Laser boring method and laser processing machine

Abstract

The invention provides a laser boring method and a laser processing machine. The laser perforation method comprises the following steps: generating a covering part covered with oil on a workpiece; irradiating the laser light to the cover portion such that a laser output density of the laser light is a first laser output density at a central portion of the cover portion irradiated by the laser light and a second laser output density smaller than the first laser output density at a peripheral portion around the central portion of the cover portion, a third laser output density smaller than the second laser output density at a boundary portion between the central portion and the peripheral portion in the cover portion; melting the workpiece in the covering part by a first laser beam irradiated to the central part, and blowing a gas onto the melted workpiece to make the melted workpiece fly around the central part, thereby forming a through hole in the covering part; and heating, by means of a second laser beam irradiated to the peripheral portion, a base of a sputter, which is a scattered workpiece and which is in contact with the workpiece to be processed in which the through-hole is formed without the aid of oil.

Description

Technical Field

[0001] The invention relates to a laser perforating method and a laser processing machine. Background Art

[0002] Most laser processing machines use a single laser source (e.g., Patent Document 1), but Patent Document 2 shows a machine tool that can achieve high-quality drilling with less adhesion of sputtering materials according to the thickness of the workpiece by controlling the intensity of the central and peripheral parts of the laser. Patent Document 3 discloses a technology for suppressing the adhesion of sputtering materials generated by drilling by applying oil before drilling.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 8-192283 Patent Document 2: International Publication No. 2017 / 134964 Patent Document 3: Japanese Patent Application Publication No. 2000-84686

[0004] Even if oil is applied before drilling, the root of the spatter near the through hole is directly connected to the component of the workpiece without the help of oil. If the root is cooled and solidified during the drilling process, the removal of the spatter becomes difficult. Summary of the invention

[0005] The purpose of the technology disclosed in the present application is to provide a laser drilling method and a laser processing machine for suppressing the root solidification of sputtering generated by drilling and improving the processing quality.

[0006] The laser perforation method of the first mode of the present invention includes blowing oil onto a workpiece to generate a covering portion covered with oil on the workpiece. The method includes irradiating a laser onto the covering portion so that the laser output density of the laser is a first laser output density at the central portion of the covering portion irradiated by the laser, a second laser output density less than the first laser output density at the peripheral portion around the central portion of the covering portion, and a third laser output density less than the second laser output density at the boundary portion between the central portion and the peripheral portion of the covering portion. The method includes melting the workpiece in the covering portion by irradiating the first laser onto the central portion, and blowing gas onto the molten workpiece so that the molten workpiece is scattered around the central portion, thereby opening a through hole in the covering portion. The method includes heating the root of the sputtered workpiece that is in contact with the workpiece to be processed to form the through hole without the aid of oil by irradiating the second laser onto the peripheral portion.

[0007] According to a second aspect of the present invention, the laser perforation method of the first aspect includes removing the sputtering from the workpiece by blowing gas onto the sputtering after heating the root. In addition, the direction of blowing the gas onto the sputtering is preferably different from the direction of blowing the gas for scattering the molten workpiece.

[0008] According to a third aspect of the present invention, in the laser drilling method of the second aspect, removing the sputtering from the workpiece includes moving the torch from the outside of the root along a circle surrounding the root and blowing gas from the torch to the periphery of the root.

[0009] According to the fourth aspect of the present invention, in the laser perforation method of any one of the first aspect to the third aspect, the method includes heating the sputtering material by a second laser to the extent that the sputtering material does not adhere to and solidify on the workpiece to be processed. In the case where a plurality of sputtering materials are generated by the first laser, the sputtering material can also be heated by a second laser to the extent that at least one of the plurality of sputtering materials does not adhere to and solidify on the workpiece to be processed. In this case, it is preferred to heat the sputtering material by the second laser to the extent that at least one of the plurality of sputtering materials is scattered by the gas of the second aspect or the third aspect. In addition, it is more preferred to heat the sputtering material by the second laser to the extent that all of the sputtering materials in the plurality of sputtering materials are scattered by the gas of the second aspect or the third aspect. It is further preferred to heat the sputtering material by the second laser to the extent that all of the sputtering materials in the plurality of sputtering materials do not adhere to and solidify on the workpiece to be processed.

[0010] According to a fifth aspect of the present invention, in the laser drilling method of any one of the first to fourth aspects, the workpiece is heated by the second laser to such an extent that the outer side of the peripheral portion is not drilled.

[0011] According to a sixth aspect of the present invention, in the laser drilling method according to any one of the fifth aspects, the workpiece in the covering portion is melted by the first laser to such an extent that the outer side of the peripheral portion is not drilled.

[0012] According to a seventh aspect of the present invention, in the laser drilling method of the fifth aspect or the sixth aspect, the workpiece is heated by the second laser to such an extent that sputtering is not generated outside the peripheral portion.

[0013] According to an eighth aspect of the present invention, the laser perforation method of any one of the first to seventh aspects further includes preparing an optical fiber, the optical fiber including a first transmission portion, a second transmission portion disposed around the first transmission portion, and a reflector disposed between the first transmission portion and the second transmission portion. The method further includes emitting laser light from a laser oscillator so that a portion of the laser light enters the first transmission portion and another portion of the laser light enters the second transmission portion, thereby generating the first laser light and the second laser light.

