Laser cutting method and laser cutting machine

Abstract

The present invention relates to a laser cutting method, a laser cutting machine, and a computer program product. The object of the present invention is to provide an improved laser cutting method and an improved laser cutting machine. To solve the object, a laser cutting method is provided, which includes the method steps of: a. cutting a workpiece with a high-power laser cutting beam along a cutting line; b. determining a good or bad cut of the workpiece during cutting of the workpiece; c. scanning the cutting line of the workpiece with a low-power laser scanning beam or irradiation beam and recording the scanning data; d. changing at least one parameter of the laser cutting machine; repeating the method steps a. to c.; and evaluating the scanning data in relation to different parameters of the laser cutting machine in a control device.

Description

[Technical Field]

[0001] The present invention relates to a laser cutting method, a laser cutting machine and a computer program product according to the preambles of the independent claims. [Background technology]

[0002] The technical field of industrial cutting of various materials using laser radiation is becoming increasingly important. Laser radiation from high-power laser cutting machines, typically in the range of several kilowatts, is typically used to cut workpieces from various materials. In exceptional cases, the workpiece may not be completely cut, leaving a separated portion on the workpiece. An incomplete cut that does not result in separation of the workpiece along the cutting line or cutting gap is called a defective cut. A defective cut is usually determined by a machine operator in a further method step, and the defective workpiece is fed to a laser cutting machine for recutting. Another possibility is known from Patent Document 1, in which the workpiece is passed over by a distance sensor in the area of ​​the tear, checking whether a complete tear or separation cut is present. The workpiece is then sent to the laser cutting machine for reprocessing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] German Patent Application Publication No. 102010039525A1 Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved laser cutting method and an improved laser cutting machine. [Means for solving the problem]

[0005] For this purpose, a laser cutting method is provided which comprises the following method steps: a. cutting a workpiece along a cutting line with a high-power laser cutting beam; b. determining whether the workpiece is cut well or poorly while it is being cut; c. scanning a cutting line on the workpiece with a low-power laser scanning beam or irradiation beam and recording the scanning data; d. The method step of changing at least one parameter of the laser cutting machine; repeating method steps a. through c.; A method step in which the control device evaluates the scan data in relation to different parameters of the laser cutting machine. In this case, scanning of the cutting line on the workpiece is carried out by a low-power laser scanning beam while the laser processing head is retracting.

[0006] Further provided is a laser cutting machine for cutting a workpiece along a cutting line, the laser cutting machine comprising at least one laser light source for generating a high-power laser cutting beam, a camera for detecting a good or bad cut of the workpiece while cutting the workpiece, a low-power laser scanning beam from the laser light source or an illumination beam of the illumination unit, and a control device configured to change at least one parameter of the laser cutting machine and to evaluate scanning data of the low-power laser scanning beam or illumination beam in relation to different parameters of the laser cutting machine.

[0007] Further provided is a computer program product for carrying out the method in a control device.

[0008] Embodiments of the invention are defined in the dependent claims.

[0009] In one embodiment, a camera is used to determine good or bad cuts while the workpiece is being cut, thereby ensuring that bad cuts are recognized in real time.

[0010] In a further embodiment, the method step of evaluating includes determining the location of the defective cut. Subsequently, a method step of cutting the workpiece with a high-power laser cutting beam is performed at the determined location of the defective cut. Determining the location of the defective cut on the workpiece is, on the one hand, useful when setting the parameters of the laser cutting machine to achieve improved cutting results. On the other hand, by precisely controlling the high-power laser cutting beam only to the locations of the workpiece that are not to be cut, the defective cut can be eliminated, thereby eliminating the defective cut in an economical way.

[0011] A further embodiment depicts the following method steps: - method steps of classifying the recorded scan data according to different parameters into good cuts or bad cuts; the method steps of providing the scanned data classified as a good cut or a bad cut to a control device; A method step of setting at least one of the parameters classified as a good cut in the laser cutting machine by the control device. These method steps allow for improved parameterization of the laser cutting machine in an automated manner, as a result of which the risk of a faulty cut occurring during operation of the laser cutting machine is significantly reduced.

