KR20200097994A - Monitoring system for inspection of Laser welding portion - Google Patents

Abstract

The present invention relates to a monitoring system for inspection of a laser welding portion, which is configured to inspect a workpiece (1) by performing optical coherence tomography (OCT) based on a surface of the workpiece (1) during laser welding or before and after welding. The monitoring system for inspection of a laser welding portion comprises: OCT (200) which separates light by the same light source (210) to obtain inspection light and reference light, is coupled to a focusing optical system (310) so that the inspection light is reflected and incident on the workpiece through the focusing optical system (310) of a welding apparatus, causes the reference light to proceed the same light path distance as the light path distance of the inspection light before welding and then, to be synthesized with the inspection light, and analyzes interference light generated by the synthesis using a spectrometer (250) so as to obtain a light path distance difference between the inspection light and the reference light; and a controller (400) which receives and monitors an optical path distance difference from the OCT (200). According to the present invention, it is possible to precisely measure the depth of a key hole.

Description

Monitoring system for inspection of laser welding portion

The present invention relates to a monitoring system for inspecting a laser weld that enables inspection of a workpiece during laser welding or before and after welding by optical coherence tomography (OCT).

Laser welding is a technique of forming a so-called welding line by irradiating a laser beam to the surface of a workpiece along an intended line, and is generally used to attach two or more workpieces, but is also used to thermally deform the workpiece surface. These welding lines are formed by welding beads that are continuously generated in the area where the laser beam passes.

However, the quality of laser welding is largely influenced by the penetration depth, and the surface shape of the formed welding bead and whether the welding line is formed as intended is also treated as an important quality item. Therefore, the welding bead is formed rather than quality inspection after welding. It is advisable to monitor the process in real time and check the quality in real time.

As a technology for real-time inspection of the penetration depth, a technique for measuring the depth of a key hole formed when a laser beam is irradiated with optical coherence tomography (OCT) has been disclosed.

However, before welding, the depth of the key hole must be measured using the surface of the workpiece as a reference surface, and in order to accurately measure the depth of the key hole by OCT, the reference surface must be accurately set. To this end, Korean Patent Application Publication No. 10-2016-0060112 determines a reference plane by measuring the distance to the surface of the workpiece before welding.

However, a method of measuring the distance to the reference plane, measuring the distance to the bottom of the key hole, and calculating the key hole depth based on the difference may be cumbersome, complicated, and low in accuracy. That is, the OCT optically obtains the distance difference from the reference set inside, and accuracy may be lower than when the internal reference is matched to the surface of the workpiece before welding.

On the other hand, since it is desirable to monitor the situation before and after welding in real time, it is desirable to be able to inspect the situation before and after welding by OCT.

KR 10-2016-0060112 A 2016.05.27.

Accordingly, an object of the present invention is to provide a monitoring system for inspecting a laser weld, which sets the OCT to measure the depth based on the surface of the workpiece before welding, and allows the state before and after welding to also be inspected by OCT.

The present invention to achieve the above object is a laser oscillator 100; And a focus adjustment optical system 310 for radiating and welding the laser beam of the laser oscillator 100 to focus on the workpiece 1. In the monitoring system for inspecting the laser weld in the welding apparatus including, the inspection light and the reference light are obtained by separating the light by the same light source 210, and the inspection light is reflected on the workpiece 1 through the focus adjustment optical system 310 It is coupled to the focusing optical system 310 to be incident, and the reference light is combined with the incident inspection light after proceeding with the same optical path distance as the optical path distance of the inspection light before welding. 250) to obtain the optical path distance difference between the inspection light and the reference light (OCT (Optical Coherence Tomography, 200)); And a controller 400 that receives and monitors the optical path distance difference from the OCT 200. Includes.

According to an embodiment of the present invention, the OCT 200 is coupled to the focusing optical system 310 so that the inspection light and the laser beam have the same optical axis, so that the depth of the key hole 2 generated during welding is reduced. The optical path distance difference is obtained, and the controller 400 divides the depth of the key hole 2 acquired in real time during welding by a predetermined period and records the maximum value for each section as the depth of the key hole 2 of the section.