[0014] The laser processing machine of the ninth mode of the present invention comprises at least one laser oscillator, an optical fiber, a lens, a flashlight, a moving mechanism, a nozzle, a first pump, a second pump and a control circuit. At least one laser oscillator is configured to emit a first laser and a second laser. The optical fiber has a first end for receiving the first laser and the second laser from at least one laser oscillator, and a second end opposite to the first end. The optical fiber includes a first transmission part for transmitting the first laser, a second transmission part arranged around the first transmission part and transmitting the second laser, and a reflector arranged between the first transmission part and the second transmission part. The lens is arranged opposite to the second end of the optical fiber, and is configured to converge the first laser and the second laser transmitted from the optical fiber toward the workpiece. The flashlight has an opening for passing the light converged by the lens and the gas for blowing to the workpiece. The moving mechanism is configured to move the flashlight. The nozzle is configured to spray oil to the workpiece. The first pump is configured to deliver oil to the nozzle. The second pump is configured to deliver gas to the flashlight. The control circuit is configured to control the laser oscillator, the first pump, the second pump and the moving mechanism. The control circuit is configured to control the at least one laser oscillator and the second pump to irradiate the first laser and the second laser to the covering portion after controlling the first pump to blow oil to the workpiece to generate a covering portion covered with oil on the workpiece, and to blow gas to the workpiece melted by the first laser to open a through hole in the covering portion. The laser output density at the central portion of the covering portion irradiated by the first laser is the first laser output density, the laser output density at the peripheral portion of the covering portion irradiated by the second laser is the second laser output density which is smaller than the first laser output density, and the laser output density at the boundary portion between the central portion and the peripheral portion of the covering portion is the third laser output density which is smaller than the second laser output density.

[0015] According to the tenth aspect of the present invention, the laser processing mechanism of the ninth aspect is a control circuit that controls the moving mechanism and the second pump to further blow gas to the sputtered product obtained by the workpiece melted by the first laser and scattered around the through hole due to the gas. In addition, the direction of blowing gas to the sputtered product is preferably different from the direction of blowing gas for scattering the melted workpiece.

[0016] According to the eleventh aspect of the present invention, the laser processing mechanism of the tenth aspect is configured such that the control circuit controls the moving mechanism and the second pump so that the flashlight moves along a circle surrounding the through hole and blows gas around the through hole.

[0017] According to the twelfth mode of the present invention, the laser processing mechanism of any one of the ninth mode to the eleventh mode is configured such that the second laser output density is a laser output density at which the second laser can heat the workpiece to the extent that the sputtering obtained by the workpiece after melting by the first laser and scattering around the through hole due to the gas does not adhere to and solidify on the processed workpiece forming the through hole. In the case where multiple sputtering objects are generated by the first laser, the second laser output density can also be a laser output density at which the second laser can heat the workpiece to the extent that at least one of the multiple sputtering objects does not adhere to and solidify on the processed workpiece. In this case, the second laser output density is preferably a laser output density at which the second laser can heat the workpiece to the extent that at least one of the multiple sputtering objects is scattered due to the gas of the second mode or the third mode. In addition, the second laser output density is more preferably a laser output density at which the second laser can heat the workpiece to the extent that all of the multiple sputtering objects are scattered due to the gas of the second mode or the third mode. The second laser output density is more preferably a laser output density at which the second laser can heat the workpiece to such an extent that all of the plurality of sputtered products do not adhere to and solidify on the workpiece.

[0018] According to the thirteenth embodiment of the present invention, the laser processing mechanism of any one of the ninth to twelfth embodiments is configured such that the first laser output density is a laser output density at which the first laser can heat the workpiece to a degree without perforating the outer side of the peripheral portion, and the second laser output density is a laser output density at which the second laser can heat the workpiece to a degree without perforating the outer side of the peripheral portion.

[0019] According to a fourteenth aspect of the present invention, the laser processing mechanism of the thirteenth aspect is configured such that the second laser output density is a laser output density at which the second laser light can heat the workpiece to such an extent that sputtering is not generated outside the peripheral portion.

[0020] According to a fifteenth aspect of the present invention, in the laser processing machine of any one of the ninth to fourteenth aspects, at least one laser oscillator includes a laser oscillator that emits laser light. The laser processing machine is configured to adjust the emission direction of the laser light of the one laser oscillator so that a part of the laser light enters the first transmission portion and another part of the laser light enters the second transmission portion.

[0021] The laser perforation method of the first mode heats the root of the sputtered material by a second laser having a second laser output density smaller than the output density of the first laser that opens the through hole. Thus, the root of the sputtered material can be prevented from adhering to the workpiece at the peripheral portion of the through hole, and the sputtered material can be easily removed. The laser processing machine of the ninth mode can heat the root of the sputtered material by a second laser having a second laser output density.

[0022] In the laser drilling method of the second aspect and the laser processing machine of the tenth aspect, the sputtered matter whose root portion is suppressed from adhering due to heating can be easily removed by gas.

[0023] In the laser drilling method of the third aspect and the laser processing machine of the eleventh aspect, since the gas can be blown from the outside of the sputtered material toward the root, more sputtered material can be removed by the gas.

[0024] In the laser drilling method of the fourth aspect and the laser processing machine of the twelfth aspect, the sputtered matter that is not adhered at the root can be easily removed by gas.

[0025] If the outside of the heating area irradiated by the second laser is perforated, the root of the sputtered material generated thereby cannot be directly heated by the second laser, and the root cools and sticks. In the fifth embodiment of the laser perforation method, since the workpiece is heated by the second laser to the extent that the outside of the heating area is not perforated, such risk is reduced. In addition, if the second laser is weak, or the outside of the heating area is perforated by the first laser because the heating area is smaller than the perforation area, the same problem will arise. In the sixth embodiment of the laser perforation method, since the workpiece is heated by the first laser to the extent that the outside of the heating area is not perforated, such risk is further reduced. In the thirteenth embodiment of the laser processing machine, since the workpiece is heated by the first laser and the second laser to the extent that the outside of the heating area is not perforated, the above-mentioned risk is reduced.

