duration of the radiation used are adjusted in such a way that at the time of drilling through the component on its underside (at the bottom of the hole (H _b )) only a minimal, remaining volume of melt needs to be removed in order to ultimately achieve the asymptotics of the hole . At this point in time the very small remaining volume of material still to be removed is melted and driven partly downwards and partly upwards along the bore wall by the evaporation pressure out of the bore, where it in turn partially solidifies and forms a recast.

The energy flux density should not fall below a minimum value and the energy flux density should not exceed a maximum value. The minimum value is determined by the fact that there is no drilling through, defined as no opening of the bottom of the hole on the underside of the component, and the maximum value is determined by the fact that the drilling time to reach the through hole increases suddenly. A sudden increase means that for an energy flux density slightly less than the maximum value, a short drilling time is sufficient to drill through the material, the drilling speed v _p assuming large values, typically greater than ¹ ms ¹ , and that for an energy flux density slightly greater than Maximum value, a long drilling time is required until drilling through and the drilling speed v _p assumes small values, typically less than 10 ² ms ¹ .

It should be noted that an energy flux density of the laser radiation that is too low is not sufficient to drive the melt out of the hole over its entire depth, and that the intensities of the laser radiation that are too high result in a too dense measurement. create tall vapor, which absorbs the laser radiation significantly and thus reduces the drilling speed v _p .

According to the method, by setting an incremental angle (alpha), defined as the angle through which the beam axis (B _A ) of the laser radiation is rotated around the bore axis (H _a ), a bore that is circular in cross section, an eight-shaped bore, an elongated bore or a three-hole - or star-shaped holes are generated. According to the state of the art, the production of non-circular bore cross-sections requires a beam diameter of the laser radiation that is smaller than the smallest cross-section of the bore, and the bore contour to be generated must be traced along a trajectory. By using prior art methods, the smallest can be achieved

Cross-sectional shape, e.g. B. the x-shaped section in the middle of an eight-shaped contour, when tracing the contour at least as large as the beam diameter and thus larger than by using the method according to the invention, since with the method according to the invention, the x-shaped section of the eight-shaped contour only through the Overlap area of the laser beam diameter is irradiated.

With the method according to the invention, an eight-shaped bore is produced by setting the increment angle and the pulse pause in such a way that the increment angle between two successive pulses is 180 degrees and the laser radiation is pulsed, the pulse being repeated when reaching 0 and 180 degrees, until the eight-shaped hole shape is reached. To create an elongated hole, an increment angle of 180 degrees and the pulse pause are set in such a way that the increment angle between two successive pulses is 180 degrees and the pulse is repeated when 0 and 180 degrees are reached, with the overlap area being set so large that an elongated hole is created. A three-hole hole, this is a hole that z. B. has three bores with an angular distance of 120 degrees, is generated by setting the increment angle to 120 degrees, the pulses are repeated when reaching 0, 120 and 240 degrees, until the three-hole hole is formed. A star-shaped bore is created according to the method according to the invention when incre- angle and pulse pause are set so that the pulses are repeated when reaching 0, 360 ^* 1 / n, 360 * 2 / n, 360 * (n-1) / (n) degrees, where n is a natural number and 360 / n is a natural number until the star-shaped hole is reached.

The essential advantages and special features of the bores that can be produced by the method according to the invention, as well as special applications and areas of use resulting therefrom, can be summarized as follows:

The diameter of the bore to be created with the method according to the invention increases with the duration of the irradiation and strives for an asymptotic value. When approaching the asymptotic value for the hole diameter, the removal per pulse or the drilling speed v _p tends to zero and the diameter of the hole is reproducible.

It should be noted here that when drilling with a gas jet to expel the melt, the smallest diameter of a hole that is created with regard to the depth of the hole is the feature of the geometrical shape of the hole, which limits the volume flow of gas throughput.

The total flow volume, for example of fuel filters, is added up from the flow volumes of the individual bores. Turbines are cooled by bores, the diameter and widening of which (conicity) determine the cooling effect. The production of bores in fuel filters and turbine parts is therefore a particularly important field of application of the method according to the invention.

The flow behavior when gases and liquids emerge from a borehole are determined by the angle of the borehole wall to the material surface and the widening of the borehole, ie the conicity of the borehole. Maintaining a predefined conicity is crucial for the distribution of cooling gases on material surfaces, for example to protect turbine components. With the method according to the invention, such a conicity can be set in a very defined manner by the Poynting- - _>

vector (<S>) in the edge area (R) of the hole (H) a monotonous with the hole tion depth has variable directional component which points to the bore wall (H _w ) of the bore to be reached (H). Since the absorption of the radiation and thus the drilling speed v _{p increases} with the increasing directional component on the wall (Hw), the diameter of the drilling also increases proportionally to the directional component.

The cylindrical or conical shape of a bore is a prerequisite for a laminar flow of liquids and gases through the bore. The diameter of holes in multi-layer systems, consisting of a base material, an adhesion promoter layer and a thermal insulation layer, as is the case in particular in turbine components, must be adjustable independently of the material layer to be drilled through during drilling, so that regardless of the material layer to be drilled through, a smooth bore wall and a bore diameter that widens or narrows evenly with increasing bore depth. According to the method according to the invention, this is possible in that first the thermal insulation layer is drilled through, which requires a greater energy flux density for drilling or has a greater value for the threshold fluence, and the drilling duration is selected so that the hole in the thermal insulation layer achieves its asymptotic shape and during subsequent drilling in deeper layers of material with a lower energy flux density or a lower value for the threshold fluence, it is no longer removed.