According to an embodiment of the present invention, the OCT 200 uses the light transmitted through the beam splitter 220 among the light of the light source 210 as the inspection light and the light reflected by the beam splitter 220 as the reference light, The reference light is reflected to the reference arm 230, passed through the beam splitter 220, and incident on the spectrometer 250, but welded with the optical path distance D2 to the reference arm 230 based on the beam splitter 220 In order to equally adjust the optical path distance D1 to the surface of the entire workpiece 1, the reference arm 230 can be moved to the linear driving device 240, and the reference light reflected and incident on the workpiece 1 Is reflected by the beam splitter 220 to be incident on the spectrometer 250.

According to an embodiment of the present invention, the controller 400 is configured such that the difference in the optical path distance between the inspection light reflected by the workpiece 1 before welding and the reference light reflected on the reference arm 230 becomes '0'. Controls the driving device 240.

According to an embodiment of the present invention, an inspection optical system 320 capable of shifting the optical axis of the laser beam by varying the optical axis of the inspection light is provided between the OCT 200 and the optical system 310 for focusing, and the controller 400 controls the inspection optical system 320 to scan the front and rear of the area being welded by the laser beam on the welding line in the width direction of the welding line, so that the difference in the optical path distance in the width direction of the surface before and after welding can be obtained. do.

According to an embodiment of the present invention, the controller 400 makes it possible to correct a position to be welded with a laser beam according to a difference in the optical path distance obtained by scanning the front of the portion being welded.

In the present invention configured as described above, since the OCT is set to obtain the depth from the surface of the workpiece (1) before welding, the configuration can be simplified, the inspection process is simple, and the slight difference in depth from the reference surface is also precise. It can be measured accurately, and through this, the depth of the key hole (2) can be precisely measured.

According to an embodiment of the present invention, since the depth of the key hole 2 is determined for each section divided by a predetermined period, noise can be excluded and accurately measured.

According to an embodiment of the present invention, the light source 210, the inspection light in/out direction, the reference arm 230 and the spectrometer 250 are arranged crisscross with respect to the beam splitter 220, and the reference arm 230 is linearly moved. By means of a structure that is configured to be simplified, the surface of the workpiece 1 before welding can be accurately set as a reference plane.

According to an embodiment of the present invention, since it is possible to measure before and after the area being welded using the inspection optical system 320, it is possible to perform real-time inspection before and after the welding area during welding, and through this, data for improving welding quality even during welding. Can be utilized.

1 is a block diagram of a monitoring system for inspecting a laser welding part according to a first embodiment of the present invention.
2 is a graph showing the measured key hole depth (a) and a cross-sectional photograph of the welded workpiece (b).
3 is a graph showing the measured key hole depth and penetration depth of the welded workpiece (a) and a photograph of the longitudinal section of the welded workpiece (b).
4 is a configuration diagram of a monitoring system for inspecting a laser welding part according to a second embodiment of the present invention.
5 is a view showing a light path when inspecting an exemplary front of a welding area.
6 is a longitudinal cross-sectional view (a) and a top view (b) of the workpiece 1 showing the scanning direction when scanning the front and rear of the portion being welded with respect to the workpiece 1 being welded.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement them. In describing an embodiment of the present invention, when it is determined that a detailed description of a related known function or a known configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

Referring to the configuration diagram shown in FIG. 1, a monitoring system for inspecting a laser weld according to a first embodiment of the present invention includes an OCT (Optical Coherence Tomography, 200) and a controller 400, and a laser oscillator 100 And it is installed and coupled to the welding device including the optical system 310 for adjusting the focus.

The laser oscillator 100 outputs a laser beam for welding the workpiece 1.

The focusing optical system 310 is a configuration for condensing and emitting a laser beam to focus on the surface of the workpiece 1, and a collimating lens 311 converting a laser beam output from the laser oscillator 100 into parallel light , A dichroic mirror 312 that selectively reflects the parallel light of the laser beam to be deflected by 90° toward the workpiece 1, and the parallel light of the laser beam toward the workpiece 1 is condensed to the workpiece 1 ) It includes a focusing lens 313 to be focused on the surface.

