Laser machining system and method for machining workpiece

Abstract

The invention relates to a laser machining system for machining a workpiece by means of a laser beam, comprising: a laser machining head having at least one focusing optics for focusing the laser beam such that the workpiece is heated and a process emission occurs; at least four optical sensors wherein the optical sensors are insensitive to radiation having a wavelength of the laser beam, and wherein the optical sensors are each arranged to detect the process emission in at least one wavelength range not including the wavelength of the laser beam and to generate a corresponding sensor signal based thereon; and a control device, the control device being arranged to monitor the machining of the workpiece on the basis of an average value of the sensor signals.

Description

Technical Field

[0001] This invention relates to a laser processing system and a method for processing workpieces, particularly for inserting into and / or cutting workpieces. Background Technology

[0002] To process a workpiece, especially to cut it, a laser beam is directed onto its surface. The laser beam intensely heats an area of ​​the workpiece, causing a portion to melt or evaporate. To cut the workpiece, the laser beam is directed onto an area until it penetrates the workpiece, creating a hole through which the laser beam can pass. The laser beam then travels along a path on the workpiece, creating a cut. During processing, particularly through the heating of the workpiece, process emission occurs. Process emission can include radiation in the visible wavelength range. The laser processing process can be monitored based on process emission.

[0003] DE 196 44 101 C1 relates to a method for identifying beam penetration during laser beam processing of a workpiece, wherein the intensity of radiation from the processing area is detected by at least one sensor, and a state signal is generated at a predetermined intensity change, wherein at least two average values ​​of the detected radiation intensity are formed for different time constants, and the state signal is generated when these average values ​​are in a predetermined ratio between each other.

[0004] Comparing measurements at two different time points means that process monitoring can only be performed with time offset. Summary of the Invention

[0005] The objective of this invention is to provide a laser processing system and method that enables process monitoring with small time offsets, particularly in real-time or instantaneously. Another objective is to provide a laser processing system and method that improves the accuracy of process monitoring. A further objective is to provide a laser processing system and method that offers the possibility of monitoring the laser processing process using a laser beam with a processing laser wavelength of less than 1200 nm, resulting in a simple structure and / or space-saving design.

[0006] At least the aforementioned tasks are solved by the laser processing system and method for processing workpieces using a laser beam according to the present invention. Preferred embodiments are defined below.

[0007] A laser processing system for machining a workpiece using a laser beam is disclosed. The laser processing system includes a laser processing head having at least one focusing optics for focusing the laser beam onto the workpiece, causing the workpiece to be heated and emitting process emissions. The laser processing system also includes at least four optical sensors. These optical sensors are insensitive to radiation having the wavelength of the laser beam. These optical sensors are configured to detect the process emissions within at least one wavelength range that does not contain the wavelength of the laser beam, and generate corresponding sensor signals based thereon. The laser processing system also includes a control device. The control device is configured to monitor the machining of the workpiece based on the average value of these sensor signals.

[0008] A method for machining, particularly penetrating and / or cutting, a workpiece using a laser beam is disclosed. The method includes the steps of: irradiating the workpiece with a laser beam, causing the workpiece to heat and emit process radiation; detecting the process radiation using at least four optical sensors in at least one wavelength range that does not contain the laser beam wavelength, and generating corresponding sensor signals based thereon, wherein these optical sensors are insensitive to radiation having the laser beam wavelength; and monitoring the machining of the workpiece based on the average value of these sensor signals. This monitoring can be performed using a control device. The monitoring may include adjusting and / or controlling the machining process based on the average value.

[0009] Each method disclosed herein can be performed using each of the laser processing systems disclosed herein. In particular, the control device can be configured to calculate the average value of these sensor signals and / or monitor the processing of the workpiece based on that average value.

[0010] Each laser processing system disclosed herein can be used in each of the methods disclosed herein.

[0011] According to the present invention, the sensor signals from these optical sensors are averaged. Therefore, this average can also be referred to as a common average. This average can be formed at a specific point in time, especially instantaneously. By using multiple sensors that are insensitive to the laser wavelength and averaging the sensor signals, the processing can be monitored with almost no delay. This is particularly applicable when the signal-to-noise ratio is relatively low. Signal noise is typically statistical, thus producing a smoother baseline during averaging, and improving the signal-to-noise ratio. This, in turn, improves the accuracy of monitoring.

[0012] Furthermore, process monitoring using fiber lasers can be implemented or improved. Fiber lasers typically have laser wavelengths slightly above 1000 nm, particularly between 1070 nm and 1090 nm. Previously, silicon-containing sensors were frequently used for process monitoring. These sensors have a wavelength sensitivity range of approximately 190 nm to 1100 nm. Therefore, silicon sensors are sensitive to the wavelengths of fiber lasers, and the measured signal may contain a large proportion of laser light.

[0013] Processing a workpiece using a laser beam can involve inserting, penetrating, and / or cutting or including the workpiece. Similarly, the process can be welding or brazing. Here, at least two workpieces can be welded.

