JP2017173371A - Optical fiber-based laser light transmission device for laser beam machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber-based laser light transmission device for a laser beam machine using a laser light source with a high energy density and a high light-condensing performance, which is able to suppress the spattering from a workpiece by means of a top hat-distributed laser beam and at the same time prevent the fluctuation in the power density for stable machining, without incurring complication and increased costs.SOLUTION: An optical fiber for guiding a laser beam from the laser light source to a machining torch is divided into a first optical fiber on the laser light source side and a second optical fiber on the machining torch side. When laser light emitted from the first optical fiber is recondensed by a recondensing optical system and made to enter the second optical fiber, the optical axis of the entering portion of the second optical fiber is tilted relative to the optical axis on the recondensation side to transform the laser light to top hat-distributed light within the second optical fiber.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laser beam transmission apparatus using an optical fiber for transmitting laser beam from a laser light source toward a machining torch in a laser beam machine such as a laser welding machine.

In a laser processing machine that performs processing such as welding, cutting, drilling, and grooving using laser light as processing energy, an optical transmission device using an optical fiber as a laser light transmission means from a laser light source to a workpiece Is widely used (for example, Patent Document 1).
On the other hand, as a laser light source for a laser processing machine, particularly a laser welding machine, in recent years, a light source having a high energy density and a high light condensing property, such as a fiber laser and a disk laser, has been frequently used. If such a high energy density and highly condensing laser beam is condensed with a lens or the like, it has a sharp peak, called a normal distribution or a Gaussian distribution, where the power density in the center is extremely high locally. A focused beam is obtained. For this reason, if a conventional general laser beam transmission device using an optical fiber transmits a laser beam with high energy density and high condensing property from a laser light source and irradiates the workpiece for welding or the like The power density at the center of the irradiation area (focal position) is too high, and a large amount of scattered matter called spatter is generated around the processing point, resulting in a problem of significantly degrading the cleanliness of the processed product.
Such a conventional problem will be described more specifically with reference to FIGS.

  FIG. 9 schematically shows a configuration of a conventional general laser processing apparatus using an optical fiber as a transmission apparatus, and FIGS. 10 and 11 show central axes (optical axes) at respective parts in the optical system. On the other hand, the shape of the power density distribution (horizontal axis: position, vertical axis: indicated by power density) of the laser beam in a plane orthogonal to each other is shown.

  In FIG. 9, a laser beam output from a laser light source, for example, a laser oscillator 1 such as a fiber laser, is guided by an optical fiber 2, and is condensed on the surface of a workpiece 5 by a lens system in a processing torch 3. Point 4 is irradiated. Here, the power density distribution of the laser light 31 in the optical fiber 2 is mainly a normal distribution (Gaussian distribution) as shown in FIG. If this laser beam is condensed by the processing torch 3, the condensing point 4 of the condensed laser beam 32 also has a normal distribution as shown in FIG. The focused beam 32 having such a normal distribution has an extremely high power density with a sharp peak at the center thereof, and the center of the focused spot of the workpiece rapidly increases in temperature. When heated, the surface of the workpiece is abruptly vaporized or ionized, and as a result, the molten metal is scattered to generate scattered materials called so-called sputtering. As a result, there is a problem that the scattered molten metal adheres and solidifies around the processing point on the surface of the workpiece, and as a result, the surface cleanliness of the workpiece is significantly deteriorated. Moreover, the problem of causing a shape error may be caused by the deposits by sputtering.

  As a method of coping with the above problems, spatter is generated by deliberately shifting the focal position of the laser beam with respect to the surface of the workpiece and reducing the power density at the surface position of the workpiece. Conventionally, laser processing is performed while suppressing.

  However, in a normally distributed laser beam from a high energy density laser light source such as a fiber laser, as shown in FIG. 12, the amount of change in the power density of the irradiated laser beam with respect to the focal length change is large near the focal point. Therefore, in an actual apparatus, it is practically difficult to maintain the shift amount of the focal position so that the power density at the surface position of the workpiece is always kept constant. Therefore, when applying the method of shifting the focal position, it is actually difficult to stabilize the power density on the surface of the workpiece, and thus it is difficult to stably perform processing such as welding. .