Accordingly, the laser beam output from the laser oscillator 100 is radiated by focusing on the surface of the workpiece 1 through the focusing optical system 310 to weld the workpiece 1, and the laser oscillator 100 And since the focus adjustment optical system 310 is a component that is also provided in a general welding apparatus, further detailed description will be omitted.

However, according to the present invention, the inspection light of the OCT 200 is coupled to the focus adjustment optical system 310 so as to transmit the focus adjustment optical system 310.

To this end, the inspection light output from the OCT 200 is transmitted through the dichroic mirror 312 to be irradiated to the workpiece 1 through the focus adjustment lens 313, and the inspection light reflected on the workpiece 1 The focus adjustment optical system 310 and the OCT 200 were combined so as to be incident on the OCT 200 through the focus adjustment lens 313 and the dichroic mirror 312.

Hereinafter, the OCT 200 and the controller 400, which are components of the present invention, will be described in detail.

The OCT 200 is a configuration capable of obtaining a tomographic shape of an inspection target using optical coherence tonograpy technology, and obtains inspection light and reference light by separating light from the same light source 210, The inspection light is reflected on the inspection object and then incident on the spectrometer 250, and the reference light is reflected on the reference arm 230 provided therein and then incident on the spectrometer 250. As known in the art of optical coherence tomography, the spectrometer 250 obtains a difference in the optical path distance between the inspection light and the reference light by analyzing the interference light because the interference light is incident by the synthesis of the inspection light and the reference light. .

According to the present invention, the OCT 200 is coupled to the focus adjustment optical system 310, so that the inspection light is output through the focus adjustment optical system 310 and reflected on the workpiece 1, and then the focus adjustment optical system 310 is provided. And the reference light is output to be irradiated toward the workpiece 1 before welding, and is combined with the incident inspection light after proceeding the same optical path distance as the incident inspection light, so that it is reflected to be detected by the spectrometer 250. It is configured to position the reference arm 230.

According to a specific embodiment, the OCT 200 separates the light output from the light source 210 with a beam splitter 220, and uses the light passing through the beam splitter 220 as inspection light, and the beam splitter 220 The light reflected and deflected by 90° is used as the reference light, and the inspection light is transmitted through the dichroic mirror 312 of the focus adjusting optical system 310 to be irradiated onto the workpiece 1 by the focus adjusting lens 313. It is coupled to the optical system 310. Accordingly, the inspection light reflected on the workpiece 1 is returned to the beam splitter 220.

The reference light is reflected by the reference arm 230 to return to the beam splitter 220, and a linear driving device 240 for adjusting the distance between the beam splitter 220 and the reference arm 230 is provided. At this time, the linear drive device 240 is operated by a controller 400 to be described later, so that the reference light path distance D2 from the beam splitter 220 to the reference arm 230 is determined to the surface of the workpiece 1 before welding. It is made equal to the inspection light path distance D1 to.

In addition, since the spectrometer 250 is disposed facing the reference arm 230 with the beam splitter 220 interposed therebetween, the reference light transmitted through the beam splitter 220 and reflected by the beam splitter 220 are deflected by 90°. As the inspection light is incident, the interference light due to the synthesis of the reference light and the inspection light can be analyzed. That is, the spectrometer 250 obtains a difference in the optical path distance between the reference light and the inspection light generated by the surface of the workpiece 1 that is deformed by melting during welding.

In the first embodiment of the present invention, since the OCT 200 is coupled to the focusing optical system 310 so that the inspection light and the laser beam are irradiated to the workpiece 1 with the same optical axis, a key hole generated during welding Hole) depth is obtained as a difference in the optical path distance obtained by the spectrometer 250.

Looking at the state of the workpiece 1 during welding shown in FIG. 1, a welding bead 4 is formed at the position where the laser beam B1 has passed, and the workpiece 1 is melted at the position where the laser beam B1 is irradiated. As a result, a key hole is formed, and a melted paper 3 is also formed. Accordingly, the inspection light B2 irradiated with the same optical axis as the laser beam B1 penetrates into the key hole and is reflected on the inner floor of the key hole.

