LASER PROCESSING METHOD, PROCESSING PROGRAM AND CONTROL DEVICE

Abstract

The present invention is a laser processing method for creating a blind hole by emitting a laser beam onto a workpiece, thereby removing a portion of the workpiece. In the laser processing method, the following steps are repeated: a first irradiation step in which a laser beam is emitted and an oxidizing gas is expelled to the irradiation point, and a second irradiation step following the first irradiation step in which a laser beam is emitted and an inert gas is expelled to the irradiation point, until the depth of the blind hole reaches a predetermined depth.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a laser machining method that forms a blind hole by irradiating a laser beam onto a workpiece and removing a part of the workpiece. GENERAL STATE OF THE ART

[0002] Laser machines such as laser cutting machines and laser welding machines transmit a processing laser beam output from a laser oscillator to irradiate a workpiece, and move the processing laser beam and the workpiece relative to each other, thereby performing predetermined processing. When processing a thick metal plate using such a laser machine, it is known that the processing is performed while ejecting an oxidizing gas such as oxygen as an auxiliary gas to a laser beam irradiation point to deepen the penetration depth at the irradiation point.

[0003] When laser processing is performed with the oxidizing gas discharged, an oxidation reaction between the metal material of the metal plate and the oxygen contained in the oxidizing gas is utilized to promote heat generation, thereby achieving deeper penetration. On the other hand, since the penetration depth is limited as the thickness of the metal plate to be processed increases or the processing speed increases, processing can become difficult.

[0004] As laser devices intended to improve the problems described above, there are, for example, those disclosed in Patent Literature Example 1 and Patent Literature Example 2. In the laser processing devices disclosed in these literature examples, immediately before irradiating a laser beam to perform main processing, a laser beam for performing pre-processing is irradiated while discharging an inert gas to flatten the surface of a workpiece, thereby increasing the absorption rate of the laser beam for the main processing. PRIOR ART PATENT LITERATURE DOCUMENTS Patent Literature Example 1: Japanese Patent Laid-Open No. H11-104879 Patent Literature Example 2: Japanese Patent Laid-Open No. 2001-214986 BRIEF DESCRIPTION OF THE INVENTION TASK THAT THE INVENTION INTENDED TO SOLVE

[0005] The prior art described above allows for the machining of a thicker workpiece compared to a case where no pre-machining is performed. However, when machining a thick workpiece requiring multiple cutting or drilling passes, or when machining a concave portion such as a blind hole or groove, an oxide film will remain on the surface of the workpiece due to an oxidation reaction that occurs during laser beam machining.

[0006] Such an oxide film has a melting point higher than that of metal materials of a base material and is formed when molten metal cools and solidifies, resulting in a rough surface that causes a decrease in the absorption rate of the laser beam. Therefore, in a case where laser processing is repeatedly performed on the same portion in multiple passes, there is a problem that a desired penetration depth (machining depth) cannot be achieved due to the oxide film remaining on the workpiece surface machined in the last pass.

[0007] In contrast, in conventional laser machining, laser machining is performed with the discharge of an inert gas as a pre-processing step for machining using an oxidizing gas as an auxiliary gas, or laser machining is performed using a mixture of an oxidizing gas and an inert gas to prevent the oxide film from remaining after the above-described machining. However, since an auxiliary gas containing an oxidizing gas is used in both cases during the final machining step, the problem arises that the residue of an oxide film on the surface after machining is inevitable.

[0008] Under the circumstances, there is a need for a laser machining technology for forming a blind hole, which can obtain a sufficient machining depth and a bottom without any residual oxide film after machining when drilling a hole leaving a bottom or a concave portion (a blind hole) in multiple passes. MEANS TO SOLVE THE PROBLEM

[0009] According to one aspect of the present invention, a laser machining method in which a blind hole is formed by irradiating a workpiece with a laser beam to remove a part of the workpiece is specified such that a first irradiation step in which an oxidizing gas is ejected to an irradiation point when the laser beam is irradiated, and following the first irradiation step, a second irradiation step in which an inert gas is ejected to the irradiation point when the laser beam is irradiated are repeatedly performed until the depth of the blind hole reaches a predetermined depth.

[0010] According to another aspect of the present invention, a machining program that causes a control device of a laser machining apparatus that forms a blind hole by irradiating a workpiece with a laser beam to remove a part of the workpiece to perform the following steps is specified to cause the control device to repeatedly perform a first irradiation step of ejecting an oxidizing gas to an irradiation point when the laser beam is irradiated, and a second irradiation step following the first irradiation step of ejecting an inert gas to the irradiation point when the laser beam is irradiated, until the depth of the blind hole reaches a predetermined depth.