  Therefore, in order to suppress spatter generation and perform stable processing when performing laser processing such as welding using a laser light source with high power density and high condensing property, such as a fiber laser, laser collection is necessary. It is considered that the power density distribution shape at the light spot is preferably a distribution shape called a top hat distribution, which is different from the conventional normal distribution (Gaussian distribution). The top hat distribution is also called a square distribution, and as shown by a solid line T in FIG. 13, is a distribution having a shape in which the top of a normal distribution indicated by a broken line N is crushed and the top is flattened. Also referred to as the normal distribution (N) of laser beams of the same energy amount, the power density at the center is low, spattering is less likely to occur, and the power density on the workpiece surface due to focal position deviation It is thought that there is little fluctuation.

  It has already been proposed in Patent Documents 2 to 6 and the like to perform laser processing such as welding by irradiating a workpiece with a laser beam having a top hat distribution in this way. However, in these proposals, a special optical system is required to obtain the top hat distribution, or a special medium must be used, which is inevitably expensive. In addition, with these conventional techniques, it is difficult or impossible to adjust the machine once it has been assembled. The optimal top according to the material, processing range, processing amount, etc. of the workpiece. There was also a problem that it was not always easy to obtain a hat distribution.

JP 2008-254006 A JP2015-155110A JP 2011-176116 A JP 2011-161383 A JP 2014-125660 A JP2015-188901A

  The present invention has been made in view of the above problems, and is used in a laser processing machine using a laser light source that generates a laser beam with high energy density and high condensing performance, such as a fiber laser or a disk laser. As a laser beam transmission device using an optical fiber, the distribution mode of the beam of the laser beam guided to the processing torch is a top hat distribution without incurring complexity and high cost of the optical system. An object of the present invention is to provide a laser beam transmission apparatus that can practically perform welding and the like while suppressing the occurrence of spatter of a workpiece and suppressing fluctuations in power density. .

  In order to solve the above-described problems, the present inventors have conducted various experiments and examinations. As a result, an optical fiber for guiding laser light from the laser light source to the processing torch is used as the first optical fiber on the laser light source side. And the second optical fiber on the processing torch side, the second light is obtained by re-condensing the laser light emitted from the first optical fiber by a re-condensing optical system composed of a lens group or the like. When entering the fiber, the laser beam from the laser light source is distributed in a normal distribution (Gaussian distribution) by tilting the optical axis of the incident portion of the second optical fiber with respect to the optical axis on the re-condensing side. However, it can be easily and easily converted to a top hat distribution without using a special optical system or a special medium. Easy to adjust Found bets, the present invention has been accomplished.

Specifically, a laser beam transmission device for a laser beam machine using the optical fiber of the basic mode (first mode) of the present invention is:
In a laser beam transmission device for a laser beam machine using an optical fiber for transmitting a laser beam from a laser light source to a machining torch,
A first optical fiber for guiding laser light from a laser light source;
A refocusing optical system for refocusing the laser light emitted from the first optical fiber to form a refocused laser beam;
A second optical fiber for receiving the refocused laser beam and transmitting the laser light toward the processing torch;
An adjustment mechanism having an angle adjustment function for adjusting the angle of the optical axis of the incident portion in the second optical fiber relative to the optical axis of the refocused laser beam;
By providing an angle relative to the optical axis of the refocused laser beam to the optical axis of the incident portion of the second optical fiber by the adjusting mechanism, the optical axis in the second optical fiber is The power density distribution in the orthogonal plane is converted into a top hat distribution, and the laser light having the top hat distribution is guided from the second optical fiber to the processing torch. is there.

  According to a second aspect of the present invention, there is provided a laser beam transmission apparatus for a laser beam machine using an optical fiber according to the first aspect, wherein the adjustment mechanism has an incident angle in the second optical fiber in addition to the angle adjustment function. It has a position adjustment function for adjusting the center position of the core of the surface relative to the center axis position of the refocus laser beam.

  Furthermore, in the laser beam transmission apparatus for a laser beam machine using the optical fiber according to the third aspect of the present invention, in the first or second aspect, the core diameter of the second optical fiber is the first light. It is larger than the core diameter of the fiber.

  The laser beam transmission apparatus for a laser beam machine using the optical fiber according to the fourth aspect of the present invention is the first or second aspect, wherein the maximum incident angle of the second fiber is the first incident angle. It is characterized by being larger than the maximum incident angle of the optical fiber.

