Method and apparatus for determining the state of laser processing

Abstract

To provide a determining method and the like for a laser processing state that can determine a processing state with good accuracy, while suppressing poor processing from being detected excessively, in determining the processing state in laser welding processing.SOLUTION: A determining method for a laser processing state includes: a step of detecting reflected light of laser light in a welded spot formed on a surface of a work-piece by irradiating the work-piece with the laser light as well as thermally-emitted light and plasma light which are generated in the welded spot, using a light sensor; a step of performing first determination of a degree of shape variation of the welded spot caused by irradiating the work-piece with the laser light, on the basis of intensity of the reflected light detected by the light sensor; a step of performing second determination of a degree of temperature variations of the welded spot, on the basis of intensity of the plasma light and the thermally-emitted light detected by the light sensor; a step of determining whether poor processing occurs or not in the laser processing, on the basis of determined results by the first determination and the second determination; and a step of outputting a determined result of the poor processing.SELECTED DRAWING: Figure 7

Description

Technical Field

[0005] ,

[0004] , , , ,

[0003]

[0001] The present disclosure relates to a method and an apparatus for determining a laser processing state used for monitoring a processing point on a workpiece in laser processing, particularly laser welding.

Background Art

[0002] As an example of monitoring a welding process at a processing point on a workpiece to be laser welded, there is a technique for measuring plasma light, thermal radiation light such as infrared light, and reflected light of the laser light for processing generated by heating the workpiece. In such monitoring, the laser light emitted from the laser oscillator reaches the processing point through an optical system such as a condenser lens, is reflected at the processing point and returns to the optical system, and is converted into an electrical signal by an optical sensor including a photodetector. Further, the plasma light and thermal radiation light generated by heating the processing point are similarly converted into electrical signals through the above optical system. From the change in the signal according to the intensity of the light thus acquired as an electrical signal, the state of the processing point is observed, and for example, a welding defect such as a defect of the workpiece or generation of spatter is determined.

[0003] For example, Patent Document 1 discloses a method for determining the quality of a laser weld related to a defect of a workpiece. The method of Patent Document 1 uses the intensities of plasma light and reflected light to determine the occurrence of a defect by comparing with respective appropriate reference values determined in advance by the weld material. (A) of FIG. 12 shows the processing flow of the quality determination algorithm described in FIG. 2 of Patent Document 1, and (B) of FIG. 12 shows the quality determination table (FIG. 3 of Patent Document 1) in that case.

[0004] In the quality determination algorithm of (A) of FIG. 12, when laser welding is started in step 101, measurement of the plasma light intensity is started in step 102, and at the same time, measurement of the reflected light intensity is started in step 103. Next, in step 104, a first quality determination 1 of the welded portion is performed from the measurement data of the plasma light intensity and the measurement data of the reflected light intensity.

[0005] The first quality determination 1 in Patent Document 1 is performed according to the situations shown in the table in Figure 12(A). For example, in situation 4 in Figure 12(B), the plasma light intensity and reflected light intensity are within the appropriate standard range, so the quality of the weld is determined to be good. On the other hand, in situations 2, 3, 5, and 6, if either the plasma light intensity or the reflected light exceeds the appropriate standard value or falls below the appropriate standard value, the weld is determined to be poor. Furthermore, in situations like situation 1, where both the plasma light and reflected light intensities exceed the appropriate standard values, the weld temperature is measured in step S107 after the welding is completed, and a second quality determination of the weld is made based on the measurement results. This ensures that the welding quality is properly determined even in situations like situation 1, where the welding may be good due to defects in the workpiece material such as oil adhesion.

[0006] Furthermore, Patent Document 2 discloses a laser welding apparatus that, when welding a workpiece using a laser beam, measures the intensity of infrared light from the weld to determine whether or not the weld is sound. Figure 13 shows a flowchart for determining welding quality, which identifies the welding state and the causes of welding defects, as described in Figure 4 of Patent Document 2.

[0007] In Patent Document 2, in the judgment flow shown in Figure 13, a threshold y1 is set for the intensity of infrared light emitted from the weld (#30), and a threshold y2 is set as an upper limit for the monitor output measured from the irradiated laser (#40). Threshold y1 is determined in advance by experiment as the lower limit of the infrared light intensity when the laser beam is irradiated normally, and threshold y2 is determined as the upper limit of the monitor output when a sound weld is often not obtained. The laser welding apparatus of Patent Document 2 first determines whether the infrared light intensity is appropriate using #30, and if it is determined to be appropriate, it determines whether the monitor output is appropriate using #40. Only if both conditions #30 and #40 are met is the weld determined to be sound (#50). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 4432282 [Patent Document 2] Japanese Patent Publication No. 2017-113789 [Overview of the project] [Problems that the invention aims to solve]

[0009] Conventionally, in monitoring technologies using light such as plasma light, reflected light, or infrared light generated in laser welding, as described in Patent Documents 1 and 2, processing conditions such as welding defects are determined based on criteria such as whether the intensity of each light exceeds a certain threshold or reaches a normal range.

[0010] However, these light intensities often include noise that does not significantly affect welding quality, such as abnormal light emission caused by surface foreign matter on the workpiece. Therefore, judging the welding condition by comparing the intensity of individual lights with their respective thresholds or normal ranges, as described above, is prone to misjudging the processing state, and in particular, it is prone to over-detection, where a normal processing state is judged as defective.

[0011] This disclosure aims to solve the above-mentioned problems by providing a laser processing state determination method and apparatus that can accurately determine the processing state while suppressing over-detection of processing defects when determining the processing state in laser welding. [Means for solving the problem]

[0012] The laser processing state determination method of this disclosure includes the steps of: detecting reflected laser light at a weld formed on the surface of a workpiece by irradiation of the workpiece with laser light, as well as thermal radiation light and plasma light generated at the weld, using an optical sensor; making a first determination regarding the degree of shape change of the weld due to irradiation with laser light based on the intensity of the reflected light detected by the optical sensor; making a second determination regarding the degree of temperature change of the weld based on the intensity of the plasma light and thermal radiation light detected by the optical sensor; determining whether or not a processing defect has occurred in the laser processing based on the determination results of the first and second determinations; and outputting the determination result of the processing defect.

[0013] The laser processing state determination device of this disclosure comprises a calculation circuit and a communication circuit that receives signals generated by detecting, using an optical sensor, the reflected laser light from a weld formed on the surface of a workpiece by irradiation of the workpiece with laser light, as well as thermal radiation light and plasma light generated in the weld. The calculation circuit performs a first determination regarding the degree of shape change of the weld due to irradiation with laser light based on the intensity of the reflected light detected by the optical sensor, and performs a second determination regarding the degree of temperature change of the weld based on the intensity of the plasma light and thermal radiation light detected by the optical sensor. Based on the determination results of the first and second determinations, it determines whether or not a processing defect has occurred in the laser processing and outputs a determination result of whether or not a processing defect has occurred. [Effects of the Invention]

[0014] According to the laser processing state determination method and determination apparatus of this disclosure, it is possible to suppress over-detection of processing defects and determine the processing state with high accuracy. [Brief explanation of the drawing]