[0011] According to another aspect of the present invention, a control device for controlling an operation of a laser machining apparatus that forms a blind hole by irradiating a workpiece with a laser beam to remove a part of the workpiece is specified to include a machining program for controlling the operation of the laser machining apparatus, the machining program causing the control device to repeatedly perform a first irradiation step of ejecting an oxidizing gas to an irradiation point upon irradiation of the laser beam and a second irradiation step following the first irradiation step of ejecting an inert gas to the irradiation point upon irradiation of the laser beam, until the depth of the blind hole reaches a predetermined depth. EFFECT OF THE INVENTION

[0012] According to one aspect of the present invention, a first irradiation step in which an oxidizing gas is ejected to an irradiation point when the laser beam is irradiated, and a second irradiation step in which an inert gas is ejected to the irradiation point when the laser beam is irradiated are repeatedly performed until the depth of a blind hole reaches a predetermined depth, thereby obtaining a sufficient machining depth and a bottom without any residual oxide film after machining. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing a structure of a laser processing apparatus having a control device for executing a laser processing method according to a first embodiment, which is a representative example of the present invention; Fig. 2 is a block diagram showing an example of a structure of a Fig. 1 shows the gas supply mechanism; Fig. 3 is a block diagram showing an example of the structure of the Fig. 1 shows the control device; Fig. 4A is a partial sectional view showing a processing state when a first irradiation step of the laser processing method according to the first embodiment is carried out; Fig. 4B is another partial sectional view showing the processing state when the first irradiation step of the laser processing method according to the first embodiment is carried out; Fig. 5A is a partial sectional view showing a processing state when a second irradiation step of the laser processing method according to the first embodiment is carried out; Fig. 5B is another partial sectional view showing the processing state when the second irradiation step of the laser processing method according to the first embodiment is carried out; Fig. 6 is a flowchart showing a control operation performed by a main control unit of the control device according to the first embodiment; Fig. 7A is a partial sectional view showing a continuous machining state when the laser machining method according to the first embodiment is performed; Fig. 7B is another partial sectional view showing the continuous machining state when the laser machining method according to the first embodiment is performed; Fig. 7C is another partial sectional view showing the continuous machining state when the laser machining method according to the first embodiment is performed; Fig. 7D is another partial sectional view showing the continuous machining state when the laser machining method according to the first embodiment is performed; Fig. 8A is a partial sectional view showing a continuous machining state when a laser machining method according to a second embodiment, which is another example of the present invention, is performed; Fig. 8B is another partial sectional view showing the continuous machining state when the laser machining method according to the second embodiment, which is another example of the present invention, is performed; Fig. 9A is a partial plan view showing an example of a machining path of a laser beam in the laser machining method according to the second embodiment; Fig. 9B is another partial plan view showing an example of the machining path of the laser beam in the laser machining method according to the second embodiment; Fig. 10A is a partial plan view showing an example of a machining path of a laser beam in a laser machining method according to a variation of the second embodiment; Fig. 10B is a partial plan view showing an example of the machining path of the laser beam in the laser machining method according to another variation of the second embodiment; Fig. 11A is a partial sectional view showing a continuous machining state when the laser machining method according to the variation of the second embodiment is performed; Fig. 11B is a partial sectional view showing the continuous machining state when the laser machining method according to another variation of the second embodiment is performed; Fig. 11C is a partial sectional view showing a continuous machining state when a laser machining method is performed according to still another variation of the second embodiment; Fig. 12 is a schematic diagram showing a structure of a laser processing apparatus having a control device for performing a laser processing method according to a third embodiment, which is still another example of the present invention; and Fig. 13 is a block diagram showing an example of the structure of a machining head and a gas supply mechanism used in Fig. 12 are shown. WAYS FOR CARRYING OUT THE INVENTION

[0013] With reference to the accompanying drawings, a description will now be given of embodiments of a laser machining method according to a representative example of the present invention, a machining program for executing the method, and a control device. First embodiment

[0014] Fig. 1 is a schematic diagram showing a structure of a laser processing apparatus having a control device for executing a laser processing method according to a first embodiment, which is a representative example of the present invention. Further, Fig. 2 a block diagram showing an example of the structure of a Fig. 1 shows the gas supply mechanism. In addition, Fig. 3 a block diagram showing an example of the structure of the Fig. 1 shown control device.

[0015] As in Fig. 1, the laser processing apparatus 100 includes, by way of example, a laser oscillator 110 that oscillates a laser beam LB for processing, a workpiece holding mechanism 120 that holds a workpiece W, a processing head 130 that irradiates the workpiece W with the laser beam LB, a head transfer mechanism 140 that moves the processing head 130 with respect to the workpiece W, a gas supply mechanism 150 that supplies an assist gas to the processing head 130, and a control device 160 that controls a laser processing operation on the workpiece W based on a processing program.

