CN111069787A

CN111069787A - Method for machining a workpiece and machining device

Info

Publication number: CN111069787A
Application number: CN201910993011.7A
Authority: CN
Inventors: B·雷加德; M·黑克尔; M·朔贝尔
Original assignee: Trumpf Werkzeugmaschinen SE and Co KG
Current assignee: Trumpf Werkzeugmaschinen SE and Co KG
Priority date: 2018-10-19
Filing date: 2019-10-18
Publication date: 2020-04-28
Anticipated expiration: 2039-10-18
Also published as: CN111069787B; DE102018217940A1

Abstract

The invention relates to a method for machining a workpiece (8) by means of a machining beam, comprising: before processing: a) moving the machining head and the workpiece (8) relative to each other along a predetermined desired movement path (9 '), b) determining a relative movement between the machining head and the workpiece (8) by means of an optical detector fixedly connected to the machining head while moving along the predetermined desired movement path (9'), and c) determining a corrected desired movement path (9) on the basis of the determined relative movement, the method further comprising: the workpiece (8) is machined by moving a machining head, which directs a machining beam onto the workpiece (8), and the workpiece (8) relative to each other along the corrected intended movement path (9). The invention also relates to a corresponding processing machine for processing workpieces (8). The invention also relates to a further method for machining a workpiece (8) by means of a machining beam, and to a corresponding machining machine.

Description

Method for machining a workpiece and machining device

Technical Field

The invention relates to a method for machining a workpiece by means of a machining beam. The invention also relates to a processing machine, in particular a laser processing machine, for processing a workpiece, comprising: a processing head for processing the workpiece, the processing head being configured for directing a processing beam onto the workpiece; a movement device for moving the machining head and the workpiece relative to each other, and an optical detector fixedly connected to the machining head.

Background

In the case of machining, for example, plate-shaped workpieces, in particular sheet metal, by means of a machining beam, in particular in the case of laser cutting by means of a laser beam, component tolerances occur on the workpiece parts to be cut, which tolerances can be attributed to deviations of the actual movement path produced during laser cutting from a predetermined desired movement path. Such deviations can be caused by dynamic forces during the relative movement between the machining head and the workpiece during machining: in particular at high machining speeds, vibrations of the gantry system to which the machining head is fastened or of the robot, or vibrations of the workpiece or workpiece carrier, which lead to overshoots during the cutting along the cutting contour, may occur.

DE102006017629a1 describes a method for laser machining a workpiece along a predetermined machining path, in which a deviation of an actual position from a desired position occurring during a relative movement of the workpiece and the laser machining head is sensed and a correction value for deflecting the laser beam into the desired position is determined therefrom, and the laser beam is deflected accordingly. An overshoot can be detected during the relative movement between the workpiece and the laser processing head, and a deflection of the laser beam opposite the relative movement can be set.

DE102006049627a1 describes a method and a device for fine positioning of a tool in which the relative movement between the tool and the object to be machined is sensed by means of at least one sensor and the deviation of the actual movement path of the tool or the object calculated therefrom from the intended movement path is compensated by means of an actuator by tracking the tool or the object.

It is also proposed in DE102006049627a1 to sense the relative movement by illuminating the surface of the object with optical radiation in the region of the machining point and repeatedly sensing the optical radiation reflected from the object surface in the region of the machining point by means of a camera in order to obtain temporally successive optical reflection patterns of overlapping surface regions of the object. The lateral relative movement is determined by comparing temporally successive reflection patterns, as described in detail in DE102005022095a 1.

Disclosure of Invention

The object on which the invention is based is to provide a method and a processing machine by means of which the contour accuracy can be increased during the processing of a workpiece along a desired movement path.

This object is achieved according to a first aspect by a method for machining a workpiece by means of a machining beam, comprising: before processing: a) moving the machining head and the workpiece relative to each other along a predetermined desired movement path, b) determining the relative movement between the machining head and the workpiece during the movement along the desired movement path by means of a detector fixedly connected to the machining head, and c) determining a corrected movement path on the basis of the determined relative movement, wherein the method further comprises: the workpiece is machined by moving the machining head, which directs the machining beam onto the workpiece, and the workpiece relative to each other along the corrected intended motion trajectory.

In this respect, it is proposed that track deviations which occur during the machining of the workpiece as a result of relative movements between the machining head and the workpiece and which can be attributed to shaft vibrations or the like are corrected by: before the machining, a predefined desired movement path is traversed before the workpiece is machined and deviations occurring are corrected if necessary. In this way, it is possible to dispense with the adjustment of the relative movement by means of the actuator during the machining of the workpiece, as is described, for example, in DE102006049627a 1. In this case, the predefined desired movement path is typically also traveled at the relative speed or feed speed at which the subsequent processing is carried out.