[0012] After the defective cut is recognized, and while the laser processing head for cutting the workpiece with the high-power laser cutting beam is retracted, the cutting line on the workpiece is scanned with a low-power laser scanning beam. On the one hand, this scanning quickly determines whether there is a defective cut or whether the defective cut has been erroneously recognized. On the other hand, this scanning determines the length and extent of the defective cut.

[0013] In a further embodiment, at least one parameter of the laser cutting machine is changed from the selection of the focus position, the laser power of the laser cutting machine, the focus diameter, the distance between the laser nozzle and the workpiece, the feed speed of the workpiece, and / or the gas pressure of the protective gas, and by changing or adjusting at least one of the above parameters, the cutting result of the laser cutting machine is changed.

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an exemplary schematic diagram of a laser cutting machine. [Figure 2] 1 is a schematic side view of a sensor device together with a control device of a laser cutting machine, located under a workpiece to be machined by a laser beam of the laser cutting machine; [Figure 3] 4 shows an exemplary signal curve of a signal of a sensor device evaluated in a control device from a cutting line having areas of good cutting and areas of bad cutting. DETAILED DESCRIPTION OF THE INVENTION

[0016] FIG. 1 schematically illustrates a laser cutting machine 10 equipped with a laser source 22, a laser processing head 24, and a workpiece support 25. Preferably, a solid-state laser is used as the laser source 22, with laser radiation being supplied to the laser processing head 24 via a laser light cable. The high-power laser cutting beam 16 generated by the laser source 22 is guided to the laser processing head 24 by a beam guide 23, where it is focused and directed perpendicular to the surface of the workpiece 2 using mirrors. In this case, high power typically represents a power output on the order of several kilowatts. Accordingly, the beam axis (optical axis) of the laser cutting beam 16 runs perpendicular to the workpiece 2 in this embodiment. In the illustrated example, the laser source 22 is a CO laser source. Alternatively, the laser cutting beam 16 can be generated, for example, by a solid-state laser with a corresponding laser source. Similarly, a low-power laser scanning beam is generated and directed toward the workpiece 2. In this case, low power typically represents a power output on the order of several watts or several hundred milliwatts. The laser cutting beam 16 and the laser scanning beam may be provided by a laser source 22 by adjusting the power in the laser source 22 .

[0017] The laser cutting beam 16 is moved over the workpiece 2 to create a consistent kerf or cutting line 14 along which the laser cutting beam 16 typically cuts completely through the workpiece 2 .

[0018] Laser cutting is assisted by the addition of gas, which can be oxygen, nitrogen, compressed air, and / or other gases depending on the application, and which are stored in a connected cutting gas container 32. The generated particles and gases can be sucked out by means of a suction device 33 from a suction chamber (not shown) located below the workpiece support 25.

[0019] The laser processing head 24 and the workpiece 2 move relative to each other within the laser cutting machine 10. In the illustrated embodiment, the workpiece 2 rests on a workpiece support 25 during processing, and the laser processing head 24 moves along three axes X, Y, and Z of an XYZ coordinate system during processing. For this purpose, a drive device is provided, which moves a portal 30 that is movable in the X direction indicated by the double arrow. The portal 30 refers to a displaceable frame provided in the laser cutting machine 10, as exemplarily shown in FIG. 1. Within the working area designated by the displaceability of the laser processing head 24 or the workpiece 2, any processing position B in the X and Y directions can be moved. X、Y The laser processing head 24 can be displaced in the Y direction indicated by the double arrow by a further drive to move to the respective processing position B. X、Y 1, the laser cutting beam 16 has a feed direction V that corresponds to the relative speed between the laser processing head 24 and the workpiece 2. The feed direction V is indicated by an arrow on the workpiece 2 in FIG. 1. The laser processing head 24 is typically moved further in the Z direction when the laser processing head 24 is reset, returned, or moved to a cutting position.

[0020] The laser processing head 24 further includes a sensor device 1, as will be described later.

