EP3041637A1

EP3041637A1 - Method for machining a workpiece by means of a laser beam, laser tool, laser machine, machine control

Info

Publication number: EP3041637A1
Application number: EP14761620.5A
Authority: EP
Inventors: Peter Hildebrand; Gottfried Reinicke
Original assignee: Sauer GmbH Lasertec
Current assignee: Sauer GmbH Lasertec
Priority date: 2013-09-05
Filing date: 2014-09-05
Publication date: 2016-07-13
Also published as: US10376992B2; JP2016533906A; JP6560678B2; CN109079328B; US20160193698A1; KR102137215B1; KR20180079445A; CN105658372A; KR101939801B1; WO2015032926A1; DE102013217783A1; KR20160040707A; CN109079328A; CN105658372B

Abstract

The invention relates to a method for machining a workpiece by means of a pulsed laser beam originating from a tool head, in which the pulsed laser beam is guided over the surface of the workpiece in a constant relative position between the workpiece and tool head and the workpiece can be machined in succession from a first and a second relative position. Said machining parameters are controlled in the second relative position such that one or several impact points of the laser pulses generated from the second relative position on the surface of the workpiece have a defined position with respect to one or several impact points of the laser pulses generated from the first relative position on the surface of the workpiece, in particular lying in a one or two dimensional grid which is defined by several laser pulse impact points generated from the first relative position on the surface of the workpiece.

Description

Method for processing a workpiece by means of a laser beam, laser tool, laser machine,

Machine control

The invention relates to a method for machining a workpiece by means of a laser beam and to a laser tool, a laser machine and a machine controller according to the preambles of the independent claims.

The prior art is about DE1017322A,

WO2000 / 18535, DE10324439A, DE10352402A, DE102004013475A, EP1613447A1, DE1021007012816, DE102007012815A,

DE102007016056A

FIG. 1 schematically shows a known machine tool 1. The machine 1 has a machine frame 16. Attached to it adjustable is a workpiece table 14, which holds a workpiece 11 clamped in operation. The mobility of the workpiece table 14 relative to the

Frame 16 can be set translationally and / or rotationally along one or more translatory and / or rotational axes. These axes are indicated by 15. Also attached to the machine frame 16 is a laser tool head 13. It can be interchangeable and standardized over couplings {HSK, taper shank, ...} be used and removable. Also, the tool head 13 can along one or more translational and / or rotatory axes 17 relative to the machine frame 16 be adjustable.

The laser tool head 13 emits a laser beam 12 which impinges on the surface 10 of the workpiece 11 and leads there to material liquefaction and material evaporation. The laser beam 12 is usually not a continuous laser beam but a pulsed laser light. The pulse power is regularly so high that individual pulses can cause the material evaporation in each case. By means of a scanner and a suitable optics, the laser beam, in particular its focus, is guided in the space as desired.

A controller 18 controls the laser beam 12 and in particular the position of the focus of the laser beam 12 in space via actuators in the head 13. It also controls the axes 15 and 17 and other machine components. It can generally be connected to sensor 19. The sensor 19 can, for example, measure the already created die three-dimensionally or can determine the instantaneous point of contact of the laser beam on the die and feed it to the controller 18 in an appropriately formatted manner. A memory 18a holds processing data, which may also include program data for a machining program of a CNC machine.

The workpiece 11 may be a metallic material or a ceramic or a plastic. But it can also be a coating of a carrier. The The structure to be fabricated may be a voluminous die, or some kind of surface finish that hardly penetrates the depth of the die. As an example, the following is the production of a

Injection mold for vehicle fittings adopted. The macroscopic form is already produced elsewhere and the machine described is intended to introduce a suitable surface structuring. Since a casting mold is to be made, it is necessary to produce a negative mold. The

Workpiece is relatively large and can be surfaces of

0.1 m ² or more or 1 m ² or more. With a square overall shape, this corresponds to an edge length of at least 31 cm or 1 m on the workpiece surface.

Laser heads 13 can accomplish such high deflections but usually not or only with significant quality losses. Because of this, it is often the case that the workpiece surface is divided into segments. Each segment is then processed from its own constant relative position between the workpiece 11 and tool head 13. When the machining of the segment is finished, the workpiece is moved relative to the tool head by using the axes 15 and 17 and controlled appropriately, in which case a new segment is machined in a new relative position.

Figure 2 shows the segmentation of a workpiece in a known manner. You can see the workpiece shown for example, as a cast of a button with four holes, for which stand negative in the form of the symbolized as four circles pillars. 10 is a die in the workpiece surface. It is assumed that the total size of the workpiece surface is too large to be machined out of a single relative position between tool head 13 and workpiece 11. The workpiece surface is therefore subdivided into segments 21a, 21b, 21c, 21d, the subdivision being a logical, not a real division. For each individual segments, a specific relative position between the workpiece and the tool head is then set, from which the segment is processed. Both the segmentation and the determination of the respective relative positions occur according to several criteria. One may be the optimization of the angle of incidence, another necessary to avoid shadowing or collisions. When the processing is completed in a segment, the workpiece and / or process tool head relative to each other, so that a good relative position is given for a further segment _'from which the additional segment can been be edited, etc. The workpiece surface may in 10 or Be divided into 20 or 50 or more segments. Moreover, if a die is to be fabricated in depth, the segment boundaries may be different in stratified material removal in different layers, as indicated by the gratings 21, 22, 23 in FIG. The respectively shown Grids indicate segment boundaries in different layers (z-position). Preferably, these are offset from each other, so that no artifacts on the side walls noticeably form at the boundaries, which may have discontinuities, because the effects are smeared.