[0016] The laser oscillator 110 uses an oscillation source with a wavelength that has a high absorption rate depending on the material of the workpiece W to be processed. For example, the laser oscillator 110 can be an oscillator that enables fiber transmission, such as a YAG laser, a YVO4 laser, a fiber laser, and a disk laser. The oscillation of the laser beam LB output from the laser oscillator 110 can be either a continuous wave or a pulsed wave, and the laser beam LB is transmitted to the processing head 130 via a transmission path 134, such as an optical fiber.

[0017] The workpiece holding mechanism 120 includes, for example, a clamping mechanism (not shown) for attaching the workpiece W and is configured to grip and fix the workpiece W. The workpiece holding mechanism 120 may also include, for example, a mechanism for moving the workpiece W in three directions X, Y, and Z, as well as a rotation mechanism.

[0018] The machining head 130 is configured such that the laser beam LB is introduced into one end (the upper end) of the machining head 130, for example, via a transmission path 134 such as an optical fiber, and is irradiated from a nozzle 132 at the other end (the lower end) toward the workpiece. In this case, a condenser lens (not shown) disposed inside the machining head 130 focuses the laser beam LB at a focal point on the workpiece W to a predetermined beam diameter.

[0019] Furthermore, an auxiliary gas for assisting laser processing by the laser beam LB is supplied to the processing head 130 from a gas supply mechanism 150, which will be described later, via a gas supply pipe 152 at a predetermined pressure and flow rate. The auxiliary gas supplied to the processing head 130 is then ejected from the nozzle 132 coaxially with the laser beam LB.

[0020] The head transport mechanism 140 includes, for example, a linear drive 142 that moves in three mutually orthogonal directions X, Y, and Z, with the machining head 130 attached to one end of the linear drive 142. The head transport mechanism 140 can be configured as a six-axis or seven-axis industrial robot equipped with a robot arm, to one end of which the machining head 130 is attached.

[0021] The gas supply mechanism 150 has as a Fig. 2, an oxidizing gas supply source 154a that temporarily stores an oxidizing gas, an inert gas supply source 154b that temporarily stores an inert gas, supply channels 155a and 155b that guide the supplied oxidizing gas and the supplied inert gas, respectively, pressure sensors 156a and 156b provided on the supply channels 155a and 155b, and a switching unit 158 ​​that selectively switches the oxidizing gas and the inert gas supplied from the two supply channels 155a, 155b so that the selected gas is supplied to the gas supply pipe 152. The switching unit 158 ​​has a switching valve and is configured to receive supply commands from the control unit 160 and thereby supply the specific gas type to the gas supply pipe 152.

[0022] In this description, the "oxidizing gas" may be pure oxygen gas (O2 gas) or oxygen gas containing a small amount of nitrogen (N2). The "inert gas" may be nitrogen gas (N2 gas), helium gas (He gas), or argon gas (Ar gas). Furthermore, the pressure sensors 156a, 156b shown in Fig. 2 are flow sensors.

[0023] The control device 160 has as a Fig. 3, the control device 160 includes a main control unit 162 that issues drive commands to the components of the laser processing device 100 based on a processing program, a display unit 164 that displays various parameters, and an input interface 166 that enables manual input of information for modifying the processing program and various parameters. Furthermore, the main control unit 162 of the control device 160 is wired or wirelessly connected to the laser oscillator 110, the workpiece holding mechanism 120, the head transport mechanism 140, and the gas supply mechanism 150, and exchanges signals with these peripheral mechanisms to control the operation of the entire laser processing device 100.

[0024] The main control unit 162 has, for example, a function of extracting information regarding a machining path and machining conditions from the machining program and outputting an output command signal to the laser oscillator 110 to command the output of the laser beam LB. The main control unit 162 also has, for example, a function of extracting information regarding the position of an irradiation point FP of the laser beam LB and the position of the machining head 130 from the machining program and outputting a machining position command signal to the workpiece holding mechanism 120 and the head transfer mechanism 140 to command the relative movement between the workpiece W and the machining head 130.In addition, the main control unit 162 has, for example, a function of extracting information regarding the type of assist gas to be ejected while irradiating and moving the laser beam LB from the machining program and outputting a gas supply command to the gas supply mechanism 150.

[0025] With reference to Fig. 4A to 7D, a manner of carrying out the laser machining method according to the first embodiment will be described in detail.

