Laser processing machine and laser head

Abstract

This invention provides a novel laser processing machine that allows for easy control of excess heat on the processing surface and enables high-speed processing. [Solution] A laser processing machine that performs laser processing by irradiating a workpiece with laser light, comprising a laser light source that emits continuous wave laser light, and a pulse conversion unit that converts the continuous wave laser light into pulsed laser light and guides it to a laser output port, wherein the pulse conversion unit is an interferometer that divides the optical path of the continuous wave laser light into multiple paths and recombines them to output, and the laser processing machine comprises a reciprocating movable mirror arranged on one of the divided optical paths, and a movement control unit that controls the reciprocating movement of the movable mirror.

Description

[Technical Field]

[0001] The present invention relates to a laser processing machine and a laser head. [Background Art]

[0002] For example, when processing difficult-to-cut materials such as CFRP (carbon fiber reinforced plastic), if a cutting tool is used, the tool may wear out quickly after a single processing operation. Therefore, for processing difficult-to-cut materials, it is desirable to use a non-contact processing means such as laser processing.

[0003] By using a high-power single-mode fiber laser as the processing means, even carbon fiber materials with high melting points can be cut. However, resin materials tend to hardly absorb infrared light. Therefore, when cutting CFRP, which is a combination of a carbon fiber material and a resin material, by laser processing, the carbon fiber material is heated and melted by irradiation of laser light, and the resin material is then heated and melted by the residual heat of the heated carbon fiber material.

[0004] Here, if an excessive amount of heat is applied by laser light irradiation, the resin material will be excessively melted by the residual heat, making it impossible to obtain a clean cut surface. Therefore, in cutting CFRP by laser processing, it is necessary to control the excess heat amount on the cut surface by considering the balance between the heat amount applied per unit area of CFRP and the heat conduction of the carbon fiber material.

[0005] Conventionally, as disclosed, for example, in Patent Document 1, wobbling processing is known, in which a laser spot is irradiated onto the surface of CFRP, and the laser spot is translated while being scanned in a circular shape using a galvanometer mirror. According to this wobbling processing, by controlling the rotation frequency of the laser spot, for example, the amount of heat per unit area on the CFRP surface and the amount of excess heat on the cut surface can be controlled, and a clean cut surface can be obtained. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-194658 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, there is a growing demand for even higher speeds in laser processing of difficult-to-machine materials such as CFRP. In the wobbling process described above, increasing the rotation frequency of the laser spot is necessary to increase the processing speed, but this is limited by the frequency of the galvanometer mirror.

[0008] This invention has been made in view of these problems, and its main objective is to provide a novel laser processing machine that allows for easy control of excess heat on the processing surface and enables high-speed processing. [Means for solving the problem]

[0009] In other words, the laser processing machine according to the present invention performs laser processing by irradiating a workpiece with laser light, and comprises a laser light source that emits continuous wave laser light, and a pulse conversion unit that converts the continuous wave laser light into pulsed laser light and guides it to a laser output port, wherein the pulse conversion unit is an interferometer that divides the optical path of the continuous wave laser light into multiple paths and recombines them to output, and comprises a reciprocating movable mirror arranged on one of the divided optical paths, and a movement control unit that controls the reciprocating movement of the movable mirror.

[0010] With this configuration, by reciprocating the moving mirror to continuously change the optical path length, a continuous phase difference can be generated between the multiple continuous-wave laser beams divided in the interferometer. By combining these beams, a pulsed laser beam with periodically changing intensity can be obtained. In other words, by reciprocating the moving mirror, the phase of the reflected light changes continuously. When such phase-changing reflected light is combined with another reflected light, the combined laser beams with the same phase increase in intensity, while the combined laser beams with opposite phases cancel each other out, resulting in a pulsed laser beam with a constant period of intensity change. The frequency of this pulsed laser beam is determined by the wavelength of the continuous-wave laser beam (several hundred nm) and the moving speed of the moving mirror, and it is possible to obtain frequencies higher than the frequency limit of the galvanometer mirror. Furthermore, by controlling the reciprocating motion of the moving mirror with the movement control unit, the pulse period of the pulsed laser light can be changed, for example, by changing the movement speed (vibration frequency) of the moving mirror, and the amount of excess heat on the processed surface can be easily controlled. Furthermore, since the intensity of the laser light itself is periodically changed, there is no need to control the heat output on the processing surface by rotating and scanning the laser spot, as is done with wobbling using a galvanometer mirror. This makes it possible to reduce the cutting width on the processing surface.

