Patent Publication Number: US-2022234144-A1

Title: Laser machining method and laser machining device

Description:
TECHNICAL FIELD 
     The present invention relates to a laser machining method and a laser machining device for performing machining on a composite material by irradiating the composite material with a laser. 
     BACKGROUND ART 
     In the related art, a laser machining method for a composite material is known as follows. According to the laser machining method, a first step of irradiating a machining target site of the composite material with a high output power laser beam in a multiple line shape at a high swept speed through a plurality of paths is performed. In response to a progress of the first step, a second step of reducing a multiple line degree is performed when a machining depth gradually increases (for example, refer to PTL 1). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Unexamined Patent Application Publication No. 2016-107574 
     SUMMARY OF INVENTION 
     Technical Problem 
     According to the laser machining method in PTL 1, in the first step, machining is performed in multiple lines disposed around a machining line as a center, and in the second step, machining is performed by reducing the multiple line degree. Therefore, in the laser machining method in PTL 1, a cutting groove has a V-shape formed around the machining line as the center (that is, a tapered shape in which a groove width is narrowed as the machining depth increases). Here, when a machining object is cut by the cutting groove having the V-shape, as the machining object is thicker, a front surface side is more widely removed. Consequently, the path number of machining paths increases, and a removal amount (removal volume) increases. When the path number of machining paths increases, a time required for cutting is lengthened. 
     Therefore, an object of the present invention is to provide a laser machining method and a laser machining device which can reduce a removal amount and improve a machining speed. 
     Solution to Problem 
     According to the present invention, there is provided a laser machining method in which cutting machining for cutting the composite material along a thickness direction is performed by irradiating a composite material with a laser. The laser machining method includes a cutting-out step of irradiating the composite material with the laser from one side in the thickness direction of the composite material to form a first cutout in the composite material, and a cutting step of irradiating the composite material with the laser from the other side in the thickness direction of the composite material to form a second cutout at a position facing the first cutout in the composite material, and cutting the composite material by causing the second cutout to communicate with the first cutout. In the cutting-out step, the first cutout is formed by irradiating the composite material with the laser through a plurality of machining paths aligned in a width direction of the first cutout. In the cutting step, the second cutout is formed by irradiating the composite material with the laser through a plurality of machining paths aligned in a width direction of the second cutout. 
     In addition, according to the present invention, there is provided a laser machining device that performs cutting machining for cutting the composite material along a thickness direction by irradiating a composite material with a laser. The laser machining device includes a laser irradiation unit that irradiates the composite material with the laser, a first laser head that irradiates the composite material with the laser emitted for irradiation from the laser irradiation unit from one side in the thickness direction of the composite material, a second laser head that irradiates the composite material with the laser emitted for irradiation from the laser irradiation unit from the other side in the thickness direction of the composite material, a laser switch that switches the laser emitted for irradiation from the laser irradiation unit between the first laser head and the second laser head, a first laser scanner that scans the composite material with the laser emitted for irradiation from the first laser head, a second laser scanner that scans the composite material with the laser emitted for irradiation from the second laser head, and a control unit that controls the irradiation of the laser. The control unit performs a cutting-out step of forming a first cutout in the composite material by causing the laser switch to switch the laser to the first laser head, and irradiating the composite material with the laser from the first laser head, and a cutting step of cutting the composite material by causing the laser switch to switch the laser to the second laser head, irradiating the composite material with the laser from the second laser head, forming a second cutout at a position facing the first cutout in the composite material, and causing the second cutout to communicate with the first cutout. In the cutting-out step, the first cutout is formed by irradiating the composite material with the laser through a plurality of machining paths aligned in a width direction of the first cutout. In the cutting step, the second cutout is formed by irradiating the composite material with the laser through a plurality of machining paths aligned in a width direction of the second cutout. 
     In addition, according to the present invention, there is provided another laser machining device that performs cutting machining for cutting a composite material along a thickness direction by irradiating a composite material with a laser. The laser machining device includes two laser irradiation units that irradiate the composite material with the laser, a first laser head that irradiates the composite material with the laser emitted for irradiation from one of the laser irradiation units from one side in the thickness direction of the composite material, a second laser head that irradiates the composite material with the laser emitted for irradiation from the other of the laser irradiation units from the other side in the thickness direction of the composite material, a first laser scanner that scans the composite material with the laser emitted for irradiation from the first laser head, a second laser scanner that scans the composite material with the laser emitted for irradiation from the second laser head, and a control unit that controls the irradiation of the laser. The control unit performs a cutting-out step of forming a first cutout in the composite material by causing the first laser head to irradiate the composite material with the laser emitted from one of the laser irradiation units, and a cutting step of cutting the composite material by causing the second laser head to irradiate the composite material with the laser emitted from the other of the laser irradiation units, forming a second cutout at a position facing the first cutout in the composite material, and causing the second cutout to communicate with the first cutout. In the cutting-out step, the first cutout is formed by irradiating the composite material with the laser through a plurality of machining paths aligned in a width direction of the first cutout. In the cutting step, the second cutout is formed by irradiating the composite material with the laser through a plurality of machining paths aligned in a width direction of the second cutout. 
