JPH11192573A - Laser processing apparatus and processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable continuous welding at an applied section and to improve water-tightness, rigidity and strength by combining a device measuring the laser reflected light intensity from a processing point, a device for vibrating a condenser optical system and a device for controlling the relative distance between the condenser optical system and the processing point and making online correction of the misalignment of a focal position. SOLUTION: The reflection from the laser beam 2 from the processing point 10 is less when laser welding is keyhole welding and good welding quality is obtd. The formation of the keyhole at the processing point 10 is no longer possible when the focal density changes and the power density at the processing point 10 changes and falls below a certain threshold. Consequently, the laser beam reflectivity from the processing point 10 increases and the reflectivity when the keyhole is not formed attains about 60%. An oscillation device control section 15 receives the time signal attaining the differential peak value of the reflected light intensity from a photodetecting intensity computing section 14 and corrects the central value of amplitude to a correct direction from the position of the condenser optical system 8 of this time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a laser processing apparatus and a processing method.

[0002]

2. Description of the Related Art In welding a YAG laser lap joint of steel, aluminum, or the like, a joint shape as shown in FIG. 6 can be considered. In the figure, reference numeral 2 denotes a laser beam, 9 denotes a material to be welded, 1
0 is a processing point and 11 is a fusion zone.

The joint shape A is the most common lap joint shape, in which two overlapping workpieces 9 are irradiated with a laser beam 2 from a vertical direction to perform joining. The joint shape B is
Fillet joint shape. By irradiating the laser beam 2 to the corner of the workpiece 9 on one side, the two workpieces 9 are joined. In the joint shape C, the laser beam 2 is irradiated to the end of the flange of the workpiece 9 to join the two workpieces 9 together. In the joint shape D, the laser beam 2 is irradiated to the flange fitting portion of the material to be welded 9 from the direction opposite to the flange end, and the two materials to be welded 9 are joined. When the material to be welded 9 is a press-formed product, the two materials to be welded 9 are
Variations are likely to occur at the positions where they come into contact.

As a conventional laser processing apparatus, there is one having a structure as shown in FIG. 7, for example. In the figure, reference numeral 2
Is a laser beam, 5 is an optical fiber, 6 is a laser processing head,
7 is a collimator, 8 is a condensing optical system, 9 is a material to be welded, 10
Denotes a processing point, 11 denotes a fusion zone, 16 denotes a joint gap correcting roller, and 17 denotes a stay for maintaining a relative distance between the gap correcting roller and the processing head.

In this prior art, a laser beam is applied to a processing point 10 while correcting a joint gap of a workpiece 9 by a holding jig using a roller 16 or the like for controlling a relative position with respect to a processing head 6 (a condensing optical system 8). Light 2 is irradiated to perform bonding. The distance between the processing point 10 and the condensing optical system 8 depends on the gap correcting roller 1.
Since it is maintained at a constant distance by the stay 6 and the stay 17, the focal position at the processing point 10 can always be kept at a set value, and stable welding quality can be obtained.

[0006]

In such a conventional laser processing apparatus, however, the control of the relative distance between the processing point 10 and the condensing optical system 8 is controlled by the pressing roller 16 which serves to correct the gap. Impossible joint shapes, for example,
In the joint shapes C and D shown in FIG. 6, since stable welding cannot be performed, stable welding quality cannot be obtained, and continuous welding, which is a characteristic of laser, cannot be performed.
There is a problem that there is no watertightness or the rigidity is reduced.

The present invention has been made in view of such a conventional problem. By measuring the reflected light of the laser beam from the processing point 10 and correcting the focal position shift online, the above problem can be solved. It is intended to solve.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 measures the intensity of YAG laser light reflected from a processing point during welding in YAG laser welding. The present invention is characterized in that a focus position shift of a processing point is detected from reflected light intensity and the focus position is corrected online.

According to a second aspect of the present invention, in the YAG laser welding, the YA which reflects from a processing point during welding while vibrating a condensing optical system in a direction perpendicular to a material to be welded.
Measures the intensity of the G laser light, detects the direction of the focal position shift of the processing point from the phase of the time derivative of the reflected light intensity and the phase of the condensing optical system position, and corrects the focal position online. It is assumed that.