[0011] A specific embodiment of the laser processing machine is one in which the pulse period of the pulsed laser light can be controlled by controlling the reciprocating frequency of the moving mirror with the moving control unit.

[0012] The laser processing machine preferably comprises a moving mirror comprising a mirror body and a piezo stage that supports the mirror body and is capable of vibrating along the reciprocating direction. With this type of device, it becomes possible to increase the frequency of the pulsed laser light by controlling the reciprocating motion of the moving mirror using a piezoelectric stage (piezoelectric element).

[0013] A specific embodiment of the laser processing machine is one in which the continuous-wave laser beam is a single-mode laser beam. With this type of device, the pulsed laser light output from the pulse conversion unit can be made into a clean waveform.

[0014] A specific example of the laser processing machine is one in which the output of the continuous wave laser light emitted from the light source is 1 kW or more. With this kind of device, it can emit pulsed laser light with sufficient output to function as a laser processing machine.

[0015] A specific embodiment of the pulse conversion unit further includes a beam splitter that divides the optical path of the continuous wave laser light, and a fixed mirror placed on the other divided optical path, wherein the continuous wave laser light reflected by the moving mirror and the continuous wave laser light reflected by the fixed mirror are combined again on the beam splitter.

[0016] Furthermore, in the laser processing machine, the continuous wave laser light reflected by the moving mirror and the fixed mirror is combined on the beam splitter to produce two pulsed laser beams with different optical paths and inverted phases. Preferably, the optical paths are set up so that one interfering beam is guided to the laser output port and the other interfering beam is guided to the beam damper. In this way, the unused but high-power interference light generated on the beam splitter by the combination of multiple continuous-wave laser beams is guided to the beam damper, thereby preventing damage to the laser processing machine's casing. Furthermore, since the combined intensity of the two interference beams generated in the beam splitter is constant, the intensity of the laser beam emitted from the laser output port can be controlled by changing the position of the moving mirror using the moving control unit.

[0017] Furthermore, it is preferable that the laser processing machine further includes a focusing lens positioned on the optical path of one of the interference beams and a diverging lens positioned on the optical path of the other interference beam. In this way, one of the interfering beams is focused and guided to the laser output to increase the output of the laser processing machine, while the other interfering beam, which is not used, is diverted and guided to the beam damper, thereby preventing damage to the laser processing machine's casing.

[0018] Furthermore, in the laser processing machine, it is preferable that the orientations of the fixed mirror and the movable mirror are set such that the position of the splitting point where the continuous wave laser light is split and the position of the synthesis point where the split continuous wave laser light is combined are different from each other. This method prevents the so-called reflected light generated in the beam splitter from returning to the laser light source, thus preventing damage to the laser light source.

[0019] Furthermore, it is preferable that the laser processing machine further includes a beam damper that absorbs the continuous wave laser light that has passed through the moving mirror and the fixed mirror. In this way, damage to the laser processing machine can be prevented by absorbing the light that passes through the moving and fixed mirrors, which are irradiated with high-power laser light, using a beam damper.

[0020] Furthermore, the laser processing machine preferably includes a pulsed light mode in which pulsed laser light is emitted from the laser output port and a continuous light mode in which continuous wave laser light is emitted from the laser output port, and the pulsed light mode and the continuous light mode can be switched by controlling the operation of the moving mirror with the moving control unit. In this way, optimal laser processing can be performed by switching between pulsed light mode and continuous light mode depending on the material of the workpiece. By continuously moving the moving mirror with the moving control unit, the intensity of the interference light generated by the interferometer changes periodically and can be emitted as pulsed laser light from the laser output port. On the other hand, by stopping and holding the moving mirror with the moving control unit, interference light of a constant output can be emitted from the laser output port.