[0021] FIG. 2 shows a schematic side view of the sensor device 1 together with the signal-connected control device 15. In this embodiment, the sensor device 1 is included in a laser processing head 24. In this embodiment, the sensor device 1 includes an illumination unit 21 for generating an illumination beam 13 and selectively directing the illumination beam 13 via an optical element 8 to a suitable mirror 7. The mirror 7 directs the illumination beam 13 from the sensor device 1 via a dichroic deflection mirror 9, a focusing lens 3, and a cutting gas nozzle 6 to the processing area of ​​the workpiece 2. The cutting gas nozzle 6 is included in the laser processing head 24. The illumination beam 13 is reflected by the workpiece 2, and the reflected illumination beam 13 retraces the same path and passes through the mirror 7 to be photographed by the camera 11. Instead of the camera 11, a photodiode can be provided to detect the reflected illumination beam 13. In this way, an image of the processing area on the workpiece 2 is recorded by the camera 11 or the photodiode, whereby the processing area essentially includes the cutting line 14 with adjacent workpiece parts generated by the laser cutting beam 16. The cutting line 14 is thus swept or scanned, and scanning data is recorded. The laser cutting beam 16 is supplied in the laser processing head 24 via a deflection mirror 9, through the focusing lens 3 and the cutting gas nozzle 6, and the laser cutting beam 16 is emitted from the laser processing head 24 by the cutting gas nozzle 6 at high energy, impinges on the workpiece 2, and completely cuts the workpiece 2 in a known manner. In an alternative embodiment, the sensor device 1 does not include the irradiation unit 21 and the optical element 8. In this embodiment, the cutting line 14, which has adjacent areas on the workpiece 2, is swept or scanned by a low-power laser scanning beam. The low-power laser scanning beam can be generated by a laser source 22 that also generates the high-power laser cutting beam 16. At that time, the laser source 22 switches from a high-power cutting mode to a low-power scanning mode. Thus, in this alternative, cutting and scanning are performed sequentially on the workpiece 2. In particular, in this embodiment, the cutting line 14 on the workpiece 2 is scanned by a low-power laser scanning beam while the laser processing head 24 is retracting.First, the workpiece 2 is cut with high power, and then the power is switched to low power, during which the laser processing head 24 moves back along the cutting portion on the cutting line 14 and scans the cutting line 14.

[0022] If a faulty cut 18 is detected, the laser processing head 24 typically returns along the same path it traveled. The laser processing head 24 stops, and the laser source 22 is set to low power by the control device 15, thereby enabling the laser scanning beam to be delivered. The laser scanning beam then scans the cutting line 14, and the scan data is recorded and evaluated as described above. From the scan data, it is determined whether a faulty cut 18 exists. In other words, it is determined whether the faulty cut 18 was detected and whether the faulty cut 18 was correctly determined. These measures eliminate incorrect determinations of a faulty cut 18. In particular, because the movement of the laser processing head 24 is optimized, it is possible to quickly determine whether a faulty cut 18 actually exists. After the fault detection, it is no longer necessary for the laser processing head 24 to return to the starting point for scanning the cutting line 14. Furthermore, the position of the faulty cut 18 is determined, and the laser processing head 24 then moves precisely to the position of the faulty cut 18 in cutting mode and cuts the workpiece 2 again by cutting again. The laser processing head 24 travels as short a distance as possible when scanning and cutting, to avoid unnecessary power loss due to cutting at the wrong position, to avoid unnecessary heating of the workpiece 2, and to avoid unnecessary deterioration of the quality of the cutting result of the workpiece 2. Repeated cutting may result in an insufficient cutting result.