  According to the present invention, as a laser beam transmission device used in a laser processing machine using a laser light source that generates a laser beam having a high energy density and a high light collecting property, such as a highly condensing fiber laser or a disk laser, The distribution mode of the laser beam guided to the processing torch can be easily and easily converted to the top hat distribution without incurring the complexity and high cost of the optical system. By processing with a laser beam with a top hat distribution, it is possible to suppress the occurrence of spattering of the work material, and it is practically possible to stably perform processing such as welding while suppressing fluctuations in power density. In addition, the shape of the top hat distribution can be easily adjusted, so laser processing with a more optimal top hat distribution is always performed to obtain high processing efficiency. Can become effects are achieved.

1 is a schematic diagram showing an outline of an example of a laser processing machine incorporating a laser beam transmission apparatus of the present invention. It is a perspective view which shows an example of the adjustment mechanism used for the laser beam transmission apparatus of this invention. It is a schematic diagram for demonstrating the condition at the time of a re-condensing laser beam injecting into the 2nd optical fiber from the re-condensing laser beam from the re-condensing optical system in the laser beam transmission apparatus of this invention. It is a diagram which shows an example of the power density distribution of the re-condensing laser beam from the optical system for re-condensing in the laser beam transmission apparatus of this invention. It is a diagram which shows an example of the power density distribution in the focus position of the laser beam at the time of irradiating a to-be-processed object from the processing torch in the laser beam transmission apparatus of this invention. It is a schematic diagram for demonstrating an example of the condition of the re-condensing laser beam which injects into the 2nd optical fiber through the optical system for re-condensing from the 1st optical fiber in the laser beam transmission apparatus of this invention. It is a schematic diagram for demonstrating another example of the condition of the re-condensing laser beam which injects into the 2nd optical fiber via the optical system for re-condensing from the 1st optical fiber in the laser beam transmission apparatus of this invention. is there. It is a diagram for explaining the definition of a top hat distribution as a power density distribution of a laser beam. It is a schematic diagram which shows the outline | summary of an example of the conventional laser beam machine. It is a diagram which shows an example of the power density distribution of the laser beam from the laser beam source in the conventional laser beam machine. It is a diagram which shows an example of the power density distribution in the focus position of the laser beam from the torch for a process in the conventional laser beam machine. It is a diagram which shows an example of the situation of the change of the power density distribution in the workpiece surface when the focus position of the laser beam from the processing torch in the conventional laser beam machine is shifted with respect to the workpiece material surface. . It is a diagram for explaining a hat top distribution in comparison with a normal distribution (Gaussian distribution) about a power density distribution of a laser beam.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 schematically shows an example of a laser processing machine, for example, a laser welding machine, to which a laser beam transmission apparatus according to the present invention is applied.
In FIG. 1, a plurality of laser beams output from a laser light source, for example, a laser oscillator 1 such as a fiber laser, for example, a laser beam having a normal distribution type (Gaussian distribution type) power density distribution are transmitted by a first optical fiber 21. Is led to a re-condensing optical system 6 composed of a lens group, and the like, and led to a processing torch 3 such as a welding torch or a cutting torch via the second optical fiber 22 from the re-condensing optical system 6. . That is, the laser beam emitted from the exit side end face of the core of the first optical fiber 21 is re-condensed by the re-condensing optical system 6 and re-condensed laser beam (re-condensing laser beam) 33. Enters the core from the end face of the incident portion of the second optical fiber 22 and is guided to the processing torch 3 by the second optical fiber 22.

Here, the incident portion (incident side end portion) 22 </ b> A of the second optical fiber 22 is held by the adjusting mechanism 7. The adjusting mechanism 7 has a function of adjusting the angle of the optical axis of the incident surface of the second optical fiber 22 relative to the optical axis of the laser light re-condensed by the re-condensing optical system 6. In addition, in this embodiment, in addition to the angle adjustment function described above, the core center position of the incident surface in the second optical fiber 2 is changed from the re-condensing optical system. It has a function (position adjustment function) of adjusting relative to the center axis position of the refocused laser beam.
In the present invention, the entire portion including the first optical fiber 21, the re-condensing optical system 6, the adjustment mechanism 7, and the second optical fiber 22 is replaced with the laser light from the laser light source. It is referred to as a laser beam transmission device 8 for transmission to the processing torch.

