JP4349075B2 - Laser processing method and processing state judgment method - Google Patents

Description

  The present invention relates to a laser processing method for irradiating a metal material with a laser, a processing state determination method for laser processing, a laser processing state determination device, and a laser processing device.

Conventionally, laser processing for welding or cutting by irradiating a metal material with laser is non-contact processing, so visual inspection after processing is necessary to determine the quality of the state after processing. It was. On the other hand, in laser processing, an apparatus for irradiating measurement light after processing to determine the quality of processing from reflected light is disclosed in Japanese Patent Laid-Open No. 4-182085 (Patent Document 1). Also, Japanese Patent Laid-Open No. 4-33786 (Patent Document 2) discloses a processing method for determining the quality of processing by irradiating laser light of weak power after laser processing and measuring the power of reflected light. ing. Further, a laser processing apparatus that performs in-line inspection using these methods is disclosed in Japanese Patent Laid-Open No. 2001-121279 (Patent Document 3).
JP-A-4-18285 JP-A-4-33786 Japanese Patent Laid-Open No. 2001-121279

  However, in the inspection methods of Patent Documents 1 to 3, the irradiation light of the laser light irradiated after processing changes due to the variation in the melting state of the processed portion of the metal material by laser light irradiation and the slight difference in the angle and position, There was a risk of misjudging the processing state. In particular, when two metal plates are joined by being overlapped and welded, it is not easy to determine whether they are reliably joined by visual observation from above or by the methods described in Patent Documents 1 to 3. .

  The present invention has been made in view of such a reason, and the object of the present invention is to irradiate laser light after processing due to variations in the melted state of the metal material processing portion and slight differences in angle and position due to laser light irradiation. It is an object of the present invention to provide a processing state determination method for laser processing that is less likely to erroneously determine a processing state due to changes in light irradiation light.

In order to solve the above-described problems, a processing state determination method of laser processing according to the present invention includes a secondary laser beam having an energy density lower than that of the primary laser beam after irradiating the primary laser beam for processing. In the laser processing state determination method for determining the processing state by measuring the reflected light of the secondary laser light, the amplitude of the reflected light intensity of the secondary laser light is 1 of the predetermined time measured the amplitude of the reflected light intensity of the second-order laser beam second predetermined time measurement, the amplitude of the reflected light intensity measured at a first predetermined time and second predetermined time after this Are compared with the threshold values at the first predetermined time and the second predetermined time set in advance, respectively, to evaluate the melted and solidified state of the processed portion and determine the processed state.

According to the laser beam machining state determination method of the present invention, the amplitude of the reflected light intensity of the secondary laser light is measured for a first predetermined time, and then the amplitude of the reflected light intensity of the secondary laser light is set to the second. And the amplitude of the reflected light intensity measured at the first predetermined time and the second predetermined time is respectively compared with a threshold value at the first predetermined time and the second predetermined time set in advance. Since the melted and solidified state of the processed part is evaluated by the above, the melted state can be evaluated by the first predetermined time measurement, and the solidified state can be evaluated by the second predetermined time measurement. For this reason, the laser beam irradiated after processing changes due to variations in the melting state of the processed portion of the metal material due to laser light irradiation and slight differences in angle and position, thereby reducing the possibility of misjudging the processing state.

(Embodiment 1)
The processing state judgment method of the laser processing of this embodiment is demonstrated based on FIGS. As shown in FIG. 1, the laser beam machining state determination method of the present embodiment is lower than the energy density of the machining laser beam (primary laser beam) after the machining laser beam irradiation, and the laser beam irradiation unit By irradiating the processing unit with a secondary laser beam having a predetermined energy density at a level that is not processed, and measuring the reflected light intensity of the secondary laser beam, the melted and solidified state (the presence or absence of melting and the molten shape) of the processing unit is determined. Detect and determine the machining state. As shown in FIG. 1 (a), the secondary laser light may be continuous with the primary laser light, and as shown in FIG. 1 (b), a predetermined time elapses after the irradiation with the primary laser light. It may be irradiated later.

  As the metal material to be processed, welding is performed by irradiating the first laser beam to two plate materials (first metal plate 1 and second metal plate 2) of metal materials such as iron, copper, aluminum and alloys thereof. Perform processing. Specifically, the welding structure is applied to various joint weldings such as lap joint welding shown in FIG. 2, butt joint welding shown in FIG. 3, fillet joint welding shown in FIG. In any welding, the first metal plate 1 and the second metal plate 2 are irradiated with the primary laser beam to melt both the metal plates. In this case, the first metal plate 1 and the second metal plate 2 are joined by forming the melting part 3. Further, when the secondary laser beam 4 is irradiated, the reflected light 5 is irradiated from the irradiation unit. Here, in FIGS. 2 to 4, (a) shows a state where the melted portion 3 is well formed and the first metal plate 1 and the second metal plate 2 are joined, and (b) The formation state of the fusion | melting part 3 is unsatisfactory, and the state which the 1st metal plate 1 and the 2nd metal plate 2 are not joined is shown.

