JP2006224107A - Method and apparatus of laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus of laser beam machining, by which method and apparatus, the irradiation of a laser beam on a machining point can be sufficiently performed even if the surface of a workpiece is not flat. <P>SOLUTION: The apparatus of laser beam machining is composed of a plurality of converging optical systems 11a, 11b for converging a plurality (two in this case) of laser beams 12a, 12b on the same machining point p of the workpiece W, and a turning apparatus 20 which mounts the respective converging optical systems 11a, 11b and turns the optical axes of the respective converging optical systems 11a, 11b about the machining point p. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser processing method and a laser processing apparatus capable of creating a three-dimensional shape of a workpiece with high accuracy.

  In a conventional laser processing method, laser irradiation is performed from a tangential direction in order to create a three-dimensional shape on a workpiece (for example, Patent Document 1).

  FIG. 6 is a cross-sectional view for explaining a conventional three-dimensional shape creation process using a laser for non-contact adjustment of a tool shape. Here, as an example of the three-dimensional shape creation processing, truing for forming the grindstone shape so as to match the required shape of the workpiece will be described.

  In FIG. 6, an electrodeposition grindstone 30 includes a cylindrical grindstone base 9 attached to a motor (not shown), and a plating layer 8 and abrasive grains 7 formed by electrodeposition on the peripheral surface of the grindstone base 9. And have. For example, cBN abrasive grains are used for the abrasive grains 7, nickel plating is used for the plating layer 8, and a YAG laser is used for the laser oscillator 10. The condensing device 11 includes a lens and can condense the laser light 12 from the laser oscillator 10 to a beam diameter of 10 μm or less.

  When truing the electrodeposition grindstone 30, the motor is rotated to rotate the electrodeposition grindstone 30. In this state, the laser irradiation position and the irradiation direction are controlled, and the outermost peripheral abrasive grain 7 is irradiated with the laser beam 12 from the tangential direction of the grindstone 30 to melt and evaporate the outermost peripheral part of the abrasive grain 7. To remove. And the cylindrical truing process is performed by moving the laser beam 12 relatively in the axial direction (perpendicular to the paper surface) of the grindstone 30.

  Thus, since the truing process which irradiates the laser beam 12 from the tangential direction of the grindstone 30 is performed on the outermost abrasive grain 7 of the grindstone 30, only the abrasive grains 7 can be trued without damaging the plating layer 8. It becomes like this. As a result, the abrasive grains 7 do not fall off from the plating layer 8, and deformation of the plating layer 8 is suppressed, so that variations in the position of the cutting edge of the abrasive grains 7 are reduced. Can be controlled. Therefore, when the electrodeposition grindstone 30 that has been subjected to truing with high precision is used, high-precision machining and high-efficiency machining are possible.

  Further, the non-contact truing process using laser light can prevent the distortion of the grindstone due to the machining resistance and the variation in the abrasive grain position of the grindstone, which are problems in the contact truing process.

  Further, a low-rigidity grindstone such as a small-diameter shaft grindstone may cause distortion of the washer 9 by contact-type truing processing, but a non-contact-type grindstone can cope with such a low-rigidity grindstone. .

JP 2002-321155 A ([0032] to [0038], FIG. 9)

  Conventional laser processing is basically performed by penetrating or drilling a workpiece due to the straightness of the beam. As an application of this, two-dimensional contours viewed from the beam traveling direction due to the relative motion of the workpiece and the beam. There is a cutting process along. In this case, the three-dimensional position control of the processing point can be controlled along two axes orthogonal to the beam, but in principle cannot be controlled in the depth direction (laser traveling direction). Note that the control based on the intensity and the irradiation time is control of the amount of processing from the workpiece surface, and not three-dimensional position control. The control in the depth direction must depend on mechanical removal processing such as milling.

