JP2017217677A - Laser processing method and laser processing apparatus - Google Patents

Abstract

The object of the present invention is to remove reattachment of molten matter and vaporized matter, which is a problem when microfabrication is performed using a single-mode fiber laser, and to control the shape of the processing surface newly formed by laser irradiation. To provide a laser processing method and a laser processing apparatus for achieving high-quality laser processing. A pulsed laser beam that revolves around the optical axis of a laser beam emitted from a single-mode fiber laser oscillator having laser oscillation means that selects an oscillation mode according to the thermophysical properties of an object to be processed. 12 is superimposed on a part of the laser beam 11 and enters the condensing lens 8 , and the pulsed laser beam 12 having an incident angle θ is focused on the object 9 by condensing the laser beam 11 and the pulsed laser beam 12 . While changing the incident direction with respect to the processed surface formed in the above, by incident on the processed surface at an incident angle θ of 1.2 ° or less according to the thermophysical property, the shape change of the processed surface and the processed surface Adds post-processing. [Selection drawing] Fig. 2

Description

  The present invention relates to a technical field in which fine processing is performed using a single mode fiber laser, and is intended to improve the quality of laser processing by superimposing two laser beams having different wavelengths.

  The fiber laser is a laser oscillator that performs laser oscillation using an optical fiber having a double clad structure in which a rare earth element is attached to a core. Currently, most fiber lasers for laser processing use optical fibers with a double clad structure with ytterbium added to the core, and high-intensity laser oscillation is achieved by injecting high-brightness semiconductor laser light into the optical fiber. Yes. Further, by producing a diffraction grating on the end face of the optical fiber, it becomes possible to reflect only a selected wavelength, and it is not necessary to use a mirror to form a resonator. In this way, the fiber laser has a structure that is not easily affected by disturbances such as vibration, and there is no need to adjust the optical axis inside the oscillator.

  Further, since the optical fiber can control the propagation mode of the laser beam, the laser beam with excellent beam quality can be easily used by using the fiber laser. When the core diameter of the fiber is sufficiently small, the propagation mode of the optical fiber is limited, so that the energy intensity distribution of the obtained laser light is very close to the Gaussian distribution. A laser oscillator that performs laser oscillation with an optical fiber that transmits only one spatial mode is referred to as a single mode fiber laser. Single-mode fiber lasers are extremely excellent in light condensing performance, and can easily obtain a small condensing diameter of 50 μm or less, and the energy intensity distribution is a Gaussian distribution. A large value.

  In general laser cutting, it is desirable to select an appropriate laser wavelength according to the light absorption characteristics of the material to be processed. For example, since the wavelength of a carbon dioxide laser is in the far-infrared region, aluminum, copper, etc. have a low absorption rate and are not suitable for processing. The wavelength of a general fiber laser used for laser processing is in the near-infrared region, and although the absorption rate of aluminum, copper, etc. is small, the energy density at the center of the focused spot is very large as described above, so the laser beam The material melts in the central region irradiated with, and processing progresses due to an increase in the absorption rate accompanying the phase change. Thus, the single mode fiber laser can be applied to a wide range of materials and has become a necessary tool in the industrial field.

  Single-mode fiber lasers are used in a wide range of fields such as drilling, cutting, and welding because of their excellent beam quality. In the case of cutting, processing with a small cutting width and a high aspect ratio can be realized. On the other hand, for example, when the object to be processed is a metal, the cutting width is small and melted when performing laser cutting processing with a high aspect ratio. Removal of the metal becomes a problem. Normally, molten metal is removed by an assist gas ejected from a nozzle installed coaxially with the laser beam. However, if the cutting width is very small even if the assist gas is ejected at a high pressure, the pressure loss is large and sufficient removal effect is obtained. May not be obtained. In addition, when the CFRP is subjected to laser cutting processing, re-adhesion of a melt or an evaporant generated by laser irradiation is often observed on the cut surface. In addition, as another problem, a material having a high melting point and high thermal conductivity such as copper deteriorates the processing performance. There is a problem similar to the above-mentioned cutting in the hole processing. In the case of welding, deep penetration by keyhole welding can be realized. However, since the welding strength varies depending on the cross-sectional shape of the penetration portion, control of the cross-sectional shape is a problem.

  The present invention has been made in consideration of such problems, and controls the shape of a new processing surface formed by laser irradiation by superimposing laser light having a wavelength different from that of a single mode fiber laser. In addition, high-quality laser microfabrication is realized for a wide range of materials by removing melts and vapors generated during laser irradiation and improving processing performance in materials with a high melting point and high thermal conductivity. For the purpose.