  In lap joint welding in which a primary laser beam is irradiated on a superposition of two metal materials, a metal plate having a large laser absorption rate is disposed on the metal plate 1 on the laser beam irradiation side, and laser A metal material having a low laser absorptance is disposed on the metal plate 2 on the non-irradiation side.

  FIG. 5 shows a schematic diagram of the waveform of the reflected light measured. By comparing the amplitude W1 of the reflected light intensity of the secondary laser light in the determination section 1 (section t1 from the end of the primary laser light to the first predetermined time) with a preset threshold value, Can be determined. Further, the second defect is obtained by comparing the amplitude W2 of the reflected light intensity of the secondary laser light in the determination section 2 (section t2 from the first predetermined time to the second predetermined time) with a preset threshold value. It is possible to determine (melting failure of only the metal plate 1).

  Here, a flowchart for determining the machining state is shown in FIG. That is, the threshold amplitude Wth1 in the determination section 1 and the threshold amplitude Wth2 in the determination section 2 are set in advance. Then, when the measured reflected light amplitude W1 in the determination section 1 is larger than Wth1, and the amplitude W2 in the determination section 2 is smaller than Wth2, it is determined to be a non-defective product. FIGS. 7 to 9 show sectional views of lap joint welding and schematic diagrams of reflected light measurement waveforms corresponding thereto. First, as shown in FIG. 7A, in the case where the melted portion 3 is satisfactorily formed in the metal plate 1 and the metal plate 2, a schematic diagram of the waveform of the reflected light is shown in FIG. First, in the determination section 1, immediately after the irradiation with the first laser beam, the irradiated portion melts and swings, and therefore vibrates with a large amplitude W1. Therefore, the amplitude W1 becomes larger than Wth1. Next, in the determination section 2, since the solidification progresses with time and the vibration is attenuated, the vibration vibrates with a small amplitude W2. Therefore, the amplitude W2 becomes smaller than Wth2.

  Further, when the melted portion 3 is formed only on the metal plate 1 as shown in FIG. 8 (a), in the determination section 1, as shown in FIG. Similarly, the reflected light of the secondary laser beam oscillated with a large amplitude W1 is measured. For this reason, the amplitude W1 becomes larger than Wth1 like the non-defective product. However, since heat conduction from the metal plate 1 to the metal plate 2 does not occur, the molten state of the laser light irradiation part of the metal plate 1 continues and vibration does not attenuate over time. The reflected light of the secondary laser beam oscillated with a large amplitude W2 is measured. Therefore, the amplitude W2 becomes larger than Wth2.

  Furthermore, as shown in FIG. 9A, in the case of a defective hole, a hole is formed in the laser beam irradiation part, and the melting part 3 is hardly present. For this reason, as shown in FIG. 9B, the reflected light of the secondary laser light with small vibration is measured immediately after the irradiation with the primary laser light. For this reason, the amplitude W1 becomes smaller than Wth1.

  Here, the first predetermined time is at least 5 milliseconds after the end of the primary laser beam, and the second predetermined time is 10 milliseconds or less. By doing so, it is possible to evaluate the state before the solidified portion of the melted portion of the laser light irradiation portion immediately after the end of the primary laser light, and to determine the processing state based on the reflected light intensity of the secondary laser light. It becomes easy.

  Moreover, the structure of the laser processing apparatus used for the processing state judgment method of the laser processing of this embodiment is shown in FIG. This includes a laser beam emitting unit that irradiates the metal plate 1 with the laser beam 4, and an optical measurement unit that measures the reflected light 5 and the plasma beam 6. The laser beam emitting unit includes a laser oscillation unit 10a that oscillates the primary laser beam, a laser oscillation unit 10b that oscillates the secondary laser beam, optical fibers 17 and 17 that guide these YAG laser beams, Mirrors 16 and 16 that reflect in the direction and a lens 15 that collects light are provided. In addition, the optical measuring unit is provided with a PD sensor 13 that detects the reflected light 5 by arranging a band pass filter 11 that transmits only YAG laser light on the front surface, and a cut filter 12 that shields the YAG laser light on the front surface. And a PD sensor 14 for detecting the plasma light 6. Here, examples of the element of the PD sensor 13 that detects the reflected light 5 include a Si photodiode and an InGaAs photodiode. On the other hand, the PD sensor 14 for detecting the plasma light 6 includes a microchannel plate and a photo multiplayer when the plasma light is ultraviolet light to visible light, and a Si photodiode when the plasma light is 190 nm to 1100 nm. In the case of 700 nm to 2600 nm, there is an InGaAs photodiode, and in the infrared region, a PbSe photoconductive element, an InAs photovoltaic element, an InSb photovoltaic element, an MCT photoconductive element, and the like can be given.