[0015] [Figure 1] A schematic diagram showing the processing system in Embodiment 1 of this disclosure. [Figure 2] A diagram illustrating the configuration of the laser processing machine in the processing system of Embodiment 1. [Figure 3]Figure illustrating the configuration of the spectroscope in the processing system of Embodiment 1 [Figure 4] Figure illustrating the configuration of the determination device in the processing system of Embodiment 1 [Figure 5] Figure showing the flowchart of the processing state determination process by the determination device of Embodiment 1 [Figure 6] Schematic diagram of the measurement waveform in the processing system of Embodiment 1 [Figure 7] Figure showing the detailed flowchart of the hole presence abnormality determination in Embodiment 1 [Figure 8] Figure for explaining the hole presence abnormality determination in Embodiment 1 [Figure 9] Figure showing the relationship between the feature quantity related to shape variation and the hole presence abnormality in Embodiment 1 [Figure 10] Figure showing the relationship between the feature quantity related to temperature change and the hole presence abnormality in Embodiment 1 [Figure 11] Figure showing the determination result of the hole presence abnormality determination [Figure 12] Figure showing the conventional laser welding quality determination method described in Patent Document 1 [Figure 13] Figure showing the flowchart of the conventional welding quality determination described in Patent Document 2

Mode for Carrying Out the Invention

[0016] (Aspect of the Present Disclosure) A method for determining the state of laser processing according to a first aspect of the present disclosure includes the steps of: using an optical sensor to detect reflected light from a weld formed on the surface of a workpiece by irradiation of the workpiece with laser light, as well as thermal radiation light and plasma light generated in the weld; making a first determination regarding the degree of shape change of the weld due to irradiation of the laser light based on the intensity of the reflected light detected by the optical sensor; making a second determination regarding the degree of temperature change of the weld based on the intensity of the plasma light and thermal radiation light detected by the optical sensor; determining whether or not a processing defect has occurred in the laser processing based on the determination results of the first and second determinations; and outputting the determination result of the processing defect.

[0017] According to a second aspect of this disclosure, in the laser processing state determination method described in the first aspect, the first determination step includes determining whether there is a processing defect with respect to the shape variation of the weld based on the extent to which the intensity of the detected reflected light deviates from the intensity when no processing defect occurs, and the second determination step includes determining whether there is a processing defect with respect to the temperature change of the weld based on the extent to which the intensity of the detected plasma light and thermal radiation light deviates from the intensity when no processing defect occurs.

[0018] According to a third aspect of this disclosure, in the laser processing state determination method described in the first or second aspect, the step of determining whether or not a processing defect has occurred is to determine that a processing defect has occurred when it is not determined in the first determination that no processing defect has occurred and it is not determined in the second determination that no processing defect has occurred.

[0019] According to a fourth aspect of this disclosure, in the method for determining the laser processing state described in any of the first to third aspects, the first determination step is performed based on the percentage of the period during which the signal value indicating the intensity of the reflected light is outside a predetermined tolerance range during the period in which the reflected light is detected, and the maximum value of the signal value, wherein the predetermined tolerance range is set based on the intensity of the reflected light when no processing defect occurs.

[0020] According to a fifth aspect of this disclosure, in the laser processing state determination method described in the fourth aspect, the first determination step is performed by comparing the proportion of the period with a first threshold and the maximum value of the signal with a second threshold.

[0021] According to the sixth aspect of this disclosure, in the laser processing state determination method described in the fifth aspect, the first determination step determines that no processing defect has occurred when the proportion of the period is less than a first threshold or the maximum value of the signal is less than a second threshold.

[0022] According to the seventh aspect of this disclosure, in the method for determining the laser processing state described in any of the first to sixth aspects, the second determination step is performed by calculating the rate of change for each signal value when no processing defect occurs, for each of the signal values ​​indicating the intensity of the thermal radiation light and the signal value indicating the intensity of the plasma light, and comparing the calculated rates of change.

[0023] According to the eighth aspect of this disclosure, in the method for determining the laser processing state described in any of the first to seventh aspects, the processing defect includes either or both of the following: perforation and spatter generation in the welded portion.

[0024] According to the ninth aspect of this disclosure, a program is provided for causing a computer control unit to execute the laser processing state determination method described in any of the first to eighth aspects.

[0025] A laser processing state determination device according to a tenth aspect of the present disclosure includes a calculation circuit and a communication circuit that receives signals generated by detecting, using an optical sensor, the reflected light of the laser beam from a weld formed on the surface of a workpiece by irradiation of the workpiece with the laser beam, as well as the thermal radiation light and plasma light generated in the weld. The calculation circuit performs a first determination regarding the degree of shape change of the weld due to irradiation of the laser beam based on the intensity of the reflected light detected by the optical sensor, performs a second determination regarding the degree of temperature change of the weld based on the intensity of the plasma light and thermal radiation light detected by the optical sensor, determines whether or not a processing defect has occurred in the laser processing based on the determination results of the first and second determinations, and outputs the determination result of the processing defect.

[0026] The embodiments of this disclosure will be described below with reference to the drawings. In the following description, similar components are denoted by the same reference numerals. Their redundant descriptions will be omitted as appropriate.

[0027] (Embodiment 1) Embodiment 1 describes a processing system that performs laser processing for overlap welding and determines the processing state, as an example of using the laser processing state determination method and determination apparatus according to the present disclosure.

[0028] 1. Structure The processing system according to Embodiment 1 will be described with reference to Figure 1. Figure 1 is a schematic diagram showing the processing system 100 in Embodiment 1.

[0029] 1-1. System Overview The processing system 100 includes a laser processing machine 20 that performs laser welding, a spectrometer 14 that detects and spectrally analyzes light from the processing point 8, and a determination device 15 that determines the processing state from the detected light. The object to be processed in the processing system 100, i.e., the workpiece, is, for example, a metal workpiece 7.

[0030] When laser light 4 is shone from the laser processing machine 20 onto the processing point 8 on the workpiece 7, thermal radiation in the near-infrared region due to the temperature rise at the processing point 8, and metal-specific emission or plasma light, which mainly consists of visible light components, are generated. In addition, a portion of the laser light 4 that does not contribute to processing is reflected as backlight. In this way, thermal radiation, plasma light, and reflected light are generated from the molten area 27 formed by the melting of the metal at the processing point 8 on the surface of the workpiece 7 upon irradiation with laser light 4.

[0031] The generated light is focused by the laser processing machine 20 and transmitted to the spectrometer 14 through an optical fiber 13 connecting the laser processing machine 20 and the spectrometer 14. The light transmitted to the spectrometer 14 is spectrally separated into thermal radiation, visible light, and reflected light components according to wavelength, detected by the photodetector 22 of the spectrometer 14, and converted into an electrical signal. When the determination device 15 in the processing system 100 receives the signal converted from the spectrometer 14, it determines the processing state at the processing point 8 based on the signal and outputs the determination result. The processing point 8 is not limited to a point-like region, but may be, for example, a linear region having a predetermined length and width.

[0032] 1-2. Configuration of a laser processing machine Figure 2 illustrates the configuration of the laser processing machine 20 of this embodiment. The laser processing machine 20 comprises a laser oscillator 1, an optical fiber 2, an output collimator 3, a bending unit 5, a focusing lens unit 6, and a detector unit 9. The output collimator 3 includes a collimating lens 31 for obtaining a parallel beam of laser light 4. The bending unit 5 includes a first mirror 16, which is, for example, a dielectric multilayer mirror. The laser processing machine 20 further comprises a second mirror 26 and a focusing collimator 12 including a focusing lens 25.

[0033] The laser oscillator 1 supplies light to generate laser light 4, for example, in a pulsed manner. The laser oscillator 1 supplies light with a wavelength of, for example, 1070 nm (or 532 nm, 450 nm, etc.). The light supplied from the laser oscillator 1 is transmitted, for example, through an optical fiber 2, and the collimating lens 31 of the output collimator 3 forms a parallel beam of laser light 4. The laser light 4 is reflected by the first mirror 16 of the bending unit 5, except for a portion that is transmitted, and is focused by the focusing lens unit 6 and irradiated onto the processing point 8 on the workpiece 7. This performs laser processing for overlap welding of the workpiece 7.

