Laser processing machine and method for controlling the laser processing machine

Abstract

A laser processing machine is provided that can process a workpiece by displacing a laser beam while accurately accommodating it within a nozzle opening. [Solution] A low-pass filter 522 filters a movement command signal CS to generate a main movement command signal MCS that causes the movement mechanism to move the machining head. A delay device 523 delays the movement command signal CS to generate a delayed movement command signal DCS. A subtractor 524 subtracts the main movement command signal MCS from the delayed movement command signal DCS to generate a secondary movement command signal SCS that causes the beam displacement mechanism to displace the laser beam. By setting the order of the low-pass filter 522 and the delay time of the delay device 523, the cutoff frequency of the low-pass filter 522 is set, which determines the amount of laser beam displacement that causes the laser beam displaced by the beam displacement mechanism to fit within the nozzle opening.

Description

[Technical Field]

[0001] The present invention relates to a laser processing machine and a method for controlling the laser processing machine. [Background technology]

[0002] Patent Document 1 describes a laser processing machine including a movement mechanism for moving a processing head and a beam displacement mechanism for displacing a laser beam traveling through an opening of a nozzle attached to the tip of the processing head. The laser processing machine includes a delay device for delaying a movement command signal for moving the processing head using the movement mechanism to cut the workpiece, a low-pass filter for filtering the movement command signal, and a subtractor for calculating the difference between the delayed movement command signal output from the delay device and the movement command signal filtered by the low-pass filter. The laser processing machine controls the movement of the processing head using the movement mechanism based on the filtered main movement command signal, and controls the displacement of the laser beam using the beam displacement mechanism based on a secondary movement command signal, which is a difference signal output from the subtractor.

[0003] The laser processing machine described in Patent Document 1, with the above configuration, moves the processing head at a gentler angle than the actual angle when changing the cutting direction of the workpiece (the direction in which the processing head moves) by a relatively large angle. The beam displacement mechanism displaces the laser beam to compensate for the difference between the actual angle and the gentle angle. Therefore, the position of the laser beam irradiated on the workpiece is equivalent to the actual angle of the processing head, allowing the workpiece to be cut according to the processing path instructed by the processing program. According to the laser processing machine described in Patent Document 1, there is no need to temporarily stop the processing head or significantly slow down the processing head's movement speed when changing the cutting direction of the workpiece, thereby shortening processing time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-25979 Summary of the Invention [Problem to be solved by the invention]

[0005] In a laser processing machine configured as described above, the beam displacement mechanism needs to displace the laser beam so that it fits within the nozzle opening. There is a need for a laser processing machine and a control method for a laser processing machine that can process a workpiece by moving the processing head based on a main movement command signal obtained by filtering a movement command signal, and displacing the laser beam while keeping it accurately within the nozzle opening based on a sub-movement command signal that is a difference signal between the delayed movement command signal and the main movement command signal. [Means for solving the problem]

[0006] A first aspect of one or more embodiments includes a machining head having a circular opening at a tip end and attached with a nozzle that emits a laser beam for machining a workpiece from the opening; a movement mechanism that moves the machining head relative to the workpiece along a surface of the workpiece; a beam displacement mechanism that displaces the laser beam traveling within the opening from the center of the opening; and a control device that controls the movement of the machining head by the movement mechanism and the displacement of the laser beam by the beam displacement mechanism, wherein the control device filters and outputs a movement command signal that moves the machining head from a machining start position to a machining end position in order to machine the workpiece. a delay device that delays the movement command signal to generate a delayed movement command signal; and a subtractor that subtracts the main movement command signal from the delayed movement command signal to generate a secondary movement command signal that causes the beam displacement mechanism to displace the laser beam. By setting the order of the low pass filter and the delay time of the delay device, the cutoff frequency of the low pass filter can be set to obtain the amount of displacement of the laser beam so that the laser beam displaced by the beam displacement mechanism fits within the aperture.