  As described above, in the laser beam machining state determination method of the present embodiment, the reflected light of the secondary laser light is measured for the first predetermined time, and then the reflected light of the secondary laser light is measured for the second predetermined time. The machining state is determined by measuring. In other words, this welding state determination method utilizes the fact that the process from melting to solidification of molten metal immediately after laser light irradiation is closely related to the processing state, and more immediately after irradiation of the processing laser light. This is done by irradiating the processing portion with an energy density inspection laser that is not processed by the irradiation portion, and detecting the molten and solidified state of the molten metal material based on the state of the reflected light. For this reason, there is no disturbance such as a difference in the melting phenomenon (keyhole formation state) and a variation in the processing state of the peripheral portion of the welded portion (thermal influence state of the peripheral resin portion) due to laser scattered light, and the processing state can be reliably determined.

  In addition, when the two metal materials are welded by irradiating the first laser beam on a superposition of two metal plates, the welding state of defects that are difficult to detect by other methods Can be determined, and the effect is particularly effective.

  In addition, by arranging two metal plates, a metal plate having a large laser absorption rate on the laser light irradiation side, and a metal plate having a low laser absorption rate on the laser non-irradiation side, the metal on the laser non-irradiation side The material is less likely to melt, and the effect is particularly effective.

  In addition, in the determination of the state of lap welding that is difficult to detect defects by irradiating a laser in a molten state by setting the first predetermined time to 5 milliseconds or less and the second predetermined time to 10 milliseconds or less, Judgment accuracy is improved.

  In addition, although the processing state judgment method of the laser processing of this embodiment has described about welding processing, it is not restricted to this, It can apply also to processing, such as drilling and a cutting | disconnection.

(Embodiment 2)
FIG. 11 shows the structure of a laser processing apparatus used in the laser processing state determination method of the second embodiment. The processing state determination method of this embodiment is substantially the same as that of Embodiment 1, but the structure of the optical measurement unit is different. The laser processing apparatus of this embodiment has a structure capable of oscillating the primary laser beam and the secondary laser beam from the laser oscillation unit 10 that is the same light source by using a waveform control function in the laser beam emitting unit. It has become.

  The method for determining the processing state of laser processing using the laser beam emitting portion of the present embodiment can irradiate the primary laser beam and the secondary laser beam from the same light source, thus simplifying the laser processing apparatus and reducing the equipment cost. Down and space saving.

(Embodiment 3)
FIG. 12 shows the structure of a laser processing apparatus used in the laser processing state determination method of the third embodiment. The processing state determination method of this embodiment is substantially the same as that of Embodiment 1, but the structure of the optical measurement unit is different. The laser processing apparatus of this embodiment measures the reflected light 5 by the same optical system as the optical system that irradiates the primary laser light. As a mirror of the laser processing apparatus, by using a partial reflection mirror 18 that transmits the plasma light 6 and reflects a part of the laser light, the plasma light 6 and the reflected light 5 emitted from the processing part are partially The reflection mirror 18 is transmitted. Then, after changing the direction of these lights by the mirror 16 and passing through the plano-convex lens 19, the plasma light 6 and the reflected light 5 are separated by the dichroic mirror 20 and measured by the PD sensors 13 and 14. In addition, a cut filter 12 that shields the YAG laser light is provided on the front surface of the PD sensor 14 that detects the plasma light 6, and a band-pass filter 11 that transmits only the YAG laser light is provided on the front surface of the PD sensor 13 that detects the reflected light 5. It is arranged. It is also possible to make a determination by image recognition of the welded part by arranging an image measuring device such as a camera in the part where the plasma light 6 is detected. All of these can be measured coaxially with the laser beam, and can also be used in a processing machine using a galvanometer mirror.

  Since the laser beam machining state determination method of the present embodiment can measure the reflected light by the same optical system as that irradiated with the primary laser beam, the laser machining apparatus is further simplified, Cost reduction and space saving can be further achieved.

(Embodiment 4)
The laser beam machining state determination method of this embodiment will be described with reference to FIGS. The processing state determination method of the present embodiment is substantially the same as that of the first embodiment, but is characterized in that the processing state is determined by measuring the intensity of plasma light emitted from the processing unit. As shown in FIG. 13, the plasma light is composed of plasma light of the primary laser light and plasma light of the secondary laser light.

