Laser processing device and evaluation method

Abstract

To easily maintain evaluation accuracy.SOLUTION: A laser processing device having a function of evaluating a quality of a laser process includes: an oscillator that oscillates a laser beam; a mirror that is disposed in an optical path of the laser beam, wherein while transmitting a first laser beam, which is a part of the laser beam emitted from the oscillator, the mirror reflects a second laser beam, which is another part of the laser beam, emits the second laser beam to a to-be-processed portion, and transmits first reflected light, which is a part of a reflected light obtained by causing the second laser beam, emitted to the to-be-processed portion, to reflect off the to-be-processed portion; an absorbing portion that receives the first laser beam and absorbs the first laser beam until the first laser beam has a predetermined amount of light or smaller; a sensor unit that measures an intensity of the first reflected light transmitted through the mirror; and a quality evaluation unit that outputs an evaluation result indicating the quality of the laser process in the processed portion, based on a measurement result of the intensity of the first reflected light measured by the sensor unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a laser processing apparatus and an evaluation method. [Background technology]

[0002] As described in Patent Document 1, in the past, in order to evaluate the welding quality in a laser processing device, the measurement results of the intensity of thermal radiation light emitted from a welding portion of a welding target by irradiating it with laser light have been used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-58927 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to accurately measure the intensity of the thermal radiation light, it is necessary that the irradiation range of the laser light is within the field of view of the sensor, and that the focused diameter of the laser light and the field of view of the sensor are aligned. For example, if the field of view of the sensor is larger than the irradiation range of the laser light, the thermal radiation light generated from the molten pool near the irradiation range of the laser light is also measured. In this case, the thermal radiation light in the irradiation range of the laser light cannot be accurately measured, and the evaluation accuracy decreases. Therefore, in order to maintain the evaluation accuracy, it is essential to accurately match the field of view of the sensor with the focused diameter of the laser light, and a laser processing device that can easily maintain the evaluation accuracy has been demanded. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms. According to one embodiment of the present disclosure, a laser processing apparatus is provided, which is a laser processing apparatus having a function of evaluating the quality of laser processing using only the intensity of reflected laser light, and which comprises an oscillator for oscillating a laser beam, and a mirror arranged in an optical path of the laser beam, which transmits a first laser beam, which is a part of the laser beam emitted from the oscillator, and has a reflection wavelength range that is a wavelength range in a predetermined range centered on a central wavelength of the laser beam, while reflecting a second laser beam, which is another part of the laser beam, and has the reflection wavelength range, to irradiate the second laser beam to a processing target portion, and the second laser beam irradiated to the processing target portion is reflected by the second laser beam. a sensor unit that measures the intensity of the first reflected light that is reflected by the area to be processed and transmitted through the mirror; an absorbing unit that prevents the first laser light from being incident on the sensor unit by absorbing the first laser light that has transmitted through the mirror and entered the area to be processed without being reflected by the area to a predetermined light amount or less; and a quality evaluation unit that outputs an evaluation result that indicates the quality of the laser processing of the area to be processed based on a measurement result of the intensity of the first reflected light measured by the sensor unit. In the laser processing apparatus according to the above embodiment, the absorbing section is a cylindrical member into which the first laser light is incident, the cylindrical member having an inner surface that is black anodized, and one end of which is closed. The cylindrical member may include a first straight portion, a first bent portion, a second straight portion, a second bent portion, and a third straight portion, the first straight portion extending along the optical path of the laser light emitted from the oscillator, the second straight portion extending in a direction intersecting the direction in which the first straight portion extends, the first bent portion connecting the first straight portion and the second straight portion, the second bent portion connecting the second straight portion and the third straight portion, the third straight portion extending in a direction intersecting the direction in which the second straight portion extends, and is formed in a tapered shape so as to gradually become thinner toward an end, and the end of the third straight portion may be closed. According to another embodiment of the present disclosure, there is provided an evaluation method for evaluating the quality of laser processing by a laser processing device using only the intensity of reflected laser light. The laser processing device includes an oscillator that oscillates a laser beam, a mirror that is arranged in a light path of the laser beam, and transmits a first laser beam that is a part of the laser beam emitted from the oscillator and has a reflection wavelength range that is a wavelength range in a predetermined range centered on a central wavelength of the laser beam, while reflecting a second laser beam that is another part of the laser beam and has the reflection wavelength range, so that the second laser beam is irradiated to a processing target portion, and transmits a first reflected light that is a part of the reflected light that is the light reflected by the processing target portion from the second laser beam irradiated to the processing target portion, a sensor unit that measures the intensity of the first reflected light that is reflected by the processing target portion and transmitted through the mirror, and an absorbing unit that absorbs the first laser beam that is transmitted through the mirror and enters the processing target portion without being reflected by the processing target portion until the first laser beam is equal to or less than a predetermined light amount, thereby preventing the first laser beam from being incident on the sensor unit. This evaluation method causes a computer to execute the steps of receiving a measurement result of the intensity of the first reflected light measured by the sensor unit, evaluating the quality of the laser processing at the area to be processed based on the measurement result, and outputting an evaluation result representing the quality. (1) According to one embodiment of the present disclosure, there is provided a laser processing apparatus having a function of evaluating the quality of laser processing, the laser processing apparatus comprising an oscillator that oscillates a laser beam, and a mirror disposed in a light path of the laser beam, the mirror transmitting a first laser beam that is a part of the laser beam emitted from the oscillator, and reflecting a second laser beam that is another