Figure 3 shows one of the problems that can occur in the segmentation of workpiece surfaces. FIG. 3 a shows that the workpiece surface is divided into two segments 21 a, 21 b. For each segment, the position of the laser head 13 would be chosen so that the respective position is good or optimal relative to the current workpiece surface. Optimal would mean that on average the laser impinges approximately perpendicular to the workpiece surface, so that the power can be introduced as equal and well-defined in the workpiece to be machined. This leads to a very individual positioning of the head 13 when the workpiece surface, as shown in Figure 3a, is uneven. By 13-1 and 13-2 different positions of the head 13 are indicated.

The effect is that each segment can work optimally for itself. However, disadvantages of this approach are shown in FIGS. 3b and 3c. At the boundary between the segments 21a and 21b, the laser beams from the two positions 13-1 and 13-2 strike the workpiece surface at different angles α and β. If the diameter d of the laser beam 12 is the same in each case, it is due to the fact that different angles α and ß in adjacent, but from different relative positions generated impulse hits on the workpiece top to different projection dimensions pl and p2 on the workpiece surface. On the one hand, this leads to uneven images of the laser beam diameter on the workpiece surface (geometrical errors) and, on the other hand, or as a consequence, to uneven power densities and thus different removal behavior (ablation errors).

If individual points corresponding to the impact locations of individual laser pulses are to be introduced _"those who depend on the segment limit thereof, which side they are systematically the same

Geometry deviations. At normal incidence at segment 21b, the shape will be approximately circular, while at oblique incidence the shape will be distorted elliptical. Even if this has no functional effects, the transition of the shape along the

Segment boundaries visually usually be clearly perceptible. This is highly undesirable. These effects can also be smeared within a layer by interleaving the track boundaries between the segments. But even then inequality can become visibly or functionally noticeable.

Figure 4 shows another problem at the segment boundaries. In each relative position, the laser is guided along several rer tracks and thus generates, depending on the Guide speed and the pulse frequency fp = 1 / T, a sequence of individual impact points. If then to

Production of another segment of the relative position is adjusted, it may cause connection errors, as the control in the second _"later relative position can be correctly and evenly in itself, but not in

With respect to the situation found after machining from the first relative position. FIG. 4 shows that individual points do not adjoin one another regularly. Shown is only a connection error in the vertical direction of the drawing plane. There may also be horizontal errors in the plane of the drawing which lead to misalignment of the tracks. Once again, even if these effects had no functional effect, they are at least visually perceivable as an artifact along the segment boundary, which is again highly undesirable.

FIG. 5 shows typical laser pulses 50a, 50b and 50c along the time axis. 51 symbolizes individual impulses or groups of impulses which follow one another regularly with a period T. The period T is good and fast in most types of lasers, but only poorly or slowly controllable in some, but in any case relatively uniform and predictable. In the pulse 50a individual pulses 51 follow each other with period T. The pulse 50b is followed by double pulses of pulses 52, 53

regularly on each other, each one of the first weaker is the second one. These double pulses also define a period T with respect to one another. Pulse 50c also shows double pulses of pulses 52, 53, which may, however, be the same.

All pulses shown also show a phenomenon at power up. If it is assumed that the pulse / double pulse to be seen on the left is the first one after switching on, it is frequently observed that the first pulses are relatively strong and the subsequent ones become weaker until they reach a constant level. It therefore changes the Abtragsleistung due to this Aufangsimpulsuberhöhung shortly after switching. Expressed in diameters of the laser pulse hits, diameters of the first hits would be larger than those of the following ones.

If the power density (power per area) on the surface of the workpiece is uneven _» , the removal rates are also uneven, which can lead to removal irregularities or erosion errors. The unequal power densities may arise due to geometry errors as described above or due to the described initial pulse overshoot.

Thus, overall, it can be seen that in known segmented workpiece machining methods by means of a laser beam, it is indeed possible to work within the respective segments with desirable accuracy and that artifacts at segment connections are somewhat can be smudged, but that at the boundaries of adjacent segments discontinuities in the form of geometric errors, connection errors or Abtragsfehlem may arise that are visually perceptible and / or cause functional discontinuities. One as the other is undesirable.

The object of the invention is to specify a method for machining a workpiece by means of a laser beam and a laser tool which can be used for this purpose, which increase the accuracy of the laser control in the case of segmented workpiece machining and in particular reduce visually perceptible differences. This object is achieved with the features of the independent claims.

In a method for processing a pulsed laser beam, the laser beam is guided over the workpiece surface in a constant relative position between the workpiece and the tool head. The workpiece is machined sequentially from a first and another second relative position. The processing parameters in the second relative position are controlled such that one or more impact points of laser pulses generated on the workpiece surface from the second relative position have a defined position relative to one or more impact locations of laser pulses on the workpiece surface generated from the first relative position, in particular in a one- or two-dimensional Grid are defined by a plurality of generated from the first relative position out impact of laser pulses on the workpiece surface. With the method designed in this way, the raster, which is predetermined by the machining out of a relative position, is continued as smoothly and systematically as possible during the machining from the later relative position, so that in the ideal case

Differences or segment boundaries are no longer perceptible.

In a further method for machining a workpiece by means of a pulsed laser beam originating from a tool head, a constant

Relative position between workpiece and tool head The pulsed laser beam is guided over positions on the workpiece surface. Successively, first workpiece positions of a first workpiece surface segment are machined from a first relative position and second workpiece positions are machined out of an adjacent second workpiece surface segment from another second relative position, wherein the segments can adjoin one another in overlapping or non-overlapping fashion. The first and second segments and the first and second relative positions are determined according to two criteria, the first determines the determination of the angle of incidence in accordance with the conditions in the respective relative positions and the second determines the determination of the angle of incidence such that, preferably in parallel cutting planes Considering a considered angle of incidence of the laser beam relative to the workpiece surface in the one relative position with respect to a considered angle of incidence of the laser beam relative to the workpiece surface in the other relative position is selected, preferably so that the difference of the considered angles of incidence is reduced or falls below a predetermined maximum amount , In this method, the impact geometries of laser impulses on the workpiece surface, which are made of different relative positions (in different segments) we the, but immediately or close to each other, matched, so that the imaging geometry of the laser beam on the workpiece surface at the boundary varies less and therefore does not "jump." This also reduces abrupt functional or perceptible differences at the segment boundaries.