  Further, in the truing process using the laser beam shown in FIG. 6, if a large uneven shape exists on the workpiece surface, a portion where the laser beam cannot be sufficiently irradiated appears. For example, as shown in FIG. 7, if the workpiece surface is flat, the target abrasive grains 7 can be accurately irradiated with the laser beam 12. However, as shown in FIG. 8, if the workpiece surface is uneven, even if the laser beam 12 is aimed at the abrasive grain 7 located in the concave portion, it is blocked by the convex portion on the front side. A problem of laser irradiation or insufficient irradiation of the grains 7 occurs. Therefore, in this method, the truing process can be carried out only with a convex grindstone having a substantially circular cross section.

  An object of the present invention is to provide a laser processing method and a laser processing apparatus capable of sufficiently irradiating a processing point with laser light even if the workpiece surface shape is not flat.

In order to achieve the above object, a laser processing method according to the present invention includes a step of arranging optical axes of laser beams so that a plurality of laser beams intersect at the same processing point of a workpiece,
And a step of performing processing by changing the irradiation angle of each laser beam using the processing point as a rotation fulcrum.

Further, the laser processing apparatus according to the present invention includes a plurality of condensing optical systems for condensing a plurality of laser beams at the same processing point of the workpiece,
Each condensing optical system is mounted, and includes a rotating device for rotating the optical axis of each condensing optical system with the processing point as a rotation fulcrum.

  According to the laser processing method of the present invention, in a state where a plurality of laser beams intersect and converge at the same processing point, processing is performed by changing the irradiation angle of each laser beam using the position of the processing point as a rotation fulcrum. Thus, an obstacle present around the processing point can be avoided, and the laser beam irradiation to the processing point is not blocked. In addition, since a substantially spherical light energy distribution can be realized with the processing point as the center, three-dimensional removal processing that is impossible with the conventional laser processing method is also possible.

  In addition, according to the laser processing apparatus of the present invention, an appropriate laser irradiation angle is maintained with respect to the processing point by providing a rotation device for rotating the optical axis of each condensing optical system with the processing point as a rotation fulcrum. Therefore, the laser beam is not blocked by the obstacle around the processing point, and it is possible to set the irradiation angle with higher processing efficiency. In addition, since a substantially spherical light energy distribution can be realized with the processing point as the center, three-dimensional removal processing that is impossible with the conventional laser processing method is also possible.

Embodiment 1 FIG.
1 and 2 are schematic perspective views showing Embodiment 1 of the present invention. Hereinafter, although truing processing of a grindstone will be described as an example, the present invention is applicable to general laser processing. In FIGS. 1 and 2, the condensing optical system is omitted in order to express the intersecting region of the laser beams.

  1 and 2, a processing point p is set on the surface of a workpiece W such as a grindstone. Laser beams 12a and 12b from a plurality (two in this case) of laser light sources 10a and 10b are irradiated to the processing point p. At this time, by using a condensing optical system (not shown), the energy density of the laser beam condensed at the processing point p is increased, and the processing efficiency is dramatically improved. The energy of the laser beams 12a and 12b is absorbed in a region centered on the processing point p, converted into thermal energy, the temperature of the processing point p rises, and is melted / evaporated or sublimated to remove the processing point. Done.

  Here, due to the physical properties of the workpiece W (light absorption rate, thermal conductivity, melting point, etc.), it is impossible to remove the processing point p with only one laser beam, but it is removed with the energy of both laser beams 12a and 12b. The energy of each laser beam (light intensity × irradiation time) is set as possible. With such a setting, it is possible to process only the intersecting region of both laser beams.

  For example, when the workpiece W is aluminum (Al), the melting point is 660 ° C., so that only one laser beam can be set to a temperature lower than the melting point, for example, 600 ° C. When intersecting at the same processing point p, the temperature rises to 660 ° C. or higher, and only the intersecting region melts. At this time, if high-pressure gas or the like is sprayed onto the processing point p to blow off the molten aluminum, the portion corresponding to the intensity distribution (substantially spherical) in the laser crossing region is removed at the processing point p, resulting in a concave shape. .

