JP2006187794A - Seam tracking welding apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seam tracking welding apparatus which can accurately track a welding line by bringing a circular sensing roller into contact with a workpiece and by feeding-back the positional change of the roller to a laser beam machine in a real time. <P>SOLUTION: The seam tracking welding apparatus is integrated with a laser transmitter 1 by means of a mounting stay 13 and has the circular sensing roller 6 which is arranged at the tip end portion so as to turn with low friction by means of a rotary shaft A. The sensing roller 6 is always brought into contact with a welding workpiece W2 during measurement because of the elastic force of a spring 8 transmitted via a fulcrum 10. Further, a stopper 12 is provided such that the sensing roller 6 is not excessively tilted by the tension force of the spring 8 applied in such a non-contact state that the sensing roller 6 moves in the air. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a seam tracking welding apparatus that detects a butt weld line in real time.

In the butt welding process using laser, welding workpieces made of a plurality of sheet metal members are butted together, the boundary line thereof is used as a welding line, and the workpiece member is joined by irradiating laser light along the welding line.
In this butt welding process, welding defects are likely to occur due to variations in the shape and dimensions of the sheet metal member that is the raw material, variations in the positioning accuracy of the jig, and the product yield is not at a satisfactory level.
In other words, the position of the weld line slightly changes each time, so that the laser beam that should be accurately irradiated on the weld line is deviated from the weld line, which causes welding failure and sufficient welding strength is obtained. Result in not.
In addition, if the weld bead is displaced with respect to the weld line, the appearance is deteriorated, and a problem occurs in both strength and appearance.

In spite of the above situation, in recent years, the demands on the quality and appearance of the welded product are becoming stricter, and among them, high-precision tracking of the weld bead to the weld line is strongly demanded.
This is the most basic and important requirement, but there are currently no low-cost products that can be stably operated. Realization of a welding support system has been demanded.

In order to respond to such a user's request, there are some known examples of adjusting the laser light irradiation position while tracking in real time in order to prevent the laser light irradiation position from deviating from the weld line. Many of these employ optical measurement using various image sensors as a method for detecting a weld line.
However, the identification method using an image sensor cannot be operated under the condition that the laser beam for measurement is blocked, so that the application range is limited and sufficient results have not been achieved.

  FIG. 1 shows the workpiece W1 and the laser transmitter 1 viewed from the side, and the lens 2 optically applies the laser light generated by the laser transmitter 1 to the workpiece W1 and the plurality of workpieces W2. The welded portion 14 is irradiated with the laser beam L1 adjusted to.

FIG. 2 is a perspective view of the workpieces W1 and W2.
In this case, the boundary between the workpieces W1 and W2 becomes the weld line 20. The quality of the product depends on how accurately the laser beam can be irradiated along the weld line 20.
That is, if the laser beam irradiation deviates from the weld line 20, not only the welding strength is lowered, but also the appearance of the weld bead that becomes the weld trace is remarkably impaired and the commercial value is greatly impaired.

As a method for coping with the welding line deviation described above, it is common to detect the welding line by an optical measuring device 3 as shown in FIG.
In the method based on the optical measurement method, an optical measurement device 3 is provided in the vicinity of the laser transmitter 1, and the measurement laser light L2 is irradiated in a pulse form from the laser light emitting unit 4 in the optical measurement device 3, which is processed around the weld line. Reflected by the surfaces of the workpieces W1 and W2, the reflected laser light L3 is individually captured by the laser light receiving unit 5, and each pulse light is recognized as a number of three-dimensional coordinate points by the principle of triangulation, and welded. A line boundary is inferred by calculation as a change in the coordinate group and extracted.

However, since the measurement result obtained by the above method is three-dimensional point group data, a large number of point group data is required to recognize and determine the shape as a three-dimensional shape.
In other words, a certain width is given to the assumed weld line, and the three-dimensional point cloud data is measured in a strip shape, but the feed rate of laser processing machines already in operation is relatively high. Therefore, it is not easy to secure a measurement speed and a processing speed corresponding to this.
In addition, the measurement by the optical method is susceptible to errors due to the reflection of the workpiece surface and its angle, etc., and there are various restrictions on the operation, and sufficient caution is required.

In the optical measurement as described above, since reflected light must be supplemented, sufficient attention must be paid to the irradiation angle and the positional relationship with the workpiece.
For example, in the situation shown in FIG. 4, the reflected light L3 of the measurement laser L2 can be supplemented. However, in the situation shown in FIG. 5 where the number of workpieces W2 has increased, the reflected light L3 interferes with the workpiece W2. Therefore, the measurement laser beam is easily blocked by the measurement laser beam, and the measurement laser beam is easily blocked by the irradiation position and irradiation angle of the measurement laser.
It is extremely problematic to interrupt the laser processing in the middle, and even if it starts again from the point where it was interrupted again, there remains a problem in the welding quality. Therefore, the possibility that the measurement is delayed as described above is a large operational risk.

