JP5187121B2 - Laser processing apparatus and laser processing method - Google Patents

Description

  The present invention relates to a monitoring technique that determines a quality by detecting a machining state during laser machining.

  Laser processing technology that irradiates a workpiece with laser light includes a monitoring technology that measures the processing state in-line. One of them is to measure the light intensity of reflected light or plasma light generated from a workpiece processing point during processing (see, for example, Patent Document 1).

  FIG. 8 is a schematic diagram of the laser processing monitoring apparatus disclosed in Patent Document 1. In FIG.

In FIG. 8, the laser beam from the laser welding machine main body 1 is irradiated to the workpiece 4 through the unit main body 3 of the laser irradiation unit 2. Then, the reflected light detector 5 detects the light intensity of the reflected light from the processing point of the workpiece 4 to determine whether the processing state is abnormal. In accordance with this, the laser beam detector 6 detects the leakage light of the laser beam from the laser welding machine main body 1 to determine whether the optical path state in the laser irradiation unit 2 is good or bad.
JP 2006-247681 A

  However, since the conventional configuration requires a plurality of photodetectors, the number of optical components increases, and the configuration is complicated.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a laser processing apparatus with a monitoring function and a laser processing method with a small number of optical components and a simple mechanism.

In order to achieve the above object, a laser processing apparatus of the present invention is arranged between a laser emitting unit, a detecting unit arranged on an optical axis of the laser emitting unit, and the laser emitting unit and the detecting unit. A half mirror, an optical system for condensing light from the half mirror, a housing for holding the laser emitting unit, the detection unit, the half mirror, and the optical system, and detection by the detection unit A reflected light from the workpiece reflected by the inner wall surface of the laser irradiation unit, and a measuring device for determining the machining state of the workpiece based on the light, and cutting the visible light on the detection surface of the detection unit A filter is provided , and the inner wall surface of the housing is black anodized .

  As described above, according to the laser processing apparatus and the laser processing method of the present invention, it is possible to provide a laser processing apparatus with a monitoring function and a laser processing method with a small number of optical components and a simple mechanism.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals and description thereof is omitted.

(Embodiment 1)
FIG. 1 is a schematic diagram of a laser processing apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, a laser processing apparatus 7 according to the present embodiment includes a laser oscillator 8 that oscillates and generates laser light, a laser torch 9 (laser irradiation unit) installed at a desired processing position, a laser oscillator 8 and a laser torch 9. It comprises an optical fiber 10 that is optically connected, a measuring device 11 that performs signal processing on the electrical signal detected and output by the laser torch 9, and determines the quality of the processing state, and a controller 12 that controls the entire laser processing device 7. The Then, the laser beam from the laser torch 9 is irradiated to the processing point 14 of the workpiece 13 (workpiece) to perform processing, and the quality of the processing state is monitored and determined.

  Each component of the laser processing apparatus 7 is demonstrated in detail.

  The laser oscillator 8 oscillates and generates laser light based on the control of the controller 12. The laser oscillator 8 in the present embodiment oscillates and generates a pulsed YAG laser having a wavelength of 1064 nm.

  The laser torch 9 includes a laser emitting unit 15 that emits laser light from the optical fiber 10 as diffused laser light, a half mirror 16 that reflects the laser light from the laser emitting unit 15 toward the processing point 14 of the workpiece 13, and a half A lens 17 for converting the laser light reflected by the mirror 16 into parallel light, a lens 18 for condensing the parallel light from the lens 17 and irradiating the processing point 14, and measuring the light intensity of the incident light as an electrical signal It comprises a detection unit 19 that outputs, a case 20 that holds the laser emitting unit 15, the half mirror 16, the lens 17, and the detection unit 19, and an irradiation unit case 21 that holds the lens 18 (and the lens 17). The On the detection surface of the detection unit 19, a neutral density filter 22 having a property of weakening the light intensity of the light incident on the detection unit 19 and visible light (light having a visible wavelength) out of the light incident on the detection unit 19. ) And a visible light cut filter 23 having a property of cutting. In the present embodiment, since the laser light from the laser emitting unit 15 has a wavelength other than visible light, the visible light cut filter 23 has a property of transmitting light having the same wavelength as the laser emitted light.