[0010] Further, the invention according to claim 3 is a method for producing a YAG
In laser welding, the intensity of YAG laser light reflected from a processing point during welding is measured while oscillating the condensing optical system in the direction perpendicular to the material to be welded at a depth of focus or less, and the reflected light intensity is measured. The method is characterized in that the direction of the focal position shift of the processing point is detected from the phase of the time differential value and the phase of the position of the condensing optical system, and the focal position is corrected online.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a laser processing apparatus and a processing method according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of an embodiment of a laser processing apparatus and a processing method according to the present invention. Also,
FIG. 2 is a schematic diagram showing the relationship between the focal position and the laser beam reflection intensity. FIGS. 3 to 5 show the case where the distance between the workpiece 9 and the condensing optical system 8 is appropriate and the welding quality is good, respectively.
When the distance between the workpiece 9 and the condensing optical system 8 is too short to cause welding failure, when the distance between the workpiece 9 and the condensing optical system 8 is too long to cause welding failure, the present invention FIG. 9 is a diagram comparing the positions of the condensing optical system 8 with the laser reflected light intensity and the time derivative thereof according to the embodiment.

First, the structure will be described. In FIG.
Reference numeral 1 denotes a YAG laser oscillator, 2 denotes a laser beam, 3 denotes a half mirror, 4 denotes an output window, 5 denotes an optical fiber, 6 denotes a laser processing head, 7 denotes a collimator, 8 denotes a condensing optical system, 9
Is a workpiece, 10 is a processing point, 11 is a fusion zone, 12 is a bandpass filter, 13 is a light receiving unit, 14 is a light receiving intensity calculation unit, and 15 is an oscillation control unit.

Referring to FIG. The laser light 2 oscillated from the YAG laser oscillator 1 is transmitted to the transmission optical system (4, 4).
5, 7, 8), and reaches the processing point 10. Processing point 1
The laser light 2 reflected at 0 hits the half mirror 3 through the same path and is reflected in the direction of the light receiving unit 13. The bandpass filter 12 disposed immediately before the light receiving unit 13 blocks light other than the laser reflected light from the processing point 10,
The light receiving unit 13 measures only the reflected laser light 2.
The measured reflected light intensity is time-differentiated by the received light intensity calculation unit 14, and the peak value is output to the oscillation control unit 15. The oscillation control unit 15 calculates the focal position shift from the signal from the received light intensity calculation unit 14 and the phase of the light collecting optical system 8, and corrects the distance.

As the material 9 to be welded in the present embodiment, an aluminum alloy A6N01-T5 and a thickness t = 20 mm were used. The welding conditions were a processing point output of 4.0 kW and a processing speed of 3 m.
/ Min. , The focal length of the collimator was 200 mm, the focal length of the condensing optical system was 150 mm, and the focal position was just focused. The condensing optical system has an amplitude of 0.3mm and a frequency of 50H
The experiment was performed at z.

The evaluation was performed by evaluating the appearance of the weld bead and observing the cross section. The required quality is that no blowholes are generated and the penetration shape is a deep penetration shape. The welding quality in the present embodiment satisfied the required quality.

Next, the operation of the present embodiment will be described. When laser welding is keyhole welding and good welding quality is obtained, the reflection of laser beam 2 from processing point 10 is small (20% or less). When the focal position changes, the power density at the processing point 10 fluctuates. When the power density falls below a certain threshold, a keyhole cannot be formed at the processing point 10. As a result, the reflectance of the laser beam from the processing point 10 increases, and the reflectance when no keyhole is formed is about 60% (see FIG. 2).

The condensing optical system 8 is oscillated in the laser irradiation direction by an oscillation device with an amplitude smaller than the depth of focus.

When the converging optical system 8 is vibrating within a proper range of the distance between the converging optical system 8 and the processing point 10, the position of the converging optical system 8 with respect to time, the intensity of reflected laser light, and the time The relation of differentiation is as shown in FIG.