Also, when it is desired to measure coordinates in real time while processing, it is greatly affected by the reflected light and scattered light of the processing laser light, and normal measurement cannot be expected.
Thus, there were many operational restrictions and it was not something that could be used with confidence.
JP 05-146885 A JP-A-10-311706 JP-A-10-311707

  According to the present invention, in a workpiece having a three-dimensional shape, in the conventional detection of a welding line by optical measurement, a situation in which measurement light and reflected light interfere with the workpiece and the measurement is interrupted easily occurs. The purpose of this is to provide a seam tracking welding apparatus that detects a weld line in real time.

According to a first aspect of the present invention, a laser transmitter for irradiating a laser beam close to a sheet metal workpiece is provided at the tip of the robot arm,
On the other hand, a disk-shaped sensing roller that can rotate itself while contacting the workpiece with the contact pressure of the spring's elastic force against the workpiece surface near the workpiece weld line, and to detect the displacement of this sensing roller Differential transformer,
A displacement detection unit is configured with a link mechanism for transmitting the displacement of the sensing roller to the differential transformer,
The displacement detector is arranged at the tip further than the laser transmitter by a stay, and is integrated with the laser transmitter,
The sensing roller is set to a length and a configuration position that protrude further downward than the displacement detection unit by an amount corresponding to the vertical undulation of the workpiece,
The displacement signal measured from the displacement detection unit is transmitted in real time to the control device of the laser processing machine that is the main body, and this is immediately fed back to the position control without stagnation, thereby correcting the misalignment between the welding line and the laser irradiation. And
According to a second aspect of the present invention, two sets of displacement detectors are arranged orthogonally to perform feedback position control in two axial directions simultaneously.

As described above, according to the seam tracking welding apparatus of the present invention, the sensing roller that contacts the workpiece is protruded downward to suppress interference with the workpiece, and the shape is directly recognized by detecting the displacement of the sensing roller. By feeding this back to the position control of the laser processing machine in real time, the conventional arithmetic processing consisting of complicated image processing can be eliminated, and simple but stable and highly accurate laser processing can be performed.
Furthermore, by arranging two sets of displacement detectors orthogonally, feedback position control in the biaxial direction can be performed, and more accurate seam tracking is possible.

Since the seam tracking device of the present invention directly recognizes the workpiece shape with a rotatable circular sensing roller, it operates stably while ensuring practical measurement accuracy, its structure is simple, and it is manufactured and operated at low cost. There are advantages you can do.
Moreover, since the control logic required for operation may be relatively easy to handle based on simple feedback control, there is an advantage that it can be easily applied to various welding robots.

  The seam tracking device of the present invention has a simple purpose of supplying the market with seam tracking for detecting a weld line that has necessary and sufficient accuracy and stability, has excellent controllability, and is easy for users to operate. This is realized at a low cost by the apparatus configuration, and will be described below by an embodiment.

FIG. 6 is a side view showing the first embodiment of the seam tracking device according to the present invention, which is integrated with the laser transmitter 1 by the mounting stay 13.
A circular sensing roller 6 that can rotate with a low friction and has a rotational axis A is provided at the tip, which always contacts the workpiece W2 during measurement by the elastic force of the spring 8 via the fulcrum 10. is doing.
In addition, a stopper 12 is provided to prevent the sensing roller 6 from tilting excessively due to the pulling force of the spring 8 in a non-contact state such as when the sensing roller 6 moves in the air.

If a deviation occurs between the assumed workpiece position and the actual workpiece position, the displacement of the sensing roller 6 is transmitted to the contact point 19 via the fulcrum 10 to move the probe 18.
The advance / retreat of the probe 18 is precisely measured by the differential transformer 9 and is transmitted as an analog signal to the control unit of the laser processing machine via the signal line 11 for use in feedback control.

FIG. 7 describes the displacement of the sensing roller and its feedback control.
FIG. 7A shows a state where the sensing roller 6 is in ideal contact with the workpiece, and is neutral in terms of control.
FIG. 7B shows a rushing state. In this situation, the inclination of the sensing roller 6 is detected as a positive displacement by the differential transformer 9, so that the amount of displacement detected is offset by the control device of the laser processing machine. By retracting, it is possible to return to the neutral state as shown in FIG.
FIG. 7D shows a situation opposite to the above, but it is possible to return to the neutral state by correcting the coordinates as much as the amount of displacement is canceled in the same manner as described above.

FIG. 8 shows the positional relationship between the sensing roller 6 and the processing laser beam L1 to be irradiated.
Since the laser beam is irradiated at a distance from the rear of the traveling direction of the sensing roller 6 so that there is no thermal influence, the sensing roller 6 and the welded portion 14 must be at a certain distance.
When the above distance is regarded as a problem due to changes in the roller diameter or workpiece shape, feedback control is performed in consideration of this distance, which is reflected in the correction of the position where the laser beam is irradiated.

