Method and apparatus for monitoring the cutting process

Abstract

The present invention relates to a method for monitoring, in particular for controlling, a cutting process of a workpiece, the method comprising the steps of: focusing a processing beam, in particular a laser beam, on the workpiece; detecting a region to be monitored (21) of the workpiece, including an interaction region (22) where the processing beam interacts with the workpiece; and determining at least one characteristic parameter (L) of the cutting process, in particular a kerf (24) formed during the cutting process, based on the detected interaction region (22). According to the invention, based on the interaction region (22) detected during the fusion cutting process, the cut front length (L) of the cut front formed at the kerf (24) is determined as the characteristic parameter. The present invention also relates to a corresponding device for monitoring, in particular for controlling, the cutting process of a workpiece (2).

Description

[Technical Field]

[0001] The present invention relates to a method for monitoring, in particular control, a workpiece cutting process, comprising the steps of: focusing a processing beam, in particular a laser beam, onto a workpiece; detecting a region of the workpiece to be monitored, including an interaction region in which the processing beam interacts with the workpiece; and identifying at least one characteristic parameter of the cutting process, in particular a cut, formed during the cutting process, based on the detected interaction region. The present invention also relates to an apparatus for monitoring, in particular control, a workpiece cutting process, comprising: a focusing device for focusing a processing beam, in particular a laser beam, onto a workpiece; an image detection device for detecting a region of the workpiece to be monitored, including an interaction region in which the processing beam interacts with the workpiece; and an evaluation device configured to identify at least one characteristic parameter of the cutting process, in particular a cut, based on the detected interaction region. [Background technology]

[0002] Characteristic parameters of the laser cutting process, such as imminent cutting. interruption An apparatus of the type described above for monitoring a laser cutting process, which can be used to detect an imminent cutting, is known from the applicant's International Publication No. 2012 / 107331. interruption This is identified when the cutting slit falls below a predetermined slit width. Alternatively or additionally, the observed cutting surface is compared to a reference surface corresponding to the cutting surface in a good or high-quality cut. interruption This method can also detect when the beam intensity identified from the reference plane exceeds the target brightness limit for normal cutting.

[0003] In addition, International Publication No. 2012 / 107331 proposes detecting the upper and lower edges of the cutting front as material interfaces of the workpiece, and then determining the cutting front angle of the laser cutting process, taking into account the thickness of the workpiece. If the cutting front angle deviates from the target value or target range, this may indicate a cutting error or an unoptimal working point, which can be corrected by appropriate means, such as adjusting the cutting speed.

[0004] Cutting interruption A common cause is insufficient energy input to the workpiece. Excessively low energy per unit length leads to flattening of the cutting surface, i.e., widening of the cutting surface angle, which prevents complete removal of the molten material from the lower edge of the cut, potentially causing the molten material to solidify at the cut. Closure of the lower edge of the cut leads to process irregularity, which usually permanently hinders the separation cut. Therefore, the cutting surface angle, a characteristic parameter of the cutting slit, is crucial for the impending cut. interruption This serves as an indicator.

[0005] In coaxial process observation through a cutting nozzle, a problem arises when observing the material interface: the observation area is defined by the normally circular internal contour of the cutting nozzle. Particularly in heated cutting processes, where small nozzle diameters are used, even with good cutting, the lower edge of the cutting front surface lies outside the observation area defined by the nozzle opening, making it impossible to determine the cutting front surface angle with high reliability.

[0006] To solve this problem, in the applicant's International Publication No. 2015 / 036140, it is proposed to infer the cutting front angle as a characteristic parameter of the cutting process from brightness or intensity values ​​identified from images of the interaction region recorded during slow observation of the laser beam at a certain angle to the beam axis. By comparing the intensity value with a threshold, it is possible to infer that the cutting front angle has exceeded a critical value at which good cutting no longer exists.