The workpiece positions and the relative position can be chosen so that the average angle of incidence of the laser beam relative to the workpiece surface in this relative position is not in the range of 90 ° ± 3 °.

In a method for machining a workpiece by means of a pulsed laser beam originating from a tool head, the pulsed laser beam is moved over positions on the workpiece surface in a constant relative position between the workpiece and the tool head guided, wherein successively first workpiece positions of a first workpiece surface segment of a

first relative position and second workpiece positions are machined out of an adjacent second workpiece surface segment from another second relative position, wherein the segments can overlap each other overlapping or non-overlapping. The segments are smaller than the einsteuerbare working window of the laser head and are determined in particular by subdivision of a preliminary segment, wherein the subdivision in accordance with the consideration of angles of incidence of laser beams relative to the workpiece surface in the preliminary segment and possibly. also adjoining segments occurs.

The method just described is helpful if within a segment the laser beam fill angles on the workpiece surface vary so much that the differences become noticeable even within a segment. It is then possible to subdivide a provisional segment into several smaller segments, so that within a smaller segment the variances become smaller and, if necessary, over the segment boundaries. as previously described can be matched to each other.

Insofar as angles of incidence are considered, these may be angles of the laser light axis with respect to the instantaneous local workpiece surface before the laser beam strikes, wherein structural features, the smaller than the 20 or 10 or 5 μτη away can be titled.

In a method for processing a workpiece by means of a pulsed laser beam originating from a tool head, the latter is guided over the workpiece surface and the workpiece is adjusted relative to the tool head by one or more automatically controlled or controlled adjusting axes. One or more of the adjustment axes and the pulsed laser beam from the tool head are operated simultaneously and coordinated with each other.

In this method, it is possible to avoid artefacts resulting from the discrete setting of different relative positions / segments in at least one area dimension by simultaneously using at least one mechanical positioning axis and the laser beam

Stellachsen large areas of a large workpiece "nonstop" be driven off.

In a method for machining a workpiece by means of a pulsed laser beam originating from a tool head, the pulsed laser beam is guided over positions on the workpiece surface in a constant relative position between the workpiece and the tool head, whereby first and second workpiece positions of a first and second workpiece surface segment successively a first or adjacent second Relative position to be worked out. The laser beams in the border region fall from the first relative position at a different angle to the workpiece than from the second relative position. The laser impulse impact points in one of the relative positions are in accordance with the

Positioned difference of said angle of incidence, in particular shifted from other definitions. This can be achieved ^" that different

Projection sizes of the laser beam diameter on the surface approximately in the case of Figure 3c are arranged not overlapping. It should be noted that when layered

Material removal the layers need not be flat, but can be uneven. For example, they may follow the original (uneven) surface of the workpiece or may follow the final exterior shape of the die or be uneven for other criteria. The unevenness can be achieved by a suitable choice of the scan boundaries in a segment and / or by appropriate focus control in the z direction. In a method for processing a workpiece by means of a pulsed laser beam originating from a tool head, the pulsed laser beam is guided over the workpiece surface in a constant relative position between the workpiece and the tool head. Workpiece areas delimited against each other are which is processed out of a first and another second relative position out. In several passes several layers of material are removed. The boundaries of the workpiece areas are chosen differently in a layer than in an immediately above or below layer, in particular qualitatively different or such that the boundaries in the one layer not only translationally shifted against the boundaries in the immediately above or below layer are.

For example, the segment boundaries in a layer may follow a rectangular pattern, in a following one

Layer a hexagonal pattern in a layer again following a random pattern, _"etc. Because of avoided regularity of segment boundaries is again reduces the occurrence of artifacts in the last-made product. In a method for machining a workpiece by means of a pulsed laser beam emerging from a tool head, the latter is focused and guided with an optical system and a guide in the tool head. The focal length is controlled in the depth direction in accordance with the angle of incidence of the laser beam on the tool surface.

By a specifically controlled defocusing with respect to the workpiece surface, the removal rate of the laser per pulse can be controlled. This manipulated variable can be used for the compensation of other infusion variables on the removal rate, such as the angle of incidence. The dependency can for example be such that a certain defocusing (focus position above or below the instantaneous workpiece surface) is selected at approximately perpendicular incidence, ie high power density, while the focus at oblique incidence in the

Workpiece surface is located. Variances of the removal rate due to geometrical conditions are then compensated by variances of the focus position.

A laser tool for machining a workpiece by means of a pulsed spring originating from the tool

Laser beam has a laser source, an optical system for shaping the laser light and a guide for guiding the laser light. The optical system has an adjustable optical element in the beam path, which has different optical properties, if one looks at its properties in mutually rotated, but the laser beam leading planes.

The optical element with the different optical properties in different planes can be used to compensate for differences resulting from the machining geometry. They may be similar to lenses that correct astigmatism, _" or may themselves be lenses that are made astigmatic. The measure of astigmatism and / or the

Alignment can be adjustable. Also, oval apertures may be provided, adjusting orientation is, for example, to compensate for different ovalities at segment boundaries.

In general, the machining can be performed in a constant relative position so that the points of impact of the laser light are guided over the surface segment currently to be processed by the laser beam, in particular its focus region, in two. Dimensions x and y (or with a constant focal length over a spherical surface) are deflected via galvano mirrors, the focus length is controlled as a function of the deflection (z-shifter) and, if necessary, adjusted. a light valve is keyed.

