Method and machine for cutting a workpiece

Abstract

The present invention relates to a method for cutting a workpiece (2), comprising: cutting the workpiece (2) along a predetermined cutting profile (18a), and checking whether a portion (17) of the workpiece is completely separated from the remaining portion (19) during the cutting process. On the one hand, if it is determined during the inspection that the portion of the workpiece is not completely separated from the remaining portion, the workpiece is recut along another cutting profile (18b) that is laterally offset relative to the predetermined cutting profile (18a). On the other hand, checking whether the portion of the workpiece has been separated from the remaining portion includes: irradiating the workpiece with a pulsed processing beam at the inspection position, detecting the radiation generated by the interaction between the processing beam and the workpiece, and evaluating the detected radiation to check whether the portion of the workpiece has been completely separated from the remaining portion, increasing the intensity of the processing beam during the irradiation of the processing beam, and terminating the irradiation of the processing beam once it is determined during the inspection that the portion of the workpiece is not completely separated from the remaining portion.

Description

[0001] This application is a divisional application of the invention patent application with application number 201780065042.5, application date October 17, 2017, and invention title "Method and machine for cutting and processing workpieces". Technical Field

[0002] This invention relates to a method for cutting and machining, particularly plate-shaped workpieces, such as sheet metal, comprising: cutting the workpiece along a pre-given cutting contour to separate a portion of the workpiece from the remaining portion, and checking whether the portion of the workpiece was completely separated from the remaining portion during the cutting process. The invention also relates to a machine for cutting and machining workpieces, comprising: a machining head for aligning a machining beam onto the workpiece; at least one motion device for generating relative motion between the machining head and the workpiece; a control device for controlling the at least one motion device; a method for separating a portion of the workpiece from the remaining portion by cutting the workpiece along a pre-given cutting contour; and an analysis and evaluation device configured to check whether the workpiece was completely separated from the remaining portion during the cutting process. Background Technology

[0003] The cutting of plate-shaped workpieces, such as sheet metal, can be performed using thermal processing or mechanical processing. In thermal processing using a processing beam, such as a laser beam, the workpiece portion is completely separated from the remaining portion along the cutting contour. The remaining portion can be the remaining workpiece or the remaining grid, from which the workpiece portion (the good part) is cut. Alternatively, the cut portion can be the remaining portion (scrap), such as cutting scrap, which is cut from the good part if necessary. The cutting contour used for cutting can be a self-closed cutting contour; however, this is not mandatory. For example, if the edge of the portion to be separated forms the outer edge of the workpiece, this portion is cut from the remaining grid without cutting the closed contour.

[0004] During cutting, especially laser beam cutting, it is possible that due to parameter errors and / or process errors, parts and / or remnants of the workpiece may not completely separate from the remaining grid or remaining workpiece and therefore fail to fall off the remaining workpiece or from the workpiece plane, creating interfering profiles for further processing. These unfallen interfering profiles, for example, caused by excess material, are particularly dangerous throughout the machining process on machines with moving shaft elements or support slides. Machine elements, especially moving machine elements, can be damaged by excess material or good parts partially located below the workpiece plane. Furthermore, the workpiece may move or be lifted unintentionally through form locking, resulting in a loss of profile accuracy. This can lead to partially poor cuts or no cuts, or the workpiece may be torn off the clamping element due to sufficient force engaging with the moving machine element, which is typically positioned on the clamping element during cutting.

[0005] WO 2015 / 080179 A1 addresses the problem of removing large, unusable portions when cutting holes in a workpiece. The solution involves introducing multiple cutting lines into the area of ​​the hole to be cut within the workpiece, thus breaking down the large portion into smaller ones. Subsequent hole cutting along the contour line begins with the portion that is set to fall along the contour line of the hole as a remaining part.

[0006] DE 10 2009 049 750 A1 describes a method for cutting material along a desired cutting trajectory by applying multiple laser pulses of a modulated laser beam. In one example, the cutting trajectory is repeatedly traversed by the modulated laser beam, wherein at least one cutting parameter is changed between two traversals. In this way, a first laser cutting point introduced into the workpiece upon the first traversal of the cutting trajectory can be offset relative to a second laser cutting point introduced into the workpiece upon the second traversal of the cutting trajectory.

[0007] DE 10 2011 004 117 A1 describes a method for controlling a cutting process on a workpiece to separate the workpiece from the remaining workpiece along a desired cutting profile. Here, after the cutting process, it is automatically verified that the workpiece portion has been completely cut from the remaining workpiece. Summary of the Invention

[0008] One aspect of the present invention is based on the objective of providing a method and machine for cutting workpieces that can automatically eliminate interfering contours that occur when a portion of the workpiece is not completely separated from the remaining portion. Another aspect of the present invention is based on the objective of providing a method and machine for cutting workpieces, wherein the complete separation of a portion of the workpiece from the remaining workpiece can be checked with high robustness.

[0009] According to the first aspect, the task is solved by the method mentioned at the beginning, characterized in that: if it is determined during a previous inspection that a portion of the workpiece has not been completely separated from the remaining portion, the workpiece is re-cut along another cutting contour that is laterally offset relative to a pre-given cutting contour. This other cutting contour extends at least along a segment or part of the pre-given contour, and in particular, may extend along the entire pre-given cutting contour. Typically, this other cutting contour is offset parallel to the pre-given cutting contour by a constant amount, although the amount of offset relative to the pre-given cutting contour may vary along the other cutting contour if necessary. Cutting along the cutting contour is performed using a processing beam, typically a laser beam; however, other types of processing beams, such as plasma beams or water beams, may also be used for this purpose.

[0010] In the method according to the invention, it is first checked, using a suitable sensing device or detector, whether further processing is required after the cutting process to completely separate the workpiece portion from the remaining portion. If so, the cutting process is then repeated along the cutting contour, more precisely along another cutting contour laterally offset from the predetermined cutting contour, so as to completely separate the workpiece portion (good portion) from the remaining portion (waste) and thereby prevent the incompletely cut good portion or remaining portion from forming an interfering contour when the workpiece is further cut. Lateral offset is suitable because when recutting along the predetermined cutting contour, that is, without lateral offset, damage is expected to occur on the edges of the good portion due to the edge region of the processing beam and / or due to the movement of the remaining portion within the cutting contour forming the cutting kerf, caused by the gas pressure of the process gas.

[0011] In a favorable variation, the other cutting profile is laterally offset toward the remaining portion (waste), that is, the distance relative to the good portion is increased. By appropriately selecting the amount of lateral offset, it is possible to prevent the edges surrounding the workpiece portion (good portion) from being damaged by the machining beam or by residue formed during recutting, or to prevent the edges surrounding the good portion from being welded or rounded.

[0012] In a variant, the other cutting profile is laterally offset by an amount such that the machining beam, aligned with the workpiece for cutting along the other cutting profile, irradiates the surrounding edges of the workpiece portion with an intensity less than 50%, preferably less than 30%, and especially less than 20% of the maximum intensity of the machining beam. For example, a machining beam in the form of a laser beam typically has an intensity distribution across its cross-section that decreases towards the edges from a maximum intensity typically present at least at the center of the beam's cross-section. The maximum intensity is sufficient to melt the workpiece for cutting, whereas the intensity typically found in the edge regions of a laser beam is not such a case, allowing the machining beam, especially a laser beam, to no longer damage the surrounding edges of the workpiece portion.

[0013] In the extended scheme, another cutting profile is laterally offset from the pre-given cutting profile by an amount that is at least 2%, preferably at least 5%, of the kerf width of the pre-given cutting profile. This lateral offset ensures that the processing beam and / or residue formed during recutting do not damage the surrounding edges of the workpiece portion.