As shown in Patent Document 1, a technical method for performing processing by irradiating lasers having different wavelengths to the same portion has been known for a long time.
In Patent Document 2, in laser drilling, two lasers having different wavelengths and pulse widths are used, and the energy of the laser beam having a shorter wavelength is increased so that the energy intensity is increased at the outer portion of the other beam spot. A technique characterized by superposing the intensity distribution after shaping it has been reported. In general, a beam shaping optical system requires a large pulse energy, so a laser oscillator with a short wavelength is expensive. However, an expensive laser oscillator with a high pulse energy is required, and a beam shaping optical system is also required. Since it is expensive, the processing apparatus becomes very expensive.
Patent Document 3 aims at performing high-speed and high-quality processing on a composite material such as CFRP, and uses two laser beams of continuous light that oscillates continuously and pulsed light that oscillates pulsedly. A technique for focusing and rotating using a diffractive optical element or the like and using a metal mirror having an opening in the center has been reported. However, since it is superimposed by a mirror after condensing, the focal length of the condensing lens that can be used is limited in optical design, and the condensing diameter of the continuous light cannot be made 30 μm or less. In addition, regarding the application range of the incident angle, which is the angle between the optical axis of the pulsed light and the optical axis of the continuous light after passing through the condenser lens, the incident light can not be incident on the inside of the opening. A range close to 0 ° is not applicable. As described above, since the region where the continuous light and the pulsed light are superimposed on the workpiece is limited to the vicinity of the surface of the workpiece, it is difficult to control the shape of the workpiece.

JP 62-289390 A JP 2007-29952 A JP2015-47638

  The present invention efficiently removes the re-adhered matter of melt and vapor generated by laser irradiation, which is a problem when performing laser processing with a small spot diameter using a single mode fiber laser. An object of the present invention is to provide a laser processing method and a laser processing apparatus for realizing high-quality laser micromachining by controlling the shape of the processed surface formed on the surface.

A single-mode fiber laser processing method having a laser oscillation means that selects continuous oscillation or pulse oscillation according to the thermal conductivity and the thermal physical property of the melting point of the object to be processed by laser processing. A pulse having a center wavelength revolving around the optical axis of laser light whose center wavelength is emitted from the fiber laser oscillator in the near infrared region is a visible light region, a pulse width of 1 nanosecond or less, and a pulse energy of 40 μJ or more. After the laser beam is focused on the surface of the workpiece, the single mode fiber laser beam and a part of the pulse laser beam are superimposed on each other and enter the condenser lens. The single-mode fiber laser beam and the pulsed laser beam are added with the revolving motion maintained at a radius. The pulse laser beam having an incident angle obtained from the arc tangent of the value obtained by dividing the revolution radius by the focal length of the condenser lens with the optical axis as a reference by condensing on the same surface of the object surface. The incident angle is 1.2 ° or less according to the thermophysical properties while changing the incident direction with respect to the machining surface newly formed on the workpiece by condensing the single mode fiber laser beam and the pulse laser beam. A laser processing method characterized by changing the shape of the processed surface and applying post-processing to the processed surface by being incident on the processed surface within a range.

Further, the processing object is a metal material having a thermal conductivity of 16 to 398 W / (m · K) or a carbon fiber composite material composed of carbon fiber and a resin.

Also, a processing apparatus using a single mode fiber laser, the single mode fiber laser oscillator that continuously or pulse oscillates laser light having a center wavelength in the near infrared region, and a center wavelength in the visible light region and 1 nanosecond or less. A pulse laser oscillator that oscillates a pulse laser beam having a pulse width of 40 μJ or more, a condensing lens that has been subjected to chromatic aberration correction and spherical aberration correction for the laser beam and the pulse laser beam, and the pulse laser beam Beam rotating means for revolving at an arbitrary revolution radius with an arbitrary axis as a revolution axis, and a dichroic that reflects the laser light and transmits the pulsed laser light so that the revolution axis coincides with the optical axis of the laser light A mirror, a collimating lens for collimating the laser beam into parallel light, and a front Divergence angle control means for controlling the divergence angle of the pulse laser beam so that the focal position of the pulse laser beam with respect to the optical axis direction coincides with the focal position of the laser beam, and irradiation of the laser beam and the pulse laser beam A high-speed flow introducing means for removing the generated melt or vapor using a high-speed flow of gas, and an incident angle obtained from an arctangent of a value obtained by dividing the revolution radius by the focal length of the condenser lens By setting the angle to be 1.2 ° or less, the shape of the processing surface newly formed on the object to be processed by the condensing of the single mode fiber laser light and the pulse laser light is changed, and the processing A post-processing process is given to the surface.

  In the present invention, the taper angle can be changed by controlling the shape of the processed surface, and the incident angle is set in a range of 0.5 to 0.7 ° on the basis of 0.6 °. A machined surface near a taper angle of 0 ° is obtained. Moreover, it is possible to remove the melted product or the evaporated product of the processing object generated by laser irradiation in laser processing.

Since no special optical element is required, the apparatus can be simply configured. By revolving the pulse laser beam, the overlap of the pulse laser beam can be reduced, and the thermal influence on the processed cross-sectional area can be reduced.

By performing the irradiation of the pulse laser in advance of the irradiation of the single mode laser light, reflection at the time of irradiation of the single mode laser light can be reduced, so that the laser light is perpendicular to a highly reflective material having high thermal conductivity. It is possible to prevent the single mode fiber laser oscillator from being damaged by the reflected light when incident. For materials having a high melting point and high thermal conductivity, the processing performance can be improved by setting the incident angle to 0.5 ° or less.