     According to the configurations, the composite material can be cut by forming the first cutout on one side of the composite material and forming the second cutout on the other side of the composite material. Therefore, compared to a case where the composite material is cut by irradiating the composite material with the laser from one side of the composite material, a removal amount can be reduced. Accordingly, a machining speed of cutting machining can be improved. 
     In addition, it is preferable to adopt a configuration as follows. The composite material is cut along a cutting line extending in a cutting progress direction. The cutting line includes a plurality of first cutout regions set to be aligned in the progress direction in which the cutting line extends, on one side in the thickness direction of the composite material, and a plurality of second cutout regions set to be aligned in the progress direction in which the cutting line extends, on the other side in the thickness direction of the composite material. In the cutting-out step, the first cutout is formed by irradiating the first cutout region with the laser. In the cutting step, the second cutout is formed by irradiating the second cutout region with the laser. The composite material is cut along the cutting line while the cutting-out step and the cutting step are alternately performed from one side toward the other side in the progress direction of the cutting line. 
     In addition, it is preferable to adopt a configuration as follows. The composite material is cut along a cutting line extending in a cutting progress direction. The cutting line includes a plurality of first cutout regions set to be aligned in the progress direction in which the cutting line extends, on one side in the thickness direction of the composite material, and a plurality of second cutout regions set to be aligned in the progress direction in which the cutting line extends, on the other side in the thickness direction of the composite material. In the cutting-out step, the first cutout is formed by irradiating the first cutout region with the laser. In the cutting step, the second cutout is formed by irradiating the second cutout region with the laser. The control unit cuts the composite material along the cutting line while alternately performing the cutting-out step and the cutting step from one side toward the other side in the progress direction of the cutting line by causing the laser switch to alternately switch between the first laser head and the second laser head. 
     According to the configurations, the cutting-out step and the cutting step are alternately performed. In this manner, the cutting-out step and the cutting step do not need to be simultaneously performed. Accordingly, it is not necessary to introduce a device for simultaneously performing the cutting-out step and the cutting step. Therefore, the machining speed of the cutting machining can be improved while a device configuration can be prevented from increasing. 
     In addition, it is preferable to adopt a configuration as follows. The composite material is cut along a cutting line extending in a cutting progress direction. The cutting line includes a plurality of first cutout regions set to be aligned in the progress direction in which the cutting line extends, on one side in the thickness direction of the composite material, and a plurality of second cutout regions set to be aligned in the progress direction in which the cutting line extends, on the other side in the thickness direction of the composite material. In the cutting-out step, the first cutout is formed by irradiating the first cutout region with the laser. In the cutting step, the second cutout is formed by irradiating the second cutout region with the laser. The composite material is cut along the cutting line by simultaneously performing the cutting-out step and the cutting step from one side toward the other side in the progress direction of the cutting line, and performing the cutting-out step prior to the cutting step. 
     In addition, it is preferable to adopt a configuration as follows. The composite material is cut along a cutting line extending in a cutting progress direction. The cutting line includes a plurality of first cutout regions set to be aligned in the progress direction in which the cutting line extends, on one side in the thickness direction of the composite material, and a plurality of second cutout regions set to be aligned in the progress direction in which the cutting line extends, on the other side in the thickness direction of the composite material. In the cutting-out step, the first cutout is formed by irradiating the first cutout region with the laser. In the cutting step, the second cutout is formed by irradiating the second cutout region with the laser. The control unit cuts the composite material along the cutting line by causing the first laser head and the second laser head to irradiate the composite material with the laser, simultaneously performing the cutting-out step and the cutting step from one side toward the other side in the progress direction of the cutting line, and performing the cutting-out step prior to the cutting step. 
     According to the configurations, the cutting-out step and the cutting step can be simultaneously performed. Accordingly, the machining speed of the cutting machining can be further improved. 
     In addition, it is preferable to adopt a configuration as follows. In the cutting step, the composite material is shielded from the laser by a receiving member that receives the laser emitted for irradiation from the other side in the thickness direction of the composite material. 
     According to the configuration, in the cutting step, even when the laser passes through the first cutout and one side is irradiated with the laser, the composite material is shielded from the laser by the receiving member. In this manner, it is possible to prevent one side from being irradiated with the laser. 
     In addition, it is preferable to adopt a configuration as follows. In the composite material, one side in the thickness direction is a lower side, and the other side in the thickness direction is an upper side. In the cutting-out step, the laser is emitted for irradiation from the lower side toward the upper side in the thickness direction of the composite material. In the cutting step, the laser is emitted for irradiation from the upper side toward the lower side in the thickness direction of the composite material. 