[0014] The workpiece may be a metal workpiece, or may be composed of or contain metal.

[0015] Process emission occurs when a workpiece is heated using a laser beam. Process emission can include radiation in the visible wavelength range, specifically between 350 nm and 850 nm, or between 390 nm and 850 nm, or between 380 nm and 800 nm, such as the radiation from plasma generated during processing. Process emission can also include radiation in the infrared wavelength range, particularly thermal radiation. Process emission may contain a component with the wavelength of the laser radiation. This component of process emission cannot be detected by these optical sensors.

[0016] Furthermore, the radiation from the laser beam may be backscattered or reflected by the workpiece and enter the laser processing head. This backscattered or reflected radiation will not be detected by these optical sensors.

[0017] Process emission can originate from the workpiece and radiate toward the laser processing head, particularly toward the at least four optical sensors. For example, process emission can enter the laser processing head, particularly through an exit or nozzle opening for the laser beam to be directed toward the workpiece.

[0018] These optical sensors (also called photoelectric sensors, or simply sensors) can be sensitive to a defined wavelength range or multiple defined wavelength ranges. In particular, these sensors can be sensitive to at least one defined continuous or coherent wavelength range. When radiation falls on the photosensitive surface of the sensor within this wavelength range or these wavelength ranges, a measurement signal can be generated.

[0019] These optical sensors are insensitive to the wavelength of laser radiation. "Insensitive" can mean that radiation at wavelengths to which the optical sensor is insensitive is not detected or is barely detected, or produces no or only a weak measurement signal when the radiation strikes the optical sensor. This weak measurement signal can be at least an order of magnitude (10 times), preferably at least two orders of magnitude (100 times), smaller than the measurement signal of radiation at the wavelength to which the sensor is most sensitive. In other words, the measurement signal of the sensor for radiation at insensitive wavelengths can be at most 0.1 or at most 0.01 times the measurement signal of radiation at the wavelength to which it is most sensitive.

[0020] By making the sensor insensitive to radiation with the wavelength of the laser beam, laser radiation backscattered or reflected from the workpiece, as well as laser radiation diffusely scattered in the cutting head, is shielded by the sensor. In this way, high-intensity reflections or diffusely scattered laser radiation in the cutting head can prevent process emissions with the wavelength of the laser beam and / or process emissions in wavelength ranges outside the laser beam wavelength from being masked.

[0021] Each of the four optical sensors generates a measurement signal when the process emission illuminates its corresponding photosensitive surface. Therefore, four independent measurement signals can be generated by these four optical sensors. These optical sensors can be configured to simultaneously detect the process emission and / or simultaneously generate corresponding sensor signals. The measurement signal or sensor signal can correspond to the intensity of the detected process emission, particularly a time-series curve of the intensity. For example, the measurement signal or sensor signal of the corresponding sensor can correspond to the process emission intensity across the entire wavelength range or multiple wavelength ranges that the sensor is sensitive to.

[0022] The sensor signals from at least four optical sensors are averaged. In particular, to calculate the average value of the sensor signals, the signal values ​​of the sensor signals from the optical sensors detected at the same time point are used.

[0023] To calculate the average, the sensor signals or their values ​​(also called sensor values) can be summed and divided by the number of sensor signals or values ​​added. For four optical sensors, each generating one sensor signal, there are a total of four sensor values ​​at a given time point. This average can be an arithmetic mean.

[0024] Averaging can be achieved by connecting sensors in parallel. In particular, all optical sensors can be connected in parallel. Parallel sensors generate a (summed) sensor signal. This (summed) sensor signal can be understood as the average of the sensor signals. Therefore, averaging can be obtained without subsequent calculations. In this (summed) sensor signal, the individual noise components can largely compensate for each other.

[0025] Alternatively, the control device can be configured to average the values ​​of these sensor signals and monitor the processing of the workpiece based on the average values ​​of these sensor signals.

[0026] By averaging the sensor signals from at least four optical sensors, monitoring of the laser processing process can be achieved even if the signal-to-noise ratio of a single sensor signal is low.

[0027] Typically, the processing of the workpiece can be monitored using this control device. This is done by comparing the average value of the sensor signals with a threshold. Whether the average value of the sensor signals is higher or lower than the threshold, the processing of the workpiece can be assessed as "normal" or "abnormal." The laser processing system can be configured to output a message when the average value of the sensor signals is lower or higher than the threshold.

[0028] Similarly, monitoring the machining of the workpiece may include comparing a sensor signal curve with a pre-defined sensor signal curve. For this purpose, sensor signal curves within a defined time period may be acquired and / or used.

[0029] The laser processing system may include at least six optical sensors, preferably at least eight, preferably at least ten, preferably at least fifteen, preferably at least twenty, preferably at least thirty, preferably at least forty, preferably at least fifty, or these sensors may be used in the methods disclosed herein. A large number of sensors improves the persuasiveness of the average value and allows for the acquisition of well-evaluable useful signals even when the signal-to-noise ratio of a single sensor signal is low. Furthermore, as the number of sensors increases, the total usable sensor area also increases.

