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 by means of laser radiation is becoming more and more important. When cutting workpieces from various materials, laser radiation from high-power laser cutting machines in the range of several kilowatts is usually used. In exceptional cases, the workpiece is not completely cut and the part to be separated remains on the workpiece. An incomplete cut of the workpiece that does not lead to separation of the workpiece along the cutting line or cutting gap is called a bad cut. A bad cut is usually determined by the machine operator in a further method step, and the badly cut workpiece is fed to the laser cutting machine for recutting. Another possibility is known from DE 101 14 133 A1, in which the workpiece is passed by a distance sensor in the region of the tear, and it is checked whether there is a complete tear or a separation cut. 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 PRESENT EMBODIMENT 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 with a high-power laser cutting beam along a cutting line; b. determining whether the workpiece is cut well or poorly while the workpiece is being cut; c. a method step of scanning a cutting line of the workpiece with a low-power laser scanning beam or irradiation beam and recording the scanning data; d. A method for modifying at least one parameter of a laser cutting machine; repeating method steps a. through c.; A method step of evaluating the scan data in the control device 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 means of 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 source for generating a high-power laser cutting beam, a camera for detecting a good or bad cut of the workpiece during cutting of the workpiece, a low-power laser scanning beam from the laser source or an illumination beam of the illumination unit, and a control device configured to modify at least one parameter of the laser cutting machine and to evaluate scanning data of the low-power laser scanning beam or the 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 controller.

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

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

[0010] In a further embodiment, the method step of evaluating comprises 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 in order to achieve an improved cutting result. On the other hand, by precise control of 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 manner.

[0011] A further embodiment depicts the following method steps. - classifying the recorded scan data according to different parameters into good cuts or bad cuts; providing the scan 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 an improved parameter setting 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 recognition of the faulty cut, and while the laser processing head for cutting the workpiece with the high-power laser cutting beam is retreating, the cutting line on the workpiece is scanned with a low-power laser scanning beam, which on the one hand quickly determines whether there is a faulty cut or whether the faulty cut has been erroneously recognized, and on the other hand determines the length and extent of the faulty 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, whereby the cutting result of the laser cutting machine is changed by changing or adjusting at least one of the above parameters.

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

[0015] [Figure 1] 1 is an exemplary schematic diagram of a laser cutting machine. [Diagram 2] FIG. 2 is a schematic side view of a sensor arrangement together with a control device of a laser cutting machine, located under a workpiece to be processed by a laser beam of the laser cutting machine. [Diagram 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 PREFERRED EMBODIMENTS

[0016] FIG. 1 shows a schematic diagram of a laser cutting machine 10 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, the laser radiation being fed 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 by a beam guide 23 to the laser processing head 24, where it is focused and directed perpendicular to the surface of the workpiece 2 by means of mirrors. In that case, the high power typically represents a power of the order of several kilowatts. The beam axis (optical axis) of the laser cutting beam 16 thus runs perpendicular to the workpiece 2 in this embodiment. In the illustrated example, the laser source 22 is a CO2 laser source. Alternatively, the laser cutting beam 16 can be generated, for example, by a solid-state laser with a corresponding laser source. In the same way, a low-power laser scanning beam is generated and directed to the workpiece 2. In that case, the low power typically represents a power of the order of several watts or several hundred milliwatts. The laser cutting beam 16 and the laser scanning beam may be provided from a laser source 22 by adjusting the power at 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: oxygen, nitrogen, compressed air and / or other gases depending on the application can be used as cutting gas, which are provided in a connected cutting gas container 32. 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 in the laser cutting machine 10. In the illustrated embodiment, the workpiece 2 rests on a workpiece support 25 during processing, while the laser processing head 24 moves along the three axes X, Y, Z of an XYZ coordinate system during processing. For this purpose, a drive is provided, which moves a portal 30 which is movable in the X direction indicated by the double arrow. The portal 30 refers to a displaceable frame which is provided in the laser cutting machine 10, as exemplarily shown in FIG. 1. Within the displaceability of the laser processing head 24 or the working area specified by the workpiece 2, any processing position B in the X and Y directions can be moved. X、Y To move the laser processing head 24 to the respective processing position B, the laser processing head 24 can be displaced in the Y direction indicated by the double arrow by a further drive. X、Y 1, the laser cutting beam 16 has a feed direction V which 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 or when it returns or moves to the cutting position.