  Since the plasma light intensity emitted from the processed part is proportional to the molten pool area, that is, the penetration depth, the peak value P of the plasma light intensity is detected and compared with a preset threshold value Pth. Judgment is possible. That is, since the penetration amount (depth) is proportional to the welding strength, it is possible to newly determine a welding strength defect. Specifically, as shown in FIG. 14 (a), if the peak value P is larger than the threshold value Pth, it is determined that the welding state is good, and as shown in FIG. 14 (b), the peak value P is set to the threshold value Pth. If it is smaller than that, the welding state is determined to be defective.

  In welding, it is possible to determine the defects (drilled, partially welded, unwelded) during laser welding by measuring the reflected light intensity of the secondary laser beam, but the penetration depth (depth) Is difficult to determine. On the other hand, if the plasma light emitted from the processing part is measured, the penetration amount (depth) can be determined.

  Since the processing state determination method of the laser processing of this embodiment is characterized in that the processing state is determined by measuring the intensity of the plasma light of the primary laser light when irradiating the primary laser light. It is possible to improve the welding state determination accuracy and increase the number of detectable defects.

(Embodiment 5)
The laser processing method according to the fifth embodiment is a laser processing method in which repair processing is performed while feeding back the result of the laser processing status determination method according to any one of the first to fourth embodiments according to the flowchart shown in FIG.

  For example, in welding processing, after irradiating with a primary laser beam and irradiating with a secondary laser beam, the quality of the processing state is determined by the method according to any one of the first to fourth embodiments. . Then, if the processing state is good, the processing is completed, and if the processing state is poor, the laser light emitting part is moved to the vicinity of the first laser light irradiation part, and the laser light is irradiated again to perform repair processing. .

  The laser processing method of the present embodiment is characterized in that repair processing is performed while feeding back the result of the laser processing state determination method, so that it is possible to construct a production line in which defective products are unlikely to occur, and productivity is improved. improves.

(Embodiment 6)
The laser processing apparatus of Embodiment 6 is demonstrated based on FIG. The laser processing apparatus of the present embodiment is substantially the same as the laser processing apparatus of the third embodiment, but a processing state determination processing unit 25 is added.
That is, the laser processing apparatus of this embodiment includes a laser oscillation unit 10 that oscillates laser light, a laser light emission unit 21 that irradiates laser light, and plasma light and reflected light emitted from the processing unit during laser light irradiation. An optical measuring unit 22 that measures the intensity, and a processing state determination processing unit 25 that determines a processing state based on predetermined determination criteria from the intensities of the plasma light 6 and the reflected light 5 measured by the optical measuring unit 22. .

  The laser processing apparatus of this embodiment includes a laser oscillation unit that oscillates laser light, a laser light irradiation unit that irradiates the processing unit with laser light, and plasma light that is emitted from the processing unit when the processing unit is irradiated with laser light. And an optical measurement unit that measures reflected light and a determination unit that determines a processing state from the light intensity measured by the optical measurement unit, so that productivity is improved by inspection automation and reduction of inspection time. .

(Embodiment 7)
The laser processing apparatus of Embodiment 7 is demonstrated based on FIG. The laser processing apparatus of the present embodiment is substantially the same as the laser processing apparatus of the sixth embodiment, but a laser light irradiation control unit 26 is added. That is, the laser processing apparatus of this embodiment includes a laser oscillation unit 10 that oscillates laser light, a laser light emission unit 21 that irradiates laser light, and plasma light and reflected light emitted from a metal material during laser light irradiation. An optical measurement unit 22 that measures the intensity, a machining state determination processing unit 25 that determines a machining state from the intensities of the plasma light 6 and the reflected light 5 measured by the optical measurement unit 22 according to a predetermined criterion, and a machining state determination process A determination result in the unit 25 is fed back to the laser beam emitting unit 21 and the laser oscillation unit 10, and if there is a defect, a laser beam irradiation control unit 26 that irradiates the laser beam again in the vicinity of the first laser beam irradiation part ing. Then, the machining state is determined by the method described in the first to fifth embodiments, and repair processing is performed based on the determination result.

  The laser processing apparatus of this embodiment is characterized in that repair processing is performed while feeding back the result of the laser processing state determination method using the processing state determination device, so that it is possible to construct a production line that is unlikely to generate defective products. Productivity.

