Laser perforation method and laser processing machine

Abstract

A laser drilling method and a laser processing machine are provided. The laser drilling method includes: forming a coating covered with oil on a workpiece; irradiating the coating with laser light so that the laser output density is a first laser output density at a central portion of the coating irradiated with the laser light, a second laser output density less than the first laser output density at a peripheral portion surrounding the central portion of the coating, and a third laser output density less than the second laser output density at a boundary portion between the central portion and the peripheral portion of the coating; melting the workpiece within the coating by irradiating the central portion with the first laser light, blowing gas onto the molten workpiece to cause the molten workpiece to scatter around the central portion, thereby forming a through hole in the coating; and heating the base of the scattered workpiece, which is in contact with the workpiece in which the through hole is formed without the aid of oil, by irradiating the peripheral portion with a second laser light.

Description

Technical Field

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

[0002] Most laser processing machines use a single laser source (e.g., Patent Document 1). However, Patent Document 2 describes a machine tool that controls the intensity of the laser beam in the center and peripheral regions to achieve high-quality drilling with minimal spatter adhesion, tailored to the thickness of the workpiece. Patent Document 3 discloses a technique for suppressing the adhesion of spatter generated by drilling by applying oil before drilling.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 8-192283

[0004] Patent Document 2: International Publication No. 2017 / 134964

[0005] Patent Document 3: Japanese Patent Application Laid-Open No. 2000-84686

[0006] Even if oil is applied before the perforation, the root of the spatter close to the through hole is not directly connected to the component of the workpiece by means of oil. If the root cools and solidifies during the perforation, the removal of the spatter becomes difficult. Summary of the Invention

[0007] The technology disclosed in this application aims 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.

[0008] A first embodiment of the laser drilling method of the present invention involves blowing oil onto a workpiece to form an oil-covered coating on the workpiece. The method involves irradiating the coating with a laser beam such that the laser output density is a first laser output density in the central portion of the coating, which is irradiated by the laser beam; a second laser output density, which is less than the first laser output density, in the peripheral portion surrounding the central portion of the coating; and a third laser output density, which is less than the second laser output density, at the boundary between the central portion and the peripheral portion of the coating. The method involves melting the workpiece within the coating by irradiating the central portion with the first laser beam, and blowing gas onto the molten workpiece to cause the molten workpiece to scatter around the central portion, thereby creating a through hole in the coating. The method involves heating the base of the scattered workpiece spatter, which contacts the workpiece in which the through hole is formed without the aid of oil, by irradiating the peripheral portion with a second laser beam.

[0009] According to a second aspect of the present invention, the laser drilling method of the first aspect includes removing spatters from the workpiece by blowing gas onto the spatters after heating the root portion. Furthermore, the direction in which the gas is blown onto the spatters is preferably different from the direction in which the gas is blown to disperse the molten workpiece.

[0010] According to a third aspect of the present invention, in the laser drilling method of the second aspect, removing the spatter from the workpiece includes moving the torch along a circle surrounding the root from outside the root and blowing gas from the torch to the periphery of the root.

[0011] According to a fourth embodiment of the present invention, in the laser perforation method of any one of the first to third embodiments, the method includes heating the sputters by a second laser to the extent that the sputters do not adhere to and solidify on the workpiece to be processed. In the case where a plurality of sputters are generated by the first laser, the sputters may also be heated by a second laser to the extent that at least one of the plurality of sputters does not adhere to and solidify on the workpiece to be processed. In this case, it is preferred that the sputters are heated by the second laser to the extent that at least one of the plurality of sputters is scattered by the gas of the second or third embodiment. In addition, it is more preferred that the sputters are heated by the second laser to the extent that all of the sputters in the plurality of sputters are scattered by the gas of the second or third embodiment. It is further preferred that the sputters are heated by the second laser to the extent that all of the sputters in the plurality of sputters are not adhere to and solidify on the workpiece to be processed.

[0012] 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.