[0021] Further, the laser head of the present invention is for use in a laser processing machine that performs laser processing by irradiating a workpiece with laser light, and comprises a pulse conversion unit that converts input continuous-wave laser light into pulsed laser light and outputs the pulsed laser light, wherein the pulse conversion unit is an interferometer that splits an optical path of the continuous-wave laser light into a plurality of paths, combines the split paths again, and outputs combined light, and the laser head comprises a movable mirror disposed on one of the split optical paths and capable of reciprocating in accordance with an input control signal.

[0022] With the laser head having such a configuration, the same operational effects as those of the laser processing machine of the present invention described above can be achieved.

Effects of the Invention

[0023] According to the present invention configured as described above, it is possible to provide a novel laser processing machine that facilitates control of excess heat on a processing surface and enables high-speed processing.

Brief Description of Drawings

[0024] [Figure 1] Figure schematically showing the overall configuration of a laser processing machine according to an embodiment of the present invention. [Figure 2] Figure showing temporal changes in intensity of interference light generated in the pulse conversion unit of the same embodiment. [Figure 3] Figure showing temporal changes in intensity of interference light generated in the pulse conversion unit of the same embodiment. [Figure 4] Figure showing temporal changes in intensity of interference light generated in the pulse conversion unit of the same embodiment. [Figure 5] Figure illustrating temporal changes in intensity of interference light in a continuous wave mode. [Figure 6] Figure illustrating temporal changes in intensity of interference light in a zero output mode. [Figure 7] Figure schematically showing the overall configuration of a laser processing machine according to another embodiment.

Mode for Carrying Out the Invention

[0025] A laser processing machine 100 according to one embodiment of the present invention will be described below with reference to the drawings.

[0026] The laser processing machine 100 of this embodiment performs laser processing by irradiating a workpiece W, which is made of, for example, CFRP (carbon fiber reinforced plastic), with laser light. Laser processing includes, but is not limited to, removal processes such as cutting, peeling, and drilling, joining processes such as welding and brazing, and modification processes such as hardening and marking. Furthermore, the workpiece W is not limited to CFRP and may be made of any material.

[0027] Specifically, this laser processing machine 100 comprises a laser light source 1 that generates laser light, a laser head 2 that focuses the generated laser light and irradiates the workpiece W with it, and a control device C.

[0028] The laser light source 1 emits single-mode continuous-wave laser light (CW laser light). The laser light source 1 in this embodiment is configured to emit high-power continuous-wave laser light of 1 kW or more. The laser light source 1 in this embodiment is a fiber laser, but it is not limited to this and may be other types such as a CO2 laser or an excimer laser. The wavelength of the emitted continuous-wave laser light may be arbitrarily changed depending on the type of processing.

[0029] The laser head 2 includes an input port 2i into which laser light emitted from the laser light source 1 is input, a laser output port 2o that emits laser light toward the workpiece W, and an optical system that guides the laser light input from the input port 2i to the laser output port 2o.

[0030] Control device C is a computer equipped with a CPU, memory, input / output interfaces, etc. Based on a program stored in memory, this control device C performs at least the function of a movement control unit C1 by coordinating the CPU and its peripheral devices.

[0031] Furthermore, this laser processing machine 100 is equipped with a pulse conversion unit 4 that converts the continuous wave laser light emitted from the laser light source 1 into pulsed laser light and guides it to the laser emission port 2o, and is configured to irradiate the workpiece W with pulsed laser light.

[0032] The pulse conversion unit 4 utilizes the principle of an interferometer (specifically a Michelson interferometer) which divides the optical path of the input continuous-wave laser light into multiple paths, recombines them, and outputs the resulting interference light as pulsed laser light.

[0033] Specifically, as shown in Figure 1, the pulse conversion unit 4 comprises at least a beam splitter 41, a fixed mirror 42, a movable mirror 43, and a movement control unit C1.

[0034] The beam splitter 41 is positioned on the optical path of the continuous-wave laser beam and divides the optical path of the continuous-wave laser beam into multiple paths. Specifically, this beam splitter 41 is composed of half mirrors and splits the continuous-wave laser beam into transmitted light and reflected light.

[0035] The fixed mirror 42 is positioned in a fixed location on one of the optical paths split by the beam splitter 41, and reflects the split continuous wave laser light. In this embodiment, the fixed mirror 42 reflects the continuous wave laser light, which is the reflected light split by the beam splitter 41.