[0030] These optical sensors may include optical semiconductor sensors or optical semiconductor sensors. At least 50%, at least 70%, at least 90%, or all of the optical sensors may be optical semiconductor sensors. Optical semiconductor sensors may include at least one semiconductor material or element for detecting radiation.

[0031] Preferably, these optical semiconductor sensors are optical compound semiconductor sensors. The compound semiconductor sensor may include at least one compound semiconductor material for detecting radiation. The compound semiconductor material may contain at least two or at least three different elements. The compound semiconductor material may be a binary or ternary material. These optical compound semiconductor sensors may be group III-V compound semiconductor sensors or group II-VI compound semiconductor sensors.

[0032] The semiconductor material of these optical sensors may contain gallium. The semiconductor material of these optical sensors may contain arsenic. The semiconductor material of these optical sensors may contain phosphorus. Preferably, the semiconductor material contains gallium and arsenic, or gallium and phosphorus. Particularly preferably, the semiconductor material contains gallium, arsenic, and phosphorus. These optical semiconductor sensors may be GaAsP sensors.

[0033] None of these optical sensors can be silicon sensors. In particular, none of these optical sensors can be elemental semiconductor sensors. That is, none of these sensors can contain silicon or elemental semiconductors for detecting radiation.

[0034] All or more optical sensors may be of the same type or identical. However, these optical sensors may be positioned in different locations. All or more optical sensors may have the same structure or construction, i.e., have the same sensor area. All or more optical sensors may have the same spectral sensitivity and / or be made of the same material.

[0035] These optical sensors can also include different types of sensors, i.e., those with different spectral sensitivities and / or made of different materials. Therefore, different types of sensors can be distinguished by at least one of the following characteristics: spectral sensitivity; structural type or sensor area; and the material used to detect radiation.

[0036] At least some of the optical sensors may be equipped with optical filters. These optical filters can transmit one or more wavelength ranges of process emission and / or block one or more wavelength ranges of process emission. In this way, although having the same spectral sensitivity, these optical sensors can also be configured to detect process emission in different wavelength ranges (either entirely or partially).

[0037] To calculate the average, sensor signals or sensor values ​​from optical sensors that have the same spectral sensitivity and / or are configured to detect process emissions within the same wavelength range or multiple wavelength ranges can be used (only). The control device can be configured to calculate the average value separately for different wavelength ranges.

[0038] These optical sensors can each have a diameter of at least 0.01 mm. 2 Preferably at least 0.02 mm 2 Preferably at least 0.03mm 2 Preferably at least 0.04 mm 2 The photosensitive area of ​​these optical sensors can be up to 0.1 mm. 2 Preferably, the maximum diameter is 0.08 mm.2 Preferably, the maximum diameter is 0.06 mm. 2 Particularly preferably, the photosensitive area of ​​these optical sensors is 0.03 mm². 2 and 0.05 mm 2 In this way, a compromise can be found between sufficient signal strength and space requirements.

[0039] These optical sensors can be insensitive to wavelengths greater than 900 nm, preferably greater than 800 nm. That is, these optical sensors can be insensitive to radiation with wavelengths at least greater than 900 nm or greater than 800 nm. These optical sensors can also be insensitive to wavelengths at least less than 550 nm, preferably less than 600 nm.

[0040] These optical sensors can be sensitive to wavelengths between 100 nm and 900 nm, preferably between 150 nm and 850 nm, preferably between 200 nm and 800 nm, preferably between 250 nm and 750 nm, preferably between 250 nm and 700 nm, preferably between 300 nm and 680 nm.

[0041] These optical sensors can be sensitive to more than one wavelength range. For example, these optical sensors may include optical filters that exclude wavelengths or wavelength ranges in which the optical sensor is not sensitive.

[0042] The laser beam can have a wavelength between 950 nm and 1200 nm, preferably between 1000 nm and 1150 nm, more preferably between 1000 nm and 1100 nm, and even more preferably between 1025 nm and 1080 nm. Similarly, the laser beam can have a wavelength between 500 nm and 550 nm, preferably between 510 nm and 530 nm.

[0043] The laser processing system may include a fiber laser, a high-power diode laser, or a disk laser to provide the laser beam.

[0044] Preferably, the laser processing system does not include a CO2 laser for providing the laser beam. Therefore, the laser beam can be provided by a laser other than a CO2 laser.

[0045] These optical sensors can be sensitive to radiation with wavelengths shorter than the laser beam wavelength. Between the maximum wavelength that these optical sensors are sensitive to and the wavelength of the laser beam, there can be a spectral interval of at least 10 nm, preferably at least 25 nm, preferably at least 50 nm, preferably at least 75 nm, preferably at least 100 nm, preferably at least 150 nm, preferably at least 200 nm, preferably at least 250 nm, preferably at least 300 nm.