[0014] In another variation, the other cutting profile is laterally offset from the given cutting profile by an amount less than the kerf width of the given cutting profile. If the process gas pressure used during cutting remains constant, i.e., it is also used for recutting, then a certain degree of offset from the given cutting profile is generally process-safe. If the other cutting profile is offset by a distance or amount equivalent to the kerf width of the given cutting profile, then doubling the kerf width in this way can cause interference with cutting quality, up to and including process tearing or incorrect cutting, making the kerf width of the given cutting profile the upper limit of the offset amount of the other cutting profile. Therefore, it should be anticipated that as the lateral offset approaches the width of the cutting profile or kerf, increasing amounts of residue will be released during recutting, reaching and adhering to the surrounding edges of the workpiece.

[0015] In the variant, during the recutting process, the laterally offset cutting profile is completed in a processing direction opposite to the pre-given cutting profile.

[0016] In another variation, the laterally staggered cutting profile formed during recutting extends only along a segment of the pre-given cutting profile.

[0017] In principle, there are several possibilities for subsequent processing or for re-cutting along a laterally offset cutting profile: the given cutting profile can be processed again completely or partially (that is, along a segment or section) with the same and / or different cutting parameters (e.g., maximum laser power, feed rate, process gas pressure, etc.), wherein the laterally offset cutting profile can be completed along the same processing direction as the given cutting profile or in the opposite direction to the given cutting profile. Here, another cutting profile can be cut by coinciding with or completely coinciding with the starting portion of the given cutting profile.

[0018] In another aspect of the invention, or in another variation, if it is determined during inspection that a portion of the workpiece has not completely separated from the remaining portion, a pre-given cutting profile or a laterally offset profile relative to the pre-given cutting profile is tracked using a cutting gas beam. In this aspect of the invention, or in this variation, the workpiece is not re-cut; instead, the cutting profile or, if necessary, the laterally offset profile is tracked using the cutting gas beam. The machining beam used for cutting is shut off when the cutting profile is tracked using the cutting gas beam. By using the cutting gas beam, slightly stuck portions of the workpiece can fall off without damage to quality, that is, without affecting the remaining portion or the edges of the workpiece portion, and be discharged downwards from the workpiece plane. The cutting effect performed by the machining beam is greater than that when using the cutting gas beam, allowing for re-cutting after tracking the cutting profile or the laterally offset profile. The direction of this other profile corresponds to the direction of the previously described other cutting profile. In particular, the cutting profile or the other profile can be tracked only partially (that is, along a segment or a section) by the cutting gas beam.

[0019] In another aspect of the invention, or in another variation, checking whether a workpiece portion has been separated from the remaining portion includes the following steps: irradiating the workpiece with a preferably pulsed machining beam at an inspection position within a pre-given cutting profile; detecting the radiation generated by the interaction between the machining beam and the workpiece; and analyzing and evaluating the detected radiation to check whether the workpiece portion has been completely separated from the remaining portion during the cutting process. The intensity of the machining beam at the inspection position is increased during the irradiation, and the irradiation of the machining beam is terminated once it is determined during the inspection that the workpiece portion has not been completely separated from the remaining portion during the cutting process. The machining beam used for inspection can, in particular, be a laser beam. The method of checking whether a workpiece portion has been separated from the remaining portion substantially corresponds to the method described in DE 10 2011 004 117 A1, cited at the outset, which is incorporated herein by reference.

[0020] The pulsed machining beam irradiating the workpiece can be a single pulse, especially a laser pulse, or multiple laser pulses. The machining beam is typically generated by the same beam source that also produces the machining beam used for cutting the workpiece. If necessary, a machining beam generated by other beam sources (such as a guided laser or the like) can also be used for inspection.

[0021] In cases where the cut portion (workpiece part or remaining part) may potentially form an interfering profile, inspection is typically conducted directly after cutting along the cutting profile to check whether the workpiece part has completely separated from the remaining part. In principle, all portions formed or cut out during the cutting process can potentially create interfering profiles for subsequent cutting operations.

[0022] For inspection, the machining beam is directed onto the workpiece at an inspection location within a pre-defined cutting profile—more precisely, within the cut portion (workpiece portion or remaining portion)—so that radiation generated during the interaction, if necessary, can be used to detect whether the workpiece portion has completely separated from the remaining portion. If the workpiece portion has completely separated from the remaining portion, it is typically ejected downwards from the workpiece plane; that is, the machining beam directed onto the workpiece at the inspection location falls into the hole formed within the cutting profile, resulting in virtually no interaction between the machining beam and the workpiece, and no or only minimal radiation intensity is detected.

[0023] As mentioned earlier, checking whether a part of the workpiece has separated from the remainder can typically be performed in the manner described in DE 102011 004 117 A1 cited at the beginning, that is, without increasing the intensity of the machining beam at the inspection location, and without terminating the machining beam irradiation once it is determined during inspection that the part of the workpiece has not completely separated from the remainder during the cutting process. If a fixed power of the machining beam is used during inspection for the entire inspection duration, it is usually necessary to painstakingly obtain characteristic data for each workpiece material, workpiece thickness, etc., and maintain this characteristic data in tables or databases. Despite the relatively laborious data acquisition, under certain circumstances, a particularly high degree of robustness in the inspection process cannot be achieved with a fixed power of the machining beam, as detailed below.

[0024] The inventors have recognized that, depending on the divergence of the processing beam and the position of the workpiece portion relative to the remaining portion, under unfavorable conditions, only the material of the workpiece portion heats up during irradiation by the processing beam, without generating sufficient radiation for detection due to the interaction between the processing beam and the workpiece portion. This unfavorable situation particularly exists when the workpiece portion, although still connected to the remaining portion, has sunk a few millimeters downward relative to the remaining portion. In this unfavorable situation, when inspected with excessively low power of the processing beam, it may be inferred that the workpiece portion has completely separated from the remaining portion, when this is not actually the case, potentially leading to a collision between components of the processing machine and the workpiece portion.

[0025] Conversely, if the processing beam intensity is too high at the inspection location, the workpiece may be marked by the processing beam, and a portion of the workpiece may be pierced by the processing beam. Because at least one recutting process may be required, especially laterally offset relative to the cut contour (as described above), to completely separate the workpiece portion from the remaining portion, multiple inspections are typically performed on the same workpiece portion. If the processing beam pierces through the workpiece portion, repeated inspections at the same inspection location can lead to undesirable results because radiation generated during interaction can no longer be measured at the piercing location, even though the workpiece portion still exists. The presence of the workpiece portion cannot be identified in this case, and there is a risk of collision in subsequent processes. Even if the workpiece portion is not completely pierced, excessive processing beam power may burn marks into the workpiece portion, accompanied by a large amount of spark spatter. Spark spatter can contaminate the machine, for example, in the form of spatter on the protective glass mounted on the processing head.

[0026] In the aspects of the invention described herein, or in the variations described herein, the intensity of the machining beam at the inspection position is increased during machining beam irradiation, and the machining beam is terminated once it is determined during inspection that a portion of the workpiece has not been completely separated from the remaining portion during cutting. In this way, sufficient interaction between the machining beam and the workpiece can be achieved during irradiation, thus reliably identifying workpiece portions that have not been completely separated from the remaining portion. On the other hand, irradiation is terminated once a portion of the workpiece has been identified as not being completely separated from the remaining portion, thereby preventing burn marks or workpiece penetration.

[0027] When the distance of a part of the workpiece from the focal point of the machining beam or to the remaining part is unknown, the presence of the workpiece part can be reliably identified in this way. If irradiation is not terminated prematurely, the range between the minimum and maximum intensity of the machining beam at the inspection position covers a range of values ​​meaningful for detecting the workpiece part. Termination of the machining beam irradiation at the inspection position can be performed in real time or via a real-time interface that effectively shuts down the beam source used to generate the machining beam immediately.