[0007] International Publication No. 2016 / 181359 describes the detection of the upper and lower edges of the cutting surface using a camera positioned with an offset from the laser beam axis. In this case, the camera's viewing direction is directed towards the rear cutting slit, opposite to the cutting direction. Therefore, the lower edge of the cutting surface can be detected. From this camera image, controllable cutting surface tracking to a specific target value can be identified. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2012 / 107331 [Patent Document 2] International Publication No. 2015 / 036140 [Patent Document 3] International Publication No. 2016 / 181359 [Overview of the project] [Problems that the invention aims to solve]

[0009] Problems of the invention The problem on which the present invention is based is to provide a method and apparatus for monitoring, particularly for controlling, a cutting process, which enables the reliable identification of characteristic parameters of the cutting process, in particular, characteristic parameters of the cut surface formed during the cutting process, and / or enables advantageous control of the cutting process. [Means for solving the problem]

[0010] Subject matter of the invention This problem is solved, according to the first aspect, by a method of the type described at the beginning, characterized in that the length of the cutting surface formed at the cut is identified as a characteristic parameter based on the interaction region detected in the melt cutting process.

[0011] The inventors have recognized that by detecting the length of the luminescence phenomenon from the process zone or from the interaction region between the processing beam and the workpiece, it is possible to determine the cutting front length as a characteristic parameter of the melt cutting process and, in some cases, as a control variable for the melt cutting process. Typically, for this purpose, a thermal image of the region to be monitored or the interaction region is recorded, i.e., the intrinsic luminosity of the melt cutting process at wavelengths in the NIR / IR wavelength region is detected or observed, but in some cases, monitoring at other wavelengths, such as wavelengths in the UV wavelength region, is also possible.

[0012] In one variant, the detection of the area to be monitored is performed using an observation beam path that extends substantially coaxially with respect to the beam axis of the processing beam. A substantially coaxial observation beam path is understood to mean that the observation beam path extends coaxially or parallel to the beam axis, or extends at an angle of less than 5° (small) with respect to the beam axis of the processing beam. Here, it was shown that detection of luminescence phenomena by process observation based on a coaxial camera using an observation beam path that extends substantially coaxially with respect to the beam axis of the processing beam is more easily implemented from a system technology perspective than a detector with spatial resolution, such as an off-axis camera.

[0013] Preferably, the area to be monitored is detected by passing through the nozzle opening of the processing nozzle for ejecting the processing beam onto the workpiece. An imaging sensor system with a vertical or quasi-vertical view (at an angle of less than 5° with respect to the beam axis of the processing beam or laser beam) through the processing nozzle images the hot cutting surface as process illumination, measures its length, and allows for control of the cutting process to its (target) length, and potentially the cutting process (see below).

[0014] In one development form, the nozzle opening of the machining nozzle from which the cutting gas jets out has a maximum extension length of at least 7 mm, preferably between 7 mm and 12 mm. Further, as will be explained in more detail below, a machining nozzle having a relatively large nozzle opening is advantageous for the controlled process management of the melting cutting process.

[0015] The maximum extension length is understood to mean the diameter of the nozzle opening in the case of a machining nozzle having a circular cross-section. In the case of other cross-sectional geometries of the nozzle, the maximum extension length is understood to mean the longest nozzle axis of the nozzle opening. In the case of a nozzle opening having an elliptical cross-section, the maximum extension length is, for example, the length of the longitudinal nozzle axis. The maximum extension length of the nozzle opening is measured on the nozzle side facing the workpiece.

[0016] In a further variant, the melting cutting process is carried out at a cutting gas pressure of less than 10 bar, preferably at a cutting gas pressure of more than 1 bar and less than 10 bar, particularly preferably at a cutting gas pressure of at least 2 bar and less than 6 bar. The cutting gas jets out from the nozzle opening of the machining nozzle together with the machining beam, and at the time of jetting out from the nozzle opening, the cutting gas pressure has a specified value. The cutting gas used in the melting cutting process is often an inert gas, such as nitrogen, but it is also possible to use, for example, a mixture containing a predetermined proportion of an oxygen component.

[0017] As described in the German Patent Application Publication No. 102016215019 of the applicant, when the cutting gas pressure is relatively small, by combining with a relatively large nozzle opening for cutting gas injection, which enables good covering of the cut edge, even at a significantly high travel speed, better edge quality can be achieved than in a conventional general high-pressure melting cutting process having a cutting gas pressure of 10 to 25 bar.

