Laser processing method and laser processing tool

Abstract

The present invention relates to a laser processing method, a laser processing tool, and a computer program product. It is an object of the present invention to provide a laser processing tool, a laser processing method, and a computer program product, which reduce defects. For this purpose, - At least one working area K AB Or one work point K AP defining at least one threshold value S0 for a first light intensity dependent process variable F; - Working range K AB Within or working point K AP detecting a second process variable K during operation of the laser processing tool (1), the second process variable K being independent of light intensity; - At least one working range K under changed process conditions AB Within or working point K AP determining a change in a first process variable F; - value F0 to value F of the first process variable F 0R In response to the change to , at least one threshold S0 is changed to threshold S 0R and changing the laser beam into

Description

[Technical field]

[0001] The present invention relates to a laser processing method, a laser processing tool and a computer program product according to the preambles of the independent claims.

[0002] The technical field of industrial processing of various materials using laser radiation is becoming more and more important. For example, when cutting workpieces made of different materials, laser radiation from high-power laser processing tools or laser cutting machines in the range of several kilowatts is usually used. To monitor the laser processing process, the laser processing tool is assigned a sensor device that measures various measurement variables that are evaluated in a control device. An example of a sensor device is a camera, with which the light intensity is detected as a spatially resolved measurement variable for the workpiece to be processed. From the light intensity, various conclusions can be drawn about the quality of the processing. These conclusions can be used to monitor the laser processing tool and as a control function for the laser processing tool. For example, it can be used to detect cut breaks during laser cutting. Cut breaks are cuts in which, undesirably, a complete cut is not made over the entire width of the workpiece. Changes in process conditions can cause malfunctions in previously calibrated and functioning sensor devices. These changes in process conditions can have various causes. Firstly, there are malfunctions or deviations of the laser processing tool, such as a dirty protective glass, heating of the lens system or a change in the purity of the gas jet. These defects or deviations affect the laser processing process or the detection by the sensor device. Secondly, deviations in the material to be processed, such as the sheet thickness, surface finish, material composition or material inclusions of the workpiece. These deviations can affect the laser processing process and the process control. Thirdly, deviations in the selected process control, such as changing the focal position, changing the focal diameter, changing the distance from the workpiece to the nozzle at the exit of the laser beam, or changing the gas pressure. This means that existing miscuts are not detected or non-existent miscuts are falsely detected. One remedy in the prior art is a further calibration process of the laser processing tool with the sensor device, which is usually performed in a separate operating step, i.e. outside machine operating hours. Recalibration is necessary, for example, regarding the transmission of the process radiation through the optical elements and sensor device used, or due to a decrease in the sensitivity of the sensor.

[0003] Object of the invention It is an object of the present invention to provide a laser processing tool and method, and a computer program product, whereby defects are reduced.

[0004] Summary of the Invention For this purpose, the laser processing method comprises the following method steps: At least one working area K AB Within or working point K AP - a method step of defining at least one threshold value S0 for a light intensity dependent variable F0 in At least one working area K AB Within or working point K AP detecting a second process variable K during operation of the laser processing tool (1), the second process variable K being independent of light intensity; When changing process conditions, the working area K AB Within or working point K AP determining a change in a first process variable F0; First process variable F OR In response to the change in 0R How to change steps.

[0005] Additionally, a computer program product is provided within the evaluation device for executing the laser processing method.

[0006] Further, a laser processing tool is provided having an evaluation device, the evaluation device being adapted to evaluate at least one working range K AB Within or working point K AP At least one threshold value S0 for a light intensity-dependent first process variable F in a working range K AB Within or working point K AP A second process variable K is defined that is independent of the light intensity during operation of the laser processing tool, and the second process variable K is changed under the changed process conditions to obtain at least one working range K. AB Within or working point K APand detecting a change in a first process variable F at the time of the first process variable F being changed from a value F0 to a value F1. 0R In response to the change to at least one threshold value S0, 0R It is designed to be changed to.

[0007] Embodiments of the invention are set forth in the dependent claims.