Further, when the workpiece W is alumina (Al ₂ O ₃ ), the melting point is about 2000 ° C. and the boiling point is about 3000 ° C., so that the temperature can be raised to a temperature lower than the melting point, for example, 1900 ° C. with only one laser beam. When both laser beams intersect at the same processing point p, the temperature rises to about 4000 ° C., and only the intersecting region evaporates. Also in this case, at the processing point p, the portion corresponding to the intensity distribution (substantially spherical) in the laser crossing region is evaporated and removed, resulting in a concave shape. Further, by selecting the material of the workpiece W, it is possible to set the energy of the laser beam so as to sublimate from the solid directly to the gas. Actually, since there is latent heat of fusion and evaporation (heat of fusion and heat of vaporization), the temperature rise due to both laser beams is not strictly twice that of a single laser beam.

  With respect to the irradiation angle of the laser beam, in FIG. 1, one laser beam 12a is irradiated along substantially the normal direction of the surface near the processing point p, and the other laser beam 12b is approximately the surface near the processing point p. Irradiating along the tangential direction. In this case, the laser beam may be blocked as shown in FIGS. In order to avoid such interruption of the laser beam, both laser beams 12a and 12b are rotated together with the processing point p as a rotation fulcrum as shown in FIG. 2, and the irradiation angle of each laser beam 12a and 12b is changed. By doing so, obstacles existing around the processing point p can be avoided, and laser processing can be easily performed even if the processing point p exists in the recess.

  Since the machining point p corresponds to a laser beam intersection region, the position of the machining point p can be determined three-dimensionally by controlling the angle of each laser beam axis and / or controlling the position of the workpiece W. Therefore, the laser processing method according to the present invention enables three-dimensional shape creation processing using laser light, which has never been possible before. In addition, the beam waist of the laser beam can theoretically be narrowed down to about the wavelength of the laser beam, so it is possible to remove a very small area that spreads at the focal point of the laser beam, realizing a removal process that is fine and has high positioning accuracy. it can.

  Here, the truing process of the grindstone is taken as an example, but the present invention is extremely effective for the removal process that requires fine processing and high-precision processing, for example, mold processing of optical parts.

  In this example, two laser beams are used as an example. However, when the melting point and boiling point cannot be properly realized, the number of laser beams can be further increased to optimize the temperature rise. . For example, in order to directly vaporize and remove aluminum, since the boiling point is 2500 ° C., when the temperature is raised to 600 ° C. with one laser beam, at least five laser beams may be used.

Embodiment 2. FIG.
FIG. 3 is a schematic sectional view showing Embodiment 2 of the present invention. The laser processing apparatus includes a plurality of condensing optical systems 11a and 11b for condensing a plurality (here, two) of laser beams 12a and 12b at the same processing point p of the workpiece W, and each condensing optical system 11a, 11b is mounted, and includes a rotating device 20 for rotating the optical axes of the respective condensing optical systems 11a and 11b with the processing point p as a rotation fulcrum.

  The rotating device 20 is equipped with a hollow housing 40 for introducing the laser light 12 and a split optical system 50 that is rotatably supported with respect to the hollow housing 40 and divides the laser light 12 into two laser lights 12a and 12b. The main housing 42, the sub housing 44 a that is supported rotatably with respect to the main housing 42, and is mounted with the condensing optical system 11 a that condenses the divided laser light 12 a, and is rotatable with respect to the main housing 42. The auxiliary housing 44b is mounted with a condensing optical system 11b that collects the laser beam 12b that is supported and divided.

  First, the course of laser light will be described. Laser light 12 from a laser oscillator (not shown) is introduced from above in the drawing through an appropriate light guide, and is divided into two by a splitting optical system 50 such as a half mirror. One of the divided laser beams 12a is repeatedly reflected by the mirrors 51a, 52a, and 53a, and is condensed and irradiated onto the processing point p by the condensing optical system 11a such as a lens. On the other hand, one of the divided laser beams 12b is repeatedly reflected by mirrors 54, 51b, 52b, and 53b, and is condensed and irradiated on the same processing point p by a condensing optical system 11b such as a lens.