[0028] In a variation of this method, the power of the processing beam is progressively increased, particularly during irradiation of the inspection position. Increasing the power of the processing beam is a particularly simple possibility to increase the intensity of the processing beam at the inspection position. In this case, the processing beam irradiates the workpiece at a power lower than the maximum possible power of the beam source at the start of irradiation or inspection, and the power is continuously (i.e., in a power ramp) or progressively increased. If no radiation generated during the interaction is detected throughout the inspection duration, the power of the beam source can be increased, for example, to the maximum possible power during the inspection duration. If the presence of a portion of the workpiece is detected during the inspection duration, the irradiation of the processing beam can be terminated in real time, meaning that the time segment with a remaining power ramp or remaining power level during the inspection duration is no longer performed.

[0029] In another extended scheme, a processing beam pulses onto the inspection position, and the power of the processing beam pulses is progressively increased. In this case, the power of the processing beam can be progressively increased, for example, after a fixed pre-given time period or after each fixed pre-given time interval. The progressively increased pulse power can be the average power of the pulses, but it can also be other measures of pulse power, such as peak power (maximum power). The pre-given time period can, for example, be on the order of milliseconds.

[0030] In an extended version of this variant, the pulse power at least doubles with each progressively increasing pulse. By doubling the power in two successive pulses or stages, or, if necessary, increasing the power more intensely, the number of pulses required to cover a large range of processed beam power can be kept small. For example, using, say, five pulses or stages each with a constant duration, a range of values ​​between approximately 100W in the first stage and approximately 1600W in the fifth stage can be covered.

[0031] In another variation, the intensity of the machining beam at the inspection position is increased by moving the focal point of the machining beam toward the workpiece. In this case, the power of the machining beam is typically kept constant during the inspection duration; however, this is not mandatory. At the start of the inspection duration, or inspection interval, the focal point along the beam direction of the machining beam is selected to be at a distance from the workpiece, and the focal point moves toward the workpiece during the inspection duration. The machining beam may move to the upper surface of the workpiece at the end of the inspection duration; however, it is also possible that the focal point is located below the upper surface of the workpiece at a defined distance, for example, at the height of the lower surface of the workpiece.

[0032] The smaller the distance between the focal point and the workpiece, the smaller the diameter of the machining beam on the workpiece and the greater its intensity. As described earlier in connection with increasing the power of the machining beam, the movement of the focal point, thereby increasing the intensity of the machining beam at the inspection position, can be performed continuously or incrementally. To change the focal point, the distance between the focusing device and the workpiece can be changed. For this purpose, for example, the distance between the machining head, in which the focusing device is arranged, and the workpiece can be changed, particularly by reducing this distance.

[0033] In a variant, to check whether the workpiece portion has completely separated from the remaining portion during the cutting process, the intensity of the detected radiation is compared to an intensity threshold, and the irradiation of the processing beam is terminated once the intensity threshold is exceeded. The radiation generated during the interaction is detected using the aforementioned detector, and the wavelength of this radiation is, for example, in the infrared wavelength range. When the intensity threshold is exceeded, the presence of a workpiece portion in the remaining portion is recognized, and the beam source is ideally shut off in real time. As previously described, this effectively prevents the processing beam from penetrating the material, which could form burn marks or other material on the workpiece portion.

[0034] If the analysis and evaluation of detected radiation determines that a portion of the workpiece was not completely separated from the remaining portion during the cutting process, a recutting process can be performed immediately. Alternatively, a subsequent inspection can be performed first, and the inspection steps can be repeated. This is typically done by re-irradiating the workpiece with the processing beam at another inspection location and analyzing and evaluating the radiation generated at this time. A recutting process is only performed if the subsequent inspection also indicates that a portion of the workpiece was not completely separated from the remaining portion.

[0035] Of course, if the inspection shows that part of the workpiece has not been completely separated from the remaining part, the processing of the workpiece shall continue.

[0036] In the extended approach, the machining beam irradiates an inspection position within a pre-defined cutting profile. The distance from this inspection position to the pre-defined cutting profile and / or initiation profile is at least the kerf width of the cutting profile. The inspection position should have a minimum distance relative to the cutting profile so that the machining beam does not unintentionally irradiate the area of ​​the cutting profile completely or partially during inspection, which could distort the inspection results. If the cut portion is a remainder, the initiation profile necessary to initiate the cutting process typically extends from the insertion position into the remainder. A minimum distance should also be maintained relative to the initiation profile during inspection to avoid distorting the inspection results. Furthermore, the inspection position should be as close as possible to the cut end, i.e., as close as possible to the cut position, so that the distance between the cut position and the inspection position is as small as possible and inspection can be performed quickly. This minimum distance can also be chosen to be greater than the kerf width, for example, when the machining beam has a so-called pulse radius, within which the machining beam affects workpiece material outside the beam diameter, for example, in a way that the machining beam causes workpiece material to accumulate there. In this case, the minimum distance should be at least equivalent to the sum of the kerf width and the pulse radius.

[0037] In another aspect of the invention, or in a variation of the method described earlier for checking whether a portion of the workpiece has been completely separated from the remaining workpiece, which involves irradiating the workpiece with a machining beam at an inspection position within a pre-given cutting profile, if it is determined during inspection that the portion of the workpiece has not been completely separated from the remaining portion during cutting, a gas pulse is applied at least to the inspection position, or, if necessary, to any other position within the cutting profile, to expel the workpiece portion from the placement plane. The gas pulse is typically applied to the inspection position through a cutting gas nozzle of the machining head, through which the machining beam is also directed at the workpiece. Alternatively, one or more gas pulses generated by side gas nozzles may be applied obliquely to the inspection position. The gas pulses may have a duration on the order of several seconds, such as two seconds, and a high gas pressure, such as above 10 bar or 15 bar. The gas used to generate the gas pulses may, in particular, be an inert gas, such as nitrogen. "Blowing out" a portion of the workpiece via one or more gas pulses is non-destructive, meaning the edges of the workpiece portion or remaining workpiece are unaffected, and "blowing out" typically has less impact compared to re-cutting via a machining beam. After applying a gas pulse to the inspection position, the workpiece portion can be re-inspected at the same location to confirm whether it has been removed from the placement plane. If necessary, at least one gas pulse can be applied to another location within the cutting profile, especially if the probability of the workpiece portion being expelled is greater when the gas pulse is applied at that location than when it is applied at the inspection position.

[0038] In another variation, the method additionally includes: (re)checking whether the workpiece portion has completely separated from the remaining portion during the recutting process. In this case, the workpiece portion is rechecked for complete separation from the remaining workpiece after subsequent processing, or after the recutting process. If this recheck is performed by irradiating the workpiece with the processing beam, it can be performed at the same check position as the previous check, or it can be performed at a different check position. The latter is particularly advantageous when the processing beam affects the workpiece, for example, when the processing beam causes material buildup on the workpiece. In this case, the distance between the two check positions should be at least equivalent to the kerf width and, if necessary, additionally equivalent to the pulse radius. If it is determined during the recheck that the workpiece portion has not yet separated from the remaining portion, further subsequent processing can be performed, i.e., further cutting can be performed with a laterally staggered cutting profile, followed by further check steps, etc.

[0039] To avoid infinite loops, in the previously described scenario, an adjustable tolerance threshold can be pre-defined, which corresponds to a limited number of repetitions of the (re)cutting process. If the tolerance threshold is exceeded, the machine is switched to a pause mode, meaning the workpiece cutting process is suspended. Additionally or alternatively, further actions can be implemented, such as sending acoustic warnings and / or messages and / or real-time images and / or notifications of the machine's processing space to the machine operator's communication device. These further actions can occur at the first iteration stage, the final iteration stage (i.e., upon exceeding the tolerance threshold), or any intermediate iteration stage.