[0007] A second aspect of one or more embodiments provides a method for controlling a laser processing machine, the method comprising: filtering, using a low-pass filter, a movement command signal for moving a processing head from a processing start position to a processing end position in order to process a workpiece, to generate a main movement command signal; delaying the movement command signal using a delay device to generate a delayed movement command signal; subtracting the main movement command signal from the delayed movement command signal using a subtractor to generate a secondary movement command signal; moving the processing head along a surface of the workpiece relative to the workpiece using a movement mechanism based on the main movement command signal; displacing a laser beam emitted from a circular opening at the tip of a nozzle attached to the processing head using a beam displacement mechanism based on the secondary movement command signal; and setting the order of the low-pass filter and the delay time set by the delay device to set a cutoff frequency of the low-pass filter at which an amount of displacement of the laser beam is obtained, so that the laser beam displaced by the beam displacement mechanism fits within the opening. [Effects of the Invention]

[0008] According to one or more embodiments of the laser processing machine and the control method for the laser processing machine, the processing head is moved based on a main movement command signal obtained by filtering a movement command signal, and the workpiece can be processed by displacing the laser beam while keeping it accurately within the nozzle opening based on a secondary movement command signal which is the difference signal between the delayed movement command signal and the main movement command signal. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the overall configuration of a laser processing machine according to one or more embodiments. [Figure 2] FIG. 2 is a perspective view showing a detailed configuration example of a collimator unit and a processing head provided in the laser processing machine according to one or more embodiments. [Figure 3] FIG. 3 is a diagram for explaining the displacement of the irradiation position of the laser beam on the workpiece by the beam displacement mechanism. [Figure 4]FIG. 4 is a block diagram showing an example of the functional configuration of an NC device provided in a laser processing machine according to one or more embodiments. [Figure 5] FIG. 5 is a block diagram showing a detailed configuration example of the filter control section 52 in FIG. [Figure 6] FIG. 6 is a diagram showing an example of a movement locus of the machining head in response to a movement command signal and a movement locus of the machining head in response to a main movement command signal. [Figure 7] FIG. 7 is a diagram showing the machining axis speed according to an example of a movement command signal and a movement command by a main movement command signal, with the delay time of the movement command signal set to 0. [Figure 8] FIG. 8 is a diagram showing the beam displacement amount when the delay time of the movement command signal is set to 0 and the movement commands by the movement command signal and the main movement command signal are as shown in FIG. [Figure 9] FIG. 9 is a diagram showing machining axis speeds according to an example of movement commands based on a movement command signal, a delayed movement command signal, and a main movement command signal. [Figure 10] FIG. 10 is a diagram showing the beam displacement amount when the movement commands by the movement command signal, delayed movement command signal, and main movement command signal are as shown in FIG. [Figure 11] FIG. 11 is a diagram showing the machining axis speeds based on movement commands from the movement command signal, delayed movement command signal, and main movement command signal when the order of the low-pass filter in FIG. 5 is 6, the cutoff frequency is 25 Hz, and the delay time of the delay device is the group delay time of the low-pass filter. [Figure 12A] FIG. 12A is a diagram showing the beam displacement amount when the movement commands by the movement command signal, delayed movement command signal, and main movement command signal are as shown in FIG. [Figure 12B] FIG. 12B is a diagram showing the beam displacement amount when the movement command is a movement command signal, a delayed movement command signal, and a main movement command signal, with the order of the low-pass filter in FIG. 5 set to 6, the cutoff frequency set to 24.784 Hz, and the delay time of the delay device set to 30 ms. [Figure 13]FIG. 13 is a diagram showing the machining axis speeds according to the movement command signals, delayed movement command signals, and main movement command signals when the delay time of the delay device is set to 10 ms and the cutoff frequency of the low-pass filter is set to 74.352 Hz. [Figure 14] FIG. 14 is a diagram showing the beam displacement amount when the movement commands by the movement command signal, delayed movement command signal, and main movement command signal are as shown in FIG. [Figure 15] FIG. 15 is a diagram showing the amount of beam displacement when the processing head is moved in the X-axis direction and the Y-axis direction to cut the workpiece under the same conditions as in FIG. [Figure 16] FIG. 16 is a diagram showing the machining axis speeds according to the movement commands from the movement command signal, delayed movement command signal, and main movement command signal when the delay time of the delay device is set to 70 ms and the cutoff frequency of the low-pass filter is set to 10.622 Hz. [Figure 17] FIG. 17 is a diagram showing the beam displacement amount when the movement commands by the movement command signal, the delayed movement command signal, and the main movement command signal are as shown in FIG. [Figure 18] FIG. 18 is a diagram showing the amount of beam displacement when the processing head is moved in the X-axis direction and the Y-axis direction to cut the workpiece under the same conditions as in FIG. [Figure 19] FIG. 19 is a diagram showing the machining axis speeds according to the movement command signals, delayed movement command signals, and main movement command signals when the delay time of the delay device is set to 65 ms and the cutoff frequency of the low-pass filter is set to 11.439 Hz. [Figure 20] FIG. 20 is a diagram showing the beam displacement amount when the movement commands by the movement command signal, delayed movement command signal, and main movement command signal are as shown in FIG. [Figure 21] FIG. 21 is a diagram showing the amount of beam displacement when the processing head is moved in the X-axis direction and the Y-axis direction to cut the workpiece under the same conditions as in FIG. [Figure 22] FIG. 22 is a flowchart showing the procedure for determining the beam displacement amount. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser processing machine and a method for controlling a laser processing machine according to one or more embodiments will be described below with reference to the accompanying drawings.