[0018] In a further variant, the melting cutting process is cutting interruptionIt is carried out at a cutting speed that reaches at least 80%, preferably at least 90% of the speed. Therefore, the cutting speed of the fusion cutting process is less than 20%, preferably less than 10% below the cutting interruption speed. The cutting quality is well maintained up to the cutting interruption limit, so that cutting can be performed at a traveling speed near the cutting interruption limit. On the other hand, in a conventional normal fusion cutting process (standard process) using a small-diameter nozzle and a high cutting gas pressure, the traveling speed range cannot be fully utilized up to the cutting interruption limit. This is because the quality of the cut edge deteriorates excessively. The cutting interruption speed, that is, the speed at which cutting interruption occurs can be determined (experimentally) in a series of prior measurements for each of various workpiece materials, workpiece thicknesses, and laser powers.

[0019] In one variant, the cutting front length is specified from an image of the interaction region as the length between two points along a contour section extending in the cutting direction of the interaction region, where the luminance or intensity is below a luminance threshold or intensity threshold. Therefore, along the length in the cutting direction between two points forming the start and end of the interaction region, the luminance of the light emission phenomenon in the image is greater than the luminance threshold. The luminance threshold or intensity threshold can be determined, for example, relative to a reference value of the luminance or intensity in the image. As a reference value to which the respectively measured intensities are associated or calibrated, for example, the maximum intensity value inside the image can be used. Additionally, the calibration of the image detection device can be performed in a reference cutting process using reference cutting parameters and / or by comparing the intensity measurement values with the values of a reference image detection device. The contour section whose length is used for specifying the cutting front length usually extends to the center inside the cut surface.

[0020] In a further modified form, the method includes a step of controlling the cutting front length to a predetermined target length by influencing at least one setting parameter of the cutting process. In the spirit of this application, control to a predetermined target length is understood to mean that control is performed to a certain target length, or that it is prevented from exceeding a predetermined target length, i.e., that the control prevents exceeding the target length.

[0021] The inventors have found that the cutting surface length is particularly important when cutting interruption We found that it is suitable for control at cutting speeds close to the actual cutting speed. On the other hand, in conventional standard processes for melt cutting, the cutting speed is about 20-40% lower than the progress speed achieved under the conditions specified above with respect to the cutting gas pressure and nozzle opening diameter. At the slower cutting speeds used in standard processes, the length of the luminescence phenomenon or the cutting front length changes only slightly with appropriate setting parameters of the cutting process that affect the energy input to the workpiece, such as the cutting speed (progress speed) or laser power. Therefore, in standard processes, process control using these setting variables or setting parameters is not advantageous.

[0022] In further developmental forms, the cutting speed (travel speed) between the processing beam and the workpiece and / or the output of the processing beam are affected as setting parameters for controlling the cutting front length. The increase in cutting front length with increasing travel speed becomes increasingly pronounced as the travel speed increases. Therefore, travel speed control (and corresponding control of the processing beam output) is particularly important in the cutting process described above. interruption This becomes possible at high cutting speeds that reach at least 80%, preferably at least 90%, of the speed.

[0023] At these high cutting speeds, on the one hand, changing influencing variables such as contamination of the protective glass or heating of optical elements in the processing head have a significant impact on the process results. interruptionBecause it is performed near the limit, the cutting is more efficient than in conventional standard processes where the cutting gas pressure is relatively high. interruption The likelihood of this occurring increases. On the other hand, under these process conditions, the luminescence phenomenon or significant change in the measured length of the cut surface, which depends on the cutting speed (travel speed) and / or laser output, can be used as good control variables by using the travel speed and / or the output of the processing beam as set variables or set parameters. By changing the travel speed or laser output, cutting can be done in a simple manner. interruption This can prevent the cutting process. In other words, the melt cutting process is a cutting process. interruption It can be guided again quickly from a sufficient distance. This ensures the robustness of the process under interference.