[0008] In one example, a control setpoint R of a laser processing process is assigned to a threshold value S0, and the control setpoint R varies from a value F0 to a value F1 of a first process variable F. 0R In response to the change to the control setpoint R OR When the first process variable F changes, the control set point is changed.

[0009] In one example, in the control method step, the second process variable K is the trailing length or tilt angle of the cutting surface of the workpiece to be cut. The trailing length is the length in the feed direction from the top cutting surface of the workpiece to the bottom cutting surface. The tilt angle of the cutting surface can be measured from the top to the bottom of the workpiece. These process variables K have been found to be particularly suitable for functionality, since they can be detected independently of the light intensity (hereinafter also intensity-independent).

[0010] In another example, the threshold value S0 is set to the threshold value S 0R The method step of changing the working point K in response to a first process variable F, the light intensity recorded for the workpiece, or a process variable that depends on the light intensity, is performed. AP In or work area K AB It is executed within

[0011] Changed threshold S OR Based on this, a failure of the laser processing tool can be determined or a controlled variable that is less dependent on monitoring or changing the light intensity can be stabilized. The failure due to the changed threshold can be advantageously S OR which is the threshold S OReflecting the actual condition of the laser processing tool under modified conditions that are better than In the context of this disclosure, the term fault also refers to faulty or undesirable processing processes and processing errors.

[0012] In one example, the disconnection interruption occurs when the modified threshold S OR Based on the changed threshold S O is to reliably detect the cut interruption and prevent inaccurate detection of the cut interruption or an unchanged threshold S O This helps to prevent a disconnection interruption from going undetected: in the first case, there is no fault, but one is falsely detected, or in the second case, there is a fault, but it is not detected.

[0013] Advantageously, the defect of the laser processing tool is determined by a threshold S in response to the modified first variable F. O Let S be the threshold value. OR It has been found that the .lambda. can be effectively reduced by proportionally changing the .lambda.

[0014] Furthermore, the threshold S OR is continuously changed in the control process of the laser processing method. Thus, the threshold value S for the light intensity-dependent first process variable F is OR is adjusted from the perspective of control technology.

[0015] In another example, the control process or control is performed using a second process variable K as the controlled variable, whereby the adjustable variable is the feed rate of a workpiece in a laser processing tool or the power supply of the laser processing tool. Thus, the controlled variable, the second process variable K, is set by adjusting the designated adjustable variable.

[0016] In one example, the threshold S O is continuously or iteratively changed or adjusted. OIt is ensured that the threshold value S always corresponds to the current conditions of the laser processing tool. By this measure, a particularly high level of process stability can be achieved. The first process variable F is detected as a function of the position and / or the orientation. O can be adjusted accordingly depending on the position and / or orientation, which allows anisotropy or inhomogeneity of the laser processing tool to be taken into account and compensated for within its working range. Alternatively or additionally, the first process variable F is detected in a time-dependent manner and a threshold value S O can be adjusted over time. O When adjusting S, it can also take into account how long ago or how far back information about the cut location or cut direction was available. If a cut was made in the same direction just a few seconds ago, it is likely that the laser processing tool is still in a similar state, but a cut a minute or more later is likely that the laser processing tool is no longer in the same state. Thus, the threshold S O can also be a function of the progression of available information over time. O When adjusting, time-series aspects may be taken into account.

[0017] In the following, examples of the invention are explained in detail with reference to the drawings. [Brief description of the drawings]

[0018] [Figure 1] 1 shows a schematic representation of an apparatus as part of a laser processing tool for monitoring a laser processing method, specifically a laser cutting process, by recording an image of an area of ​​a workpiece to be monitored, including an interaction area. [Diagram 2] 2 shows a schematic representation of a laser processing tool with further devices for monitoring the laser processing process, in particular the laser cutting process. [Diagram 3] 1 shows a qualitative diagram with a first process variable F on the y-axis and a threshold value S of a second process variable K on the x-axis, a characteristic curve with a working range and a working point, and a miscut area of ​​the laser processing tool in operation.