Some of the described methods or method steps can be planned in advance and mapped in a correspondingly pre-written machining program that is stored in the machine and executed during workpiece machining. However, some of the steps may or may also be controlled in real time or controlled in accordance with sensor signals.

The methods described can be used in the voluminous Gesenkbiildung by surface layered layered material removal or surface processing for optical or other purposes or for surface texturing by removal of punctiform or related structures in only one or a few layers. The workpieces can z. B. large casting molds for mass-produced plastic (thermoplastics), for example in automotive engineering. The focus position of the laser beam in the space-is- Y-PH ^ ti _v well predictable controllable. In a simplified representation (disregarding the dome-shaped geometry resulting from the oscillating mirrors), it can be stated that the deflection of the focus in the surface is effected by means of oscillating mirrors with intersecting oscillating axes (control approximately in the xy plane - see Coordinate definition in FIG FIG. 1), while in the depth direction (z-direction, away from the tool) the focus can be controlled by means of fast optical elements ("z-shift"). These components can be under continuous, rapid control of the machine controller 18 forth.

Embodiments of the invention will now be described with reference to the drawings, in which: Figure 1 shows generally schematically a machine in which the described methods and tools can be used;

Fig. 2 the segmentation of the workpiece surface, also in several layers,

3 shows sketches for explaining problems with the angle of incidence of the laser beam,

4 shows sketches for explaining problems at the edge of segments,

5 typical laser pulses, 6 shows a sketch to explain the determination of the angle of incidence of the laser beam,

7 shows schematically a laser tool,

8 shows a method for improving connections at segment boundaries,

9 shows a result of the method of FIG. 8, FIG. 10 shows schematically sketches for angle-dependent focus control. In general, in this description features can also be combined with one another if the combination is not expressly mentioned, as far as the combination is technically possible. Representations of method steps and methods are also to be understood as representations of device parts and devices or device parts and devices that implement the respective method steps or methods, and vice versa. In general, a coordinate system is used in this description, as indicated in FIG. The z direction is vertical and can be the depth direction of the die, while the x and y coordinates are horizontal. It is pointed out, however, that this is to be understood only for illustrative purposes. Because of the diverse rotational adjustment axes and complex geometries in concrete operation, it can not be fundamentally assumed that, for example, the (instantaneous or initial) workpiece surface lies in the xy plane or that the depth direction of a die is always vertically aligned.

FIG. 6 shows a method in which the effects described with respect to FIG. 3 c are reduced or avoided. It is hereby ensured that the

Relative positions between the tool 13 and workpiece surface segment 21a and 21b are each selected not only under each individual optimization, but also with mutual consideration, in particular such that the angles of incidence 'and ß' in the boundary regions of the segments 21a, 21b are matched to each other, so Also, the projection of the laser cross section on the workpiece surface in the boundary region of the segments 21a, 21b less different and at best equal or uniform.

For the determination of the respective relative positions in the individual segments between the tool head 13 and segment 21a, 21b,

Surface segments are then each at least two criteria used. One is the individual setting for the respective segment, which can take place according to the necessary criteria or optimization criteria for the respective segment, and the other is the adjustment of the settings in such a way that the angles of incidence α 'and β' are in the limit range be the same or the same. In particular, the result of the application of the one criterion can be modified by the application of the other criterion. In this case, the relative position can initially be set in a segment-immanent manner, for example as shown in FIG. 3, so that the conditions are optimally possible in the respective segment 21a, 21b, for instance by approximately the averaged angle of incidence being approximately rectangular. For this will be

Positions 13-1 and 13-2 of the laser head 13 for processing the segment 21a and 21b set. Other criteria can also be used here, such as the avoidance of shadows or mechanical collisions.

However, different angles of incidence α, β of the laser beam in the border region between the segments 21a, 21b can then result from the different relative positions. This is especially the case when the workpiece is uneven. The individual setting may then be modified as shown in FIG. 6 to shift both positions 13-1 and 13-2 to the right to 13-3 and 13-4, respectively. As a result, the ratios are no longer optimal within the individual segments, but the angles of incidence oi 'and β · (preferably viewed in one or in parallel sectional planes) are aligned with one another, so that the impingement geometries of the laser diameter are also matched to one another. so that the mentioned artifacts less or not arise.

It is also possible to proceed in a different way such that initially identical angles of incidence α 'and β' are set in the border regions and these settings then be modified according to each segment-specific criteria and optimizations for the processing of each individual segment. It may then be further assessed to weigh the effects of the two criteria against each other on how much is gained on the one hand and lost on the other hand, if, according to one or the other criterion,

Changes to the settings are made in order to arrive at a defined result. ni sp procedural steps can be carried out automatically in advance in work planning. The results can then be reflected in a machining program that adjusts the respective parameters when it runs during the concrete workpiece machining.

A result of the approximation of the angles of incidence in the border region of adjoining segments may be that at least in one segment the average angle of incidence, not as a priori desired, is optimally perpendicular, but suboptimally displaced from the vertical, say at least 3 ° or at least 6 °.

Insofar as angles of incidence are considered, these can, unless otherwise stated, be angles of incidence of the laser beam on the workpiece surface in the respective border area, or average angles of incidence over the workpiece surface entire segment. Angle α and 180 ° -ex are considered equal.

FIG. 8 shows a method which serves to reduce or avoid connection errors at segment boundaries, as shown in FIG. 4, in order to arrive at a result as shown in FIG. Shown is the procedure in individual segments along

Traces that are vertical in the drawing plane. In this case, all tracks are first traveled in a segment 21a by means of the laser scanner by laser and scanner are controlled accordingly. Thereafter, the relative position by means of the mechanical adjusting axes 15 and 17 is changed so that the adjacent segment can be edited by the traces can be traced there with the scanner.