[0026] Even if the outside of the heated area is not perforated, if a portion of the peripheral portion of the through hole outside the area irradiated by the second laser is melted by the second laser and scattered by the auxiliary gas, the root of the sputtered product thus formed cannot be directly heated by the second laser, and the root cools and adheres. In the laser perforation method of the seventh aspect and the laser processing machine of the fourteenth aspect, since the workpiece is heated by the second laser to a degree that sputtered products are not generated outside the processing area, such a risk is reduced.

[0027] The laser perforating method of the eighth aspect and the laser processing machine of the fifteenth aspect generate the first laser beam and the second laser beam by one laser oscillator, and thus can reduce the manufacturing cost.

[0028] According to the technology disclosed in the present application, it is possible to provide a laser drilling method and a laser processing machine for suppressing the solidification of the root of sputtering generated by drilling and improving the processing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a figure which shows the external appearance structure of the laser processing machine which concerns on embodiment. Figure 2 It is a cross-sectional view of a laser head of a laser processing machine according to an embodiment. Figure 3 It is a diagram showing the internal structure of an optical fiber according to an embodiment. Figure 4A An output example of laser light according to the embodiment is shown. Figure 4B An output example of laser light according to the embodiment is shown. Figure 4C An output example of laser light according to the embodiment is shown. Figure 5 It is a schematic diagram showing a perforation method according to an embodiment. Figure 6 It is another schematic diagram showing the punching method according to the embodiment. Figure 7 This is a schematic diagram of laser light from a flashlight according to an embodiment. Fig. 8A This is an example of a non-preferred perforation method of the embodiment. Figure 8B This is an example of a non-preferred perforation method of the embodiment. Fig. 9 is a flowchart showing a perforation method according to an embodiment. Fig.10 Represents the results of the validation experiment. DETAILED DESCRIPTION

[0030] Hereinafter, the present invention will be described in detail based on the accompanying drawings showing embodiments of the present invention. In addition, the same reference numerals in the drawings represent corresponding structures or substantially the same structures. <Implementation Method> <Structure of Laser Processing Machine 1> Figure 1 It is a schematic structural diagram showing the external appearance structure of a laser processing machine 1 according to an embodiment of the present invention. Figure 1 The X-axis shown is along the depth direction of the laser processing machine 1, the Y-axis is along the width direction of the laser processing machine 1, and the Z-axis is along the height direction of the laser processing machine 1. Hereinafter, the directions along the X-axis, the Y-axis, and the Z-axis are referred to as the X-direction, the Y-direction, and the Z-direction, respectively. Figure 1As shown, the laser processing machine 1 includes a base 10, a first guide rail 11, a column 12, a second guide rail 13, a saddle 14, a nozzle 15, a first pump 16, a laser head 20, at least one laser oscillator 30, an optical fiber 40, and a numerical control apparatus 6. The laser processing machine 1 is a device for processing a metal plate MP on the base 10. The metal plate MP is, for example, mild steel, SUS (Steel Use Stainless Steel), aluminum steel, brass, and copper. In addition, the metal plate MP can also be referred to as a workpiece W. The base 10 can also have a plurality of elongated projections. A pair of first guide rails 11 are installed along the Y direction at both ends of the base 10, and the column 12 is installed on the first guide rail 11 so as to be movable on the first guide rail 11. The column 12 moves on the first rail 11 by a driving force of a driving device D1 such as a motor provided on one of the first rail 11 and the column 12 .

[0031] A second guide rail 13 is provided on the column 12 along the Y axis orthogonal to the X axis, and a saddle 14 is mounted on the second guide rail 13 so as to be movable in the Y direction. The saddle 14 moves on the second guide rail 13, for example, by the driving force of a driving device D2 such as a motor provided on either one of the second guide rail 13 and the saddle 14. Although not shown, the column 12 may be covered by a corrugated cover. The laser head 20 is mounted on the saddle 14 so as to be movable in the Z direction along the Z axis perpendicular to the X axis and the Y axis. The laser head 20 moves on the saddle 14, for example, by the driving force of a driving device D3 such as a motor provided on either one of the saddle 14 and the laser head 20. The laser head 20 is configured to process the metal plate MP on the base 10. The laser head 20 has an optical system for introducing laser light transmitted from at least one laser oscillator 30. The laser head 20 includes a torch 28 for laser processing.

[0032] The nozzle 15 is configured to spray oil toward the workpiece W before the laser is irradiated by the laser head 20 described later. The first pump 16 is configured to deliver oil to the nozzle 15. The oil is stored in an oil tank (not shown). Figure 1In the embodiment, the nozzle 15 and the first pump 16 are mounted on the saddle 14, but the nozzle 15 and the first pump 16 may be mounted on the base 10. At least one laser oscillator 30 outputs a laser for processing the metal plate MP. The optical fiber 40 is retractably connected to the at least one laser oscillator 30 and the laser head 20 to supply the laser output from the at least one laser oscillator 30 to the laser head 20. The optical fiber 40 has a first end 40a for receiving the laser from the at least one laser oscillator 30, and a second end 40b opposite to the first end 40a. The numerical control device 6 has a control circuit 7 including a hardware processor, a memory, etc. The control circuit 7 is configured to control the at least one laser oscillator 30, the driving devices M1 to M3, and the first pump 16 to process the metal plate MP. In the following embodiment, the driving devices D1 to D3 are collectively referred to as a transfer mechanism TM. The transfer mechanism TM is configured to move the flashlight 28.

[0033] Figure 2 It is a cross-sectional view of the laser head 20 of the laser processing machine 1 according to the embodiment. Figure 2 A cross-sectional view of the laser head 20 cut along a cutting plane passing through the optical axis RZ of the laser beam irradiated from the flashlight 28 is shown to explain the optical system of the laser head 20. Figure 2 The laser head 20 has a head body 21, an upper unit 22, and a lower unit 23. The upper unit 22 is mounted on the head body 21. The upper unit 22 includes a connector 25 and a reflector 26. The connector 25 is a connector for mounting the second end 40b of the optical fiber 40 on the laser head 20. In addition, the optical fiber 40 connector 25 reflector 26 reflects the laser output from the connector 25 toward the lower unit 23.