part of the laser beam, so that the second laser beam is irradiated onto a processing target portion; The laser processing device includes a mirror that transmits first reflected light, which is a portion of the reflected light that is the second laser light irradiated to the area to be processed and reflected from the area to be processed; an absorption section that receives the first laser light and absorbs it until the amount of light is equal to or less than a predetermined amount of light; a sensor section that measures the intensity of the first reflected light that has transmitted through the mirror; and a quality evaluation section that outputs an evaluation result that indicates the quality of the laser processing at the area to be processed based on the measurement result of the intensity of the first reflected light measured by the sensor section. According to the above embodiment, the first laser light emitted from the oscillator that passes through the mirror is absorbed until the amount of light is equal to or less than a predetermined amount, and does not enter the sensor unit. The quality evaluation unit evaluates the quality of the laser processing at the processing target portion based on the intensity of the first reflected light reflected at the processing target portion. Compared to an embodiment in which the quality of the laser processing is evaluated using thermal radiation light, it is not necessary to precisely align the field of view of the sensor with the focused diameter of the laser, making it easier to maintain the evaluation accuracy. (2) In the laser processing apparatus described in the above aspect, the absorbing section may be a cylindrical member into which the first laser light is incident, the cylindrical member having an inner surface that is black anodized and one end of which is closed. According to the above embodiment, the first laser light incident on the cylindrical member of the absorbing unit is attenuated as it is repeatedly reflected. With this simple configuration, the first laser light transmitted through the mirror can be attenuated until it becomes equal to or less than a predetermined light amount. (3) According to another aspect of the present disclosure, there is provided a method for evaluating the quality of laser processing by a laser processing device. The laser processing device includes an oscillator that oscillates a laser beam, a mirror that is disposed in a light path of the laser beam, and transmits a first laser beam that is a part of the laser beam emitted from the oscillator, while reflecting a second laser beam that is another part of the laser beam, so that the second laser beam is irradiated to a processing target portion, and transmits a first reflected light that is a part of the reflected light that is the light that is reflected by the processing target portion from the second laser beam irradiated to the processing target portion, an absorbing section that receives the first laser beam and absorbs the first laser beam until the amount of the first reflected light is equal to or less than a predetermined amount of light, and a sensor section that measures the intensity of the first reflected light that has passed through the mirror. This evaluation method causes a computer to execute the steps of receiving a measurement result of the intensity of the first reflected light measured by the sensor section, evaluating the quality of the laser processing at the processing target portion based on the measurement result, and outputting an evaluation result that indicates the quality. According to the above embodiment, the first laser light emitted from the oscillator that passes through the mirror is absorbed until the amount of light is equal to or less than a predetermined amount, and does not enter the sensor unit. The quality evaluation unit evaluates the quality of the laser processing at the processing target portion based on the intensity of the first reflected light reflected at the processing target portion. Compared to an embodiment in which the quality of the laser processing is evaluated using thermal radiation light, it is not necessary to precisely align the field of view of the sensor with the focused diameter of the laser, making it easier to maintain the evaluation accuracy. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a laser welding device. [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of a damping structure. [Diagram 3] 1 is a schematic diagram showing the path of reflected light until it reaches a measurement unit in a laser processing device equipped with an attenuation structure. [Figure 4] 1 is a schematic diagram showing the path of reflected light until it reaches a measurement unit in a laser processing device that does not have an attenuation structure. [Diagram 5] 1 is a flowchart showing a method for evaluating the quality of welding performed by a laser welding device. [Figure 6] 11 is a diagram showing an example of the positional relationship between a laser focusing diameter and a sensor field of view; FIG. [Figure 7] 13 is a diagram showing another example of the positional relationship between the laser focusing diameter and the sensor field of view. FIG. [Figure 8] 13 is a diagram showing yet another example of the positional relationship between the laser focusing diameter and the sensor field of view. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] A. Embodiment FIG. 1 is a diagram showing a schematic configuration of a laser welding apparatus 100. In FIG. 1, an XYZ Cartesian coordinate system is set in order to facilitate understanding of the technology. The X-axis and the Y-axis are assumed to be along a horizontal plane, and the Z-axis is assumed to be along a vertical line. Therefore, the -Z direction is the direction of gravity. The laser welding apparatus 100 welds the first metal object Wa and the second metal object Wb, which are stacked, by irradiating the first metal object Wa and the second metal object Wb with a laser light LB. The first metal object Wa and the second metal object Wb are collectively referred to as a workpiece WK. The laser welding apparatus 100 is also referred to as a laser processing apparatus. The laser welding apparatus 100 evaluates the quality of the weld based on the intensity of the reflected light RB, which is the laser light LB reflected by the workpiece WK. In FIG. 1, in order to facilitate understanding of the technology, the optical path of the laser light LB and the optical path of the reflected light RB are shown shifted from each other. The laser welding apparatus 100 includes a laser oscillator 10 , an optical fiber cable 11 , a laser scanner 20 , a measuring section 30 , an attenuation structure 40 , a control section 60 , an input device 61 , and a display device 62 .

[0008] The laser oscillator 10 outputs laser light LB generated by laser oscillation. The laser oscillator 10 is, for example, a fiber laser. The laser oscillator 10 is connected to a laser scanner 20 via an optical fiber cable 11. The laser oscillator 10 is also called an oscillator.

[0009] The laser scanner 20 irradiates the laser light LB outputted by the laser oscillator 10 onto the workpiece WK to be processed. The laser scanner 20 is attached to the tip of a robot arm (not shown). The laser scanner 20 is moved to a target welding position of the workpiece WK by the robot arm. Note that the robot arm can move the laser scanner 20 to a specified position and arrange it in a specified orientation by driving each joint of the robot arm by a robot controller (not shown). The laser scanner 20 includes an optical isolator 205, an optical system 210, a Z lens driving unit 220, a galvano scanner unit 230, and a protective glass 240.