[0026] Fig. 4A and Fig. 4B are partial sectional views showing a processing state when a first irradiation step of the laser processing method according to the first embodiment is performed. Fig. 5A and Fig. 5B are partial sectional views showing a processing state when a second irradiation step of the laser processing method according to the first embodiment is performed. Fig. 6 is a flowchart showing a control operation performed by the main control unit of the control device according to the first embodiment. Fig. 7A to 7D are partial sectional views showing a continuous machining state when the laser machining method according to the first embodiment is performed.

[0027] The laser machining method according to the first embodiment repeatedly performs the first irradiation step, in which an oxidizing gas Ga is ejected to the irradiation point FP when the laser beam LB is irradiated, and the second irradiation step, in which an inert gas Gb is ejected to the irradiation point FP when the laser beam LB is irradiated, until a blind hole BH reaches a predetermined depth. Consequently, a portion of the workpiece W is removed, thereby forming the blind hole BH with the predetermined depth.

[0028] In the first irradiation step, the processing is carried out as in Fig. 4A, the welding is carried out by ejecting an oxidizing gas Ga as an auxiliary gas at a high velocity and high pressure to the irradiation point FP of the laser beam LB. The emitted laser beam LB is absorbed into the workpiece W, thereby forming a weld pool MP with a depth Da.

[0029] Since the oxidizing gas Ga is emitted as an auxiliary gas while the laser beam LB is emitted, the oxygen contained in the oxidizing gas Ga causes the temperature of the molten strip to rise, thereby increasing the penetration depth Da. The oxidizing gas, which is emitted at high speed, blows the molten weld pool MP away from the workpiece W, so that the blind hole BH with the depth Da is formed in the workpiece W as shown in Fig. 4B. In this case, due to an oxidation reaction between the workpiece W and the oxidizing gas Ga, an oxide film MO with a predetermined thickness remains on the bottom surface of the blind hole BH.

[0030] In the second irradiation step, the processing is carried out as in Fig. 5A, the welding process is carried out by ejecting an inert gas Gb as an auxiliary gas at a high velocity and high pressure to the irradiation point FP of the laser beam LB. The emitted laser beam LB is absorbed into the workpiece W, thereby forming a weld pool MP with a depth Db.

[0031] Since the inert gas Gb is ejected as an auxiliary gas while the laser beam LB is radiated, the environment of the weld pool MP becomes an inert gas atmosphere due to the effect of the inert gas GB, so that no oxidation reaction occurs with the molten workpiece W. The inert gas, which is ejected at high speed, blows the weld pool MP away from the workpiece W, which is why the blind hole BH with the depth Db is formed in the workpiece W, as shown in Fig. 5B. As a result, the blind hole BH, whose depth is small but whose bottom surface has almost no oxide film MO remaining, can be obtained.

[0032] In the laser processing method according to the first embodiment, which employs the above-described procedures of the first irradiation step and the second irradiation step, the main control unit 162 of the control device 160 reads as shown in Fig. As shown in Figure 6, the machining program, including the size and depth of a blind hole to be machined, the laser beam irradiation conditions, and so on, is first retrieved from, for example, an external database or storage medium (not shown) (step S101). Then, the main control unit 162 analyzes the retrieved machining program and generates various command signals, which are output to the components of the laser machining apparatus 100.

[0033] Second, the main control unit 162 outputs a supply command signal to the gas supply mechanism 150 based on the gas supply conditions determined in the machining program to switch to the discharge of the oxidizing gas Ga (step S102). The main control unit 162 then outputs irradiation command signals to the laser oscillator 110, the workpiece holding mechanism 120, and the head conveying mechanism 140 based on the emission conditions of the laser beam LB (step S103). Through the operations of the above two steps, the above-described "first irradiation step" is executed, thereby forming the blind hole BH with the depth Da in the workpiece W as shown in Fig. 7A is shown.

[0034] Subsequently, the main control unit 162 outputs a supply command signal to the gas supply mechanism based on the gas supply conditions determined in the machining program to switch to the discharge of the inert gas Gb (step S104). Then, the main control unit 162 outputs irradiation command signals to the laser oscillator 110, the workpiece holding mechanism 120, and the head conveying mechanism 140 based on the emission conditions of the laser beam LB (step S105). Through the operations of the above two steps, the above-described "second irradiation step" is executed, thereby forming the blind hole BH with the depth (Da + Db) in the workpiece W as shown in Fig. 7B is shown.

[0035] Next, the main control unit 162 obtains the hole depth (the cumulative total depth) of the blind hole BH formed so far in the machining (step S106). In the machining performed so far, the cumulative total depth is (Da + Db) as described above.

[0036] Then, the main control unit 162 determines whether the hole depth of the blind hole BH obtained in step S106 has reached the final hole depth specified by the machining program (step S107). If it is determined in step S107 that the obtained hole depth of the blind hole BH has reached the specified hole depth, the main control unit judges that the machining of the specified blind hole BH is completed and therefore terminates the control operation according to the machining program.