  Next, the mechanism of the rotating device 20 will be described. The laser processing apparatus has an xyz table (not shown) on which a workpiece W workpiece such as a grindstone is mounted, and performs processing by three-axis driving. A hollow housing 40 is attached along the z-axis of the laser processing apparatus, and the laser beam 12 travels downward in the z-axis through the inside, and is divided into two laser beams 12a and 12b through the optical path, The laser beams 12a and 12b intersect at the processing point p.

  A main housing 42 is rotatably attached to the hollow housing 40 via a bearing 41. The split optical system 50 and the mirror 54 are fixed inside the main housing 42, and the mirror 51a is fixed with respect to the laser light 12a and the mirror 51b is fixed with respect to the laser light 12b.

  A sub housing 44a is rotatably attached to the main housing 42 via a bearing 43a. Inside the sub-housing 44a, mirrors 52a and 53a and a condensing optical system 11a related to the laser beam 12a are fixed.

  Further, a sub housing 44b is rotatably attached to the main housing 42 via a bearing 43b. Inside the sub-housing 44b, mirrors 52b and 53b and a condensing optical system 11b related to the laser light 12b are fixed.

  The sub housing 44a is rotationally driven by a rotation unit 60a configured by a motor 61a and gears 62a and 63a fixed to the main housing 42. The sub housing 44b is rotationally driven by a rotation unit 60b constituted by a motor 61b fixed to the main housing 42 and gears 62b and 63b.

  The rotary shafts 67a and 67b of the rotary units 60a and 60b are set at an angle of about 45 degrees with respect to the optical axis of the introduced laser beam 12. Further, the optical axes 57a and 57b of the condensing optical systems 11a and 11b of the divided laser beams 12a and 12b are set to about 45 degrees with respect to the rotation axes 67a and 67b of the rotation units 60a and 60b, respectively. Yes.

  When the rotating units 60a and 60b are rotated, the splitting optical system 50, the mirrors, and the condensing optical systems 11a and 11b are arranged so that the intersecting regions of the laser beams 12a and 12b do not move with respect to the processing point p. The position and orientation are fine-tuned. Accordingly, the rotation angle of each of the rotating units 60a and 60b causes the laser beam irradiation angle to rotate 90 degrees even in the direction directly above the processing point p (downward on the z axis as in the laser beam 12a in the figure). Irradiation is possible even from (as in the figure, laser beam 12b).

  In such a configuration, as described in the above laser processing method, regarding the energy of the laser beam irradiated to the processing point p, the material at the processing point p is not melted by only one laser beam, but the two laser beams are used. Set to melt. With this setting, the material is melted or evaporated only when the two laser beams 12a and 12b intersect at the processing point p, and can be removed by the laser.

  Since the laser crossing region is usually a region having a beam waist at the focal point (diameter of several μm), the material to be removed has the same volume. At this time, it is preferable to set the optical axis so that the two laser beams intersect at about 90 degrees. When the beam characteristic of the laser oscillator is the Gaussian mode, the intensity distribution in the laser intersecting region becomes almost spherical and is removed. The portion has a concave shape corresponding to the spherical shape.

  With respect to the irradiation angle of the laser beam, as shown in FIG. 3 (schematically as shown in FIG. 1), one laser beam 12a is substantially from the normal direction of the surface near the processing point p, and the other laser beam 12b is Irradiation from the substantially tangential direction of the surface near the processing point p may be performed. However, in order to avoid blocking of the laser beam by an obstacle, if both the laser beams 12a and 12b are irradiated obliquely from above as shown in FIG. The possibility of this can be reduced, and concave processing becomes possible.

  Next, an example of an actual processing procedure will be described. In order to perform three-dimensional removal processing by laser irradiation, it is necessary to relatively move the workpiece W so that the processing point p has a desired shape while irradiating laser light.