[0010] The optical isolator 205 passes the laser light LB emitted from the end face of the optical fiber cable 11 and prevents the reflected light RB from entering the laser oscillator 10. The optical isolator 205 is connected to the laser oscillator 10 via the optical fiber cable 11.

[0011] The optical system 210 guides the laser light LB to travel a determined optical path. The optical system 210 includes a collimator lens 211, a dichroic mirror 212, a first reflecting mirror 213, a diffractive optical element (DOE) 214, a Z lens 215, a second reflecting mirror 216, and a condenser lens 217. The collimator lens 211 is a lens for correcting the laser light LB to a parallel light.

[0012] The dichroic mirror 212 is a mirror that reflects light in a specific wavelength range and transmits light in other wavelength ranges. The dichroic mirror 212 is also called a mirror. In the embodiment, the dichroic mirror 212 reflects light in a determined wavelength range centered on the central wavelength of the laser light LB output by the laser oscillator 10, and transmits light in other wavelength ranges. The wavelength range reflected by the dichroic mirror 212 is called a reflected wavelength range. In the embodiment, the reflected wavelength range is a wavelength range in a determined range centered on the central wavelength of the laser light LB. The central wavelength of the laser light LB is, for example, 1070 nm. However, the dichroic mirror 212 cannot completely reflect light in the reflected wavelength range. For example, the reflectance of the reflected wavelength range in the dichroic mirror 212 is 99.9%, and the transmittance of the reflected wavelength range is 0.1%. In other words, 0.1% of the light in a specific wavelength range that is incident on the dichroic mirror 212 is transmitted through the dichroic mirror 212. The laser light LB in the part of the reflected wavelength range that is transmitted through the dichroic mirror 212 is also referred to as a first laser light. The laser light LB in the part of the reflected wavelength range that is reflected by the dichroic mirror 212 is also referred to as a second laser light.

[0013] The first reflecting mirror 213 and the second reflecting mirror 216 are total reflection mirrors. The diffractive optical element 214 is an optical element for adjusting the shape of the laser light LB.

[0014] The Z lens driving unit 220 moves the Z lens 215 to change the focal position of the laser light LB. The Z lens driving unit 220 has a movement mechanism for moving the position of the Z lens 215 in the optical axis direction, and a driver for driving the movement mechanism.

[0015] The galvano scanner unit 230 changes the focal point of the laser light LB by changing the angle of a built-in reflecting mirror. The galvano scanner unit 230 has a reflecting mirror that reflects the laser light LB, an angle changing mechanism that changes the angle of the reflecting mirror, and a driver that drives the angle changing mechanism. The galvano scanner unit 230 changes the focal point of the laser light LB, thereby changing the irradiation position of the laser light LB on the workpiece WK.

[0016] The protective glass 240 is a lens provided at the output port of the laser scanner 20 for the laser light LB in order to protect the optical system 210 included in the laser scanner 20.

[0017] The laser light LB emitted from the laser oscillator 10 travels along the following optical path in the laser scanner 20. The laser light LB emitted from the laser oscillator 10 enters the laser scanner 20 via the optical fiber cable 11. The laser light LB that passes through the optical isolator 205 is corrected to a parallel light by the collimator lens 211. The laser light LB is reflected by the dichroic mirror 212 and the first reflecting mirror 213, and enters the diffractive optical element 214. The diffractive optical element 214 emits the incident laser light LB as a laser light LB having a power density distribution shape different from that at the time of incidence. The emitted laser light LB passes through the Z lens 215, the position of the optical axis of which is adjusted by the Z lens driving unit 220. Thereafter, the laser light LB is reflected by the second reflecting mirror 216, passes through the condenser lens 217, and enters the galvano scanner unit 230. The galvano scanner unit 230 adjusts the focal point of the laser light LB. The laser light LB emitted from the galvano scanner unit 230 is irradiated onto the workpiece WK through the protective glass 240. When the laser light LB is irradiated onto the workpiece WK, the metal melts and a molten pool is formed.

[0018] Furthermore, the reflected light RB, which is the result of reflection of the laser light LB irradiated to the workpiece WK, travels along the following optical path in the laser scanner 20. The reflected light RB is also called the first reflected light. The reflected light RB passes through the protective glass 240 and enters the laser scanner 20. The reflected light RB passes through the galvano scanner unit 230 and the condenser lens 217, and is reflected by the second reflecting mirror 216. Thereafter, the reflected light RB passes through the Z lens 215 and the diffractive optical element 214, and is reflected by the first reflecting mirror 213.

[0019] Thereafter, a part of the reflected light RB is reflected by the dichroic mirror 212, and another part of the reflected light RB is transmitted through the dichroic mirror 212. Since the reflected light RB has the same wavelength as the laser light LB, 99.9% of the reflected light RB incident on the dichroic mirror 212 is reflected by the dichroic mirror 212. 0.1% of the reflected light RB incident on the dichroic mirror 212 is transmitted through the dichroic mirror 212.

[0020] A portion of the reflected light RB reflected by the dichroic mirror 212 travels in the +Z direction, passes through the collimator lens 211, and heads toward the optical isolator 205. The travel of the reflected light RB is blocked by the optical isolator 205. Therefore, the reflected light RB does not enter the laser oscillator 10. Note that the optical path of the reflected light RB from the dichroic mirror 212 to the optical isolator 205 is not shown in FIG. 1. Another portion of the reflected light RB transmitted by the dichroic mirror 212 travels in the +X direction and enters the measurement unit 30.