  The measuring device 11 has a function of capturing an electrical signal from the detection unit 19 as numerical data during laser processing, and compares the time series data of the captured electrical signal with data during normal laser processing to determine whether the processing state is good or bad. It has the function to determine. Details of the determination method will be described later. In addition to determining the quality of the machining state, the measuring device 11 also determines the quality of the equipment state (the optical path state of the laser torch 9) based on the time series data of the captured electric signal. The measuring device 11 also has a function of recording data at the time of normal laser processing.

  The controller 12 is for controlling the laser output of the laser oscillator 8. As a specific control method, the laser output is controlled based on the signal received from the measuring device 11. The controller 12 has a function of stopping the output of the laser oscillator 8 when receiving a signal indicating the machining state NG (not) from the measuring device 11.

  The workpiece 13 is formed by stacking a plurality of plate-like materials having a property of reflecting light. In this embodiment, a stack of two 1 mm thick SUS plates is used.

  The processing point 14 is a predetermined region of the work 13 and is a part where physical properties are denatured by irradiation with laser light.

  The half mirror 16 has a property of reflecting the laser light from the laser emitting portion 15 to the processing point 14 while transmitting the reflected light reflected by the processing point 14.

  The lenses 17 and 18 are optical systems arranged so that the laser light reflected by the half mirror 16 is collimated by the lens 17 and then condensed on the processing point 14 by the lens 18. In the present embodiment, the optical system also has a function of condensing the laser light reflected from the processing point 14 by the lens 17 after making the laser light parallel by the lens 18.

  The detection unit 19 converts the light intensity of incident light into an electrical signal. In this embodiment, the machining state is detected by detecting the reflected light from the workpiece 13, and the equipment state (the optical path state of the laser torch 9) is also detected by detecting the leakage light of the laser beam from the laser emitting unit 15. Used to detect. In the present embodiment, in order to detect the scattered light of the reflected light from the work 13, it is desirable that the detection unit 19 is not disposed on the optical axis of the reflected light from the work 13. The detection of the reflected light from the work 13 is performed by detecting the irregularly reflected light (scattered light) on the inner wall surface of the housing 20, which will be described in detail later.

  The casing 20 is obtained by performing black alumite (aluminum anodization) treatment on the inner wall surface in order to weaken the irregular reflection of the laser beam. By performing the black alumite treatment, the corrosion resistance of the inner wall surface can be improved and the reflected light from the work 13 can be guided to the detection unit 19 by being reflected.

  As for the inner wall surface, if the reflectance is high, strong irregular reflection of light occurs in the housing 20, and the device having the conventional configuration absorbs light. For this reason, as in this embodiment, the inventors have studied various conditions for generating reflected light (scattered light) with an appropriate intensity, and have found that it is desirable to perform black alumite treatment. . By using the inner wall surface subjected to the black alumite treatment as a reflection surface, it is possible to weaken the light intensity at the time of irregular reflection of the laser light to an appropriate intensity. However, since monitoring is performed using irregularly reflected light of laser light, it is necessary not to perform black alumite treatment that completely absorbs light.

  Next, details of the measurement apparatus 11 of FIG. 1 will be described using a block diagram.

  FIG. 2 is a block diagram of the measuring apparatus 11 according to the first embodiment.

  In FIG. 2, the electrical signal from the detection unit 19 is taken into the measurement calculation unit 24 of the measurement device 11 and stored as time-series data of the light intensity measurement values. Then, the time series data of the light intensity measurement values at the time of normal processing stored in the reference waveform storage unit 25 is read, and the comparison with the measured time series data is performed by the comparison unit 26.

  This comparison method will be described in detail. First, when comparing, it is necessary to set conditions for comparison. Therefore, the monitor section (time section) for comparison is stored in the monitor section setting unit 27. Further, the comparison method such as the reference, threshold value, and condition to be compared is stored in the comparison method setting unit 28. Then, the comparison unit 26 compares the measured time series data with the time series data at the time of normal machining, using the monitor section and the comparison method read from the monitor section setting unit 27 and the comparison method setting unit 28.

  Then, based on the comparison result in the comparison unit 26, the machining state determination unit 29 determines the quality of the machining state. Then, laser irradiation is performed by appropriately adjusting based on the quality determination in the processing state determination unit 29. Here, when the machining state is OK (good), the workpiece 13 is irradiated with laser under the same conditions. Further, in the case of the machining state NG (No), the controller 30 creates a notification signal for changing the laser irradiation condition by the controller 12 and transmits a signal from the measuring device 11 to the controller 12, so that the laser irradiation condition Irradiate with laser.