It is a figure which shows laser beam irradiation of Embodiment 1. FIG. It is sectional drawing which shows the lap joint welding of Embodiment 1, (a) has shown the quality goods and (b) has shown inferior goods. It is sectional drawing which shows the butt joint welding of Embodiment 1, (a) has shown the good quality item and (b) has shown inferior goods. It is sectional drawing which shows the meat joint welding of Embodiment 1, (a) has shown the non-defective product, (b) has shown the defective product. 3 is a schematic diagram illustrating reflected light according to Embodiment 1. FIG. 4 is a flowchart for determining a machining state according to the first embodiment. It is a top view which shows the state judgment of the lap joint welding of Embodiment 1, (a) is sectional drawing of a welding state (good product), (b) is a schematic diagram which shows the reflected light at this time. It is a top view which shows the state judgment of the lap joint welding of Embodiment 1, (a) is sectional drawing of a welding state (only one part melt | dissolves), (b) is a schematic diagram which shows the reflected light at this time. It is a top view which shows the state judgment of the lap joint welding of Embodiment 1, (a) is sectional drawing of a welding state (perforated), (b) is a schematic diagram which shows the reflected light at this time. It is sectional drawing which shows the laser processing apparatus of Embodiment 1. It is sectional drawing which shows the laser processing apparatus of Embodiment 2. It is sectional drawing which shows the laser processing apparatus of Embodiment 3. It is a schematic diagram which shows the plasma light of Embodiment 4. It is a schematic diagram which shows the plasma light of Embodiment 4, (a) has shown the non-defective product plasma light, (b) has shown the defective product plasma light. 10 is a flowchart for determining a laser processing method according to a fifth embodiment. It is sectional drawing which shows the laser processing apparatus of Embodiment 6. It is sectional drawing which shows the laser processing apparatus of Embodiment 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st metal plate 2 2nd metal plate 3 Melting | fusion part 4 Laser beam 5 Reflected light 6 Plasma light 10 Laser oscillation part 10a Primary laser beam laser oscillation part 10b Secondary laser beam laser oscillation part 11 Filter band pass 12 IR Cut filter 13 PD sensor for reflected light 14 PD sensor for plasma light 15 Laser condensing lens 16 Reflecting mirror 17 Optical fiber 18 Partial reflecting mirror 19 Plano-convex lens 20 Dichroic mirror 21 Laser light emitting unit 22 Optical measuring unit 25 Processing state determination processing unit 26 Laser beam irradiation control unit

Claims (9)

A method for determining a processing state of laser processing of a metal material, wherein a processing unit is irradiated with a secondary laser beam having an energy density lower than that of the primary laser beam after irradiating the primary laser beam for processing. In the processing state determination method of laser processing for determining the processing state by measuring the reflected light of the secondary laser light,
The amplitude of the reflected light intensity of the secondary laser light is measured for a first predetermined time, and thereafter, the amplitude of the reflected light intensity of the secondary laser light is measured for a second predetermined time, and the first predetermined time is measured. And evaluating the melted and solidified state of the processed part by comparing the amplitude of the reflected light intensity measured at the second predetermined time with the threshold values at the first predetermined time and the second predetermined time set in advance, respectively , A processing state determination method for laser processing, characterized by determining a processing state.   The laser processing state determination method according to claim 1, wherein the first laser beam and the second laser beam are irradiated from the same light source. 2. The laser machining processing state determination method according to claim 1, wherein the amplitude of the reflected light intensity of the secondary laser light is measured by the same optical system as the optical system that irradiates the primary laser light. .   The processing state is determined by measuring the intensity of plasma light of the primary laser light when irradiating the primary laser light. Laser machining processing status judgment method.   5. The two metal materials are welded to each other by irradiating the first laser beam on a superposition of two metal materials. 6. Laser machining processing status judgment method.   The metal materials having a large laser absorption rate are arranged on the laser beam irradiation side and the metal materials having a low laser absorption rate are arranged on the laser non-irradiation side. Item 6. The processing state determination method for laser processing according to any one of Items 5 to 6.   A laser processing method, wherein repair processing is performed while feeding back a result of the processing state determination method of laser processing according to any one of claims 1 to 6. A laser oscillation unit that oscillates laser light, a laser light irradiation unit that irradiates the processing unit with the laser light, and plasma light and reflected light intensity emitted from the processing unit when the processing unit is irradiated with the laser light . The laser processing according to any one of claims 1 to 6, further comprising: an optical measurement unit that measures amplitude; and a determination unit that determines a processing state from light intensity measured by the optical measurement unit. A laser processing state determination apparatus characterized by determining a processing state by the processing state determination method.   9. A laser processing apparatus for performing repair processing while feeding back a result of a processing state determination method of laser processing by the processing state determination device according to claim 8.

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