     According to the configuration, in the cutting step, the laser can be emitted for irradiation toward the lower side. Accordingly, the laser is emitted for irradiating a ground side, and thus, the laser can be prevented from being scattered in air. 
     In addition, it is preferable to adopt a configuration as follows. The composite material is cut along a cutting line extending in a cutting progress direction. A machining line is set along the thickness direction of the composite material. During the cutting machining, an irradiation direction of the laser is tilted with respect to the machining line set in the composite material, in a cross section perpendicular to the progress direction. 
     In addition, it is preferable to adopt a configuration as follows. The composite material is cut along a cutting line extending in a cutting progress direction, and a machining line is set along a thickness direction of the composite material. The laser machining device further includes a laser tilting unit that tilts an irradiation direction of the laser with respect to the machining line set in the composite material, in a cross section perpendicular to the progress direction. 
     According to the configurations, the irradiation direction of the laser is tilted with respect to the machining line. In this manner, a machining surface can be prevented from being tilted with respect to the machining line, and the machining surface can be set along the machining line. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view schematically illustrating a laser machining device according to Embodiment 1. 
         FIG. 2  is a view for describing an example relating to a laser machining method according to Embodiment 1. 
         FIG. 3  is a view for describing an example relating to the laser machining method according to Embodiment 1. 
         FIG. 4  is a view for describing a cutout region of the laser machining method according to Embodiment 1. 
         FIG. 5  is a sectional view of a composite material cut by the laser machining method according to Embodiment 1. 
         FIG. 6  is a view schematically illustrating a laser machining device according to Embodiment 2. 
         FIG. 7  is a view for describing a cutout region of a laser machining method according to Embodiment 2. 
         FIG. 8  is a view schematically illustrating a laser machining device according to Embodiment 3. 
         FIG. 9  is a sectional view of a composite material cut by a laser machining method according to Embodiment 3. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. The present invention is not limited by the embodiments. In addition, configuration elements in the following embodiments include those which can be easily replaced by those skilled in the art, or those which are substantially the same. In addition, the configuration elements described below can be appropriately combined with each other, and when there are a plurality of the embodiments, the embodiments can be combined with each other. 
     Embodiment 1 
       FIG. 1  is a view schematically illustrating a laser machining device according to Embodiment 1. As illustrated in  FIG. 1 , a laser machining device  10  according to Embodiment 1 is a device that can cut a composite material  5  by irradiating the composite material  5  serving as a machining object with a laser L. 
     For example, the composite material  5  includes fiber reinforced plastics such as carbon fiber reinforced plastic (CFRP), glass fiber reinforced plastic (GFRP), and glass long fiber reinforced plastic (GMT). 
     As illustrated in  FIG. 1 , the laser machining device  10  is configured to include a laser irradiation device  11 , a laser switch  16 , two scanning optical systems (laser scanners)  12   a  and  12   b , two light condensing optical systems (laser heads)  13   a  and  13   b , two gas nozzles  14   a  and  14   b , two shielding plates (receiving members)  17   a  and  17   b , and a control unit  15 . 
     The laser irradiation device  11  is a device that outputs the laser L. The laser irradiation device  11  may use a pulse wave (continuous wave) or a continuous wave (CW) as the laser L to be output. In Embodiment 1, it is preferable to use the laser irradiation device  11  that irradiates the composite material  5  with the laser L having the continuous wave capable of continuously supplying energy. In addition, the laser irradiation device  11  may irradiate the composite material  5  with the laser L in a single mode or a multi-mode. In Embodiment 1, it is preferable to use the laser irradiation device  11  that irradiates the composite material  5  with the laser L in a single mode having a high light condensing property. 
     The laser switch  16  switches between light guide paths of the laser L emitted for irradiation from the laser irradiation device  11 . The laser switch  16  switches the light guide path so that the laser L is oriented toward a front surface side of the composite material  5 , or switches the light guide path so that the laser L is oriented toward a rear surface side of the composite material  5 . 
     Specifically, the laser switch  16  switches between a first light guide path T 1  oriented toward the rear surface side of the composite material  5  and a second light guide path T 2  oriented toward the front surface side of the composite material  5 . 
     The two scanning optical systems  12   a  and  12   b  include a first scanning optical system  12   a  provided in the first light guide path T 1  and a second scanning optical system  12   b  provided in the second light guide path T 2 . The first scanning optical system  12   a  is an optical system that causes the laser switch  16  to switch the first light guide path T 1  so that the rear surface of the composite material  5  is scanned with the laser L passing through the first light guide path T 1 . The second scanning optical system  12   b  is an optical system that causes the laser switch  16  to switch the second light guide path T 2  so that the front surface of the composite material  5  is scanned with the laser L passing through the second light guide path T 2 . The first scanning optical system  12   a  and the second scanning optical system  12   b  include a scanner capable of operating the laser L on the rear surface and the front surface of the composite material  5 . For example, as the scanner, a galvanometer mirror is used. 