Another surprising property of the method according to the invention can be seen in the fact that a defined conicity can be carried out over the entire depth of the hole when drilling multilayer systems with very different properties for the absorption of laser radiation and heat conduction - ceramic of the thermal insulation layer and metal of the base material. The layers to be drilled first have a surprisingly negligible effect on the drilling process and thus the shape of the hole. This is understood as a consequence of the melt flow, which flows over the ceramic layers drilled first and covers them, whereby the absorption of laser radiation and heat conduction for the thermal insulation layer and the metallic base material become the same and a smooth bore wall is created. So it is essential that that The method according to the invention has a melt expulsion counter to the jet direction from the beginning of the drilling up to the time of the drilling through. Since the hole is created in the central area, areas of the hole where there is a lack of quality - here shape deviations due to different material properties - are removed in the further course of drilling and thus do not contribute to the quality of the hole. The melt of the lower-lying metallic layers are driven in the direction of the overlying, for example ceramic layers and cover them, which means that the radiation on the molten material is absorbed from the deeper layers and the heat is dominated by the covering melt.

No reduction in the adhesive and shear strength of coatings can be observed. When drilling multilayer systems, the adhesion between the

Layers in the area of the hole are not reduced. For example, if the thermal insulation layer of turbine components is damaged, the layers of the components that are thermally and mechanically highly stressed during operation can detach from the base material and protection by the thermal insulation layer is no longer guaranteed. Since the adhesion between the layers is thermally stressed during drilling by the melt flowing out of the hole wall against the direction of the jet, the layers being heated again to the melting temperature of the melt flowing past during each pulse and due to the different thermal expansion in the different layers If the layers result in a thermomechanical shearing effect of different strengths, the pulse pause between two successive pulses must be chosen so large that the heating by heat diffusion can decrease again and there is no accumulation of heat, which would increase the shearing effect. It should be noted here that the penetration depth of the heat (scaled the thickness of the thermal insulation layer) in the thermal insulation layer must remain less than 1, otherwise the shearing effect will be too strong, as shown in the graphic in Figure 4 of the drawing. In this figure, the depth of penetration of the heat into the thermal insulation layer and the temperature on the bore wall of the thermal insulation layer after heating are shown in the time tp and a pulse pause tpause. This is according to the invention Method possible in that the pulse pause tpause is to be selected as a multiple of the pulse duration tp, the temperature T being calculated from the scaled temperature Ts from the relationship T = Ta + (Tm-Ta) Ts. Ta indicates the ambient temperature, while Tm indicates the melting temperature. The graph in FIG. 4 shows how the scaled temperature Ts decreases during the pulse pause tpause. In order to cool down from the melting temperature Ts = 1 to the 10th part of the melting temperature Tm - the constant curve in FIG. 4 - the pulse pause tpause must be 40 times as large as the pulse duration tp.

According to the method according to the invention, a deposit of solidified melt (recast) on the bore wall is avoided. A defined bore diameter can only be achieved if the geometric shape of the bore is not changed by irregular deposits of solidified melt on the bore wall, which would also affect the drilling progress and the geometric shape of the drilling unsystematically. In addition, cracks and stresses can arise in the solidified melt, which can lead to damage during operation of the component. In the case of highly stressed components, such as turbine blades and fuel filters, avoiding deposits from solidified melt increases their service life.

The formation of burrs due to solidified melt at the hole outlet is avoided because the method creates a through hole in the overlap area which has a smaller hole diameter than the hole diameter of the edge area after the asymptotic shape of the hole has been reached. The burr that arises at the beginning of the hole at the hole exit in the overlapping area is still abgetra conditions with the method of drilling in the edge area, and since the two areas are abraded close to each other, a short drilling time is achieved. Avoiding the formation of burrs saves post-processing and reduces the production time, for example of turbine components and fuel filters, and the efficiency of cooling is increased, since otherwise burr formation at the bore outlet reduces the flow resistance of a cooling fluid and thus the efficiency of cooling. The melt can be expelled in the direction opposite to the incident laser radiation by a pressure gradient due to evaporation of the component material at the bottom of the hole, which is much more efficient for small hole diameters in the initial phase of drilling than a pressure gradient due to a driving, external gas jet . According to the prior art, an external gas jet is required to expel the melt. Experience with the method according to the invention shows that the melt expulsion in the overlapping area by pressure gradients due to evaporation is sufficient and an external gas jet is not required. The outflow of dominant portions of the melt from the overlapping area out of the bore and against the incident laser radiation reduces the recast on the bore wall. When manufacturing stents, fuel filters and turbine blades, post-processing, also known as cleaning, is otherwise necessary if material residues (recast) are deposited in the bores during drilling.