[0034] The lower unit 23 is mounted on the head body 21. The lower unit 23 includes a lens 24, which is disposed opposite to the second end 40b of the optical fiber 40 and is configured to converge the laser light transmitted from the optical fiber 40 toward the workpiece W. That is, the laser processing machine 1 includes the lens 24. Figure 2 Although not shown, another lens for converging the light emitted from the second end 40b of the optical fiber 40 may be provided between the connector 25 and the lens 24. A flashlight 28 is mounted on the top of the lower unit 23. An optical path 27 for passing laser light is provided in the upper unit 22, the head body 21, the lower unit 23, and the flashlight 28.

[0035] like Figure 2As shown, the laser processing machine 1 has a second pump 17 in the head body 21. The second pump 17 is configured to deliver gas to the flashlight 28. The control circuit 7 is configured to control the second pump 17. The gas is, for example, oxygen for promoting the melting of the workpiece W, but may also be air, nitrogen, and argon. In the following embodiments, the gas delivered from the second pump is referred to as auxiliary gas AG. The auxiliary gas AG is stored in the gas storage 18 (see Figure 1 ), and is delivered to the flashlight 28 through the gas supply passage 19. The flashlight 28 has a connector 29 for connecting to the gas supply passage 19. The flashlight 28 has an opening 28h through which the light focused by the lens 24 and the gas blown toward the workpiece W pass.

[0036] Figure 3 4 is an internal structure diagram of an optical fiber 40 according to an embodiment. The optical fiber 40 includes a first transmission portion 42, a second transmission portion 44, a reflector 46, and an additional reflector 48. The first transmission portion 42 is cylindrical and is configured to transmit laser light. The reflector 46 is a tubular member covering the outer periphery of the first transmission portion 42, and is configured to reflect laser light at an interface with the first transmission portion 42. The second transmission portion 44 is a tubular member covering the outer periphery of the reflector 46, and is configured to transmit laser light. In other words, the second transmission portion 44 is arranged around the first transmission portion 42. The reflector 46 is arranged between the first transmission portion 42 and the second transmission portion 44. The reflector 46 is configured to reflect laser light at an interface with the second transmission portion 44. The additional reflector 48 is a tubular member covering the outer periphery of the second transmission portion 44, and is configured to reflect laser light at an interface with the second transmission portion 44.

[0037] Figures 4A to 4C FIG. 2 shows an output example of the laser beam RL according to the embodiment. In the embodiment, at least one laser oscillator 30 includes a laser oscillator 30A that emits the laser beam RL. The laser oscillator 30A is configured to be able to Figures 4A to 4C As shown, the positional relationship between the optical axis Ax1 of the laser light RL outputted from the laser oscillator 30A and the central axis Ax2 of the optical fiber 40 is changed. Figure 4A An example is shown in which the optical axis Ax1 of the laser light RL is aligned with the central axis Ax2 of the optical fiber 40 . Figure 4B An example is shown in which the optical axis Ax1 of the laser light RL is directed slightly inward from the reflector 46 . Figure 4C An example is shown in which the optical axis Ax1 of the laser light RL is directed toward the vicinity of the center of the second transmission portion 44 .

[0038] Figures 4A to 4C The right side of the figure of the optical fiber 40 shows the magnitude of the laser output density. Figures 4A to 4C In the graph, the further to the right the line is, the greater the laser output density is. Figure 4AIn the case of the laser beam RL not entering the second transmission portion 44, the laser output density is maximum near the central axis Ax2 of the optical fiber 40 and then decreases gradually. Figure 4B In FIG. 4 , it is shown that when the optical fiber 40 is long enough, due to the influence of diffuse reflection at the reflector 46 and the additional reflector 48, the laser output density has two peaks near the central axis Ax2 of the optical fiber 40 and near the center of the second transmission part 44. Moreover, the peak near the central axis Ax2 of the optical fiber 40 is greater than the peak near the center of the second transmission part 44. Figure 4C In the example, the laser light RL hardly enters the first transmission portion 42 , and therefore has a peak only near the center of the second transmission portion 44 , or the peak near the center of the second transmission portion 44 is larger than the peak near the central axis Ax2 of the optical fiber 40 .

[0039] In this embodiment, the laser oscillator 30A is positioned at Figure 4B In such a position, the laser output density of the first transmission section 42 is set to be greater than the laser output density of the second transmission section 44. That is, the emission direction of the laser RL of one laser oscillator 30A is adjusted so that a part of the laser RL enters the first transmission section 42 and the other part of the laser RL enters the second transmission section 44. In other words, by emitting the laser RL from one laser oscillator 30A so that a part of the laser RL enters the first transmission section 42 and the other part of the laser RL enters the second transmission section 44, the first laser RL1 and the second laser RL2 are generated. In the following embodiments, the laser output from the first transmission section 42 is referred to as the first laser RL1, and the laser output from the second transmission section 44 is referred to as the second laser RL2. Therefore, at least one laser oscillator 30 is configured to emit the first laser RL1 and the second laser RL2. The first transmission section 42 transmits the first laser RL1. The second transmission section 44 transmits the second laser RL2.