[0013] According to a sixth aspect of the present invention, in the laser drilling method of the fifth aspect, the workpiece in the covering portion is melted by the first laser light to such an extent that the outer side of the peripheral portion is not drilled.

[0014] 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 light to such an extent that sputtering is not generated outside the peripheral portion.

[0015] 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 including a first transmission portion, a second transmission portion disposed around the first transmission portion, and a reflector disposed between the first and second transmission portions. The method further includes emitting laser light from a laser oscillator such 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.

[0016] A ninth embodiment of the present invention comprises a laser processing machine comprising 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. The at least one laser oscillator is configured to emit a first laser beam and a second laser beam. The optical fiber has a first end for receiving the first and second laser beams from the at least one laser oscillator, and a second end opposite the first end. The optical fiber includes a first transmitting portion for transmitting the first laser beam, a second transmitting portion disposed around the first transmitting portion for transmitting the second laser beam, and a reflector disposed between the first and second transmitting portions. The lens is disposed opposite the second end of the optical fiber and is configured to converge the first and second laser beams transmitted from the optical fiber toward a workpiece. The flashlight has an opening for passing the light converged by the lens and the gas for blowing toward the workpiece. The moving mechanism is configured to move the flashlight. The nozzle is configured to spray oil toward the workpiece. The first pump is configured to supply oil to the nozzle. The second pump is configured to supply 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, after controlling a first pump to blow oil onto a workpiece to form an oil-covered coating on the workpiece, control at least one laser oscillator and a second pump to irradiate the coating with a first laser beam and a second laser beam, and blow gas onto the workpiece melted by the first laser beam to create a through-hole in the coating. The laser output density at a central portion of the coating irradiated by the first laser beam is a first laser output density, the laser output density at a peripheral portion of the coating irradiated by the second laser beam is a second laser output density that is lower than the first laser output density, and the laser output density at a boundary between the central portion and the peripheral portion of the coating is a third laser output density that is lower than the second laser output density.

[0017] According to a tenth aspect of the present invention, the laser processing mechanism of the ninth aspect is configured such that the control circuit controls the moving mechanism and the second pump to further blow gas toward the sputtering generated by the gas scattering around the through-hole after the workpiece is melted by the first laser beam. Furthermore, the direction in which the gas is blown toward the sputtering is preferably different from the direction in which the gas is blown to scatter the melted workpiece.

[0018] According to the eleventh aspect of the present invention, in the laser processing mechanism of the tenth aspect, 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.

[0019] According to the twelfth aspect of the present invention, the laser processing mechanism of any one of the ninth to eleventh aspects 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 resulting from the workpiece being melted by the first laser and scattered around the through-hole by the gas does not adhere to and solidify on the workpiece being processed to form the through-hole. In the case where multiple sputtering objects are generated by the first laser, the second laser output density may 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 workpiece being processed. 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 by the gas of the second or third aspect. Furthermore, 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 by the gas of the second or third aspect. 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 materials do not adhere to and solidify on the workpiece.

[0020] According to the thirteenth embodiment of the present invention, the laser processing mechanism of any one of the ninth to twelfth embodiments becomes 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 a second laser output density at which the second laser can heat the workpiece to a degree without perforating the outer side of the peripheral portion.

[0021] 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 sputters are not generated outside the peripheral portion.

[0022] According to a fifteenth aspect of the present invention, in the laser processing machine according to any one of the ninth to fourteenth aspects, at least one laser oscillator includes a single laser oscillator that emits laser light. The laser processing mechanism is configured to adjust the emission direction of the laser light from the single 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.

[0023] The laser drilling method of the first embodiment heats the root of the sputtered material using a second laser beam having a second laser output density less than the output density of the first laser beam used to create the through-hole. This prevents the root of the sputtered material from adhering to the workpiece surrounding the through-hole, and facilitates removal of the sputtered material. The laser processing machine of the ninth embodiment heats the root of the sputtered material using a second laser beam having a second laser output density.

[0024] 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.