[0040] In addition to the inspection of the workpiece by the processing beam described earlier, it is also possible to use a grating, a light grid or similar object to check whether the cut part falls down from the workpiece plane. The grating is arranged below the workpiece plane and detects the fall of the cut part.

[0041] In another variation, during the cutting process, a cutting gas stream containing a first cutting gas, preferably a reactive gas, such as oxygen, is introduced into the workpiece. During the re-cutting process, a cutting gas stream containing a second cutting gas, preferably an inert cutting gas, such as nitrogen, is introduced into the workpiece. It has proven advantageous to use an inert gas during the re-cutting process because the gas pressure can typically be higher in this case compared to a reactive gas. Furthermore, there is no risk of thermal reaction with the workpiece material when using an inert gas.

[0042] In another variation, the distance between the machining head and the workpiece is increased during recutting. It has proven advantageous to increase the distance between the machining head, and especially the cutting gas nozzle located there, and the workpiece during recutting, as this improves the robustness of the cutting process. This is particularly meaningful for cutting processes where the cutting distance between the machining head and the workpiece is very small, such as when the cutting process has a split nozzle, where the cutting distance may be only 0.4 mm. Conversely, the distance between the machining head, or cutting gas nozzle, and the workpiece can be chosen to be relatively large during recutting, for example, approximately 3 mm.

[0043] In the extended scheme, the focal position of the processing beam is moved towards the workpiece direction as the distance is increased, so that the same focal position is used during recutting as during the initial cutting. For this purpose, the focal position is typically moved towards the workpiece by a distance corresponding to the increased distance between the processing head and the workpiece. By maintaining the focal position, a cutting kerf can be generated during recutting, the width of which is essentially the same as the kerf width during the initial cutting. Here, to allow the focal position to be moved towards the workpiece without changing the distance between the processing head and the workpiece, for example, a focusing device, such as a focusing lens, arranged in the processing head can be moved relative to the housing of the processing head.

[0044] Another aspect of the invention relates to a machine of the type described above for cutting workpieces, in which a control device is configured, or programmed, to manipulate at least one motion device to perform a recutting of the workpiece with a laterally offset cutting profile relative to a pre-given cutting profile if an analysis and evaluation device determines during inspection that a portion of the workpiece has not been completely separated from the remaining portion. The motion device manipulated by the control device can be a motion device for moving a processing head, typically a laser cutting head. Alternatively or additionally, a motion device can be manipulated by the control device to move the workpiece. The relative movement between the processing head and the workpiece is understood as movement in or parallel to a plane in which the workpiece, typically plate-shaped, is arranged. The laterally offset between the pre-given cutting profile and the laterally offset cutting profile also occurs within the workpiece plane.

[0045] In a further aspect of the invention, or in a further embodiment, the machine includes a detector for detecting radiation generated by the interaction between the machining beam and the workpiece, the radiation being produced when the preferably pulsed machining beam irradiates the workpiece at an inspection position within a pre-given cutting profile. An analysis and evaluation device is configured to check, by means of the detected radiation, whether a portion of the workpiece has completely separated from the remaining portion during the cutting process. A control device is configured to increase the intensity of the machining beam at the inspection position and to terminate irradiation of the machining beam onto the inspection position once it is determined during inspection that the portion of the workpiece has not completely separated from the remaining portion during the cutting process. As described earlier in connection with the method, even if the position of the workpiece portion relative to the remaining portion, or relative to the focal position of the machining beam, is not precisely known, it is possible to process-safely check whether the workpiece portion has completely separated from the remaining portion in this machine.

[0046] The control unit is configured to execute an NC (numerical control) machining program in which a pre-defined cutting contour for the portion to be cut is given to the workpiece. Here, communication between the control unit and other machine components, such as with the beam source, the distance adjustment device between the machining head and the workpiece, with the Human Machine Interface (HMI), and with a Programmable Logic Controller (PLC), is used to cut the pre-defined cutting contour with the cutting parameters determined for each pre-defined cutting contour. After cutting a portion or a cutting contour, a waiting time can be set in the NC machining program to allow the workpiece to cool before cutting other portions. The aforementioned checks can be performed, in particular, during this waiting time, which may be necessary.

[0047] In its simplest case, the detector can be a photodiode that senses or measures the intensity of radiation reflected from the workpiece. This radiation is typically process radiation, thermal radiation, and / or reflected or scattered processing beams, especially laser beams, generated when the processing beam interacts with the workpiece. For example, a detector in the form of a photodiode can be arranged, for instance, in a beam source used to generate the processing beam, such as a solid-state laser used to generate the laser beam. In particular, detecting laser beams reflected from the workpiece has proven advantageous because, in this case, the processing beam can irradiate with a significantly lower power compared to detecting process light or thermal radiation, so that the cut portion is not damaged during inspection. The latter is especially advantageous if the cut portion is intact.

[0048] In this embodiment, the machine has a beam source and the control device is configured or programmed to manipulate the beam source so that the power of the processing beam is progressively increased, particularly during irradiation of the inspection position. As described earlier in connection with the method, by changing the power of the beam source, the intensity of the processing beam at the inspection position can be rapidly increased continuously or progressively, so that the inspection duration does not need to be prolonged or is only slightly prolonged compared to inspection using constant power.

[0049] In another embodiment, the control device is configured to manipulate the beam source so that the processing beam pulses onto the inspection position, and the pulse power of the pulsed processing beam is gradually increased, wherein, preferably, the pulse power is at least doubled each time it is increased. When the power is doubled, a relatively small number of stages are needed to cover a large range of laser beam power values, thereby shortening the inspection time while ensuring that the duration of each pulse is the same. Instead of gradually increasing the power, the processing beam power can also be continuously increased, especially when using a "continuous wave" (CW) processing beam.

[0050] In another embodiment, the machine additionally includes a focusing device disposed in the machining head and another motion device for moving the machining head in a direction perpendicular to the workpiece. The control device is configured to manipulate the other motion device to increase the intensity of the machining beam at the inspection position, thereby moving the focal position of the machining beam toward the workpiece during the machining beam's illumination of the inspection position. The smaller the distance between the focal position of the machining beam and the workpiece, the smaller the diameter of the machining beam on the workpiece and the higher the intensity of the machining beam at the inspection position. Therefore, to increase the intensity of the machining beam at the inspection position, the distance between the focal position and the workpiece, or a portion thereof, can be continuously or, if necessary, progressively reduced. Instead of moving the machining head, the focal position can also be adjusted in other ways if necessary, for example, by moving the focusing device relative to the machining head.

[0051] In another embodiment, the analysis and evaluation device is configured to compare the intensity of detected radiation with an intensity threshold in order to check whether a workpiece portion has been completely separated from the remaining portion during the cutting process. As previously described, particularly when using a non-spatial-resolved detector, such as a photodiode, in the simplest case, the intensity of detected radiation can be compared with an intensity threshold. If it is below the intensity threshold, there is no workpiece material at the inspection location, and the NC cutting program continues to cut other workpiece portions. If the intensity value of the detected radiation is higher than the intensity threshold, it is considered that there is interfering workpiece material at the inspection location, causing the workpiece portion to not be completely separated from the remaining portion. In this case, ideally, the processing beam is terminated in real time and irradiated at the inspection location, as described in detail previously.

[0052] If a spatially resolved detector is used for inspection, instead of comparing with an intensity threshold, the detected radiation can be analyzed and evaluated using image recognition methods on workpiece images, such as those taken through the machining nozzle of the machining head. Analysis and evaluation using image recognition methods can be particularly well combined with the previously described continuous or stepwise changes in focus position, as this allows for the identification of workpiece portions that have sunk below the surface of the remaining portion. Attached Figure Description

[0053] Other advantages of the invention will become apparent from the specification and drawings. Similarly, the features described above and further listed can be used individually or in any combination. The illustrated and described embodiments should not be construed as an exhaustive enumeration, but rather as having several exemplary features for describing the invention.