Very small radii of curvature can be achieved at the trailing edge of the hole. These small radii of curvature, ideally a sharp edge, which corresponds to 90 degrees or a right-angled edge, are achieved by increasing the absorption of the laser radiation on the bore wall near the leading edge by adding the Poynting vector (<S>) in the edge area (R) of the bore (H) has a directional component which changes with the bore depth and which points to the bore wall (H _w ) of the bore (H) to be reached.

While the hole is being drilled, the resulting melt should detach itself from the leading edge (so there should be no burr), and while the hole is in use, for example as a hole in a nozzle, a fuel, for example, is supposed to detach itself from the trailing edge. The detachment of a liquid flow at the bore opening (i.e. both at the leading edge where the bore is made and at the bottom of the component where the bore bottom opens first) is determined by the curvature of the trailing edge. In the case of injection nozzles, the curvature of the trailing edge is decisive for the detachment and the complete burning of the fuel in the combustion chamber. The drawing in of ambient gases into the bore or the detachment of a cooling gas flow from the outlet of a cooling bore in turbine blades are undesirable properties of the flow, the occurrence of which depends on the geometric shape of the exit edge, which should preferably be right-angled, at least approximately right-angled.

The device according to the invention for drilling components made of metallic materials and components made of layered metallic and dielectric materials has a laser processing device which comprises at least one beam unit which directs laser radiation onto the component, and has a control unit which controls the radiation unit in such a way that that a spot area, defined as a region of the component irradiated with the laser radiation on an upper side, moves along an inner circumferential section, which is a position corresponding to an inner circumference of the bore to be created, and further controls such that part of the spot area creates an area of overlap within the inner peripheral portion of the bore at any point in time.

With such a laser processing device, a very good shape accuracy of the bore is achieved and the time required to form the bore is shortened in comparison with conventional methods.

The device uses the irradiation or cross-sectional area of a spot area of the laser radiation that strikes the component, which is smaller than a cross-sectional area of the bore to be created.

It is also preferred that the laser processing device emits the laser radiation in such a way that a point diameter, which is a diameter of the spot area, is greater than half a length of a diameter of the bore to be created and less than the length of the diameter of the bore. As a result, an excessively high energy flux density of the laser light, which is necessary for drilling through and desired for quickly drilling through the overlap area, is advantageously reduced at the edge of the opening, i.e. in the edge area, the reduction in energy flow density leading to a smaller removal volume per pulse and thus the accuracy of the shape the drilling improved. The control unit controls the laser beam unit in such a way that the laser radiation expands an area of the opening in the component, seen in the radial direction to the beam axis, from the overlapping area outwards.

In order to improve the expulsion of the melt after the bottom of the bore has been opened, an auxiliary fluid supply unit is provided which supplies a fluid to the top of the component and into the bore that is being formed in the component.

The laser processing device can have a laser oscillation unit that oscillates the laser radiation in the radial direction with respect to the beam axis, and a galvano scanner unit that changes a position of the spot surface by reflecting the laser radiation, while at the same time an optical path of the laser radiation oscillated by the laser oscillation unit changes, insert.

Further details and features of the invention emerge from the following description of exemplary embodiments with reference to the drawing.

In the drawing:

Figures 1 to 3 show in schematic cross-sectional representations the creation of a hole in a component in a time sequence using the method according to the invention in each case in a plane containing the axis of the hole, wherein

Figure 1 shows the geometric shape of the bore wall and the bore bottom before the time of drilling through the bore bottom,

Figure 2 shows the geometric shape of the bore wall at a point in time of drilling through,

FIG. 3 shows the geometric shape of the bore wall when the bore wall has assumed its predefined geometric shape to be achieved,

FIG. 4 shows a graph that shows the temperature on the bore wall on the thermal insulation layer after heating by the melt flowing past in a time tp and a pulse pause tpause, Figure 5 shows the geometric relationships of a hole to be created in a cross section perpendicular to the hole axis,

FIGS. 6A to 6E show a chronological sequence of cross-sectional representations corresponding to FIG. 5 of the drilling process for creating the hole by superimposing radiation components in an edge area and in an overlapping area,

Figure 7 shows in the sequence of images (1) to (4) the progressive drilling through a component,

FIG. 8 shows, in the sequence of images (1) to (4), a trepanning process as it is used according to the prior art to produce a bore,

FIG. 9 shows the schematic structure of a device according to a first embodiment with which the method according to the invention can be carried out,

FIG. 10 shows the structure of FIG. 9 with an additional auxiliary gas supply unit, and

FIG. 11 shows a schematic view of a device for drilling, in a partially sectioned representation, as it can be used in the devices of FIGS. 9 and 10, and with an auxiliary gas supply source assigned to the device for drilling.

The method according to the invention for drilling components made of metallic materials and components made of layered metallic and dielectric materials using single pulse / percussion drilling and trepanning with pulsed or continuous laser radiation is described below with reference to FIGS. 5 and 6A to 6E.

In order to explain the geometric relationships, reference is first made to FIGS. 1 to 3.

FIG. 1 shows the cross-sectional representation of a component 1, which has a thickness d perpendicular to its upper side 2, before the point in time of drilling through the bottom of the hole H _b . The component 1 consists of a metallic material or of layered metallic and dielectric materials. In this component 1, a bore H is already formed with a bore axis H _a , which runs in the plane of the cross section, the bore wall of which is denoted by H _w .