[0046] These optical sensors can be arranged within the laser processing head. The laser processing head may include a housing. These optical sensors can be arranged within the housing.

[0047] In this laser processing head, particularly in the housing, multiple optical elements for shaping and / or guiding the laser beam can be provided. For example, the laser processing head, especially the housing, can have a laser coupler. The laser coupler can be connected to a laser (i.e., a laser source), for example, via an optical fiber, and the laser beam can be coupled from the laser source into the laser processing head or housing. In this laser processing head, particularly in the housing, collimating optics can be arranged for collimating the laser beam that diverges into the laser processing head or housing. In this laser processing head, particularly in the housing, focusing optics, such as one or more focusing lenses, can be provided for focusing the laser beam onto the workpiece.

[0048] Preferably, all optical sensors are arranged in the laser processing head, particularly in the housing. Alternatively, some sensors, such as up to 30%, up to 20%, or up to 10%, may be arranged outside the laser processing head, particularly outside the housing, while the remaining sensors may be arranged inside the laser processing head, particularly inside the housing.

[0049] These optical sensors can be arranged before the focusing optics relative to the propagation direction of the laser beam. Specifically, all optical sensors are arranged before the focusing optics relative to the propagation direction of the laser beam. The propagation direction of the laser beam can be defined as the direction from its entry into the laser processing head or housing, or from the laser towards the workpiece. However, the invention is not limited to the arrangement before the focusing optics. These optical sensors can also be arranged after the focusing optics.

[0050] These optical sensors can be arranged relative to the propagation direction of the laser beam between the entry point where the laser beam enters the laser processing head and the exit point where the laser beam leaves the laser processing head. In particular, these optical sensors can be arranged relative to the propagation direction of the laser beam between the fiber optic end and the last optical element of the laser processing head. These optical sensors can also be arranged relative to the propagation direction of the laser beam between the collimating optics and the focusing optics.

[0051] Some optical sensors, such as up to 30%, up to 20%, or up to 10%, can be arranged in front of the collimating optics and / or after the focusing optics relative to the propagation direction of the laser beam.

[0052] These optical sensors can be arranged in a plane, for example, in a plane perpendicular to the optical axis of the focusing optics. They can also be positioned at the same distance from the optical axis of the focusing optics. Furthermore, they can be symmetrically arranged within the laser processing head, particularly within the head's housing. This symmetry relates to the optical path of the laser beam. Similarly, this symmetry relates to the optical axis of the focusing optics. In particular, the optical sensors are arranged symmetrically around the optical axis of the focusing optics. In this way, monitoring independent of the processing direction can be provided.

[0053] The photosensitive surface of the corresponding optical sensor can be oriented towards the workpiece or towards the exit opening of the laser processing head, or in other words, facing them. Similarly, the photosensitive surface of the corresponding optical sensor can be oriented away from the workpiece or away from the exit opening of the laser processing head. The photosensitive surface of the corresponding optical sensor can also be opposite to the workpiece or the exit opening of the laser processing head. Here, process emissions can enter the laser processing head and be reflected onto the sensor within the laser processing head, for example, by an optical interface.

[0054] Preferably, all optical sensors are arranged outside the optical path of the laser beam. The optical path of the laser beam can be defined by optical elements in the laser processing head.

[0055] The laser processing system may include a sensor arrangement. These optical sensors, especially all optical sensors, may be arranged on or within the sensor arrangement. The sensor arrangement may be located in the laser processing head, particularly in the housing of the laser processing head. The sensor arrangement may include a circuit board or plate on which the optical sensors are arranged.

[0056] The sensor arrangement, particularly the circuit board or plate, can be constructed as a ring. These optical sensors can be arranged on the ring surface of the sensor arrangement. This ring surface can be flat. The optical sensors can be uniformly or regularly distributed or irregularly distributed along the ring surface. The sensor arrangement can be constructed as rotationally symmetric. The sensor arrangement can be arranged coaxially with the optical axis of the focusing optics.

[0057] The sensor arrangement may have a notch. This notch may be formed substantially at the center of the sensor arrangement. The notch may be (completely) surrounded by the annular surface of the sensor arrangement. The sensor arrangement may be positioned within the laser processing head or its housing such that the laser beam passes through the notch during workpiece processing. The sensor arrangement may at least partially, and especially completely, surround the optical path of the laser beam.

[0058] The sensor arrangement may have an inner diameter of at least 5 mm, preferably at least 10 mm, preferably at least 20 mm, and preferably at least 25 mm. The inner diameter of the sensor arrangement may be at most 150 mm, preferably at most 100 mm, preferably at most 50 mm, preferably at most 40 mm, and preferably at most 35 mm. The inner diameter of the sensor arrangement may correspond to the diameter of the notch.

[0059] These optical sensors can be arranged in a plane. This plane can be oriented substantially (±10° or ±5°) perpendicular to the optical axis of the focusing optics or the optical path or propagation direction of the laser beam.