[0021] The measurement unit 30 measures the intensity of the reflected light RB of the laser light LB irradiated to the workpiece WK. The measurement unit 30 is also called a sensor unit. The measurement unit 30 includes a bandpass filter 31, a third reflecting mirror 32, and a photoelectric element 33. The bandpass filter 31 transmits only light in a predetermined range of wavelengths centered on a specified central wavelength. In the embodiment, the bandpass filter 31 transmits only light in a predetermined range of wavelengths centered on the central wavelength of the laser light LB emitted by the laser oscillator 10. The third reflecting mirror 32 reflects the reflected light RB incident on the measurement unit 30 and causes the reflected light RB to travel toward the photoelectric element 33. The third reflecting mirror 32 is a total reflection mirror. The photoelectric element 33 is used to measure the intensity of the reflected light RB. Specifically, the photoelectric element 33 converts the incident reflected light RB into an electrical signal and outputs the electrical signal indicating the intensity of the reflected light RB to the control unit 60. The photoelectric element 33 is, for example, a photodiode or a phototransistor.

[0022] The attenuation structure 40 receives a portion of the laser light LB that is in the reflection wavelength range and that has passed through the dichroic mirror 212, and absorbs it until the amount of light becomes equal to or less than a predetermined amount. The damping structure 40 is also called an absorbing portion.

[0023] FIG. 2 is a diagram showing a schematic configuration of the damping structure 40. The damping structure 40 is a member formed in a cylindrical shape with one end open. The damping structure 40 is made of aluminum, for example. The damping structure 40 includes a first straight portion 42, a first bent portion 43, a second straight portion 44, a second bent portion 45, a third straight portion 46, and a terminal portion 47. The first straight portion 42 is a passage extending along the Z-axis direction. The end of the first straight portion 42 on the +Z side is open.

[0024] A surface 212b of the dichroic mirror 212 opposite to the surface 212a on which the laser light LB is incident is disposed at an angle of 45 degrees with respect to the opening at the end on the +Z side of the first straight section 42. In addition, the surface 212b of the dichroic mirror 212 is disposed at an angle of 45 degrees with respect to the open end of the cylindrical member 30a of the measurement unit 30. Therefore, at least a part of the light transmitted through the dichroic mirror 212 in the -Z direction enters the attenuation structure 40. In addition, at least a part of the light transmitted through the dichroic mirror 212 in the +X direction enters the measurement unit 30.

[0025] The first bent portion 43 connects the first straight portion 42 and the second straight portion 44. The second straight portion 44 is a passage extending in the X-axis direction. The second bent portion 45 connects the second straight portion 44 and the third straight portion 46. The third straight portion 46 is a passage extending along the Z-axis direction. The third straight portion 46 includes a portion formed in a tapered shape so as to gradually become thinner toward the terminal portion 47. For example, the third straight portion 46 is formed in the shape of a triangular pyramid. The terminal portion 47 is located on the -Z side of the third straight portion 46 and is a closed end.

[0026] The inner surface of the damping structure 40 is black anodized. The anodized treatment is a surface treatment that generates an oxide film on the surface of aluminum. The black anodized treatment is a treatment that turns the oxide film black using a black dye after the anodized treatment.

[0027] A part of the laser light LB incident on the surface 212a of the dichroic mirror 212 passes through the dichroic mirror 212, travels in the -Z direction, and enters the inside of the attenuation structure 40. The laser light LB travels toward the end portion 47 of the attenuation structure 40 while repeatedly reflecting on the inner surface of the attenuation structure 40. The laser light LB incident on the attenuation structure 40 is absorbed by the inner surface that has been black anodized each time it is repeatedly reflected inside. For example, the reflectance of the inner surface that has been black anodized is about 40%. In this case, the amount of light of the laser light LB decreases by about 60 percent with one reflection. With two or more reflections, the amount of light of the laser light LB further decreases. With this simple configuration, the laser light LB that has passed through the dichroic mirror 212 in the -Z direction can be absorbed. Therefore, it is possible to prevent the laser light LB emitted by the laser oscillator 10, traveling in the -Z direction, and transmitted through the dichroic mirror 212 from entering the photoelectric element 33 of the measurement unit 30.

[0028] Moreover, the third straight portion 46 is formed to gradually become thinner toward the terminal end portion 47. Therefore, the frequency of reflection of the laser light LB increases toward the terminal end portion 47. This makes it possible to efficiently attenuate the laser light LB.

[0029] Ideally, it is desirable for the laser light LB to be absorbed until the amount of light of the laser light LB that has entered the attenuation structure 40 becomes zero, but there are cases where the amount of light of the laser light LB cannot be reduced to zero. In this case, it is assumed that a part of the laser light LB will exit the attenuation structure 40 again. For this reason, the shape and size of the internal space of the attenuation structure 40 are set so that the laser light LB can be absorbed until the amount of light of the laser light LB becomes equal to or less than a predetermined amount of light. The predetermined amount of light is, for example, an amount of light that does not affect the measurement of the reflected light RB even if the attenuated laser light LB exits the attenuation structure 40.

[0030] In this manner, the attenuation structure 40 absorbs the laser light LB that is transmitted through the dichroic mirror 212 out of the laser light LB incident on the laser scanner 20 from the laser oscillator 10 until the amount of light becomes equal to or less than a predetermined amount.