The drilling speed is denoted by v _p and indicates the movement of the bottom of the hole H _b in the direction of the hole axis H _a . R denotes an edge area which is defined as that area which lies outside the central or overlap area O and is irradiated with a lower energy flux density of the laser radiation LS during drilling.

The beam axis B with a beam direction of the laser radiation is moved on a trajectory C with a direction R _c and runs through this trajectory C repeatedly until the drilling result sketched in FIG. 3 is achieved. The trajectory C lies in a plane perpendicular to the beam axis B _A (beam axis).

The bore H in FIG. 1 has not yet penetrated the underside 3 of the component 1 and shows a conical cross-sectional shape. This means that the bore H is still limited by a bore base H _b , to which a diameter Do of the overlap area O is assigned. The overlap area O is shown in dashed lines in FIGS. 1 to 3. Up to this drilling phase, the melt is consequently accelerated against the beam direction of the beam axis B _{A of} an inserted laser radiation LS out of the hole base H _b and expelled from the hole H along the hole wall H _w on the upper side 2 of the component 1. The accelerating effect is caused by the evaporation of the material at the bottom of the hole H _b and the evaporation pressure or ablation pressure acting on the melt of the material.

FIG. 2 now shows, in broken lines, the cross-sectional shape of the overlap region O and the geometric shape of the bore wall H _{w of} the bore H at a point in time at which the component 1 has been drilled through on the underside 3. The point in time of drilling through the component 1 is defined by the fact that the entire width Do of the overlap area O has reached the underside 3 of the material and the orientation of the melt expulsion changes, which means that the melt can now also predominantly on the underside 2 of the component 1 step out. FIG. 3 shows the geometric shape of the bore wall H _{w of} the bore H when the bore wall H _w , starting from the shape of the bore H as shown in FIG. 2, has reached its predefined, geometric shape, this being defined by a radius r _{S top} on top 2 of component 1 and a radius right. _bo t are predefined on the underside 3 of the component 1. For a conical bore, r _B , top = r _B , bot and the diameter D _{H of} the bore is constant with respect to the bore depth.

FIG. 3 shows that the bore diameter Do in the overlap area is smaller than the bore diameter D _{H of} the entire bore to be made, which also reaches the outer edge, that is the bore wall H _w (dashed), of the edge region R.

In order to produce a bore in a component 1 by means of laser radiation LS, according to the invention both the single-pulse / percussion drilling and the trepanning drilling are carried out simultaneously in terms of time, ie. H. that the two processes are superimposed by the overlap in the overlap area with pulsed laser radiation LS or superimposed with continuous laser radiation or non-pulsed laser radiation by setting an inner central area or overlap area O with a high energy flux density and an outer area or edge area with a smaller energy flux density.

A higher energy flux density means that a maximum value is not exceeded, above which a strong absorption of the laser radiation LS occurs in the metal vapor from removed material and the drilling time increases drastically, suddenly with decreasing energy flux density. A lower energy flux density means that the value does not fall below a minimum value or threshold value, below which there is no more erosion or an ablation stop occurs.

The beam guidance of a laser radiation LS used with continuous laser radiation or non-pulsed laser radiation will now be explained with reference to FIGS. 5 and 6A to 6E.

Figures 6A to 6E show a chronological sequence of cross-sectional representations (snapshots) perpendicular to the bore axis H _{a of} the drilling process corresponding Correspondingly, FIG. 5 shows the creation of the bore by superimposing radiation components in an edge area R and in an overlapping area O. The beam axis B _A runs through a closed trajectory C, and by changing the time between two successive pulses (pulse pause) and the trajectory speed v _c the time average of the energy flux density in the edge area is changed.

The beam shaping carried out with continuous laser radiation or non-pulsed laser radiation is carried out in such a way that the laser beam axis B _{A is} not moved and the laser radiation LS in the central area O - which in the case of pulsed laser radiation is referred to as the overlap area O of the individual, successive pulses - is larger Has energy flux density smaller than the maximum value and in the edge region has a smaller energy flux density greater than the threshold value of the ablation stop.

The bore H shown in cross section in a plan view in FIG. 5 is intended to have a diameter D _H with a radius DH / 2 extending from the bore axis H _a over the entire thickness d of the component 1 shown in FIGS. 1 to 3 goes out, so that a cylindrical bore wall H _w through the component 1 results.

In FIG. 5, a central area O, hereinafter also referred to as the overlap area O, to which a diameter D _{0 is} assigned, is shown hatched. The edge region R adjoins the central region O in the radial direction and extends to the bore wall H _w .

For the area FR this edge region R where: FR = F _H - Fo = p · D _H / 2 - p · Do / 2, where F _H indicates the cross-sectional area of the hole H and Fo indicative of the area of the central / overlap area O.

From FIG. 5, also from FIGS. 1 to 3, it can be seen that at the beginning of drilling a hole H, which is shown in FIG. 1, a large drilling progress is achieved in the overlapping area O and a comparatively small drilling progress is present in the edge area R. . As FIGS. 5 and 6A to 6E now show, the top of the component (see also FIGS. 1 to 3) is irradiated with laser radiation LS, the beam axis of which is labeled B _A and which, viewed perpendicular to the beam axis B _A , has a beam diameter Ds owns. The irradiated area of the upper side of the component is the cross-sectional area S of the laser radiation LS and is also referred to as the spot area S.

