JP3978066B2 - Laser processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser processing apparatus for welding, cutting, or surface treating a workpiece such as metal or ceramic.
[0002]
[Prior art]
Currently, lasers are widely used for welding, cutting, drilling, surface treatment, and other processing in the processing field of metals, ceramics, and the like. In these processes, a single laser beam is used for processing such as welding and cutting. For this reason, the machining speed is slow, the machining takes a long time, and there is room for improvement in work efficiency. Therefore, many proposals have been made to increase the processing efficiency. For example, the “twin beam processing method” disclosed in Japanese Patent Application Laid-Open No. 9-15288 discloses a deep penetration and welding by inserting a splitting lens into a condensing lens system and dividing the laser beam into two. Simultaneously melting the wire.
[0003]
[Problems to be solved by the invention]
In the twin beam processing method, there are two condensing points, but the two condensing points are condensed at a position equidistant from the condensing optical system in the optical axis direction. Further, since the two laser beams are obtained by dividing one laser beam, each laser beam cannot be controlled independently. Accordingly, it is impossible to irradiate the laser beam with different power densities at different condensing positions on the processed portion. As a result, the laser beam cannot be irradiated at a condensing position and a power density according to the processing conditions, so that there has been a limit to improvement in processing quality and processing efficiency.
[0004]
This invention makes it a subject to provide the laser processing apparatus which can further improve processing quality and processing efficiency by irradiation of the suitable laser beam according to processing conditions.
[0005]
[Means for Solving the Problems]
A laser surface processing apparatus according to the present invention includes a plurality of fiber laser oscillation devices, a laser oscillation control device that controls on / off of the oscillation of the fiber laser oscillation device, and a laser beam emitted from each fiber laser oscillation device. A laser processing apparatus having a single condensing optical system for condensing light, wherein a plurality of laser beams are emitted at positions where the condensing point distances in the optical axis direction from the condensing optical system to the condensing position are different from each other. The light is collected and sequentially turned on and off in the order of short focus distance. Thereby, it can condense to a deep position sequentially from the workpiece surface in steps according to progress of processing.
[0006]
In the laser processing apparatus according to the present invention, the processing material is irradiated with laser light from each optical fiber of the plurality of fiber laser oscillation apparatuses. By controlling an excitation device (for example, a semiconductor laser oscillator), the output of the fiber laser oscillation device is controlled on and off. Moreover, the condensing point distances of the plurality of laser beams are different from each other. Therefore, it is possible to collect light with a required power density that is uniform over a wide range in the processing depth direction or for each depth. As a result, it is possible to appropriately supply the laser beam energy to the processing unit corresponding to various processing conditions.
[0007]
A laser surface processing apparatus according to the present invention includes a plurality of fiber laser oscillation devices, a laser oscillation control device that controls on / off of the oscillation of the fiber laser oscillation device, and a laser beam emitted from each fiber laser oscillation device. focused on a laser processing apparatus and a single converging optical system, said plurality of fiber laser oscillator comprises a first fiber laser oscillator unit and the second fiber laser oscillator device group, wherein The first fiber laser oscillation device group and the second fiber laser oscillation device group are configured such that laser beams are condensed at positions where the condensing point distances in the optical axis direction from the condensing optical system to the condensing position are different from each other. Pulse laser beams from the one-fiber laser oscillator group and the second fiber laser oscillator group are alternately turned on / off.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of the present invention and is a schematic schematic view of the entire laser processing apparatus. The laser processing apparatus 10 is mainly composed of a plurality of fiber laser oscillation apparatuses 12, laser oscillation control apparatuses 18 and processing heads 20 (only three are illustrated for simplicity).
[0009]
The fiber laser oscillation device 12 includes a semiconductor laser oscillator 17 as an excitation device. As the semiconductor laser oscillator 17, for example, a Ga-As semiconductor laser oscillator can be used. When the semiconductor laser oscillator 17 irradiates the active optical fiber (laser oscillation optical fiber) 14 with the excitation laser light (wavelength: about 0.8 μm), the active optical fiber 14 oscillates the laser light (wavelength: about 1.06 μm). . The output of the active optical fiber 14 is, for example, 1 kW, the core diameter is 50 μm, and the clad cross section is a rectangle of 300 × 600 μm. The end of the active optical fiber 14 is a laser beam output end. A passive optical fiber (power transmission optical fiber) may be connected to the output end by fusion, and the laser light may be transmitted to the processing head 20 by the passive optical fiber. In this case, the tip of the passive optical fiber becomes the laser light output end.
[0010]
The laser oscillation control device 18 includes a control computer and a driving power supply unit for the semiconductor laser oscillator 17. The laser oscillation control device 18 controls the injection current of the semiconductor laser oscillator for each fiber laser oscillation device 14. When the injection current exceeds the threshold value, the fiber laser oscillation device oscillates, and when the injection current becomes below, the oscillation is stopped and the laser light output is controlled to be on / off. Depending on the processing conditions, the on / off timing and cycle are set for each optical fiber 14 in advance.