[0040] Figure 5 Schematic diagram of a perforation method according to an embodiment. Figure 5As shown, the control circuit 7 is configured to control the first pump 16 to blow the oil OIL to the workpiece W to form a coating portion (coating portion) WCP covered with the oil OIL on the workpiece W, and then control at least one laser oscillator 30 and the second pump 17 to irradiate the first laser RL1 and the second laser RL2 to the coating portion WCP and blow the gas (auxiliary gas AG) to the workpiece MEW melted by the first laser RL1 to open the through hole PH in the workpiece W. In particular, the control circuit 7 is configured to control the second laser RL2 to heat the root RT of the sputter SPT, and when the gas (auxiliary gas AG) is blown to the melted workpiece MEW, the sputter SPT is scattered around the through hole PH. The melted workpiece MEW refers to the workpiece W in a state where the viscosity is reduced by heating to the extent that it is scattered by the auxiliary gas AG. The root RT refers to the portion of the sputter SPT that is in contact with the workpiece MAW to be processed to form the through hole PH without the help of the oil OIL.

[0041] Figure 6 is another schematic diagram showing a perforation method according to an embodiment. Figure 6 As shown, the control circuit 7 is configured to control the moving mechanism TM and the second pump 17 to further blow the gas (e.g., auxiliary gas AG) to the workpiece MEW melted by the first laser RL1, and the sputtering SPT is obtained by the gas (e.g., auxiliary gas AG) being scattered around the through hole PH. In addition, the blowing direction of the gas is different from the blowing direction to the melted workpiece MEW. In addition, the gas blown at this time may also be a gas different from the gas used to scatter the melted workpiece. Specifically, as Figure 6 As shown, the control circuit 7 is configured to control TM and the second pump 17 to move the flashlight 28 along a circle CIR surrounding the through hole PH and blow gas (eg, auxiliary gas AG) around the through hole PH.

[0042] Figure 7 FIG. 2 is a schematic diagram of laser light RL from a flashlight 28 according to an embodiment. Figure 7 As shown, the laser RL is maximally converged at the focal position FP and is incident on the surface of the cover portion WCP in a slightly expanded state. Here, the portion of the cover portion WCP irradiated by the first laser RL1 is referred to as the central portion CP, and the portion irradiated by the second laser RL2 is referred to as the peripheral portion PP. The peripheral portion PP surrounds the central portion CP in the radial direction relative to the optical axis RZ of the laser RL. The boundary between the central portion CP and the peripheral portion PP can be determined based on the assumption that the laser is emitted from the reflectors 46 and 48 of the optical fiber 40 and reaches the workpiece W. In addition, as Figure 7 As shown, the assist gas AG is ejected from the torch 28 so as to reach both the central portion CP and the peripheral portion PP.

[0043] Here, the laser output density of the first laser RL1 at the central portion CP is referred to as the first laser output density, and the laser output density of the second laser RL2 at the peripheral portion PP is referred to as the second laser output density. The first laser output density is greater than the second laser output density. Figure 4B Based on the principle of laser output density, the laser output density at the boundary portion BP between the central portion CP and the peripheral portion PP in the cover portion WCP is called the third laser output density. The third laser output density is smaller than the first laser output density and the second laser output density.

[0044] In addition, the first laser output density to the third laser output density are different at the upper surface WTP of the workpiece W and at the lower surface WBP of the workpiece W due to the expansion of the first laser RL1 and the second laser RL2. Specifically, the diameter of the central portion CP in the upper surface WTP of the workpiece W is smaller than the diameter of the central portion CP in the lower surface WBP of the workpiece W. The diameter DBT of the peripheral portion PP in the upper surface WTP of the workpiece W is smaller than the diameter DBB of the peripheral portion PP in the lower surface WBP of the workpiece W. Therefore, the first laser output density to the third laser output density in the upper surface WTP of the workpiece W is greater than the first laser output density to the third laser output density in the lower surface WBP of the workpiece W. In addition, from a microscopic point of view, even in the central portion CP, the peripheral portion PP and the boundary portion BP on the same plane, there are positions with high laser output density and positions with low laser output density, but the values ​​of the first laser output density to the third laser output density described in this embodiment are average values ​​of the central portion CP, the peripheral portion PP and the boundary portion BP over the entire area determined based on the imaginary optical path of the reflectors 46 and 48.

[0045] In the present embodiment, the first laser output density to the third laser output density are the average values ​​of the laser output density in the cross-sectional portion of the central portion CP, the cross-sectional portion of the peripheral portion PP, and the cross-sectional portion of the boundary portion BP when the center plane CTP between the upper surface WTP and the lower surface WBP of the workpiece W is set as a cross section. In addition, when the flashlight 28 opens the through hole PH while moving in the direction (Z direction) along the optical axis RZ, the average laser output density is defined as the first laser output density to the third laser output density. Figure 7 In the example, the diameter DCC of the cross section of the center plane CTP of the central part CP can be regarded as a cylindrical shape with the diameter being set to , and the outer diameter DBC and inner diameter DCC of the cross section of the center plane CTP of the peripheral part PP can be regarded as a tube shape with the outer diameter and inner diameter being set to .