The method can be used, for example, in a machining machine for machining flat surfaces, for example, in a 2D laser cutting machine. In such a processing machine, the processing head is usually moved in two dimensions (X/Y direction) over the workpiece and the workpiece remains stationary. In this case, the movement of the processing head and the workpiece relative to each other corresponds to a movement of the processing head along a predefined desired path relative to the stationary workpiece or a machine frame of the processing machine. Instead of cutting by means of a machining beam, for example, a welding process can be carried out by means of a laser beam.

In one variant, the determination of the relative movement comprises: irradiating the workpiece surface with an illumination radiation in the region of the machining head, sensing the illumination radiation reflected on the workpiece surface in the region of the machining head in a spatially resolved manner in order to obtain temporally successive reflection patterns of overlapping surface regions of the workpiece when moving along a predefined desired movement path, and determining the relative movement by comparing the temporally successive reflection patterns.

By comparing temporally successive reflection patterns, a relative movement or a lateral movement of the surface region can be determined, for example, in the manner described in DE102006049627a1 or DE102005022095a1, typically by calculation of a similarity function, see also pages 67-74 of the paper "geometriebasierte procedure ü berwachung und-regluging beim laserstahlschwei β en dual koaxialee beachhtung DEs schmelzzdes fremdbleuchhtung" (process monitoring and adjustment based on the geometry by observing the weld puddle coaxially by means of external illumination) in b.regaard, aac, aard is published, the content of the application is incorporated by reference, for determining the relative movement or lateral offset, the local image portion of the reflection pattern of the overlapping surface region having the greatest similarity should be determined by means of the similarity function, the deviation should be determined in the movement trajectory along the given position, the relative movement trajectory should be calculated, the deviation should be calculated in accordance with the given movement trajectory, the relative movement trajectory should be calculated in the given direction, and the relative movement should be offset.

Another aspect of the invention relates to a method for machining a workpiece by means of a machining beam, comprising: before processing: a) moving the machining head and the workpiece relative to each other along a predetermined desired movement path at a first relative movement speed, and moving the machining head and the workpiece relative to each other along a predetermined desired movement path at a second, greater relative speed, b) determining a deviation between the movement along the predetermined desired movement path at the first relative speed and the movement along the predetermined desired movement path at the second relative speed by means of a detector fixedly connected to the machining head, and c) determining a corrected desired movement path on the basis of the determined deviation, wherein the method further comprises: the workpiece is machined by moving the machining head, which directs the machining beam onto the workpiece, and the workpiece relative to each other along the corrected intended motion trajectory. In step a), the sequence of movements along the predefined desired movement trajectory is arbitrary, i.e. first of all at a first relative speed and then in time at a second relative speed, or vice versa.

In this aspect of the present invention, as in the first aspect of the present invention, a profile deviation that may be attributed to shaft vibration or the like when processing a workpiece is corrected by: before the machining operation, the workpiece is moved past and, if necessary, the predefined desired movement path is corrected. In contrast to the first aspect described above, however, the predefined desired movement path is traversed twice at different relative speeds: the first relative movement speed is relatively low, so that the predefined desired movement path is traversed slowly and with high accuracy. The second relative speed of movement corresponds substantially to the desired relative speed during the further processing. Depending on the deviation between the movements along the predefined desired movement path at two different relative speeds, the predefined desired movement path can be corrected, for example by calculating a correction counteracting the deviation into the desired movement path.

In one variant, the derivation of the deviation comprises: irradiating the workpiece surface with an illumination radiation in the region of the processing head, sensing the illumination radiation reflected on the workpiece surface in the region of the processing head in a spatially resolved manner in order to obtain a first reflection pattern of the overlapping surface area of the workpiece when moving along a predefined desired movement path at a first relative speed and a second reflection pattern of the overlapping surface area of the workpiece when moving along the predefined desired movement path at a second relative speed, and determining the deviation by comparing the first and second reflection patterns.

The deviation is determined on the basis of a comparison of the first and second reflection patterns, wherein the reflection patterns obtained during a first or second pass through a predefined desired movement path at two different relative speeds are compared with one another. The first reflection pattern obtained during the movement at the lower relative speed forms the reference or desired state, and the second reflection pattern obtained during the movement at the higher relative speed deviates from the first reflection pattern by a lateral offset. The comparison of the first and second reflection patterns for determining the deviation or lateral offset can be carried out analogously to the procedure described above, i.e. for example in the manner described in DE102006049627a1 or DE102005022095a1, typically by means of calculation of a similarity function.