     The two light condensing optical systems  13   a  and  13   b  include a first light condensing optical system  13   a  provided in the first light guide path T 1  and a second light condensing optical system  13   b  provided in the second light guide path T 2 . The first light condensing optical system  13   a  is an optical system that condenses the laser L emitted from the first scanning optical system  12   a  and irradiates the rear surface of the composite material  5  with the condensed laser L. The second light condensing optical system  13   b  is an optical system that condenses the laser L emitted from the second scanning optical system  12   b  and irradiates the front surface of the composite material  5  with the condensed laser L. The first light condensing optical system  13   a  and the second light condensing optical system  13   b  are configured to include an optical member such as a light condensing lens. 
     The two gas nozzles  14   a  and  14   b  include a first gas nozzle  14   a  provided on the rear surface side of the composite material  5  and a second gas nozzle  14   b  provided on the front surface side of the composite material  5 . The first gas nozzle  14   a  injects an inactive assist gas toward the rear surface of the composite material  5 . The second gas nozzle  14   b  injects an assist gas toward the front surface of the composite material  5 . An injection direction of the assist gas is a direction intersecting with an irradiation direction of the laser L, and is a direction along the rear surface and the front surface of the composite material  5 . Although illustration is omitted, the laser machining device  10  is provided with a suction port for suctioning the assist gas. 
     The two shielding plates  17   a  and  17   b  include a first shielding plate  17   a  provided on the rear surface side of the composite material  5  and a second shielding plate  17   b  provided on the front surface side of the composite material  5 . The first shielding plate  17   a  is attached to the first light condensing optical system  13   a , and can shield the composite material  5  from the laser L emitted from the second light condensing optical system  13   b . The second shielding plate  17   b  is attached to the second light condensing optical system  13   b , and can shield the composite material  5  from the laser L emitted from the first light condensing optical system  13   a.    
     The control unit  15  is connected to each unit including the laser irradiation device  11 , the laser switch  16 , and the two scanning optical systems  12   a  and  12   b , and controls each unit to control an operation of the laser machining device  10 . For example, the control unit  15  adjusts irradiation conditions of the laser L emitted for irradiation from the laser irradiation device  11  by controlling the laser irradiation device  11 . In addition, the control unit  15  performs switching control on the laser switch  16  to guide the laser L to the first light guide path T 1  or the second light guide path T 2 . Furthermore, for example, the control unit  15  controls a scanning operation of the laser L on the front surface and the rear surface of the composite material  5  by controlling the first scanning optical system  12   a  and the second scanning optical system  12   b.    
     The composite material  5  is supported at a predetermined position by a support member (not illustrated). For example, the composite material  5  is formed in a flat plate shape, and the front surface and the rear surface of the composite material  5  are substantially perpendicularly irradiated with the laser L emitted to irradiate the composite material  5 . That is, an optical axis A (refer to  FIG. 2 ) of the laser L extends along a thickness direction of the composite material  5 . In addition, the front surface of the composite material  5  is an upper surface in a vertical direction, and the rear surface is a lower surface in the vertical direction. Then, the composite material  5  is supported so that the front surface and the rear surface are horizontal planes. The composite material  5  may be supported to be movable within the horizontal plane. 
     The laser machining device  10  configured as described above irradiates the composite material  5  with the laser L emitted from the laser irradiation device  11 , and guides the laser L emitted for irradiation to the laser switch  16 . The laser switch  16  guides the laser L to the first light guide path T 1  or the second light guide path T 2 , based on the switching control performed by the control unit  15 . The laser L guided to the first light guide path T 1  is guided to the first scanning optical system  12   a . The laser machining device  10  changes an irradiation position of the laser L on the rear surface of the composite material  5  by scanning the rear surface of the composite material  5  with the laser L incident on the first scanning optical system  12   a . The laser machining device  10  causes the laser L emitted from the first scanning optical system  12   a  to be incident on the first light condensing optical system  13   a , and irradiates the rear surface of the composite material  5  with the condensed laser L. On the other hand, the laser L guided to the second light guide path T 2  is guided to the second scanning optical system  12   b . The laser machining device  10  changes the irradiation position of the laser L on the front surface of the composite material  5  by scanning the front surface of the composite material  5  with the laser L incident on the second scanning optical system  12   b . The laser machining device  10  causes the laser L emitted from the second scanning optical system  12   b  to be incident on the second light condensing optical system  13   b , and irradiates the front surface of the composite material  5  with the condensed laser L. 
     Next, a laser machining method of performing cutting machining for cutting the composite material  5  by using the above-described laser machining device  10  will be described with reference to  FIGS. 2 to 4 .  FIG. 2  is a view for describing an example relating to the laser machining method according to Embodiment 1.  FIG. 3  is a view for describing an example relating to the laser machining method according to Embodiment 1.  FIG. 4  is a view for describing a cutout region of the laser machining method according to Embodiment 1. Here, for example, the composite material  5  has a plate thickness of 10 mm or larger. 