[0019] 1 shows an exemplary structure of an apparatus 14 for process monitoring and process control of a laser processing method, in particular a laser cutting process, on a workpiece 8 by a laser processing tool 1, where only the laser processing head 4 of the apparatus 14 is shown very diagrammatically, with a focusing lens 15 for focusing the laser beam 6 of the laser processing tool 1, a cutting gas nozzle 16 and a deflection mirror 17. Further components may also be included in the laser processing head 4. In the present case, the deflection mirror 17 has a partially transparent design and forms an inlet-side component of the process monitoring device 14. The laser beam 6 has a high power for processing the workpiece 8, in particular for cutting or separating the workpiece 8.

[0020] The deflecting mirror 17 reflects the incident laser beam 6, which for example has a wavelength of approximately 10 μm or 1 μm if a solid-state laser is used, and transmits process radiation 19, which is radiation reflected from the workpiece 8 and emitted from an interaction area 18 of the laser beam 6 with the workpiece 8, relevant for process monitoring, which in this example is in the wavelength range of approximately 300 nm to 2000 nm. As an alternative to a partially transparent deflecting mirror 17, a scraper or aperture mirror can also be used to feed the process radiation 19 to the camera 21.

[0021] In the device 14, another deflection mirror 20 is arranged downstream of the partially transparent mirror 17 in the direction of the process radiation 19 and deflects the process radiation 19 towards a geometrically high-resolution camera 21 as an image capture unit. The camera 21 can be a high-speed camera arranged coaxially with respect to the laser beam axis 22 or to an extension of the laser beam axis 22a and thus arranged in an orientation-independent manner. In principle, the camera 21 can also record images using the reflected light method from about 300 nm to 2000 nm, provided that an additional illumination source is provided in this wavelength range, and alternatively, it is also possible to record self-illumination or process radiation 19 in the UV and NIR / IR wavelength ranges. The camera 21 may also be provided only as an image detection unit, so that no additional scanning beams are necessary. In both cases, the camera 21 detects the process radiation 19 or the process light from the interaction area 18.

[0022] In this example, imaging, focusing optics 23 are provided between the partially transmitting mirror 17 and the camera 21, which is shown in Figure 1 as a lens, to focus the radiation relevant for process monitoring or the process radiation 19 onto the camera 21. In the example shown in Figure 1, a filter 24 in front of the camera 21 in the direction of the process radiation 19 is advantageous if further radiation or wavelength components are to be excluded from detection by the camera 21. The filter 24 may, for example, be in the form of a narrow bandpass filter.

[0023] In this example, the camera 21 is optionally operated using a reflected light method, i.e. an additional illumination source 25 is provided above the workpiece 8, which couples illumination radiation 27, which is coaxial with the laser beam axis 22, into the light path via another partially transparent mirror 26. In principle, however, the intensity of the process radiation 19 generated during laser processing is sufficient. The respective beam paths are vertically coaxial, as shown in FIG. 1. A laser diode or a diode laser can be provided as the additional illumination source 25, which can be arranged coaxially, as shown in FIG. 1, or off-axis with respect to the laser beam axis 22. The additional illumination source 25 can also be arranged, for example, outside the laser processing head 4, in particular adjacent to the laser processing head 4, and directed onto the surface 8a of the workpiece 8. Alternatively, the illumination source 25 can be arranged in the laser processing head 4. It will be understood that the device 14 can also be operated without the additional illumination source 25.

[0024] In the example shown in Figure 1, during a laser fusion cutting or laser flame cutting process, camera 21 takes an image B of a monitored area 28 of workpiece 8, including interaction area 18. During the cutting process with laser beam 6, relative movement occurs between workpiece 8 and laser processing head 4 by movement of laser processing head 4 along the positive Y direction (see arrow) with a relative speed shown as feed rate V. Laser processing head 4 also moves in two planes in the x and z directions. During the cutting process, a cut surface 29 is formed in the run-up to interaction area 18, followed by a kerf 9 in the workpiece 8 in the negative Y direction.

[0025] The image acquisition unit, designed as a camera 21, is connected in signal technology with an evaluation device 30. The evaluation device 30 is configured and programmed to recognize at least one disturbance in the processing process, such as a section interruption, on the basis of the evaluation of the recorded images B of the area 28 or a chronological sequence of images B. The camera 21 and the evaluation device 30 form a sensor device.