In one variant, the surface region is illuminated and spatially resolved by processing optics of the processing head, in particular by focusing optics. In this case, the irradiation of the surface region is usually carried out coaxially or only slightly obliquely with respect to the machining beam directed onto the workpiece. Such illumination has proven to be advantageous because in this illumination mode the illumination radiation reflected from the surface region produces an irregular reflection pattern in the image on the detector, which reflection pattern facilitates a comparison between the images of the surface region sensed in a spatially resolved manner. Coaxial observation or sensing of the surface region, for example by means of imaging optics, has also proved advantageous for performing the comparison. In this case, the detector, for example a camera, is typically arranged coaxially with respect to the machining beam or to an extension of the beam axis of the machining beam.

In one variant, steps a) and b) are performed at least once more, wherein the corrected desired movement path determined in the preceding step c) forms the predetermined desired movement path for the performance of steps a) and b) again. In particular in the case of a corrected intended movement path which deviates significantly from the predefined intended movement path, it can be expedient to at least once again follow this movement path and to sense the relative movement or deviation between the machining head and the workpiece. In case the deviation or residual error between the actual motion trajectory and the due motion trajectory is still relatively large, step c) may be performed again to generate another corrected due motion trajectory. This process, i.e. the execution of steps a), b) and, if appropriate, c), can be carried out several times until the residual error or the actual-due deviation is sufficiently small.

Another aspect of the invention relates to a processing machine of the type mentioned at the beginning, which processing machine further comprises: a control device which is constructed or programmed/configured for moving the processing head and the workpiece relative to each other along a predetermined desired movement path before processing; an evaluation device which is designed or programmed/configured to determine a relative movement between the processing head and the workpiece by means of the optical detector during the movement along the desired movement path and to determine a corrected desired movement path as a function of the determined relative movement, wherein the control device is designed to move the processing head and the workpiece relative to one another along the corrected desired movement path during the processing. The processing machine may be, for example, a laser welder or a laser cutter.

In a further embodiment, the optical detector is designed for the spatially resolved sensing of the illumination radiation reflected at the workpiece surface in the region of the processing head in order to obtain temporally successive reflection patterns of overlapping surface regions of the workpiece during the movement along the predefined intended movement path, and the evaluation device is designed for determining the relative movement by comparing the temporally successive reflection patterns. As explained above in connection with the first aspect, the respective instantaneous relative movement between the processing head and the workpiece can be ascertained locally by calculating a similarity function or by finding an image of the maximum similarity of the reflection patterns of the overlapping surface areas.

Another aspect of the invention relates to a processing machine of the type mentioned at the beginning, which processing machine further comprises: a control device which is constructed or programmed/configured for moving the processing head and the workpiece relative to each other along a predetermined desired movement path at a first relative speed and at a second, greater relative speed before processing; an evaluation device which is designed or programmed/configured to determine a deviation between the movement along the predetermined desired movement path at the first relative speed and the movement at the second relative speed by means of the optical detector and to determine a corrected desired movement path as a function of the determined deviation, wherein the control device is designed to move the processing head and the workpiece relative to one another along the corrected desired movement path during the processing. As described above in connection with the corresponding method, the movement at the first relative speed along the predefined desired movement path takes place relatively slowly, so that an overshoot is avoided

Typically, the second relative speed corresponds to the intended speed of movement when subsequently processing the workpiece.

In one embodiment, the optical detector is designed for the spatially resolved sensing of the illumination radiation reflected at the workpiece surface in the region of the processing head, in order to obtain a first reflection pattern of the overlapping surface area of the workpiece when moving along a predefined desired movement path at a first relative speed and a second reflection pattern of the overlapping surface area of the workpiece when moving along a predefined desired movement path at a second relative speed; the evaluation device is designed to determine a deviation by comparing the first and second reflection patterns. In order to determine the deviation in the form of a lateral offset or difference, the respective first reflection pattern of the first surface region is compared with a second reflection pattern of a second surface region of the workpiece, which overlaps the first surface region, which second reflection pattern generally corresponds to the same position along a predefined desired movement path. As explained above, the corrected intended movement path can be determined in this way and deviations that may be attributed to shaft vibrations or the like can already be compensated for before machining.

In a further embodiment, the processing machine comprises an irradiation source for irradiating the workpiece surface with an irradiation radiation which is preferably coaxial with the processing beam. As explained above, it is advantageous for the sensing of the surface region to irradiate the surface region with the illuminating radiation. The processing optics, which are coaxial with the processing beam and therefore typically pass through the processing head, are advantageous but not absolutely necessary. For example, the irradiation can also be carried out by means of an irradiation source mounted on the outside of the processing head, wherein in this case the beam path of the irradiation radiation does not intersect the beam path of the processing beam in the processing head. If necessary, the illumination source for illuminating the surface can also be omitted, provided that sufficient illumination is present in the surroundings.