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

[0021] FIG. 2 shows a schematic side view of the sensor arrangement 1 together with a signal-connected control device 15. The sensor arrangement 1 is included in the laser processing head 24 in this embodiment. The sensor arrangement 1 includes an illumination unit 21 for generating an illumination beam 13 and selectively emitting the illumination beam 13 via an optical element 8 onto a suitable mirror 7. The mirror 7 directs the illumination beam 13 from the sensor arrangement 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 takes the same path again and passes through the mirror 7 to be photographed by the camera 11. Instead of the camera 11, a photodiode can also be provided which detects 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 comprises a cutting line 14 with adjacent workpiece parts, which was generated by the laser cutting beam 16. Thus, the cutting line 14 is swept or scanned, and the scanning data is recorded. The laser cutting beam 16 is fed in the laser processing head 24 via the deflection mirror 9 through the focusing lens 3 and the cutting gas nozzle 6, where the laser cutting beam 16 leaves 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 with 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, which also generates a high-power laser cutting beam 16. The laser source 22 then switches from a high-power cutting mode to a low-power scanning mode. Thus, in this alternative, cutting and scanning are performed on the workpiece 2 sequentially. In particular, in this embodiment, the scanning of the cutting line 14 on the workpiece 2 is performed 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, while the laser processing head 24 retreats along the cut on the cutting line 14 and scans the cutting line 14 in the process.

[0022] The laser processing head 24 normally returns along the same path along which it has been moved if a faulty cut 18 is detected. The laser processing head 24 stops, the laser source 22 is set to low power by the control device 15, whereby the laser scanning beam can be supplied. The laser scanning beam then scans the cutting line 14, and the scanning data are recorded and evaluated as described above. From the scanning data it is determined whether there is a faulty cut 18. In other words, it is determined whether the detection of the faulty cut, which causes the laser processing head 24 to stop, the determination of the faulty cut 18, was correctly made. An erroneous determination of the faulty cut 18 is excluded by these measures. In particular, since the travelling run of the laser processing head 24 is optimized, it is possible to quickly determine whether a faulty cut 18 is actually present. After the fault detection, a run of the laser processing head 24 to the starting point for scanning the cutting line 14 is no longer necessary. Furthermore, the position of the faulty cut 18 is determined, after which the laser processing head 24 moves in the cutting mode exactly to the position of the faulty cut 18 and cuts the workpiece 2 by cutting again. The laser processing head 24 travels as short a distance as possible when scanning and cutting, so that unnecessary power losses due to cutting at incorrect positions are avoided, the workpiece 2 is not unnecessarily heated, and the quality of the cutting result of the workpiece 2 is not unnecessarily impaired. Repeated cutting may result in an insufficient cutting result.