[0025] In the laser drilling method of the third aspect and the laser processing machine of the eleventh aspect, gas can be blown from the outside of the sputtered material toward the root portion, so that more sputtered material can be removed by the gas.

[0026] In the laser drilling method of the fourth aspect and the laser processing machine of the twelfth aspect, the sputtered matter that has not adhered to the root can be easily removed by gas.

[0027] If the outside of the heated area irradiated by the second laser is perforated, the root of the resulting sputtering cannot be directly heated by the second laser, and the root cools and sticks. In the fifth embodiment of the laser perforation method, this risk is reduced because the workpiece is heated by the second laser to a degree that the outside of the heated area is not perforated. In addition, if the second laser is weak, or the outside of the heated area is perforated by the first laser because the heated area is smaller than the perforation area, the same problem will arise. In the sixth embodiment of the laser perforation method, this risk is further reduced because the workpiece is heated by the first laser to a degree that the outside of the heated area is not perforated. In the thirteenth embodiment of the laser processing machine, the above-mentioned risk is reduced because the workpiece is heated by the first laser and the second laser to a degree that the outside of the heated area is not perforated.

[0028] Even if drilling is not performed outside the heated area, if a portion of the periphery of the through-hole outside the area irradiated by the second laser is melted by the second laser and dispersed by the assist gas, the root of the sputtered material thus formed cannot be directly heated by the second laser, and the root will cool and adhere. In the laser drilling method of the seventh aspect and the laser processing machine of the fourteenth aspect, this risk is reduced because the second laser heats the workpiece to a level that prevents sputtering from occurring outside the processing area.

[0029] The laser drilling method of the eighth aspect and the laser processing machine of the fifteenth aspect generate the first laser beam and the second laser beam using a single laser oscillator, and thus can reduce manufacturing costs.

[0030] 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 root solidification of sputtering generated by drilling and improving the processing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a diagram showing the external appearance structure of a laser processing machine according to an embodiment.

[0032] Figure 2This is a cross-sectional view of a laser head of a laser processing machine according to an embodiment.

[0033] Figure 3 It is a diagram showing the internal structure of an optical fiber according to an embodiment.

[0034] Figure 4A An output example of laser light according to the embodiment is shown.

[0035] Figure 4B An output example of laser light according to the embodiment is shown.

[0036] Figure 4C An output example of laser light according to the embodiment is shown.

[0037] Figure 5 It is a schematic diagram showing a perforation method according to an embodiment.

[0038] Figure 6 It is another schematic diagram showing the perforation method according to the embodiment.

[0039] Figure 7 This is a schematic diagram of laser light emitted from a flashlight according to an embodiment.

[0040] Figure 8A This is an example of a non-preferred perforation method according to the embodiment.

[0041] Figure 8B This is an example of a non-preferred perforation method according to the embodiment.

[0042] Figure 9 1 is a flowchart showing a punching method according to an embodiment.

[0043] Figure 10 Represents the results of the validation experiment. DETAILED DESCRIPTION

[0044] 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.

[0045] <Implementation Method>

[0046] <Structure of Laser Processing Machine 1>

[0047] 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, Y-axis, and Z-axis will be referred to as the X-direction, Y-direction, and Z-direction, respectively. Figure 1As shown, a 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 device 6. The laser processing machine 1 is a device for processing a metal plate MP mounted on the base 10. Examples of the metal plate MP include mild steel, SUS (Steel Use Stainless Steel), aluminum steel, brass, and copper. The metal plate MP may also be referred to as a workpiece W. The base 10 may also include a plurality of elongated projections. A pair of first guide rails 11 are mounted along the Y direction at both ends of the base 10, and a column 12 is mounted on the first guide rails 11 so as to be movable on the first guide rails 11. The column 12 moves on the first guide rail 11 by a driving force of a driving device D1 such as a motor provided on one of the first guide rail 11 and the column 12 .