[0031] FIG. 3 is a schematic diagram showing the path of reflected light RB until it reaches the measurement unit 30 in a laser welding apparatus 100 equipped with an attenuation structure 40. The reflectance of the dichroic mirror 212 in the reflection wavelength range is 99.9%, and the transmittance of the reflection wavelength range is 0.1%. The reflectance at the workpiece WK is 60%. The reflectance of the attenuation structure 40 is 0%. In FIG. 3, the intensity of the laser light LB is illustrated to facilitate understanding of the technology. The intensity of the laser light LB is proportional to the amount of light of the laser light LB.

[0032] 3, it is assumed that the power of the laser light LB output by the laser oscillator 10 is 1000 W. 99.9% of the 1000 W laser light LB, i.e., 999 W of the laser light LB, is reflected by the dichroic mirror 212 and enters the workpiece WK. 0.1% of the 1000 W laser light LB, i.e., 1 W of the laser light LB, enters the attenuation structure 40 and is absorbed.

[0033] The 999W laser light LB is reflected by the workpiece WK and becomes reflected light RB. At this time, the power of the reflected light RB is approximately 599W. 0.1% of the 599W reflected light RB, i.e., 599mW reflected light RB, enters the measurement unit 30. In this way, since the attenuation structure 40 absorbs the 1W laser light LB, only the reflected light RB reflected by the workpiece WK that has passed through the dichroic mirror 212 enters the measurement unit 30. In other words, only the reflected light RB reflected by the workpiece WK enters the measurement unit 30. In this way, the part of the laser light LB that has passed through the dichroic mirror 212 is prevented from entering the photoelectric element 33 of the measurement unit 30. Therefore, the measurement unit 30 can measure only the intensity of the reflected light RB reflected by the processing target area.

[0034] As shown in Fig. 3, the direction in which the laser light LB emitted by the laser oscillator 10 enters the dichroic mirror 212 must be different from the direction in which the reflected light RB reflected by the workpiece WK enters the dichroic mirror 212. The positions of the laser oscillator 10, the dichroic mirror 212, the workpiece WK, and the measurement unit 30 must be set so that these directions are different. For example, it is desirable to set the direction in which the laser light LB emitted by the laser oscillator 10 enters the dichroic mirror 212 and the direction in which the reflected light RB reflected by the workpiece WK enters the dichroic mirror 212 so as to be perpendicular to each other. Here, perpendicular includes a range of 90 degrees plus or minus 10 degrees.

[0035] 4 is a schematic diagram showing the path of reflected light RB until it reaches the measuring unit 30 in a laser welding device not equipped with an attenuation structure 40. Below, for comparison, a case where the attenuation structure 40 is not equipped will be described. Explanations of conditions common to FIG. 3 will be omitted. The scanner structure is, for example, a part of the housing of the laser scanner 20. The reflectance of the scanner structure is 75%.

[0036] In FIG. 4, the power of the laser light LB output by the laser oscillator 10 is 1000 W. 99.9% of the 1000 W laser light LB, i.e., 999 W of the laser light LB, is reflected by the dichroic mirror 212 and enters the workpiece WK. 0.1% of the 1000 W laser light LB, i.e., 1 W of the laser light LB, enters the scanner structure. The 1 W laser light LB is reflected by the scanner structure and becomes reflected light RB2. At this time, the power of the reflected light RB2 is 750 mW. The 750 W reflected light RB2 is reflected by the dichroic mirror 212. As a result, the reflected light RB2 of approximately 743 mW enters the measurement unit 30.

[0037] Furthermore, the 999 W laser light LB incident on the workpiece WK is reflected by the workpiece WK and becomes reflected light RB. At this time, the power of the reflected light RB is approximately 599 W. 0.1% of the 599 W reflected light RB, i.e., 599 mW reflected light RB, is incident on the measurement unit 30. As a result, a total of 1342 mW of light is incident on the measurement unit 30.

[0038] 4, not only the reflected light RB reflected by the workpiece WK, but also the reflected light RB2, which is the light of the laser light LB output by the laser oscillator 10 that passes through the dichroic mirror 212 and is reflected by the scanner structure, enters the measurement unit 30. Therefore, the light that enters the measurement unit 30 includes light that is not reflected by the workpiece WK. Both the reflected light RB and the reflected light RB2 are reflections of the laser light LB, and therefore have the same wavelength. For this reason, the measurement unit 30 cannot measure the reflected light RB and the reflected light RB2 individually.

[0039] As shown in FIG. 1, the control unit 60 controls the laser oscillator 10 and the laser scanner 20. The functions of the control unit 60 are realized by a computer including a CPU (Central Processing Unit) and a memory. A program for executing a laser welding process is stored in the memory. This program is executed by the CPU. Thus, the laser oscillator 10 and the laser scanner 20 are controlled. Specifically, the control unit 60 designates an output value of the laser light LB to the laser oscillator 10, and causes the laser light LB to be output. The control unit 60 designates an irradiation position of the laser light LB on the irradiated surface of the workpiece WK in XY coordinates to the galvano scanner unit 230, and causes the condensing point of the laser light LB to be changed. In addition, the control unit 60 designates a focal position to the Z lens drive unit 220, and causes the Z lens 215 to be moved.

[0040] The control unit 60 also receives an electrical signal indicating the intensity of the reflected light RB from the measurement unit 30. For example, the control unit 60 monitors the time series change in the intensity of the reflected light RB based on the time series change in the output current of the photoelectric element 33. The control unit 60 evaluates the quality of the welding based on the time series change in the intensity of the reflected light RB. The control unit 60 is also called a quality evaluation unit.