[0026] The evaluation device 30 evaluates an image B or a series of images B from the interaction area 18, recorded in sequence, to extract or identify features of the interaction area 18 that are indicative of disturbances in the cutting process.

[0027] As can be seen from FIG. 1, the evaluation device 30 is in signal connection with an open-loop or closed-loop control device 31, by which the laser cutting and laser machining processes are controlled in an open-loop or closed-loop manner.

[0028] FIG. 2 shows a very schematic side view of a laser processing tool 1. As in FIG. 1, a camera 21 and a connected evaluation device 30 are included to monitor the laser processing method, in particular the laser cutting process. Here, the laser processing tool 1 is a laser cutting system. A workpiece 8, here a sheet metal, is placed on a workpiece support 5 of the laser processing tool 1. The laser processing tool 1 has a laser processing head 4, which is a cutting head. The laser processing head 4 can move along a first translation axis 32, a second translation axis 33 and along an axis in the image plane relative to the workpiece support 5. Furthermore, the laser processing head 4 can be rotatable about one or more rotation axes in a manner not shown in detail.

[0029] For processing, e.g. cutting, the workpiece 8, the laser processing head 4 or cutting head emits a laser beam 6. By means of the laser beam 6, the workpiece 8 is cut along a trajectory. To support processing of the workpiece 8 with the laser beam 6, the laser processing head 4 has a cutting gas nozzle 16. Cutting gas is supplied to the workpiece 8 via the cutting gas nozzle 16. The laser processing head 4 may further comprise a protective glass 34 for a lens system, which is not shown in detail in FIG. 2.

[0030] The laser processing tool 1 comprises an evaluation device 30 similar to that of Fig. 1, and further a control device 31 may be connected to the evaluation device 30 in terms of signal technology. The evaluation device 30 and the associated control device 31 perform the cutting process by determining and adjusting various process parameters or variables F, K. Two of the process parameters are for example the feed rate v and the focal position, i.e. the position of the focal point of the laser beam 6 relative to the workpiece 8. Further process parameters or variables may be the laser power, the focal diameter, the gas pressure of the cutting gas before leaving the cutting gas nozzle 16, the mass flow rate of the cutting gas through the cutting gas nozzle 16 and / or the distance of the cutting gas nozzle 16 from the workpiece 8.

[0031] FIG. 3 shows a qualitative diagram to explain an example of the invention. Under normal processing conditions, a miscut can be easily distinguished from a good cut using light intensity-dependent, or intensity-dependent, process variables. The process variables depend on the degree of change in light intensity detected by the camera 21 and sensor device used. For example, the gray value of a camera pixel is proportional to the light intensity, while the geometric variables in the camera image are independent of the light intensity. Nevertheless, the geometric variables may also be correlated with the light intensity, for example if a threshold value is used for the gray value of the camera image.

[0032] Under faulty or difficult processing conditions, the intensity-dependent variable alone can no longer reliably determine the fault or fault in the processing process. Difficult processing conditions can arise, for example, when there is a fault in the light intensity of the scanning beam or the process radiation 19. Therefore, a second variable is introduced that is independent of the light intensity or is less dependent on the light intensity. With the help of the second variable or process variable, faults or faults in the processing process are detected, thus reducing the sensitivity of the laser processing process to faults.

[0033] A second intensity-independent or substantially intensity-independent variable K is shown on the x-axis approximately at the trailing length and indicates the distance in the feed direction from the top cutting surface 29 to the bottom cutting surface 29 of the workpiece 8. Another intensity-independent process variable K is the inclination angle of the cutting surface 29, which is the angle between the top and bottom of the workpiece 8 at the cutting surface. These process variables K have been found to be particularly suitable for functionality. On the y-axis is the thresholds S0 and S1 due to the first process variable F, in this example the miscut variable F. oR After exceeding the threshold values ​​S0 and S1, a disconnection interruption is detected in the evaluation device 30. oR is the intensity miscut variable F with the thresholds S0 or S oR That is, F 依存の0 or F oR If S0 or S1, then there is a good cut. oR Exceeds, i.e., F>S0 or F>S oR If the threshold is not changed, then in fault-free operation, the unupdated threshold satisfies condition F O is applied and the threshold is changed, in the bad behavior, the updated threshold has F>S oR Optionally, the above conditions can be used to detect whether the cut is good or bad if they are met for a certain period of time. oR Each of the updated thresholds S oR is a function of the set threshold value S0, the first process variable F (here, the miscut variable F), and the process variable K, and S oR =f(F,K,S O ) In particular, the work point K AP In or work area K AB The second process variable K in AP If the threshold S0 is near the threshold S oR Some work scopes are changed to K AB can also be determined. AB Or multiple work ranges K AB ​​​3 , can range anywhere, i.e., from the minimum measurable process variable K to the hatched miscut region along the x-axis of FIG. 3 , indicated by the second process variable K. The controller or regulator 31 can, for example, execute a process stop of the laser processing tool 1 when a miscut is detected.