[0034] From the processing point 8, the reflected light of the laser beam 4, along with the plasma light and thermal radiation emitted by the processing, return towards the bending unit 5. The reflected light, plasma light, and thermal radiation that have passed through the first mirror 16 are reflected by the second mirror 26, focused by the focusing lens 25 of the focusing collimator 12, and incident on the spectrometer 14 via the optical fiber 13. Hereafter, the reflected light, plasma light, and thermal radiation will be collectively referred to as monitoring light 11.

[0035] The detector unit 9 includes, for example, a photodetector, and detects the light that has passed through the first mirror 16 from the laser light 4 emitted from the laser oscillator 1, and generates an electrical signal corresponding to the detected light. The generated signal is input to the determination device 15 through the signal line 10 and is used, for example, as a trigger signal to start recording the monitoring light 11 in the determination device 15.

[0036] 1-3. Spectrometer Configuration In the spectrometer 14, the incident monitoring light 11 is separated by wavelength into reflected light of the laser light 4 and plasma light and thermal radiation light emitted from the processing point. Each of these lights is converted into an electrical signal by the photodetector 22 and transmitted to the determination device 15.

[0037] Figure 3 illustrates the configuration of the spectrometer 14 in the processing system 100 of this embodiment. The spectrometer 14 in Figure 3 includes a collimating lens 17, a third mirror 18a, a fourth mirror 18b, a fifth mirror 18c, focusing lenses 19a to 19c, a photodetector 22, a transmission cable 23, and a controller 24, all housed inside a housing 28.

[0038] The collimating lens 17 converts the light transmitted from the laser processing machine 20 through the optical fiber 13 back into parallel light. The light that has passed through the collimating lens 17 is spectrally separated into plasma light, reflected light, and thermal radiation light according to wavelength by the third mirror 18a, the fourth mirror 18b, and the fifth mirror 18c, and then focused by the focusing lenses 19a, 19b, and 19c, respectively. The third mirror 18a transmits plasma light in the visible wavelength range (e.g., 400 nm to 700 nm) and reflects light of other wavelengths. The fourth mirror 18b transmits reflected light at the laser wavelength (e.g., 1070 nm, 532 nm, or 450 nm, depending on the wavelength emitted by the laser oscillator 1) and reflects light of other wavelengths. The fifth mirror 18c reflects thermal radiation light at the infrared wavelength (e.g., 1300 nm).

[0039] The spectrometer 14 in Figure 3 includes, for example, photodetectors 22a, 22b, and 22c, each having high sensitivity to different wavelengths. Each photodetector 22a, 22b, and 22c detects plasma light, reflected light, and thermal radiation light focused by focusing lenses 19a to 19c, respectively, and generates an electrical signal corresponding to the intensity of the detected light. Alternatively, the photodetector 22 may be a single photodetector capable of detecting intensity at each wavelength.

[0040] The electrical signal generated by the photodetector 22 is transmitted to the controller 24 via the transmission cable 23. The controller 24 is a hardware controller that provides overall control over the operation of the entire spectrometer 14. The controller 24 includes a CPU and communication circuits, and transmits the electrical signal received from the photodetector 22 to the determination device 15. The controller 24 includes, for example, an A / D converter that converts the analog electrical signal into a digital signal (also simply called a "signal").

[0041] The above configuration of the spectrometer 14 is merely an example; the spectroscopy of light may be performed using, for example, a combination of dichroic mirrors or filters, or by diffraction gratings. For example, by placing arbitrary band-pass filters in the optical path after the third mirror 18a, the fourth mirror 18b, and the fifth mirror 18c, it may be possible to select the wavelength to be passed through.

[0042] 1-4. Configuration of the Judgment Device In the processing system 100 of this embodiment, the reflected light, plasma light, and thermal radiation light signals spectrally separated by the spectrometer 14 are collected and recorded in the determination device 15 and used to determine the processing state. Figure 4 is a block diagram illustrating the configuration of the determination device 15 in the processing system 100. The determination device 15 is composed of an information processing device such as a computer. The determination device 15 includes a CPU 51 for processing calculations, a communication circuit 52 for communicating with other devices, and a storage device 53 for storing data and computer programs.

[0043] The CPU 51 is an example of the calculation circuit of the determination device 15 in this embodiment. The CPU 51 executes, for example, a control program 56 stored in the memory device 53 to realize predetermined functions, including determination of the processing state.

[0044] In this embodiment, the arithmetic circuit configured as the CPU 51 may be implemented by various processors such as an MPU or GPU, or by one or more processors. Furthermore, the arithmetic circuit may be a dedicated electronic circuit or a reconfigurable electronic circuit designed to realize the above functions, or it may be a various semiconductor integrated circuit such as a GPGPU, TPU, DSP, microcontroller, FPGA, and ASIC.

[0045] The communication circuit 52 is a communication circuit that performs communication in accordance with standards such as IEEE 802.11, 4G, or 5G. The communication circuit 52 may also perform wired communication in accordance with standards such as Ethernet®. The communication circuit 52 can be connected to a communication network such as the Internet. The determination device 15 may communicate directly with other devices via the communication circuit 52, or it may communicate via an access point. In this embodiment, the determination device 15 receives signals from the spectrometer 14 via the communication circuit 52, for example. The communication circuit 52 may also be capable of communicating with other devices without going through a communication network, and may include connection terminals such as a USB® terminal and / or an HDMI® terminal. Furthermore, the communication circuit 52 may be various connection interfaces, such as a PCIe bus connecting the A / D converter in the controller 24 of the spectrometer 14 and the determination device 15.

[0046] The storage device 53 is a storage medium that stores computer programs and data necessary to realize the functions of the determination device 15, and stores various types of data such as the control program 56 executed by the CPU 51 and signals received from the spectrometer 14.

[0047] The storage device 53 is composed of, for example, a magnetic storage device such as a hard disk drive (HDD), an optical storage device such as an optical disc drive, or a semiconductor storage device such as an SSD. The storage device 53 may also include temporary memory elements composed of RAM such as DRAM or SRAM, and may function as the internal memory of the CPU 51.

[0048] 2.Operation The operation of the processing system 100 in this embodiment will be described below.

[0049] The processing system 100 illustrated in Figure 1 uses a spectrometer 14 to spectrally analyze the light generated during laser processing for overlap welding of the workpiece 7, and a determination device 15 determines the processing state at the processing point 8 of the workpiece 7 based on the signal corresponding to the intensity of the spectrally analyzed light.

[0050] In the processing system 100 of this embodiment, the determination device 15 determines abnormalities in the processing state, particularly processing defects such as holes at the processing point 8. For example, in the workpiece 7, which consists of two superimposed members as shown in Figure 1, when the laser beam 4 is irradiated, molten metal may splatter and create holes due to the boiling of foreign matter that may adhere to the interface between the members. Holes do not occur even if foreign matter adheres to the surface of the workpiece 7, but are thought to occur in response to shape changes that cause significant distortion of the shape of the molten metal surface due to the boiling of foreign matter at the interface of the workpiece 7, as well as rapid temperature changes.

[0051] The determination device 15 of this embodiment performs a determination process to determine various processing conditions such as holes. The processing condition determination process in the determination device 15 will be described below with reference to Figures 5 to 8.

[0052] 2-1. Processing to determine the state of processing Figure 5 is a flowchart of the processing state determination process by the determination device 15 of this embodiment. The processes shown in this flowchart are executed at predetermined time intervals, for example, from the start of processing of one workpiece 7 to the start of processing of the next workpiece 7, and each process is executed by the CPU 51 of the determination device 15.