[0048] A second guide rail 13 is provided on the column 12 along the Y-axis, which is perpendicular to the X-axis. 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 using, for example, the driving force of a drive device D2, such as a motor, provided on either the second guide rail 13 or the saddle 14. Although not shown, the column 12 may also be covered with a corrugated cover. A laser head 20 is mounted on the saddle 14 so as to be movable in the Z-direction, which is perpendicular to the X- and Y-axes. The laser head 20 moves on the saddle 14 using, for example, the driving force of a drive device D3, such as a motor, provided on either the saddle 14 or the laser head 20. The laser head 20 is configured to process the metal plate MP on the base 10. The laser head 20 includes 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.

[0049] The nozzle 15 is configured to spray oil toward the workpiece W before the laser head 20 described later irradiates the workpiece W. The first pump 16 is configured to deliver oil to the nozzle 15. The oil is stored in an oil tank (not shown). Figure 1, an example is given in which the nozzle 15 and the first pump 16 are mounted on the saddle 14. However, the nozzle 15 and the first pump 16 may also be mounted on the base 10. At least one laser oscillator 30 outputs laser light for processing the metal plate MP. An optical fiber 40 retractably connects the at least one laser oscillator 30 and the laser head 20 to supply the laser light 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 light from the at least one laser oscillator 30, and a second end 40b opposite the first end 40a. The numerical control device 6 includes a control circuit 7 including a hardware processor, a memory, and the like. The control circuit 7 is configured to control the at least one laser oscillator 30, the drive devices D1 to D3, and the first pump 16 to process the metal plate MP. In the following embodiments, the drive devices D1 to D3 are collectively referred to as a transfer mechanism TM. The transfer mechanism TM is configured to move the flashlight 28.

[0050] 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 is shown, which is obtained by cutting the laser head 20 along a cutting plane passing through the optical axis RZ of the laser light irradiated from the flashlight 28, to explain the optical system of the laser head 20. Figure 2 The laser head 20 includes 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 used to attach the second end 40b of the optical fiber 40 to the laser head 20. The reflector 26 reflects the laser light output from the connector 25 toward the lower unit 23.

[0051] 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 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 transmitting laser light is formed between the upper unit 22, the head body 21, the lower unit 23, and the flashlight 28.

[0052] 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 ), is delivered to the flashlight 28 through the gas supply passage 19. The flashlight 28 includes 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.

[0053] Figure 3 : This is a diagram of the internal structure of the optical fiber 40 according to the embodiment. The optical fiber 40 includes a first transmissive portion 42, a second transmissive portion 44, a reflector 46, and an additional reflector 48. The first transmissive portion 42 is cylindrical and is configured to transmit laser light. The reflector 46 is a tubular member that covers the outer periphery of the first transmissive portion 42 and is configured to reflect laser light at the interface with the first transmissive portion 42. The second transmissive portion 44 is a tubular member that covers the outer periphery of the reflector 46 and is configured to transmit laser light. In other words, the second transmissive portion 44 is arranged around the first transmissive portion 42. The reflector 46 is arranged between the first transmissive portion 42 and the second transmissive portion 44. The reflector 46 is configured to reflect laser light at the interface with the second transmissive portion 44. The additional reflector 48 is a tubular member that covers the outer periphery of the second transmissive portion 44 and is configured to reflect laser light at the interface with the second transmissive portion 44.

[0054] Figures 4A to 4C FIG. 1 shows an output example of the laser RL according to the embodiment. In this embodiment, at least one laser oscillator 30 includes a laser oscillator 30A for emitting the laser 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 .

[0055] Figures 4A to 4C The right side of the figure shows the laser output density of the optical fiber 40. 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, one near the central axis Ax2 of the optical fiber 40 and the other near the center of the second transmission portion 44. Moreover, the peak near the central axis Ax2 of the optical fiber 40 is larger than the peak near the center of the second transmission portion 44. Figure 4C In the embodiment, 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 .