[0023] FIG. 3 shows an exemplary signal curve of the signal of the sensor arrangement 1 evaluated in the control device 15 in the upper part of FIG. 3 and the associated cut line 14 in the lower part of FIG. 3. The cut line 14 is indicated by a number in the range of millimeters mm on the horizontal axis. The signal is generated by a photodiode or a camera 11 with the aid of suitable image processing software. The camera 11 then usually photographs the light intensity of the processing radiation at the cut line 14, which appears during laser melting upon interaction of the laser beam with the material of the workpiece 2. It can be seen that the signal runs close to the zero line over a wide range. The associated cut line 14 on the workpiece 2 is free of defects, so that the workpiece 2 is cut completely and only the amount of material required for a through-separation or through-cut of the workpiece 2 is removed. The areas on the workpiece 2 that are assigned a low signal are referred to as good cuts 17. The maximum brightness in the area of ​​the cut gap of the cut line 14 is used to check whether there is a glint phenomenon during the scan and to classify the image as a separation cut or good cut on the one hand and as a cut break or bad cut on the other hand. For this classification, a threshold value is established in the graph of Fig. 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 generated by the camera 11 is categorized or classified as a bad cut. The light intensity signal is called 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, whereby an undesirable defective cut 18 occurs. In the signal curve, the area of ​​the defective cut 18 on the workpiece 2 results in a significant signal increase, which can be seen by the signal to the right of the dashed line in FIG. 3. This signal increase is recognized by the control device 15 as exceeding a threshold value of light intensity. As described above, a good cut 17 or a defective cut 18 on the workpiece 2 is determined during the cutting of the workpiece 2, and the cutting line 14 on the workpiece 2 can be scanned by different methods, whereby the cutting data and the scanning data are recorded. In the example shown in FIG. 3, as described above, a defective cut 18 occurs. The parameters of the laser cutting machine 10 are stored in the control device 15, for example 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 are stored. 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 bad 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 of scan data and evaluation are carried out as described above with the at least one changed parameter. With the at least one changed parameter, a good cut 17 or a bad cut 18 is again determined, with the corresponding parameter or parameter set being assigned to the good cut 17 or the bad cut 18. The above method steps are repeated as desired, so that there are a number of parameter sets in the control device 15, and from each parameter set it is recognized whether a good cut 17 or a bad cut 18 was obtained with the parameter set and in which part of the cutting line 14 the good cut 17 and the bad cut 18 are present. For example, the feed rate parameter of the laser processing head 24 is changed after each cutting process. The cutting process with recording or depiction of the scan data with the changed feed rate is repeated until a bad cut is recognized. Therefore, the feed speed of the laser processing head 24 at which the defective cut occurred is recognized by the control device 15.Therefore, the laser cutting machine 10 can be set such that the feed rate parameters do not exceed a threshold at which a bad cut occurs.

[0025] The scanning data associated with the various parameters or parameter sets of the laser cutting machine 10 are evaluated in the control device 15 with the aid of suitable software. For example, parameters or parameter sets are assigned to good cuts 17, while other parameters or parameter sets are assigned to bad cuts 18. The scanning data recorded with the different parameters are classified and stored as good cuts 17 or bad cuts 18. In this way, in the control device 15, there are categories of parameters or parameter sets that are assigned to good cuts 17 and categories that are assigned to bad cuts 18. Furthermore, data of the location of the uncut areas are 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 allows good cuts 17 and avoids bad cuts 18. The laser cutting machine 10 is thus trained, so to speak. 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 beam 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) with a high power laser cutting beam (16) along a cutting line (14); b. determining, during cutting of said workpiece (2), a good cut (17) or a bad cut (18) of said workpiece (2); c. the method steps of scanning the cutting line (14) of the workpiece (2) with a low power laser scanning beam or illumination beam (13) and recording the scanning data; d. The method steps of modifying at least one parameter of the laser cutting machine (10); repeating said method steps a. to c.; and in a control device (15), a method step of evaluating the scanning data 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 during retraction of a laser processing head (24).

2. 2. The laser cutting method according to claim 1, characterized by the method step of determining good cuts (17) or bad cuts (18) during cutting of the workpiece (2) by means of a camera (11).

3. The method step of evaluating includes the method step of determining a 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. - classifying the recorded scan data according to different parameters into good cuts (17) or bad cuts (18); - providing said scan data classified as a good cut (17) or a bad cut (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. 5. The laser cutting method according to claim 1, 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 a 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 source (22) for generating a high power laser cutting beam (16); a camera (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) comprising a low-power laser scanning beam from the laser light source (22) or an irradiation beam (13) of an irradiation unit (21), 1. A laser cutting machine (10), comprising: 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 irradiation beam (13) in relation to different parameters of the laser cutting machine (10).

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 by different parameters into good cuts (17) or bad cuts (18).

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 of the laser cutting machine (10) that is classified as a good cut (17).

9. 9. The laser cutting machine (10) according to any one of claims 6 to 8, 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. The laser cutting machine (10) according to any one of claims 6 to 8, 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 any one of claims 1 to 5 in a control device (15).

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