[0011] 1, a laser processing machine 100 according to one or more embodiments includes a laser oscillator 10 that generates and emits a laser beam, a laser processing unit 20, a process fiber 12 that transmits the laser beam emitted from the laser oscillator 10 to the laser processing unit 20, an operation unit 40, an NC device 50, an assist gas supply device 80, and a display unit 90. A processing program database 60 and a processing condition database 70 are connected to the NC device 50, for example, via a network. The NC device 50 is an example of a control device that controls each part of the laser processing machine 100. The NC device 50 can be configured using a computer device.

[0012] The processing program database 60 and the processing condition database 70 are external components of the laser processing machine 100, but the laser processing machine 100 may be provided with the processing program database 60 and the processing condition database 70.

[0013] A laser oscillator that amplifies pumping light emitted from a laser diode to emit a laser beam of a predetermined wavelength, or a laser oscillator that directly utilizes a laser beam emitted from a laser diode, is suitable as the laser oscillator 10. Examples of the laser oscillator 10 include a solid-state laser oscillator, a fiber laser oscillator, a disk laser oscillator, and a direct diode laser oscillator (DDL oscillator).

[0014] The laser oscillator 10 emits a laser beam in the 1 μm band with a wavelength of 900 nm to 1100 nm. Taking a fiber laser oscillator and a DDL oscillator as examples, the fiber laser oscillator emits a laser beam with a wavelength of 1060 nm to 1080 nm, and the DDL oscillator emits a laser beam with a wavelength of 910 nm to 950 nm.

[0015] The laser processing unit 20 has a processing table 21 on which the sheet metal W, which is the workpiece to be processed, is placed, a gate-shaped X-axis carriage 22, a Y-axis carriage 23, a collimator unit 30 fixed to the Y-axis carriage 23, and a processing head 35. The X-axis carriage 22 is configured to be movable in the X-axis direction on the processing table 21. The Y-axis carriage 23 is configured to be movable in the Y-axis direction perpendicular to the X-axis on the X-axis carriage 22. The X-axis carriage 22 and the Y-axis carriage 23 function as a movement mechanism that moves the processing head 35 along the surface of the sheet metal W in the X-axis direction, the Y-axis direction, or any combined direction of the X and Y axes. The X-axis and Y-axis may be referred to as processing axes.

[0016] Instead of moving the processing head 35 along the surface of the metal sheet W, the processing head 35 may be configured to be fixed in position and the metal sheet W may move. The laser processing machine 100 may be provided with a movement mechanism that moves the processing head 35 relative to the surface of the metal sheet W.