By providing the above-described configuration, the present invention can fully utilize the characteristics of a single mode fiber laser for laser processing. The processing width during laser processing is 50 μm or less and the aspect ratio is 20 or more. Processing can be realized, and high-quality laser micromachining can be realized for a wide range of materials.

It is a schematic block diagram regarding the example of an apparatus which implements the laser processing apparatus which concerns on this invention. It is a perspective view regarding the condensing optical system which implements the laser processing apparatus which concerns on this invention. It is a cutting | disconnection result of the stainless steel plate by this invention in Example 1. FIG. 2 is a cut surface of a stainless steel plate under an incident angle of 0.29 ° according to the present invention in Example 1. FIG. 3 is a cut surface of a stainless steel plate under a condition of an incident angle of 0.58 ° according to the present invention in Example 1. FIG. 2 is a cut surface of a stainless steel plate under a condition of an incident angle of 1.2 ° according to the present invention in Example 1. FIG. FIG. 2 is a cut surface of a stainless steel plate according to Example 1 by single-mode fiber laser irradiation alone. It is the result which showed the relationship between the incident angle and taper angle in Example 1. FIG. It is a cutting result of the copper plate by this invention in Example 2. FIG. 6 is a SEM image of a laser cut surface by single mode fiber laser single irradiation in Example 3. FIG. 6 is a SEM image of a laser cut surface according to the present invention in Example 3. FIG. 6 is a high-magnification SEM image of a laser cut surface obtained by single-mode fiber laser single irradiation in Example 3. FIG. 6 is a high-magnification SEM image of a laser cut surface according to the present invention in Example 3. FIG.

  Embodiments according to the present invention will be described below. Since the following apparatus configuration is a specific example of the present invention, various technical limitations are made. However, the present invention is not limited to these forms unless specifically described in the following description. It is not limited to. In addition, various modifications of the present invention can be considered for the following apparatus configuration as long as it is a person in the technical field, but they are all included in the technical scope of the present invention.

  An example of a schematic configuration of the laser processing apparatus 100 according to the present invention is shown in FIG. The laser processing apparatus 100 includes a laser oscillator 1, a laser oscillator 2, a collimating lens 3, a mirror 4, a dichroic mirror 5, a beam rotating means 6, a spread angle control means 7, a condenser lens 8, and a processing target. It has at least an object 9, a control means 20, a high-speed flow introducing means 21, and a processing stage 22.

The laser oscillator 1 is a single mode fiber laser oscillator and has a laser wavelength in the near infrared region. The oscillation form of the laser oscillator 1 includes continuous oscillation and pulse oscillation, and can be selectively used according to the processing purpose. When reducing the thermal effect of the material, the laser oscillator 1 is preferably pulsed. Control of the output and oscillation timing of the laser oscillator 1 is performed by the control means 20. Here, the near-infrared region is a region where the center wavelength of the laser light is greater than 800 and not more than 1500 nm. The pulse width when the laser oscillator 1 is oscillated is preferably 1 microsecond or more. Diameter d in the case of condensing the laser beam 11 by the condensing lens 8, the core diameter at the fiber end face which is a focal length f and the focal length f _c and the laser irradiation surface of the laser oscillator 1 of the collimator lens 3 of the condenser lens 8 It is expressed by the following formula 1 using d _out .

  The laser oscillator 2 is a pulsed laser oscillator and has a laser wavelength in the visible light region. The pulse width of the laser oscillator 2 is desirably 1 nanosecond or less. Control of the output and oscillation timing of the laser oscillator 2 is performed by the control means 20. Here, the visible light region is a region where the center wavelength of the laser light is 380 nm or more and 800 nm or less. When the center wavelength of the laser oscillator 2 is close to near-infrared or close to ultraviolet, the dichroic mirror 5 used for superimposition is expensive. Therefore, the center wavelength is preferably 500 nm or more and 550 nm or less. The polarization direction of the laser beam 12 is preferably circular polarization, but linear polarization can also be applied, and the polarization direction is not limited. The duty ratio Dr, which is a guideline indicating the thermal effect when irradiating the workpiece with pulse oscillation, is represented by the product of the pulse width τ [s] of the laser oscillator 2 and the repetition frequency Fr [Hz]. The peak output Pp [W] is calculated by dividing the pulse energy Pe [J] per pulse of the laser oscillator 2 by the pulse width τ [s].

  The collimating lens 3 collimates the laser beam 11 emitted and diffused from the fiber end of the laser oscillator 1 into a parallel light beam.

  The mirror 4 reflects the laser beam 11 emitted from the laser oscillator 1 and the laser beam 12 emitted from the laser oscillator 2 at an arbitrary angle.

  The dichroic mirror 5 is characterized by reflecting laser light in the near infrared region and transmitting laser light in the visible light region.