The laser radiation LS that strikes the component at the spot surface S is now guided according to the invention in such a way that its beam axis B _{A is} guided on a trajectory C, in the example shown on a circular path C, around the bore axis H _a , like this Figure 6A illustrates. The direction Re of the beam axis guidance along the circular path C (contour C) takes place counterclockwise in the example shown in FIGS. 6A to 6E, but this is not absolutely necessary. This beam guidance can also be carried out in a clockwise direction.

The following applies to the beam diameter Ds

Ds ⁼ De ⁺ Do and Ds ⁼ DH 2 + Do / 2,

with D _s = beam diameter of the laser radiation

D ₀ = diameter of the central area O

D _H = diameter of the hole Fl

De = diameter of circular path C, also referred to as path curve C, FIG. 6A now shows, compared with FIG. 5, the illumination or irradiation of the component after two pulses of laser radiation LS, while FIG. 6B shows the illumination or irradiation of the component after three Pulses of the laser radiation LS, which shows FIG. 6C the irradiation of the component after four pulses of the laser radiation and FIG. 6D the pulses of the radiation after a complete revolution. The edge of the spot area S of the last pulse in each case is shown in a thick line.

It can be seen from the sequence of FIGS. 6A to 6E that the central area O is irradiated with each pulse of laser radiation, the cross-sectional area or spot area of which is denoted by S, and is consequently also denoted as the overlap area O, while the edge area R is that area is defined, which lies outside the overlap area O and is not irradiated with every pulse due to the movement of the laser beam axis B _A along the contour C. FIG. 7, pictures (1) to (4) represents a schematic diagram which shows an example of how a hole (bore) at the bore bottom H is opened. As a result of the irradiation with the laser radiation LS, the opening H (hole) in the component 1 is gradually expanded outwards in the radial direction, as can be seen from the increasing black area, starting at the location of the hole axis H _a . The edge of the circular area shown in black indicates the respective bore wall H _{w of} the bore H in the component 1.

The diameter DH = 2 ^» re _{, offered to} the bore H on the underside of the component 1 is consequently increased until the asymptotic shape of the bore H to be achieved is reached and no further abrasion occurs due to further irradiation of the energy flux density.

As shown in FIG. 7- (1), at the beginning of the irradiation with the laser light LS no opening of the bore H or no through-bore is achieved. This means that, in order to achieve the opening, a laser beam unit used continues the irradiation with the laser radiation LS while it moves the spot surface S several times along the direction Rc, as described above with reference to FIGS. 6A to 6E.

The laser beam unit irradiates the overlap area O with the laser radiation LS at all times while it moves the spot area S. The time-averaged energy flux density of the laser radiation LS is therefore greater in the overlap area O than in the edge area R.

As FIG. 7- (2) shows, the opening or hole H at the bottom of the hole is consequently first opened in the overlap area O. With the further irradiation, the opening is enlarged (FIG. 7- (3)) until finally the opening H assumes its full diameter (FIG. 7- (4)).

It should be noted that the time span for which the laser light LS is emitted tends to become shorter from the bore axis H _a over the edge of the overlap region O in the radial direction outward. Accordingly, the opening that forms is expanded in the radial direction from the overlap area O outwards until the diameter of the opening is up to the predefined bore wall H _{w is} sufficient and the predefined hole H is generated (see also Figure 6E).

FIG. 7 also makes it clear through the image sequences (1) to (4) that the single pulse / percussion drilling and the trepanning drilling are carried out simultaneously. Simultaneously means that the laser beam is guided in such a way that the central area O is completely irradiated with each pulse of the laser radiation LS, the beam axis B _A being offset from the beam axis B _{A of} a previous pulse and thus only a part of the edge area being irradiated during a pulse becomes.

The beam diameter Ds of the laser beam LS should not be set smaller than half the diameter D _{H of} the bore to be reached (Ds> DH / 2) - see Figure 5. This measure ensures that a central area O is formed which has a greater energy flux density is irradiated and for cw radiation is irradiated with radiation during the entire drilling period or is irradiated with each pulse for pulsed radiation.

Also, in order to ensure that the entire central area O is exposed to radiation during the entire drilling period without missing a gap, the diameter De of the trajectory C should not be set larger than the beam diameter D _s , so that consequently D _s <D _c applies - see Figure 5. This measure also ensures that a central area O is formed.

In the case of the method that is illustrated with the aid of the figures described above, it must be ensured that no multiple reflections of the laser radiation change the shape of the bore. According to the invention, the final, asymptotic bore shape is clearly defined by the spatial distribution of the energy flux density of the laser radiation and the movement of the beam axis, with multiple reflections and consequent repeated irradiations being undesirable. Such multiple reflections are avoided in that, for example, the spot diameter Ds and the path diameter D _{c are set} so large that an aspect ratio A = d / (2 r _{B, top} ) less than 10 is maintained. Multiple reflections occur with small bore diameters and large bore depths, which means that the aspect ratio is typically greater than 10. In order to carry out the method according to the invention, the movement of the beam axis B _{A of} the radiation LS can be carried out during drilling with the aid of a scanner, the movement of the beam axis B _A along a closed trajectory C with a diameter D _{c that is} to be passed through at least once periodically he follows.