[0060] All optical sensors can be arranged in this plane. Alternatively, only some of the optical sensors, such as at least 50%, 60%, 70%, 80%, or 90%, can be arranged in this plane. The remaining optical sensors can be arranged outside this plane.

[0061] At least two optical sensors may be arranged in a stack. Preferably, at least four, more preferably at least ten, and more preferably at least fifteen optical sensors are arranged in the stack.

[0062] These optical sensors can be arranged along an (imaginary) line in the stack. This line can extend substantially (±10°, ±5°, or ±2°) parallel to the optical axis of the laser beam. This optical axis can be determined by collimating optics and / or focusing optics.

[0063] The laser processing system may include multiple stacks of optical sensors. Preferably, the laser processing system includes at least two, more preferably at least three, more preferably at least four, and more preferably at least five stacks. Each stack may be any stack disclosed herein.

[0064] These stacks can be arranged around the optical axis. In the circumferential direction around the optical axis, these stacks can be arranged uniformly. Similarly, these stacks can be arranged non-uniformly around the optical axis.

[0065] Typically, this laser processing system can be configured to cut workpieces using a laser beam. The laser processing procedure can be a laser cutting process.

[0066] The control device can be configured to determine the laser beam's entry point into the workpiece based on the signals from these optical sensors, particularly the average value; monitor the laser beam's entry process; determine the workpiece processing quality; identify cutting errors; determine the quality of the cut edge; and identify cutting interruptions and / or cutting cessation. To perform these operations, the sensor signals from all optical sensors can be used. In particular, the average value of all sensor signals can be calculated, and the operations can be performed based on this average value.

[0067] Typically, the laser processing procedure that can be performed in the laser processing system can be modified based on determining the timing of the laser beam's penetration into the workpiece, monitoring the laser beam's penetration process, determining the workpiece's processing quality, and / or determining the quality of the cut edge of the workpiece. This modification of the laser processing procedure can be achieved through process control or adjustment.

[0068] The laser processing process can be monitored by detecting process emissions using these optical sensors. In particular, multiple sensors shielding the laser radiation diffusely scattered within the cutting head or the backscattered radiation of the processing laser enable rapid and accurate monitoring of the laser processing process. The structure is relatively simple and compact. Attached Figure Description

[0069] The present invention will now be described in detail with reference to the accompanying drawings.

[0070] Figure 1 The laser processing system 100 is shown. Figure 2 Some components of the laser processing system 100 are schematically shown; Figure 3 Sensor arrangement 16 is shown; Figure 4a A side view schematically illustrates some components of the laser processing system 100; and Figure 4b A top view schematically showing some components of the laser processing system 100 is shown. Detailed Implementation

[0071] Figure 1 A laser processing system 100 is shown. The laser processing system 100 may include a laser processing head 10, at least four optical sensors 17 (in... Figure 3 (As shown in detail below) and control equipment 30. The laser processing system 100 may also include a laser 20.

[0072] The laser 20 can generate a processing laser beam L (laser beam). The laser 20 can be configured as a single-mode laser, a solid-state laser, a fiber laser, a high-power diode laser, or a disk laser. Preferably, the laser is not configured as a CO2 laser.

[0073] The processing laser beam L generated by laser 20 can be transmitted from laser 20 to laser processing head 10 via optical fiber. The processing laser beam L can be coupled into laser processing head 10 via fiber optic coupler 14. The fiber optic coupler 14 can be arranged on the housing 11 of laser processing head 10.

[0074] The laser processing head 10 may include a collimating optics 12. The collimating optics 12 may be arranged and configured in the laser processing head 10 such that the processing laser beam L, which diverges into the laser processing head 10, is collimated. The collimating optics 12 may be arranged in the housing 11 of the laser processing head 10.

[0075] The collimating optics 12 may include at least one lens or two or more lenses. The distance between the two or more lenses may be adjustable, particularly by means of an electric motor. The collimating optics 12 may define an optical axis.

[0076] Furthermore, the laser processing system 100 may include a focusing optics 13. The focusing optics 13 may be arranged and configured in the laser processing head 10 such that the collimated processing laser beam L is focused. The focusing optics 13 may be disposed within the housing 11 of the laser processing head 10.

[0077] The focusing optics 13 may include at least one lens or two or more lenses. The distance between the two or more lenses may be adjustable, particularly by means of a motor. The focusing optics 13 may define the optical axis. The focusing optics 13 may be an F-Theta objective lens.

[0078] A focused processing laser beam L can be emitted from the laser processing head 10 and irradiate the workpiece W to process the workpiece W.

[0079] The laser processing head 10 may include an exit opening 40. A laser beam can exit the laser processing head 10 from the exit opening 40 and be directed toward the workpiece W. The exit opening 40 may be formed in a nozzle disposed at the end of the laser processing head 10, particularly at the end of the housing 11 of the laser processing head 10.