The controller operates in such a way that in the later (second) relative position the machine parameters (relative positioning, laser control,,...) Are set so that the laser impulse impact points in the second segment have a defined position with respect to the laser impulse impact points in the first segment , in particular such that they are defined to, in particular in a grid, which is predetermined by the impact points in the processing of the first segment. The predefined screening and the following connection thereto can be viewed one or two-dimensionally. In this case, it is possible to proceed as shown in FIG. 8 after the workpiece machining has ended out of a first relative position. In step 801, the laser operation is started so that laser pulses are generated. But you can still be hidden by a shutter (light valve). Before or thereafter, in step 802, the relative positioning of the laser head and workpiece for processing the new segment in the vicinity of the previously processed segment is set and, if necessary, adjusted. sensory accurately determined. In step 803, the laser pulse timing is detected in phase within the period T of the laser pulses.

In step 804, the mechanical parameters are set to achieve a defined insertion and impact of the laser pulses in the new segment. These specifications may include the start time of the scanner operation, the acceleration of the scanner, the final speed (angular velocity) of the laser. Also the

Opening time of the shutter can be determined here. In step 805, the scanner is then started in accordance with the determined sizes. When the desired setpoints are reached, in step 806 the shutter is opened so that laser pulses impinge on the workpiece surface.

In particular, when the laser pulse frequency is not or only insufficiently controllable, after the laser has been switched on, the respectively present pulse timing can be used as an input variable for the determination of the Values are used in step 804. On the other hand, if the frequency and / or phase of the laser pulses are controllable, they too can be set as a result of the determinations in step 804 and then adjusted accordingly.

The stipulations are made in such a way that the desired result is achieved, namely that the points of incidence of the laser pulses in the new relative position, ie in the new, adjacent segment, the grid in a raster dimension or in both raster dimensions continue as accurately as possible by the processing of the previous segment. In order to meet the desired specifications in step 804 _"can be sensory obtained and then used either data relating to the previous processing, for example, the impingement oints in the previous processing are measured optically, or, if present, can fall back on already existing stored values be used when processing, z. B. the laser control or regulation in the processing of the previous segment have been stored. In this way, information about the already given grid can be generated. However, if the machining is so mechanically determined that the theoretical machining positions (points of impact of the laser pulses on the surface of the workpiece) correspond to the real one with sufficient accuracy, the definitions in Step 804, also with reference to the theoretical values in the previous segment.

In this way, when the new segment 21b is machined from the new relative position, the laser pulses impinge on the workpiece surface as accurately as possible in one or both surface dimensions of the grid, so that the errors shown in FIG. 4 are avoided and the error shown in FIG 9 result is achieved.

It is also possible, in the new relative position, to carry out one or more test runs with weak or attenuated laser light without a processing effect, to sensually record their results (impact positions of the laser pulses), to vary parameters set in accordance with the detected results or to set new ones and then with To undertake the workpiece processing in the parameters thus created.

In general, it is pointed out that sensor system 19 can optionally be provided so that the currently existing die (intermediate result of the production) can be measured very precisely in real time two or three-dimensionally during the workpiece production or impact points during the test runs just described, and that the measured values in the memory device 18a in real time (during the workpiece production) can be stored retrievable. The survey can be done in high resolution to x, y and z, so that a "map" of the hitherto manufactured segments can be stored with high resolution in any case so accurately that the real grid is known or can be determined from it. The sensor 19 may be designed so that it can accurately detect the impact of laser pulses on the workpiece surface two- or three-dimensional. The sensor system 19 can be an optical sensor system which either evaluates the process illumination of the laser ablation or which takes pictures in the manner of a camera, which are evaluated automatically.

The adjustment of relative positioning in step 802 may be done according to predetermined / programmed parameters, while the determinations in step 804 and the previous necessary acquisitions in real time may be made immediately during workpiece machining. To avoid segment boundaries, as far as possible, the laser head 13 and the mechanical actuator axes 15, 17 can also be operated simultaneously and in a coordinated manner. In a simple case, for example, a translational adjusting axis 15, for example, of the workpiece table 14 can be moved slowly continuously in one direction, while at the same time

Laser tool 13 works by the scanner and the laser are controlled appropriately. In this way, even a large workpiece in at least one dimension be traveled continuously without segment boundaries, so that the number of segment boundaries decreases.

The segments may then be straight or curvilinear "processing strips" that extend over all or at least part of the workpiece surface. There are no more processing limits along the strip direction. They then need to be considered only for adjacent stripes and edited as previously described. The processing and consideration may be as described with reference to FIGS. 6 and 8.

If successive first and second workpiece positions of a first or second workpiece surface segment are machined out of a first or adjacent second relative position and the laser beams in the border region from the first relative position at a different angle to the workpiece than from the second relative position, the Laserimpulstreffstellen positioned in one of the relative position (also) in accordance with the difference of said angles of incidence, in particular shifted from (offset from) other definitions.

In particular, oval impact sites can be evacuated away from less oval impact sites, and / or conversely, less ovals are brought closer to more oval ones. As a quantitative measure of this, the degree of overlap or the distance from adjacent laser pulse be a match. In this way, at the boundary or in the boundary area, the overlaps are adjusted to each other (i.e., difference smaller) or made equal. The points of impact may be positioned or modified from other determinations such that at the segment boundary, and preferably also within the border region of the second segment, the overlaps of the impulse impact sites are the same as in the border region of the first segment, if constraints already exist from other criteria available.