[0034] For example, the control device 31 may be configured to detect a work point K AP The controller 31 can then steer the machining process back to the defined working point by controlling the process parameters or parameter variables. AP is led to.

[0035] The diagram also shows two characteristic curves of the laser processing tool 1 in operation, which show the progression of the first process variable F or the miscut variable F in relation to the second process variable K, the dashed curve showing the laser processing without any faults or defects and the solid curve showing the laser processing with faults or defects, as described below. AP and the region along the process variable K is the working point K AP , working range K AB The measurement range of the laser processing tool 1 and the laser processing process is registered around the working point K AP In or work area K AB At the work point K AP In the laser processing process, the second process variable in the fault-free process according to FIG. AB In particular, the defined work point K AP K during operation of the laser processing tool 1 in controlled operation of the process variable K at the work point K AP defines this as K = K AP is applicable and / or the working scope K AB For the process variable K, the operating point K AP The region around the failure-free miscut variable F on the dashed characteristic curve. Oindicates a fault-free operation of the laser processing tool 1, where the evaluation device 30 detects no faults. AP In FIG. 3, a threshold value S0 indicating a fault of the laser processing tool 1, a threshold value of the miscut variable without fault, is shown as F-threshold S0 without fault. The threshold value S0 is determined before operation of the laser processing tool 1, or alternatively during operation. If the miscut variable F exceeds the threshold value S0 during laser processing, a fault is detected and a cut interruption is recognized. Optionally, a cut interruption is detected when the threshold value S0 is exceeded for a certain period of time. A fault can be reliably detected without process changes to the laser processing tool 1.

[0036] If a process change occurs during operation of the laser processing tool 1, for example due to a contamination of the focusing lens 15, the first process variable F or the miscut variable F changes, which is recognized by the evaluation device 30. The process change or disturbance leads to a shift of the characteristic curve of FIG. 3. For example, the light intensity of the first process variable F, the miscut variable F, changes when the laser beam 6 is disturbed by a contamination, as a result of which the camera 21 detects more process light or process radiation 19 due to scattered radiation. AB , especially the work point K AB The first process variable F OR This would lead to the disconnection being detected inaccurately. This altered first process variable is the perturbed F value F in Figure 3. OR , i.e., a faulty miscut variable. This false positive is denoted F OR >S O 3 as F = K. The process change leads to a shift of the first variable F relative to the second process variable K. The characteristic curve as a functional relationship between the first process variable F and the second process variable K shifts. In FIG. 3, the faulty miscut variable F is shown as a solid characteristic curve. Without further measurements, in FIG. 3, the faulty miscut variable F OR is the working range K AB Within, and in particular above, the threshold S0, the working point K AP That is, F 0RIf >S0, a cut interruption was erroneously detected. To correct this, the working range K AB In particular, the work point K AP The first process variable F OR is determined, which has a deviation from the fault-free detected value for the first process variable F0. The matching process is performed within a working range K AB In particular, the working point K AP If the threshold S OR is determined, and when this threshold is exceeded, the disconnection is interrupted by the fault F OR >S OR The faulty F-threshold S in Figure 3 is recognized as OR This newly set threshold S, denoted as OR is at a higher value, such as a higher detected light intensity of the process radiation 19. For example, the threshold S O is a functional context S with a proportionality constant p. OR =p*(F 0R / F0) depending on the detected miscut variable F OR The threshold S OR The miscut variable F can be changed by about 20%, i.e., (F 0R If the change is only 1.2 p, the threshold S O is the threshold S OR The miscut variable is now increased by 20% to the faulty miscut variable F 0R If the device moves during operation, the threshold S O If the threshold value S is exceeded, the evaluation device 30 will erroneously detect a malfunction. O Let S be the threshold value. OR After moving or resetting the threshold value S0 to 0, the fault is only recognized in the higher first process variable F or miscut variable F, which thereby corresponds to the actual conditions of the laser processing tool 1 during operation. The adjustment or modification of the threshold value S0 is performed continuously during the operation of the laser processing tool 1. The modified threshold value S0 is accordingly OR Then, the process variable F O The original threshold S is modified according to another threshold O Instead, a threshold S is used to detect the disconnection.OR can be continuously varied. In particular, the threshold value S of the first light intensity-dependent process variable F OR can be continuously varied in the control process.