[0024] A further aspect of the present invention relates to an apparatus of the type described at the beginning, wherein the evaluation device is configured or programmed / set to identify the cutting front length of the cutting front formed in the cut as a characteristic parameter based on the detected interaction region. For this purpose, the evaluation device can evaluate an image of the area to be monitored, which includes the interaction region and is recorded, for example, through the nozzle opening of a processing nozzle, in order to identify the length of the luminescence phenomenon corresponding to the cutting front length in the cutting direction.

[0025] In one embodiment, the apparatus includes a control device for controlling the cutting front length to a predetermined target length by influencing at least one setting parameter of the cutting process. The setting parameter affects the energy input to the workpiece. The process can be controlled in particular by changing the cutting speed and / or laser power, and in particular by ensuring that the cutting front length, as determined by the evaluation device, corresponds to or does not exceed the target length.

[0026] In further developmental forms, the control device cuts the front length, interruptionThe system is configured or programmed / set to control the target length at a cutting speed that reaches at least 80%, preferably at least 90%, of the speed. Furthermore, as described above, the cutting front length can be controlled to a target length using the cutting speed as a setting parameter, as long as the cutting front length changes sufficiently depending on the cutting speed. This is particularly relevant when cutting interruption This applies to cases where the cutting speed is just below the specified speed.

[0027] Further advantages of the present invention will become apparent from the specification and drawings. Similarly, the features described above and those further described below can be used individually or in any combination. The illustrated and described embodiments should not be understood as a final enumeration, but rather as exemplary features for illustrating the present invention. [Brief explanation of the drawing]

[0028] [Figure 1] A schematic diagram of an embodiment of a device for monitoring and controlling a laser cutting process. [Figure 2] This figure shows images recorded by an image detection unit of the area of ​​the workpiece to be monitored, in order to identify the cutting front length as a characteristic parameter of the cutting process. [Figure 3] A diagram showing the length of the cutting surface as dependent on the ratio of the cutting speed to the cutting interruption speed.

[0029] In the following descriptions based on drawings, the same reference numeral is used for identical or functionally equivalent parts. [Modes for carrying out the invention]

[0030] Figure 1 shows an exemplary structure of a device 1 for process monitoring and control of a laser melt cutting process on a plate-shaped workpiece 2 using a laser processing system. Of the laser processing system, Figure 1 shows only one processing unit 3 (part of the laser processing head) of the laser processing unit, which has a focusing lens 4 for focusing the CO2, solid, or diode laser beam 5, a processing nozzle 6, and a deflection mirror 7. In this case, the deflection mirror 7 is formed to be partially transparent and therefore forms the incident side component of the device 1 for process monitoring. The device 1 for process monitoring is part of the laser processing head, similar to the processing unit 3.

[0031] The deflection mirror 7 reflects the incident laser beam 5 and transmits the process beam, which is reflected from the workpiece 2 and emitted by the interaction zone, in this example, in the wavelength range of approximately 550 nm to 2000 nm, related to process monitoring. Alternatively, a scraper mirror or a perforated mirror can be used to feed the process beam into the observation beam path 8, instead of the partially transmitting deflection mirror 7. However, the use of a scraper mirror typically leads to partial masking of the process beam and limitation of the raw beam diameter. The use of a perforated mirror usually leads to diffraction effects of the process beam and a strong influence on the laser beam.

[0032] In apparatus 1, a further deflection mirror 9 is positioned behind the partial transmission mirror 7, which deflects the process beam to a geometrically high-resolution camera 10 acting as an image detection unit. This camera 10 is positioned coaxially with respect to the laser beam axis 11 or its extension 11a, and therefore can be a direction-independent high-speed camera. Accordingly, in the illustrated example, the observation beam path 8 also extends coaxially with respect to the laser beam axis 11 or its extension 11a. In principle, there is a means for recording images by the camera 10 using an incident light method, i.e., in the VIS wavelength range, and in some cases, if an additional illumination source 15 is provided that irradiates a beam in the NIR range and inputs an illumination beam 17 to the beam path coaxially with respect to the laser beam axis 11 via a further partial transmission mirror 16, there is a means for recording images by the camera 10 in the NIR wavelength range as well. As the additional illumination source 15, for example, a laser diode with a wavelength of 658 nm or, for example, a diode laser with a wavelength of 808 nm can be provided. These can be arranged coaxially with respect to the laser beam axis 11, as shown in Figure 1, but they can also be arranged off-axis with respect to the laser beam axis 11. Alternatively, it is possible to record process illumination in the UV and NIR / IR wavelength ranges without additional illumination.