[0023] FIG. 3 shows an exemplary signal curve of the sensor device 1 signal evaluated in the control device 15 in the upper part of FIG. 3, and the associated cutting line 14 in the lower part of FIG. 3. The cutting line 14 is indicated by a number in the millimeter range on the horizontal axis. The signal is generated by a photodiode or camera 11 using appropriate image processing software. The camera 11 typically captures the light intensity of the processing radiation at the cutting line 14, which appears during laser melting when the laser beam interacts with the material of the workpiece 2. It can be seen that the signal runs close to the zero line over a wide area. The associated cutting line 14 on the workpiece 2 is free of defects, so the workpiece 2 is completely cut, and only the amount of material necessary for a through-separation or through-cut is removed. The area on the workpiece 2 assigned a low signal is referred to as a good cut 17. The maximum brightness in the area of ​​the cutting gap of the cutting line 14 is used to check for the presence of a sparkle phenomenon during scanning and to classify the image as a separation cut or a good cut, on the one hand, and as a cut break or a bad cut, on the other hand. For this classification, a threshold value is established in the graph of Figure 3. If the intensity feature, which is the maximum brightness in the region of the cutting gap of the cutting line 14, is below the threshold value, the image is classified as a good cut, and if the intensity feature is above the threshold value, the image produced by the camera 11 is categorized or classified as a bad cut. The light intensity signal is referred to as the scanning mode signal.

[0024] On the right side of FIG. 3 , it can be seen that the cutting line 14 is disrupted and interrupted, resulting in an undesirable defective cut 18. In the signal curve, the area of ​​the defective cut 18 on the workpiece 2 results in a significant signal increase, recognizable by the signal to the right of the dashed line in FIG. 3 . This signal increase exceeds a threshold light intensity and is recognized by the control device 15. As described above, a good cut 17 or a defective cut 18 on the workpiece 2 is determined during cutting of the workpiece 2. The cutting line 14 on the workpiece 2 can be scanned using different methods, with the cutting data and the scanning data being recorded. In the example shown in FIG. 3 , the defective cut 18 occurs, as described above. Parameters of the laser cutting machine 10 are stored in the control device 15, such as the focal position, the laser power of the laser cutting machine 10, the focal diameter, the distance between the laser nozzle (in this case, the cutting gas nozzle 6) and the workpiece 2, the feed rate of the laser processing head 24, and the gas pressure of the protective gas. Further parameters of the laser cutting machine 10 can be stored in the control device 15. The parameters or parameter sets of the laser cutting machine 10 are known in the example of FIG. 3 with a faulty cut 18. If at least one parameter of the laser cutting machine 10 is changed and the laser cutting process is repeated, the method steps of cutting, scanning, recording and evaluating the scan data are performed with the at least one changed parameter, as described above. With the at least one changed parameter, a good cut 17 or a faulty cut 18 is again determined, and the corresponding parameter or parameter set is assigned to the good cut 17 or faulty cut 18. The above method steps are optionally repeated, so that multiple parameter sets exist in the control device 15, and from each parameter set, it is recognized whether the parameter set resulted in a good cut 17 or a faulty cut 18, and in which part of the cutting line 14 the good cut 17 or the faulty cut 18 exists. For example, the feed rate parameter of the laser processing head 24 is changed after each cutting process. The cutting process with the recording or depiction of the scan data with the changed feed rate is repeated until a faulty cut is recognized. Therefore, the feed speed of the laser processing head 24 at which the defective cutting occurred is recognized by the control device 15.Therefore, the laser cutting machine 10 can be configured so that the feed rate parameter does not exceed the threshold at which a poor cut occurs.

[0025] The scan data associated with various parameters or parameter sets of the laser cutting machine 10 is evaluated in the control device 15 using appropriate software. For example, some parameters or parameter sets are assigned to good cuts 17, while other parameters or parameter sets are assigned to bad cuts 18. The scan data recorded with different parameters is classified and stored as either good cuts 17 or bad cuts 18. In this way, the control device 15 has a category of parameters or parameter sets assigned to good cuts 17 and a category assigned to bad cuts 18. Furthermore, data on the location of uncut areas is assigned to the category of bad cuts 18. Essentially, the parameters that lead to good cuts 17 are automatically set or adjusted in the laser cutting machine 10. In this way, the laser cutting machine 10 is maintained in an operating state that essentially enables good cuts 17 and avoids bad cuts 18. In this way, the laser cutting machine 10 is, so to speak, trained. Furthermore, the classified data set can be used to train a machine learning model. [Explanation of symbols]