[0037] If it is determined at step S107 that the obtained hole depth of the blind hole BHJ has not reached the specified hole depth, the main control unit 162 returns to step S102 and executes the operations at step S102 and subsequent steps. That is, the main control unit 162 outputs the supply command signal to switch the assist gas to the oxidizing gas Ga (step S102), and then outputs the irradiation command signals to the laser oscillator 110, the workpiece holding mechanism 120, and the head transfer mechanism 140 (step S103).

[0038] Through these operations, the first irradiation step is repeated for a second time and thereby the blind hole BH with a depth (2Da + Db) is formed in the workpiece W, as shown in Fig. 7C. In this case, due to the oxidation reaction between the workpiece W and the oxidizing gas, an oxide film MO with a certain thickness remains on the bottom surface of the blind hole BH.

[0039] Then, the main control unit 162 outputs the supply command signal to switch the assist gas to the inert gas Gb (step S104), and then outputs the irradiation command signals to the laser oscillator 110, the workpiece holding mechanism 120, and the head transfer mechanism 140 (step S105). The second irradiation step is repeated a second time, thereby forming the blind hole BH with a depth of (2Da + 2Db) in the workpiece W, leaving almost no oxide film MO.

[0040] Subsequently, the main control unit 162 acquires the hole depth (the cumulative total depth) of the blind hole BH formed so far in the machining (step S106), and determines whether the acquired hole depth of the blind hole BH has reached the final depth specified in the machining program (step S107). If it is determined in the thus repeatedly executed step S107 that the acquired hole depth of the blind hole BH has reached the specified hole depth, the main control unit 162 judges, as in the first case, that the machining of the specified blind hole BH is completed and therefore terminates the control operation according to the machining program.

[0041] If it is determined at step S107 that the obtained hole depth of the blind hole BH has not reached the predetermined hole depth, the main control unit 162 returns to step S102 and executes the operations at step S102 and subsequent steps. Thus, the laser machining method according to the first embodiment performs the first irradiation step using the oxidizing gas Ga as the auxiliary gas and the second irradiation step using the inert gas GB as the auxiliary gas to form the blind hole BH with the predetermined depth in the workpiece W.

[0042] At this time, if the hole depth BH of the blind hole specified in the machining program is not an integer multiple of the sum of the machining depth Da in the first irradiation step and the machining depth Db in the second irradiation step, the laser machining conditions in the first irradiation step and the second irradiation step, which are repeatedly performed, can be set as appropriate. However, the laser machining conditions should be set so that the last process repeatedly performed in the machining is a process according to the second irradiation step. As a result, the blind hole BH with almost no oxide film MO remaining on its surface is formed in the workpiece W.

[0043] With the configuration described above, the laser machining method according to the first embodiment performs the first irradiation step of ejecting the oxidizing gas to the irradiation point upon irradiation of the laser beam and the second irradiation step of ejecting the inert gas to the irradiation point upon irradiation of the laser beam until the depth of the blind hole reaches the predetermined depth, thereby obtaining a sufficient machining depth and a bottom where no oxide film remains after machining. In this first embodiment, a specific implementation of the representative laser machining method according to the present invention has been described.Alternatively, a machining program for performing the steps of the laser machining method may be employed by a control device, and a laser machining apparatus including this machining program may be configured to perform the operations of the laser machining program described above while functioning as a control device. Second embodiment

[0044] Fig. 8A and Fig. 8B are partial sectional views showing a continuous machining state when a laser machining method according to a second embodiment, which is another example of the present invention, is carried out. Fig. 9A and Fig. 9B are partial plan views showing examples of a processing path of a laser beam in a laser processing method according to the second embodiment. Fig. 10A and Fig. 10B are partial plan views showing examples of a processing path of a laser beam in a laser processing method according to a variation of the second embodiment. Fig. 11A to 11C are partial sectional views showing a continuous machining state when the laser machining method according to the variation of the second embodiment is carried out.

[0045] In the second embodiment, structural elements similar to those in the first embodiment are shown in the schematic diagrams, etc. shown in Fig. 1 to 7D are the same or may employ common structures, are designated by the same reference numerals and their description will not be repeated.

[0046] The laser processing method according to the second embodiment carries out the first irradiation step, which is Fig. 4A and Fig. 4B, and after the first irradiation step, the second irradiation step shown in Fig. 5A and Fig. 5B, the laser beam LB irradiated onto a workpiece W is repeatedly scanned by scanning an optical axis until the depth of a blind hole BH reaches a predetermined depth. Therefore, a portion of the workpiece W corresponding to the irradiation area of ​​the laser beam LB is removed, thereby forming the blind hole BH with a predetermined depth.