[0041] The input device 61 is a keyboard, a mouse, etc. connected to the control unit 60. The input device 61 is used, for example, when a user inputs an output value of the laser light LB. The display device 62 is a liquid crystal display, an organic EL (Electro Luminescence) display, etc. connected to the control unit 60. The display device 62 is used, for example, to display the evaluation result.

[0042] 5 is a flowchart showing a method for evaluating the quality of welding performed by the laser welding apparatus 100. In step S101, the control unit 60 instructs the robot controller to move the robot arm to a welding start position. In response to the instruction from the control unit 60, the robot controller moves the robot arm to the welding start position. Thus, the laser scanner 20 attached to the tip of the robot arm is disposed at the welding start position. The robot controller notifies the control unit 60 that the movement of the robot arm to the welding start position is completed.

[0043] In step S102, in response to the notification from the robot controller, the control unit 60 starts welding. Specifically, the control unit 60 controls the laser oscillator 10 to start outputting the laser light LB. Furthermore, the control unit 60 instructs the robot controller to cause the robot arm to perform a movement task. The movement task performed by the robot arm refers to the movement of the laser scanner 20 by the robot arm moving along a path taught in advance. In response to the instruction to perform the movement task from the control unit 60, the robot controller starts moving the robot arm. As the robot arm moves, the laser light LB is irradiated from the laser scanner 20 to the workpiece WK.

[0044] The control unit 60 controls the laser oscillator 10, for example, as follows, from the start to the stop of the output of the laser light LB. The control unit 60 controls the laser oscillator 10 to gradually increase the laser output until the laser output reaches a predetermined output value. When the laser output reaches the predetermined output value, the control unit 60 controls the laser oscillator 10 to continue the state in which the laser output is kept constant. When a predetermined period has elapsed, the control unit 60 controls the laser oscillator 10 to gradually decrease the laser output. Thus, the laser output of the laser oscillator 10 finally becomes zero, that is, the laser output stops. The predetermined period is, for example, a period set so that the timing of stopping the laser output is the same as the timing of completing the operation of the robot arm. By controlling the laser output in this manner, the occurrence of welding defects such as spatters and cracks can be reduced.

[0045] In step S103, the control unit 60 starts measuring the reflected light RB. For example, the control unit 60 acquires an electrical signal indicating the intensity of the reflected light RB output by the photoelectric element 33 every second, and stores the intensity of the reflected light RB indicated by the acquired electrical signal in memory. That is, the step of accepting the measurement result of the intensity of the reflected light RB measured by the measurement unit 30 is executed by the control unit 60.

[0046] In step S104, the control unit 60 waits for a notification that the movement of the robot arm is complete. Until the movement of the robot arm is completed (step S104; NO), the irradiation of the laser light LB and the measurement of the intensity of the reflected light RB are continued. When the robot controller moves the robot arm to the final point of the previously taught path, it notifies the control unit 60 that the movement is complete. When the control unit 60 receives a notification from the robot controller that the movement of the robot arm is completed (step S104; YES), it executes the process of step S105.

[0047] In step S105, the control unit 60 causes the laser oscillator 10 to stop outputting the laser light LB in order to end the welding. The control unit 60 also stops acquiring a signal from the photoelectric element 33. After that, the control unit 60 instructs the robot controller to retract the robot arm. In response to the instruction from the control unit 60, the robot controller retracts the robot arm from the final point to the retract position.

[0048] In step S106, the control unit 60 evaluates the quality of the welding at the processing target portion based on the measured value of the intensity of the reflected light RB, and outputs an image showing the evaluation result to the display device 62. For example, the control unit 60 can evaluate the quality of the welding as follows. In general, the intensity of the reflected light RB reflected by the workpiece WK of the laser light LB increases rapidly immediately after the start of irradiation of the laser light LB, then decreases rapidly, and thereafter tends to take an almost constant value. If the intensity of the reflected light RB falls outside a predetermined range after a predetermined time has elapsed since the start of irradiation, the control unit 60 evaluates that a defect has occurred in the welding. Specifically, it is assumed that an upper limit value and a lower limit value that define the predetermined range are stored in advance in the memory. The control unit 60 can evaluate that a defect has occurred in the welding when the intensity of the reflected light RB exceeds the upper limit value or falls below the lower limit value. The control unit 60 can output an evaluation result that the welding result is defective.

[0049] Alternatively, the control unit 60 may evaluate that a defective weld has occurred when the number of times the intensity of the reflected light RB falls outside a predetermined range exceeds a threshold value after a predetermined time has elapsed since the start of irradiation. That is, the step of evaluating the quality of the laser processing at the processing target portion based on the measurement results and the evaluation step of showing the evaluation results indicative of the quality are executed by the control unit 60. In this way, the control unit 60 only needs to output a quality result based on the result of detecting only the reflected light RB reflected by the laser light LB emitted from the laser oscillator 10. Therefore, no complicated process is required for quality evaluation.

[0050] As described above, in the embodiment, the quality of the weld is evaluated based on the intensity of the reflected light RB, which is the laser light LB reflected by the workpiece WK. The advantages of evaluating the quality of the weld based on the intensity of the reflected light RB will be described below.

[0051] Conventionally, when measuring the intensity of thermal radiation light, it is necessary to make the field of view of the sensor that measures the thermal radiation light almost coincide with the laser focus diameter. The wavelength of the thermal radiation light is, for example, 800 nm. FIG. 6 is a diagram showing an example of the positional relationship between the sensor field of view V1 and the laser focus diameter F1. In FIG. 6, the size of the sensor field of view V1 is almost the same as the size of the laser focus diameter F1, which is the range where the laser light LB is focused. The molten pool MP formed by melting the metal is present around the laser focus diameter F1.