[0054] The attached diagram shows:

[0055] Figure 1 A schematic diagram of an embodiment of a machine for cutting workpieces, in the form of a laser processing machine.

[0056] Figure 2 A schematic diagram of the cutting kerf formed in the workpiece during the cutting process.

[0057] Figure 3 A view formed in the workpiece during the cutting process, representing a pre-defined cutting profile used to separate the remaining portion from the workpiece.

[0058] Figure 4a 、b Figure 3 A schematic diagram of a pre-defined cutting contour and another cutting contour offset from the pre-defined cutting contour.

[0059] Figure 5 A schematic diagram of the laser beam distribution at the inspection location on the workpiece.

[0060] Figure 6 A schematic diagram showing the time trajectory of the power of the laser beam irradiating the inspection position and a schematic diagram showing the time trajectory of the IR radiation intensity detected when the irradiated laser beam interacts with the workpiece.

[0061] In the following description of the accompanying drawings, the same reference numerals are used for the same or functionally identical parts. Detailed Implementation

[0062] Figure 1An exemplary configuration of a machine 1 for laser processing, or more precisely, laser cutting, of a plate-shaped workpiece 2 (shown as dashed) using a laser beam 3 is shown. Other types of thermal processing beams may be used instead of the laser beam 3 for cutting the workpiece 2. During processing, the workpiece 2 is placed on two workpiece placement surfaces 4 and 5, which in the illustrated example form the upper sides of two workpiece stages and define a placement plane E (the XY plane of the XYZ coordinate system) for placing the workpiece 2.

[0063] The conventional motion and holding device 7 has a driver and a clamping device 8 in the form of a clamping block for fixing the workpiece 2. With the aid of this motion and holding device, the workpiece 2 can be controlled to move along a first motion direction X (hereinafter: X direction) on the workpiece placement surfaces 4, 5 and move to a predetermined workpiece position X. W .

[0064] A slit 6 is formed between two workpiece placement surfaces 4 and 5, extending along a second direction (Y direction below) along the entire travel path of a processing head in the form of a laser cutting head 9, which aligns and focuses a laser beam 3 onto the workpiece 2. The laser cutting head 9 can be controlled to move in the Y direction within the slit 6 by means of a driven slide 11, which is guided on a stationary gantry 10. In the example shown, the laser cutting head 9 can also be additionally controlled to travel in the X direction within the slit 6 by means of an additional motion device 12, for example, in the form of a linear actuator, mounted on the slide 11. By means of the motion devices 11 and 12 built on each other, the laser cutting head 9 can be positioned not only in the X direction but also in the Y direction at a desired cutting head position X within the slit 6. S Y S Above. Two support slides 13a and 13b are arranged within the gap 6, which extend across the entire width of the gap 6 and can move in a controlled manner and independently within the gap 6 along the Y direction.

[0065] Additionally, in the illustrated example, the laser cutting head 9 can be moved along a third motion direction Z (the direction of gravity, hereinafter: Z direction) by means of another motion device 13 constructed on a first motion device in the form of a slide 11, in order to adjust the distance between the processing nozzle 9a of the laser cutting head 9 and the surface of the workpiece 2, or in other words, to position the laser cutting head 9 at the desired cutting head position Z. S It is positioned at the desired distance along the Z direction relative to the workpiece placement plane E.

[0066] Support slides 13a and 13b can move along the Y direction within the gap 6 to the desired position Y, respectively. UA Y UBThe workpiece 2 is supported there by means of support surfaces 14a and 14b arranged on the corresponding support slides 13a and 13b, or more precisely, by supporting the workpiece portion 17 cut from or during machining from the workpiece 2. In the case shown, the support surfaces 14a and 14b of the corresponding support slides 13a and 13b terminate flush with the workpiece placement surfaces 4 and 5 in the z-direction, that is, the support surfaces 14a and 14b are located in the placement plane E for the workpiece 2.

[0067] To control the cutting process, machine 1 has a control device 15 for coordinating the movement of workpiece 2, the movement of the laser cutting head, and the movement of the support slides 13a and 13b, so as to adjust the desired workpiece position X. W Expected cutting head position X S Y S Z S And the desired positions Y of the support slides 13a and 13b UA Y UB This allows for cutting along a pre-defined cutting contour 18a and, if necessary, supports the workpiece in the area of ​​the slit 6. The movement of the first support slide 13a can be synchronized with the second support slide 13b, or it can be performed independently. The control device 15 is also used to manipulate the beam source 31, which is in the form of a laser source.

[0068] exist Figure 1 In the illustrated embodiment, covering elements 16a and 16b are respectively disposed on the mutually opposing outer edges extending in the X direction of the support surfaces 14a and 14b, for covering the gap 6 outside the cut area formed between the support slides 13a and 13b. The covering elements 16a and 16b extend over the entire width b of the gap 6 and move together in the Y direction when the support slides 13a and 13b move.

[0069] When workpiece portion 17 is cut from workpiece 2, or more precisely from the remaining portion of workpiece 2 in the form of the remaining grid 19, the final connection between workpiece portion 17 and the remaining grid 19 is separated at the cut-out position FP. For this purpose, the two support slides 13a, 13b can travel together more closely, such that only a very small distance or no distance is maintained between them in the Y direction.

[0070] Figure 2 A cross-sectional view is shown. Figure 1 The details of workpiece 2 are shown in this cross-sectional view, illustrating a cutting kerf 26 with a kerf width B, formed in workpiece 2 along a pre-defined cutting profile 18a. The kerf width B of the cutting kerf 26 is determined by process parameters such as cutting gas pressure, feed rate, and laser power. As long as... Figure 1The cutting process shown is performed correctly, and the workpiece portion 17 is completely separated from the remaining portion 19 at the cut position FP along the pre-given cutting contour 18a. The workpiece portion 17 is then removed from the workpiece plane E, for example, by moving the two support slides 13a, 13b in opposite directions in the slit 6, so that the workpiece portion 17 is no longer supported and falls downward into the slit 6, in which the workpiece portion 17 can be discharged from the machine 1 by means of a device not described in detail.

[0071] To check whether workpiece portion 17 actually separates from remaining portion 19 during the cutting process, an inspection, or check step, is performed, which is then carried out using... Figure 3 Detailed description. Figure 3 The top view of workpiece 2 is shown, showing a workpiece portion 17 separated from (remaining) workpiece 2, which is different from... Figure 1 As shown, a circular remainder 19 is cut from the workpiece portion 17 to create an opening in the workpiece portion 17 for securing bolts or the like. In this example, the cut profile 18a is circular, but obviously, the geometry of the cut profile 18a can be arbitrary in principle. Figure 3 The diagram also shows the insertion point 20a and the linear starting contour 20b, which are used for insertion and initiation of the laser beam 3 before separating the remaining portion 19 from the workpiece portion 17 along a pre-given cutting contour. The machining direction 23a of the pre-given cutting contour 18a is... Figure 3 For example, it extends in a clockwise direction.

[0072] To check whether the remaining portion 19 has completely separated from the workpiece portion 17 and thus fallen downwards from the workpiece plane E, the laser cutting head 9 is positioned by means of two motion devices 11, 12 and / or the workpiece 2 by means of a motion device and a holding device 7, such that the laser beam 3 for processing is oriented substantially perpendicular to the surface of the workpiece 2 and irradiates the remaining portion 19 at the inspection position, wherein, in Figure 3 Two possible inspection locations 21a and 21b are illustrated exemplarily. If there are incompletely separated portions at inspection locations 21a and 21b, for example... Figure 3 The remaining portion 19 shown in the diagram interacts with the laser beam 3, thereby generating radiation 27, which in... Figure 3 The first inspection position 21a is shown as an example.