[0056] 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. Specifically, the emission direction of the laser light RL from one laser oscillator 30A is adjusted so that a portion of the laser light RL enters the first transmission section 42 and another portion of the laser light RL enters the second transmission section 44. In other words, by emitting the laser light RL from one laser oscillator 30A so that a portion of the laser light RL enters the first transmission section 42 and another portion of the laser light RL enters the second transmission section 44, first laser light RL1 and second laser light RL2 are generated. In the following embodiments, the laser light output from the first transmission section 42 is referred to as the first laser light RL1, and the laser light output from the second transmission section 44 is referred to as the second laser light RL2. Thus, at least one laser oscillator 30 is configured to emit the first laser light RL1 and the second laser light RL2. The first transmission section 42 transmits the first laser light RL1, and the second transmission section 44 transmits the second laser light RL2.

[0057] Figure 5 Schematic diagram showing a punching method according to an embodiment. Figure 5As shown, the control circuit 7 is configured to control the first pump 16 to blow oil OIL onto the workpiece W, thereby forming a coating portion WCP covered with the oil OIL on the workpiece W. Thereafter, the control circuit 7 controls at least one laser oscillator 30 and a second pump 17 to irradiate the coating portion WCP with a first laser beam RL1 and a second laser beam RL2, and to blow gas (assistant gas AG) onto the workpiece MEW melted by the first laser beam RL1, thereby forming a through-hole PH in the workpiece W. In particular, the control circuit 7 is configured to control the second laser beam RL2 to heat the root RT of the sputtering material SPT. When the gas (assistant gas AG) is blown onto the melted workpiece MEW, the sputtering material SPT is scattered around the through-hole PH. The melted workpiece MEW is a workpiece W whose viscosity has been reduced by heating to a level that allows it to be scattered by the assist gas AG. The root RT refers to the portion of the sputtering material SPT that contacts the workpiece MAW where the through-hole PH is formed, without the aid of the oil OIL.

[0058] Figure 6 : is another schematic diagram showing a punching 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 resulting sputtering SPT is scattered around the through hole PH due to the gas (e.g., auxiliary gas AG). 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 the moving mechanism TM and the second pump 17 to move the flashlight 28 along the circle CIR surrounding the through-hole PH and blow gas (eg, assist gas AG) around the through-hole PH.

[0059] Figure 7 Schematic diagram of laser RL from flashlight 28 in the 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.

[0060] 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 referred to as a third laser output density. The third laser output density is lower than the first laser output density and the second laser output density.

[0061] Furthermore, the first through third laser output densities differ between the top surface WTP and bottom surface WBP of the workpiece W due to the spread of the first laser beam RL1 and the second laser beam RL2. Specifically, the diameter of the central portion CP of the top surface WTP of the workpiece W is smaller than the diameter of the central portion CP of the bottom surface WBP of the workpiece W. The diameter DBT of the peripheral portion PP of the top surface WTP of the workpiece W is smaller than the diameter DBB of the peripheral portion PP of the bottom surface WBP of the workpiece W. Therefore, the first through third laser output densities at the top surface WTP of the workpiece W are greater than the first through third laser output densities at the bottom surface WBP of the workpiece W. Furthermore, microscopically, even within the central portion CP, peripheral portion PP, and boundary portion BP on the same plane, there are locations with high and locations with low laser output density. However, the values ​​of the first through third laser output densities described in this embodiment are average values ​​across the entire area of ​​the central portion CP, peripheral portion PP, and boundary portion BP, determined based on the hypothetical optical paths of the reflectors 46 and 48.

[0062] In this 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 along the optical axis RZ (Z direction), 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 the diameter, 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 the outer diameter and inner diameter.

[0063] 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 FIG. 1 ) between the optical axis Ax1 of the laser RL and the central axis Ax2 of the optical fiber 40. 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 of the 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.

[0064] [Condition 1] The first and second laser output densities are determined by the extent to which the center portion CP is perforated by the first and second laser beams RL1 and RL2. This is determined by determining whether the center portion CP is perforated when the workpiece W is irradiated with the laser beams RL comprising the first and second laser beams RL1 and RL2. Alternatively, the first and second laser output densities may be determined by considering that the workpiece W is also heated by the assist gas AG.