[0080] For example, a workpiece W can be cut. Here, a laser beam L irradiates the surface of the workpiece W until that area of ​​the workpiece W melts or evaporates. The laser beam L can irradiate that area of ​​the workpiece W until the workpiece W is penetrated (i.e., so-called piercing). Here, a hole can be formed in the workpiece W, through which the laser beam L can irradiate. Subsequently, the laser beam L can move along the processing path to form a cut in the workpiece W. Similarly, the workpiece W can be welded or brazed. In particular, two workpieces W can be welded or brazed together.

[0081] The laser processing head 10 can be a laser beam cutting head, a laser beam welding head, or a laser beam brazing head.

[0082] Workpiece W can emit process emission P. This process emission P can include radiation in different wavelength ranges, such as those in the human visible wavelength range, the infrared wavelength range, the ultraviolet wavelength range, and the wavelength range of laser radiation L. Process emission P can be emitted from workpiece W into laser processing head 10, particularly through exit opening 40.

[0083] At least four optical sensors 17 can be arranged in the laser processing head 10. These optical sensors 17 are insensitive to radiation having a wavelength of the laser beam L, and therefore the back-reflected laser radiation L will not be detected by these optical sensors 17. However, these optical sensors 17 are configured to detect process emission P. For this purpose, these optical sensors 17 preferably have spectral sensitivity at least in the visible light wavelength range, i.e., between 350 nm and 780 nm. Preferably, these optical sensors 17 are insensitive in the wavelength range greater than 900 nm. Below 900 nm wavelength, these optical sensors 17 may be at least partially or within a certain range sensitive to radiation, especially process emission P.

[0084] These optical sensors 17 detect the emission of P within one or more wavelength ranges excluding the wavelength of the laser beam L, and generate sensor signals (measurement signals). Each optical sensor 17 can generate one sensor signal.

[0085] The sensor signals of these optical sensors 17 at a given time point can be averaged by the control device 30 to obtain the average value of the sensor signals.

[0086] Similarly, these sensors 17 can be connected in parallel. By connecting them in parallel, a (summed) sensor signal can be generated using these sensors 17. This (summed) sensor signal can correspond to the average value of the sensor signals.

[0087] Based on this average value, the laser processing process can be monitored. Specifically, the piercing time of the laser beam into workpiece W can be determined, the piercing process of the laser beam L into workpiece W can be monitored, and the processing quality of workpiece W and / or the quality of the cut edge of workpiece W can be determined. The piercing and cutting processes may differ for different workpieces W or different areas on the same workpiece W. For example, when an area of ​​workpiece W is "hot," the piercing process may end faster compared to a "cold" area of ​​workpiece W. If another piercing or cutting process has already been performed near the area of ​​workpiece W where the piercing process is to be performed, that area of ​​workpiece W may already have an elevated temperature, and the piercing process will be shortened.

[0088] This monitoring allows for the control or adjustment of the laser processing process. For example, once the piercing process is complete, the laser beam L can move along the processing path to form a cut. Therefore, it is helpful to know the completion of the piercing process with minimal time delay. By averaging, rapid monitoring of the laser processing process is achieved, enabling improved execution of the laser processing procedure.

[0089] These optical sensors 17 can be arranged in the laser processing head 10 before the focusing optics 13 relative to the propagation direction of the laser beam L. Preferably, these optical sensors 17 are arranged in the laser processing head 10 before the focusing optics 13 and after the collimating optics 12 relative to the propagation direction of the laser beam L. It is also possible that these optical sensors 17 are arranged in the laser processing head 10 after the focusing optics 13 or before the collimating optics 12 relative to the propagation direction of the laser beam L. However, it is preferable that all optical sensors 17 are arranged in the laser processing head 10.

[0090] These optical sensors 17 can be arranged in a plane. This plane can be oriented substantially perpendicular to the optical axis of the focusing optics 13 and / or the optical axis of the collimating optics 12.

[0091] The photosensitive surfaces of the corresponding optical sensors 17 can be oriented or face the workpiece W and / or the outlet opening 40. That is, the photosensitive surfaces of these optical sensors 17 can be opposite to the workpiece W and / or the outlet opening, or face the workpiece and / or the outlet opening. Similarly, the photosensitive surfaces of these optical sensors 17 can face the inlet location, such as the fiber optic coupler 14. The corresponding photosensitive surfaces of these optical sensors 17 can be arranged substantially (±10° or ±5°) perpendicular to the optical axis of the focusing optics 13.

[0092] The laser processing system 100 may include a sensor arrangement 16. Optical sensors 17, preferably all of them, may be arranged on or within the sensor arrangement 16. The sensor arrangement 16 is optional. These optical sensors 17 may also be included in the laser processing system 100 without the sensor arrangement 16. For example, these optical sensors 17 may be arranged individually or in groups on the housing 11 of the laser processing head 10.

[0093] The sensor arrangement 16 can be disposed in the laser processing head 10, particularly in the housing 11 of the laser processing head 10. Preferably, the sensor arrangement 16 is positioned in front of the focusing optics 13 relative to the propagation direction of the laser beam L. The sensor arrangement 16 can be disposed between the collimating optics 12 and the focusing optics 13.