The ovality ov can be expressed as the ratio ov = dmax / dmin of the maximum to the transverse to the minimum diameter of the image of the laser beam on the workpiece surface (approximately an ellipse). When assuming a circular laser beam cross section, it can also be determined from the angle of incidence of the laser beam relative to the local workpiece surface via the relationship o = 1 / sin (ex). In general, a right angle of incidence (90 °) and around it "relatively small deviations" of ± 30 ° are preferred, which corresponds to ovalities between 1 and 1, 15. But in finely structured or very wavy dies or

Structures in the workpiece can be local - together with the angular deflection of the laser beam through the

Scanner - also very oblique to almost abrasive angle of incidence (a <45 °, <30 °) arise, so that the ovalities ov> 1.4 or ov> 2 can arise. The offset direction may be the direction of the major axis of the larger oval, or the raster direction closer to the major axis of the oval. This can be achieved that different

Proj ektionsgrößen the laser beam diameter on the surface approximately in the case of Figure 3c are arranged not overlapping. In the case of FIG. 3 c, for example, the oval impact points in the left-hand segment 21 a can be displaced to the left, so that they do not overlap in the boundary region.

FIGS. 4 and 9 show segment boundaries at right angles or cutting edges to machining tracks. However, the same considerations apply to segment boundaries parallel to machining tracks. Track pitch, track direction and location of the hits in the edge tracks must then be suitably set so that the production of the new relative position is as accurate as possible in the grid defined by the earlier processing.

Segment boundaries can, but need not be defined in a straight line. In any case, they are ideal boundaries. When the laser pulse hits raster distinguishable

Define hits can be selected or modified during work planning and programming and / or on an ad hoc basis during piece processing so that individual hits are unambiguously assigned to one of the other segments. It is generally pointed out that the methods described in this description can not be used individually in each case but can also be combined with one another.

Material can be removed in several layers. One layer is composed of traces of laser impingement points. Within the track, the laser impingement sites may be related / overlapped, but need not, and adjacent traces may be related / overlapping, but need not, so that a layer may be removed selectively or in a striped or planar manner. If in a relative position between the laser head and the workpiece within a layer of the removal as desired is complete or track by train or selectively done, can either to a new

Relative position can be transferred, or it can be removed at the same relative position in another (lower) layer. The layers can, but need not, be flat, as stated above. Using the z-shifter, the focus position may also be in z depending on the instantaneous deflection of the laser (either angularly determined or x-y

determined) _» so synonymous not flat

Layers can be controlled.

If several layers are to be removed and work is performed segmented in each layer, the segment boundaries in the individual layers can be selected qualitatively differently. Maybe they can in the be a layer at right angles, hexagonal in the following layer, randomized in a subsequent layer, such as Voronoi. In principle, the segment boundaries may also be random in all layers, for example by Voronoi line patterns between quasi-randomly selected points.

This differs from the known procedure according to FIG. 2 in that, in FIG. 2, the segment boundaries in the different layers are merely displaced in translation relative to one another in order to prevent the build-up of artifacts on the die walls. However, the qualitatively different segment boundaries in the successive layers, as described, do not lead to artifacts which would lead to an unevenness of the removal even during the removal. If different angles of incidence can not be avoided at segment boundaries, one or more compensation strategies or compensation steps can be carried out, in particular in the case of flattening angles of incidence

- Introduction of a preferably angle-dependent

Offsets at the beginning of the track so that overlaps corresponding to the different ovalities are avoided by pulling apart Increasing the laser power in order to keep the power input per area constant in larger oval impact locations. Increasing the scanning speed in track direction to further pull the impact locations apart to keep the overall power input per area approximately constant Impact geometries in the boundary region can be compensated by beam shaping, in particular shaping of the beam cross section, for example by astigmatic lenses, oval diaphragms or the like.

Another way to control the power input per area is to selectively adjust the focal position relative to the workpiece surface, as shown by way of example in Figures 10a and 10b.

FIG. 10a shows the laser source 71, which emits the laser beam 12 {pulsed). Among other things, it passes through the adjustable focus 73 ("z-shifter"), with which the focal length of the optics and thus the focus position can be adjusted quickly Workpiece 11 is shown displaced 77 symbolizes the scanner, which works with oscillating mirrors ("galvo mirrors").

Since according to the different angular positions of the mirror 77 of the beam 12 under different Angle a. impinges on the workpiece surface, the already described with reference to Figures 3b and 3c different images of the beam diameter on the workpiece surface. Accordingly, the power input per area changes. This can be compensated by controlling the focal position above or below the workpiece surface, depending on the angle.

In particular, the control can be such that, when the impact is nearly vertical (= 90 ° = n / 2), a maximum height hmax of the focus 12a above or below the workpiece surface is set. As a result, the non-existing geometric distortion is compensated by an optical expansion. At smaller angles of incidence, the geometric distortion becomes larger. Accordingly, the optical beam spread can be made smaller by making the height h above or below the workpiece surface smaller until it becomes, and then remains, at a selected angular position, for example 90 ° to -30 °. In this way geometric distortions can be approximately compensated by optical beam spreads or beam confinements.

Fig. 10b shows a corresponding characteristic curve. The height h of the focus 12a above or below the surface of the workpiece 11 is at maximum incidence at maximum hmax and decreases left and right thereof. Both the height hmax and the other characteristic parameters are chosen such that the best possible overall distribution over the possible range of the angle a results. The height difference h can already be stored permanently in the predefined processing program or can be applied in real time dependent on the angle or superimposed on other control or regulation criteria.

FIG. 7 shows a laser tool. It may, for example, be the processing head 13 in FIG. However, certain components may be provided separately from the actual tool head 13 that can be inserted into the machine, such as the physical laser light source 71 and an associated optics 72. Together, they can form a light source 70 which is provided independently of the processing head 13 and the ge - Pulsed laser light generated »is guided or brought freely into the processing head 13 and then there as

Source light is available.

The machining head 13 has components for

Beam shaping and components for beam guidance.

Generally speaking, the machining head 13 is in communication with the controller 18. In particular, actuators in the processing head 13 can be adjusted in accordance with commands from the controller 18. With 77 two oscillating mirrors are referred to, which have crossing vibration axes and by means of which the laser beam can be guided over the surface. They are often referred to as "scanners" or "gazec mirrors." With 73, there is an adjustable focus of the

Lasers, the so-called "z-shifter". He agrees the focal length of the optics and thus the position of the focus 12a of the laser beam in the propagation direction, which can be considered simplified as z-direction. The z-shifter is a fast optical component »that can be changed quickly and in real time under the influence of the control and, for example, can set and change the focus depending on the x and y.