[0036] The movable mirror 43 is positioned on one of the optical paths split by the beam splitter 41 and is configured to reciprocate in the direction of the optical path in response to a control signal from the movement control unit C1. Reciprocating in the direction of the optical path means that it can reciprocate in a direction that changes the optical path length. In this embodiment, the movable mirror 43 reflects the continuous wave laser light, which is the transmitted light split by the beam splitter 41.

[0037] The movable mirror 43 comprises a mirror body and a piezo stage that supports the mirror body and is capable of vibrating along the reciprocating direction. The piezo stage receives a voltage as a control signal from the movement control unit C1, causing its internal piezo element to vibrate and repeat periodic vibrations along the reciprocating direction.

[0038] The orientation and position of these fixed mirrors 42 and movable mirrors 43 are set so that their respective reflected light is combined on the beam splitter 41 and directed towards the laser output port 2o.

[0039] The movement control unit C1 controls the reciprocating motion of the moving mirror 43 (specifically, the piezo stage) by applying a voltage to it. For example, the movement control unit C1 adjusts the vibration frequency and amplitude of the moving mirror 43 by applying a voltage to a piezo element and causing a displacement of several tens of microns due to its electrostrictive effect.

[0040] By moving the movable mirror 43 back and forth, the optical path length of the transmitted light in the divided continuous-wave laser beam changes continuously, and a continuous phase difference is created between it and the reflected light reflected by the fixed mirror 42. As a result, the combined interference wave takes on a pulse wave shape with intensity peaks appearing at a constant period, as shown in Figure 2.

[0041] The movement control unit C1 controls the vibration frequency of the moving mirror 43, thereby controlling the pulse period of the emitted pulsed laser light. For example, by increasing the vibration frequency of the moving mirror 43 using the movement control unit C1, the pulse frequency of the pulsed laser light can be increased, as shown in Figure 3. On the other hand, by decreasing the vibration frequency of the moving mirror 43 using the movement control unit C1, the pulse frequency of the pulsed laser light can be decreased, as shown in Figure 4.

[0042] In the laser processing machine 100 of this embodiment, a first focusing lens 21 that focuses the input continuous wave laser light into parallel light and a reflective mirror 22 that reflects the continuous wave laser light that has passed through the first focusing lens 21 and guides it to the beam splitter 41 are arranged in the optical path between the input port 2i and the beam splitter 41. In addition, a second focusing lens 23 is arranged in the optical path between the beam splitter 41 and the laser emission port 2o to focus the pulsed laser light, which is substantially parallel light synthesized on the beam splitter 41, to a single point (the focal point).

[0043] Furthermore, in the laser processing machine 100 of this embodiment, the pulse conversion unit 4 is configured using the principle of an interferometer. As shown in Figure 1, the continuous wave laser light reflected by the moving mirror 43 and the fixed mirror 42 is combined on the beam splitter 41, generating two interference beams (pulsed laser beams) PL1 and PL2 with different optical paths. The optical paths of these two interference beams PL1 and PL2 are symmetrical with respect to the beam splitter 41 (half mirror). Also, as shown in Figures 2 to 4, the phases of the two interference beams PL1 and PL2 are inverted, and their total intensity remains constant regardless of time.

[0044] One pulsed laser beam, PL1, is generated by the combination of reflected light from the moving mirror 43 that has passed through the beam splitter 41 and reflected light from the fixed mirror 42 that has been reflected by the beam splitter 41. The other pulsed laser beam, PL2, is generated by the combination of reflected light from the moving mirror 43 that has been reflected by the beam splitter 41 and reflected light from the fixed mirror 42 that has passed through the beam splitter 41.

[0045] The optical path is set such that one of the two pulsed laser beams, PL1 and PL2 (in this case, pulsed laser beam L1), is guided to the laser output port 2o as the processing laser beam. The second focusing lens 23 is positioned along the optical path of the processing pulsed laser beam PL1.