[0033] For improved imaging, in this example, a focusing imaging optical system 12, shown as a lens in Figure 1, is provided between the partially transparent mirror 7 and the camera 10. This imaging optical system focuses the beam related to process monitoring onto the camera 10. The aspherical configuration of the focusing imaging optical system or lens 12 can prevent or at least reduce spherical aberration during imaging.

[0034] In the example shown in Figure 1, the filter 13 in front of the camera 10 is advantageous if further beam or wavelength components should be excluded from detection by the camera 10. This filter 13 may be configured, for example, as a narrow-band bandpass filter with a small full width at half maximum to avoid or reduce chromatic aberration. The positions of the camera 10 along the laser beam axis 11, as well as the imaging optical elements 12 and / or filter 13 present in this example, can be set via a positioning system known to those skilled in the art, indicated for simplification by bidirectional arrows, and can be changed as needed.

[0035] In this example, camera 10 is operated without an additional illumination source 15. That is, the intrinsic illumination of the process zone in the NIR / IR wavelength range is detected. As shown in Figure 2, camera 10 records a high-resolution image 20 of the area to be monitored 21 (cutting area) of the workpiece 2 on its sensor surface 10a. This image 20 is defined by the circular inner contour of the nozzle opening 6a of the nozzle 6 (see Figure 1), whose diameter D or maximum extension length at the exit end of the nozzle 6 is between 7 mm and 12 mm in the illustrated example. The cutting process shown in Figure 1 is a molten cutting process using nitrogen as the cutting gas. Nitrogen is used at a relatively low cutting gas pressure p, preferably between 1 bar and 10 bar, and ideally between 2 bar and about 6 bar, less than about 10 bar. S The cutting gas injection 14, which has the properties of [unclear], is ejected from the nozzle opening 6a of the processing nozzle 6.

[0036] The nozzle 6 may be configured as an annular flow nozzle having two (usually concentric) nozzle openings, as an alternative to the example shown in Figure 2. In this configuration, the laser beam 5 is emitted through the opening of the inner nozzle, and the cutting gas jet 14 is ejected through the outer nozzle opening, or through both the inner and outer nozzle openings. In this case, the outer nozzle opening has a diameter or maximum extension of at least 7 mm. Image recording by the camera 10 is performed through the inner nozzle opening, and therefore the image 20 is defined by the circular inner contour of the inner nozzle opening, which has, for example, a diameter of 3 mm.

[0037] The evaluation device 18 shown in Figure 1 is used for evaluating the image 20, in particular for detecting the interaction region 22 within the area 21 of the workpiece 2 to be monitored. The evaluation device 18 is signal-technically connected to a control device 19, also shown in Figure 1, which controls the laser cutting process in open-loop or closed-loop mode, in particular depending on characteristic parameters of the laser cutting process identified by the evaluation device 18, the cutting front length L of the cutting front 23 formed during the cutting process (see Figure 1), the cutting front 23 is adjacent to the cut surface 24 in the direction of travel or opposite to the cutting direction (i.e., in the negative X direction). As can be seen from Figure 2, the cutting front length L between point P1 at the front end of the interaction region 22 and point P2 at the rear end of the interaction region 22 is measured along the direction of travel or cutting, along which the laser beam 5 is guided over the workpiece 2 at the cutting speed or travel speed V (see Figure 1). In the illustrated example, the direction of travel corresponds to the X direction.