     In the laser machining method of Embodiment 1, the front surface and the rear surface of the composite material  5  are alternately irradiated with the laser L to cut the composite material  5 . In addition, as illustrated in  FIG. 2 , the composite material  5  has a flat plate shape (illustration is partially omitted). In the laser machining method, a machining line I extending along a thickness direction (upward-downward direction in  FIG. 2 ) of the composite material  5  is set in advance, and a cutting line C extending in a cutting progress direction (depth direction in  FIG. 2 ) is set in advance in the composite material  5  before cutting machining is performed. 
     In the laser machining method of Embodiment 1, a cutting-out step of irradiating the above-described machining line I with the laser L toward the rear surface of the composite material  5  from a lower side in the thickness direction of the composite material  5 , and a cutting step of irradiating the above-described machining line I with the laser L toward the front surface of the composite material  5  from the upper side in the thickness direction of the composite material  5  are performed. In the cutting-out step, the composite material  5  is irradiated with the laser L from the lower side in the thickness direction of the composite material  5  to form a first cutout  21  in the composite material  5  on the lower side of the machining line I. In the cutting step, the composite material  5  is irradiated with the laser L from the upper side in the thickness direction of the composite material  5  to form a second cutout  22  in the composite material  5  on the upper side of the machining line I. Then, in the cutting step, the composite material  5  is cut by causing the second cutout  22  to communicate with the first cutout  21 . 
     In addition, in the cutting-out step, the first cutout  21  is formed by irradiating the composite material  5  with the laser L through a plurality of machining paths aligned in the width direction of the first cutout  21 . The plurality of machining paths in the cutting-out step are set to be aligned in the width direction (rightward-leftward direction in  FIG. 2 ) perpendicular to the thickness direction and the depth direction, and each of the machining paths is set to extend along the cutting line C. In this case, the plurality of machining paths are set to be aligned at a predetermined pitch interval P in the width direction. For example, the pitch interval P between the machining paths is provided at an equal interval. 
     Similarly, in the cutting step, the second cutout  22  is formed by irradiating the composite material  5  with the laser L through a plurality of machining paths aligned in the width direction of the second cutout  22 . As in the cutting-out step, the plurality of machining paths in the cutting step are set to be aligned in the width direction, and each of machining paths is set to extend along the cutting line C. In this case, the plurality of machining paths are set to be aligned at a predetermined pitch interval P in the width direction. For example, the pitch interval P between the machining paths is provided at an equal interval. 
     In addition, as illustrated in  FIGS. 3 and 4 , in the laser machining method of Embodiment 1, a first cutout region  25  corresponding to the first cutout  21  and a second cutout region  26  corresponding to the second cutout  22  are set in the cutting line C. 
     A plurality of the first cutout regions  25  are set to be aligned in the progress direction in which the cutting line C extends, on the lower side in the thickness direction of the composite material  5 . The plurality of first cutout regions  25  are regions having the same size. The first cutout region  25  has a length which is a half of the thickness of the composite material  5  in the thickness direction of the composite material  5 . 
     A plurality of the second cutout regions  26  are set to be aligned in the progress direction in which the cutting line C extends, on the upper side in the thickness direction of the composite material  5 . The plurality of second cutout regions  26  are regions having the same size, and are regions having a size the same as that of the first cutout region  25 . Therefore, the second cutout region  26  also has a length which is a half of the thickness of the composite material  5  in the thickness direction of the composite material  5 . 
     The first cutout region  25  and the second cutout region  26  are disposed in a grid pattern within a plane including the machining line I and the cutting line C. The first cutout region  25  and the second cutout region  26  may partially overlap each other in the center in the thickness direction of the composite material  5 . 
     Then, during the cutting machining, the cutting-out step and the cutting step are performed, based on the machining line I, the cutting line C, and the plurality of machining paths which are set as described above. As illustrated in  FIG. 4 , during the cutting machining, the composite material  5  is cut along the cutting line C while the cutting-out step and the cutting step are alternately performed from one side (right side in  FIG. 4 ) toward the other side (left side in  FIG. 4 ) in the progress direction of the cutting line C. 
     Specifically, during the cutting machining, the laser switch  16  first guides the laser L to the first light guide path T 1 . Then, the cutting-out step is performed on the first cutout region  25  (“1” in  FIG. 4 ) on the right side in  FIG. 4  of the cutting line C, thereby forming the first cutout  21 . Subsequently, during the cutting machining, the laser switch  16  guides the laser L to the second light guide path T 2 . Then, the cutting step is performed on the second cutout region  26  (“2” in  FIG. 4 ) on the right side in  FIG. 4  of the cutting line C, that is, on the second cutout region  26  at a position facing the first cutout  21 , thereby forming the second cutout  22 . In the cutting step, even when the laser L passes through the first cutout  21 , the composite material  5  is shielded from the laser L by the second shielding plate  17   b . In addition, in the cutting-out step, the laser L does not pass through the composite material  5 . However, for safety, the first shielding plate  17   a  is provided. 