[0047] In the first irradiation step, the processing is carried out as in Fig. 8A, by scanning the laser beam LB in a predetermined direction TD while ejecting an oxidizing gas Ga as an auxiliary gas at a high speed and high pressure to an irradiation point FP of the laser beam LB. As a result, a weld pool MP with a depth Da is formed in the workpiece W at the irradiation point FP of the laser beam LB, and the weld pool MP is moved by scanning the laser beam LB.

[0048] Since the laser beam LB is irradiated while the oxidizing gas Ga is discharged as an auxiliary gas, the oxidizing gas Ga, which is discharged at a high speed, blows the weld pool MP away from the workpiece W, and consequently, the blind hole BH with the depth Da is formed in a predetermined region in the workpiece W. At this time, due to an oxidation reaction between the workpiece W and the oxidizing gas Ga, an oxide film MO with a predetermined thickness remains on the bottom surface of the blind hole BH.

[0049] In the second irradiation step, the processing is carried out as in Fig. 8B, by scanning the laser beam LB in the predetermined direction TD while ejecting an inert gas Gb as an auxiliary gas at a high speed and high pressure to an irradiation point FP of the laser beam LB, the welding is performed in an overlapping manner in the area machined in the first irradiation step. As a result, a weld pool MP with a depth Db is formed in the workpiece W at the irradiation point FP of the laser beam LB, and the weld pool MP is moved by scanning the laser beam LB.

[0050] Since the laser beam LB is irradiated while the inert gas Gb is discharged as an assist gas, the inert gas Gb discharged at a high speed blows the weld pool MP away from the workpiece W, and thus the blind hole BH with the depth Db is formed in a predetermined region in the workpiece W. Consequently, the blind hole BH with almost no oxide film MO remaining on the bottom surface can be obtained. As in the first embodiment, the laser machining method according to the second embodiment repeats the first irradiation step and the second irradiation step until the hole depth specified in the machining program is reached.

[0051] The process of scanning the laser beam in the above-mentioned predetermined area may be a mode in which the optical axis of the laser beam LB is moved approximately in a zigzag manner to the right and left in a rectangular area, as shown in Fig. 9A, or an embodiment in which the optical axis of the laser beam LB is shifted from left to right in the same rectangular area by one row each time, as shown in Fig. 9B. The scanning of the laser beam LB can be set to follow a straight path as well as a curved path.

[0052] For example, the laser beam LB can be as in Fig. 10A, the laser beam LB can be scanned along a circumferential path that is a concentric circle, forming a round blind hole BH. Furthermore, the laser beam LB can be Fig. 10B shown scanned on a spiral path from the center of a circle.

[0053] As a concrete application example for the formation of the above-described round blind hole BH, in the workpiece W, for example, as in Fig. As shown in Figure 11A, a through hole TH with a predetermined inner diameter is formed, and then the first irradiation step is performed to scan the laser beam LB in a circular area centered on the through hole TH. This forms the blind hole BH with a depth Da connected to the through hole TH.

[0054] Then, as in Fig. As shown in Figure 11C, the second irradiation step is performed to scan the laser beam LB in the same irradiation area (on the same path) as in the first irradiation step. This removes the oxide film MO remaining in the blind hole BH formed in the first irradiation step, and forms the blind hole with the depth (Da + Db) connected to the through hole TH. As in the first embodiment, the first irradiation step and the second irradiation step described above are repeated until the hole depth specified in the machining program is reached.

[0055] According to such an application example, the blind hole BH formed by the laser machining method of the second embodiment can be applied as a counterbore used for tightening the head of a bolt or a nut on the workpiece W. At this time, since the bottom surface of the blind hole BH is formed as a surface where almost no oxide film MO remains by the second irradiation step, no design surface blackened by the oxide film MO is exposed, and no finishing is required after machining.

[0056] With the above-described configuration, in the laser machining method according to the second embodiment, in addition to the effect described with respect to the first embodiment, processing is performed by scanning the optical axis of the laser beam in the predetermined range, thereby enabling the formation of a blind hole with any bottom shape. Specifically, a screw hole or a through hole is formed in the workpiece, and a blind hole connected to this hole is formed, so that the formed blind hole can be applied as a counterbore in which the bottom surface of the blind hole is the mounting surface. Third embodiment

[0057] Fig. 12 is a schematic diagram showing a laser processing apparatus having a control device for performing a laser processing method according to a third embodiment, which is still another example of the present invention. Fig. 13 is a block diagram showing an example of the structure of a machining head and a gas supply mechanism used in Fig. 12. In the third embodiment, structural elements similar to those in the first and second embodiments are shown in the schematic diagrams, etc. shown in Fig. 1 to 11C are the same or may employ common structures, are designated by the same reference numerals and their description will not be repeated.