That is, the reference light is incident on the spectrometer 250 after reciprocating the optical path distance (D2 = D1) equal to the optical path distance D1 to the surface of the workpiece 1 before welding based on the beam splitter 220, The spectrometer 250 analyzes the interference between the inspection light and the reference light to obtain an optical path distance difference that is twice as much as the key hole depth, and through this, it is possible to obtain the key hole depth. .

Here, the obtained key hole depth can be viewed as a substantially penetration depth, because the thickness of the melted paper 3 at the bottom of the key hole is very thin.

Among the components of the OCT 200, the collimating lenses 211 and 231, which are not described above, convert the light output from the light source 210 into parallel light, and the reference light and the inspection light obtained by being separated from the beam splitter 220 are also parallel light. The collimating lens 211 and the reference light reflected by the beam splitter 220 to become parallel light are condensed to be reflected on the reference arm 230, and the reflected reference light is converted into parallel light, thereby forming the beam splitter 220. As a collimating lens 231 facing, it is internally treated as parallel light.

Here, since the collimating lens 231 installed on the side of the reference arm 230 is focused on the reference arm 230, it is moved by the linear driving device 240 together with the reference arm 230.

The controller 400 controls the light source 210, the linear driving device 240, and the spectrometer 250 of the OCT 200 to perform an OCT setting operation before welding and a monitoring operation during welding.

In the description of the embodiment of the present invention, the controller 400 is integrally configured with the control unit of the welding device to perform a control operation for the welding process. Also, in the drawing, the laser oscillator 100 and the optical system 310 for focusing It is shown that the welding process is performed by controlling the focus adjustment lens 313. This is because the controller 400 is connected to the control unit of the welding device to link the OCT setting operation before welding and the monitoring operation during welding to the welding process, and it will be described as being configured as an integral type for convenience. In reality, it is connected to a control unit that controls the welding process of the welding device to be performed, so that the welding progress is recognized, and according to the welding progress, the OCT setting operation before welding and the monitoring operation during welding are performed.

The welding process is a conventional process of forming a welding line by focusing a laser beam on the workpiece 1. In addition, as described in Korean Patent Publication No. 10-2016-0060112 referred to as a background art, the laser welding device fixes a head configured by combining a laser oscillator 100 and an optical system for focusing 310 to the movable arm of the robot. In addition, since the robot is operated to direct the head to the workpiece 1, the head is moved along the intended direction, and a welding line is formed on the workpiece 1, the welding process also includes an operation of controlling the robot. Since the control operation for performing such a welding process is a known technique, a detailed description will be omitted, and an OCT setting operation and a monitoring operation will be described.

The OCT setting operation is an operation to adjust the reference light path distance of the OCT 200 to the inspection light path distance before performing the welding process. When the distance between the workpiece (1) is aligned with the distance during laser welding, the laser beam Without irradiation, the OCT 200 is operated, and the difference in the optical path distance between the inspection light reflected by the workpiece 1 before welding and the reference light reflected on the reference arm 230 is checked through the spectrometer 250, This is an operation of varying the position of the reference arm 230 by the linear driving device 240 so that the difference in the optical path distance becomes '0'.

When the difference in the optical path distance becomes '0', the welding process is performed, and a monitoring operation is performed simultaneously with the welding process.

The monitoring operation is an operation of operating the OCT 200 while performing the welding process to monitor the difference in the optical path distance obtained by the spectrometer 250.

According to the first embodiment of the present invention, the depth of the key hole is measured from the difference in the obtained optical path distance.

2(a) is a graph showing the key hole depth measured in real time. As shown in Fig. 2(a), the keyhole gradually deepens while the laser beam is irradiated, and the inspection light may be reflected by various foreign substances, so the depth value 10' during the deepening of the keyhole is also measured. .

Accordingly, in an embodiment of the present invention, the maximum value for each section is recorded as the keyhole depth 10 of the section by dividing the keyhole depth acquired in real time during welding by a predetermined period. That is, when laser welding is performed while welding is carried out at a generally constant speed, the maximum value for each section is selected by dividing the acquired key hole depth by section of a predetermined period and selecting the actual key hole depth as shown in FIG. 2. Accordingly, it is possible to obtain the measured keyhole depth.