[0017] The processing head 35 is fitted with a nozzle 36 having a circular opening 36a at its tip, which emits a laser beam from the opening 36a. The laser beam emitted from the opening 36a of the nozzle 36 is irradiated onto the metal sheet W. An assist gas supply device 80 supplies nitrogen, oxygen, a mixed gas of nitrogen and oxygen, or air as an assist gas to the processing head 35. When the metal sheet W is processed, the assist gas is sprayed onto the metal sheet W from the opening 36a. The assist gas expels molten metal within the kerf width where the metal sheet W has melted.

[0018] 2, the collimator unit 30 includes a collimator lens 31 that converts the diverging laser beam emitted from the process fiber 12 into parallel light (collimated light). The collimator unit 30 also includes a galvanometer scanner unit 32 and a bend mirror 33 that reflects the laser beam emitted from the galvanometer scanner unit 32 downward in the Z-axis direction, which is perpendicular to the X-axis and Y-axis. The processing head 35 includes a focusing lens 34 that focuses the laser beam reflected by the bend mirror 33 and irradiates the metal sheet W with the focused laser beam.

[0019] In order to adjust the focal position of the laser beam, the focusing lens 34 is configured to be movable in a direction toward the metal sheet W and a direction away from the metal sheet W by a drive unit and a movement mechanism (not shown).

[0020] The laser processing machine 100 is centered so that the laser beam emitted from the opening 36a of the nozzle 36 is positioned at the center of the opening 36a. In the standard state, the laser beam is emitted from the center of the opening 36a. The galvano scanner unit 32 functions as a beam displacement mechanism that displaces the position within the opening 36a of the laser beam that travels through the processing head 35 and is emitted from the opening 36a. How the galvano scanner unit 32 displaces the laser beam will be described later.

[0021] Galvano scanner unit 32 has scan mirror 321 that reflects the laser beam emitted from collimator lens 31, and drive unit 322 that rotates scan mirror 321 to a predetermined angle. Galvano scanner unit 32 also has scan mirror 323 that reflects the laser beam emitted from scan mirror 321, and drive unit 324 that rotates scan mirror 323 to a predetermined angle.

[0022] The driving units 322 and 324 can change the angles of the scan mirrors 321 and 323, respectively, within a predetermined angle range under the control of the NC device 50. By changing the angle of one or both of the scan mirrors 321 and 323, the galvano scanner unit 32 can displace the laser beam traveling within the opening 36a of the nozzle 36, thereby shifting the position on the metal sheet W where the laser beam is irradiated. The galvano scanner unit 32 is an example of a beam displacement mechanism, and the beam displacement mechanism is not limited to the galvano scanner unit 32 having a pair of scan mirrors.

[0023] 3 shows a state in which either one or both of the scan mirror 321 and the scan mirror 323 are tilted, displacing the laser beam irradiated onto the metal sheet W. In FIG. 3, the thin solid line that is bent by the bend mirror 33 and passes through the focusing lens 34 indicates the optical axis of the laser beam when the laser processing machine 100 is in the reference state.

[0024] More specifically, the angle of the optical axis of the laser beam incident on the bend mirror 33 changes due to the operation of the galvano scanner unit 32 located in front of the bend mirror 33, and the optical axis deviates from the center of the bend mirror 33. For the sake of simplicity, in Fig. 3, the incident position of the laser beam on the bend mirror 33 is shown as the same before and after the operation of the galvano scanner unit 32.

[0025] It is assumed that the optical axis of the laser beam is displaced from the position indicated by the thin solid line to the position indicated by the thick solid line due to the action of the galvano scanner unit 32. If the laser beam reflected by the bend mirror 33 is tilted at an angle θ, the irradiation position of the laser beam on the metal sheet W is displaced by a distance Δs. If the focal length of the focusing lens 34 is EFL (Effective Focal Length), the distance Δs is calculated as EFL × sin θ.

[0026] If the galvano scanner unit 32 tilts the laser beam by an angle θ in the direction opposite to the direction shown in Fig. 3, the irradiation position of the laser beam on the metal sheet W can be displaced by a distance Δs in the direction opposite to the direction shown in Fig. 3. The distance Δs is a distance less than the radius of the opening 36a, and preferably a distance equal to or less than the maximum distance obtained by subtracting a predetermined margin from the radius of the opening 36a.