  The rotating means 6 is characterized by causing the laser beam 12 to revolve with an arbitrary revolution diameter. A method for realizing the revolving motion is not particularly limited, but here, a method using a dove prism, which is the simplest method, will be described. It is a well-known fact that when the Dove prism rotates about its longitudinal direction, the image obtained from the exit surface rotates at a rotational speed that is twice the rotation angle, and the laser beam 12 is incident on the Dove prism. The laser beam 12 that has passed through the Dove prism is twice the rotation speed of the Dove prism when the Dove prism is displaced at an arbitrary distance from the rotation axis of the Dove prism and is incident on the Dove prism. Revolve at a speed of. It is desirable to rotate the Dove prism so that the rotation axis and the optical axis of the laser beam 12 immediately before entering the Dove prism are parallel, and the rotation axis passes through the center of the incident surface. The revolution diameter of the laser beam 12 that has passed through the Dove prism is determined by the amount of displacement from the rotation axis on the incident surface. The amount of displacement can be controlled by displacing the mirror 4c in a direction perpendicular to the rotation axis, and the rotating means 6 includes a mechanism for controlling the displacement of the mirror 4c. The optical axis and the revolution axis of the laser beam 12 in the revolving state are parallel to the optical axis of the laser beam 12 immediately before entering the Dove prism. The rotation means 6 is controlled by the control means 20. Here, the incident surface represents a surface on which laser light is incident in the target optical element.

  The divergence angle control means 7 is configured to arbitrarily control the beam diameter and the divergence angle of the laser light 12 by configuring the two optical elements as a Galileo or Keplerian parallel optical system.

  The condensing lens 8 condenses the laser beam 11 and the laser beam 12 on the surface of the workpiece 9 and corrects spherical aberration and chromatic aberration with respect to the wavelengths of the laser beam 11 and the laser beam 12. Is desirable. The condensing diameter of the laser beam 12 is determined depending on the beam diameter and the divergence angle immediately before entering the condensing lens 8.

  The control means 20 includes a control mechanism that performs control related to the laser oscillator, control related to revolution of the laser beam, control related to the processing stage, and control related to the flow of the high-speed gas.

  The high-speed flow introducing means 21 forms a flow field having a Mach number larger than 0.2, which is a value obtained by dividing the gas velocity in the vicinity of the laser irradiation portion by the sound speed in a stationary and stationary state. It is possible to pressurize the gas and blow a high-pressure gas onto the laser irradiation unit, or decompress the gas and suck the laser irradiation unit. The high-speed flow introducing means 21 is accompanied by a transmission window that transmits the laser beam 11 and the laser beam 12. Gases used in the high-speed flow introducing means 21 are compressed air, nitrogen, and argon, which are properly used depending on the object to be processed. The high-speed flow introducing means 21 is controlled by the control means 20. The high-speed flow introducing means 21 is installed between the condenser lens 8 and the workpiece 9 in a state of being integrated with the condenser lens 8, and the high-speed flow introducing means 21 and the workpiece to be processed in the optical axis direction of the laser beam 11. The distance between 9 is preferably controlled by the machining stage 22 so as to keep an arbitrary distance.

  The processing stage 22 includes a holding mechanism and a moving mechanism for the workpiece 9, and the moving mechanism includes, for example, three orthogonal moving axes and is linearly arranged at an arbitrary speed on the moving axis. The workpiece is moved to the position. The number of movement axes of the processing stage 22 is not limited. The processing stage 22 is controlled by the control means 20. The object to be held and moved by the processing stage 22 can be used as the condenser lens 8, and the object to be held and moved can be both the workpiece 9 and the condenser lens 8. When the surface of the workpiece 9 is uneven or curved, the measurement means for measuring the distance between the condenser lens 8 and the workpiece 9 and the processing stage 22 can be used together to process the unevenness or curved surface. It becomes possible. In the present invention, the focal position of the laser beam 11 and the laser beam 12 can be moved simultaneously by the movement of the condenser lens 8 in the optical axis direction, so that the laser processing head can be miniaturized and the three-dimensional processing can be performed. Easy to apply.

The laser beam 11 emitted from the laser oscillator 1 is collimated by the collimating lens 3 and is reflected by the mirror 4a and the dichroic mirror 5 and enters the condenser lens 8 in a parallel light state. It is desirable that the optical axis of the laser beam 11 immediately before entering the condenser lens 8 coincides with the symmetry axis of the condenser lens 8. Here, the symmetry axis represents a reference axis in which the object is line symmetric. In FIG. 1, the straight line representing the laser beam 11 is a light beam representing the optical axis of the laser beam 11, and the laser beam 11 is represented by a thick line for convenience in FIG. 1, but the thickness of the beam in FIG. Is independent of the beam diameter. Here, the optical axis is a representative light beam representing laser light, and represents a straight line connecting the centers of the laser light.

  The laser beam 12 emitted from the laser oscillator 2 is reflected by the mirrors 4 b and 4 c and enters the rotating means 6, and a revolving motion is given by the rotating means 6. Thereafter, the laser beam 12 passes through the divergence angle control means 7 and the dichroic mirror 5 in order and enters the condenser lens 8 with revolving motion. The laser beam 11 and the laser beam 12 are superimposed by the dichroic mirror 5. When passing through the dichroic mirror 5, the laser beam 12 is accompanied by a revolving motion, and the revolution axis of the laser beam 12 coincides with the optical axis of the laser beam 11 after being reflected by the dichroic mirror 5. In FIG. 1, the straight line representing the laser beam 12 is a light beam that represents the optical axis of the laser beam 12, and the laser beam 12 involves a revolving motion after passing through the rotating means 6. Represented by straight and dotted lines. The straight lines representing the laser light 11 and the laser light 12 in FIG. 1 do not overlap because they indicate the optical axis, but actually the laser light 11 and a part of the laser light 12 overlap. 1 is used for convenience to express that the laser beam 12 revolves. The thickness of the light beam in FIG. 1 is independent of the beam diameter of the laser light.