In a further embodiment, the processing machine is designed for illuminating the workpiece surface and for the spatially resolved sensing of the surface region through processing optics, in particular focusing optics, of the processing head. As explained above in connection with the method, the irradiation is preferably generally carried out coaxially or only slightly obliquely with respect to the machining beam directed onto the workpiece. Coaxial observation of the surface region, for example by means of imaging optics, has also proved advantageous. As explained above, the detector, which may be a high-resolution camera, for example, is typically also arranged coaxially with respect to the machining beam or with respect to an extension of the beam axis of the machining beam.

Drawings

Further advantages of the invention result from the description and the drawings. The features mentioned above and those yet further listed can likewise be used individually or in any combination of a plurality of them. The embodiments shown and described are not to be understood as being exhaustive in the end, but rather as having exemplary features for describing the invention.

The figures show:

figure 1 a laser processing machine for cutting a workpiece,

figures 2a, b are views of a laser machining head of the laser machining machine of figure 1,

FIG. 3 shows a schematic representation of a workpiece with a predetermined intended movement path of the machining head of FIGS. 2a and b,

FIG. 4a, b two diagrams of the reflection pattern of the illumination radiation reflected at two surface regions on the workpiece surface, captured by a detector, and

fig. 5a, b two diagrams, similar to fig. 4a, b, of a first and a second reflection pattern, which are obtained when walking through a predefined desired movement trajectory at two different relative speeds.

In the following description of the figures, the same reference numerals are used for identical or functionally identical components.

Detailed Description

Fig. 1 shows a laser processing machine 1 having a laser source 2, a laser processing head 4 and a workpiece carrier 5. The laser beam 6 generated by the laser source 2 is guided by means of a beam guide 3 by means of deflection mirrors (not shown) to the laser processing head 4 and focused therein, and is oriented perpendicularly to the surface 8a of the workpiece 8 by means of mirrors (also not shown), i.e. the beam axis (optical axis) of the laser beam 6 extends perpendicularly to the workpiece 8. In the example shown, the laser source 2 is CO₂A laser source. Alternatively, the laser beam 6 may be generated by a solid-state laser, for example.

For laser cutting of the workpiece 8, the workpiece 8 is first pierced by means of the laser beam 6, i.e. the workpiece 8 is melted or oxidized in a punctiform manner at the piercing point E and the melt formed there is blown off. Next, the laser beam 6 is moved over the workpiece 8, so that a common cutting contour 9 is formed, along which the laser beam 6 separates the workpiece 8.

Both the penetration and the laser cutting can be assisted by the addition of gas. Oxygen, nitrogen, compressed air and/or special purpose gases may be used as the cutting gas 10. The particles and gases formed can be sucked away from the suction chamber 12 by means of the suction device 11.

The laser processing machine 1 also comprises a movement device 13 for moving the laser processing head 4 and the workpiece 8 relative to each other. In the example shown, the workpiece 8 rests on the workpiece carrier 5 during machining and the laser machining head 4 moves along two axes X, Y of an XYZ coordinate system during machining. For this purpose, the movement device 13 has a gantry 14 which is movable in the X direction by means of a drive indicated by a double arrow. The laser processing head 4 can be moved by means of a further drive of the movement device 13, which drive is indicated by a double arrow, in the X direction in order to move it in the X direction or the Y direction to any desired processing head position B in a working field which is predetermined by the movability of the laser processing head 4 or by the workpiece 8. The laser beam 6 has a (momentary) feed speed v at the respective processing head position B.

As can be seen in fig. 2a, the laser beam 6 is focused onto the workpiece 8 by means of a focusing device in the form of a focusing lens 15 in order to perform a cutting process on the workpiece 8. In the example shown, the focusing lens 15 is a lens made of zinc selenide which focuses the laser beam 6 through the laser machining nozzle 16, more precisely through the nozzle opening 16a of the laser machining nozzle, onto the workpiece 8, in particular in the example shown onto a focal position F on the surface 8a of the workpiece 8. There, the laser beam 6 forms an interaction region 17 with the workpiece 8, after which a cutting contour 9 shown in fig. 1 is produced counter to the machining direction V or counter to the cutting direction of the laser cutting process. In the case where the laser beam 6 is derived from a solid-state laser, a focusing lens made of, for example, quartz glass may be used.

Also visible in fig. 2a is a semitransparent deflecting mirror 18, which reflects the incident laser beam 6 (for example, with a wavelength of approximately 10.6 μm) and transmits the observation radiation, which is important for process monitoring, to a further semitransparent deflecting mirror 19. In the example shown, the deflecting mirror 18 is translucent for observation radiation in the form of thermal radiation having a wavelength λ of approximately 700nm to 2000 nm. The illumination source 21 serves to illuminate the workpiece 8 coaxially with illumination radiation 22. The illuminating radiation 22 is transmitted by the other half-transmissive deflection mirror 19 and by the deflection mirror 18 and is deflected onto the workpiece 8 through the nozzle opening 16a of the laser machining nozzle 16.