     Thereafter, in the cutting step, the laser L is switched to the first light guide path T 1  by the laser switch  16 , and the cutting-out step is performed again on the first cutout region  25  (“3” in  FIG. 4 ) adjacent to the first cutout  21  of the cutting line C, thereby forming the first cutout  21 . Subsequently, in the cutting step, the laser L is switched to the second light guide path T 2  by the laser switch  16 , and the cutting step is performed on the second cutout region  26  (“4” in  FIG. 4 ) at a position facing the first cutout  21 , thereby forming the second cutout  22 . Then, in the cutting step, the composite material  5  is cut on the cutting line C by performing the cutting-out step and the cutting step a plurality of times (N times). 
     Since the cutting machining is performed as described above, a cutting surface perpendicular to the cutting line C of the composite material  5  is formed as illustrated in  FIG. 5 . As illustrated in  FIG. 5 , the first cutout  21  and the second cutout  22  which are formed along the machining line I are formed in a tapered shape tapered toward the center in the thickness direction of the composite material  5 . A removal amount in this case has a volume in which the first cutout  21  and the second cutout  22  are formed. On the other hand, a dotted line illustrated in  FIG. 5  is a cutout formed during the cutting machining in the related art, that is, the cutting machining for cutting the composite material  5  by irradiating the composite material  5  with the laser L from one side surface of the composite material  5 . The cutout is formed in a tapered shape tapered from the front surface toward the rear surface of the composite material  5 . The removal amount removed during the cutting machining in the related art is larger than the removal amount in Embodiment 1. 
     As described above, according to Embodiment 1, the composite material  5  can be cut by forming the first cutout  21  on the lower side of the composite material  5 , and forming the second cutout  22  on the upper side of the composite material  5 . Therefore, compared to a case where the composite material  5  is cut by irradiating the composite material  5  with the laser L from one side of the composite material  5 , the removal amount can be reduced. Accordingly, a machining speed of the cutting machining can be improved. 
     In addition, according to Embodiment 1, the cutting-out step and the cutting step are alternately performed. In this manner, the cutting-out step and the cutting step do not need to be simultaneously performed. Accordingly, it is not necessary to introduce a device for simultaneously performing the cutting-out step and the cutting step. Therefore, the machining speed of the cutting machining can be improved while a device configuration of the laser machining device  10  can be prevented from increasing. 
     In addition, according to Embodiment 1, in the cutting step, even when the laser L passing through the first cutout  21  is emitted for irradiating the lower side, the composite material  5  is shielded from the laser L by the second shielding plate  17   b . In this manner, the lower side can be prevented from being irradiated with the laser L. 
     In addition, according to Embodiment 1, in the cutting step, the laser L can be emitted for irradiation toward the lower side. Accordingly, the laser L is emitted for irradiating a ground side, and thus, the laser L can be prevented from being scattered in air. 
     Embodiment 2 
     Next, a laser machining device and a laser machining method according to Embodiment 2 will be described with reference to  FIGS. 6 and 7 . In Embodiment 2, in order to avoid repeated description, elements different from those in Embodiment 1 will be described, and description will be made by assigning the same reference numerals to elements having configurations the same as those in Embodiment 1.  FIG. 6  is a view schematically illustrating the laser machining device according to Embodiment 2.  FIG. 7  is a view for describing a cutout region of the laser machining method according to Embodiment 2. 
     In the laser machining device and the laser machining method of Embodiment 1, the composite material  5  is cut along the cutting line C while the cutting-out step and the cutting step are alternately performed. In contrast, in the laser machining device and the laser machining method of Embodiment 2, the composite material  5  is cut along the cutting line C while the cutting-out step and the cutting step are simultaneously performed. 
     As illustrated in  FIG. 6 , a laser machining device  30  of Embodiment 2 includes two laser irradiation devices  11   a  and  11   b , the two scanning optical systems  12   a  and  12   b , the two light condensing optical systems  13   a  and  13   b , the two gas nozzles  14   a  and  14   b , the two shielding plates  17   a  and  17   b , and the control unit  15 . The two scanning optical systems  12   a  and  12   b , the two light condensing optical systems  13   a  and  13   b , the two gas nozzles  14   a  and  14   b , and the two shielding plates  17   a  and  17   b  are the same as those in Embodiment 1. Accordingly, description thereof will be omitted. In addition, the laser machining device  30  of Embodiment 2 has a configuration from which the laser switch  16  provided in the laser machining device  10  of Embodiment 1 is omitted. 