[0027] The NC device 50 controls the driving units 322 and 324 of the galvano scanner unit 32 to displace the laser beam in a predetermined direction within the surface of the sheet metal W. By displacing the laser beam, the beam spot formed on the surface of the sheet metal W can be displaced.

[0028] The laser processing machine 100 configured as described above cuts the metal sheet W with a laser beam emitted from the laser oscillator 10 to produce a product having a predetermined shape. A processing program for cutting the metal sheet W is stored in the processing program database 60. The NC device 50 reads out the processing program from the processing program database 60 and selects one of a plurality of processing condition files stored in the processing condition database 70. The NC device 50 controls the laser processing machine 100 to cut the metal sheet W based on the processing conditions set in the read processing program and the selected processing condition file.

[0029] 4 and 5, a description will be given of how the NC device 50 specifically controls the movement mechanism and the beam displacement mechanism. As shown in FIG. 4, the NC device 50 has, as its functional configuration, an NC control unit 51, a filter control unit 52, a movement mechanism control unit 53, and a beam displacement control unit 54. These can be functionally realized by a central processing unit provided in the NC device 50. When an instruction to read a machining program is given by the operation unit 40, the NC control unit 51 reads the specified machining program from the machining program database 60. Based on the read machining program, the NC control unit 51 acquires information indicating the machining start position and machining end position for cutting the metal sheet W.

[0030] As will be described later, the filter control unit 52 generates a movement command signal for moving the laser beam from the processing start position to the processing end position, and based on the movement command signal, generates a main movement command signal MCS for controlling the movement mechanism control unit 53 and a sub movement command signal SCS for controlling the beam displacement control unit 54. The filter control unit 52 supplies the main movement command signal MCS to the movement mechanism control unit 53 and supplies the sub movement command signal SCS to the beam displacement control unit 54.

[0031] A movement mechanism consisting of X-axis carriage 22 and Y-axis carriage 23 (hereinafter referred to as movement mechanisms 22 and 23) has drive units 220 and 230 that drive movement mechanisms 22 and 23, respectively. A movement mechanism control unit 53 controls drive unit 220 or 230, or both drive units 220 and 230, based on a main movement command signal MCS. A beam displacement control unit 54 controls drive unit 322 or 324 of galvano scanner unit 32, or both drive units 322 and 324, based on a sub movement command signal SCS.

[0032] 5, the filter control unit 52 has an interpolation calculation unit 521, a low-pass filter (hereinafter referred to as LPF) 522, a delay unit 523, and a subtractor 524. The interpolation calculation unit 521 performs interpolation calculation between the machining start position and the machining end position based on information indicating the machining start position and the machining end position for cutting the metal sheet W, and generates a movement command signal CS. The interpolation calculation unit 521 performs linear interpolation or circular interpolation between the machining start position and the machining end position in accordance with the machining program.

[0033] LPF 522 performs filtering processing to pass a frequency band below a predetermined cutoff frequency in movement command signal CS and block a frequency band above the cutoff frequency, thereby generating a main movement command signal MCS. A Bessel filter is preferably used as LPF 522. A Bessel filter is an IIR (Infinite Impulse Response) filter. Delay unit 523 delays movement command signal CS by a predetermined delay time and supplies a delayed movement command signal DCS to subtractor 524. Subtractor 524 subtracts main movement command signal MCS from delayed movement command signal DCS output from delay unit 523 to generate a secondary movement command signal SCS.

[0034] In Figure 6, the solid line indicates the movement trajectory of the machining head 35 in response to the movement command signal CS, and the dashed line indicates the movement trajectory of the machining head 35 in response to the main movement command signal MCS. The movement mechanism control unit 53 controls the drive unit 220 or 230, or the drive units 220 and 230, to move the machining head 35 based on the main movement command signal MCS rather than the movement command signal CS. Therefore, the movement mechanisms 22 and 23 move the machining head 35 at a gentle angle. The movement command signal CS indicating the movement trajectory shown in Figure 6 can be generated by combining linear interpolation and circular interpolation in the interpolation calculation unit 521.