Instead of the semitransparent deflection mirrors 18, 19, it is also possible to use a spatula mirror (scriperspegel) or a hole mirror (lochsiegel) which reflects only the incident radiation from the edge region in order to deliver the illuminating radiation 22 to the workpiece 8. It is also possible to use at least one mirror which is introduced laterally into the beam path of the laser beam 6 in order to be able to observe it.

A diode laser or LED or flash lamp may be provided as illumination source 21, which may be arranged coaxially with respect to the laser beam axis 24 as shown in fig. 2a, but may also be arranged coaxially. The radiation source 21 can also be arranged, for example, outside the laser processing head 4 (in particular next to the laser processing head) and aligned on the workpiece 8; alternatively, the irradiation source 21 may be arranged within the laser processing head 4, however not oriented coaxially with the laser beam 6 onto the workpiece 8. If necessary, the laser processing head 4 can also be operated without the radiation source 21.

A position-resolving detector in the form of a high-geometric-resolution camera 25 is arranged in the observation beam path 23 downstream of the further translucent deflection mirror 19. The camera 25 may be a high-speed camera which is arranged coaxially and thus independently of the direction with respect to the laser beam axis 24 or with respect to an extension of the laser beam axis 24. In the example shown, the camera 25 captures images in the near-infrared/infrared wavelength range by incident light irradiation, in order to capture a thermal image of the cutting process itself. In the example shown in fig. 2a, a filter can be arranged in front of the camera 25 when another radiation component or wavelength component is to be excluded from the sensing by means of the camera 25. The filter can be configured, for example, as a narrow-band bandpass filter having a half-value width of, for example, about 15nm, which filter transmits wavelengths λ in the range of about 800 nm.

In order to sense the surface region O, O' of the workpiece 8 shown in fig. 4a, b with a local resolution on the detector surface 25a of the camera 25, the laser processing head 4 has imaging optics 27. In the example shown, the imaging optics 27 have a diaphragm 28 which is mounted so as to be rotatable about a central axis of rotation D, so that the position of the eccentrically arranged diaphragm aperture 28a moves on an arc of a circle about the axis of rotation D when rotated (see fig. 2 b).

By arranging the diaphragm 28 in the beam path of the imaging optics 27 focused by means of the lens 29, only a part of the observation beam path 23, which passes through the diaphragm opening 28a arranged eccentrically with respect to the extension of the beam axis 24 of the laser beam 6 and forms the observation beam 23a imaged on the detector surface 25a, passes through the edge region of the focusing lens 15 and is oriented at an angle β in the converging beam path behind the focusing lens 15 with respect to the beam axis 24 of the laser beam 6, in the example shown in fig. 2 the observation direction R1 of the observation beam 23a extends in projection in the XY plane or workpiece plane parallel to the direction of the machining vector V along which the laser beam 6 and the workpiece 8 are moved relative to one another in the X-Y plane in order to form the desired cutting profile, i.e. to carry out a penetration observation (stechende beabachtung) — in the example shown, the angle β (observation direction R1 is oriented at this angle with respect to the beam axis 24 of the laser beam 6) lies between about 1 ° and about 5 °, for example about 4 °.

Instead of a mechanically adjustable aperture 28, an electrically adjustable aperture, for example in the form of an LCD array, can also be used, in which individual pixels or groups of pixels are switched on or off electronically in order to produce an aperture effect. Unlike what is shown in fig. 2a, b, the mechanical diaphragm 28 can also be moved or displaced transversely to the observation beam path 23, for example in the YZ plane, in order to mask different parts of the observation beam path 23 or to open these parts for observation. The aperture 28 may also be implemented as one or more mechanical elements that may be opened and closed. In contrast to the illustration in fig. 2a, b, the diaphragm 28 can also be omitted completely, i.e. the machining beam path 23 is imaged completely onto the detector surface 25 a.

Fig. 3 shows a workpiece 8 to be machined, more precisely a workpiece surface 8a, having a predefined intended movement path 9' along which the workpiece 8 is to be cut in order to produce the intended cutting contour 9 shown in fig. 1. The predefined intended movement path 9' extends from the insertion position E explained above to the end position T and has a semicircular path section, to which a straight path section adjoins. Due to the axial vibrations of the machining head 4, more precisely of the drive shaft of the movement device 13, the actual cutting contour (not shown) generated during the movement along the predefined movement path 9' of the machining head 4 does not exactly correspond to the (due) cutting contour 9 shown in fig. 1 that is to be generated on the workpiece 8 during the cutting operation.