FIG. 2 shows the locus of the laser beam 11 and the laser beam 12 before and after the incidence of the condenser lens 8. The laser beam 11 and the laser beam 12 superimposed by the dichroic mirror 5 enter the condensing lens 8 and are respectively collected on the surface of the workpiece 9. During this time, the laser beam 12 maintains a revolving motion, The laser beam 11 and the laser beam 12 are kept superimposed. The optical axis of the laser beam 11 passes through the center of the condenser lens 8, but the optical axis of the laser beam 12 does not pass through the center of the condenser lens 8, so that the optical axis of the laser beam 12 passes through the condenser lens 8. As a result, the optical axis of the laser beam 12 has an arbitrary incident angle θ with respect to the optical axis of the laser beam 11. As shown in FIG. 2, when the laser beam 11 is perpendicularly incident on the surface of the workpiece 9, the laser beam 12 revolves on the workpiece 9 while revolving in a state inclined with respect to the optical axis of the laser beam 11. Incident. Thus, the optical axis of the laser beam 12 after passing through the condenser lens 8 has a pseudo precession. Here, the pseudo precession movement represents a precession movement that does not involve rotation. The laser beam 12 is incident on the processing surface newly formed by removing the processing object in the irradiation portion by the irradiation of the laser beam 11 with the pseudo precession, so that the laser beam is applied to the processing surface. 12 is irradiated. A melted product or an evaporated product of the workpiece 9 generated by the irradiation of the laser beam 11 adheres to the processed surface. Although the laser beam 12 has a small amount of energy, the pulse width is short and the peak output is large, and the melt and the vaporized material have a small processing threshold. Therefore, the laser beam 12 is processed near the processing wall 9. Remove the melt and re-deposited evaporates. Although the surface of the workpiece 9 in FIG. 2 is a plane, the drawing is an embodiment and does not limit the present invention, and the surface shape of the workpiece 9 is not limited.

The incident angle θ [deg] is obtained by using the revolution radius Rm of the laser beam 12 and the focal length f of the condenser lens 8.
It is represented by In order to perform the laser processing efficiently, it is necessary that the laser light 11 and a part of the laser light 12 are overlapped before the condenser lens 8 is incident as shown in FIG. For this reason, the revolution radius Rm of the laser beam 12 is preferably smaller than the beam radius Rb of the laser beam 11.

  When the workpiece 9 is made of a material having high thermal conductivity such as copper, there is a risk that the laser oscillator 1 may be damaged by reflected light when the laser beam 11 is irradiated onto the workpiece 9. For this reason, since the wavelength is short and the peak output is large, it is desirable to irradiate the laser beam 12 having a higher absorption rate to the material first and then irradiate the laser beam 12 thereafter. The reflected light is reduced by forming a processing mark by irradiation with the laser beam 12. The order of irradiation is later for the laser beam 11, but the laser beam 11 has a larger energy amount than the laser beam 12, and the processing speed in the optical axis direction of the laser beam 11 exerted on the workpiece 9 is as follows. Since the laser beam 11 is faster than the laser beam 12, the processing in the present invention is performed mainly by the laser beam 11.

When heated by laser irradiation, the heating temperature changes depending on the thermal conductivity of the workpiece 9, and the heating is maximized on the surface in the steady state of the material heated by the Gaussian beam with the beam radius d and the beam center intensity I _0. It is known that the temperature T is given by the following mathematical formula 3 (reference: laser processing, Yutaka Kurata, Nikkei Technical Library, published on March 10, 1990, p. 25). Here, ε is the absorption rate of laser light in the material, and K is the thermal conductivity of the material. Although the heating temperature varies depending on the absorption rate of the laser beam, since the laser beam 12 having a large peak output is irradiated in advance in the present invention as described above, the material dependence on the absorption rate can be relaxed. When the pulse width of the laser beam 12 is 100 picoseconds or more, a thermal effect is exerted, and a melt layer is formed in the laser irradiation portion, so that the absorptance can be increased. In actual laser processing, laser irradiation is often completed before the heating temperature reaches a steady state, so it becomes unsteady heat conduction, and it is necessary to consider the thermal diffusivity of the material. In the present invention, the heating temperature is estimated from the magnitude of thermal conductivity.