As already mentioned, the spot area S, ie the cross-sectional area of the laser radiation LS perpendicular to the beam axis B _A , is smaller than an area of an opening, ie an area over which the bore H is gradually opened. The laser processing device used is able to prevent the concentration of the energy flux density of the laser radiation LS at the edge of the opening by using the method according to the invention, also with the result that a reduction in the dimensional accuracy of the opening is prevented if the spot area S is along the inner Peripheral section I of the bore (see Figure 7) is moved.

In the sequence of images (1) to (4) of FIG. 8, a trepanning process is shown as it is used according to the prior art for producing a bore. During the trepanning machining, the spot area SX is moved along the inner circumferential section I of a bore contour to be produced, but there is no overlap area which, in terms of time, is overlapped by the spot area at every point in time of the irradiation. A laser processing device that performs such a trepanning processing according to the prior art first emits laser light, represented by a spot area SX1 (see Figure (1)), so that a hole is opened, for example in the center of the hole to be produced. This means that such a hole is created for the discharge of the molten material, which runs through the entire thickness of the component. The irradiation position of the laser light is then moved in the radial direction to a spot position SX2 (see figure (2)). Subsequently, the irradiation position of the laser light is moved along the inner peripheral portion I so that the spot area changes to the position SX3 (see figure (3)). This movement of the spot area is now repeated as shown in Figure (4). ' FIG. 9 shows a schematic representation of a first embodiment according to the invention, with which the method described above can be carried out.

Insofar as reference is made to the radiation guidance of the laser radiation LS in connection with the following description of various embodiments and configurations of the device, reference symbols are also used that relate to FIGS. 1 to 3 and 5 to 7, without the information pertaining to these reference symbols or parts are described again with reference to FIGS. 9 to 11. In addition, it should be expressly pointed out that in the description of the various exemplary embodiments, as shown in the figures, not all components and method steps are described again for an embodiment if they have already been described or explained using another embodiment. Accordingly, the description of the various components for one embodiment can be transferred to the respective components of another embodiment without this being expressly mentioned.

The device of FIG. 9 comprises at least one laser beam unit 10, the laser radiation LS, which has a beam axis B _A and a beam diameter D _s , via an optical fiber 11 and an output device 12 of a first galvano scanner unit 13 and from there a second galvano scanner unit 14, which directs the laser radiation LS onto the component 1 via an optical system 15. Both the beam unit 10 and the first and second galvano scanner units 13, 14 are controlled via a control unit 16. The control takes place in such a way that a spot area, defined as an area irradiated with the laser radiation LS on the area of the upper side 2 of the component 1 (see cross-sectional area S in FIGS. 6A to 6E), moves along an inner circumferential section, which is a position , which corresponds to an inner circumference, the diameter D _{H of} a hole Fl to be created, and in such a way that part of the spot area S creates an overlap region O within the inner peripheral portion of the hole H.

The laser radiation LS is pulsed. However, a continuous wave laser or cw radiation can also be used. In addition, the laser light LS can with any laser source, such as a YAG laser, a CO2 laser or a disk laser. It is also possible to use the beam shape of the laser radiation, ie a distribution of the energy flux density or intensity distribution perpendicular to its beam axis B _A , for example in Gaussian form, in top-hat form or in super-Gaussian form.

The glass fiber 11 amplifies the laser light LS by reflecting the laser radiation LS inside the fiber. The diameter of the laser radiation LS emerging from the glass fiber 11 depends on the diameter of the glass fiber 11. Therefore, the radiation diameter, which is required for processing the component 1, can be set in a simple manner by exchanging the glass fiber. The radiation diameter of the laser radiation LS which strikes the upper side 2 of the component 1 can, however, also be carried out, for example, via an appropriate optical system or by using a fiber laser. When using a fiber laser, the glass fiber 11 and the control unit 16 are omitted.

With the device as shown in FIG. 9, using the method as described above with reference to FIGS. 5 and 6A to 6E, bores H with a bore diameter D _{H of} less than 1 mm can be produced.

FIG. 10 shows schematically a further device with which the method according to the invention can be carried out. This device is comparable to that of FIG. It differs from the device of FIG. 9 in that an auxiliary gas supply unit 18 is provided. An auxiliary gas is supplied to the component 1 via this auxiliary gas supply unit 18 in such a way that after drilling through in the overlapping area a mass flow of auxiliary gas flows through the bore. This auxiliary gas is used to remove melted material from the bore in the direction of the flowing auxiliary gas by the laser radiation LS. As a result, the machining accuracy of the bore H can be improved, since the melt carried out can no longer solidify on the bore wall. Oxygen, air, nitrogen gas, argon gas or a mixed gas, for example, can be used as the auxiliary gas. It is also provided that the bore H instead of an auxiliary gas is supplied with a liquid, for example water by a corresponding water jet.