[0046] The first laser output density and the second laser output density are determined by the output of at least one laser oscillator 30 (laser oscillator 30A), the offset DX (see Figure 4B ), and the distance LW between the focal position FP and the cover portion WCP. The control circuit 7 can control the position of at least one laser oscillator 30 and the flashlight 28 to adjust their values. In this embodiment, the first laser output density and the second laser output density meet the following conditions. [Condition 1] The first laser output density and the second laser output density are determined as the extent to which the central portion CP is perforated by the first laser RL1 and the second laser RL2. This is determined by whether the central portion CP is perforated when the laser RL having the first laser RL1 and the second laser RL2 is irradiated onto the workpiece W. In addition, the first laser output density and the second laser output density may be determined by considering that the workpiece W is also heated by the assist gas AG. [Condition 2] The first laser output density is the laser output density at which the first laser RL1 can heat the workpiece W to a degree that does not cause perforation of the outer side of the peripheral portion PP. This condition does not hold true if the output of the first laser RL1 is too strong and causes the outer side of the peripheral portion PP to melt or if the peripheral portion PP is too small. Fig. 8A As shown, if the first laser RL1 perforates the outer side of the peripheral portion PP, the root RT of the sputtered material SPT cannot be heated by the second laser RL2. As a result, the root RT of the sputtered material SPT solidifies and adheres to the workpiece MAW. The first laser output density is determined to suppress such a state. In addition, the first laser output density can also be determined by considering that the workpiece W is also heated by the auxiliary gas AG. [Condition 3] The second laser output density is a laser output density at which the second laser RL2 can heat the workpiece W to such an extent that the outer side of the peripheral portion PP is not perforated. This condition does not apply if the output of the second laser RL2 is too strong and the outer side of the peripheral portion PP is melted. This condition is also set to suppress the Fig. 8A In this case, the second laser output density may be determined by considering that the workpiece W is also heated by the first laser RL1 and the assist gas AG. [Condition 4] The second laser output density is a laser output density at which the second laser RL2 can heat the workpiece W to such an extent that the workpiece MEW melted by the first laser RL1 is scattered around the through hole PH by the gas (auxiliary gas AG) so that the sputtered matter SPT obtained does not adhere to and solidify on the workpiece MAW forming the through hole PH. If the second laser output density is too weak and the root RT of the sputtered matter SPT adheres to the workpiece MAW, then even if Figure 6 Even if the gas (assist gas AG) is blown in this way, the sputtered matter SPT cannot be removed from the workpiece MAW. In this case, the second laser output density may be determined by considering that the workpiece W is also heated by the first laser RL1 and the assist gas AG. [Condition 5] The second laser output density is a laser output density at which the second laser RL2 can heat the workpiece to such an extent that sputtering is not generated outside the peripheral portion PP. The second laser output density is not so high as to perforate the outside of the peripheral portion PP. However, if Figure 8B As shown, the second laser output density is lower than the laser output density at which the second laser RL2 melts a portion of the outer side of the peripheral portion PP and the viscosity of the melted workpiece MEW is such that it is scattered by the assist gas AG. Figure 8B In such a state, the root RT of the sputtered material SPT cannot be heated by the second laser RL2, and the root RT of the sputtered material SPT solidifies and adheres to the workpiece MAW. The second laser output density is determined to suppress such a state. In this case, it can also be considered that the workpiece W is also heated by the first laser RL1 and the auxiliary gas AG to determine the second laser output density.

[0047] Fig. 9 Flow chart of the laser perforation method of the embodiment. In step S1, the method blows oil OIL onto the workpiece W to generate a cover portion WCP covered with oil OIL on the workpiece W. In step S2, the method positions the flashlight 28 relative to the workpiece W in such a way that the central portion CP coincides with the target position on the workpiece W, so that the laser output density of the laser RL is a first laser output density at the central portion CP irradiated by the laser RL in the cover portion WCP, a second laser output density less than the first laser output density at the peripheral portion PP around the central portion CP in the cover portion WCP, and a third laser output density less than the first laser output density and the second laser output density at the boundary portion BP between the central portion CP and the peripheral portion PP in the cover portion WCP.

[0048] In step S3, the method sprays auxiliary gas AG from the flashlight 28 toward the central portion CP of the positioned workpiece W. In step S4, the method adjusts the offset DX between the optical axis Ax1 of the laser RL and the central axis Ax2 of the optical fiber 40 and the output of the laser oscillator 30A to meet [conditions 1] to [conditions 5], and irradiates the laser RL toward the cover portion WCP. Thus, according to the method, the workpiece W in the cover portion WCP can be melted by the first laser RL1 irradiated to the central portion CP, and the gas (auxiliary gas AG) can be blown to the molten workpiece MEW to scatter the molten workpiece MEW around the central portion CP, thereby opening a through hole PH in the cover portion WCP. Specifically, the method melts the workpiece W in the cover portion WCP by the first laser RL1 to such an extent that the outer side of the peripheral portion PP is not pierced.

[0049] In addition, the method heats the root RT of the spatter SPT of the workpiece W after scattering, which is in contact with the workpiece MAW to be processed and forming the through hole PH without the aid of oil OIL, by irradiating the second laser RL2 to the peripheral part PP. Specifically, the method heats the spatter SPT to the extent that the spatter SPT does not adhere to and solidify on the workpiece MAW to be processed by the second laser RL2. The method heats the workpiece W to the extent that the outer side of the peripheral part PP is not perforated by the second laser RL2. The method heats the workpiece W to the extent that the spatter SPT is not generated outside the peripheral part PP by the second laser RL2.

[0050] In step S5, after heating the root RT of the sputtered material SPT, the method moves the torch 28 blowing gas (auxiliary gas AG) from the outside of the root RT along a circle surrounding the root RT. At this time, in order to make the sputtered material SPT float, the method may also include actions such as raising and lowering the torch 28. In step S6, the method does not irradiate the laser RL, but blows gas (auxiliary gas AG) from the torch 28 to the periphery of the root RT. Thus, the method removes the sputtered material SPT from the workpiece MAW by blowing the gas (auxiliary gas AG) to the sputtered material SPT. <Verification Experiment> The following verification experiment was conducted to verify the effectiveness of the above-mentioned laser perforation method and the effectiveness of the above-mentioned conditions. The metal plate MP used in the experiment was SS400 steel with a thickness of 9.0 mm. The position of the flashlight 28 was adjusted so that the upper surface WTP of the workpiece W was located at a height of 8.5 mm from the focal position. At the focal position, the diameter DC of the area R1 through which the first laser RL1 passes (refer to Figure 7 ) is 0.234 mm, and the diameter DP of the area R2 through which the second laser RL2 passes (refer to Figure 7) is 0.806 mm. The diameter DCC of the central portion CP in the center plane CTP of the workpiece W is 1.066 mm, and the diameter DBC of the peripheral portion PP in the center plane CTP of the workpiece W is 1.492 mm. As a preliminary preparation, the optical axis Ax1 of the laser RL is set as Figure 4A Based on the positioning, the laser oscillator 30A is heated at 1000 W and a duty cycle of 15% for 0.1 seconds to open a punch hole. Thereafter, the offset DX between the optical axis Ax1 and the central axis Ax2 is changed so that the laser oscillator 30A outputs the laser RL at a duty cycle of 25% at 9000 W. In addition, the wind pressure of the auxiliary gas injected in step S3 is 0.4 MPa.

