JPH09248684A - Laser beam machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a highly reliable oscillating mechanism by oscillating the optical system with an actuator using a piezoelectric element and thereby enabling high frequency oscillation. SOLUTION: In machining by the irradiation of a laser beam 10 on the surface of an object 13 to be worked, the optical system is oscillated with an actuator 20 using a piezoelectric element. Accordingly, the fluctuating direction of the converging position of the laser beam varies depending on the oscillating direction of the optical system; therefore, for example, with the converging position varied in the direction crossing the machining line 14, the converging position traces a zigzag moving locus as the machining head moves along the machining line 14. As a result, in the case of butt welding, a gap or misalignment tolerance is expanded, relaxing machining accuracy required for the abutting end face. In addition, with the piezoelectric element used for the actuator 20, high frequency oscillation is made possible. Further, looseness or wear is less compared with a conventional mechanical mechanism; hence, there is high reliability for durability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention guides a laser beam emitted from a laser oscillator to a condensing optical system by a transmission optical system, condenses the laser beam to a predetermined spot diameter by the condensing optical system, and irradiates the workpiece. The present invention relates to a laser processing device for performing welding, cutting, and other various processing.

[0002]

2. Description of the Related Art Among the processes performed by using laser light, there is a use in which a laser irradiation area is widened to enhance its effect. For example, when butt-welding two or more plates having the same or different plate thickness or chemical composition, melting is performed by reciprocally moving the laser focusing position with a certain amplitude around the joining line (processing line). The increase in the amount not only ensures the bonding, but also has the effect of absorbing a minute positional deviation between the bonding line and the light collecting position. Further, the same method is often effective also in the case of surface treatment for which a large area is desired to be easily processed.

A mechanical mechanism is known in which the condensing position of laser light is reciprocally moved in a direction crossing a processing line (Japanese Patent Laid-Open Nos. 2-142693 and 5-5).
7466, JP 7-9176, etc.).

Japanese Unexamined Patent Publication (Kokai) No. 2-142693 discloses a mechanism for oscillating a laser beam applied to a machining line of a workpiece in a direction intersecting the machining line.
FIG. 3 shows a lens scanning type beam scanning device which is generated by reciprocating a lens for focusing the laser light so that the oscillation of the laser light is reciprocated. In this known device, as shown in FIG. 5, a condenser lens (2) for condensing a laser beam (1) is held on a lens mount (4), and a rod (5) of a lens (4) is attached to the lens mount (4). One end is connected and the other end of the rod (5) is rotatably fitted to an eccentric cam (6) attached to the output shaft of the motor (7). Then, with the rotation of the eccentric cam (6), the lens mount (4) reciprocates in a direction traversing the processing line (8) of the workpiece (3) through the reciprocating motion of the rod (5).

Condensing lens (2) and lens mount (4)
Is housed in a torch (not shown), and the torch moves along the processing line (8).
Therefore, during laser welding, the lens mount (4) holding the condenser lens (2) reciprocates as described above, so that the laser light (1) simply scans linearly along the processing line. Instead of doing it, it will swing zigzag.

[0006]

SUMMARY OF THE INVENTION In the above-mentioned conventional mechanical rocking mechanism, poor responsiveness, generation of sound, generation of vibration and chatter at high frequency, and change of amplitude cannot be performed by using an electric signal. There are problems such as wear over time due to use and a complicated mechanism. For example, wear between the rod (3) and the eccentric cam (5) is unavoidable, and it becomes difficult to perform stable laser light scanning due to backlash. In addition, since the swing amplitude is uniquely determined by the amount of eccentricity of the cam, there is a limit to the swing amplitude that can be obtained when using an eccentric cam with a small displacement.

Therefore, the object of the present invention is to:
To solve the above problems of the conventional mechanical rocking mechanism, and to provide a laser processing apparatus equipped with a rocking mechanism capable of rocking at a high frequency, having less rattling and wear, and having high durability and reliability. is there.

[0008]

In order to achieve the above object, the present invention provides a laser processing apparatus for irradiating a surface of a workpiece with a laser beam for processing, wherein an optical system is formed by an actuator using a piezoelectric element. It is designed to be rocked (Claim 1).