[0053] First, the CPU 51 acquires signals corresponding to the thermal radiation light, plasma light, and reflected light detected by the photodetector 22 of the spectrometer 14 via the communication circuit 52 (S1). Also in step S1, the CPU 51 acquires the signal input from the detector unit 9 of the laser processing machine 20 as a laser output signal corresponding to the laser output from the laser oscillator 1. In the determination device 15 of this embodiment, the waveform data of each signal is acquired as digital data and processed. The laser output signal is used, for example, as a trigger signal, as well as for monitoring whether the laser beam 4 is fluctuating during processing.

[0054] Next, the CPU 51 performs preprocessing on each acquired signal (S2). Preprocessing includes, for example, adjusting the signal intensity according to individual differences in the laser processing machine 20 and / or removing noise using various filters such as low-pass filters. The CPU 51 stores the waveform data, after preprocessing each signal, in the storage device 53.

[0055] Figure 6 shows a schematic diagram of the measurement waveforms after applying preprocessing (S2) to the corresponding signals, as measurement waveforms measured by the photodetector 22 or detector unit 9 for each monitoring light 11 and laser light 4 in the processing system 100 of this embodiment. Figure 6(D) exemplifies the measurement waveform of the laser light 4 corresponding to the laser output signal, and Figures 6(A) to (C) exemplify the measurement waveforms of the monitoring light 11 for plasma light, thermal radiation light, and reflected light, respectively. In Figures 6(A) to (D), the horizontal axis represents time, for example, based on the number of signal samples, and the vertical axis represents the signal intensity as a signal value obtained by converting light intensity to voltage. In Figure 6, period Td is shown as the period during which the laser output is at a steady output for a period corresponding to one pulse of the laser light 4.

[0056] Returning to Figure 5, the CPU 51 uses the signals from each monitoring light 11 after preprocessing (S2) to determine whether a hole has formed (S3). For example, the CPU 51 determines whether a hole has formed in the workpiece 7 from which the processing signal was acquired (S1). Details of this hole formation determination process (S3) will be described later.

[0057] Furthermore, in the determination device 15 of this embodiment, the CPU 51 determines various processing conditions based on changes in the intensity of each signal, in addition to determining the hole abnormality (S3). For example, processing conditions include the focus position of the laser beam 4 irradiated onto the processing point 8, the processing point output of the laser output that reaches the processing point 8, and abnormalities in the gaps between the components of the workpiece 7.

[0058] After performing the determination of hole defects and various other defects (S3, S4), the CPU 51 performs an overall determination of whether or not a machining defect has occurred, for example, according to the results of each determination (S5). For example, if all the determinations in steps S3 and S4 determine that there are no defects, the machining state is determined to be normal; otherwise, a defect is determined to have occurred. The CPU 51 outputs the determination result, for example, via the communication circuit 52 (S6). The determination result can be received and displayed by, for example, an external device that can communicate with the determination device 15. Alternatively, the determination device 15 may be equipped with a display device (for example, a display) that is connected to the CPU 51 in a manner that enables communication, and the determination result may be displayed on the display device.

[0059] According to the above process, the determination device 15 acquires the signal generated by the photodetector 22 of the spectrometer 14 (S1), and determines the processing state (S5) by comprehensively integrating the results of the determination of hole abnormalities (S3) and the determination of other abnormalities (S4). This makes it easier to identify abnormal processing conditions, such as hole abnormalities, that can cause joining defects in laser processing of overlap welding, and to avoid situations such as defective products flowing out to subsequent processes after welding.

[0060] In the above judgment process, an example was described in which, after determining the presence of a hole (S3), other abnormalities are determined (S4). However, the execution order of steps S3 and S4 is not limited to the above example; for example, they may be executed in parallel. Also, in determining the presence of a hole (S3), in addition to determining whether a hole is present, other machining defects such as sputter generation may be determined. Furthermore, for example, only the determination of the hole (S3) may be performed, and the overall judgment (S5) may not be performed.

[0061] 2-1-1. Processing for detecting hole defects The details of step S3 in Figure 5 will be explained using Figures 7 and 8.

[0062] Figure 7 is a flowchart detailing the hole defect detection process (S3) in this embodiment. The process shown in this flowchart is started, for example, after applying preprocessing to the signals of each monitoring light 11 acquired during processing (S1, S2), and with the preprocessed signals held in the storage device 53. Figure 8 is a diagram illustrating the hole defect detection process (S3).

[0063] In the hole-punching abnormality determination process (S3) of this embodiment, as shown in Figure 7, abnormalities are estimated from the perspectives of shape change and temperature change of the molten portion 27 at the processing point 8 as phenomena that occur due to hole-punching abnormalities (S31-S33, S37-S39). Then, by combining the estimation results from each perspective, the presence or absence of a final hole-punching abnormality is determined (S40, S41).

[0064] (1) Determination of hole defects Through diligent research, the inventors have focused on the fact that when a perforation anomaly occurs, the surface shape of the molten part 27, i.e., the molten pool, changes during welding, and the reflection direction of the laser beam 4 fluctuates due to, for example, a change in the angle of the surface of the molten part 27 from the normal state. For example, when a perforation anomaly occurs, the molten metal in the molten pool undergoes a large wave-like shape change, and in particular, the reflection direction of the reflected light fluctuates greatly.

[0065] Therefore, when the shape of the molten portion 27 changes, it is assumed that the amount of incident light to the optical system that observes the light from the processing point 8 in the processing system 100 changes, and the intensity of the monitoring light 11 detected by the photodetector 22, particularly the reflected light, changes. Figure 8(A) is a diagram to explain the estimation regarding shape changes in the hole abnormality determination process (S3), and illustrates the time change in the signal intensity of the reflected light when a hole abnormality occurs.

[0066] In Figure 8(A), the signal intensity of the reflected light, shown by the solid line, fluctuates significantly over time due to the change in shape of the molten portion 27 associated with the occurrence of a perforation anomaly. Therefore, it is conceivable that anomalies in the shape change of the molten portion 27 can be determined based on the signal intensity of the reflected light. However, if, for example, the signal intensity of the reflected light is simply compared with a predetermined threshold, it is susceptible to fluctuations in signal intensity due to noise, and there are concerns that it will be difficult to accurately determine perforation anomalies in response to the shape change of the molten portion 27.

[0067] Therefore, in the hole abnormality determination process (S3) in this embodiment, as will be described later, an abnormality related to shape variation is estimated based on the rate by which the signal intensity of the reflected light deviates from a predetermined normal range in the time axis direction and the magnitude of the change in signal intensity at the time of deviation.

[0068] Furthermore, when a hole formation anomaly occurs, it is often accompanied by a temperature anomaly such as heat generation due to foreign matter contamination in the molten section 27. In this case, the temperature of the molten section 27 rises, which can cause an increase in the brightness of the emitted plasma light and thermal radiation light. The inventors have focused on the fact that the degree of this brightness increase differs depending on the wavelength of the observed emission, and that the rate of change in brightness from the normal state tends to be greater for thermal radiation light than for plasma light. Thus, since the rate of change in signal intensity differs for plasma light and thermal radiation light in response to temperature changes, it is expected that by utilizing this difference in rate of change, it will be possible to observe temperature changes during an anomaly without, for example, separately measuring the temperature of the molten section 27.

[0069] Therefore, in the hole abnormality detection process (S3) of this embodiment, in addition to estimating shape variation, as described later, the rate of variation from the normal state is calculated for each signal intensity of plasma light and thermal radiation light, and the abnormality related to temperature change is estimated using the ratio of each rate of variation.

[0070] In the determination device 15 of this embodiment, in the hole-punching abnormality determination process (S3), the hole-punching abnormality can be determined with high accuracy by combining the estimation results of abnormalities corresponding to the shape fluctuations and temperature changes of the molten portion 27 as described above.