When the heating temperature reaches the melting point, the material melts and a melt is produced. As the temperature difference between the heating temperature and the melting point is larger, a larger amount of the melt is generated, so that the amount of the melt generated by the melting point can be estimated. The thermal conductivity and melting point of the workpiece 9 are expressed as thermal properties. Thus, the amount of the melt produced by laser irradiation can be estimated from the thermophysical properties, and the processing speed can be estimated from the amount of melt produced. For example, copper has a thermal conductivity of 398 [W / (m · K)] and a melting point of 1085 ° C., a thermal conductivity of about 16 [W / (m · K)] and a melting point of about 1400 ° C. Compared with stainless steel (SUS304), the thermal conductivity of copper is more than 24 times that of stainless steel. Therefore, the heating temperature is significantly lower than that of stainless steel, and the melting point is relatively high. The processing speed is estimated to be slow. Since we have clarified that the present invention can be applied to copper and stainless steel, it is not possible to process a metal material having a thermal conductivity of 16 to 398 [W / (m · K)]. The scope of the invention. Since the metal material has free electrons, laser processing except for the ultrashort pulse laser beam is performed by a thermal action. The application range of the pulse width of the laser oscillator 1 in the present invention is 1 microsecond or more.

  The laser oscillator 1 can perform continuous oscillation or pulse oscillation, and it is necessary to select an appropriate oscillation mode according to the processing purpose, the material of the processing object 9 and the thermophysical properties. For example, when laser cutting a metal material, since copper is a material having a high melting point and high thermal conductivity, pulse oscillation with a high peak output is desirable. Conversely, stainless steel is a material with low thermal conductivity, so a lot of melt is generated by laser irradiation, and when the assist gas is injected by pulse oscillation, the melt scatters in all directions and melts when the cutting width is small. The reattachment of the object becomes remarkable, and the cutting property deteriorates. For this reason, it is desirable to oscillate continuously in the case of laser cutting of stainless steel. In the case of a composite material such as CFRP, it is composed of a material having a melting point and a thermal conductivity that are greatly different. However, since the heat-resistant temperature of the resin used as a component is about 200 ° C., Pulse oscillation with less influence is desirable.

  Since the processing speed of the present invention changes according to the incident angle, it is desirable to change the incident angle according to the thermal characteristics of the workpiece 9. Since a material having a high melting point and high thermal conductivity such as copper has a low processing speed, the processing speed can be increased by reducing the incident angle. This is because the processing progresses more efficiently when the region where the laser beam 11 and the laser beam 12 overlap is larger in the region irradiated with the laser. Since the laser beam 12 has a large peak output, it can be locally processed even in a material having high thermal conductivity.

  In addition, the taper angle can be changed depending on the size of the incident angle. When a machined surface having a taper angle of about 0 ° is desired, the taper angle can be changed from 0.5 ° based on the incident angle of 0.6 °. It is desirable to set in the range of 0.7 °. Here, the taper angle is an angle based on the optical axis in a straight line obtained by linearly approximating a line where the processed surface and the surface having the optical axis of the laser beam 11 intersect. For example, when the laser beam 11 is perpendicularly incident on the surface of the workpiece 9 and the processed surface is formed perpendicular to the surface, the taper angle becomes 0 °. Regarding the positive and negative of the taper angle, the case where the length of the perpendicular with respect to the optical axis of the straight line becomes shorter as it advances in the laser beam irradiation direction of the optical axis is positive, and the case where it becomes longer is negative. In the case of drilling, the taper angle becomes negative when the hole diameter on the back surface is larger than the hole diameter on the surface irradiated with the laser beam.

Since the laser beam 12 has a short pulse width, the thermal effect on the object to be processed is small, and by making the pulse width of the laser beam 12 100 picoseconds or less, the thermal effect due to the irradiation of the laser beam 12 can be reduced as much as possible. Although the melt and the evaporate are evaporated by the irradiation of the laser beam 12, it is desirable to use the assist gas spraying or the gas suction by the suction device in order to quickly remove the evaporate. Here, the blowing of the assist gas or the suction by the suction device corresponds to the high-speed flow introducing means.

Since the influence of viscosity becomes prominent in the vicinity of the processing wall, it is difficult to completely remove the melt and reattachment in the vicinity of the processing wall by only a hydrodynamic approach such as spraying of assist gas. By using the invention, it is possible to efficiently remove the reattachment near the processing wall surface.

The structural example of the laser processing apparatus 100 and the processing example with respect to a stainless steel plate are shown below.
As the laser oscillator 1, a single mode fiber laser (YLR-150 / 1500-QCW manufactured by IPG) was used. The laser oscillator 1 can select and use continuous oscillation or pulse oscillation. The core diameter of the fiber laser at the emission end is 50 μm.

As the laser oscillator 2, a sub-nanosecond laser (HELIOS 532-3-50 manufactured by COHERENT) was used. The wavelength of the laser oscillator 1 is 1070 nm, the wavelength of the laser oscillator 2 is 532 nm, and the pulse width is 400 picoseconds under the condition that the repetition frequency is 16.6 kHz.

  The collimating lens 3 uses a collimating lens with a focal length of 100 mm, the condensing lens 8 uses an achromatic lens with a focal length of 49.4 mm, and the condensing diameter under this condition is 25 μm.

  The beam rotating means 6 includes a dove prism, a prism holder 61, and a motor 62. The dove prism is held by the prism holder 61 having a bearing so that it can rotate. The prism holder 61 and the motor Since the rotation shaft 62 is connected by a timing belt, the Dove prism rotates in synchronization with the rotation of the motor 62.