74 designates a fast adjustable optical lens which acts astigmatically, ie has different focal lengths in different spatial planes, which however all guide the laser beam. The astigmatism can be automatically adjusted in strength and position quickly in real time, such as by using pressure-sensitive or deformable optical materials that can be pressurized with appropriate piezo elements or other actuators under the influence of the control, or the like. The different breaking behavior is then controllable in size and orientation and can be used by the controller 18 of the machine to compensate for other factors, in particular the already mentioned several times different imaging geometries on the surface, as described in Figure 3b. 75 symbolizes a diaphragm whose aperture is smaller than the laser cross section and which is not circularly symmetrical and can therefore partially shadow the laser beam as well. It may also be adjustable in its unevenness and subjected to the control intervention by the controller 18. The aperture 73 can a mode aperture, so an aperture that hides edge rays.

76 symbolizes an adjustable damping, by means of which the laser power can generally be reduced quickly. It is under the influence of the controller 18.

The z-Shifter 73 is provided in virtually all scanners and laser heads to quickly adjust the position of the focus point targeted. One or more of the mentioned optical elements, astigmatic lens 74, aperture 75 and damping 76 may additionally be provided. All elements are under the influence of the controller 18 and can be used to compensate for irregularities resulting in particular from uneven geometric images of the laser cross section on the current workpiece surface. This compensation can be done in real time (during the

Workpiece machining) happen and be set variably. Again, previously stored values or values from the sensor 19 can be used as input variables for the determinations to be made. The

Adjustability can be so fast that it can be tracked to the respective current positions of the laser beam, to make adjustments even within a track. For example, when the laser beam is guided along a track from one end of a segment to the other end of the segment and thereby the If the angle of incidence changes from 70 ° to 30 ° to 110 ° and, accordingly, the projection of the laser beam cross section changes from oval to circular and then again oval, then the astigmatism of a lens can be tracked so that it changes

Ovality is compensated by the beam cross-section is adjusted by the adjustable astigmatism of the lens compensating in its ovality. Similar considerations apply to the mentioned aperture or

oden loin and for the mentioned attenuation.

Many of the above features are designed as a control of a CNC machine or a programmable machine tool. In that regard, a machine control, which is designed to initiate or execution of a method as described above on or with a machine tool, an aspect of the invention. Many of the mentioned features can be implemented by software running in a controller of a CMC machine or programmable machine tool. In that regard, is also a disk with computer-readable, code on it, when running in a CNC machine, a method or a machine or a

Machine control as described above implements an aspect of the invention.

Typical concrete values are: Laser type: fiber laser or ultrashort pulse laser

Wavelength: 100 to 2,000 nm, esp. 300 to 1,100 nm

Laser pulse frequency> 20 kHz,> 50 kHz,> 500 kHz,> 1 MHz,> 2 MHz,> 5 MHz

Adjustability of pulse frequency and / or

Amplitude: "slow" track by track or "snow 1" from P ls to pulse

Segment size> 10 mm,> 20 mm,> 50 mm,> 100 mm Number of segments in the workpiece> 10,> 50,> 100

Laser diameter in focus corresponding to the diameter of the pulse hits at normal focused incidence: 10 μπι

- 100 μτα

Oval itat ov = dmax / dmin> 1.1,> 1.4,> 2

Layer thickness d corresponding to the removal depth of a pulse: Lower limits 1 μν or 2 im, upper limits 5 μτη or 10 μτα

Laser pulse power: Lower limits 0, 1 mJ or 0, 2 mJ or 0.5 mJ, upper limits 2 mJ or 5mJ or 10 mj

Deflection laser beam: up to +/- 30 °

Angle of incidence of the laser beam with respect to local workpiece flat: 90 ° ± 30 ° to 90 ° ± 70 °

Path speed of the laser beam> 500 mm / s,> 1,000 mm / s,> 2,000 mm / s> 5,000 mm / s

Workpiece size> 0, 1 m ^A 2 or> 1 m ^A 2 or> 30cm or> 1 m

Claims

claims

A method of machining a workpiece by means of a pulsed laser beam emanating from a tool head, in which the pulsed laser beam is guided over the workpiece surface in a constant relative position between the workpiece and the tool head and wherein the workpiece is processed successively from a first and another second relative position, characterized in that the processing parameters in the second relative position are controlled such that one or more impact points of laser pulses on the workpiece surface generated from the second relative position define a defined position with respect to one or more impingement locations of laser pulses generated on the first relative position Have workpiece surface, in particular lie in a one- or two-dimensional grid, which is defined by a plurality of out of the first relative position generated by impact of laser pulses on the workpiece surface.

2. The method of claim 1, wherein the controlled processing parameters include one or more of the following quantities:

the second relative position,

- the turn-on time of the pulsed laser beam

the opening time of a light gate, the deflection of the laser beam at the time of connection,

the pulse frequency of the laser beam,

the web speed of the bearing beam on the workpiece surface,

3. The method according to claim 1 or 2, characterized in that the control of the impact points from the second relative position also in accordance with

Measurement results and / or stored in accordance with stored values of sizes in the workpiece machining from the first relative position out.

4. The method according to any one of the preceding claims, characterized in that in the second relative position one or more mechanical parameters, in particular the laser guidance, are controlled in accordance with laser parameters, in particular in accordance with the pulse times.