[0071] (2) Operation of the determination device The following describes the operation of the determination device 15 in which it performs the hole abnormality determination process (S3). In this embodiment, the determination device 15 performs the following in the hole abnormality determination process (S33): a process for estimating abnormalities with respect to shape variation (S31-S33) and a process for estimating abnormalities with respect to temperature change (S37-S39).

[0072] (2a) Estimation regarding shape variation In the flowchart of Figure 7, first, the CPU 51 refers to, for example, the storage device 53 and calculates the reflected light NG ratio NGRr based on the stored reflected light signal (S31). The NG ratio indicates the percentage by which the signal intensity deviates from a predetermined normal range in the time axis direction.

[0073] Figure 8(A) illustrates a measurement waveform W1 corresponding to the reflected light signal acquired when a hole-punching abnormality occurs. In the example of Figure 8(A), the reflected light NG ratio NGRr is calculated as the percentage of the period (T1+T2+T3) during which the reflected light signal intensity deviates from a predetermined normal range, with the period Td being the judgment period during which the laser output is in a steady state. The predetermined normal range is, for example, the range in which the signal intensity is less than or equal to the upper limit Wc and greater than or equal to the lower limit Wf, when the upper limit Wc and lower limit Wf are set based on a standard waveform Ws that shows the time change of the average signal intensity during normal welding.

[0074] The standard waveform Ws is obtained, for example, by using waveform data of signals acquired when it is known in advance that normal welding has been performed for each monitoring light 11 of reflected light, plasma light, and thermal radiation light, at least twice, and calculating the average of each time. The upper limit Wc and lower limit Wf are calculated, for example, by adding or subtracting predetermined values ​​from the signal value of the standard waveform Ws. In this embodiment, for example, before the hole abnormality determination process (S3), the standard deviation is calculated for each sampling time in the multiple waveform data used to calculate the standard waveform Ws in advance, and the average value of the standard deviation of the entire waveform data is calculated based on the standard deviation at each sampling time. Then, a value of 3 to 5 times the average value is set as a predetermined value, and the upper limit Wc is the value obtained by adding the predetermined value to the standard waveform Ws, and the lower limit Wf is the value obtained by subtracting the predetermined value from the standard waveform Ws.

[0075] In step S31, the CPU 51 calculates the NG ratio NGRr based on the signal intensity of the reflected light using, for example, the following calculation formula. The upper limit Wc and lower limit Wf of the normal range are calculated for each monitoring light 11 as described above, for example, and stored in the storage device 53, etc. The NG ratio NGRr may also be calculated as a percentage by multiplying the value calculated using the following calculation formula by "100". NGRr = {(Number of samples where the measured waveform W1 exceeds the upper limit Wc of the normal range + Number of samples where the measured waveform W1 falls below the lower limit Wf of the normal range) ÷ Number of samples in the judgment period Td}

[0076] Next, the CPU 51 calculates the normalized peak height PHr of the reflected light based on the reflected light signal (S32). The normalized peak height is the value obtained by normalizing the maximum signal intensity during the judgment period Td, i.e., the peak height of the measured waveform, by the average signal value of the standard waveform Ws during the judgment period Td.

[0077] In the example shown in Figure 8(A), the CPU 51 calculates the normalized peak height Phr for the reflected light signal by dividing the maximum signal value Vb of the measurement waveform W1 during the judgment period Td by the average signal value Va of the standard waveform Ws during the judgment period Td (S32).

[0078] In step S32, the CPU 51 calculates a normalized peak height PHr based on the signal intensity of the reflected light, for example, according to the following calculation formula. PHr = maximum signal value Vb within the determination period Td of the measurement waveform W1 ÷ average Va of the signal values within the determination period Td of the standard waveform Ws The average Va of the standard waveform Ws is calculated in advance for the reflected light signal, for example, and stored in the storage device 53 or the like.

[0079] The CPU 51 determines whether both the NG ratio NGRr and the normalized peak height PHr (S31, S32) calculated for the reflected light are each greater than or equal to the predetermined thresholds TH_NGRr and TH_PHr, that is, whether NGRr ≥ TH_NGRr and PHr ≥ TH_PHr (S33). For example, when both the NG ratio NGRr and the normalized peak height PHr are each greater than or equal to their respective thresholds TH_NGRr and TH_PHr (YES in S33), it is presumed that an abnormality has occurred regarding the shape change of the melting part 27. In this case (YES in S33), the CPU 51 proceeds to the processing after step S37, and the processing for estimating the temperature change (S37 to S39) is executed.

[0080] Each of the thresholds TH_NGRr and TH_PHr is set to a sufficiently small value from the viewpoint of suppressing the overlooking of abnormalities, for example, based on the reflected light signals obtained when performing a plurality of processes in advance and the processing state is determined to be normal or abnormal.

[0081] On the other hand, when NGRr ≥ TH_NGRr and PHr ≥ TH_PHr do not hold, that is, when NGRr < TH_NGRr or PHr < TH_PHr (NO in S33), the CPU 51 determines that no perforation abnormality has occurred (S41). In this case (NO in S33), at least one of the NG ratio NGRr and the normalized peak height PHr is less than its respective threshold TH_NGRr and TH_PHr, and for example, it is presumed that no abnormality in shape variation has occurred.

[0082] As described above, by comparing the reflected light NG ratio NGRr and normalized peak height PHr with their respective thresholds TH_NGRr and TH_PHr (S336, S37), if it is estimated that there is no abnormality in shape variation (NO in S33), it is determined that there is no hole abnormality (S41). On the other hand, if the possibility of shape variation is estimated (YES in S33), estimation processing related to temperature change, such as described below (S37-S39), is performed.

[0083] (2b) Estimation regarding temperature changes First, the CPU 51 calculates the fluctuation rate VRp of the plasma light and the fluctuation rate VRt of the thermal radiation light based on the plasma light and thermal radiation light signals, respectively (S37, S38). The respective fluctuation rates VRp and VRt are indices for estimating abnormalities in the temperature change of the molten section 27 (hereinafter also referred to as "temperature anomalies"), and indicate the degree to which the signal intensity of the plasma light or thermal radiation light deviates from normal in accordance with the temperature anomaly.

[0084] Figure 8(B) is a diagram illustrating the estimation related to temperature changes, and shows the measured waveform W2 corresponding to the plasma light signal as an example of the time change in the signal intensity of plasma light when a perforation anomaly occurs. In Figure 8(B), the signal intensity of the measured waveform W2 is on average higher than that of the standard plasma light waveform Ws when there is no perforation anomaly. Similarly to the plasma light shown in Figure 8(B), for example, when a perforation anomaly occurs, an increasing trend in the average signal intensity is observed in conjunction with the increase in brightness for thermal radiation light.

[0085] The fluctuation rate is calculated as the percentage change in the average signal value Vm of the measured waveform W2 during the judgment period Td relative to the average signal value Va of the standard waveform Ws during the judgment period Td, as shown in Figure 8(B). In steps S37 and S38, the CPU 51 calculates the fluctuation rate VR for the measured waveforms of the plasma light and thermal radiation light signals using, for example, the following formula. Here, VR represents the fluctuation rate VRp of the plasma light or the fluctuation rate VRt of the thermal radiation light. VR = (Average signal value Vm of measured waveform W2 - Average signal value Va of standard waveform Ws) ÷ (Average signal value Va of standard waveform Ws)

[0086] Next, the CPU 51 determines whether the thermal radiation fluctuation rate VRt is greater than the value "a × VRp + b" calculated from the plasma radiation fluctuation rate VRp and predetermined coefficients a and constant b, i.e., whether VRt > (a × VRp + b) (S39). For example, if VRt > (a × VRp + b) (YES in S39), a temperature anomaly is estimated.