[0037] The functionality of the described laser processing tool 1 and the laser processing method is further illustrated using the hatched areas in Fig. 3. The miscut areas represent areas in the diagram of the second process variable K where the evaluation device 30 detects a cut interruption. The hatched miscut areas are defined, for example, as rectangular areas, but may take any shape in the diagram. During fault-free operation, in the hatched characteristic curve, the detected cut interruption is a function of the fault-free miscut variable S O In the case of a faulty operating solid characteristic curve, as described, a cut interruption is detected when the miscut variable S has a higher value than the intensity-dependent first process variable F has. OR is at the threshold.

[0038] The first process variable F also corresponds to the operating point K in uncontrolled operation. AP If the known working range K is not reached, AB The second process variable K can be operated within the working range K AB To minimize AP Ideally, the temperature should be adjusted to .

[0039] In another example, the control setpoint R of the laser processing process is O and the control setpoint R is assigned to the value F of the first process variable F. O From value F OR Depending on the change to the setting value R OR The evaluation device 30 changes the working point K AP In or work area K ABIf a change in the first process variable F, e.g., an increased light intensity due to a fault in the optical system 23, is detected within the control setpoint R, this increased light intensity will be inaccurately contributed to the changed trailing length. With an increase in the trailing length, the laser processing tool 1 will experience an undesirable change in the speed of the feed of the workpiece 8. The correct trailing length is determined by the control setpoint R. AP In or work area K AB In order to ensure that speed control of the feed rate of the workpiece 8 continues to be performed, the control setpoint R is determined using the light intensity independent process variable K in the evaluation device 30 such that the feed rate of the workpiece 8 remains unchanged regardless of the first process variable F. OR This feature prevents the control process from being disturbed by an inaccurate measurement of the light intensity dependence of the first process variable F. In other words, the second process variable K is changed to the control setpoint R OR , to correct for inaccurate measurements of the first process variable F with reference to the laser processing tool 1. OR The adjustment to allows the use of the first process variable F to continue despite a malfunction of the optical system 23. This avoids a subsequent calibration of the first process variable F, which would be necessary otherwise. The principle of changing the control setpoint R therefore corresponds to the principle of changing the threshold at which a disconnection interruption is detected.

[0040] The described method for laser processing is also applicable to other technical fields and is not limited to the technical field of the laser processing tool 1. The described method is applicable in all technical domains where process variables change and thresholds are automatically adjusted, changed or controlled without recalibration.

[0041] List of reference symbols 1 Laser processing tools 4 Laser processing head 5 Workpiece Rest 6 Laser Beam 8 Workpiece 8a surface 9 Calf 10 Cutting gas 14 Equipment 15 Focusing Lens 16 Cutting gas nozzle 17 Deflection Mirror 18 Interaction area 19 Process Radiation 20 additional deflection mirrors 21 Camera 22 Laser beam axis 22a Scan beam axis 23 Optical system 24 Filters 25 light source 26 Partially transparent mirror 27 Illumination Radiation 28 Areas under surveillance 29 Cut surface 30 Evaluation Units 31 Control device 32 First translation axis 33 Second translation axis 34 Protective Glass