An example of a specific configuration of the adjusting mechanism 7 is shown in FIG.
In FIG. 2, an XYZ stage 71 that can be moved and adjusted in the X-axis direction, the Y-axis direction, and the Z-axis direction is disposed on a fixed base (not shown). On the XYZ stage 71, a fixed plate 72 is fixed so as to be along a plane substantially orthogonal to the optical axis of the re-focusing optical system 6 (the central axis of the re-focusing laser beam), and the turning plate 73 Are provided so as to be tilted substantially parallel to the fixed plate 72. The fixed plate 72 and the turn plate 73 are connected by a fixed pin 74 at a position (fixed position) close to the XYZ stage 71. Further, at a position away from the fixed position in two different directions along the surface of each plate (desirably two directions perpendicular to each other, for example, the X direction and the Z direction), there is a gap between the fixed plate 72 and the turn plate 73. Two angle turning screws 75 and 76 capable of adjusting the distance are provided. At least the incident side end (the end on the re-condensing optical system 6 side) 22 a of the second optical fiber 22 is held by a fiber holder 77, and the tip of the fiber holder 77 is fixed to the fixed plate 72. The rear side field portion of the fiber holder 77 (the portion on the side away from the re-condensing optical system 6) is inserted into the opening so as to be tiltable. Although not shown in FIG. 2, the re-condensing optical system 6 is fixed on the fixed base (not shown), or always maintains a fixed positional relationship with respect to the fixed base. Has been.

  In such an adjustment mechanism 7, the turning plate 73 can be tilted (turned) with the fixing pin 74 as a reference by adjusting the angle turning screws 75 and 76 independently. That is, the angle of the tilt plate 73 with respect to the optical axis of the refocusing optical system 6 (the central axis of the refocused laser beam) can be adjusted. Thereby, the angle of the fiber holder 77 with respect to the optical axis of the optical system 6 for re-condensing, and consequently the angle of the optical axis of the incident portion of the second optical fiber 22 whose end 22a is held by the fiber holder 77, It is possible to adjust (adjust the tilt angle) with respect to the optical axis of the refocused laser beam.

  Further, by moving the XYZ stage 71 in one or more of the X-axis direction, the Y-axis direction, and the Z-axis direction with respect to a fixed base (not shown), the second position with respect to the focused position of the refocused laser beam. The center position of the incident surface of the optical fiber 22 can be adjusted so that the center position matches the light collection position.

  Here, referring to FIG. 3, the angle of the optical axis (core axis of the core) of the incident portion of the second optical fiber 22 by the angle adjustment function of the adjustment mechanism 7 in the laser light transmission device 8 in the present embodiment. Will be described by adjusting the angle so that is tilted with respect to the optical axis Or of the refocusing optical system 6.

  In a general laser light transmission apparatus, when a condensed laser light (condensed beam) is incident on an optical fiber, the optical axis of the optical fiber is matched with the optical axis of the condensed beam, and the optical fiber is collected. Usually, the end face (incident surface) of the optical fiber is aligned with the optical position (focal point or imaging position), that is, no misalignment is caused. On the other hand, in the case of the present invention, the angle of the optical axis of the incident portion of the second optical fiber 22 is intentionally tilted with respect to the optical axis of the refocusing optical system 6, that is, the central axis of the refocused beam. Adjustments are made each time (angle adjustment is performed) (the position adjustment function will be described later).

  FIG. 3 shows a situation in which the refocused laser beam 33 is incident on the core 22A of the second optical fiber 22 made of a general single mode fiber made up of the core 22A and the clad 22B surrounding the core 22A. In FIG. 3, with respect to the optical axis of the refocused laser beam, the optical axis in the state where it coincides with the optical axis Oc of the incident portion of the second optical fiber 22 is indicated by the symbol Or ′, and the second light The optical axis in the state inclined with respect to the optical axis Oc of the incident part of the fiber 22 is shown by the symbol Or.