[0087] As described above, with respect to the temperature change of the molten portion 27, the fluctuation rates VRp and VRt of the plasma light and thermal radiation light signals, respectively, may differ from the normal signal intensity. In this embodiment, by using the fluctuation rates VRp and VRt for comparison, it is possible to suppress the influence of changes in signal intensity due to the expansion of the light emission area, for example, by the combustion of interfacial foreign matter during processing, and to easily estimate the influence of temperature changes on the signal intensity.

[0088] The coefficient a and constant b used to estimate temperature anomalies are set, for example, based on the thermal radiation and plasma light signals obtained when multiple processing cycles have been performed in advance and the processing state is known to be normal or abnormal, using an approximate straight line that shows the relationship between each fluctuation rate VRt and VRp. For example, an approximate straight line can be calculated from the distribution of each fluctuation rate VRt and VRp in the multiple processing cycles, the slope of the approximate straight line can be set as the coefficient a, and the intercept of the approximate straight line, adjusted from the viewpoint of suppressing the oversight of anomalies under slope a, can be set as the constant b.

[0089] If the relationship between the fluctuation rates VRt and VRp (S37, S38) calculated from the measured waveforms of thermal radiation and plasma light is VRt > (a × VRp + b) (YES in S39), the CPU 51 determines that a hole-punching abnormality has occurred in the workpiece 7 during the machining process when the measured waveform was observed (S40).

[0090] On the other hand, if the thermal radiation fluctuation rate VRt is not greater than (a × VRp + b) calculated from the plasma radiation fluctuation rate VRp, i.e., VRt ≤ (a × VRp + b) (NO in S39), the CPU 51 determines that no hole-punching abnormality has occurred (S41).

[0091] Based on the above, if an abnormality is estimated regarding shape variation and it is not determined that there is no hole defect (YES in S33), and an abnormality is estimated regarding temperature change and it is not determined that there is no hole defect (YES in S39), then it is determined that there is a hole defect (S40).

[0092] CPU 51 terminates the processing of this flowchart if it determines that there is a hole defect (S40) or if it determines that there is no hole defect (S41).

[0093] Through the above process, estimations are made using the signal intensity of reflected light for shape variation (S31-S33) and estimations are made using the signal intensity of plasma light and thermal radiation light for temperature change (S37-S39) to determine whether or not there is a hole defect (S40, S41). In this way, by using the signal intensity of light observed during processing, two estimations are made corresponding to the shape variation and temperature change phenomena that may occur on the surface of the molten part 27 when a hole defect occurs, and by combining the results of each estimation, the presence or absence of a hole defect can be determined with high accuracy.

[0094] Furthermore, the above processing calculates feature quantities such as the NG ratio NGRr, normalized peak height PHr, and fluctuation rate VR from the light signal intensity (S31-S32, S37-S38), and the shape change or temperature change due to the perforation anomaly is estimated from the feature quantities (S33, S39). This reduces the influence of noise and other factors compared to simply using the magnitude of the signal intensity, and allows for a more accurate determination of the presence or absence of a perforation anomaly in accordance with the estimation of the shape change or temperature change of the molten part 27.

[0095] In the example above, the process for determining whether there is a hole defect (S3) is described in which estimation regarding temperature change (S37-S39) is performed after estimation regarding shape variation (S31-S33). The process for determining whether there is a hole defect (S3) is not limited to this, and for example, the estimation regarding shape variation (S31-S33) and the estimation regarding temperature change (S37-S39) may be executed in parallel. In this case, for example, the logical AND of the judgment result regarding shape variation (S33) and the judgment result regarding temperature change (S39) may be calculated to determine that there is a hole defect if YES is obtained in step S33 and YES is obtained in S39 (S40), and that there is no hole defect in other cases (S41).

[0096] 3. Effects, etc. As described above, in this embodiment, the processing state determination process (S1 to S6) provides a method for determining the laser processing state. This method includes, as an example of a process that uses a photodetector 22 (an example of an optical sensor) to detect reflected light of the laser beam 4 from a molten portion 27 (an example of a welded portion) formed on the surface of a workpiece 7 (an example of a workpiece) by irradiation of the workpiece 7 with the laser beam 4, as well as thermal radiation light and plasma light generated in the molten portion 27, the steps of: acquiring the signals of each light (S1); making a first determination (S3, S31~S33) regarding the degree of shape change of the molten portion 27 due to irradiation of the laser beam 4 based on the intensity of the reflected light detected by the photodetector 22; making a second determination (S3, S37~S39) regarding the degree of temperature change of the molten portion 27 based on the intensity of the plasma light and thermal radiation light detected by the photodetector 22; determining (S3, S40, S41) whether or not a hole abnormality has occurred as an example of a processing defect in laser processing, based on the determination results of the first and second determinations; and outputting the processing defect determination result (S6).

[0097] According to the above method, reflected light, plasma light, and thermal radiation from the molten area 27 at the welding processing point 8 on the workpiece 7 are observed (S1), and the state of shape variation and temperature change in the molten area 27 is estimated from the intensity of each by first and second determinations (S3). Then, based on the first and second determination results that estimate each occurrence state, the presence or absence of perforation abnormality is determined as the processing state (S3). In this way, perforation abnormality is determined by combining the first and second determinations regarding the degree of shape variation and temperature change in the molten area 27 based on the intensity of reflected light, plasma light, and thermal radiation observed during welding.

[0098] For example, in the hole-punching abnormality detection process (S3), if abnormalities are estimated with respect to shape variation and temperature change in both the first and second determinations (YES in S33 and YES in S39), it is determined that a hole-punching abnormality machining defect has occurred (S40). This allows for accurate determination of the machining state, for example, by suppressing over-detection of machining defects.

[0099] In this embodiment, the first determination step (S31-S33) includes determining whether there is a hole abnormality (an example of a processing defect) with respect to the shape variation of the molten part 27 based on the NG ratio NGRr and normalized peak height PHr, respectively, as an example of the degree to which the detected intensity of reflected light deviates from the normal range of upper limit Wc and lower limit Wf, and the average Va of the signal value during the determination period Td of the standard waveform Ws (an example of the intensity of reflected light when no processing defect occurs). The second determination step (S37-S39) includes determining whether there is a processing defect with respect to the temperature change of the molten part 27 based on the fluctuation rates VRp and VRt, respectively, as an example of the degree of variation in the detected intensity of plasma light and thermal radiation light compared to the intensity when no hole abnormality occurs. For example, in the first determination, a signal indicating the intensity of reflected light is used, and in the second determination, a signal indicating the intensity of plasma light and thermal radiation light is used, and feature quantities such as the NG ratio NGRr, normalized peak height PHr, and fluctuation rates VRp and VRt are extracted from waveform data showing changes in intensity. Based on these features, a determination is made to estimate the occurrence of abnormalities due to shape changes and temperature changes in the molten portion 27 (S33, S39). This reduces the influence of noise and other factors compared to simply comparing the magnitude of light intensity with normal or abnormal thresholds, for example. As a result, the processing state can be determined with high accuracy.

[0100] In this embodiment, the steps for determining whether or not a processing defect has occurred (S40, S41) are as follows: If the first determination does not determine that no processing defect has occurred and the second determination does not determine that no processing defect has occurred (YES in S33 and YES in S39), then it is determined that a processing defect has occurred (S40). On the other hand, if either the first or second determination determines that no processing defect has occurred (NO in S33 or NO in S39), then it is determined that no processing defect has occurred (S41), thereby reducing the over-detection of processing defects.