[0065] [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. Figure 8A As shown, if the first laser beam RL1 perforates the outer portion of the peripheral portion PP, the second laser beam RL2 cannot heat the root RT of the sputtered material SPT. Consequently, the root RT of the sputtered material SPT solidifies and adheres to the workpiece MAW. The first laser output density is determined to suppress this state. Furthermore, the first laser output density can also be determined by considering that the workpiece W is also heated by the assist gas AG.

[0066] [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 hold true 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 following situations: Figure 8A In this case, the second laser output density can be determined by considering that the workpiece W is also heated by the first laser RL1 and the assist gas AG.

[0067] [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 (assistant gas AG) so that the sputtered matter SPT 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 manner, 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.

[0068] [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 this state, the second laser beam RL2 cannot heat the root RT of the sputtered material SPT, causing it to solidify and adhere to the workpiece MAW. The second laser output density is determined to suppress this state. In this case, the second laser output density can also be determined by considering that the workpiece W is also heated by the first laser beam RL1 and the assist gas AG.

[0069] Figure 9 This is a flow chart of a laser perforation method according to an embodiment. In step S1, the method applies oil OIL to a workpiece W, thereby forming a cover portion WCP covered with the oil OIL. In step S2, the method positions the flashlight 28 relative to the workpiece W so that the central portion CP aligns with a target position on the workpiece W. This allows the laser output density of the laser RL to be a first laser output density at the central portion CP of the cover portion WCP, which is illuminated by the laser RL. A second laser output density is lower than the first laser output density at the peripheral portion PP surrounding the central portion CP of the cover portion WCP. Finally, a third laser output density is lower than the first and second laser output densities at the boundary portion BP between the central portion CP and the peripheral portion PP of the cover portion WCP.

[0070] In step S3, the method sprays assist 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 then irradiates the cover portion WCP with the laser RL. Thus, according to this method, the workpiece W within the cover portion WCP is melted by the first laser RL1 irradiated onto the central portion CP, and the gas (assist gas AG) is blown onto the melted workpiece MEW, causing the melted workpiece MEW to scatter around the central portion CP, thereby forming a through hole PH in the cover portion WCP. Specifically, the method melts the workpiece W within the cover portion WCP using the first laser RL1 to a degree that does not perforate the outer portion PP.

[0071] Furthermore, this method heats the root RT of the spatter SPT of the workpiece W, which is scattered and in contact with the workpiece MAW where the through-hole PH is formed, by irradiating the peripheral portion PP with the second laser beam RL2. Specifically, this method heats the spatter SPT with the second laser beam RL2 to a level that prevents the spatter SPT from adhering to and solidifying the workpiece MAW. This method heats the workpiece W with the second laser beam RL2 to a level that prevents perforation outside the peripheral portion PP. This method heats the workpiece W with the second laser beam RL2 to a level that prevents spatter SPT from forming outside the peripheral portion PP.

[0072] In step S5, after heating the root RT of the sputtered material SPT, the method moves the torch 28, which blows gas (assist gas AG), from outside the root RT along a circle surrounding the root RT. This may also include raising and lowering the torch 28 to lift the sputtered material SPT. In step S6, the method does not irradiate the sputtered material SPT with laser light RL, but instead blows gas (assist gas AG) from the torch 28 toward the periphery of the root RT. This method removes the sputtered material SPT from the workpiece MAW by blowing the gas (assist gas AG) onto the sputtered material SPT.

[0073] <Verification Experiment>

[0074] In order to verify the effectiveness of the above-mentioned laser perforation method and the effectiveness of the above-mentioned conditions, the following verification experiment was conducted. 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 top surface WTP of the workpiece W was 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 beam RL1 passed (refer to Figure 7 ) is 0.234 mm, and the diameter DP of the region R2 through which the second laser RL2 passes (refer to Figure 7) is 0.806mm. The diameter DCC of the central portion CP in the center plane CTP of the workpiece W is 1.066mm, and the diameter DBC of the peripheral portion PP in the center plane CTP of the workpiece W is 1.492mm. As a preliminary preparation, the optical axis Ax1 of the laser RL is set as Figure 4A With this positioning, laser oscillator 30A is heated at 1000 W and a 15% duty cycle for 0.1 seconds to create a punch hole. Thereafter, the offset DX between optical axis Ax1 and central axis Ax2 is varied, so that laser oscillator 30A outputs laser light RL at 9000 W and a 25% duty cycle. The assist gas pressure injected in step S3 is set to 0.4 MPa.