[0026] 1. Sensor device 2 Work 3. Focusing Lens 4 Focusing device 6 Cutting gas nozzle 7. Mirror 8 Optical Elements 9 Dichroic Mirror 10 Laser Cutting Machine 11 Camera 13 Irradiation beam 14 Cutting line 15 Control device 16 laser cutting beams 17 Good cutting 18 Bad cut 21 Irradiation unit 22 Laser light source 23 Beam Guide 24 Laser processing head 25 Work support 27 Support Web 30 Portal 32 Cutting gas bottle 33 Suction device

Claims

1. 1. A laser cutting method comprising the following method steps: a. cutting a workpiece (2) along a cutting line (14) with a high-power laser cutting beam (16) emitted from a laser processing head (24); b) determining a good cut (17) or a bad cut (18) of the workpiece (2) during cutting of the workpiece (2); c) scanning the cutting line (14) of the workpiece (2) with a low-power laser scanning beam or illumination beam (13) emitted from the same laser processing head (24) and recording the scanning data; d. The method step of modifying at least one parameter of the laser cutting machine (10); repeating said method steps a. to c.; and a method step of evaluating the scanning data in a control device (15) in relation to different parameters of the laser cutting machine (10), A laser cutting method, wherein scanning of the cutting line (14) on the workpiece (2) is performed by the low-power laser scanning beam or irradiation beam (13) while the laser processing head (24) is retracting.

2. A laser cutting method as described in claim 1, characterized by a method step of using a detector (11) to determine a good cut (17) or a bad cut (18) during cutting of the workpiece (2).

3. said evaluating method step including the method step of determining the location of a faulty cut (18); 3. The laser cutting method according to claim 1 or 2, characterized in that it comprises a subsequent method step of cutting the workpiece (2) with the high-power laser cutting beam (16) at the determined location of the defective cut.

4. a method step of classifying the scan data recorded according to different parameters into good cuts (17) or bad cuts (18); the method steps of providing said scan data classified as good cuts (17) or bad cuts (18) to said control device (15); and a method step of setting at least one of the parameters classified as a good cut (17) in the laser cutting machine (10) by the control device (15).

5. 3. The laser cutting method according to claim 1 or 2, characterized by a method step of changing at least one parameter of the laser cutting machine (10) from the selection of a focus position, a laser power of the laser cutting machine (10), a focus diameter, a distance between the laser nozzle and the workpiece (2), a feed speed of the laser processing head (24), and / or a gas pressure of a protective gas.

6. A laser cutting machine (10) for cutting a workpiece (2) along a cutting line (14), comprising: at least one laser light source (22) for generating a high-power laser cutting beam (16) emitted from a laser processing head (24); a detector (11) for detecting a good cut (17) or a bad cut (18) of the workpiece (2) during cutting of the workpiece (2); A laser cutting machine (10) equipped with a low-power laser scanning beam emitted from the same laser processing head (24) from the laser light source (22) or an irradiation beam (13) from an irradiation unit (21); a control device (15) configured to change at least one parameter of the laser cutting machine (10) and to evaluate scanning data of the low-power laser scanning beam or the illumination beam (13) in relation to different parameters of the laser cutting machine (10), 10. A laser cutting machine (10), characterized in that the laser cutting machine (10) is configured to carry out the laser cutting method according to claim 1.

7. 7. The laser cutting machine (10) according to claim 6, characterized in that the control device (15) is configured to classify and store the scanning data recorded according to different parameters into good cuts (17) or bad cuts (18).

8. 8. The laser cutting machine (10) according to claim 6 or 7, characterized in that the control device (15) is configured to set at least one of the parameters to the laser cutting machine (10) that is classified as a good cut (17).

9. 8. The laser cutting machine (10) according to claim 6 or 7, characterized by a control device (15) for evaluating the signal from the detector (11) and for setting the power of the laser light source (22) to a high power for cutting the workpiece (2) and to a low power for scanning the cutting line (14) with the laser scanning beam.

10. 8. The laser cutting machine (10) according to claim 6 or 7, characterized in that the low-power laser scanning beam consists of at least one pulsed laser beam or a continuous laser beam.

11. 1. A computer program product comprising: A computer program product for implementing the method according to claim 1 or 2 in a control device (15).

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