     The two laser irradiation devices  11   a  and  11   b  include a first laser irradiation device  11   a  that irradiates the front surface side of the composite material  5  with the laser L, and a second laser irradiation device  11   b  that irradiates the rear surface side of the composite material  5  with the laser L. The first laser irradiation device  11   a  emits the laser L for irradiation toward the first scanning optical system  12   a . In addition, the second laser irradiation device  11   b  emits the laser L for irradiation toward the second scanning optical system  12   b.    
     The control unit  15  controls the two laser irradiation devices  11   a  and  11   b , controls each of the two laser irradiation devices  11   a  and  11   b  so that the composite material  5  is irradiated with the laser L, or controls any one of the two laser irradiation devices  11   a  and  11   b  so that the composite material  5  is irradiated with the laser L. 
     The laser machining device  30  configured as described above emits the laser L for irradiation from each of the two laser irradiation devices  11   a  and  11   b , and causes the emitted laser L for irradiation to be incident on each of the two scanning optical systems  12   a  and  12   b . The laser machining device  30  changes an irradiation position of the laser L on the rear surface of the composite material  5  by scanning the rear surface of the composite material  5  with the laser L incident on the first scanning optical system  12   a . The laser machining device  30  causes the laser L emitted from the first scanning optical system  12   a  to be incident on the first light condensing optical system  13   a , and irradiates the rear surface of the composite material  5  with the condensed laser L. In addition, the laser machining device  30  changes the irradiation position of the laser L on the front surface of the composite material  5  by scanning the front surface of the composite material  5  with the laser L incident on the second scanning optical system  12   b . The laser machining device  10  causes the laser L emitted from the second scanning optical system  12   b  to be incident on the second light condensing optical system  13   b , and irradiates the front surface of the composite material  5  with the condensed laser L. 
     Next, the laser machining method of performing cutting machining for cutting the composite material  5  by using the above-described laser machining device  30  will be described with reference to  FIG. 7 . 
     In the laser machining method of Embodiment 2, the composite material  5  is cut by simultaneously irradiating the front surface and the rear surface of the composite material  5  with the lasers L. The cutting-out step and the cutting step are the same as those in Embodiment 1, and thus, description thereof will be omitted. In addition, the first cutout region  25  and the second cutout region  26  which are set in the cutting line C are the same as those in Embodiment 1, and thus, description thereof will be omitted. 
     As illustrated in  FIG. 7 , during the cutting machining, the composite material  5  is cut along the cutting line C while the cutting-out step and the cutting step are simultaneously performed from one side (right side in  FIG. 7 ) toward the other side (left side in  FIG. 7 ) in the progress direction of the cutting line C. 
     Specifically, during the cutting machining, first, the composite material  5  is first irradiated with the laser L by the first laser irradiation device  11   a , and performs the cutting-out step on the first cutout region  25  (“1” in  FIG. 7 ) on the right side in  FIG. 4  of the cutting line C, thereby forming the first cutout  21 . Subsequently, during the cutting machining, the cutting-out step and the cutting step are simultaneously performed. That is, during the cutting machining, the composite material  5  is irradiated with the laser L by the second laser irradiation device  11   b , and the cutting step is performed on the second cutout region  26  (“2” on the upper side of  FIG. 7 ) on the right side in  FIG. 4  of the cutting line C, that is, the second cutout region  26  at a position facing the first cutout  21 , thereby forming the second cutout  22 . Simultaneously, during the cutting machining, the cutting-out step is performed on the first cutout region  25  (“2” on the lower side in  FIG. 7 ) adjacent to the first cutout  21  of the cutting line C, thereby forming the first cutout  21 . Therefore, in the cutting line C, the cutting-out step is performed prior to the cutting step. 
     Thereafter, in the cutting step, the cutting step is performed again on the second cutout region  26  (“3” on the upper side in  FIG. 7 ) at the position facing the first cutout  21 , thereby forming the second cutout  22 . The cutting-out step is performed on the first cutout region  25  (“3” on the lower side in  FIG. 7 ) adjacent to the first cutout  21 , thereby forming the first cutout  21 . Then, in the cutting step, the cutting-out step and the cutting step are performed a plurality of times (N−1 times). Thereafter, in the Nth time, the cutting step is performed on the second cutout region  26  (“N” on the upper side in  FIG. 7 ) at the position facing the first cutout  21 . In this manner, the composite material  5  is cut in the cutting line C. 
     As described above, according to Embodiment 2, the cutting-out step and the cutting step can be simultaneously performed. Accordingly, the machining speed of the cutting machining can be further improved. 
     Embodiment 3 
     Next, a laser machining device and a laser machining method according to Embodiment 3 will be described with reference to  FIGS. 8 and 9 . In Embodiment 3, in order to avoid repeated description, elements different from those in Embodiments 1 and 2 will be described, and description will be made by assigning the same reference numerals to elements having configurations the same as those in Embodiments 1 and 2.  FIG. 8  is a view schematically illustrating the laser machining device according to Embodiment 3.  FIG. 9  is a sectional view of a composite material cut by the laser machining method according to Embodiment 3. 