[0075] Figure 10 The image shows the hole diameter (diameter) and the hole trace when the hole is punched while changing the output ratio between the first transmission part 42 and the second transmission part 44 according to the offset DX. Figure 10 The image of the perforation mark and the through-hole diameter represent the results of the processing up to step S4. Samples 1 to 9 all generated through-holes with a diameter greater than 1.1 mm, thus meeting [Condition 1]. Samples 5 to 9 all generated through-holes with a diameter greater than 1.4 mm. Considering that the first laser output density is lower than that of Sample 4, this indicates that [Condition 3] is not met. Sample 0 is an example in which the second laser output density is substantially lower, thus not meeting [Condition 4].

[0076] Samples 1 to 3 show examples where the number of sputters SPT, whose root RT is ideally heated, increases as the sample value increases. The number of sputters SPT decreases as the assist gas injected in step S3 removes these sputters. Samples 1 to 3 meet [Conditions 1] to [Conditions 5], indicating that [Condition 4] is met in a more ideal state as the sample value increases. Sample 3 is a sample that meets [Condition 4] in a more ideal state, reducing the strength of the root of the sputters SPT to a level where the sputters SPT can be removed solely by the wind pressure of the assist gas injected in step S3.

[0077] In sample 4, the second laser output density increases, and thus [Condition 5] is no longer satisfied, 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 is not necessarily removed as shown in the above experimental results. Therefore, the sputtering SPT can be completely removed by subsequently performing steps S5 and S6.

[0078] As described above, the fulfillment of [Conditions 1] to [Conditions 3] can be confirmed by comparing the diameter of the actually drilled through-hole with the theoretically required diameters of the central portion CP and the peripheral portion PP of the workpiece W. Whether or not a hole is outside the peripheral portion PP referred to in [Conditions 2] and [Conditions 3] is determined by taking into account reasonable measurement errors and reasonable differences between theoretical and measured values. If, even after taking such differences into account, it can be clearly determined that the hole is outside the peripheral portion PP, then [Condition 2] or [Condition 3] is not fulfilled.

[0079] Comparing the amount of sputtered material with that obtained when the second laser output density is substantially set to 0 can confirm the fulfillment of [Condition 4] by determining whether the amount of sputtered material has decreased. The situation in which the second laser output density is substantially set to 0 refers to a situation in which the optical axis Ax1 of the laser light RL output by the laser oscillator 30A is aligned with the central axis Ax2 of the optical fiber 40, and the laser light RL is output at the same output. Alternatively, when at least one laser oscillator 30 is composed of two laser oscillators, one that outputs the first laser light RL1 and one that outputs the second laser light RL2, the output of the laser oscillator that outputs the second laser light RL2 is set to 0 without changing the output of the laser oscillator that outputs the first laser light RL1.

[0080] When the second laser output density increases stepwise even if the through-hole diameter does not change, whether the amount of sputtered matter increases relative to the amount of sputtered matter in the previous stage can be determined to determine whether [Condition 5] is met.

[0081] <Features and Effects of the Laser Perforation Method in This Embodiment>

[0082] The laser drilling method and laser processing machine 1 of this embodiment heats the root RT of the spatter SPT, which is scattered from the workpiece W and contacts the workpiece MAW where the through-hole PH is formed, without the aid of oil OIL, by irradiating the peripheral portion PP with the second laser beam RL2. Consequently, the laser drilling method and laser processing machine 1 can suppress solidification of the root RT, facilitate removal of the spatter SPT, and improve processing quality.