The divergence angle control means 7 uses a beam expander with a diopter correction function (LBED-3 manufactured by Sigma Koki Co., Ltd.) corresponding to a laser wavelength of 532 nm, and the condensing diameter of the laser light 12 accompanied with the revolving motion is on the surface of the workpiece 9. The spread angle of the laser beam 12 was adjusted so as to be minimized.

  As the workpiece 9, a stainless steel plate (SUS304) having a thickness of 0.5 mm was used. The aspect ratio, which is the ratio between the plate thickness and the focused diameter of the laser beam 11 under this condition, is 20.

The laser irradiation conditions in this embodiment are as follows: the laser oscillator 1 is 70 W for continuous oscillation, the laser oscillator 2 is 16.6 kHz pulse oscillation, the pulse energy of the laser oscillator 2 is 60 μJ, the peak output is 150 kW, and the duty ratio is 0. .00067%, the rotational speed of the motor of the beam rotating means 6 was 2500 RPM, and the incident angle of the laser beam 12 was set to 0.58 °. The processing stage 22 was scanned at a speed of 30 mm / min so as to cut out 3 mm × 3 mm, and compressed air was blown coaxially with the laser beam by the high-speed flow introducing means 21 during laser irradiation. The processing test was performed based on the laser irradiation conditions, and a comparison was made between a condition in which the laser beam 11 was irradiated alone and a condition in which the laser beam 11 and the laser beam 12 were superimposed.

Table 1 shows the processing results of this example. Table 1 shows the results of fixing the laser irradiation conditions and setting the assist gas pressure in three stages. When the assist gas pressure is increased to 0.4 MPa in the single irradiation of the laser beam 11, the melted material by the laser irradiation adheres to the cut surface and the complete cutting is not achieved. It was confirmed that cutting was possible at .3 and 0.4 MPa, and the melt could be removed by superimposed irradiation, and cutting was possible with a small assist gas pressure. The cut stainless steel plate is shown in FIG. The results shown in Table 1 were that the laser oscillator 1 was continuously irradiated, but the same processing was performed by changing to pulse irradiation, but it was not possible to cut completely by both single irradiation and superimposed irradiation of the laser beam 11. When the stainless steel plate was continuously irradiated with the laser beam 11, the melt was scattered almost obliquely backward, whereas when the pulse was irradiated, the melt was scattered in all directions, and no deviation was observed in the scattering direction. For this reason, even in the case of superimposed irradiation, if the melt is reattached to the region after irradiation with the laser beam 12, removal is difficult. This is probably because the stainless steel plate has a low thermal conductivity and thus scatters in a molten state and causes reattachment. As described above, it was found that continuous irradiation of the laser beam 11 is effective in cutting a metal material having low thermal conductivity in the present invention, and pulse irradiation is not suitable.

  Further, the stainless steel plate was cut as described above under three conditions of the incident angle of the laser beam 12 of 0.29 °, 0.58 °, and 1.2 °. The assist gas pressure was 0.4 MPa, the cutting scanning direction was one direction, and other conditions were the same as those described above. The cut surface at each incident angle and the cut surface by single irradiation of a single mode fiber laser are shown in FIGS. In this figure, the direction of laser irradiation is from the top to the bottom of the figure. As can be seen from these figures, it can be confirmed that the taper angle changes depending on the incident angle of the laser beam 12, and it was found that the taper angle is close to 0 when the incident angle is 0.58 °. Under the condition of an incident angle of 1.2 °, the taper angle is −11 °, which is a so-called reverse taper shape. FIG. 8 shows the result of showing the relationship between the incident angle and the taper angle based on the above result.

  Next, the example of a process with respect to a copper plate is shown. The laser processing apparatus 100 is the same as that of the first embodiment except for the items described below. The workpiece 9 was a copper plate having a thickness of 0.5 mm.

In this example, drilling and cutting were performed. As laser irradiation conditions, hole machining is performed under three conditions of incident angles of the laser beam 12 of 0.29 °, 0.58 °, and 1.2 °, and cutting processing is performed with the laser oscillator 1 having an average output of 79 W and a repetition frequency of 500 Hz. Pulse oscillation was performed, the incident angle was fixed at 0.29 °, and the processing stage 22 was scanned so as to cut out 1 mm × 1 mm at a processing speed of 6 mm / min. In both cases, the assist gas pressure was 0.4 MPa.

Table 2 shows the drilling results of this example. As can be seen from Table 2, under the condition of continuous irradiation of the laser beam 11 of 70 W, it was possible to drill a hole through only the condition where the incident angle was 0.29 ° by superimposing irradiation. A through hole could not be formed even by single irradiation with the laser beam 11. Thus, it was confirmed that the smaller incident angle was more suitable for through-hole processing.

Next, the cutting result of the present embodiment is shown in FIG. Unlike the first embodiment, the laser beam 11 can be cut by the pulse irradiation. As a result of observation at the time of laser cutting, the amount of molten material scattered is less when the copper plate is compared with the stainless steel plate, and copper has a high thermal conductivity, so the metal is cooled during the scattering and difficult to maintain the molten state For this reason, it is difficult to cause reattachment after scattering, and it is considered that cutting by pulse irradiation becomes possible.
Thus, it was found that pulsed irradiation of the laser beam 11 is effective in cutting a metal material having high thermal conductivity in the present invention.