FIG. 9 shows variations of the shape of the sensing roller 6.
FIG. 9A shows a standard shape. In this shape, it is necessary to secure a slight gap in consideration of the contact between the lower part of the sensing roller 6 and the workpiece W1 and the inclination of the sensing roller.
On the other hand, FIG. 9B changes the shape of the sensing roller to enable detection of a portion closer to the weld line.
Further, in FIG. 9C, by making the bottom of the sensing roller elliptical, even if the sensing roller 6 ″ contacts the workpiece W1, the frictional resistance can be suppressed low.
As described above, it is possible to appropriately change the shape of the sensing roller according to the required content such as the workpiece shape and measurement conditions.

The seam tracking welding apparatus according to the first embodiment has the following effects.
Suppressing the sensing roller that touches the workpiece to work downward suppresses the interference with the workpiece, and the shape is directly recognized by detecting the displacement of this sensing roller, which is fed back to the position control of the laser machine in real time. Thus, it is possible to eliminate the conventional arithmetic processing consisting of complicated image processing, and to perform stable and highly accurate laser processing while being simple.

Next, the second embodiment will be described.
The above was related to seam tracking based on measurement in only one axis direction, but by arranging and mounting two sets of displacement detectors orthogonal to each other, simultaneous correction in two axis directions is possible. Is shown in FIG.
The configuration related to the sensing roller 6 for the side surface direction is the same as that described in the first embodiment, and this is combined with the sensing roller 6 ′ ″ for detecting the vertical direction.

According to the above configuration, since it is possible to follow a change in the position in the downward direction, it is particularly effective when it is desired to weld a workpiece having a three-dimensional shape.
This is an effective system for inputting a basic trajectory in advance by teaching and following the weld line with higher accuracy than in teaching in actual welding, and can reduce the work load of conventional teaching.
In addition, by tracking the welding line with high accuracy by the sensing roller, even if the spot diameter of the laser beam for processing to be irradiated is small, the small laser beam spot can be traced without detaching from the welding line. Accuracy can be improved.

According to the present invention, in addition to the category of seam tracking based on the detection of a weld line, there is also a potential digitizing function by copying the workpiece shape.
That is, it is possible to prevent a defective product from leaking to a subsequent process by detecting an undefined deformation of the workpiece and displaying an alarm.
Measurement with a differential transformer is generally highly accurate and can sufficiently measure distortion after welding, etc., reducing welding defects themselves and enabling inspection of defective products themselves with a single machine. .

It is an external view of the conventional apparatus which shows the condition which irradiates a process laser to a workpiece | work. It is a perspective view of the conventional apparatus which shows the workpiece | work for a process, and its weld line. It is an external view of the seam tracking system based on the conventional optical measurement. It is explanatory drawing which shows irradiation and reflection of the conventional laser beam for a measurement. It is explanatory drawing which shows a mode that reflection of the conventional laser beam for a measurement is interrupted | blocked. 1 is a configuration diagram of a seam tracking device according to a first embodiment of the present invention. It is an effect | action figure which shows the displacement and feedback of the said sensing roller. It is a perspective view which shows the irradiation position of the said sensing roller and a processing laser. It is sectional drawing of various sensing rollers. It is a block diagram of the seam tracking apparatus of 2nd Embodiment using two sensing rollers.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser transmitter 2 Lens 3 Optical measuring device 4 Laser light emission part (optical measuring device)
5 Laser Participation Department (Optical Measuring Device)
6 Sensing roller 7 Strut 8 Spring 9 Differential transformer 10 Supporting point 11 Signal line 12 Stopper 13 Mounting stay 14 Welded portion 15 Weld bead 16 Traveling direction 17 Rotating direction 18 Probe 19 Contact point 20 Welding line A Rotating axis L1 Laser beam L2 for processing Laser beam for measurement L3 Laser beam for measurement (reflected light)
W1 Machining workpiece (base side)
W2 Machining workpiece (additional side)

Claims (2)

A butt laser welding process for joining sheet metal workpieces with laser light,
A laser transmitter for irradiating a laser beam close to the sheet metal workpiece is provided at the tip of the robot arm,
On the other hand, a disk-shaped sensing roller that can rotate itself while contacting the workpiece with the contact pressure of the spring's elastic force against the workpiece surface near the workpiece weld line, and to detect the displacement of this sensing roller Differential transformer,
A displacement detection unit is configured with a link mechanism for transmitting the displacement of the sensing roller to the differential transformer,
The displacement detector is arranged at the tip further than the laser transmitter by a stay, and is integrated with the laser transmitter,
The sensing roller is set to a length and a configuration position that protrudes further downward than the displacement detection unit by an amount corresponding to the vertical undulation of the workpiece,
The displacement signal measured from the displacement detection unit is transmitted in real time to the control device of the laser processing machine as the main body, and this is immediately fed back to the position control without stagnation, thereby correcting the misalignment between the welding line and the laser irradiation. Seam tracking welding equipment.   The seam tracking method according to claim 1, wherein two sets of displacement detectors are arranged orthogonally to perform feedback position control in two axial directions simultaneously.

Images