     In the laser machining devices  10  and  30  and the laser machining method according to Embodiment 1 and Embodiment 2, the irradiation direction (optical axis A) of the laser L emitted for irradiating the front surface and the rear surface of the composite material  5  in the cutting-out step and the cutting step is a direction extending along the thickness direction of the composite material  5 . Here, in a case where one side is a product side and the other side is a remaining portion side across the machining line I, when the machining line I is set in a product side end portion, a portion on the product side (front surface side) is removed by the laser. When the machining is performed by sliding a position of the machining line I to be away from the product side in order to avoid the portion on the product side (front surface side) from being removed by the laser, the remaining portion is formed on the product side (rear surface side). Consequently, when a vertical cutting surface is required, it is necessary to perform post processing. Therefore, in the laser machining device and the laser machining method according to Embodiment 3, the irradiation direction (optical axis A) of the laser L emitted for irradiating the front surface and the rear surface of the composite material  5  in the cutting-out step and the cutting step is tilted with respect to the thickness direction of the composite material  5 . 
     A laser machining device  40  of Embodiment 3 further includes a laser tilting unit  41  that relatively tilts the laser L with respect to the composite material  5  in the laser machining device  10  of Embodiment 1. Embodiment 3 adopts a configuration in which the composite material  5  is fixed and the laser L is tilted. However, a configuration may be adopted so that the laser L is fixed and the composite material  5  is movable. The laser tilting unit  41  tilts the laser L with respect to the machining line I by tilting the scanning optical systems  12   a  and  12   b  and the light condensing optical systems  13   a  and  13   b . The machining line I is a line set along the thickness direction of the composite material  5 . Specifically, the laser tilting unit  41  tilts the optical axis A of the laser L with respect to a depth direction in which the machining line I extends, in a cross section (for example,  FIGS. 8 and 9 ) perpendicular to the progress direction of the cutting line C. The laser tilting unit  41  may physically tilt at least one of the scanning optical systems  12   a  and  12   b  and the light condensing optical systems  13   a  and  13   b , or may tilt the laser L by using an optical member included in the scanning optical systems  12   a  and  12   b  or the light condensing optical systems  13   a  and  13   b . The laser tilting unit  41  is not particularly limited. 
     As illustrated in  FIG. 8 , the laser L tilted by the laser tilting unit  41  is condensed at a predetermined angle θ with respect to the optical axis A. Then, the optical axis A of the laser L is tilted with respect to the depth direction of the machining line I. That is, in view of the predetermined angle θ for condensing the laser L, a tilt angle of the optical axis A is set with respect to the depth direction of the machining line I. The tilt angle is set in a range of 0.1° to 5°, preferably in a range of 0.1° to 2°, and more preferably in a range of 0.1° to 1°. 
     During the cutting machining of Embodiment 3, in the cutting-out step and the cutting step, the irradiation is performed by causing the laser tilting unit  41  to tilt the laser L with respect to the thickness direction of the composite material  5 . In this manner, the cutting surface perpendicular to the cutting line C of the composite material  5  is formed as illustrated in  FIG. 9 . As illustrated in  FIG. 9 , the first cutout  21  and the second cutout  22  which are formed along the machining line I are formed in a tapered shape tapered toward the center in the thickness direction of the composite material  5 . In this case, as the laser L is tilted, a tapered angle on a tilted side (left side in  FIG. 9 ) is an angle sharper than a tapered angle on a side (right side in  FIG. 9 ) opposite to the tilted side. 
     Therefore, when a machining surface (surface on the right side in  FIG. 9 ) of a product cut out from the composite material  5  after the cutting machining is set to have a shape along the machining line I, the laser L condensed at the predetermined angle θ with respect to the optical axis A is tilted to form the predetermined angle θ with respect to the machining line I. 
     As described above, according to Embodiment 3, the irradiation direction (optical axis A) of the laser L is tilted with respect to the machining line I. In this manner, the machining surface can be prevented from being tilted with respect to the machining line I, and the machining surface can be set along the machining line I. 
     REFERENCE SIGNS LIST 
     
         
         
           
               5 : Composite material 
               10 : Laser machining device 
               11 : Laser irradiation device 
               11   a ,  11   b : Laser irradiation device 
               12   a ,  12   b : Scanning optical system 
               13   a ,  13   b : Light condensing optical system 
               14   a ,  14   b : Gas nozzle 
               15 : Control unit 
               16 : Laser switch 
               17   a ,  17   b : Shielding plate 
               21 : First cutout 
               22 : Second cutout 
               25 : First cutout region 
               26 : Second cutout region 
               30 : Laser machining device (Embodiment 2) 
               40 : Laser machining device 
               41 : Laser tilting unit 
             T 1 : First light guide path 
             T 2 : Second light guide path 
             L: Laser 
             I: Machining line 
             C: Cutting line 
             A: Optical axis