  The dotted line in FIG. 3 indicates the situation where the refocused laser beam is incident on the second optical fiber 22 without misalignment as described above, that is, the optical axis Or ′ of the refocused laser beam and the second optical fiber 22. This shows a state (alignment state) in which the optical axis Oc of the incident portion coincides. In this case, the laser beam incident into the core 22A of the second optical fiber 22 travels through the core A of the second optical fiber 22 while repeating total reflection at the boundary surface between the core 22A and the cladding 22B. At this time, the laser beam travels in the core while being reflected on the axis object with the central axis of the second optical fiber 22 as a reference.

  On the other hand, the solid line in FIG. 3 shows a situation where the optical axis Oc of the incident portion of the second optical fiber 22 is tilted by an angle α with respect to the optical axis Or of the refocused laser beam (angle shifted state). This situation can also be said to be a situation in which the refocused laser beam is bent and incident on the optical fiber 22. In such an angle-shifted state, unlike the alignment state, the laser beam incident on the core A of the second optical fiber 22 repeats asymmetric reflection with respect to the central axis of the second optical fiber 22. . Therefore, the number of reflections at the interface between the core 22A and the clad 22B varies greatly depending on the incident position into the core, and as a result, light at different incident positions gradually mixes in the core. As a result, the characteristic distribution state of the power density of the refocused laser beam 33 at the time of incidence (in this case, a normal distribution with a high center and a low periphery) changes (disintegrates), and the core is repeatedly reflected repeatedly. The power density is averaged within. Due to the averaging of the power density in the core, the laser beam 34 emitted from the end of the second optical fiber 22 has a top hat distribution as shown in FIG. 4, for example. According to such an averaging mechanism, the longer the length of the second optical fiber, the more the averaging proceeds, and the top hat distribution can be obtained more reliably.

  As described above, for example, a top hat-shaped laser beam 34 as shown in FIG. 4 is output from the second optical fiber 22. If such a top-hat shaped laser beam 34 is guided to the processing torch 3, a top-hat shaped condensed beam 35 as shown in FIG. This top-hat-shaped focused beam has a region where the power density is high spreading flat around the position of the optical axis, and there is no portion where the power density is extremely high (a point where a sharp peak occurs) at the center. Therefore, it is possible to suppress the occurrence of spatter in laser processing such as welding. At the same time, even if the focal position is shifted with respect to the surface position of the workpiece, there is little fluctuation in the power density on the surface of the workpiece, and therefore laser processing such as stable welding can be realized.

  Here, the core diameter of the second optical fiber 22 is the same as the core diameter of the first optical fiber 21, and the maximum incident angle θmax is the same between the first optical fiber 21 and the second optical fiber 22. If there is a portion of the refocused laser beam incident on the second optical fiber 22 in a bent state, a small portion of the refocused laser beam that cannot enter the core of the second optical fiber 22 is generated. There is a concern that the light energy is consumed as heat in the second optical fiber 22, resulting in an inefficient optical system.

  As a first method for preventing the above-described heat generation and preventing the decrease in efficiency while actively promoting the top hat distribution of the laser beam, for example, as shown in FIG. It is effective to make the maximum incident angle θmax2 of the core of the optical fiber 22 larger than the maximum incident angle θmax1 of the core of the first optical fiber 21. The maximum incident angle θmax can be expressed by the numerical aperture NA of the optical fiber, and NA = sin (θmax).

The reason why it is effective to make the maximum incident angle θmax2 of the second optical fiber 22 larger than the maximum incident angle θmax1 of the first optical fiber 21 as described above is as follows.
That is, even if the second optical fiber 22 is bent with respect to the central axis of the refocused beam (and hence the optical axis of the first optical fiber 21), the bending angle (incident shift angle) α is equal to the first light. If the difference between the angles of θmax1 of the fiber 21 and θmax2 of the second optical fiber 22 is smaller, the refocused beam on the second optical fiber 22 is within the range of the maximum incident angle θmax2 of the second optical fiber 22. This is because all the laser light of the re-condensing beam can be incident on the core of the second optical fiber 22 and there is no portion that cannot completely enter the core.

  In addition, as shown in FIG. 7, the second method for preventing the above-described heat generation and preventing the decrease in efficiency while actively promoting the top hat distribution of the laser beam is as follows. It is effective to make the core diameter d2 of the optical fiber 22 larger than the core diameter d1 of the first optical fiber 21. The reason is as follows.

