Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/352—Working by laser beam, e.g. welding, cutting or boring for surface treatment
  • B23K26/356—Working by laser beam, e.g. welding, cutting or boring for surface treatment by shock processing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/352—Working by laser beam, e.g. welding, cutting or boring for surface treatment
  • B23K26/354—Working by laser beam, e.g. welding, cutting or boring for surface treatment by melting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
  • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
  • B23K26/0648—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/08—Devices involving relative movement between laser beam and workpiece
  • B23K26/082—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/36—Removing material
  • B23K26/361—Removing material for deburring or mechanical trimming

Definitions

• 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.
• 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.
• 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 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.
• 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.
• 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.
• the workpiece surface may in 10 or Be divided into 20 or 50 or more segments.
• 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.
• FIG. 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.
• 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.
• 13-1 and 13-2 different positions of the head 13 are indicated.
• each segment can work optimally for itself.
• disadvantages of this approach are shown in FIGS. 3b and 3c.
• the laser beams from the two positions 13-1 and 13-2 strike the workpiece surface at different angles ⁇ and ⁇ .
• the diameter d of the laser beam 12 is the same in each case, it is due to the fact that different angles ⁇ 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.
• 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).
• 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.
• 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.
• 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.
• the pulse 50a individual pulses 51 follow each other with period T.
• the pulse 50b is followed by double pulses of pulses 52, 53
• 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 Abtrags antique 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.
• 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.
• 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.
• 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.
• 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 ,
• 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 °.
• 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 ein Kunststoffbare 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.
• angles of incidence 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 ⁇ away can be titled.
• a pulsed laser beam originating from a tool head 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.
• 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
• 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
• 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.
• 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.
• 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.
• segment boundaries in a layer may follow a rectangular pattern, in a following one
• 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
• 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.
• 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 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.
• Figure 1 shows generally schematically a machine in which the described methods and tools can be used
• FIG. 9 shows a result of the method of FIG. 8
• FIG. 10 shows schematically sketches for angle-dependent focus control.
• 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.
• 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.
• 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.
• 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 ⁇ 'and ⁇ ' are in the limit range be the same or the same.
• the result of the application of the one criterion can be modified by the application of the other criterion.
• 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.
• 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 °.
• angles of incidence 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 ⁇ 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
• 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.
• step 803 the laser pulse timing is detected in phase within the period T of the laser pulses.
• 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.
• the scanner is then started in accordance with the determined sizes.
• the shutter is opened so that laser pulses impinge on the workpiece surface.
• the respectively present pulse timing can be used as an input variable for the determination of the Values are used in step 804.
• 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.
• 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.
• Step 804 the definitions in Step 804, also with reference to the theoretical values in the previous segment.
• 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.
• the laser head 13 and the mechanical actuator axes 15, 17 can also be operated simultaneously and in a coordinated manner.
• 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.
• the Laserimpulsschreibstellen 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.
• oval impact sites can be evacuated away from less oval impact sites, and / or conversely, less ovals are brought closer to more oval ones.
• the degree of overlap or the distance from adjacent laser pulse be a match.
• 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.
• 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).
• o 1 / sin (ex).
• 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
• the laser beam diameter on the surface approximately in the case of Figure 3c are arranged not overlapping.
• 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
• 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.
• the focus position may also be in z depending on the instantaneous deflection of the laser (either angularly determined or x-y
• 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.
• 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").
• the non-existing geometric distortion is compensated by an optical expansion.
• 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 are Beam shaping and components for beam guidance.
• the machining head 13 is in communication with the controller 18.
• actuators in the processing head 13 can be adjusted in accordance with commands from the controller 18.
• 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.”
• scanners or “gazec mirrors.”
• gazec mirrors there is an adjustable focus of the
• the 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.
• 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
• 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
• 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.
• 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
• Segment size 10 mm,> 20 mm,> 50 mm,> 100 mm Number of segments in the workpiece> 10,> 50,> 100
• Layer thickness d corresponding to the removal depth of a pulse Lower limits 1 ⁇ or 2 im, upper limits 5 ⁇ or 10 ⁇
• 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
• 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

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