In order to correct contour deviations due to vibrations, the following steps are carried out before machining: in step a), the laser processing head 4 is moved along a predetermined desired movement path 9 'over the stationary workpiece 8, i.e. the laser processing head 4 is guided along the desired movement path 9' between the penetration position E and the end position T. The movement of the laser machining head 4 is controlled by means of a control device 34 (see fig. 1), which also assumes the other control tasks of the laser cutting machine 1 and is connected to the evaluation device 30 in terms of signals.

By means of an evaluation device 30 connected to the detector 25 in terms of signals, the relative movement 31 between the laser processing head 4 and the workpiece 8 is determined in step b) using the optical detector 25, as described in more detail below. Based on the determined relative movement 31 between the laser processing head 4 and the workpiece 8, in step c) a corrected target movement path 9 is determined in the evaluation device 30, the control device 34 or other devices, which is also shown in fig. 3. The corrected due motion trajectory 9 compensates for a trajectory error due to the vibration of the drive axis of the laser processing head 4 described earlier. If the laser processing head 4 is moved along the corrected desired movement path 9 shown in fig. 3, a desired cutting contour 9 shown in fig. 1 is produced during the subsequent processing when cutting the workpiece 8, which cutting contour corresponds to the predetermined desired movement path 9' (irrespective of deviations or overshoots).

In order to determine the relative movement 31 or the actual movement path when the laser processing head 4 is moved along the intended movement path 9', the irradiation radiation 22 of the radiation source 21 irradiates the surface 8a of the workpiece 8 through the nozzle opening 16a of the processing nozzle 16. The surface area O sensed in the area of the machining head 4 or at the respective machining head position B along the predefined desired movement path 9' on the surface 8a of the workpiece 8 through the nozzle opening 16a is imaged by means of the imaging optics 27 onto the detector surface 25a of the position-resolving detector 25.

Fig. 4a shows the illuminating radiation 22 reflected on the surface area O shown in fig. 3, more precisely the reflection pattern 32 of the surface 8a of the workpiece 8 in the surface area O at the processing head position B shown in fig. 3. Fig. 4B shows a reflection pattern 32 ' or image of the surface region O ', which is recorded at a later point in time than the reflection pattern 32 shown in fig. 4a at a further processing head position B '. The time offset between the recording of the two images of the surface region O, O ' or of the associated reflection pattern 32, 32 ' is selected in such a way that the two surface regions O, O ' (in part) overlap, as is shown in fig. 4 b.

From a comparison between the temporally successive reflection patterns 32, 32 ' of the two surface regions O, O ', a lateral offset between the relative movement 31, more precisely the two surface regions O, O ', can be determined. The lateral offset 31 corresponds to the direction and magnitude of the feed speed v of the processing head 4 at the processing head position B of the surface area O shown in fig. 3. As can be seen in fig. 4b, the transverse offset 31 does not have to extend horizontally or in the negative Y-axis direction, as is the case with the predefined desired trajectory profile 9 'shown in fig. 3 in the straight trajectory section, but rather the direction of the transverse offset 31 deviates from the predefined desired movement trajectory 9', in particular in the X direction by a deviation 33 shown in fig. 4 b.

When the laser processing head 4 is moved along the predefined movement path 9' shown in fig. 3, a deviation 33 of the actual movement path can be determined at each processing head position B by: the analysis evaluates the reflection patterns 32, 32 'of the respectively overlapping surface regions O, O' which follow one another in time. In this way, the corrected intended machining path 9 shown in fig. 3 can be determined in the evaluation device 30, the control device 34 or another device of the laser processing machine 1 or a device connected to the laser processing machine in terms of signals. In the corrected intended machining path 9, the deviation 33 is compensated for by a change of the predefined intended machining path 9' in such a way that the desired straight-line path section of the cutting contour 9 shown in fig. 1 results.

Instead of determining the deviation 33 from the relative movement 31, the deviation 33 can also be determined as described below with reference to fig. 5a and b. The following steps are carried out before the machining: in a first step a), the laser processing head 4 is moved along a predefined desired movement path 9 'shown in fig. 3 over the stationary workpiece 8, i.e. the laser processing head 4 is guided along the predefined desired movement path 9' between the penetration position E and the end position T. A (first) movement along a predetermined desired movement path 9' at a first relative or feed speed v₁The speed is so low that practically no deviations from the predefined desired movement path 9 'due to vibrations occur, i.e. the laser processing head 4 is actually moved exactly along the predefined desired movement path 9'.

During the movement, the illuminating radiation 22 reflected on the surface 8a of the workpiece 8 in the region of the machining head 4 is sensed in a spatially resolved manner, as described above in connection with fig. 4a, b. Fig. 5 shows the reflected illuminating radiation 22, more precisely the reflection pattern 32a of the surface 8a of the workpiece 8 in the surface region O, sensed in a spatially resolved manner for the surface region O at the processing head position B shown in fig. 3.