In general, in an optical system, a laser beam follows the following formula.
That is, if the condensing diameter is d and the angle of divergence is θ,
Therefore, if the core diameter d2 of the second optical fiber 22 is a times the core diameter d1 of the first optical fiber 21 (a is a number of 1 or more), the light is condensed. The angle of beam divergence (condensation) is 1 / a times. As an example, FIG. 7 shows a situation in which an enlarged image is formed on the second fiber 22 having a core diameter d2 (= a × d1) which is a times the core diameter d1 of the first optical fiber 21. . In this example, the maximum incident angle θmax2 of the second fiber 22 is the same as the maximum incident angle θmax1 of the first optical fiber 21.
In this case, the converging angle (divergence angle) θmax1 / a of the incident beam (recondensing beam) to the second optical fiber 22 is the maximum incident angle θmax2 (= θmax1) of the second optical fiber 22.
Even if the second optical fiber is bent within a range that is smaller and does not exceed this difference, the refocused laser beam does not protrude from the core of the second optical fiber 22.

  Note that, in the above, the first method in which the maximum incident angle θmax2 of the core of the second optical fiber 22 is larger than the maximum incident angle θmax1 of the core of the first optical fiber 21, and the second method Although the second method of making the core diameter of the optical fiber 22 larger than the core diameter of the first optical fiber 21 has been individually described, it goes without saying that these methods may be combined. That is, the maximum incident angle θmax2 of the core of the second optical fiber 22 is set larger than the maximum incident angle θmax1 of the core of the first optical fiber 21, and at the same time, the core diameter of the second optical fiber 22 is set to the first diameter. It may be larger than the core diameter of the optical fiber 21.

In the above-described embodiment, the adjustment mechanism 7 has not only the angle adjustment function but also the position adjustment function. The reason is as follows.
That is, in the embodiment, the optical axis of the incident portion of the second optical fiber 22 is collected again by tilting (turning) the turning plate 73 with reference to the fixing pin 74 by adjusting the angle turning screws 75 and 76. In this case, the center position of the incident surface of the second optical fiber 22 is re-collected from the re-condensing optical system 6. The focal position of the light beam may be shifted. Therefore, during or after the angle adjustment, the XYZ stage 71 is set so that the center position of the incident surface of the second optical fiber 22 coincides with the focal position of the re-condensing beam from the re-condensing optical system 6. The above-mentioned alignment can be performed by moving and adjusting a fixed base (not shown) in one or more of the X-axis direction, the Y-axis direction, and the Z-axis direction.

  As described above, the incident shift angle α of the second optical fiber 22 necessary for finally obtaining a laser beam having a top hat distribution varies greatly depending on the length of the second optical fiber 22, and refocusing is performed. Since it varies depending on the condensing characteristic (condensing angle) in the optical system 6 for use, the material of the second optical fiber 22 (core refractive index), the core diameter, etc., it cannot be generally defined, but will be described later. As shown in the first and second embodiments, for example, when the fiber length of the second optical fiber 22 is 10 m, the laser beam power density that can be evaluated as the top hat distribution at about 0.1 ° or 0.3 ° or more. Distribution can be obtained.

  If the incident shift angle α of the second optical fiber 22 is made larger than about 0.1 ° or 0.3 °, a better top hat distribution can be obtained. Even if it exceeds about 0 °, the top hat shape does not change beyond that. Furthermore, if the incident shift angle α is excessively increased, a portion where the refocused beam cannot enter the core of the second optical fiber 22 even if the first method or the second method is applied. In general, the incident shift angle α is desirably about 1.0 ° or less at maximum because it causes heat generation and a decrease in efficiency.

Whether the top hat distribution is obtained or not is determined by examining the power density distribution in the plane perpendicular to the optical axis of the laser beam 34 on the exit side of the second optical fiber 22 as follows. Can be evaluated.
That is, as shown in FIG. 8, the beam diameter in a line having a high power density corresponding to 17% of the maximum power density of the laser beam 34 on the exit side of the second optical fiber 22 is defined as the focused beam diameter. The diameter of the central horizontal part is defined as the flat part beam diameter. Then, the ratio of the flat portion beam diameter to the above-mentioned condensing beam diameter (flat portion beam diameter / condensing beam diameter) is defined as a top hat ratio, and the shape of the top hat distribution can be evaluated by the value of the ratio. it can.