  FIG. 4 shows an example in which the processed shape is a flat L-shaped groove with a semicircular cross section. In a conventional laser cutting process, in order to obtain a stable processing result, the irradiation angle is controlled so that the laser beam is always irradiated from the normal direction to the processing point. Also in the laser processing according to the present invention, in order to perform stable processing, it is preferable to perform processing while holding two laser beams at a constant angle with respect to two moving directions 69c and 69d orthogonal to each other. For this purpose, it is necessary to control the irradiation direction mainly by rotation of the sub-housings 44a and 44b by the rotation units 60a and 60b, and to further rotate the main housing 42.

  In FIG. 4, the irradiation angle of the laser beam with respect to the traveling direction can be kept constant by rotating the main housing 42 by 90 degrees at the point q where the moving direction changes.

  As shown in FIG. 3, a motor 64 is fixed to the hollow housing 40 and constitutes a main rotation unit 68 together with gears 65 and 66. The main housing 42 is rotationally driven with respect to the hollow housing 40 by the rotation operation of the main rotation unit 68. As a result, the sub-housings 44a and 44b attached to the main housing 42 also rotate around the optical axis of the laser light 12, and the laser irradiation angle with respect to the traveling direction can be controlled. As described above, the rotation units 60a, 60b, and 68 are driven to rotate so as to maintain a certain angle with respect to the moving direction (travel vector) of the machining point. In this way, in addition to driving the xyz table of the laser processing apparatus, the rotation control by the rotation units 60a, 60b, 68 makes it possible to always keep the irradiation angles of the laser beams 12a, 12b constant. As a result, the machining shape that is the locus of the machining point is stabilized.

Embodiment 3 FIG.
In the present embodiment, the polarization directions of a plurality of laser beams will be described. Normally, in thermal processing using laser light, molecules (atoms) are excited (lattice vibration) by an electric field of light. This is heat generation due to light absorption. In each of the above-described embodiments, the two laser beams 12a and 12b are overlapped at the same processing point p. Therefore, by matching the polarization directions of the laser beams 12a and 12b, that is, the vibration directions, molecules and atoms can be aligned. The excitation directions match, and the conversion efficiency from light energy to heat, that is, the light absorption rate can be improved. As a result, laser processing can be performed at higher speed.

Embodiment 4 FIG.
In this embodiment, wavelengths of a plurality of laser beams will be described. In each of the above-described embodiments, the thermal energy of laser light (the kinetic / vibrational energy of atoms and molecules) is used. In other words, the laser used mainly is an infrared laser (CO ₂ gas laser, YAG laser, etc.) with high conversion efficiency to heat, but is not limited to this, and quantum chemical energy (atom or molecule excited state) Energy) may be used. In other words, it is possible to activate the atoms and molecules of the material by the multi-photon absorption of the laser beam to make it easy to react, or to ionize and vaporize it by combining it with the atmospheric molecules, and perform laser removal processing It is.

  A laser capable of activating or exciting atoms and molecules is more effective as the wavelength is shorter, such as an ultraviolet laser (excimer laser, nitrogen laser, etc.). This is because the photon energy is inversely proportional to the wavelength of the light. In general, the beam waist existing in the processing region can be set smaller as the wavelength is shorter. Moreover, since the excitation efficiency is proportional to the square or the third power of the light intensity, a region narrower than the beam waist is excited and removed. Therefore, it is possible to remove a three-dimensional shape that is finer than that using thermal energy.

  Furthermore, the wavelengths of the plurality of laser beams do not have to be the same, and the material of the workpiece and the required processing result (surface roughness, surface crystal state, thickness of the coating layer or work-affected layer, and It is preferable to select a plurality of wavelengths according to the material. This makes it possible to perform removal processing that combines various light-substance interaction phenomena, such as removal processing using both thermal energy and quantum chemical energy, and stepwise multiphoton absorption by photons having different wavelengths.

Embodiment 5. FIG.
In the present embodiment, laser light transmission means will be described. In the transmission of laser light, a mirror may be used as in each of the above-described embodiments, but a plurality of laser lights may be transmitted using optical fibers 70a and 70b as shown in FIG. When an optical fiber is used, it is not necessary to adjust the optical axis of a mirror or the like, and the apparatus configuration and adjustment are further simplified.