Subsequently, in step a), the laser processing head 4 is moved again along the predefined desired movement path 9 'over the stationary workpiece 8, i.e. the laser processing head 4 is moved again along the predefined desired movement path 9' between the penetration position E and the end position T at a second, higher relative speed or feed speed v₂Is guided. The second relative velocity v is set here₂Corresponding to the desired relative speed during the subsequent machining of the workpiece 8. In a second movement along the predefined desired trajectory 9', the illuminating radiation 22 reflected at the surface 8a of the workpiece 8 is also subjected to a spatially resolved sensing. Fig. 5B shows a reflection pattern 32B or image of the surface region O 'which is recorded in a second movement at a processing head position B' which corresponds to the position shown in fig. 3 along a predetermined pathBut is offset laterally (in the X direction) relative to the processing head position B due to axial vibrations, due to the processing head position B of the intended motion trajectory 9'.

In a second step b), the difference or deviation 33 between the machining head positions B, B 'is determined by a comparison between the first and

second reflection patterns

32a, 32b of the two mutually overlapping surface regions O, O' by means of an evaluation device 30 connected to the detector 25 in terms of signals. As can be seen by a comparison between fig. 4b and fig. 5b, in the method described in conjunction with fig. 5a, b, the same amount of deviation 33 is determined as in the method described above. In the following step c), a correction of the predefined desired movement path 9 'or a compensation of the path errors takes place in the manner described above, i.e. by determining and correcting the deviations 33 at each machining head position B along the predefined desired machining path 9'.

The steps a) and b) described above can be repeated as necessary to check whether the desired cutting contour 9 is produced on the workpiece 8 when the laser processing head 4 is moved along the corrected desired processing path 9, i.e. whether the predefined desired movement path 9' is reproduced as accurately as possible on the workpiece 8 when the processing head 4 is moved along the corrected desired movement path 9. If this is not the case, step c) can be executed again if necessary, i.e. a further corrected desired movement path 9 can be determined and steps a) and b) can be executed again in order to check whether the deviation 33 of the corrected desired movement path 9' from the actual movement path is sufficiently small. If necessary, steps a), b) and c) can be carried out successively a plurality of times until the deviation 33 along the entire corrected movement path 9 falls below a predetermined value or until a pause criterion is reached, for example a predetermined number of repetitions.

To compare the reflective patterns 32, 32'; 32a, 32b for determining the relative movement 31 or the deviation 33, a pattern recognition algorithm is implemented in the evaluation device 30, which calculates two reflection patterns 32, 32'; 32a, 32b, from which the reflection patterns 32, 32 'in the overlapping surface area O, O' are determined; 32a, 32b, the image part having the greatest similarity. For details of examples of such pattern recognition algorithms reference may be made to DE102005022095a1 or DE102006049627a1, cited at the outset.

In summary, in the manner described above, the cutting contour 9 to be produced during the cutting process can be reproduced with high accuracy without the need for a reduction in the dynamics, i.e. the processing speed, during the cutting process. The method described above can also be carried out in other processes, for example during the welding of workpieces 8, in order to specify a corrected movement path 9 to be provided for producing a weld seam or weld contour to be formed with as high an accuracy as possible.

Claims

1. A method for machining a workpiece (8) by means of a machining beam (6), the method comprising:

before processing:

a) moving the machining head (4) and the workpiece (8) relative to each other along a predetermined desired movement path (9'),

b) the relative movement (31) between the machining head (4) and the workpiece (8) during the movement along the predefined desired movement path (9') is determined by means of an optical detector (25) which is fixedly connected to the machining head (4), and

c) determining a corrected desired movement trajectory (9) from the determined relative movement (31),

the method further comprises:

the workpiece (8) is machined by moving the machining head (4) which directs the machining beam (6) onto the workpiece (8) and the workpiece (8) relative to each other along the corrected intended movement trajectory (9).

2. The method according to claim 1, in which the determination of the relative movement comprises:

irradiating the surface (8a) of the workpiece (8) with an irradiation radiation (22) in the region of the processing head (4),

spatially resolved sensing of the illuminating radiation (22) reflected on the surface (8a) of the workpiece (8) in the region of the machining head (4) in order to obtain temporally successive reflection patterns (32, 32 ') of overlapping surface regions (O, O ') of the workpiece (8) during the movement along the predefined desired movement path (9 '), and

the relative movement (31) is determined by comparing the reflection patterns (32, 32') which are successive in time.