When the distance between the converging optical system 8 and the processing point 10 is shorter than an appropriate range, the converging optical system 8 is vibrating at a shorter distance than the position of the converging optical system 8 with respect to time and the reflected laser beam. The relationship between the intensity and its time derivative is as shown in FIG. 4, and the differential value of the reflected light intensity has a peak at the point where the condensing optical system 8 approaches the processing point 10.

When the distance between the converging optical system 8 and the processing point 10 is longer than an appropriate range, the converging optical system 8 vibrates at a position longer than the appropriate range. The relationship between the intensity and the time derivative thereof is as shown in FIG. 5, and the differential value of the reflected light intensity reaches a peak at a point where the light-collecting optical system 8 moves away from the processing point 10.

The oscillation device control unit 15 receives the time signal from the received light intensity calculation unit 14 that takes the differential peak value of the reflected light intensity, and calculates the time signal from the phase of the condensing optical system 8 at that time.
The center value of the amplitude is corrected in an appropriate direction.

[0022]

As described in detail above, according to the present invention, the structure of the present invention includes an apparatus for measuring the intensity of the laser reflected light from the processing point 10, an apparatus for oscillating the condensing optical system 8,
In addition, since the combination of the device for controlling the relative distance between the condensing optical system 8 and the processing point 10 is obtained, the effect of stabilizing the welding quality is obtained. As a result, continuous welding at the application site becomes possible, The effect of improving rigidity is obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a laser processing apparatus and a processing method according to the present invention.

FIG. 2 is a schematic diagram showing a relationship between a focal position and a laser beam reflection intensity.

FIG. 3 shows the position of the condensing optical system 8 according to the embodiment of the present invention, the intensity of laser reflected light, and the time derivative thereof when the distance between the workpiece 9 and the condensing optical system 8 is appropriate and the welding quality is good. It is the figure which compared the phase with the value.

FIG. 4 shows the position of the condensing optical system 8 according to the embodiment of the present invention, the intensity of laser reflected light, and the time derivative thereof when the distance between the workpiece 9 and the condensing optical system 8 is too short to cause welding failure. It is the figure which compared the phase with the value.

FIG. 5 shows the position of the condensing optical system 8 according to the embodiment of the present invention, the intensity of laser reflected light, and the time derivative thereof when the distance between the workpiece 9 and the condensing optical system 8 is too large to cause welding failure. It is the figure which compared the phase with the value.

FIG. 6 is a view showing a joint shape by YAG laser lap joint welding.

FIG. 7 is a diagram showing a configuration of a laser processing apparatus according to a conventional technique.

[Description of Signs] 1 YAG laser oscillator 2 Laser beam 3 Half mirror 4 Output window 5 Optical fiber 6 Laser processing head 7 Collimator 8 Condensing optical system 9 Workpiece material 10 Processing point 11 Fused portion 12 Bandpass filter 13 Light receiving portion 14 Light intensity calculator 15 Oscillation controller

Claims (3)

[Claims] 1. A method for measuring the intensity of YAG laser light reflected from a processing point during welding in a YAG laser welding, detecting a focus position shift of the processing point from the reflected light intensity, and correcting the focal position online. And a processing method. 2. In YAG laser welding, the intensity of YAG laser light reflected from a processing point during welding is measured while oscillating a converging optical system in a direction perpendicular to a material to be welded, and the time of the reflected light intensity is measured. A laser processing apparatus and a processing method, wherein a direction of a focus position shift of a processing point is detected from a phase of a differential value and a phase of a condensing optical system position, and the focus position is corrected online. 3. In YAG laser welding, the intensity of YAG laser light reflected from a processing point during welding is measured while oscillating the condensing optical system in the direction perpendicular to the workpiece to be welded with its amplitude below the depth of focus. A laser processing apparatus and a processing method, wherein a direction of a focus position shift of a processing point is detected from a phase of a time differential value of the reflected light intensity and a phase of a condensing optical system position, and the focal position is corrected online. .