As can be seen from FIG. 10, a distance DG between a nozzle outlet 19 and the top 2 of the component 1 is greater than a distance DL between the exit side of the optics 15, seen in the beam direction of the laser radiation LS, and the top 2 of the component 1, in each case in seen in the Z-direction. This setting is used to set a minimum value for the mass flow of auxiliary gas which flows through the bore and is not already discharged at the bore entry to the top of the component. If, however, an inclined hole or an inclined bore is to be drilled into the component 1, as shown for example in FIGS. 1 to 3, the distance D _{L is selected to be} greater than the distance D _G.

The auxiliary gas supply unit 18 supplies the auxiliary gas under a pressure of at least 400 kPa or more, i.e. H. in a range from 400 kPa to 1000 kPa in order to achieve an expulsion effect on the liquid melt. With the method according to the invention, in which the single pulse / percussion drilling and the trepanning drilling are carried out simultaneously, it is possible to work with very low pressures of the auxiliary gas compared to conventional methods, since in the method according to the invention the melt is essentially caused by the pressure due to the Evaporation against the laser beam direction is discharged from the bore H over the top 2 of the component 1. During the drilling, the auxiliary gas can only be supplied temporarily, and only if the drilling has taken place in the overlapping area.

Because the auxiliary gas supply unit 18 supplies the auxiliary gas laterally via the nozzle outlet 19 to the component 1, the melt can be ejected or discharged from the bore H.

The galvano scanner units 13 and 14 move the position of the spot surface S by reflecting the laser light and at the same time change the optical path of the laser radiation LS. Since this laser processing device carries out the laser processing in such a way that it always has the overlap area O, which is partially overlapped by the cross-sectional area or spot area of the laser radiation LS while moving the spot area S along the inner peripheral portion I of the hole H to be made, a hole can be machined with such a laser machining device that employs a galvano scanner unit.

The use of a galvanic scanner unit can accelerate material processing if, for example, when the machining of one hole is completed, the machining of the next hole is started only by adjusting the angles of rotation of the mirror bodies of the galvanic scanner units, whereby the laser radiation in the direction of the next Drilling is directed. It is also provided that a beam splitter is used to guide the laser radiation in order to control several optical systems at the same time. It is also provided to use optics instead of a scanner for beam shaping in order to set the distribution of the radiation in the central area O and in the edge area R of the bore H to be achieved differently for cw processing without interruptions and for pulsed processing in the time average.

Another embodiment of a device is shown schematically in FIG. In contrast to the device in FIG. 10, no galvano scanner unit is provided.

According to this embodiment, the laser radiation LS is coupled into a nozzle cutting head 20 via the glass fiber 11.

This nozzle cutting head 20 comprises an optical system 21, a lens cylinder 22 and an auxiliary gas nozzle 23.

The nozzle cutting head 20 can be moved along a direction parallel to the upper side or upper side 3 of the component 1, ie along any path of a two-dimensional coordinate plane XY, in order to move the laser radiation LS on a path along the inner circumference of a bore H to be created (see FIG FIGS. 5, 6A to 6E). Instead of moving the nozzle cutting head 20, a support table (not shown) that carries the component 1 could also be moved in order to achieve a relative movement between the nozzle cutting head 20 and the support table. However, it is advantageous if the masses to be moved are kept small.

Claims

1. Process for drilling components (1) made of metallic materials and components (1) made of layered metallic and dielectric materials by means of single pulse drilling or percussion drilling and by means of trepanning drilling with laser radiation (LS), which has a beam axis (B _A ) and a beam diameter (Ds) and with dominant melt expulsion, with the single pulse / percussion drilling and the trepanning drilling being carried out simultaneously by the spatial distribution of the Poynting vector (<S>) that is assigned to the laser radiation and is defined as the vector that points in the direction of the radiation propagation and the magnitude of which is the energy flux density of the laser radiation (LS), in an overlap area (O) of the bore to be produced (H), which has a bore axis (H _a ), a bore wall (H _w ) and a bore bottom (H _b ) that progresses with increasing bore , with the progressing end of the hole (H) being formed as drilling ungsgrund (H) is assigned, and is set differently in an edge area (R) of the hole (H) to be produced, the overlap area (O) being defined as the area that is irradiated with high energy flux density of the laser radiation during single pulse drilling , and the edge area (R) is defined as the area that lies outside the overlap area (O) and when drilling with a low energy flux density of the laser radiation (LS), less than the energy flux density in the overlap area (O), where a maximum value A _{max of} an aspect ratio A, with A = d / (2 r _{B, toP} ) has a value less than or equal to 10, where d for a vertical bore (H ) relative to the upper side (2) of the material is the material thickness of the material to be drilled through or, with an inclined bore axis (H _a ) relative to the upper side (2) of the material, the bore _length is and r _{B, t0p is} the bore _radius of the bore (H) at the bore inlet, defined as the radius measured in the direction perpendicular to the bore axis (H _a ).

2. The method according to claim 1, characterized in that the laser radiation (LS) performs a movement during drilling in such a way that the beam axis (B _A ) is moved along a closed trajectory (C) to be traversed at least once, the beam diameter ( D _s ) is at least as large as the diameter (De) of the trajectory (C).