[0011]
The processing head 20 includes a fiber holding unit 22 and a condensing optical system 25. The fiber holding unit 22 holds the tip portions of the plurality of optical fibers 14 at a preset position with the optical axes aligned. The held optical fiber 14 is arranged to form a polygon such as a square or a ring when viewed in a cross section perpendicular to the optical axis of the condensing optical system 25. In the case of a square arrangement, they are arranged in an n × n matrix (where n is the number of optical fibers and 2 or more). Further, the position of the output end 15 is shifted in the optical axis direction with respect to the condensing optical system 25 for each optical fiber or for each optical fiber group. Therefore, as shown in FIG. 2, the output end 15 has a three-dimensional arrangement. The output end of the optical fiber or optical fiber group may be shifted by three or more stages.
[0012]
As shown in FIG. 3, the condensing optical system 25 includes a first condensing lens 26 having a focal length f1 and a second condensing lens 27 having a focal length f2. The distance between the center of the first condenser lens 26 and the center of the second condenser lens 27 is L.
[0013]
As shown in FIG. 3A, the first optical fiber output end 15 n is at a distance of f 1 + Δ with respect to the center of the first condenser lens 26. The laser light Rn emitted from the first optical fiber output end 15n is slightly converged by the first condenser lens 26 and becomes substantially parallel light between the first condenser lens 26 and the second condenser lens 27. The substantially parallel light is condensed by the second condenser lens 27 at the position of the focal point distance f2 ′. As shown in FIG. 3B, the second optical fiber output end 15f is at a focal length f1 with respect to the center of the first condenser lens 26, and the laser light emitted from the second optical fiber output end 15f. Rf becomes parallel light by the first condenser lens 26. The parallel light is condensed at the focal length f2 by the second condenser lens 27.
[0014]
The condensing point distance f2 'of the laser beam Rn can be obtained by the following equation.
f2 '= (f1 ² + Δ · f 1 −Δ · L) f ² / {f 1 ² + Δ · (f 1 + f 2) −Δ · L}
Therefore, the laser beam Rn emitted from the first optical fiber output end 15n is closer to the second condenser lens 27 than the laser beam Rf emitted from the second optical fiber output end 15f as shown in FIG. It is focused on. Note that the output end 15 is not necessarily arranged at the position of the focal length.
[0015]
The laser processing apparatus configured as described above performs processing such as welding, cutting, and surface treatment while feeding the workpiece 1 in the direction of the arrow.
[0016]
Here, the welding test by the said laser processing apparatus is demonstrated. The welding material is a mild steel material having a thickness of 25 mm.
[0017]
The configuration of the condensing optical system 25 is as follows. The focal lengths f1 and f2 of the first condenser lens 26 and the second condenser lens 27 are each 100 mm, and the distance L between both lens centers is also 100 mm. The first optical fiber output end 15n is located at a position 105 mm from the center of the first condenser lens 26, and the second optical fiber output end 15f is located at a position 100 mm. In this case, the laser light Rn from the first optical fiber 14n is condensed at a position of 95 mm from the center of the second condenser lens 27, and the laser light Rf from the second optical fiber 14f is condensed at a position of 100 mm. . That is, the laser beam Rn from the first optical fiber 14n is condensed at a position shifted by 5 mm toward the second condenser lens from the condensing position of the laser beam Rf from the second optical fiber 14f.
[0018]
The arrangement of the optical fibers used in this welding test is as shown in FIG. That is, in any of FIGS. 4A and 4B, nine optical fibers 14f and 14n are arranged in a 3 × 3 matrix. In the arrangement of FIG. 4A, the first optical fibers 14f and the second optical fibers 14n shown in FIG. 3 are alternately arranged in rows and columns. In the arrangement of FIG. 4B, the first optical fibers 14n are arranged along one side of the square, and the others are all the second fibers 14f.
[0019]
The laser output is 8 kW, and the frequency of the pulse laser beam is 5 kHz. The laser light irradiation conditions are as follows.
(1) Output continuous laser light from the first optical fiber 14n and the second optical fiber 14f arranged in FIG.
(2) A pulse laser beam is output from the first optical fiber 14n arranged in FIG. 4A, and a continuous laser beam is output from the second optical fiber 14f.
(3) Pulse laser light is output from the first optical fiber 14n arranged in FIG. 4B, and continuous laser light is output from the second optical fiber 14f following the first optical fiber 14n (see FIG. 6).
(4) A continuous laser beam is output from all optical fibers without deviation in a 3 × 3 matrix arrangement.
FIG. 5 shows the welding results. FIG. 5 reveals that the apparatus of the present invention can obtain a deeper penetration depth than the conventional apparatus, and that the penetration depth varies depending on the laser light irradiation conditions.
[0021]
The deeper penetration in condition (1) than in condition (4) is due to the fact that the focusing position by the fiber laser is misaligned, so the effective depth of focus becomes longer and the range that can be processed by laser light increases. It depends on.