[0052] FIG. 7 is a diagram showing another example of the positional relationship between the sensor field of view V1 and the laser focusing diameter F1. In FIG. 7, a part of the laser focusing diameter F1 is out of the sensor field of view V1. In this case, the sensor cannot accurately measure the intensity of the thermal radiation light generated in a part of the range of the laser focusing diameter F1. The deviation between the sensor field of view V1 and the laser focusing diameter F1 may occur, for example, as follows. As described above, the welding work is performed while the laser scanner 20 is moved by the robot arm. For example, it is assumed that welding is performed on a large number of workpieces WK in succession. In such a case, the optical axis or the sensor field of view V1 may be deviated due to residual vibration of the robot arm. As a result, the sensor field of view V1 and the laser focusing diameter F1 are deviated. Assuming the occurrence of the deviation between the sensor field of view V1 and the laser focusing diameter F1, for example, it is considered to set the sensor field of view V1 to be somewhat larger than the size of the laser focusing diameter F1.

[0053] FIG. 8 is a diagram showing another example of the positional relationship between the sensor field of view V1 and the laser condensed diameter F1. FIG. 8 shows an example in which the sensor field of view V1 is set to be somewhat larger than the laser condensed diameter F1. In this case, it is considered that it is easier to suppress a situation in which the laser condensed diameter F1 and the sensor field of view V1 are misaligned due to a misalignment of the optical axis or the field of view of the sensor. However, in the case shown in FIG. 8, the sensor field of view V1 includes the laser condensed diameter F1 and a part of the molten pool MP. Therefore, in addition to the intensity of the thermal radiation light generated at the laser condensed diameter F1, the intensity of the thermal radiation light generated in a part of the molten pool MP is also measured. Therefore, the intensity of the thermal radiation light generated at the laser condensed diameter F1 cannot be accurately measured. In this way, when evaluating the quality of welding based on the intensity of the thermal radiation light, the above-mentioned problems may occur.

[0054] On the other hand, the reflected light RB is light reflected from the range irradiated with the laser light LB, and is not detected from outside the range of the laser focus diameter F1. For example, even if the sensor field of view V1 is set to be somewhat larger than the laser focus diameter F1 as shown in Fig. 8, or even if the size of the sensor field of view V1 and the size of the laser focus diameter F1 are aligned as shown in Fig. 6, there is no significant difference in the detection result of the reflected light RB. Therefore, even if the sensor field of view V1 is set to be somewhat larger than the laser focus diameter F1 in anticipation of the occurrence of a misalignment of the optical axis or the sensor field of view V1, the accuracy of the welding evaluation does not decrease compared to the case where the sensor field of view V1 and the laser focus diameter F1 are aligned.

[0055] In the configuration according to the embodiment, the laser light LB emitted from the laser oscillator 10 and transmitted through the dichroic mirror 212 is absorbed until the amount of light is equal to or less than a predetermined amount. The laser light LB emitted from the laser oscillator 10 and transmitted through the dichroic mirror 212 can be prevented from entering the measurement unit 30. In this manner, in the laser welding device 100, the quality of the laser processing at the processing target portion is evaluated based on the reflected light RB reflected at the processing target portion. Unlike the conventional evaluation of the quality of laser processing using thermal radiation, it is not essential to accurately match the field of view of the sensor with the focused diameter of the laser light LB, so that the evaluation accuracy can be easily maintained. In addition, the same effect is obtained in the method of evaluating the quality of laser processing using the laser welding device 100.

[0056] Furthermore, the intensity of the thermal radiation light corresponds to a physical quantity that represents the shape of the surface of the part to be processed by heat. The intensity of the reflected light RB corresponds to a physical quantity that represents the shape of the surface of the part to be processed by light reflection. From this, it can be said that the intensity of the reflected light RB can more directly represent the shape of the surface of the part to be processed compared to the intensity of the thermal radiation light. Therefore, evaluating the part to be processed based on the change in the intensity of the reflected light RB can more accurately represent the change in the shape of the surface of the part to be processed compared to evaluating the part to be processed based on the change in the intensity of the thermal radiation light.

[0057] In the embodiment, the quality of welding is evaluated using the reflected light RB having the same wavelength as the wavelength of the laser light LB, so as described above, there is a risk that a portion of the laser light LB transmitted through the dichroic mirror 212 may be incident on the photoelectric element 33 of the measurement unit 30. However, since the attenuation structure 40 absorbs a portion of the laser light LB transmitted through the dichroic mirror 212, the portion of the laser light LB transmitted through the dichroic mirror 212 is prevented from being incident on the photoelectric element 33 of the measurement unit 30. Therefore, the control unit 60 can evaluate the quality of welding at the processing target portion based on the reflected light RB reflected at the processing target portion.

[0058] B1. Alternative embodiment 1: In the embodiment, the example in which the inner surface of the damping structure 40 is black anodized has been described, but the present invention is not limited to this. For example, the inner surface of the damping structure 40 may be black plated.

[0059] In the embodiment, an example in which the laser oscillator 10 is a fiber laser has been described, but the laser oscillator 10 may be another type of laser such as a YAG laser.

[0060] In the embodiment, welding has been described as an example of laser processing, but the above-described evaluation method can also be adopted in other types of laser processing.