By swinging the optical system, the focus position of the laser light changes. Then, the direction of fluctuation of the focus position of the laser light also changes depending on the direction of oscillation of the optical system. For example, when the condensing position of the laser light is changed in the direction crossing the machining line, the condensing position of the laser light draws a zigzag movement trajectory as the machining head moves along the machining line. As a result, for example, in the case of butt welding, the gap tolerance and the misalignment tolerance are increased, and the machining accuracy required for the butt end face of the workpiece is relaxed. Further, it is also possible to change the focus position of the laser light in parallel with the processing line, that is, in the moving direction of the processing head, which is useful, for example, in stirring the molten metal to increase the penetration.
Furthermore, by swinging the optical system so that the focus position of the laser light draws a circle, it is possible to make the spot position of the laser light draw a spiral movement locus as the machining head runs. is there.

As the actuator, an actuator using a piezoelectric element can be adopted. An example of such an actuator is a piezo actuator. A piezo actuator utilizes a so-called inverse piezoelectric effect, in which when a voltage is applied to a crystal such as piezoelectric ceramics, a displacement is generated according to the voltage,
It has excellent responsiveness and follows at a high speed of 100 μs or less. Moreover, since it has a high resolution of 0.1 μm or less, it can be driven with high accuracy.

Since the displacement of the piezo actuator is not so large as about 50 μm, when the amplitude of about 1 mm is required, it cannot be adopted in the actuator of the prior art described with reference to FIG. By adopting the piezo actuator in combination with the condensing optical system including a mirror, a desired swing amplitude can be obtained on the machined surface even if the actuator itself has a relatively small displacement. That is, when the parabolic mirror is moved around the fulcrum, the displacement on the focal plane becomes large optically. For example, for butt welding of blank materials, it is sufficiently effective to obtain an amplitude of 1 mm or less at the focal point, and the tilt angle of the parabolic mirror required for that is, when the focal length is 10 inches,
It is about 0.11 °.

The fluctuation of the condensing position of the laser light can be achieved by oscillating the condensing optical system of the laser light (claim 2). The condensing optical system may be a reflective parabolic mirror (Claim 3) or a transmissive condensing lens (Claim 4). When the focusing position is swung, the quality of the beam is deteriorated due to the influence of the aberration inherent in the lens except when the optical axis is at the center of the lens. Considering this point, the folding mirror and the condenser lens may be unitized to swing the condenser unit that constitutes the condenser optical system as a whole (Claim 5).

It is also possible to change the focus position of the laser light by swinging an optical system other than the focus optical system. For example, the folding mirror on the side closer to the laser oscillator than the focusing optical system may be swung by the actuator (claim 6). Usually, an electric motor is used to drive the mirror, but the mechanism can be miniaturized by being driven by an actuator using a piezoelectric element. in this case,
Only one folding mirror may be swung (claim 7), or two or more folding mirrors may be swung in synchronization with each other (claim 8). In the latter case, for example, by swinging one folding mirror in the horizontal direction and swinging the other folding mirror in the vertical direction, the focus position of the laser light draws a circle or an ellipse. fluctuate.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a laser processing apparatus according to the present invention will be described below.

FIG. 1 exemplifies an embodiment of the present invention applied to butt welding two blank steel plates (workpieces) whose ends are abutted against each other. The laser processing apparatus has a reflection-type condensing system using a parabolic mirror (11), and transmits a laser beam (10) guided by a transmission optical system including a folding mirror (12) to a parabolic mirror ( The light is focused at 11) and is applied to the surface of the work (13). The processing line (14), in this case the welding line, extends perpendicular to the plane of the drawing in FIG.

The laser beam (10) focused by the parabolic mirror (11) is directed toward the abutting portion of the workpiece (13), that is, the welding line (14). By swinging the parabolic mirror (11) in parallel with the paper surface of FIG. 1 as shown in the figure, the converging position of the laser beam (10) reciprocates in the direction crossing the processing line (14). The swing mechanism in this case is, as an example, a parabolic mirror (11) rotatably supported by a support pin that passes through the fulcrum (O) of the swing motion and is perpendicular to the paper surface of FIG. At (21), the parabolic mirror (11) is biased in one rotation direction, and the driving force of the actuator (20) is exerted in the opposite direction. Note that here, the case where the processing line extends perpendicularly to the paper surface of the figure and therefore the processing head moves vertically to the paper surface of the figure has been described, but the processing line extends parallel to the paper surface of the figure and the processing head is When moving parallel to the paper surface of the figure,
When the parabolic mirror (11) swings as shown by the imaginary line, the focus position of the laser light will change parallel to the processing line. This also applies to those in FIGS. 2 and 3.