[0022]
The reason why the penetration deeper than that in condition (1) was obtained in condition (2) is that the pulse laser beam has a high power density and a keyhole is easily formed, and the second optical fiber 14f is formed inside the formed keyhole. This is because the continuous laser beam from the laser beam is condensed and the absorption efficiency of the continuous laser beam is increased.
[0023]
Condition (3) is the optical fiber arrangement of FIG. 4B as shown in FIG. 6, and the first optical fiber 14n is arranged on the front side (advance side) of the second optical fiber 14f in the processing direction. Pulse laser light Rn is output from the first optical fiber 14n, and continuous laser light Rf is output from the second optical fiber 14f. Since the pulse laser beam Rn is concentrated on the front side, it is condensed with high power density near the surface of the welding material, and a deep keyhole 6 is formed. The continuous laser beam is condensed at a position where it enters the welding material 5 from the surface of the welding material, that is, inside the keyhole 6. As a result, the laser light absorptance is increased, the processing efficiency is improved, and a deep penetration depth can be obtained.
[0024]
Further, as the laser beam irradiation condition (5) , in the optical fiber arrangement shown in FIG. 4 (a), the optical fibers 14n and 14f are alternately oscillated at a frequency of 1 kHz (on time of the optical fiber is 500 μsec), and the plate thickness is 10 mm. Butt welding was conducted. For comparison, butt welding of mild steel having a thickness of 10 mm was performed under condition (4) . When the number of pore defects in the weld bead per 100 m of weld length was evaluated, the number of pore defects per 100 m of weld length was 1 in condition (5) , whereas 13 holes in condition (4). Defects were observed.
[0025]
The reason why the pore defects per unit length are reduced is as follows. When observing the keyhole opening during welding, the condition (4) shows that the keyhole is periodically blocked, whereas the condition (5) where the condensing point position is vibrated is the keyhole opening. Was stable and no obstruction occurred. For this reason, it is considered that the assist gas that has been trapped inside due to the blockage of the keyhole and becomes a pore defect in the prior art is discharged again to the outside of the steel sheet in the welding of the condition (5) , and the pore defect is reduced.
[0026]
When the laser processing device is, for example, a drilling device, the plurality of fiber laser oscillation devices include a plurality of fiber laser oscillation devices having different focal point distances, and the laser oscillation is performed in ascending order of the focal point distance according to processing conditions. Sequentially turn on and off. Within the optical fiber group, the focal point distance is the same. A deep hole can be made by deepening the condensing position step by step as processing proceeds.
[0027]
【The invention's effect】
In the laser processing apparatus according to the present invention, the laser beam can be focused uniformly over a wide range in the processing depth direction or at a required power density for each processing depth. Energy can be supplied to the processing section. As a result, the processing quality and processing efficiency can be further improved.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention and is a schematic schematic view of an entire laser processing apparatus.
FIG. 2 is a view showing a holding state of a tip portion of an optical fiber in a processing head of the apparatus.
FIG. 3 is a drawing for explaining the relationship between the position of the optical fiber output end and the light collecting position with respect to the light collecting optical system of the apparatus.
FIG. 4 is a view showing an example of arrangement of optical fibers in a processing head.
FIG. 5 is a graph showing the relationship between the welding speed and the penetration depth when the laser beam irradiation conditions change.
FIG. 6 shows an example in which the laser processing apparatus of the present invention is a welding apparatus, and is a schematic view of a processing head.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Work material 5 Welding material 6 Keyhole 10 Laser processing apparatus 12 Fiber laser oscillation apparatus 14 Active optical fiber 15 Optical fiber output end 18 Laser oscillation control apparatus 19 Optical fiber cable 20 Processing head 22 Optical fiber holding part 25 Condensing optical system 26 First condenser lens 27 Second condenser lens 30, 32 Optical fiber group R Laser light

Claims (2)

A plurality of fiber laser oscillator, a laser oscillation control unit for controlling turning on and off the oscillation of the fiber laser oscillator, a single converging optical condensed on the processing unit to the laser light emitted from the fiber laser oscillator A plurality of laser beams are condensed at positions where the condensing point distances in the optical axis direction from the condensing optical system to the condensing position are different from each other, and the condensing point distance is A laser processing apparatus which is sequentially turned on and off in a short order. A plurality of fiber laser oscillator, a laser oscillation control unit for controlling turning on and off the oscillation of the fiber laser oscillator, a single converging optical condensed on the processing unit to the laser light emitted from the fiber laser oscillator A plurality of fiber laser oscillation devices, each of which includes a first fiber laser oscillation device group and a second fiber laser oscillation device group, wherein the first fiber laser oscillation device group and the first fiber laser oscillation device group In the second group of fiber laser oscillators, the laser beams are condensed at positions where the focal point distances in the optical axis direction from the condensing optical system to the condensing position are different from each other. A laser processing apparatus in which pulsed laser beams from a group of fiber laser oscillation apparatuses are alternately turned on and off.

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