  Next, processing examples for CFRP will be shown. The laser processing apparatus 100 is the same as that of the first embodiment except for the items described below. The processing object 9 was made of CFRP having a thickness of 2 mm. The CFRP uses a thermosetting resin.

In this embodiment, the laser irradiation conditions are as follows: the laser oscillator 1 is pulsed with an average output of 9.5 W and a repetition frequency of 50 Hz; the laser oscillator 2 is pulsed with 30 kHz; the pulse energy of the laser oscillator 2 is 48 μJ; The rotational speed of the motor of means 6 was set to 1000 RPM. The processing stage 22 was scanned in one axis direction at a processing speed of 60 mm / min. In the processing test, a comparison was made between a condition in which the laser beam 11 was irradiated alone and a condition in which the laser beam 11 and the laser beam 12 were superimposed at an incident angle of 1.2 °.

The processing results of this example are shown in FIGS. 10 and 11 show SEM images of the laser cut surface, respectively. In SEM observation, the processed sample was photographed under conditions without pretreatment such as metal deposition. FIG. 10 shows the result of the single irradiation of the laser beam 1, and FIG. 11 shows the result of the laser superimposed condition. Further, FIG. 12 is a result of enlarging the center part of FIG. 10, and FIG. 13 is a result of enlarging the center part of FIG. Since these SEM observation images are not subjected to metal vapor deposition or the like, the re-adhered material generated by laser processing has a large surface area, so that it is easy to charge up and appears white. As can be seen from the results of FIGS. 10 to 13, the result of the single irradiation of the laser beam 1 has a large image contrast and reattachment is observed, but in the superimposed result, the image contrast is low and the reattachment is suppressed. ing.

DESCRIPTION OF SYMBOLS 1 Single mode fiber laser oscillator 2 Pulse laser oscillator 3 Collimating lens 4a Mirror 4b Mirror 4c Mirror 5 Dichroic mirror 6 Rotating means 7 Divergence angle control means 8 Condensing lens 9 Processing object 11 Single mode fiber laser light 12 Pulse laser light 20 Control means 21 High-speed flow introducing means 22 Processing stage 61 Prism holder 62 Motor 100 Laser processing apparatus θ Incident angle
Rb Single mode fiber laser beam radius
Rm Revolution radius of pulsed laser light

Claims (3)

  A single-mode fiber laser processing method having a laser oscillation means that selects continuous oscillation or pulse oscillation according to the thermal conductivity and the thermal physical property of the melting point of the object to be processed by laser processing. A pulse having a center wavelength revolving around the optical axis of laser light whose center wavelength is emitted from the fiber laser oscillator in the near infrared region is a visible light region, a pulse width of 1 nanosecond or less, and a pulse energy of 40 μJ or more. After the laser beam is focused on the surface of the workpiece, the single mode fiber laser beam and a part of the pulse laser beam are superimposed on each other and enter the condenser lens. The single-mode fiber laser beam and the pulsed laser beam are added with the revolving motion maintained at a radius. The pulse laser beam having an incident angle obtained from the arc tangent of the value obtained by dividing the revolution radius by the focal length of the condenser lens with the optical axis as a reference by condensing on the same surface of the object surface. The incident angle is 1.2 ° or less according to the thermophysical properties while changing the incident direction with respect to the machining surface newly formed on the workpiece by condensing the single mode fiber laser beam and the pulse laser beam. A laser processing method characterized by changing the shape of the processed surface and applying post-processing to the processed surface by being incident on the processed surface within a range. 2. The laser according to claim 1, wherein the object to be processed is a metal material having a thermal conductivity of 16 to 398 W / (m · K) or a carbon fiber composite material composed of carbon fiber and resin. Processing method. A processing apparatus using a single mode fiber laser, the single mode fiber laser oscillator that continuously or pulse oscillates laser light having a center wavelength in the near infrared region, and a pulse having a center wavelength in the visible light region and 1 nanosecond or less. A pulse laser oscillator that oscillates a pulse laser beam having a width and a pulse energy of 40 μJ or more, a condensing lens that has been subjected to chromatic aberration correction and spherical aberration correction with respect to the laser beam and the pulse laser beam, and the pulse laser beam A beam rotating means for revolving at an arbitrary revolving radius with an axis as a revolving axis; a dichroic mirror that reflects the laser light and transmits the pulsed laser light so that the revolving axis coincides with the optical axis of the laser light; A collimating lens for collimating the laser beam into parallel light, and the optical axis Divergence angle control means for controlling the divergence angle of the pulse laser beam so that the focal position of the pulse laser beam with respect to the direction coincides with the focal position of the laser beam, and melting caused by irradiation of the laser beam and the pulse laser beam And at least a high-speed flow introducing means for removing substances and evaporates using a high-speed flow of gas, and an incident angle obtained from an arctangent of a value obtained by dividing the revolution radius by the focal length of the condenser lens is 1. By setting the angle to be 2 ° or less, the shape of the processing surface newly formed on the processing object is changed by condensing the single mode fiber laser light and the pulse laser light, and the processing surface A laser processing apparatus characterized by applying post-processing.