  Next, a monitoring method using the laser processing apparatus shown in FIG. 1 will be described.

  FIG. 3 is a diagram illustrating a flow of the laser processing monitoring method according to the first embodiment.

  First, the laser light emitted from the laser emitting unit 15 from the laser oscillator 8 through the optical fiber 10 is reflected by the half mirror 16, converted into parallel light by the lens 17, and condensed by the lens 18 to process the workpiece 13. The point 14 is irradiated with laser (step S1).

  Subsequently, the reflected light reflected by the work 13 passes through the lenses 18, 17, and the half mirror 16 in order, and then the scattered light is irregularly reflected by the inner wall surface of the case 20 that has been black anodized, and the laser output unit 15 to the half mirror 16. The mixed light with the laser emission light that has passed through is detected by the detection unit 19 (step S2).

  Subsequently, A / D conversion of the signal detected in step S2 is performed using an A / D conversion board (not shown) (step S3).

  Subsequently, the comparison unit 26 of the measurement apparatus 11 compares the waveform measured by the above-described comparison method with the waveform during normal machining (step S4).

  Subsequently, the processing state determination unit 29 of the measuring device 11 determines whether the processing state is good (OK / NG) (step S5).

  Subsequently, if the machining state is OK (good) in step S5, laser irradiation can be performed under the same conditions, so the process returns to step S1 and laser irradiation is performed again.

  In the case of the processing state NG (No) in step S5, the laser irradiation condition needs to be changed. Therefore, the processing state is notified from the measuring device 11 to the controller 12, and the laser irradiation condition is changed by the controller 12 (step S5). S6).

  Subsequently, after changing the conditions in step S6, the process returns to step S1 to perform laser irradiation.

  By repeating these steps, laser irradiation is performed while monitoring the laser processing state. Here, the reason why the laser irradiation (step S1) is performed a plurality of times is that welding is performed by a plurality of times of laser irradiation, assuming that the specific processing content is welding.

(Embodiment 2)
The present embodiment is for performing a factor analysis of a machining (welding) process using the laser processing apparatus described in the first embodiment, defining an algorithm, and performing an automatic analysis. About the apparatus and method, since the thing similar to Embodiment 1 is used, description is abbreviate | omitted.

  FIG. 4 is an enlarged view of the vicinity of the laser torch 9 of the second embodiment. In FIG. 4, three types of five items A1, A2, B1, B2, and C are defined as the obstruction factors of the machining process, and each occurrence location is added to the drawing. Hereinafter, each inhibition factor will be described.

  When the optical fiber 10 is deteriorated (A1 in FIG. 4), or when foreign matter or dirt is attached to the lenses 17, 18 and the protective glass (not shown) (A2 in FIG. 4), the laser optical path In this case, laser light scattering occurs (this is assumed as factor A).

  When the optical fiber 10 is disconnected (disconnected) (B1 in FIG. 4), or when the height or position of the workpiece 13 is shifted (B2 in FIG. 4), the laser focusing system ( Condensation deviation occurs in the detection unit 19 or the like (this is assumed to be factor B).

  When foreign matter or dirt adheres to the workpiece surface, noise is generated in the detection result (this is assumed as factor C).

  In order to consider these obstruction factors separately, in the present embodiment, using the apparatus of the first embodiment, the scattered light generated on the surface of the workpiece 13 and the laser torch 9 is captured by the detection unit 19 (light sensor), The waveform intensity was analyzed in detail. Thereby, it becomes possible to detect an obstruction factor of the machining (welding) process and inspect the machining defect.

  In the present embodiment, the light intensity of the scattered light captured by the detection unit 19 and the value of a power meter (not shown) installed in the laser emission unit 15 are sampled at a sampling rate of 50 by an A / D conversion board. Consider a case where data is captured at a resolution of 32,768 gradations (16 bits) at 2,000 points / second (sampling interval 20 μs).

  In the present embodiment, the characteristics of the scattered light waveform are analyzed when the factors A, B, and C are inhibited under the above-described conditions.