FIG. 2(b) is a photograph of a cross section taken by cutting the workpiece 1 after welding in four exemplary locations. As a result of checking the penetration depth, it was confirmed that it was almost identical to the measured key hole depth.

3 is a graph (a) showing the measured key hole depth and penetration depth of the welded workpiece and a photograph of the longitudinal section of the welded workpiece (b). Here, in the graph of FIG. 3(a), the key hole depth 10 is slightly shifted in the x-axis direction compared to the penetration depth 20 checked after welding, so it should be noted that the comparison is better.

Looking at the graph of FIG. 3(a), it can be seen that the penetration depth 20 determined by cutting along the welding line and the key hole depth 10 obtained by measuring are almost identical over the entire section of the welding line. That is, it can be seen that the key hole depth 10 obtained by the OCT 200 during welding reflects the penetration depth well.

4 is a block diagram of a monitoring system for inspecting a laser weld according to a second embodiment of the present invention.

According to the second embodiment of the present invention, the inspection optical system 320 is disposed between the OCT 200 and the focus adjustment optical system 310, so that the inspection light passes through the inspection optical system 320.

After the inspection optical system 320 is optically separated by the beam splitter 220 of the OCT 200, the inspection light generated by two total reflection mirrors 321 and 322 is paralleled by 90° in two stages, and the The optical system for focus adjustment 310 may be transmitted, but by rotating any one of the total reflection mirrors 322, the optical axis of the inspection light transmitted through the optical system for focusing 310 may be varied.

In other words, the inspection light having an optical axis shifted from the optical axis of the laser beam radiating toward the workpiece 1 can be radiated toward the workpiece 1, so that the inspection light can be irradiated toward the periphery of the area being welded by the laser beam. I can. Of course, the irradiated inspection light is reflected so that it is optically matched to reach the spectrometer 250 by the beam splitter 220 of the OCT 200 by sequentially transmitting the focus adjustment optical system 310 and the inspection optical system 320 I did.

Accordingly, the controller 400 may inspect the periphery of the portion being welded on the surface of the workpiece 1 by controlling the rotation device 323.

For example, as illustrated in FIG. 5, the rotation device 323 may be controlled to inspect the direction in which the inspection light is irradiated in advance of the area being welded, that is, the area before welding.

As another example, as shown in FIG. 6, both the front and rear of the area being welded may be inspected. That is, in order to alternately inspect the front and rear of the area being welded by the laser beam on the welding line, after irradiating the inspection light (B2) in front of the area being welded by the laser beam (B1), the rear of the area being welded The rotation device 323 of the inspection optical system 320 is controlled to repeat the operation of irradiating the inspection light B2, and the difference in the optical path distance obtained through the spectrometer 250 is separated into front and rear values, The back surface can be obtained and inspected according to the surface shape.

6(b) shows the direction in which the inspection light B2 is irradiated and scanned when inspecting the front and rear of the area being welded. According to this, a predetermined distance is scanned in the width direction of the welding line 1 (S1, S2).

That is, by scanning the front side in the width direction (S1), the area to be welded in the future can be inspected. For example, when performing fillet welding or butt welding, the welding position can be detected by obtaining the optical path distance difference obtained by scanning the front side and obtaining the surface shape of the scan range. Can be used to correct.

In addition, by scanning the rear in the width direction (S2), the surface shape of the welding bead 4 can be obtained from the difference in the optical path distance obtained along the scanning direction, and the welding state is inspected according to the surface shape at this time, and the welding strength, etc. It can be used to calibrate the welding parameters of.

Although not shown, it is also possible to sequentially repeat the key hole depth measurement, front inspection, and rear inspection during welding.

In addition, before performing the welding process, only the OCT 200 may be operated to inspect the entire area to be welded before welding, or the entire welding line may be inspected after welding by operating only the OCT 200 after performing the welding process. .

In the second embodiment of the present invention in which the inspection optical system 320 is added as described above, as shown in FIG. 4, the optical path distance of the inspection light according to the addition of the inspection optical system 320 is increased (D12, D13). The position of the reference arm 230 is adjusted to increase the optical path distance of light. However, if it is used to obtain a tomography image by detecting only the shape in the scan direction in the anterior and posterior inspections, the optical path distances of the reference light and the inspection light may not be matched and may be fixed to a certain position.