  In each of the above-described embodiments, an example in which two laser beams are used has been described. However, three or more laser beams may be used.

  In each of the above-described embodiments, an example in which laser light from one laser oscillator is split into two laser lights by a splitting optical system such as a half mirror has been described. These laser oscillators may be provided individually. In addition, it is preferable that the wavelength and / or polarization state of the plurality of laser beams focused on the processing point is appropriately selected depending on the required processing result and the material to be processed.

  In each of the above-described embodiments, the condensing optical systems 11a and 11b are driven to rotate around the z-axis simultaneously by the rotation unit 68. However, a separate rotation unit is provided for each of the condensing optical systems 11a and 11b. Thus, the condensing optical systems 11a and 11 may be independently driven to rotate around the z axis. In this case, the apparatus is considerably complicated, but the irradiation direction by the respective condensing optical systems 11a and 11b can be arbitrarily set, and the selection range of the processing conditions is expanded.

  Further, if the workpiece is transparent to the laser beam, internal processing is also possible. For example, if the light intensity is set so as to generate minute cracks, or the wavelength or the like is set so that the color, crystal state, or the like changes, a three-dimensional pattern can be formed inside the transparent body. This can provide a new expression method for art objects such as figurines.

  Further, the present invention can be applied to a three-dimensional storage device, and a large capacity storage can be expected. Furthermore, if a three-dimensional waveguide or the like is formed inside, an optical circuit that is a replacement of an electronic circuit can be realized, and realization of a computing device that requires faster operation can be expected.

It is a schematic perspective view which shows Embodiment 1 of this invention. It is a schematic perspective view which shows Embodiment 1 of this invention. It is a schematic sectional drawing which shows Embodiment 2 of this invention. It is a schematic perspective view which shows an example of the laser processing procedure of this invention. It is a schematic sectional drawing which shows Embodiment 5 of this invention. It is sectional drawing for demonstrating the conventional three-dimensional shape creation process. It is explanatory drawing which shows the irradiation state of the laser beam in the conventional laser processing method. It is explanatory drawing which shows the irradiation state of the laser beam in the conventional laser processing method.

Explanation of symbols

10a, 10b Laser light source, 11a, 11b Condensing optical system, 12, 12a, 12b Laser light, 20 Rotating device, 40 Hollow housing, 42 Main housing, 44a, 44b Sub housing, 50 Division optical system, 57a, 57b Optical axis 60a, 60b, 68 rotating unit, 67a, 67b rotating shaft, 70a, 70b optical fiber, p processing point, W workpiece.

Claims (7)

Arranging the optical axes of the laser beams so that a plurality of laser beams intersect at the same processing point of the workpiece;
And a step of processing by changing the irradiation angle of each laser beam with the processing point as a rotation fulcrum. A plurality of condensing optical systems for condensing a plurality of laser beams at the same processing point of the workpiece;
A laser processing apparatus, comprising: each focusing optical system; and a rotating device for rotating the optical axis of each focusing optical system with the processing point as a rotation fulcrum. The rotation axis of the rotating device is set to pass through the machining point,
3. The laser processing apparatus according to claim 2, wherein the optical axis of the condensing optical system intersects the rotation axis of the rotation device at a predetermined angle. The rotating device includes a first housing for introducing laser light;
A second housing that is rotatably supported with respect to the first housing and is equipped with a splitting optical system that splits the laser light into first and second laser light;
A third housing mounted with a first condensing optical system that is rotatably supported with respect to the second housing and condenses the divided first laser light;
4. The laser processing according to claim 3, further comprising a fourth housing that is rotatably supported with respect to the second housing and includes a second condensing optical system that condenses the divided second laser light. apparatus.   The laser processing apparatus according to claim 2, wherein the polarization directions of the plurality of laser beams condensed at the same processing point coincide with each other.   The laser processing apparatus according to claim 2, wherein the plurality of laser beams have two or more wavelengths. The laser processing apparatus according to claim 2, further comprising a plurality of optical fibers for transmitting a plurality of laser beams.

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