[0073] Two in Figure 3The inspection positions 21a and 21b shown are located at a distance A1 from the starting contour 20b, which is at least equivalent to the kerf width B. Similarly, the inspection positions 21a and 21b are at least 1 mm away from the pre-given cutting contour 18a at a distance A2, which is at least equivalent to the kerf width B, to prevent measurement distortion due to a portion of the laser beam 3 irradiating into the kerf 26 or the starting contour 20b. For rapid inspection, it is advantageous that the inspection positions 21a and 21b are not too far from the cut position FP. In cases where the laser beam 3 affects the material of the workpiece 2, the two inspection positions 21a and 21b should be similarly arranged at least at a distance from each other that is at least equivalent to the kerf width B. In cases where the laser beam 3 has a pulse radius (in which case the laser beam affects the material of the workpiece 2 outside the beam diameter, for example, through material spatter), the pulse radius should be taken into account when determining the respective distances A1 and A2, typically by increasing each distance A1 and A2 by one pulse radius.

[0074] As shown in DE 10 2011 004 117 A1 cited at the beginning, the radiation 27 generated when interacting with the laser beam 3 is detected by a detector 22, for example, in the form of a photodiode (see reference). Figure 1 The radiation can be sensed as process-generated emission, thermal radiation due to the heating of workpiece 2, and / or reflected laser beams. If Figure 3 The remaining part 19 or Figure 1 If the workpiece portion 17 has been completely cut out, then the detector 22 will not detect, or will only detect, the low intensity of radiation 27 generated during the interaction. Analysis and evaluation device 28 (refer to...) Figure 1 The detected radiation 27 is used to check whether parts 17 and 19 have fallen downwards from the workpiece plane E. For this check, the intensity of the detected radiation 27 can be compared with an intensity threshold, for example. If the intensity of the detected radiation 27 is below the intensity threshold, it can be assumed that parts 17 and 19 have fallen downwards from the workpiece plane E, so that there is actually no interaction between the laser beam 3 and parts 17 and 19 at the inspection positions 21a and 21b.

[0075] If, during inspection, it is determined that part 17 of the workpiece is not completely separated from the remaining part 19, recutting can be performed directly, as described in detail below. If necessary, the workpiece part 17 can be checked again to ensure it is completely separated from the remaining part 19 before recutting; that is, the inspection steps can be repeated as described above, typically by changing the inspection location. In this case, recutting is only performed if both inspection steps determine that part 17 is not completely separated from the remaining part 19.

[0076] As in Figure 4a b and Figure 2 As can be seen, the recutting process is performed along another cutting contour 18b, which is laterally offset relative to the pre-given cutting contour 18a, or more precisely, in the example shown, offset by a constant amount V towards the remaining portion 19. Figure 4a and Figure 4b The difference in the examples shown is that, in Figure 4a In the middle Figure 3 The remaining part 19 is circular, as in the example. Figure 4b The middle portion 17 is circular and cut out from the remaining portion 19, which in this case forms the remaining grid of workpiece 2. For example... Figure 3 The example shown is the same, in Figure 4b In the example shown, the insertion point 20a and the starting profile 20b are formed in the remaining portion 19. Figure 4b In the example shown, the check positions 21a and 21b are also selected within the closed cutting contour 18a, that is, within the good part of the circle 17.

[0077] exist Figure 4a In the example shown, another cut profile 18b is offset radially inward toward the remaining portion 19, while... Figure 4b In the example shown, the other cutting profile 18b is offset radially outward toward the remaining grid 19. The amount V by which the other cutting profile 18b is offset is chosen such that the machining beam 3 falling on the workpiece 2 to cut the other cutting profile 18b does not touch the edge 25 of the workpiece portion 17 (the good portion) or only... Figure 2 The edge 25 of the workpiece portion 17 is touched at the outer edge of the intensity I distribution (Gaussian distribution) shown in the diagram, so that the edge 25 is not damaged by the laser beam 3 during recutting. Here, the lateral offset amount V can be chosen such that the laser beam 3 falls on the edge 25 of the workpiece portion with intensity I along another cutting contour 18b during the cutting process, and this intensity is less than the laser beam 3's relative to the laser beam 3's... Figure 2 The maximum intensity I of the beam distribution extending radially symmetrically along the beam axis is shown in the figure. MAX (Refer to Figure 2 The lateral offset V can be 50%, preferably less than 30%, and especially less than 20%. In particular, the lateral offset V can be greater than about 2% or 5% of the kerf width B of the pre-given cutting profile 18a.

[0078] Furthermore, the offset amount V is typically chosen such that it is less than the kerf width B of the kerf 26 along the pre-given cutting profile 18a. It should be understood that, unlike... Figure 4aAs shown in Figures 1 and 2, the offset amount V is not forced to be constant, but can vary along another cutting profile 18b. Figure 4a As shown in Figures 1 and 2, another cutting contour 18b is completed along a machining direction 23b opposite to that of the pre-given cutting contour 18b. Alternatively, the machining direction of the pre-given cutting contour 18a corresponds to the machining direction of the other cutting contour 18b, such that the two cutting contours 18a and 28b are cut in a clockwise direction. If necessary, the other cutting contour 18b is not required to extend along the entire length of the pre-given cutting contour 18a; instead, the other cutting contour 18b may extend only along a segment 29 of the pre-given cutting contour 18a, such as in... Figure 4b As shown in the image.

[0079] exist Figure 2 As can be seen, a cutting gas beam 33 is used during the cutting process along the pre-defined cutting contour 18a. This cutting gas beam is ejected from the processing nozzle 9a of the laser cutting head 9 in the direction toward the workpiece 2. In the example shown, the process is a combustion cutting process, meaning that the cutting gas beam 33 consists of a reactive gas, or in other words, the cutting gas beam 33 contains a reactive gas, which in the example shown is oxygen (O2). The cutting gas beam 33 is also used for the recutting process along another laterally offset cutting contour 18b; however, in this case, an inert cutting gas in the form of nitrogen (N2) is used. The use of an inert cutting gas for the recutting process along another cutting contour 18b has proven advantageous because, on the one hand, a higher gas pressure can be used compared to the reactive gas case, and on the other hand, the risk of thermal reaction with the workpiece material is reduced by using the inert cutting gas N2.

[0080] Instead of recutting the workpiece 2 along a laterally offset cutting profile 18b using the processing gas beam 3, the cutting gas beam 33 can be used to track a pre-given cutting profile 18a, or, if necessary, another laterally offset profile 18b whose orientation corresponds to the aforementioned other cutting profile 18b, in which case the processing gas beam 3 is not activated. When tracking the pre-given cutting profile 18a or the other profile 18b, gas pressure is applied to the workpiece portion 17 by the cutting gas to press and expel the workpiece portion 17 downwards from the placement plane E. Typically, when tracking the corresponding profiles 18a and 18b with the cutting gas beam 33, only the slightly tilted workpiece portion 17 in the remaining portion 19 can fall; that is, recutting with the processing gas beam 3 is more effective than tracking the cutting profile 18a or the other profile 18b with the cutting gas beam 33. However, using the cutting gas beam 33 is non-destructive, meaning it does not affect, and in particular, damage, the cutting edges of the remaining portion 19 or the workpiece portion 17.

[0081] After recutting along another cutting contour 18b using the cutting gas beam 33, or following a pre-given cutting contour 18a or another laterally offset contour 18b, a further inspection can be performed to check whether the workpiece has completely separated from the remaining portion 19. This re-inspection can be performed in the manner described above, but can also be performed and re-inspected as necessary by other sensing devices, such as those in the form of gratings, positioned below the workpiece plane E and detecting the fall of portions 17, 19. If, during the re-inspection, it is found that portions 17, 19 have not been completely cut out, recutting can be performed, followed by another inspection step. It is understood that to avoid infinite loops, a stop criterion should be set so that machine 1 pauses after a pre-given number of repeated cutting operations and inspections.