  FIG. 5A is a diagram illustrating the light intensity of the laser beam output from the laser oscillator 8 according to the second embodiment, and FIG. 5B is a diagram illustrating normality due to reflected light from the workpiece 13 according to the second embodiment. It is a figure which shows the scattered light intensity at the time. 5A and 5B, the vertical axis indicates the light intensity, and the horizontal axis indicates the time.

  As shown in FIG. 5A, in the present embodiment, the light intensity of the laser light from the laser oscillator 8 has a relatively simple waveform. As shown in FIG. 5A, after a large power is first applied and the metal of the workpiece 13 is melted, a triangular waveform whose strength decreases with time to suppress sputtering is obtained. For this waveform, it is necessary to appropriately determine the strength and time depending on the characteristics of the object to be processed (welded), and in some cases, it is also necessary to change the waveform shape itself. In the present embodiment, welding is performed by hitting a spot weld having such a waveform a plurality of times.

  Region D in FIG. 5B is a phenomenon that occurs because the reflectance of the laser beam is high until the metal is melted when the metal surface of the workpiece is irradiated with the laser beam. Such a feature is a feature that can be seen only during the first irradiation among a plurality of times of laser irradiation, and is an important feature in determining a processing (welding) defect.

  The inventor confirmed by experiments the state of waveform change when the above-described factors A, B, and C were added to the normal waveform. This situation will be described.

  FIG. 6A is a diagram showing a waveform change due to the factor A in the second embodiment, and FIG. 6B is a diagram showing a waveform change due to the factor B in the second embodiment, and FIG. ) Is a diagram showing a waveform change due to the factor C in the second embodiment. 6A to 6C, the vertical axis represents the light intensity, and the horizontal axis represents the time.

  FIG. 6A shows the waveform change due to the factor A, which is divided into two cases. In the first case, the scattered light intensity is increased by scattering the laser beam due to foreign matters existing in the laser beam path, dirt on the protective glass, or the like. The second case is a case where the scattered light also decreases due to a decrease in the intensity of the laser beam entering the laser torch due to the deterioration of the optical fiber. These are characterized in that the size changes in any case while maintaining the shape of the waveform at the normal time.

  FIG. 6B shows a waveform change due to factor B. FIG. Since the laser beam is not focused on the processing point, the shape of the peak point of the scattered light changes. As a result, a time delay (deviation on the horizontal axis), a decrease in light intensity (decrease on the vertical axis), and deformation of the waveform shape are observed.

  FIG. 6C shows a waveform change due to the factor C. FIG. Since the laser beam is absorbed by the foreign matter on the workpiece surface, the initial peak decreases, but the scattered light thereafter increases. In the experiment in the present embodiment, the scattered light intensity at the peak is reduced because the foreign matter absorbed the laser beam. However, the same result may not be obtained depending on the characteristics of the attached foreign matter. It is considered that the accuracy of analysis is further improved by analyzing the materials and the like and examining the characteristics based on them.

  The inventor classified the factors of processing (welding) defects based on the experimental results obtained in FIGS. The results are summarized in FIGS. 7 (a) and 7 (b).

  FIG. 7A is a diagram for explaining a first algorithm for laser processing monitoring, and FIG. 7B is a diagram for explaining a second algorithm for laser processing monitoring.

  Here, the laser processing monitoring is an algorithm for evaluating the scattered light waveform, and its basic idea is based on comparison with a normal waveform (reference waveform) as described in the first embodiment. It is something to evaluate. Evaluate the size of the area (light intensity x time) outside the allowable range set around the predetermined threshold or the reference waveform, and detect a case where a predetermined condition is exceeded as a processing (welding) defect To do.

  FIG. 7A shows a basic processing standard of the evaluation algorithm. Here, as shown in FIG. 7A, the entire waveform is divided into three types of areas. In the peak detection area, the peak height is compared with the reference waveform. In the waveform comparison area, the area outside the allowable range is measured, and the quality is determined based on the size of the area. In the present embodiment, the invalid area is not used for the determination because the influence of the obstruction factor is small. By comparing the peak height with the area, it is possible to detect a processing defect caused by the above-described factors A and C. By using this criterion, the first algorithm is constructed. Since the division criteria and reference waveforms of these three areas differ depending on the type of workpiece and laser, they are appropriately determined according to them. In the present embodiment, the entire waveform is divided into three types of areas. However, these areas can be divided into other types of areas, and a plurality of areas overlap. You may use the state. These need to be appropriately determined depending on the measurement object and the determination criteria.