On the other hand, the optical system for inspection 320 is not limited to the configuration shown in the drawing, and an optical system for varying the optical path of the inspection light is satisfied.

The focus adjustment optical system 310 is configured to vary the direction of light irradiation toward the workpiece, but also in this case, since the irradiation direction of the inspection light along with the laser beam is varied, the keyhole depth measurement, the front inspection and the rear inspection are all You can do it.

Although shown and described in specific embodiments to illustrate the technical idea of the present invention, the present invention is not limited to the same configuration and operation as the specific embodiment as described above, and various modifications are within the scope of the present invention. Can be carried out in Therefore, such modifications should be regarded as belonging to the scope of the present invention, and the scope of the present invention should be determined by the claims to be described later.

1: processed object 2: key hole
3: Weld Pool 4: Bead
100: laser oscillator
200: OCT (Optical Coherence Tomography)
210: light source 211: collimating lens
220: beam splitter 230: reference arm
231: collimating lens 240: linear driving device
250: spectrometer
310: focus adjustment optical system 311: collimating lens
312: dichroic mirror 313: focusing lens
320: inspection optical system 321, 322: total reflection mirror
323: rotating device
400: controller

Claims (6)

Laser oscillator 100; And a focus adjustment optical system 310 for radiating and welding the laser beam of the laser oscillator 100 to focus on the workpiece 1. In the monitoring system for inspecting the laser weld in the welding device including,
By separating the light from the same light source 210, the inspection light and the reference light are obtained, and the inspection light is coupled to the focusing optical system 310 so that it is reflected and incident on the workpiece 1 through the focus adjustment optical system 310, and the reference light Is made to proceed with the same optical path distance as the optical path distance of the inspection light before welding, and then synthesized with the incident inspection light, and the interfering light generated by the synthesis is analyzed by the spectrometer 250 and the difference in the optical path distance between the inspection light and the reference light OCT (Optical Coherence Tomography, 200) configured to obtain a; And
A controller 400 for receiving and monitoring a difference in optical path distance from the OCT 200;
Including
Monitoring system for laser welding inspection. The method of claim 1,
The OCT 200 is
The inspection light and the laser beam are coupled to the focusing optical system 310 so that they have the same optical axis, and the depth of the key hole 2 generated during welding is obtained by the difference in the optical path distance,
The controller 400 is
By dividing the depth of the key hole (2) acquired in real time during welding by a certain period, the maximum value for each section is recorded as the depth of the key hole (2) of the section.
Monitoring system for laser welding inspection. The method of claim 1,
The OCT 200 is
Among the light of the light source 210, the light transmitted through the beam splitter 220 is used as the inspection light, and the light reflected by the beam splitter 220 is used as the reference light, and the reference light is reflected to the reference arm 230 to reflect the beam splitter 220. The light path distance (D2) from the beam splitter 220 to the reference arm 230 and the light path distance to the surface of the workpiece 1 before welding (D1) In order to equally adjust the reference arm 230 to the linear driving device 240, the reference light reflected by the workpiece 1 and incident on the beam splitter 220 is reflected to the spectrometer 250 Organized
Monitoring system for laser welding inspection. The method of claim 3,
The controller 400 is
Controls the linear driving device 240 so that the difference in the optical path distance between the inspection light reflected by the workpiece 1 before welding and the reference light reflected on the reference arm 230 becomes '0'.
Monitoring system for laser welding inspection. The method of claim 1,
An inspection optical system 320 capable of shifting the optical axis of the laser beam by varying the optical axis of the inspection light is provided between the OCT 200 and the focus adjustment optical system 310,
The controller 400 is
By controlling the inspection optical system 320, it is possible to obtain a difference in the optical path distance in the width direction of the surface before and after welding by scanning the front and rear of the area being welded by a laser beam on the welding line in the width direction of the welding line.
Monitoring system for laser welding inspection. The method of claim 5,
The controller 400 is
It is possible to correct the position to be welded with a laser beam according to the difference in the optical path distance obtained by scanning the front of the area being welded.
Monitoring system for laser welding inspection.

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