[0051] Fig.10 The image shows the through hole diameter (diameter) and the perforation mark when the perforation is performed while changing the output ratio between the first transmission section 42 and the second transmission section 44 corresponding to the offset DX. Fig.10 The image of the perforation mark and the through-hole diameter represent the result of the processing up to step S4. Samples 1 to 9 all generate through-holes with a hole diameter greater than 1.1 mm, and therefore meet [Condition 1]. Samples 5 to 9 all generate through-holes with a hole diameter greater than 1.4 mm. If the first laser output density is smaller than that of sample 4, it indicates an example that does not meet [Condition 3]. Sample 0 indicates an example that the second laser output density is substantially smaller, and therefore does not meet [Condition 4].

[0052] Samples 1 to 3 show an example in which the number of sputters SPT whose root RT is ideally heated increases as the value of the sample increases, and the number of sputters SPT decreases by removing these sputters by the auxiliary gas injected in step S3. In samples 1 to 3, [Conditions 1] to [Conditions 5] are present, indicating that [Condition 4] is present in a more ideal state as the value representing the sample increases. Sample 3 is a sample that has [Condition 4] in a more ideal state, and can reduce the strength of the root of the sputter SPT to the extent that the sputter SPT can be removed only by the wind pressure of the auxiliary gas injected in step S3.

[0053] In sample 4, the second laser output density increased and thus [Condition 5] was no longer met, resulting in Figure 8B In such a state, sputtering remains which cannot be removed by the assist gas injected in step S3. In addition, even in sample 4, sputtering cannot necessarily be removed as shown in the above experimental results, so the sputtering SPT can be completely removed by subsequently performing steps S5 and S6.

[0054] As described above, the fulfillment of [Conditions 1] to [Conditions 3] can be confirmed by comparing the diameter of the through hole actually bored with the diameter of the central portion CP and the diameter of the peripheral portion PP in the workpiece W that are theoretically required. Regarding the determination of whether or not the peripheral portion PP is located outside of [Conditions 2] and [Conditions 3], reasonable measurement errors and reasonable differences between theoretical values ​​and actual measured values ​​are taken into consideration. When it can be clearly stated that the peripheral portion PP is located outside even after taking such differences into consideration, it is determined that [Conditions 2] or [Conditions 3] are not fulfilled.

[0055] By comparing the amount of sputtered material when the second laser output density is substantially set to 0, the fulfillment of [Condition 4] can be confirmed by whether the amount of sputtered material is reduced. The situation where the second laser output density is substantially set to 0 here refers to the situation where the optical axis Ax1 of the laser RL output by the laser oscillator 30A is consistent with the central axis Ax2 of the optical fiber 40 and the laser RL is output with the same output. Or it refers to the situation where the output of the laser oscillator outputting the second laser RL2 is set to 0 without changing the output of the laser oscillator outputting the first laser RL1 when at least one laser oscillator 30 is composed of two laser oscillators, a laser oscillator outputting the first laser RL1 and a laser oscillator outputting the second laser RL2.

[0056] When the second laser output density increases stepwise even if the through-hole diameter does not change, whether the [condition 5] is met can be determined by whether the amount of sputtered matter increases compared to the amount of sputtered matter in the previous stage. <Features and Effects of Laser Perforation Method in the Present Embodiment> The laser drilling method and laser processing machine 1 of the present embodiment heat the root RT of the spatter SPT of the workpiece W after scattering, which is in contact with the workpiece MAW to be processed and forming the through hole PH without the aid of oil OIL, by irradiating the second laser RL2 to the peripheral portion PP. Therefore, the laser drilling method and laser processing machine 1 can suppress the solidification of the root RT, easily remove the spatter SPT, and improve the processing quality. <Modification> In the above-mentioned embodiment, at least one laser oscillator 30 is provided with a laser oscillator 30A that emits laser light, but the first laser light and the second laser light may be laser light emitted from different laser oscillators. In addition, the movement of the flashlight 28 shown in step S5 is not limited to the circle CIR, but may be an ellipse, and the flashlight 28 may be moved closer to the workpiece W or away from the workpiece W during rotation.

[0057] In the above embodiment, the laser processing machine 1 for processing a metal plate MP is exemplified, but it can also be applied to a laser processing machine for processing a pipe, etc. In this case, the laser head 20 can be rotated about rotation axes parallel to the X-axis and the Y-axis to enable three-dimensional processing.

[0058] In the present application, "having" and its derivatives are non-restrictive terms that describe the presence of constituent elements and do not exclude the presence of other constituent elements that are not described. This also applies to "having", "including" and their derivatives.

[0059] Phrases such as "~ member", "~ part", "~ element", "~ body" and "~ structure" can have multiple meanings such as a single part or a plurality of parts.

[0060] Ordinal numbers such as "first" and "second" are merely terms used to identify structures and do not have other meanings (such as a specific order, etc.). For example, the existence of a "first element" does not imply the existence of a "second element", nor does the existence of a "second element" imply the existence of a "first element".