  FIG. 7B is an algorithm for detecting the waveform shape of the peak position and the time delay by paying attention to the characteristic part as in the region D of FIG. 5B. When the laser beam is focused on the processing point of the workpiece, the processing defect is detected by utilizing the fact that the peak of the scattered light is delayed in time when the laser beam is not focused. Thereby, it is possible to detect a machining defect caused by the factor B. By using this criterion, the second algorithm is constructed.

  By using these algorithms in combination, automatic analysis (automatic monitoring) becomes possible.

  Note that in the creation of the reference waveform, the normal waveform also fluctuates within a certain range. Therefore, it is desirable for the monitoring device to have a function of collecting and accumulating waveforms during normal machining of the workpiece and calculating an allowable range from the reference waveform and the dispersion value for the average value of the waveform data for a predetermined number of times. As a result, the reference waveform and the allowable range can be calculated relatively easily.

  By using the present invention, it is possible to provide a laser processing apparatus and a laser processing method with a simple configuration, and therefore, the present invention can be applied to in-line laser processing state inspection.

Schematic diagram of laser processing apparatus of Embodiment 1 Block diagram of measuring apparatus 11 according to Embodiment 1 The figure which shows the flow of the laser processing monitoring method of Embodiment 1. Enlarged view of the vicinity of the laser torch 9 of the second embodiment (A) The figure which shows the light intensity of the laser beam output from the laser oscillator 8 of Embodiment 2, (b) The figure which shows the scattered light intensity at the time of the normal by the reflected light from the workpiece | work 13 of Embodiment 2. (A) The figure which shows the waveform change by the factor A in Embodiment 2, (b) The figure which shows the waveform change by the factor B in Embodiment 2, (c) The figure which shows the waveform change by the factor C in Embodiment 2. (A) The figure explaining the 1st algorithm of laser processing monitoring, (b) The figure explaining the 2nd algorithm of laser processing monitoring Schematic of the laser processing monitoring device of Patent Document 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser welding machine main body 2 Laser irradiation unit 3 Unit main body 4 Work piece 5 Reflected light detector 6 Laser light detector 7 Laser processing apparatus 8 Laser oscillator 9 Laser torch 10 Optical fiber 11 Measuring apparatus 12 Controller 13 Work 14 Processing point 15 Laser emitting part 16 Half mirror 17, 18 Lens 19 Detection unit 20 Housing 21 Irradiation unit housing 22 Neutral filter 23 Visible light cut filter 24 Measurement calculation unit 25 Reference waveform storage unit 26 Comparison unit 27 Monitor section setting unit 28 Comparison method setting unit 29 Machining state determination unit 30 Control unit

Claims (4)

A laser emitting part;
A detection unit disposed on the optical axis of the laser emission unit;
A half mirror disposed between the laser emitting unit and the detecting unit;
An optical system for condensing the light from the half mirror;
A housing for holding the laser emitting unit, the detecting unit, the half mirror, and the optical system;
The reflected light from the workpiece detected by the detection unit is reflected by the inner wall surface of the laser irradiation unit, and includes a measuring device that determines the processing state of the workpiece based on the light ,
A laser processing apparatus , wherein a visible light cut filter is provided on a detection surface of the detection unit, and an inner wall surface of the housing is black anodized . The determination of the machining state in the measuring device is performed by determining a peak detection area and a waveform comparison area according to the detection time of the light reflected from the workpiece detected by the detection unit and reflected from the inner wall surface of the laser irradiation unit. and it classifies the detected result to the three areas of the disabled area, the laser processing apparatus according to claim 1, wherein the benzalkonium be determined in criterion corresponding to the respective areas. The determination of the machining state by the measuring device is performed by comparing the detection result of the light reflected from the workpiece and detected by the detection unit with the reference waveform with the reference waveform. position or based on the area due to the deviation between the reference waveform, the laser machining apparatus according to any one of claims 1 to 2, wherein the benzalkonium be determined by classifying the cause. The laser processing apparatus according to any one of claims 1 to 3, characterized in that a neutral density filter on the detection surface of the detector.

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