[0094] In addition, the laser processing head 10 may include lenses, transmission elements, reflection elements, radiation shaping elements, beam splitters, and / or optical wedges.

[0095] The optical elements of the laser processing head 10 can define an optical path for the processing laser beam L to pass through the laser processing head 10.

[0096] Figure 2 Some components of a laser processing system 100 are illustrated schematically. A collimating optics 12, a focusing optics 13, and an optional sensor arrangement 16 with an optical sensor 17 are shown. The laser processing system 100 may include or have some or all of the components and / or features disclosed herein.

[0097] These optical sensors 17, for example, arranged on or in the sensor arrangement 16, may be positioned in front of the focusing optics 13 relative to the propagation direction of the laser beam L. The process emission P emitted from the workpiece W can enter the laser processing head 10, pass through the focusing optics 13, and reach these optical sensors 17.

[0098] The diameter D2 of the focusing optics 13 can be larger than the diameter D1 of the collimating optics 12. In particular, the outer diameter of the focusing optics 13 can be larger than the outer diameter of the collimating optics 12. Thus, these optical sensors 17 or sensor arrangement 16 can be arranged outside the optical path of the laser beam L, and the optical path of the process emission P entering the laser processing head 10 can be guided through the focusing optics 13.

[0099] Figure 3 One embodiment of the sensor arrangement 16 is shown. The sensor arrangement 16 includes these optical sensors 17. (Only some of the sensors 17 are shown with reference numerals in Figure 3).

[0100] All or a portion of the optical sensors 17 may be arranged on or within the sensor arrangement 16.

[0101] The sensor arrangement 16 can have any shape and can be arbitrarily arranged in the laser processing head 10 or in the housing 11 of the laser processing head 10. Figure 3 In the example, the sensor arrangement 16 is configured as a ring. These optical sensors 17 can be arranged on the ring surface 16a of the sensor arrangement 16. These optical sensors 17 can be arranged uniformly or non-uniformly on the sensor arrangement 16.

[0102] The sensor arrangement 16 may have a notch 16b. The notch 16b may be formed substantially at the center of the sensor arrangement 16. An annular surface 16a may at least partially, and especially completely, surround or enclose the notch 16b. The sensor arrangement 16 may be positioned in the laser processing head 10 such that the laser beam L can pass through the notch 16b to irradiate the light source. Preferably, when the sensor arrangement 16 is positioned in the laser processing head 10, the annular surface 16a surrounds the optical path of the laser beam L.

[0103] These optical sensors 17 may have a photosensitive surface. When radiation of a wavelength (one or more detectable wavelength ranges) of which these optical sensors 17 are detectable is irradiated onto the photosensitive surface, these optical sensors 17 may generate a measurement signal or a sensor signal.

[0104] The photosensitive surfaces of these optical sensors 17 can face the workpiece W. Similarly, the photosensitive surfaces of these optical sensors 17 can face the exit opening 40. The photosensitive surfaces of these optical sensors 17 can be arranged in the laser processing head 10 substantially (±10° or ±5°) perpendicular to the optical axis of the focusing optics 13 or the collimating optics 12.

[0105] By arranging these optical sensors 17 within the laser processing head 10, an additional steering mirror is unnecessary for coupling the output process emission P from the optical path. Similarly, an additional beam splitter is unnecessary for coupling the output process emission P from the optical path. This also achieves a compact structural form for the laser processing head 10 or the laser processing system 100.

[0106] Figure 4a Some components of the laser processing system 100 are schematically shown. The laser processing system 100 can be any laser processing system disclosed herein, and the same components will not be described again. Figure 4a The view shown is a schematic side view.

[0107] The laser processing system 100 includes at least four optical sensors 17 as described. At least two optical sensors 17 may be arranged in a stack 18. Preferably, at least four, more preferably at least ten, and more preferably at least fifteen optical sensors 17 are arranged in the stack 18. These optical sensors 17 may be arranged along an imaginary line in the stack 18. This line may extend substantially parallel to the optical axis of the laser beam L. This optical axis may be determined by collimating optics 12 and / or focusing optics 13.

[0108] The stack 18 can be completely arranged in the laser processing head 10, and in particular, completely arranged in the housing 11 of the laser processing head 10. The stack 18 can be completely arranged (along the optical axis of the laser beam L) between the collimating optics 12 and the focusing optics 13.

[0109] The optical sensors 17 stacked 18 can all be in contact with each other. Similarly, the optical sensors 17 stacked 18 can all be spaced apart from each other.

[0110] Figure 4b A schematic top view is shown. Figure 4a Components of the laser processing system 100.

[0111] The laser processing system 100 may include multiple stacks 18 having optical sensors 17. Preferably, the laser processing system 100 includes at least two, more preferably at least three, more preferably at least four, and more preferably at least five stacks 18. Each stack 18 may be any stack 18 disclosed herein. All stacks 18 may each contain the same number of optical sensors 17. These optical sensors 17 may be arranged in the same manner in all stacks 18. Similarly, these stacks 18 may contain different numbers of optical sensors 17, and / or these optical sensors 17 may be arranged in different manner in the stacks 18.