[0101] In this embodiment, the first determination step (S31-S33) is performed based on the NG ratio NGRr, which is an example of the period during which reflected light is detected, and the normalized peak height PHr, which is an example of the maximum value of the signal value. The normal range is set based on the standard waveform Ws, which is an example of the intensity of reflected light when no hole abnormality occurs, which is an example of a processing defect. This allows for the estimation of hole abnormalities related to shape variation based on the NG ratio NGRr, which corresponds to the degree to which the signal intensity of reflected light deviates from the normal range in the time axis direction, and the normalized peak height PHr, which corresponds to the magnitude of the change in signal intensity during the deviation.

[0102] In this embodiment, the first determination step (S31-S33) is performed by comparing the reflected light, the NG ratio NGRr, with the NG ratio threshold TH_NGRr, and the normalized peak height PHr, with the peak height threshold TH_PHr (S33). This allows, for example, the thresholds TH_NGRr and TH_PHr to be set for each of the NG ratio NGRr and normalized peak height PHr according to the tendency for the intensity of the reflected light to change due to the shape variation of the molten portion 27, and the first determination to be performed.

[0103] In this embodiment, the first determination step (S31-S33) determines that no hole-punching abnormality, which is an example of a processing defect, has occurred (S41) if the NG ratio NGRr is less than the threshold TH_NGRr or the normalized peak height PHr is less than the threshold TH_PHr (NO in S33). This allows us to estimate that there is no shape variation due to hole-punching abnormality, for example, if the degree to which the signal value deviates from the normal range is smaller than a predetermined standard.

[0104] In this embodiment, the second determination step (S37-S39) is performed by calculating the fluctuation rates VRt and VRp for the average Vm of the measurement waveform W2 (an example of a signal value indicating the intensity of thermal radiation light and a signal value indicating the intensity of plasma light) with respect to the average Va of the standard waveform Ws (an example of each signal value when no perforation abnormality occurs as an example of a processing defect) (S37, S38), and comparing the calculated fluctuation rates VRt and VRp (S39). This makes it possible to perform the second determination by taking advantage of the fact that the fluctuation rates VRt and VRp differ between thermal radiation light and plasma light with respect to the temperature change due to perforation abnormality in the molten part 27.

[0105] In this embodiment, the processing defects to be determined by the processing state determination process (S1-S6) include either or both of the following: perforation and spatter generation in the molten portion 27. Perforation and spatter generation are phenomena that can generally occur as abnormalities in the processing state during laser processing of overlap welding, and there is a need to be able to automatically and accurately determine both of these.

[0106] In this embodiment, a control program 56 is provided as an example of a program for causing a CPU 51, which is an example of a computer control unit, to execute the laser processing state determination method described above.

[0107] In the processing system 100 of this embodiment, a determination device 15 (an example of a device for determining the laser processing state) is provided. The determination device 15 comprises a CPU 51 (an example of an arithmetic circuit) and a communication circuit 52. The communication circuit 52 receives signals generated by detecting, using a photodetector 22 (an example of an optical sensor), the reflected light of the laser beam 4 from the molten portion 27 (an example of a welded portion) formed on the surface of the workpiece 7 (an example of a workpiece) by irradiation of the workpiece 7 with the laser beam 4, as well as the thermal radiation light and plasma light generated in the molten portion 27. The CPU 51 performs a first determination regarding the degree of shape change of the molten part 27 due to irradiation with laser light 4 based on the intensity of reflected light detected by the photodetector 22 (S31-S33), and performs a second determination regarding the degree of temperature change of the molten part 27 based on the intensity of plasma light and thermal radiation light detected by the photodetector 22 (S37-S39). Based on the determination results from the first and second determinations, it determines whether or not a hole-punching abnormality (an example of a processing defect) has occurred in the laser processing (S3, S40, S41), and outputs the determination result of the processing defect (S6).

[0108] According to the above determination device 15, the laser processing state determination method in this embodiment can be executed, suppressing over-detection of processing defects such as hole drilling abnormalities, and enabling accurate determination of the processing state.

[0109] (Examples) An example relating to Embodiment 1 described above will be explained below. Below, an example relating to the hole abnormality detection process (S3) (also referred to as "hole abnormality detection") will be explained using Figures 9 to 11.

[0110] Figure 9 shows the relationship between feature quantities related to shape variation and perforation abnormalities in Embodiment 1. Figure 10 shows the relationship between feature quantities related to temperature change and perforation abnormalities. Figures 9 and 10 show data points that associate feature quantities obtained in multiple welding operations where the processing state is known as either "perforation (NG judgment)" where perforation abnormalities occur or "normal" where no perforation abnormalities occur, with the processing state of each operation. In Figures 9 and 10, data points during normal processing are indicated by "△", and data points during processing where perforation occurred are indicated by "○".

[0111] Figure 9 shows the relationship between features related to shape variation and perforation anomalies. In Figure 9, the vertical axis represents the normalized peak height PHr of reflected light, and the horizontal axis represents the NG ratio NGRr of reflected light. In the example in Figure 9, the threshold for the NG ratio TH_NGRr is set to "3.35%", and the threshold for the normalized peak height TH_PHr is set to "1.3". In this case, each data point is classified into a region indicating a perforation anomaly if the feature is within the range of NGRr ≥ TH_NGRr and PHr ≥ TH_PHr.

[0112] In Figure 9, the region where a hole is detected using the thresholds TH_NGRr and TH_PHr, namely "NGRr≧TH_NGRr and PHr≧TH_PHr," actually includes data points "△" from normal machining. In this case, it results in over-detection, where a normal machining state is incorrectly identified as a hole, but it can suppress the possibility of overlooking a hole and incorrectly identifying it as normal.

[0113] Figure 10 shows the relationship between temperature change features and hole anomalies. In Figure 10, the vertical axis represents the thermal radiation variability VRt, and the horizontal axis represents the plasma radiation variability VRp. In this example, the coefficient a used for the plasma radiation variability VRp in estimating temperature anomalies was 1.2, and the constant b was 2.5. In this case, each data point is classified as not having a hole anomaly, i.e., as being in a normal processing state, if the feature falls within the range of VRt ≤ 1.2 × VRp + 2.5. In Figure 10, the range VRt > 1.2 × VRp + 2.5 is shown as the region where hole anomalies are determined using coefficient a and constant b, but even in this region, there are data points that are over-detected.

[0114] In the perforation abnormality determination of this embodiment, as described above, if a perforation abnormality is estimated to occur based on both the estimation of shape variation of the molten portion 27 and the estimation of temperature change (YES in S33 and YES in S39), then a perforation abnormality is finally determined (S40), thereby reducing false positives.

[0115] Figure 11 shows the results of the hole abnormality detection. Figures 11(A) to (D) show tables that classify the hole abnormality detection results according to the measurement results, where the processing state is known from actual measurements of the workpiece 7 after processing in multiple processing cycles. In Figures 11(A) to (D), a normal judgment or measurement result is indicated as "OK", and an abnormal judgment or measurement result is indicated as "NG". For comparison, Figure 11(D) shows the results of determining the hole abnormality when the hole abnormality detection method according to the present invention is not applied, for example, by visual inspection of the molten part 27 using a camera.

[0116] The table in Figure 11 shows that when the judgment is "OK" and the actual measurement is "OK", the processing state is normal; when the judgment is "OK" and the actual measurement is "NG", the hole abnormality is over-detected; when the judgment is "NG" and the actual measurement is "OK", the hole abnormality is missed; and when the judgment is "NG" and the actual measurement is "OK", there is a hole abnormality. Thus, when the judgment result and the actual measurement result match, the normal state or hole abnormality is correctly determined, while when the judgment result and the actual measurement result do not match, there is an over-detection or missed hole abnormality. As shown in Figure 11(D), when the hole abnormality judgment of the present invention is not applied, the missed detection rate is "0.0%", while the over-detection rate is "84.9%".