3. A method for machining a workpiece (8) by means of a machining beam (6), the method comprising:

before processing:

a) the machining head (4) and the workpiece (8) are moved relative to each other along a predetermined desired movement path (9') at a first relative speed (v)₁) The movement is carried out, and the movement is carried out,

the machining head (4) and the workpiece (8) are moved relative to each other along the predefined desired movement path (9') at a second, greater relative speed (v)₂) The movement is carried out, and the movement is carried out,

b) determining the first relative movement speed (v) along the predefined desired movement path (9') by means of an optical detector (25) which is fixedly connected to the machining head (4)₁) The movement is carried out with the second relative movement speed (v) along the predetermined desired movement path (9₂) A deviation (33) between the movements performed, and

c) a corrected due movement locus (9) is obtained from the deviation (33),

the method further comprises:

4. A method according to claim 3, in which the derivation of the deviation (33) comprises:

spatially resolved sensing of illumination radiation reflected on the surface (8a) of the workpiece (8) in the region of the machining head (4)Is fired (22) so as to follow said predetermined desired movement trajectory (9') at said first relative speed (v₁) While moving, a first reflection pattern (32a) of an overlapping surface region (O, O ') of the workpiece (8) is obtained and the workpiece is moved along the predefined desired movement path (9') with the second relative speed (v)₂) Obtaining a second reflection pattern (32b) of an overlapping surface area (O, O') of the workpiece (8) while in motion, and

the deviation (33) is found by comparing the first and second reflective patterns (32a, 32 b).

5. Method according to claim 2 or 4, in which method the illumination and the locally resolved sensing of the surface area (O, O') is carried out through processing optics, in particular focusing optics (15), of the processing head (4).

6. Method according to one of the preceding claims, in which method the steps a) and b) are carried out at least once more, wherein the corrected due movement trajectory (9) determined in the preceding step c) constitutes the predefined due movement trajectory (9') when the steps a) and b) are carried out again.

7. A processing machine, in particular a laser processing machine (1), for processing a workpiece (8), the processing machine comprising:

a machining head (4) for machining the workpiece (8), which is designed to direct a machining beam (6) onto the workpiece (8),

a movement device (13) for moving the machining head (4) and the workpiece (8) relative to one another, and

an optical detector (25) which is fixedly connected with the processing head (4),

it is characterized by comprising:

a control device (34) which is designed to move the machining head (4) and the workpiece (8) relative to one another along a predefined desired movement path (9') before machining,

an evaluation device (30) which is designed to determine a relative movement (31) between the machining head (4) and the workpiece (8) during the movement along the predefined desired movement path (9') by means of the optical detector (25) and to determine a corrected desired movement path (9) as a function of the determined relative movement (31), and wherein the control device (34) is designed to move the machining head (4) and the workpiece (8) relative to one another along the corrected desired movement path (9) during the machining.

8. Processing machine according to claim 7, wherein the optical detector (25) is designed for the spatially resolved sensing of the illumination radiation (22) reflected at the surface (8a) of the workpiece (8) in the region of the processing head (4) in order to obtain temporally successive reflection patterns (32, 32 ') of overlapping surface regions (O, O') of the workpiece (4) during the movement along the predefined desired movement path (9 '), and wherein the evaluation device (30) is designed for determining the relative movement (31) by comparing the temporally successive reflection patterns (32, 32').

9. Processing machine according to the preamble of claim 7, characterized by:

a control device (34) which is designed to bring the machining head (4) and the workpiece (8) relative to one another at a first relative speed (v) before machining₁) And at a second, greater relative velocity (v)₂) Moving along a predetermined desired movement path (9'),

an evaluation device (30) which is designed to determine a deviation (33) between the movement along the predefined desired movement path (9 ') at the first relative speed (v1) and the movement along the predefined desired movement path (9') at the second relative speed (v2) by means of the optical detector (25), and to determine a corrected desired movement path (9) from the determined deviation (33), and wherein,

the control device (34) is designed to move the machining head (4) and the workpiece (8) relative to one another during machining along the corrected intended movement path (9).

10. Processing machine according to claim 9, wherein the optical detector (25) is designed for the spatially resolved sensing of the illuminating radiation (22) reflected on the surface (8a) of the workpiece (8) in the region of the processing head (4) in order to determine the first relative velocity (v) along the predefined desired movement path (9') at the first relative velocity (v ″)₁) While moving, a first reflection pattern (32a) of an overlapping surface region (O, O ') of the workpiece (8) is obtained and the workpiece is moved along the predefined desired movement path (9') with the second relative speed (v)₂) Obtaining a second reflection pattern (32b) of an overlapping surface area (O, O') of the workpiece (8) while in motion,

and in the processing machine, the evaluation device (30) is designed to determine the deviation (33) by comparing the first and second reflection patterns (32a, 32 b).

11. The converting machine according to any one of claims 7 to 10, further comprising: an illumination source (21) for illuminating a surface (8a) of the workpiece (8) with illumination radiation (22).

12. Processing machine according to one of claims 8 or 10, which is designed for illuminating the surface (8a) of the workpiece (8) and for the spatially resolved sensing of the surface region (O, O') by means of processing optics, in particular focusing optics (15), of the processing head (4).