[0058] In the third embodiment, a structure is used in which the processing head 130 shown in the first embodiment, which radiates (ejects) the laser beam LB and the auxiliary gas (the oxidizing gas Ga, the inert gas Gb) coaxially from the nozzle, is replaced by a scanning head 330 for scanning the optical axis of the laser beam LB using an optical system such as a mirror and a gas ejection nozzle 354 for ejecting the auxiliary gas to an irradiation point FP of the laser beam LB. More specifically, a laser processing apparatus 330 as shown in Fig. 12, for example, a laser oscillator 110, a workpiece holding mechanism 120, the scanning head 330 that scans the optical axis of the laser beam LB in a predetermined area of ​​the workpiece W, a head transport mechanism 140 that moves the scanning head 330 with respect to the workpiece holding mechanism 120, a gas supply mechanism 350 that supplies the assist gas to the irradiation point FP of the laser beam LB irradiated onto the workpiece W, and a control device 160 that controls a laser machining operation on the workpiece W based on a machining program.

[0059] The scan head 330 has a Fig. 13, a housing 332, a connector 334a connecting a transmission path 334 to the housing 332, a pair of scanning mirrors 336a, 336b that reflect a processing laser beam LB introduced from the connector 334a and determine a scanning angle for scanning an optical axis of the laser beam LB, and a light-converging optical system 338 arranged on the emission side of the scanning mirrors 336a, 336b to irradiate the workpiece W with the laser beam LB. With this structure, the laser beam LB emitted from the scanning head 330 can move an irradiation point FP of the laser beam LB to any position within a predetermined scanning range, as shown in Fig. 13. The scan head 330 may also include known structures such as a cooling mechanism for cooling various built-in optical systems.

[0060] The pair of scanning mirrors 336a, 336b, for example, have mirror planes for total internal reflection of the laser beam LB and have a function for moving (scanning) the optical axis of the laser beam LB by pivoting the scanning mirrors at a minute angle. The scanning mirrors 336a, 336b include, for example, a galvano scanner that pivots a total internal reflection mirror around a predetermined galvanomotor axis to tilt it to any desired angle, or a piezoelectric scanner in which the total internal reflection mirror is attached to an actuator using a piezoelectric film, and the angle of the total internal reflection mirror is finely adjusted by applying a current.

[0061] The light-converging optical system 338 is configured to converge the laser beam LB deflected by the pair of scanning mirrors 336a, 336a so that the beam is focused on a predetermined position on the workpiece W. It is constructed, for example, as a combination of a condenser lens, an fθ lens, and the like. Therefore, the laser beam LB scanned within a predetermined scanning range is incident almost perpendicularly on the surface of the workpiece W. The light-converging optical system 338 also functions as a lid that tightly seals the interior of the scanning head 330.

[0062] The gas supply mechanism 350 comprises, for example, a supply source 154a for an oxidizing gas, a supply source 154b for an inert gas, supply channels 155a and 155b, pressure sensors 156a and 156b and a switching unit 158, which are arranged in Fig. 2 are shown, but all in Fig.13 are not shown, and further comprises a gas supply pipe 352 which carries a gas supplied from the switching unit 158, a gas ejection nozzle 354 which is attached to one end of the gas supply pipe 352, and a nozzle moving mechanism 356 which moves the gas ejection nozzle 354 to assume an arbitrary position and in an arbitrary direction.

[0063] The nozzle moving mechanism 356 is composed of, for example, a robot arm with the gas ejection nozzle 354 attached to one end thereof, and is configured to move the gas ejection nozzle 354 based on an irradiation command signal received from a main control unit 162 of a control device 160 so that the ejection opening of the gas ejection nozzle 354 is directed toward an irradiation point FP of the laser beam LB. This ejects an auxiliary gas (an oxidizing gas, an inert gas) at the required timing toward the irradiation point FP of the scanned laser beam LB.

[0064] Since the laser processing apparatus 300 implementing a laser processing method according to the third embodiment uses the scanning head 330 to scan the laser beam LB, it is not necessary to move the scanning head 330 significantly, thereby enabling a reduction in size or simplification of the structure of the head transport mechanism 140. Furthermore, since the laser processing apparatus 300 jointly uses the scanning head 330 and the gas supply mechanism 350 that discharges the assist gas to the irradiation point FP of the laser beam LB, the laser beam LB can be configured, for example, as a so-called long-focus laser, thereby enabling remote processing that scans the laser beam LB at a high speed.

[0065] By the above-described structure, in the laser oscillator according to the third embodiment, in addition to the effect described with respect to the first embodiment, the scanning head and the head transport mechanism can be downsized or simplified by using the scanning head that enables high-speed scanning on the optical axis of the laser beam.