[0046] Furthermore, the other pulsed laser beam PL2 is the so-called reflected light in the interferometer, and the positions and orientations of the fixed mirror 42 and movable mirror 43 relative to the beam splitter 41 are set so that it does not return to the laser light source 1. Specifically, in the beam splitter 41, the positions and orientations of the fixed mirror 42 and movable mirror 43 are set so that the position of the splitting point Ps where the continuous wave laser beam is split and the position of the combining point Pr where the two split continuous wave laser beams are combined are different from each other.

[0047] The other pulsed laser beam PL2, which is the reflected light, has its optical path set so that it is guided to a beam damper 45 (specifically a water-cooled damper) located inside the laser head 2. A diverging lens 44 that diverges the pulsed laser beam is also placed on the optical path of the other pulsed laser beam PL2.

[0048] Furthermore, in the laser processing machine 100 of this embodiment, a beam damper (not shown) that absorbs the continuous wave laser light transmitted through the fixed mirror 42 and the movable mirror 43 is provided inside the laser head 2. The beam damper is provided on the back side of the fixed mirror 42 and the movable mirror 43, respectively.

[0049] With the laser processing machine 100 of this embodiment configured in this way, by reciprocating the moving mirror 43 to continuously change the optical path length, a phase difference can be continuously generated between the multiple continuous wave laser beams divided in the interferometer, and by combining these, a pulsed laser beam with periodically changing intensity can be obtained. That is, by reciprocating the moving mirror 43, the phase of the reflected light changes continuously, and when such phase-changing reflected light is combined with the other reflected light, the intensity increases when laser beams with the same phase are combined, and cancels out when laser beams with opposite phases are combined, resulting in a pulsed laser beam with an intensity that changes at a constant period. The frequency of this pulsed laser beam is determined by the wavelength of the continuous wave laser beam (several hundred nm) and the moving speed of the moving mirror 43, and a high frequency exceeding the frequency limit of the galvanometer mirror can be obtained.

[0050] Furthermore, by controlling the reciprocating motion of the moving mirror 43 with the moving control unit C1, the pulse period of the pulsed laser light can be changed, for example, by changing the moving speed (vibration frequency) of the moving mirror 43, and the excess heat on the processed surface can be easily controlled.

[0051] Furthermore, since the intensity of the laser light itself is periodically changed, there is no need to control the heat output on the processing surface by rotating and scanning the laser spot, as is done with wobbling using a galvanometer mirror. This makes it possible to reduce the cutting width on the processing surface.

[0052] However, the present invention is not limited to the embodiments described above.

[0053] In another embodiment, the laser processing machine 100 is equipped with a pulsed light mode in which pulsed laser light is emitted from the laser emission port 2o, a continuous light mode in which continuous wave laser light is emitted from the laser emission port 2o, and a zero output mode in which the output of laser light from the laser emission port 2o is set to zero. These modes can be switched by controlling the operation of the moving mirror 43 with the moving control unit C1.

[0054] In pulsed light mode, as described above, the movement control unit C1 moves (reciprocates) the moving mirror 43, causing the intensity of the interference light PL1 to change periodically, as shown in Figures 2-4, and the interference light PL1 is emitted from the laser output port 2o as pulsed laser light.

[0055] In continuous light mode, as shown in Figure 5, the movement control unit C1 controls the moving mirror 43 and stops it at a position where the intensity of the interference light PL1 is greater than 0. As a result, the interference light PL1 is emitted from the laser output port 2o as continuous wave laser light. Also in continuous light mode, as shown in Figure 5, the movement control unit C1 can change the intensity of the continuous wave laser light emitted from the laser output port 2o by controlling the moving mirror 43 and changing its stopping position.

[0056] In zero-output mode, as shown in Figure 6, the movement control unit C1 controls the moving mirror 43 and stops it at a position where the intensity of the interference light PL1 becomes zero. As a result, the interference light PL1 emitted from the laser output port 2o becomes zero output.

[0057] For example, in the above embodiment, the transmitted light split by the beam splitter 41 was reflected by the moving mirror 43, but this is not limited to this configuration. In other embodiments, the system may be configured to reflect the reflected light split by the beam splitter 41 by the moving mirror 43.