[0038] To determine the front length L of the cut, rapid image recording can be performed during the cutting process using an image detection device 10 at a frequency of, for example, 100 to 1000 Hz. Each image 20 is evaluated, for example, by a threshold comparison method, i.e., here, the binarization of each image 20 is performed by comparing the intensity value of the luminescence phenomenon in each recorded pixel with a threshold. From the binarized image 20, the length of the luminescence phenomenon in the cutting direction (X direction) is determined, and this length corresponds to the front length L of the cut. That is, the front length L of the cut is obtained from the image 20, for example, by the luminance threshold I of the contour cross section 25 of the luminescence phenomenon extending in the cutting direction (X direction). S This can be determined through, that is, here, the cutting front length is determined by one or more predetermined luminance thresholds I SIt can be specified as the length L between two points P1 and P2 of the contour section 25 that is less than this. Here, the measured value of the intensity I can be calibrated to a reference value in the image 20, for example, to the maximum intensity value of the image 20. Additionally, the calibration of the image detection device 10 can be performed using reference cutting parameters and by comparing the measured value with the measured value of a reference image detection device in a reference cutting process.

[0039] Cutting gas pressure p S Further related process parameters other than the diameter D of the machining nozzle 6 and the cutting speed V are the laser output P of the laser beam 5 or a laser source (not shown), the material of the workpiece 2, and the thickness d of the plate-shaped workpiece between the upper surface 2a and the lower surface 2b of the workpiece 2.

[0040] Furthermore, the melting cutting process described above can be performed using, for example, the following process parameters Structural steel: - d = 4mm, P = 10kW, V = 20m / min, p S = 7 bar - d = 10mm, P = 10kW, V = 5m / min, p S = 9 bar Stainless steel: - d = 4mm, P = 10kW, V = 21m / min, p S = 6 bar - d = 10mm, P = 10kW, V = 5.5m / min, p S = 4 bar Aluminum: - d = 4mm, P = 10kW, V = 35m / min, p S = 8 bar - d = 10mm, P = 10kW, V = 8m / min, p S = 9 bar can be implemented using.

[0041] Furthermore, in a melt cutting process carried out under the above-described conditions, that is, under conditions using a relatively low cutting gas pressure ps and a processing nozzle 6 with a large diameter D, good edge quality of the cut surface 24 can be achieved even at a high cutting speed V. This good cutting quality is particularly important for cutting interruption This is maintained even at cutting speeds V near speed Vs. In other words, this melt cutting method is interruption The cutting process can also be carried out at a high cutting speed V, which is at least 80%, preferably at least 90%, of the speed Vs. interruption The speed Vs can be determined in a series of prior measurements for each workpiece material, each workpiece thickness d, a predetermined laser power P, and a predetermined cutting gas pressure ps. interruption The value corresponding to the speed Vs can be stored, for example, in a technical table or storage device located in the evaluation device 18 or elsewhere.

[0042] Cutting interruption At high cutting speeds V near speed Vs, the cutting is faster than in conventional standard processes performed with higher cutting gas pressures ps and slower cutting speeds V. interruption This is highly likely to occur. interruption When cutting is imminent, the cutting front length L increases rapidly, and therefore it is advantageous to control the cutting front length L to a predetermined target length Ls using the control device 19. To achieve this, the control device 19 influences or modifies at least one setting parameter of the cutting process that affects the energy input into the workpiece 2.

[0043] Figure 3 shows the dependence of the cutting front length L on the cutting speed V, as determined using the evaluation device 18, in an example of structural steel with a workpiece thickness d of 8 mm, more precisely, the dependence of the cutting speed V on the cutting front length L. interruption This shows a dependence on the ratio with respect to the speed Vs. As can be seen in Figure 3, the increase in the cutting front length L becomes increasingly pronounced with increasing cutting speed V, and therefore, the control of the cutting front length L is done using the cutting speed V, or typically by cutting interruption This can be done using the progress speed as a setting parameter at a high cutting speed V that exceeds 80% or 90% of the speed Vs.

[0044] In the example shown in Figure 3, the cutting speed V and cutting interruption The target length Ls of the cutting surface, which corresponds to approximately 95% of the ratio with the velocity Vs, is approximately 0.6 mm. Alternatively or additionally, the control of the cutting surface length L to a predetermined target length Ls can also be performed using the laser output P of the laser beam 5 as a setting parameter. In either case, by influencing the energy input, the melt cutting process is controlled. interruption It can be guided at a sufficient distance, which ensures the robustness of the melt cutting process under interference.