[0035] The beam displacement control unit 54 controls the drive unit 322 or 324 of the galvanometer scanner unit 32, or both the drive units 322 and 324, based on the sub-movement command signal SCS, which is the difference between the movement command signal CS and the main movement command signal MCS. Therefore, the galvanometer scanner unit 32 displaces the laser beam so as to compensate for the difference between the movement trajectory based on the movement command signal CS and the movement trajectory based on the main movement command signal MCS. In this way, the laser processing machine 100 can move the laser beam irradiated onto the metal sheet W along the movement trajectory based on the movement command signal CS, while moving the processing head 35 along the movement trajectory based on the main movement command signal MCS.

[0036] According to the laser processing machine 100, there is no need to temporarily stop the processing head 35 at a corner of the movement trajectory or to significantly slow down the movement speed of the processing head 35, and therefore the processing time can be shortened.

[0037] Next, a specific method for accurately positioning the laser beam within the opening 36a of the nozzle 36 will be described using Figures 7 to 21. Here, it is assumed that the movement mechanisms 22 and 23 move the machining head 35 only in the X-axis direction. The X-axis and Y-axis components of the movement command signal CS will be referred to as movement command signals CSx and CSy, respectively. The movement command signal CSy is 0. The main movement command signal MCS and the sub-movement command signal SCS based on the movement command signal CSx will be referred to as the main movement command signal MCSx and the sub-movement command signal SCSx, respectively. The beam displacement amounts by which the galvano scanner unit 32 displaces the laser beam within the opening 36a of the nozzle 36 in the X-axis and Y-axis directions will be referred to as beam displacement amounts BDx and BDy, respectively.

[0038] In FIG. 7, the solid line indicates a movement command generated by the movement command signal CSx, which linearly increases the machining axis speed of the machining head 35 in the X-axis direction from time 0, maintains a constant speed for a predetermined period of time, and then linearly decreases the speed. The machining axis speed is the speed at which the machining head 35 moves in the X-axis or Y-axis direction. The dashed line indicates a movement command generated by the main movement command signal MCSx, which is obtained by filtering the movement command signal CSx using the LPF 522. If the delay time of the delay device 523 is 0, the delayed movement command signal DCS will be the same as the movement command signal CS. Because the main movement command signal MCSx is delayed from the movement command signal CSx due to the time required for filtering by the LPF 522, the difference between the movement command signal CSx and the main movement command signal MCSx will be large.

[0039] Therefore, when the subtractor 524 subtracts the main movement command signal MCSx from the movement command signal CSx to generate the sub movement command signal SCSx, the sub movement command signal SCSx becomes a large value, and the beam displacement amount BDx then becomes a large value such that the laser beam does not fit within the opening 36a of the nozzle 36, as shown in FIG.

[0040] 9, the dashed dotted line indicates a movement command based on a delayed movement command signal DCSx, which is obtained by delaying movement command signal CS by delay device 523 by approximately the same amount of time required for LPF 522 to filter primary movement command signal MCSx. When subtractor 524 subtracts primary movement command signal MCSx from delayed movement command signal DCSx to generate secondary movement command signal SCSx, the secondary movement command signal SCSx becomes a small value. As a result, beam displacement amount BDx becomes a small value as shown in FIG. 10, and the laser beam is more likely to fit within opening 36a of nozzle 36.

[0041] That is, by adjusting the delay time of the movement command signal CS by the delay device 523, it is possible to adjust the amount of beam displacement by the galvano scanner unit 32. The larger the difference between the delayed movement command signal DCS output from the delay device 523 and the main movement command signal MCS output from the LPF 522, the larger the secondary movement command signal SCS becomes, and the larger the amount of beam displacement becomes. The smaller the difference, the smaller the secondary movement command signal SCS becomes, and the smaller the amount of beam displacement becomes.