3. The method according to any one of claims 1 or 2, characterized in that the distribution of the radiation (LS) in the overlap and edge area (O, R) of the bore to be achieved (H) is set differently in the time average.

4. The method according to any one of claims 1 to 3, characterized in that the Poynting vector (<S>) jm edge region (R) of the bore (H) has a directional component which changes with the bore depth and which points towards the bore wall (H _w ) reaching hole (H).

5. The method according to any one of claims 1 to 4, characterized in that the achievement of an asymptotics of the geometric shape of the bore (H) is ensured in that a drilling duration is determined from which the bore (H) in relation to its diameter ( DH) does not progress any further and thus reaches a final shape.

6. The method according to any one of claims 1 to 5, characterized in that the final shape of the hole is determined by setting the laser radiation (LS) on the edge area (R) and a threshold value is determined for reaching the final shape of the hole (H), which is defined as a number with the dimension W ^» cm ² for a pulse duration longer than one nanosecond or J * cm ² for a pulse duration shorter than 10 picoseconds (corresponds to 10 ^-4 W ^» m ² or J ^» m ² ), which is all otherwise known for the Drilling replaces relevant parameters for characterizing the material to be drilled and which for metallic materials assumes a typical value of 10 ⁴ to 10 ⁵ W ^» cm ² or 1 to 10 J ^» cm ² .

7. The method according to any one of claims 1 to 6, characterized in that when drilling with several pulses, the energy flux density of the laser radiation in the overlap area (O) is set so that before drilling through the material in the overlap area (O) the melt against the direction of propagation of the Laser radiation (LS) is driven out of the hole (H) and the hole bottom (H _b ) reaches the material thickness and no through hole, defined as an opening of the hole (H) at the hole bottom (H _b ) on the underside (3) of the Component (1) is present.

8. The method according to any one of claims 1 to 7, characterized in that the expulsion of the melt takes place without the use of a gas nozzle and only due to the evaporation pressure, the energy flux density in the overlap area (O) is set so that the bottom of the hole {H _b ) in Overlap area (O) reaches the bottom (3) of the component (1) at a pulse end and an asymptotic shape of the bore wall (H _w ) has not yet been reached.

9. The method according to any one of claims 1 to 8, characterized in that a minimum value for the energy flux density is not fallen below and a maximum value for the energy flux density is not exceeded, wherein the minimum value is determined that no piercing, defined as an opening of the Drilling (H) on the bottom of the hole (H _b ) on the underside (3) of the component (1) takes place and the maximum value is determined by the fact that the drilling time to reach the hole increases abruptly with the energy flux density.

10. The method according to claim 6, characterized in that the final shape of the bore by measuring the energy flux density of the laser radiation (LS) is determined in the edge region (R), the final shape of the bore being predetermined by the position of the bore wall (H _w ) at which the measured values are equal to the threshold value.

11. The method according to claim 2, characterized in that by setting a feed of the beam axis (B _A ) along the trajectory (C) of a period duration, defined as the sum of a pulse duration and a pulse pause between two successive pulses, and an increment angle (alpha) , defined as the angle by which the beam axis (BA) of the laser radiation (LS) is rotated on the trajectory (C) during a period around the bore axis (H _a ), a bore that is circular in cross section, an eight-shaped bore, an elongated bore or a three-hole or star-shaped hole (H) is created.

12. Device for drilling components made of metallic materials and components made of layered metallic and dielectric materials with a laser processing device which comprises at least one beam unit (20), the laser radiation (LS), the beam axis (B _A ) and a beam diameter (Ds) has, aimed at the component (1), and with a control unit (12) which controls the beam unit (20) in such a way that the beam axis (B _a ) and the beam diameter (Ds) have a position and a cross-sectional area of a spot area (S) characterize, defined as an area of the component (1) irradiated with the laser radiation (LS) on an upper side (2) with the beam diameter Ds, the beam axis (B _A ) moving along a closed trajectory (C), and that a part the spot area (S) creates an overlap area (O) within the trajectory (C).

13. The device according to claim 12, characterized in that the area of the overlap region (O) is smaller than the cross-sectional area with the diameter (D) of the bore (H).

14. The device according to claim 12 or 13, characterized in that the laser processing device emits the laser radiation (LS) so that the beam diameter (Ds) of the spot area (S) is greater than half the length of the The diameter (D) of the hole (H) and smaller than the diameter (DH) of the hole (H).

15. Device according to one of claims 12 to 14, characterized in that the control unit (16) controls the laser beam unit in such a way that the laser radiation (LS) covers an area of the bore in the component (1) in the radial direction to the bore axis (H _a ) seen from the overlap area (O) extended outwards.

16. Device according to one of claims 12 to 15, characterized in that an auxiliary fluid supply unit (18) is provided which delivers a fluid to the upper side (2) of the component (1) and into the bore formed in the component (1) (H) feeds.

17. Device according to one of claims 12 to 16, characterized in that the laser processing device has a beam unit (10) which generates a GE pulsed laser radiation (LS) and a galvano scanner unit (13, 14) which defines the beam axis (B _A ) , the center of the spot surface (S), is moved by reflection of the laser radiation (LS), while at the same time it changes an optical path of the laser radiation (LS) oscillated by the beam unit (10).