Claims

1. A laser processing method, comprising: at least one working area K ＡＢ Within or working point K ＡＰ At least one threshold value S for a first light intensity dependent process variable F in ０ and a method step for defining - Working range K ＡＢ Within or working point K ＡＰ detecting a second process variable K during operation of the laser processing tool (1), the second process variable K being independent of light intensity; When changing the process conditions, at least one working range K ＡＢ Within or working point K ＡＰ determining a change in the first process variable F; the value F of the first process variable F ０ From the value F ０Ｒ In response to the change to at least one threshold value S ０ Let S be the threshold value. ０Ｒ and a method step of changing the laser beam into a laser beam.

2. The control setting value R of the laser processing process is set to the threshold value S ０ and a method step of assigning the value F of the first process variable F ０ From the value F ０Ｒ In response to the change to the control setting value R, ＯＲ and a method step of changing the laser beam intensity to a laser beam intensity.

3. A laser processing method according to claim 1 or 2, comprising the method step of controlling the second process variable K as a trailing length or a tilt angle of the cutting surface (29) on the workpiece (8) to be cut.

4. as the first process variable F, the working point K in response to the light intensity recorded on the workpiece (8), ＡＰ or in the working range K ＡＢ At least one threshold value S ０ The threshold value S ０Ｒ 2. A laser processing method according to any one of the preceding claims, comprising the method step of:

5. the modified threshold value S ０Ｒ 4. The laser processing method according to any one of the preceding claims, comprising the method step of determining a fault in the laser processing tool (1) based on:

6. the modified threshold value S ０Ｒ The laser processing method of claim 5 , further comprising the method step of determining a cut interruption as a defect based on:

7. at least one threshold value S in response to the modified first process variable F; ０ The threshold value S ０Ｒ 4. A method according to any one of the preceding claims, comprising the method step of proportionally varying

8. The laser processing method according to any one of the preceding claims, comprising a method step of controlling the second process variable K as a controlled variable with an adjustable variable of a feed rate of a workpiece (8) in the laser processing tool (1) or of a power supply of the laser processing tool (1).

9. The change in the first process variable F is detected in a position-dependent, time-dependent, and / or direction-dependent manner, and the at least one threshold S ０ 5. A laser processing method according to any one of the preceding claims, characterized in that is varied or set in a position-dependent, time-dependent and / or direction-dependent manner.

10. A laser processing tool (1), comprising an evaluation device (30), the evaluation device (30) being adapted to evaluate at least one working range K ＡＢ Within or working point K ＡＰ At least one threshold value S for a first light intensity dependent process variable F in ０ Define the work range K ＡＢ Within or working point K ＡＰ A second process variable K independent of the light intensity during operation of the laser processing tool (1) is detected, and when the process condition is changed, at least one working range K ＡＢ or the working point K ＡＰ determining a change in the first process variable F in ０ From the value F ０Ｒ In response to the change to at least one threshold value S ０ Let S be the threshold value. ０Ｒ A laser processing tool (1) characterized in that it is designed to change

11. 11. A laser processing tool (1) with an evaluation device (30) according to claim 10, characterized in that the evaluation device (30) is designed to control as a second process variable K a trailing length or a tilt angle of a cutting surface (29) on the workpiece (8) to be cut.

12. The evaluation device (30) determines as the first process variable F the at least one threshold value S in dependence on the recorded light intensity within the working range of the workpiece (8). ０ The threshold value S ０Ｒ 12. A laser processing tool (1) having an evaluation device (30) according to claim 10 or 11, characterized in that it is designed to change

13. The evaluation device (30) changes the threshold value S ０Ｒ A laser processing tool (1) having an evaluation device (30) according to any one of claims 10 to 12, characterized in that it is designed to detect defects of the laser processing tool (1) on the basis of

14. The evaluation device (30) determines the at least one threshold value S in response to the changed first process variable F. ０ The threshold value S ０Ｒ 14. A laser processing tool (1) having an evaluation device (30) according to claim 10, characterized in that it is designed to proportionally change

15. A computer program product in an evaluation device (30) for carrying out the method according to any one of the preceding claims.

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