[0066] The present invention is not limited to the above-described embodiments, but can be modified as appropriate without departing from the gist of the invention. For example, any structural elements in the embodiments of the present invention can be modified, or any structural elements can be omitted from the embodiments.

[0067] For example, in the first to third embodiments, specific implementations of the laser machining method were described, but the present invention can be interpreted to include within the scope of the invention a machining program for causing the control device to execute the laser machining method, and a control device containing the machining program or a storage medium for storing the machining program. LIST OF REFERENCE SYMBOLS 100 laser processing device 110 Laser oscillator 120 Workpiece holding mechanism 130 machining head 132 nozzle 134 Transmission path 140 Head transport mechanism 142 Linear actuator 150 Gas supply mechanism 152 Gas supply pipe 154a Supply source for an oxidizing gas 154b Supply source for an inert gas 155a, 155b supply channel 156a, 156b pressure sensor 158 switching unit 160 control device 162 Main control unit 164 display unit 166 Input interface 300 laser processing device 330 scan head 332 housings 334 Transmission path 334a connector 336a, 336b Scanning mirror 338 light-concentrating optical system 350 Gas supply mechanism 352 Gas supply pipe 354 Gas ejection nozzle 356 Nozzle movement mechanism QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 11-104879

[0004] JP 2001-214986

[0004]

Claims

[1] A laser machining method for forming a blind hole by irradiating a workpiece with a laser beam to remove a part of the workpiece, comprising the following steps, a first irradiation step in which an oxidizing gas is ejected to an irradiation point during the emission of the laser beam; and following the first irradiation step, a second irradiation step in which an inert gas is ejected to the irradiation point during the emission of the laser beam, be carried out repeatedly until a depth of the blind hole reaches a predetermined depth. [2] The laser processing method according to claim 1, wherein the first irradiation step is performed while moving the irradiation point, and the second irradiation step is performed while moving the irradiation point along the same path as the first irradiation point. [3] The laser machining method according to claim 2, wherein the irradiation point is moved by moving a machining head that irradiates the laser beam in the first irradiation step and the second irradiation step. [4] The laser machining method according to claim 2, wherein the irradiation point is moved in the first irradiation step and the second irradiation step by means of a scanning head that scans an optical axis of the laser beam. [5] The laser machining method according to claim 3 or 4, wherein the irradiation point is moved on a circumferential or spiral path in the first irradiation step and the second irradiation step. [6] Machining program that causes a control device of a laser machining device that forms a blind hole by irradiating a workpiece with a laser beam to remove a part of the workpiece to perform the following steps, a first irradiation step in which an oxidizing gas is ejected to an irradiation point when the laser beam is irradiated; and following the first irradiation step, a second irradiation step in which an inert gas is ejected to the irradiation point during the emission of the laser beam, repeatedly until a depth of the blind hole reaches a predetermined depth. [7] A machining program according to claim 6, wherein the first irradiation step is performed while the irradiation point is moved, and the second irradiation step is carried out while the irradiation point is moved along the same path as the first irradiation point. [8] The machining program according to claim 7, wherein the irradiation point is moved by moving a machining head that irradiates the laser beam in the first irradiation step and the second irradiation step. [9] The machining program according to claim 7, wherein the irradiation point is moved in the first irradiation step and the second irradiation step by means of a scanning head that scans an optical axis of the laser beam. [10] The machining program according to claim 8 or 9, wherein the irradiation point is moved on a circumferential or spiral path in the first irradiation step and the second irradiation step. [11] A control device for controlling an operation of a laser machining device that forms a blind hole by irradiating a workpiece with a laser beam to remove a part of the workpiece, wherein the control device contains a processing program that controls the operation of the laser processing device, where the processing program performs the following steps, a first irradiation step in which an oxidizing gas is ejected to an irradiation point when the laser beam is irradiated; and following the first irradiation step, a second irradiation step in which an inert gas is ejected to the irradiation point during the emission of the laser beam, repeatedly until a depth of the blind hole reaches a predetermined depth. [12] The control device according to claim 11, wherein the first irradiation step is performed while moving the irradiation point, and the second irradiation step is performed while moving the irradiation point along the same path as the first irradiation point. [13] The control device according to claim 12, wherein the irradiation point is moved in the first irradiation step and the second irradiation step by moving a machining head that irradiates the laser beam. [14] The control device according to claim 12, wherein the irradiation point is moved in the first irradiation step and the second irradiation step by means of a scanning head that scans an optical axis of the laser beam. [15] The control device according to claim 13 or 14, wherein the irradiation point is moved on a circumferential or spiral path in the first irradiation step and the second irradiation step.

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