[0117] Figure 11(A) shows the results of the estimation regarding shape variation (S31-S33). In this estimation, for example, in the hole abnormality detection shown in Figure 7, if NGRr≧TH_NGRr and PHr≧TH_PHr (YES in S33) are compared with the thresholds for the NG ratio and normalized peak height, then the hole detection result (S40) is considered to be correct. In this estimation, false positives occurred in "6.6%" of cases.

[0118] Figure 11(B) shows the results when, for example, estimations related to shape variation (S31-S33) are not performed, and only estimations related to temperature change (S37-S39) are performed to determine the presence or absence of hole abnormalities (S40, S41). In this estimation, false positives occurred in "6.6%" of cases. Note that the fact that the values ​​of the judgment results from estimations related to shape variation and estimations related to temperature change are the same in Figure 11(A) and (B) is purely coincidental.

[0119] Figure 11(C) shows the result of determining a perforation anomaly in the final perforation anomaly (S40), where cases where a perforation is estimated based on both the estimation related to shape variation and the estimation related to temperature change (YES in S33 and YES in S39) were determined to be perforation anomalies. In this case, not only was the missed detection rate "0.0%", but the overdetection rate was also "0.0%", indicating that overdetection was suppressed.

[0120] (Other embodiments) As described above, Embodiment 1 has been explained as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this and can be applied to embodiments that are modified, replaced, added, or omitted as appropriate. Other embodiments are described below as examples.

[0121] In the above embodiment 1, an example was described in which, in the perforation abnormality determination process (S3), the signal intensity of reflected light is used to estimate abnormalities related to shape variation (S31-S33). The estimation process related to shape variation is not limited to the above example, and may, for example, be performed using the signal intensity of plasma light in addition to reflected light. For example, the NG ratio and normalized peak height may be calculated for plasma light in the same way as for reflected light, and each may be compared with a predetermined threshold. For example, if at least one of the NG ratio and normalized peak height of plasma light is less than the respective threshold, and the result for reflected light is also NO in step S33, then it may be determined that there is no perforation abnormality (S41). On the other hand, if it is not determined that there is no perforation abnormality, for example, estimation related to temperature change (S37-S39) may be performed.

[0122] In the above-described embodiment 1, in the estimation of temperature change shown in Figure 7 (S37-S39), an example was described in which the fluctuation rate VRp of plasma light was calculated (S37), followed by the calculation of the fluctuation rate VRt of thermal radiation (S38). In this embodiment, the execution order is not limited to that illustrated in Figure 7. For example, the calculation of the fluctuation rate VRp of plasma light (S37) may be performed after the calculation of the fluctuation rate VRt of thermal radiation (S38), or steps S37 and S38 may be executed in parallel.

[0123] This disclosure is not limited to the embodiments described above, and various modifications are possible. In other words, embodiments obtained by combining technical means as appropriately modified by those skilled in the art are also within the scope of this disclosure. [Industrial applicability]

[0124] The laser processing state determination method and determination apparatus of this disclosure can be applied to process monitoring, for example, in welding processes for batteries or electronic components, and in particular can be applied to applications that accurately determine the state of perforation abnormalities by suppressing over-detection. [Explanation of Symbols]

[0125] 1. Laser oscillator 2 Optical Fibers 3. Output Collimator 4. Laser light 5 Bending Units 6. Focusing lens unit 7 Work 8 processing points 9 Detector Unit 10 signal lines 11. Monitoring light (reflected light, plasma light, thermal radiation light) 12. Focusing collimator 13 Optical Fiber 14 Spectrometer 15 Judgment device 16. First mirror (dielectric multilayer mirror) 22 Photo Detectors 23 Transmission Cable 24 controllers 51 CPU 52 Communication Circuits 56 Control Program

Claims

1. A method for determining the state of laser processing, A step of using an optical sensor to detect the reflected light of the laser beam from the weld formed on the surface of the workpiece by irradiating the workpiece with laser light, as well as the thermal radiation light and plasma light generated in the weld, A step of making a first determination regarding the degree of shape variation of the welded part due to irradiation with laser light, based on the intensity of reflected light detected by the optical sensor, the step of making a determination of a processing defect with respect to the shape variation of the welded part based on the degree to which the detected intensity of reflected light deviates from the intensity when no processing defect occurs in laser processing, A second step is to make a determination regarding the degree of temperature change of the welded part based on the intensity of plasma light and thermal radiation light detected by the optical sensor, A step of determining whether or not a processing defect occurred in the laser processing based on the determination results from the first and second determinations, The process includes outputting the result of determining the aforementioned processing defect. A method for determining the state of laser processing.

2. The step of making the second determination includes making a determination of whether there is a processing defect with respect to the temperature change of the welded part, based on the degree of variation in the intensity of the detected plasma light and thermal radiation light compared to the intensity when no processing defect occurs. A method for determining the laser processing state according to claim 1.

3. The step of determining whether or not the aforementioned processing defect has occurred is to determine that the processing defect has occurred when, in the first determination, it is determined that the processing defect has not occurred and in the second determination, it is determined that the processing defect has occurred. A method for determining the laser processing state according to claim 1.

4. The first determination step is performed based on the percentage of the period during which the signal value indicating the intensity of the reflected light is outside a predetermined allowable range during the period in which the reflected light is detected, and the maximum value of the signal value. The predetermined tolerance range is set based on the intensity of the reflected light when no processing defects occur. A method for determining the laser processing state according to claim 1.

5. The first determination step is performed by comparing the proportion of the period with a first threshold and the maximum value of the signal with a second threshold. The method for determining the laser processing state according to claim 4.

6. The first determination step involves determining that no processing defect has occurred if the proportion of the period is less than a first threshold, or if the maximum value of the signal is less than a second threshold. The method for determining the laser processing state according to claim 5.

7. The second determination step involves calculating the rate of change for each of the signal values ​​indicating the intensity of the thermal radiation light and the signal value indicating the intensity of the plasma light, as the percentage change in the average value over a predetermined period compared to the average value of each signal value over the predetermined period when no processing defect occurs, and then comparing the calculated rates of change. A method for determining the laser processing state according to claim 1.

8. The aforementioned processing defects include either or both of the following: perforation and spatter generation in the welded area. A method for determining the laser processing state according to claim 1.

9. A program for causing a computer control unit to execute the laser processing state determination method according to any one of claims 1 to 8.

10. A device for determining the state of laser processing, Calculation circuit and, A communication circuit that receives signals generated by detecting, using an optical sensor, the reflected light of the laser beam from the weld formed on the surface of the workpiece by irradiation of the workpiece with the laser beam, as well as the thermal radiation light and plasma light generated in the weld. Equipped with, The aforementioned arithmetic circuit is Based on the intensity of the reflected light detected by the optical sensor, a first determination is made regarding the degree of shape variation of the welded part due to the irradiation of the laser light, and a determination of a processing defect is made regarding the shape variation of the welded part based on the degree to which the detected intensity of the reflected light deviates from the intensity when no processing defect occurs in the laser processing. Based on the intensity of plasma light and thermal radiation light detected by the aforementioned optical sensor, a second determination is made regarding the degree of temperature change in the welded area. Based on the determination results from the first and second determinations, it is determined whether or not a processing defect occurred in the laser processing. Output the result of the determination of the aforementioned processing defect. A device for determining the state of laser processing.

11. The first determination is made with respect to the deformation of the welded part, based on the extent to which the intensity of the detected reflected light deviates from the intensity when no processing defect occurs after processing in the laser processing. The determination method according to claim 1.

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