In the embodiment of the present invention, when the ratio is 0.5 or more, it is determined that the top hat distribution is obtained. That is,
Top hat ratio = flat part beam diameter / condensed beam diameter ≧ 0.5
When it becomes, it determines with top hat distribution.
Here, if the top hat ratio in the laser beam 34 on the exit side of the second optical fiber 22 is 0.5 or more, the workpiece is irradiated with the condensed beam condensed by the machining torch. Experiments have confirmed that the effect of suppressing spatter can be obtained.

  In the above description, whether or not the top hat distribution is obtained is evaluated by the top hat ratio of the laser beam 34 on the exit side of the second optical fiber 22, but the lens in the processing torch 3 or the like. Is generally extremely small, the top hat ratio at the focal point (image point) of the laser beam 35 collected by the processing torch 3 is also the top of the laser beam 34 on the exit side of the second optical fiber 22. Usually, it is substantially the same as the hat rate. Therefore, depending on the case, it is allowed to evaluate the top hat ratio based on the power density distribution at the focal point (image point) of the laser beam 35 collected by the processing torch 3.

  In the above-described embodiment, the refocusing optical system 6 is fixed and the angle and position of the incident portion of the second optical fiber 22 are adjusted by the adjustment mechanism 7. The relationship between the optical system 6 for use and the second optical fiber 22 is relative. Therefore, the incident portion of the second optical fiber 22 is fixed, and the angle and position of the optical system 6 for re-condensing are fixed. Of course, it may be adjusted.

  In order to verify the operation and effect of the present invention, experiments as shown in the following examples were conducted.

[Example 1]
In the first embodiment, as shown in FIG. 6, the maximum incident angle θmax2 of the second optical fiber 22 is made larger than the maximum incident angle θmax1 of the first optical fiber 21 as shown in FIG. This is an example of applying a method of enlarging.
Specifically, a fiber laser having an output of 1 kW is used as a laser light source, and a general quartz-based single mode fiber is used as the first and second optical fibers 21 and 22, and laser processing as shown in FIG. A welding test was performed on a steel plate having a thickness of 3 mm by irradiating the surface of the steel plate with a laser beam with a focused diameter of 0.4 mm by a machine (in this example, a laser welding machine).
The first optical fiber 21 has a core diameter of 400 μm, NA = 0.20 (θmax1 = 11 °), and the second optical fiber 22 has a core diameter of 400 μm, NA = 0.26 (θmax2 = 14 °), second The length of the optical fiber 22 was 10 m. Further, as the re-condensing optical system 6, an equal magnification imaging system was used, and the condensing angle to the second optical fiber 22 was about 8 °.

  The angle of the optical axis Oc of the incident portion of the second optical fiber 22 with respect to the optical axis Or of the refocusing optical system 6 (incident shift angle α) is adjusted in various ways, and for each incident shift angle, At the position where the largest power is generated (loss is reduced) so that the center position of the incident surface of the second optical fiber 22 matches the focal position of the re-condensing beam from the re-condensing optical system 6 as much as possible. The position was adjusted to be fixed. Then, for each incident shift angle, the power density distribution state of the refocused beam was examined to obtain the top hat ratio and the occurrence of spatter was examined.

  As a result, by setting the incident shift angle to 0.1 ° or more, the top hat ratio becomes 0.5 or more, that is, the laser beam from the processing torch has a top hat distribution, thereby reducing the occurrence of spatter. Turned out to be possible. In particular, when the incident shift angle was set to 1.5 °, it was confirmed that a very good top hat distribution (top hat ratio of 0.75) was obtained and the occurrence of spatter could be sufficiently suppressed. The above effect does not change even if the incident shift angle exceeds 1.5 °. However, if the incident shift angle exceeds 3 °, the refocused beam does not completely enter the core of the second optical fiber 22 and the efficiency is improved. It was confirmed that it decreased.

  In the above, it is considered that the reason why the effect was not recognized when the incident shift angle was less than 0.1 ° was that the number of reflections was not sufficiently increased in the second optical fiber having a length of 10 m. Also, under the condition that the incident shift angle exceeds 1.5 °, it is considered that the top hat has already been completely completed, and no further improvement is made.