[0061] In the embodiment, since the attenuation structure 40 is disposed outside the housing of the laser scanner 20, the attenuation structure 40 is configured from a tubular member having two bent portions (see FIG. 2). Alternatively, the attenuation structure 40 may be configured from a tubular member having no bent portions. Also, the attenuation structure 40 may be configured from a tubular member having one bent portion. Also, the attenuation structure 40 may be configured from a tubular member having three or more bent portions. Also, the attenuation structure 40 may be disposed inside the housing of the laser scanner 20.

[0062] In the embodiment, an example has been described in which the third straight portion 46 (see FIG. 2) of the attenuation structure 40 is formed in a triangular pyramid shape. Alternatively, the shape of the third straight portion 46 may be a cone or a quadrangular pyramid. In this manner, it is desirable that the third straight portion 46 is formed in a tapered shape so as to gradually become thinner toward the terminal portion 47. In this case, as in the embodiment, the frequency of reflection of the laser light LB in the attenuation structure 40 increases toward the terminal portion 47. This allows the laser light LB to be efficiently attenuated.

[0063] Alternatively, the third straight portion 46 of the attenuation structure 40 may be formed in the shape of a cylinder or a square prism. In this case, the height of the cylinder or square prism is set to a height such that the amount of the entering laser light LB is equal to or less than a predetermined amount of light, and the same effect as that of the embodiment can be expected. Also, the end portion 47 of the attenuation structure 40 is closed.

[0064] The present disclosure is not limited to the above-mentioned embodiment, and can be realized in various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention column can be appropriately replaced or combined in order to solve some or all of the above-mentioned problems or to achieve some or all of the above-mentioned effects. Furthermore, if the technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0065] 10...laser oscillator, 11...optical fiber cable, 20...laser scanner, 30...measuring section, 31...bandpass filter, 32...third reflecting mirror, 33...photoelectric element, 40...attenuation structure, 41...opening, 42...first straight section, 43...first bent section, 44...second straight section, 45...second bent section, 46...third straight section, 47...termination section, 60...control section, 61...input device, 62...output device, 100...laser welding device, 205...optical isolator, 210...optical system, 211...collimator Lens, 212... dichroic mirror, 212a, 212b... surfaces, 213... first reflecting mirror, 214... diffraction optical element, 215... Z lens, 216... second reflecting mirror, 217... focusing lens, 220... Z lens drive unit, 230... galvano scanner unit, 240... protective glass, F1... laser focusing diameter, LB... laser light, MP... molten pool, RB... reflected light, RB2... reflected light, V1... sensor field of view, WK... workpiece, Wa... first metal object, Wb... second metal object

Claims

1. A laser processing device having a function for evaluating the quality of laser processing using only the intensity of reflected laser light, an oscillator that emits laser light; A mirror disposed in an optical path of the laser light, A first laser beam, which is a part of the laser beam emitted from the oscillator and has a reflection wavelength range that is a wavelength range in a predetermined range centered on a central wavelength of the laser beam, is transmitted, while a second laser beam, which is another part of the laser beam and has the reflection wavelength range, is reflected, and the second laser beam is irradiated onto a processing target portion; a mirror that transmits a first reflected light that is a part of a reflected light that is the second laser light irradiated to the processing target portion and reflected by the processing target portion; a sensor unit that measures an intensity of the first reflected light that is reflected by the processing target portion and transmitted through the mirror; an absorbing section that absorbs the first laser light that has passed through the mirror and entered the processing target portion without being reflected therefrom until the amount of light becomes equal to or less than a predetermined amount, thereby preventing the first laser light from being incident on the sensor section; a quality evaluation unit that outputs an evaluation result representing a quality of laser processing of the processing target portion based on a measurement result of the intensity of the first reflected light measured by the sensor unit; Equipped with Laser processing equipment.

2. 2. The laser processing apparatus according to claim 1, the absorbing unit is a cylindrical member into which the first laser light is incident, the cylindrical member having an inner surface that is black anodized and one end of which is closed; the tubular member includes a first straight portion, a first bent portion, a second straight portion, a second bent portion, and a third straight portion; the first linear portion extends along the optical path of the laser light emitted from the oscillator, The second straight portion extends in a direction intersecting a direction in which the first straight portion extends, the first bent portion connects the first straight portion and the second straight portion, the second bent portion connects the second straight portion and the third straight portion, The third straight portion extends in a direction intersecting a direction in which the second straight portion extends, and is formed in a tapered shape so as to become gradually thinner toward an end, and the end of the third straight portion is closed. Laser processing equipment.

3. A method for evaluating the quality of laser processing by a laser processing apparatus using only the intensity of reflected laser light, comprising: The laser processing apparatus includes: an oscillator that emits laser light; A mirror disposed in an optical path of the laser light, A first laser beam, which is a part of the laser beam emitted from the oscillator and has a reflection wavelength range that is a wavelength range in a predetermined range centered on a central wavelength of the laser beam, is transmitted, while a second laser beam, which is another part of the laser beam and has the reflection wavelength range, is reflected, and the second laser beam is irradiated onto a processing target portion; a mirror that transmits a first reflected light that is a part of a reflected light that is the second laser light irradiated to the processing target portion and reflected by the processing target portion; a sensor unit that measures an intensity of the first reflected light that is reflected by the processing target portion and transmitted through the mirror; an absorbing section that absorbs the first laser light that has passed through the mirror and entered the processing target portion without being reflected therefrom until the amount of light is equal to or less than a predetermined amount, thereby preventing the first laser light from being incident on the sensor section; Equipped with The evaluation method is as follows: receiving a measurement result of the intensity of the first reflected light measured by the sensor unit; Evaluating quality of the laser processing of the processing target portion based on the measurement results; outputting an evaluation result representative of the quality; Execute the Evaluation method.

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