[0083] <Modification>

[0084] In the above embodiment, at least one laser oscillator 30 includes a single laser oscillator 30A that emits laser light. However, the first laser light and the second laser light may be emitted from different laser oscillators. Furthermore, the movement of the flashlight 28 shown in step S5 is not limited to a circle CIR but may also be an ellipse. Furthermore, the flashlight 28 may be moved toward or away from the workpiece W while rotating.

[0085] 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.

[0086] In this application, "having" and its derivatives are non-restrictive terms that indicate the presence of a component and do not exclude the presence of other components not described. This also applies to "having", "including" and their derivatives.

[0087] Phrases such as "~ member", "~ part", "~ element", "~ body" and "~ structure" can have multiple meanings such as a single part or a plurality of parts.

[0088] Ordinal numbers such as "first" and "second" are merely terms used to identify structures and do not have any other meanings (such as a specific order). 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."

[0089] Unless otherwise specified in the embodiments, the words "substantially," "about," and "approximately" when used to indicate a degree of effect may indicate that the final result does not vary significantly within a reasonable range. All numerical values ​​described in this application may be interpreted as including the words "substantially," "approximately," and "approximately."

[0090] In this application, the phrase "at least one of A and B" should be interpreted as including only A, only B, and both A and B.

[0091] 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 manner different from the specific disclosure of this application without departing from the scope of the present invention.

Claims

1. A laser processing machine comprising: at least one laser oscillator configured to emit a first laser beam and a second laser beam; an optical fiber having a first end for receiving the first laser beam and the second laser beam 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 beam, a second transmission portion provided around the first transmission portion and transmitting the second laser beam, and a reflector provided 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 light and the second laser light transmitted from the optical fiber toward a workpiece; a flashlight having an opening for passage of light focused by the lens and 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 covering portion with the first laser beam and the second laser beam after controlling the first pump to blow the oil onto the workpiece to form a covering portion covered with the oil, and to blow the gas onto the workpiece melted by the first laser beam to form 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 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 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 a third laser output density smaller than the second laser output density.

2. The laser processing machine according to claim 1, wherein The control circuit is configured to control the moving mechanism and the second pump so as to further blow gas onto sputtered matter generated by the gas and scattered around the through hole after the workpiece is melted by the first laser.

3. The laser processing machine according to claim 2, 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.

4. The laser processing machine according to any one of claims 1 to 3, wherein The second laser output density is a laser output density at which the second laser can heat the workpiece to 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.

5. The laser processing machine according to any one of claims 1 to 3, 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.

6. The laser processing machine according to claim 5, 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.

7. The laser processing machine according to any one of claims 1 to 3, wherein The at least one laser oscillator comprises a laser oscillator that emits laser light, The emission direction of the laser light from the one laser oscillator is adjusted 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.

8. A laser perforation method, used in the laser processing machine according to any one of claims 1 to 7, comprising: blowing oil onto a workpiece to generate a coating 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; Melting the workpiece in the cover portion by irradiating the central portion with a first laser beam, and blowing gas 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 spattered material, which is the workpiece after scattering and contacts the workpiece in which the through hole is formed, without the aid of the oil.

9. The laser perforation method according to claim 8, wherein: The method further includes removing the spatter from the workpiece by blowing gas onto the spatter after heating the root portion.

10. The laser perforation method according to claim 9, wherein: Removing the spatter 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.

11. The laser perforation method according to any one of claims 8 to 10, 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.

12. The laser perforation method according to any one of claims 8 to 10, wherein: The workpiece is heated by the second laser to such an extent that the outer side of the peripheral portion is not perforated.

13. The laser perforation method according to claim 12, 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.

14. The laser perforation method according to claim 12, wherein: The workpiece is heated by the second laser to such an extent that sputtering is not generated outside the peripheral portion.

15. The laser perforation method according to any one of claims 8 to 10, wherein: An optical fiber is prepared, the 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 laser light is emitted from one 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.

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