[0082] Figure 5 The beam distribution of the laser beam 3 is shown, which is focused onto the workpiece 2 by a focusing device 32 (focusing lens) arranged in the processing head 9. Figure 5 In the example shown, the position Z of the machining head 9 in the Z direction is selected in this way. S Therefore, the distance A between the machining head 9 and the workpiece 2 is selected in this way, so that the focal position Z F Located precisely on the surface of workpiece 2, this focal point (arbitrarily) coincides with the origin of the Z-axis coordinate system in the example shown. F =0). Laser beam 3 at focal position Z F The beam has its beam waist, or its minimum beam diameter d, which in the example shown is approximately d = 150 μm. For the laser beam 3 at the focal position Z... F The radius R around the object along the Z direction is well approximated:

[0083]

[0084] Among them, Z R The Rayleigh length of the laser beam 3 is indicated. This Rayleigh length depends primarily on the wavelength of the laser beam 3 and is approximately 1.0 mm in the example shown. In the example shown, the workpiece 2 is formed of steel, such as structural steel or high-quality steel. If we assume that the thickness D of the workpiece 2 is, for example, D = 6 mm, then the cross-sectional area of ​​the laser beam 3 on the lower side of the workpiece 2 is equal to the area on the upper side, that is, at the focal position Z in the example shown. F The cross-sectional area of ​​the laser beam 3 is 37 times larger than that of the workpiece 2. When the incompletely cut workpiece portion 16 sinks to a horizontal height near the lower side of the workpiece 2, the cross-sectional area of ​​the laser beam 3 increases by this factor, and the intensity I of the laser beam falling on the workpiece portion 17 is increased. P Accordingly, it was reduced to 1 / 37.

[0085] Therefore, if the laser beam 3 irradiates the workpiece 2 with a relatively low power P, there is a risk that the workpiece portion 17, which is sinking downwards but still connected to the remaining portion 19, cannot be detected due to the minimal interaction between the laser beam 3 and the workpiece portion 17, and thus a collision with the sinking workpiece portion 17 occurs as the process continues. Conversely, if the laser beam 3 irradiates the workpiece 2 with a relatively high power P, burn marks may be left in the workpiece portion 17 located at the height of the upper side of the workpiece 2, typically accompanied by a large amount of spark spatter. Spark spatter can cause contamination of the machine, for example, resulting in splashes on the protective glass set on the processing head 9.

[0086] Furthermore, if workpiece 2 is relatively thin, it may be pierced by the laser beam 3. This piercing of workpiece 2 or workpiece component 17 means that, after recutting, a valid inspection cannot be performed again at least at the same inspection position 21a, because in such an inspection, material interaction with workpiece component 17 may no longer occur, even if that component remains connected to the remaining component 19. Therefore, there is a risk that workpiece component 17, still connected to the remaining component 19, may not be identified in this situation, potentially leading to undesirable collisions as the process continues.

[0087] Therefore, if a constant power P is used for inspection with the laser beam 3, this constant power must be large enough that the portion of the workpiece sinking to the vicinity of the lower side of the workpiece 2 is still just identified, but on the other hand, the power P cannot be large enough to burn marks in the portion 17 of the workpiece located on the upper side of the workpiece 2. When the workpiece 2 is relatively thick, these conditions usually cannot be met by the same power P.

[0088] In order to perform robust inspection despite the uncertain position of workpiece portion 17 relative to the remaining portion 19, in the example shown, the power P of the pulsed laser beam 3 is gradually increased during inspection, as exemplarily in Figure 6 As shown in the lower part. Figure 6 The diagram shows the power P, or more precisely, the average power, of a laser beam 3 pulsed with five consecutive pulses P1 to P5. In the example shown, the average power of the laser beam 3 pulses P1 to P5 doubles with each pulse, meaning the first pulse P1 has an average power of 100 W, the second pulse P2 has an average power of 200 W, the third pulse P3 has an average power of 400 W, the fourth pulse P4 has an average power of 800 W, and the fifth pulse P5 has an average power of 1600 W. The duration of each pulse P1 to P5, or each stage, can be on the order of milliseconds, making it possible to... Figure 6 The entire pulse sequence shown, and thus the total duration of the entire examination, does not exceed, for example, about 20 ms.

[0089] As mentioned above, during the process of irradiating the workpiece 2 with the laser beam 3, the intensity I of the detected radiation 27, for example in the infrared wavelength range, is detected by the detector 22. IR The intensity I of the detected radiation 27 IR During the inspection, the intensity threshold I remained constant. IR，S Comparison, such as in Figure 6 The middle part is shown at the top. For the detected beam 27 intensity I... IR Exceeding the intensity threshold I IR In this case, the irradiation of the laser beam 3 onto the workpiece 2 is ideally terminated in real time. To say that the irradiation is terminated in real time, the control device 15 influences the beam source 31 through a real-time interface to shut down the laser beam 3.

[0090] By rapidly shutting off the laser beam 3, only the power P required to check whether workpiece portion 17 has completely separated from the remaining portion 19 is applied to workpiece 2, or workpiece portion 17. This method prevents unwanted burn marks from forming or workpiece 2 from being penetrated by the laser beam 3. Figure 6 In the example shown, the intensity threshold I was exceeded during the second pulse P2. IR，S Therefore, the pulse sequence terminates after the second pulse P2 and the third, fourth and fifth pulses P3, P4 and P5 of the pulse sequence are no longer implemented.

[0091] Alternative Figure 6 The progressively increasing power P of the laser beam 3 shown can also be performed by continuously increasing the power P of the laser beam 3. In particular, a continuous laser beam 3 can be used instead of a pulsed laser beam, the power of which is increased to the maximum power in a ramp or similar manner during the inspection duration.

[0092] Alternatives Figure 6 The power P of the laser beam 3 is increased during the inspection interval, and the intensity I at the inspection position 21a is increased. P This can also be improved by changing the distance A between the processing head 9 and the workpiece 2 continuously or gradually during the laser beam 3 irradiation, typically decreasing. In this case, the processing head 9 is positioned at a distance A relative to the workpiece 2 at the beginning of the inspection interval, for example, at this distance, the focal position Z. F Located above the upper side of workpiece 2. Then, decrease the distance A between the machining head 9 and workpiece 2 until the focal point position Z. F Located on the upper side of workpiece 2, at a position between the upper and lower sides of workpiece 2, or on the lower side of workpiece 2.

[0093] At the focal position Z of the moving laser beam 3 FTo increase the intensity of the laser beam 3 at inspection position 21a P When the intensity threshold I is exceeded IR，S This also terminates the irradiation of the laser beam 3 at the inspection position 21a, thus avoiding excessive interaction with the workpiece 2, which could lead to burn marks or penetration of the workpiece 2. Furthermore, by increasing the power P of the laser beam 3 or decreasing the focal diameter on the workpiece 2 during the inspection process, robustness against fluctuations in the material surface properties of the workpiece 2 and against offset of the focal position relative to the workpiece 2 can be improved. The method described here is to increase the intensity I at the inspection position 21a during inspection. P This method can be advantageously combined with the previously described method of recutting the workpiece 2 along another cutting contour 18b that is laterally offset relative to the pre-given cutting contour 18a. Alternatively, this method can be performed without laterally offsetting the cutting contour 18a during the recutting process if necessary.

[0094] Whether to increase the intensity at inspection location 21a during inspection I P Regardless, the distance A between the laser cutting head 9 and the workpiece 2 can be increased during recutting to improve the robustness or safety of the cutting process. This has proven particularly advantageous when using a split nozzle for cutting, where the distance A between the laser cutting head 9, or nozzle 9a, and the workpiece 2 is very small, for example, only about 0.4 mm. For recutting, the distance A can be increased to, for example, 3 mm.