[0061] Unless otherwise specified in the embodiments, the words "substantially", "about" and "approximately" indicating the degree may refer to a reasonable deviation without a significant change in the final result. All numerical values ​​recorded in this application may be interpreted as including the words "substantially", "about" and "approximately".

[0062] In the present application, the phrase "at least one of A and B" should be interpreted as including only A, only B, and both A and B.

[0063] It is obvious that various changes and modifications of the present invention can be made in view of the above disclosure. Therefore, the present invention can also be implemented in a method different from the specific disclosure of this application without departing from the scope of the present invention.

Claims

1. A laser perforation method, comprising: blowing oil onto a workpiece to generate a coating portion covered with the oil on the workpiece; irradiating the cover portion with laser light so that a laser output density of the laser light is a first laser output density at a central portion of the cover portion irradiated with the laser light, a second laser output density smaller than the first laser output density at a peripheral portion around the central portion of the cover portion, and a third laser output density smaller than the second laser output density at a boundary portion between the central portion and the peripheral portion of the cover portion; The first laser beam is irradiated onto the central portion to melt the workpiece in the cover portion, and a gas is blown onto the melted workpiece to scatter the melted workpiece around the central portion, thereby forming a through hole in the cover portion; and The second laser beam irradiated onto the peripheral portion heats the root of the sputtered material as the workpiece after scattering, which is in contact with the workpiece to be processed in which the through hole is formed without the oil.

2. The laser perforation method according to claim 1, wherein: The method further includes removing the sputtering from the workpiece by blowing a gas onto the sputtering after heating the root portion.

3. The laser perforation method according to claim 2, wherein: Removing the sputtering from the workpiece includes moving a torch from the outside of the root along a circle surrounding the root and blowing gas from the torch to the periphery of the root.

4. The laser perforation method according to claims 1 to 3, wherein: The sputtered material is heated by the second laser to a degree that the sputtered material does not adhere to and solidify on the workpiece.

5. The laser perforation method according to any one of claims 1 to 4, wherein: The workpiece is heated by the second laser to such an extent that the outer side of the peripheral portion is not perforated.

6. The laser perforation method according to claim 5, wherein: The workpiece in the covering portion is melted by the first laser to such an extent that the outer side of the peripheral portion is not perforated.

7. The laser perforation method according to claim 5 or 6, wherein: The workpiece is heated by the second laser to such an extent that sputtering is not generated outside the peripheral portion.

8. The laser perforation method according to claims 1 to 7, wherein: preparing an optical fiber including a first transmission portion, a second transmission portion provided around the first transmission portion, and a reflector provided between the first transmission portion and the second transmission portion, The first laser light and the second laser light are generated by emitting the laser light from one laser oscillator so that a part of the laser light enters the first transmission portion and another part of the laser light enters the second transmission portion.

9. A laser processing machine comprising: at least one laser oscillator configured to emit a first laser and a second laser; an optical fiber having a first end for receiving the first laser light and the second laser light from the at least one laser oscillator and a second end opposite to the first end, and including a first transmission portion for transmitting the first laser light, a second transmission portion disposed around the first transmission portion and transmitting the second laser light, and a reflector disposed between the first transmission portion and the second transmission portion; a lens disposed opposite to the second end of the optical fiber and configured to converge the first laser and the second laser transmitted from the optical fiber toward the workpiece; a flashlight having an opening for passage of light focused by the lens and of gas for blowing toward the workpiece; a moving mechanism configured to move the flashlight; a nozzle configured to spray oil toward the workpiece; a first pump configured to deliver the oil to the nozzle; a second pump configured to deliver the gas to the flashlight; and a control circuit configured to control the at least one laser oscillator, the first pump, the second pump, and the moving mechanism, The control circuit is configured to control the at least one laser oscillator and the second pump to irradiate the first laser and the second laser to the covering portion, and to blow the gas to the workpiece melted by the first laser to open a through hole in the covering portion after controlling the first pump to blow the oil to the workpiece to form a covering portion covered with the oil on the workpiece. The laser output density at the central portion of the covering portion irradiated by the first laser is a first laser output density, the laser output density at the peripheral portion of the covering portion irradiated by the second laser is a second laser output density less than the first laser output density, and the laser output density at the boundary portion between the central portion and the peripheral portion of the covering portion is a third laser output density less than the second laser output density.

10. The laser processing machine according to claim 9, wherein: The control circuit is configured to control the moving mechanism and the second pump so as to further blow gas to sputtered matter obtained by the gas being scattered around the through hole after the workpiece is melted by the first laser.

11. The laser processing machine according to claim 10, wherein: The control circuit is configured to control the moving mechanism and the second pump so that the flashlight moves along a circle surrounding the through hole and blows gas around the through hole.

12. The laser processing machine according to any one of claims 9 to 11, wherein: The second laser output density is a laser output density at which the second laser can heat the workpiece to such an extent that sputtering of the workpiece melted by the first laser and scattered around the through hole by the gas does not adhere to and solidify the workpiece forming the through hole.

13. The laser processing machine according to any one of claims 9 to 12, wherein: The first laser output density is a laser output density at which the first laser can heat the workpiece to such an extent that the outer side of the peripheral portion is not perforated. The second laser output density is a laser output density at which the second laser can heat the workpiece to such an extent that the outer side of the peripheral portion is not perforated.

14. The laser processing machine according to claim 13, wherein: The second laser output density is a laser output density at which the second laser can heat the workpiece to such an extent that sputtering is not generated outside the peripheral portion.

15. The laser processing machine according to any one of claims 9 to 14, wherein: The at least one laser oscillator comprises a laser oscillator for emitting laser light, The emission direction of the laser light of the one laser oscillator is adjusted so that a part of the laser light enters the first transmission portion and another part of the laser light enters the second transmission portion.

Images