5. A method for machining a workpiece by means of a tool head springing from a pulsed laser beam, preferably according to one of the preceding claims, wherein seen in a constant relative position between the workpiece and the tool head of the pulsed laser beam over positions on the workpiece surface, wherein successively first workpiece positions of a first workpiece surface segment from a first relative position and second workpiece positions from an adjacent second workpiece surface segment another second relative position, the segments being able to adjoin one another in overlapping or non-overlapping fashion, characterized in that the first and second segments and the first and second relative positions are determined according to two criteria,

the first of which determines an optimization of the angles of incidence in the respective relative positions, and

the second of which determines the definition of the insertion angle such that, preferably in parallel

Considering sectional planes, a considered angle of incidence of the laser beam relative to the workpiece surface in the one relative position with respect to a considered angle of incidence of the laser beam relative to the workpiece surface is selected in the other relative position, preferably such that the difference of the considered angles of incidence is reduced or below a predetermined maximum amount falls.

6. A method according to claim 5, characterized in that the angle of incidence considered for at least one of the two relative positions is a mean angle of incidence in this relative position or an angle of incidence at workpiece positions in the boundary region of the segment, in particular those of the associated workpiece positions that are at workpiece positions in the adjacent to other relative position.

7. The method according to claim 5 or 6, characterized in that the second criterion of the amount of

Differences, preferably in parallel cutting planes _{»is set} to less than 20 ° or less than 15 ° or less than 10 °.

8. The method according to one or more of claims 5 to 7, characterized in that first the first criterion is applied and the resulting ratios are modified in accordance with the second criterion, or that first the second criterion is applied and the resulting conditions after Massgäbe the first criterion to be modified.

9. A method for machining a workpiece by means of a tool head springing pulsed laser beam, preferably according to one of the preceding claims, wherein in a constant relative position between the workpiece and the tool head of the pulsed laser beam is guided over positions on the workpiece surface, characterized in that the workpiece positions and the relative position are chosen so that the average angle of incidence of the laser beam relative to the workpiece surface in this relative position is not in the range of 90 ° ± 3 °.

10. A method for machining a workpiece by means of a pulsed laser beam emanating from a tool head _» preferably according to one of the preceding claims, in which the pulsed laser beam is guided over positions on the workpiece surface in a constant relative position between the workpiece and the tool head, whereby first workpiece positions of one first workpiece surface segment from a first relative position and second workpiece positions are processed from an adjacent second workpiece surface segment from another second relative position, the segments overlapping or not overlapping adjacent to each other, characterized in that the segments are smaller than the controllable working window of the laser head and, in particular, by dividing a preliminary segment, the division according to the consideration of angles of incidence of laser beams with respect to the Workpiece surface in the preliminary segment and possibly also adjacent thereto segments.

11. Method for processing a workpiece by means of a pulsed laser beam originating from a tool head, preferably according to one of the preceding claims, in which the pulsed laser beam is guided over the workpiece surface and the workpiece is guided by one or more automatically controlled or regulated positions. Salmon relative to the tool head is adjusted, characterized in that one or more of the adjusting axes and the pulsed laser beam from the tool head are operated simultaneously and coordinated.

12. A method for machining a workpiece by means of a tool head springing pulsed laser beam, preferably according to one of the preceding claims, wherein in a constant relative position between the workpiece and the tool head of the pulsed laser beam is guided over positions on the workpiece surface, wherein sequentially first workpiece positions of a first workpiece surface segment from a first relative position and second workpiece positions from an adjacent second workpiece surface segment are machined out of another second relative position, the segments overlapping or not overlapping adjacent to each other, wherein the laser beams in the border region from the first relative position at a different angle to the workpiece as from the second relative position, characterized in that the laser impulse impact points in a relative position in accordance with the difference of said incident angle be postponed, in particular be shifted from other provisions.

13. The method according to any one of the preceding claims, characterized in that several layers of material are removed at the same points of the workpiece surface in several passes.

14. A method of machining a workpiece by means of a pulsed spring originating from a tool head

Laser beam, preferably according to one of the preceding claims, wherein in a constant relative position between the workpiece and the tool head, the pulsed laser beam is guided over the workpiece surface and wherein mutually delimited Werkst ckbereiche successively processed from a first and another second relative position, and wherein in several Passing through several layers of material to be removed, characterized in that the boundaries of the workpiece areas are selected differently in a layer than in an immediately above or below layer, in particular qualitatively different or so that the boundaries in the one layer not only translationally against the boundaries are shifted in the immediately above or below layer.

15. Method, preferably according to ei em of the preceding claims, for machining a workpiece by means of a tool head springing pulsed laser beam, de with an optics and a guide in the tool head is focused and guided, characterized, the Fokusläge in the depth direction in accordance with Incident angle of the laser beam is controlled on the tool surface.

16. The method of claim 15, wherein the distance of the laser focus from the workpiece surface is larger when the angle of insertion approaches a right angle.

17. The method according to one or more of the preceding claims, characterized in that surface structuring of individual or a few contiguous laser pulse impingement points are generated.

18. Apparatus for carrying out the method according to one or more of the preceding claims.

19. Tool for machining a workpiece by means of a tool originating from the pulsed laser beam mi with a laser source, a lens for shaping the laser light and a guide for guiding the laser light, characterized in that the optical system in the beam path has an adjustable optical element having different optical properties, if one considers its properties in mutually rotated, but the laser beam leading planes.

20. Tool according to claim 19, characterized in that the adjustability of the optical element comprises the adjustment of its orientation and / or the difference in the twisted planes and / or the insertion or removal of the optical element in or out of the beam path ,

21. Tool according to claim 19 or 20, characterized in that the element is a lens which has different focal lengths in the mutually rotated planes, or a diaphragm which has different aperture dimensions in the mutually rotated planes.

22. Control for a device according to claim

18th

23. Data carrier with computer-readable code thereon, which in the execution of a method according to one of Claims 1 to 17 or forms an apparatus according to claim 18 or a controller according to claim 22.