[0095] In order to maintain the focal position Z relative to workpiece 2 despite increasing the distance A. F With a constant distance A, the focal position Z moves towards workpiece 2. F For this purpose, for example, the focusing device in the laser cutting head 9, which takes the form of a focusing lens 32, can be moved, such as in... Figure 5 The double arrows indicate this. This ensures that the recutting process is performed with essentially the same kerf width B, and the cutting process is also performed with that kerf width B.

[0096] Regardless of whether the strength IP at inspection position 21a is increased during inspection, if it is found during inspection that workpiece portion 17 has not completely separated from the remaining portion 19, instead of re-cutting, an attempt can be made to expel workpiece portion 17 downward from the placement plane E by applying a gas pulse 33a (see reference). Figure 5The gas pulse 33a is applied to inspection position 21. It typically has a high gas pressure, for example, approximately 15 bar. For this purpose, an inert gas, such as nitrogen, is usually used as the (cutting) gas. The duration of the gas pulse can be on the order of one second or, if necessary, several seconds. As described earlier when tracking the cutting profile 18a or another profile 18b with the cutting gas beam 33, the application of the gas pulse 33a is also non-destructive, meaning it has no effect on the quality of the cut edges. However, the effect of applying the gas pulse 33a to expel the workpiece portion 17 from the placement plane E is less significant compared to the case when re-cutting by the laser beam 3. Therefore, it is advisable to first attempt to expel the workpiece portion 17 by applying the gas beam 33a. If, upon re-inspection, it is determined that the workpiece portion 17 is still within the placement plane E, re-cutting can be performed.

[0097] It should be understood that although the method for inspecting the cutting process described above is in conjunction with laser cutting machine 1, the method can also be performed on other machines, such as on a machine that combines stamping and laser cutting functions.

Claims

1. A method for cutting and processing workpiece (2), comprising: The workpiece (2) is cut along a pre-defined cutting contour (18a) to separate the workpiece portion (17) from the remaining portion (19), and Check whether the workpiece portion (17) is completely separated from the remaining portion (19) during the cutting process. It was determined that the workpiece portion (17) had not completely separated from the remaining portion (19). The process of checking whether the workpiece portion (17) is separated from the remaining portion (19) includes the following steps: The machining beam (3) is used to irradiate the workpiece (2) at inspection positions (21a, 21b) within the pre-defined cutting profile (18a). Detecting the radiation (27) generated by the interaction between the processing beam (3) and the workpiece (2), and The detected radiation (27) is analyzed and evaluated to check whether the workpiece portion (17) has been completely separated from the remaining portion (19) during the cutting process. Its features are, The intensity (I) of the processing beam (3) at the inspection positions (21a, 21b) is gradually increased during the irradiation of the processing beam (3). P Furthermore, once it is determined during inspection that the workpiece portion (17) has not been completely separated from the remaining portion (19) during the cutting process, the irradiation of the processing beam (3) is terminated.

2. The method according to claim 1, wherein the power (P) of the processing beam (3) is increased during irradiation of the inspection positions (21a, 21b).

3. The method according to claim 2, wherein the processing beam (3) is pulsed onto the inspection positions (21a, 21b) and the power of the pulses (P1 to P5) is increased stepwise.

4. The method according to claim 3, wherein the power of the pulses (P1 to P5) is at least doubled as each pulse is increased.

5. The method according to any one of claims 1 to 4, wherein the intensity (I) of the processing beam (3) at the inspection positions (21a, 21b) is... P The focal position (Z) of the machining beam (3) is moved toward the workpiece (2). F To improve.

6. The method according to any one of claims 1 to 4, wherein, in order to check whether the workpiece portion (17) has been completely separated from the remaining portion (19) during the cutting process, the detected radiation (27) intensity (I) is measured. IR ) and intensity threshold (I IR，S ) comparison, and once the intensity threshold (I) is exceeded IR，S Then the irradiation of the processing beam (3) will be terminated.

7. The method according to any one of claims 1 to 4, wherein the processing beam (3) is irradiated onto an inspection position (21a, 21b) within a pre-given cutting profile (18a), the inspection position being at least at a distance from the pre-given cutting profile (18a) and / or from the starting profile (20b) equal to the cutting kerf width (B) of the cutting profile (18a).

8. The method according to any one of claims 1 to 4, further comprising: If it is determined during inspection that the workpiece portion (17) was not completely separated from the remaining portion (19) during the cutting process, a gas pulse (33a) is applied to the inspection position (21a, 21b) to expel the workpiece portion (17) from the placement plane (E).

9. A machine (1) for cutting and processing workpieces (2), comprising: A processing head (9) is used to align the processing beam (3) with the workpiece (2). At least one motion device (7, 11, 12) is used to generate relative motion between the processing head (9) and the workpiece (2). as well as A control device (15) is used to manipulate the at least one motion device (7, 11, 12) to separate the workpiece portion (17) from the remaining portion (19) by cutting the workpiece (2) along a pre-given cutting profile (18a). An analysis and evaluation device (28) is configured to check whether the workpiece portion (17) is completely separated from the remaining portion (19) during the cutting process. The machine also includes: A detector (22) is used to detect radiation (27) generated by the interaction between the processing beam (3) and the workpiece (2), the radiation being generated when the processing beam (3) irradiates the workpiece (2) at inspection positions (21a, 21b) within a pre-given cutting profile (18a). The analysis and evaluation device (28) is configured to check, by means of detected radiation (27), whether the workpiece portion (17) is completely separated from the remaining portion (19) during the cutting process, wherein The control device (15) is configured to progressively increase the intensity (I) of the processing beam (3) at the inspection positions (21a, 21b) during irradiation by the processing beam (3). P Furthermore, once it is determined during inspection that the workpiece portion (17) was not completely separated from the remaining portion (19) during the cutting process, the irradiation of the processing beam (3) on the inspection positions (21a, 21b) is terminated.

10. The machine according to claim 9, having a beam source (31) and having a control device (15) configured therein, the control device manipulating the beam source (31) to increase the power (P) of the processing beam (3) during irradiation of the inspection positions (21a, 21b).

11. The machine according to claim 10, wherein the control device (15) is configured to manipulate the beam source (31) to pulse the processing beam (3) onto the inspection positions (21a, 21b) and progressively increase the power of the pulses (P1 to P5) of the pulsed processing beam (3).

12. The machine according to any one of claims 9 to 11, further comprising: A focusing device (32) is disposed in the processing head (9), and another motion device (30) is used to move the processing head (9) in a direction (Z) perpendicular to the workpiece (2), wherein the control device (15) is configured to increase the intensity (I) of the processing beam (3) at the inspection positions (21a, 21b). P The other motion device (30) is manipulated to adjust the focal position (Z) of the processing beam (3) at the inspection positions (21a, 21b) during the period when the processing beam (3) irradiates the inspection positions (21a, 21b). F ) moves toward the workpiece (2).

13. The machine according to any one of claims 9 to 11, wherein the analysis and evaluation device (28) is configured to, in order to check whether the workpiece portion (17) is completely separated from the remaining portion (19) during the cutting process, measure the intensity (I) of the detected radiation (27). IR ) and intensity threshold (I IR，S )Compare.

14. The machine according to claim 9, wherein the processing beam (3) is a pulsed processing beam.

15. The machine according to claim 10, wherein the control device (15) manipulates the beam source (31) to gradually increase the power (P) of the processing beam (3) during irradiation of the inspection positions (21a, 21b).

16. The machine according to claim 11, wherein the power of the pulses (P1 to P5) is at least doubled each time the power is increased step by step.

Images