[Example 2]
The second embodiment is an example in which the second technique described above, that is, a technique in which the core diameter of the second optical fiber 22 is made larger than the core diameter of the first optical fiber 21 is applied.
Specifically, as in the first embodiment, a fiber laser having an output of 1 kW is used as the laser light source, and general quartz-based single mode fibers are used as the first and second optical fibers 21 and 22, respectively. 1 was irradiated with a laser beam with a condensing diameter of 0.4 mm on the surface of the steel sheet, and a 3 mm thick welding test was performed.

  The first optical fiber 21 has a core diameter of 200 μm, NA = 0.20 (θmax1 = 11 °), and the second optical fiber 22 has a core diameter of 400 μm, NA = 0.20 (θmax2 = 11 °), and the fiber length. 10 m. When a double imaging system was used as the re-condensing optical system 6 (a = 2 in FIG. 7), the condensing angle to the second optical fiber 22 was about 5.5 degrees. Then, for each incident shift angle, the power density distribution of the refocused beam was examined to obtain the above-mentioned top hat ratio and the occurrence of sputtering.

  As a result, by setting the incident shift angle to 0.3 ° or more, the value of the top hat ratio becomes 0.5 or more, that is, the laser beam from the processing torch is converted into the top hat distribution, and the sputtering is performed. It has been found that the occurrence can be reduced. In particular, when the incident shift angle was set to 2.0 °, it was confirmed that a very good top hat distribution can be obtained (top hat ratio 0.75), and the occurrence of spatter can be sufficiently suppressed. . The above effect does not change even if the incident shift angle exceeds 2.0 °. However, if the incident shift angle exceeds 5.5 °, the refocused beam does not completely enter the core of the second optical fiber 22, It was confirmed that the efficiency decreased.

  In the above, the reason why the effect was not recognized when the incident shift angle was less than 0.3 ° was considered that the number of reflections was not sufficiently increased in the second optical fiber having a length of 10 m. Further, it is considered that under the condition that the incident shift angle exceeds 2.0 °, the top hat has already been completely completed, and no further improvement is made.

  The preferred embodiments and examples of the present invention have been described above. However, these embodiments and examples are merely examples within the scope of the present invention and do not depart from the spirit of the present invention. Thus, addition, omission, replacement, and other changes of the configuration are possible. That is, the present invention is not limited by the above description, is limited only by the scope of the appended claims, and can be appropriately changed within the scope.

1 Laser oscillator (laser light source)
3 Processing Torch 5 Workpiece 6 Re-Condensing Optical System 7 Adjustment Mechanism 21 First Optical Fiber 22 Second Optical Fiber

Claims (4)

In a laser beam transmission device for a laser beam machine using an optical fiber for transmitting a laser beam from a laser light source to a machining torch,
A first optical fiber for guiding laser light from a laser light source;
A refocusing optical system for refocusing the laser light emitted from the first optical fiber to form a refocused laser beam;
A second optical fiber for receiving the refocused laser beam and transmitting the laser light toward the processing torch;
An adjustment mechanism having an angle adjustment function for adjusting the angle of the optical axis of the incident portion in the second optical fiber relative to the optical axis of the refocused laser beam;
By providing an angle relative to the optical axis of the refocused laser beam to the optical axis of the incident portion of the second optical fiber by the adjusting mechanism, the optical axis in the second optical fiber is An optical fiber characterized in that a power density distribution in a plane orthogonal to each other is converted into a top hat distribution, and the laser light having the top hat distribution is guided from a second optical fiber to the processing torch. Laser beam transmission device for laser processing machine using In the laser beam transmission device for a laser beam machine using the optical fiber according to claim 1,
In addition to the angle adjustment function, the adjustment mechanism includes a position adjustment function for adjusting the center position of the core of the incident surface of the second optical fiber relative to the center axis position of the refocused laser beam. A laser beam transmission device for a laser beam machine using an optical fiber. In the laser beam transmission apparatus for a laser beam machine using the optical fiber according to any one of claims 1 and 2,
A laser beam transmission apparatus for a laser beam machine using an optical fiber, wherein the core diameter of the second optical fiber is larger than the core diameter of the first optical fiber. In the laser beam transmission apparatus for a laser beam machine using the optical fiber according to any one of claims 1 and 2,
A laser beam transmission apparatus for a laser beam machine using an optical fiber, wherein the maximum incident angle of the second fiber is larger than the maximum incident angle of the first optical fiber.

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