[0045] When the cutting speed V or the progress speed is used as a setting parameter for control, the progress speed setting or progress speed adaptation ΔV (change in cutting speed V) can be performed at a regular period (e.g., 200 Hz). The progress speed adaptation ΔV is, for example, the current progress speed V and the target length L stored in the control device 19 or evaluation device 18. S The current cutting front length L and the target length L, as measured by the evaluation device 18. S From the difference ΔL between and and the (constant) proportionality constant f, the following relationship is obtained: ΔV / V = f * ΔL / L S It can be formed according to the following.

[0046] Controlling the cutting front length L to the target length LS can be done on an individual image basis if it is done slowly enough (e.g., with a period of 200 Hz), thus obtaining good control characteristics without overshoot. By averaging the individual images 20 recorded using the image detection device 10, the image processing, i.e., determining the cutting front length L, can be made more robust. For this averaging, for example, a moving average, and possibly a weighted average, can be calculated. For example, averaging can be performed by combining the current image and the last average image with predetermined weights to form a new average image. For example, the current image can be combined with the old average image at a ratio of 30% and the old average image at a ratio of 70% to form a new average image.

[0047] As mentioned above, the melt cutting process is a cutting process. interruption This can be performed at speeds near speed Vs, that is, it can prevent deterioration of the quality of the cut edge of the cut surface 24 and cutting. interruption Cutting without causing damage interruption The range of travel speeds up to speed Vs can be utilized almost completely.

Claims

1. A method for monitoring, and in particular for controlling, the cutting process of a workpiece (2), The steps include focusing a processing beam, particularly a laser beam (5), onto the workpiece (2), The steps include detecting a region (21) of the workpiece (2) to be monitored, which includes an interaction region (22) where the processing beam interacts with the workpiece (2), Based on the interaction region (22) detected in the cutting process, the step of identifying the length (L) of the cutting surface (23) formed on the cut surface (24) formed during the cutting process as at least one characteristic parameter of the cutting process, In a method including, The method further comprises the step of performing the cutting process at a cutting speed (V) that reaches at least 80%, preferably at least 90%, of the cutting interruption speed (Vs), by controlling the cutting front length (L) to a predetermined target length (Ls) by changing at least one of the cutting speed (V) and the output of the processing beam (P) as setting parameters of the cutting process.

2. The detection of the area to be monitored (21) is performed using an observation beam path (8) that extends substantially coaxially with respect to the beam axis (11) of the processing beam. The method according to claim 1.

3. The nozzle opening (6a) of the processing nozzle (6) for the injection of the cutting gas injection (14) has a maximum extended length (D) of at least 7 mm, preferably between 7 mm and 12 mm. The method according to claim 1 or 2.

4. The cutting process is carried out at a cutting gas pressure (ps) of less than 10 bar, preferably more than 1 bar and less than 10 bar, and particularly preferably at least 2 bar and less than 6 bar. The method according to any one of claims 1 to 3.

5. The length of the cutting surface is determined from the image (20) of the interaction region (22) as the length (L) between two points (P1, P2) along the contour cross section (25) extending in the cutting direction (X) of the interaction region (22). The method according to any one of claims 1 to 4.

6. The length of the cut front surface is determined by the fact that the measured values ​​of the intensity (I) of the luminescence phenomenon at the two points (P1, P2) fall below the luminance threshold (Is). The method according to claim 5.

7. A device (1) for monitoring, and especially for controlling, the cutting process of a workpiece (2), A focusing device for focusing a processing beam, particularly a laser beam (5), onto the workpiece (2), An image detection device (10) for detecting a region (21) of the workpiece (2) to be monitored, which includes an interaction region (22) where the processing beam interacts with the workpiece (2), An evaluation device (18) is configured to identify, based on the interaction region (22) detected in the cutting process, the length (L) of the cutting surface (23) formed on the cut surface (24) formed during the cutting process as at least one characteristic parameter of the cutting process, In a device equipped with, The apparatus (1) is characterized by comprising a control device (19) configured to perform the cutting process at a cutting speed (V) that reaches at least 80%, preferably at least 90%, of the cutting interruption speed (Vs) by changing at least one of the cutting speed (V) and the output of the processing beam (P) as setting parameters of the cutting process, thereby controlling the cutting front length (L) to a predetermined target length (Ls).

Images