As shown in FIG. 2, the parabolic mirror (11) may be swung around the incident optical axis. That is, a paraboloidal mirror (11) is rotatably supported about the incident optical axis, and as shown in FIG. 2C, a spring or the like that biases the parabolic mirror (11) in one rotation direction. The elastic means (21) is provided and the actuator (20) is interposed between the stationary member and the parabolic mirror (11) so that the displacement direction of the actuator (20) coincides with the tangential direction of the parabolic mirror. . As a result, when the actuator (20) is extended by energization, the parabolic mirror (11) rotates in one direction against the elastic force of the elastic pressure means (21), and the actuator (20).
When is reduced, the parabolic mirror (1
1) rotates in the opposite direction. Thus, the displacement of the actuator (20) causes the parabolic mirror (11) to reciprocally rotate about the incident optical axis, and as a result, the focus position of the laser beam (10) reflected by the parabolic mirror (11). Moves reciprocally in the direction crossing the incident optical axis (FIG. 2 (B)).

FIG. 3 illustrates a transmissive condensing system in which the folding mirror (15) and the condensing lens (16) are unitized as shown by the chain double-dashed line. By swinging this condensing unit (17) in parallel with the paper surface of FIG. 2 by the piezo actuator, the condensing position of the laser beam (10) is set in the direction crossing the processing line (14) of the workpiece (13). It will move back and forth.

Further, a swinging mechanism in the case of changing the focus position of the laser light by swinging one or more folding mirrors on the side closer to the laser oscillator than the focusing optical system is illustrated in FIG. It can take such a form.

That is, the folding mirror (12) is attached to a support or a bend block (18) shown by a chain double-dashed line, and the path of the laser beam (10) is reflected by the folding mirror (1).
It will be changed according to 2). The folding mirror (12) is fixed to a mirror holder (12a), and the mirror holder (12a) is a bend block (1).
8) supported by one fulcrum (19) provided between
Moreover, the actuator (20) is in contact with the fulcrum (19) at two positions separated by 90 °. Further, the mirror holder (12a) is adjacent to the fulcrum (19) and the actuator (20), and the bend block (18) is formed by the spring (21).
Being oppressed towards.

By adjusting the displacement of each actuator (20), the angle of the mirror holder (12a) and thus also of the folding mirror (12) can be adjusted arbitrarily and automatically. Actuator (20)
Is embedded in the bend block (18) and does not project to the outside, especially behind the mirror holder (12a), so when mounted in the laser transmission system of various laser devices such as robots, peripheral devices and parts, etc. It has the advantage that it does not interfere with the movement, and the freedom of movement is not restricted.

[0022]

According to the present invention, the high-speed response of the actuator using the piezoelectric element enables high-frequency oscillation, and the displacement, that is, the amplitude of the actuator can be easily changed by an electric signal from the outside. Moreover, since it has less backlash and wear than the conventional mechanical mechanism, it has high durability and reliability, and maintains stability for a long period of time. Therefore, the processing quality can be improved without sacrificing the processing speed too much.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a main part of a laser processing apparatus illustrating an embodiment of the present invention.

2A is a schematic view of a converging optical system showing another embodiment of a laser processing apparatus, FIG. 2B is a sectional view of a workpiece perpendicular to a processing line, and FIG. 2C is a swing mechanism. Is a schematic diagram of.

FIG. 3 is a schematic view of a condensing unit portion showing still another embodiment of the laser processing apparatus.

4A is a cross-sectional view of a folding mirror showing still another embodiment of a laser processing apparatus, and FIG. 4B is a view on arrow B.

FIG. 5 is a schematic diagram showing a conventional technique.

[Explanation of symbols]

 10 Laser Light 11 Parabolic Mirror 12 Folding Mirror 12a Mirror Holder 13 Workpiece 14 Processing Line 15 Folding Mirror 16 Condensing Lens 17 Condensing Unit 20 Actuator

Claims (8)

[Claims] 1. A laser processing apparatus for irradiating a surface of a workpiece with laser light for processing, wherein an optical system is swung by an actuator using a piezoelectric element. 2. The laser processing apparatus according to claim 1, wherein the optical system is a focusing optical system for laser light. 3. The laser processing apparatus according to claim 2, wherein the condensing optical system is a parabolic mirror. 4. The laser processing apparatus according to claim 2, wherein the condensing optical system is a condensing lens. 5. The laser processing apparatus according to claim 2, wherein the condensing optical system is a condensing unit including a folding mirror and a condensing lens. 6. The laser processing apparatus according to claim 1, wherein the optical system is a folding mirror on a side closer to a laser oscillator than a focusing optical system for laser light. 7. The laser processing apparatus according to claim 6, wherein a single folding mirror is swung. 8. The laser processing apparatus according to claim 6, wherein the plurality of folding mirrors are rocked in synchronization with each other.