[0058] Furthermore, in the above embodiment, one of the multiple continuous wave laser beams split by the beam splitter 41 was reflected by the moving mirror 43 and the other was reflected by the fixed mirror 42, but the embodiment is not limited to this. In other embodiments, as shown in Figure 7, a moving mirror 43' may be placed in place of the fixed mirror 42, so that one of the continuous wave laser beams split by the beam splitter 41 (e.g., transmitted light) is reflected by one moving mirror 43 and the other continuous wave laser beam (e.g., reflected light) is reflected by the other moving mirror 43'.

[0059] Furthermore, although the above embodiment used a piezo stage to configure the moving mirror 43, it is not limited to this. In other embodiments, the moving mirror 43 may be configured using any moving mechanism that can move the reflective surface of the mirror back and forth in the direction of the optical path.

[0060] Furthermore, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. [Explanation of Symbols]

[0061] 100... Laser processing machine 1. Laser light source 2 ···Laser head 2i ···Input port 2o...Ejection port 21 ···First focusing lens 22 ···Reflective mirror 23 ···Second focusing lens C...control device C1 ···Movement Control Unit 4. Pulse conversion section 41...Beam Splitter 42 ···Fixed mirror 43 ···Moving mirror 43' ···Moving mirror 44 ···Diverging lenses 45 ···Beam damper Ps...Dividing point Pr...Synthesis point W ···Object to be processed

Claims

1. A laser processing machine that performs laser processing by irradiating a workpiece with laser light, A laser light source that emits continuous wave laser light, The system includes a pulse conversion unit that converts the continuous wave laser light into pulsed laser light and guides it to the laser output port, The pulse conversion unit is an interferometer that divides the optical path of the continuous wave laser light into multiple paths, recombines them, and outputs the result. A reciprocating movable mirror arranged on one of the divided optical paths, A laser processing machine comprising a movement control unit that controls the reciprocating motion of the moving mirror.

2. The laser processing machine according to claim 1, wherein the pulse period of the pulsed laser light can be controlled by controlling the reciprocating frequency of the moving mirror with the moving control unit.

3. The laser processing machine according to claim 1, wherein the moving mirror comprises a mirror body and a piezo stage that supports the mirror body and is vibrable along the reciprocating direction.

4. The laser processing machine according to claim 1, wherein the continuous wave laser light is a single-mode laser light.

5. The laser processing machine according to claim 1, wherein the output of the continuous wave laser light emitted from the light source is 1 kW or more.

6. The pulse conversion unit, A beam splitter that divides the optical path of the continuous wave laser light, The system further comprises a fixed mirror placed on the other divided optical path, The laser processing machine according to claim 1, wherein the continuous wave laser light reflected by the moving mirror and the continuous wave laser light reflected by the fixed mirror are combined again on the beam splitter.

7. The laser processing machine according to claim 6, wherein the continuous wave laser light reflected by the moving mirror and the fixed mirror is combined on the beam splitter to produce two interference beams with different optical paths and inverted phases, and each optical path is set to guide one interference beam to the laser output port and the other interference beam to the beam damper.

8. A focusing lens placed on the optical path of one of the aforementioned interference light, The laser processing machine according to claim 7, further comprising a diverging lens disposed on the optical path of the other interference light.

9. The laser processing machine according to claim 6, wherein the orientation of the fixed mirror and the movable mirror is set such that the position of the splitting point where the continuous wave laser light is split and the position of the synthesis point where the split continuous wave laser light is combined are different from each other.

10. The laser processing machine according to claim 6, further comprising a beam damper that absorbs the continuous wave laser light transmitted through the moving mirror and the fixed mirror.

11. The system includes a pulsed light mode in which pulsed laser light is emitted from the laser output port, and a continuous light mode in which continuous wave laser light is emitted from the laser output port. The laser processing machine according to claim 1, wherein the operation of the moving mirror is controlled by the moving control unit, thereby switching between the pulsed light mode and the continuous light mode.

12. This is a laser head for a laser processing machine that performs laser processing by irradiating a workpiece with laser light. It includes a pulse conversion unit that converts the input continuous wave laser light into pulsed laser light and outputs it. The pulse conversion unit is an interferometer that divides the optical path of the continuous wave laser light into multiple paths, recombines them, and outputs the result. A laser head comprising a movable mirror positioned on one of the divided optical paths and capable of reciprocating in response to an input control signal.

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