[0112] These stacks 18 can be arranged around the optical axis. In the circumferential direction around the optical axis, these stacks 18 can be arranged uniformly. For example, if the laser processing system 100 includes four stacks 18 with optical sensors 17, one stack 18 can be arranged every 90° in the circumferential direction around the optical axis. Similarly, these stacks 18 can be arranged non-uniformly around the optical axis.

Claims

1. A laser processing system (100) for processing a workpiece (W) using a laser beam (L), the laser processing system (100) comprising: A laser processing head (10) having at least one focusing optics (13) for focusing the laser beam (L) so that the workpiece (W) is heated and process emission (P) occurs. At least four optical sensors (17), wherein the optical sensors (17) are insensitive to radiation having the wavelength of the laser beam (L), and wherein each of the optical sensors (17) is configured to detect the process emission (P) within at least one wavelength range excluding the wavelength of the laser beam (L), and generate a corresponding sensor signal accordingly; and A control device (30) is configured to monitor the processing of the workpiece (W) based on the average value of the sensor signals.

2. The laser processing system according to claim 1, comprising at least six optical sensors (17), preferably at least ten optical sensors (17), preferably at least twenty optical sensors (17), preferably at least thirty optical sensors (17), and preferably at least fifty optical sensors (17).

3. The laser processing system according to any one of the preceding claims, wherein, The optical sensor (17) includes a semiconductor sensor, preferably a compound semiconductor sensor, and more preferably a GaAsP sensor.

4. The laser processing system according to any one of the preceding claims, wherein, All optical sensors (17) are of the same type, or the optical sensors (17) include at least two different types of sensors.

5. The laser processing system according to any one of the preceding claims, wherein, The optical sensor (17) is insensitive at least in the wavelength range of greater than 900 nm, preferably greater than 800 nm, and / or less than 550 nm, preferably less than 600 nm.

6. The laser processing system according to any one of the preceding claims, wherein, The laser beam (L) has a wavelength between 950 nm and 1200 nm, preferably between 1000 nm and 1150 nm, or a wavelength between 500 nm and 550 nm.

7. The laser processing system according to any one of the preceding claims, wherein, The optical sensor (17) is arranged in the laser processing head (10), and in particular, the laser processing head (10) includes a housing (11) in which the optical sensor (17) is arranged.

8. The laser processing system according to any one of the preceding claims, wherein, The optical sensor (17) is arranged in front of the focusing optics (13) relative to the propagation direction of the laser beam (L).

9. The laser processing system according to any one of the preceding claims, wherein, The optical sensor (17) is arranged outside the optical path of the laser beam (L), and / or wherein the optical sensor (17) is arranged in a plane perpendicular to the optical axis of the focusing optics (13), and / or the optical sensor (17) is symmetrical with respect to the optical axis of the focusing optics (13).

10. The laser processing system according to any one of the preceding claims, further comprising a ring-shaped sensor arrangement (16), wherein, The optical sensor (17) is arranged on the annular surface (16a) of the sensor arrangement (16), and in particular, the sensor arrangement (16) is arranged coaxially with the optical axis of the focusing optics (13).

11. The laser processing system according to any one of claims 1 to 9, wherein, At least two optical sensors (17), preferably at least three or at least four optical sensors (17) are arranged in a stack (18), wherein the optical sensors (17) are arranged along a line, and in particular, wherein the laser processing system (100) comprises at least two stacks (18) having sensors (17).

12. The laser processing system according to any one of the preceding claims, wherein, The laser processing system (100) is configured to penetrate the workpiece (W) with the laser beam (L) and / or cut the workpiece (W) with the laser beam (L).

13. The laser processing system according to any one of the preceding claims, wherein, The control device (30) is configured to determine the piercing time of the laser beam (L) into the workpiece (W) based on the average value, monitor the piercing process of the laser beam into the workpiece (W), determine the processing quality of the workpiece (W), determine the quality of the cut edge of the workpiece (W), and / or adjust the processing process.

14. The laser processing system according to any one of the preceding claims, wherein, The optical sensors (17) are connected in parallel, and in particular, the average value of the sensor signals is a sensor signal obtained by connecting the optical sensors (17) in parallel.

15. A method for processing, particularly cutting, a workpiece (W) using a laser beam (L), wherein, The method includes the following steps: The laser beam (L) is irradiated onto the workpiece, causing the workpiece (W) to be heated and process emission (P) to occur. The process emission (P) is detected by at least four optical sensors (17) in at least one wavelength range excluding the wavelength of the laser beam (L), and a corresponding sensor signal is generated accordingly, wherein the optical sensors (17) are insensitive to radiation having the wavelength of the laser beam (L). as well as The processing of the workpiece (W) is monitored based on the average value of the sensor signals, especially with the aid of a control device (30).

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