[0042] When the group delay time of the LPF 522 is Td, the cutoff frequency is fc, and the order is n, the group delay time Td can be calculated by equation (1), and the cutoff frequency fc can be calculated by equation (2).

[0043]

number

[0044]

number

[0045] As an example, if the order n is 6 and the cutoff frequency fc is 25 Hz, the group delay time Td is calculated as 0.0297406 s = 29.7406 ms using equation (1). Figure 11 shows the movement command signal CSx, delayed movement command signal DCSx, and main movement command signal MCSx when the delay time of delay device 523 is set to the group delay time Td of 29.7406 ms. Figure 12A shows the beam displacement amount BDx at this time. The position of beam displacement amount BDy in the Y-axis direction is the center of the opening 36a of the nozzle 36.

[0046] If the control period of the NC device 50 is 1 ms, the filter control unit 52 cannot displace the laser beam in accordance with the delay time of 29.7406 ms, which has a fraction less than 1 ms and is set as the delay time of the delay unit 523. Therefore, as shown in FIG. 12A, the beam displacement amount BDx becomes a constant value of approximately -0.150 mm during the period when the machining head 35 moves at a constant speed, and the position of the laser beam deviates from the center of the opening 36a. During the period when the machining head 35 is accelerating, the beam displacement amount BDx includes a portion where the negative value gradually increases, and during the period when the machining head 35 is decelerating, the beam displacement amount BDx includes a portion where the positive value gradually increases.

[0047] The group delay time Td is rounded up to set the group delay time Td' to 30 ms. The cutoff frequency fc is calculated from equation (2) to be 24.784 Hz. FIG. 12B shows the beam displacement amount BDx when the delay time of the delay device 523 is 30 ms and the cutoff frequency fc of the LPF 522 is 24.784 Hz. As shown in FIG. 12B, the beam displacement amount BDx is a constant value of approximately 0 in the section where the movement of the processing head 35 is constant, and the position of the laser beam coincides with the center of the opening 36a. In other words, in the section where the movement of the processing head 35 is constant, the laser beam traveling within the opening 36a is located at the center of the opening 36a and is not displaced.

[0048] During the period when the processing head 35 is accelerating, the beam displacement amount BDx includes a portion where it is a constant negative value, and during the period when the processing head 35 is decelerating, the beam displacement amount BDx includes a portion where it is a constant positive value.

[0049] In this way, rather than first setting the cutoff frequency fc of LPF 522 and then determining the delay time of the movement command signal CS by the delay device 523, it is better to first set the delay time of the delay device 523 and then apply the delay time of the delay device 523 to the group delay time Td of LPF 522 to determine the cutoff frequency fc.

[0050] FIG. 13 shows the movement commands generated by the movement command signal CSx, delayed movement command signal DCSx, and main movement command signal MCSx when the delay time of the delay device 523 is 10 ms and the cutoff frequency fc of the LPF 522 is 74.352 Hz. The beam displacement BDx at this time is very small, as shown in FIG. 14. For example, to cut out square or rectangular parts from a metal sheet W, if the processing head 35 is moved in the X-axis and Y-axis directions under the same conditions as in FIG. 13 to cut the metal sheet W, the beam displacement is as shown in FIG. 15. The laser beam traveling through the opening 36a moves only slightly from the center. Here, the diameter (nozzle diameter) of the opening 36a is 2 mm.

[0051] FIG. 16 shows the movement commands generated by the movement command signal CSx, delayed movement command signal DCSx, and main movement command signal MCSx when the delay time of the delay device 523 is set to 70 ms and the cutoff frequency fc of the LPF 522 is set to 10.622 Hz. The beam displacement amount BDx at this time is large, as shown in FIG. 17. When the processing head 35 is moved in the X-axis and Y-axis directions to cut the metal sheet W under the same conditions as in FIG. 16, the beam displacement amount is as shown in FIG. 18. The laser beam traveling within the opening 36a moves from the center a distance greater than the radius of the opening 36a. As a result, the laser beam strikes the inner peripheral surface of the nozzle 36 around the opening 36a.

[0052] 19 shows the movement commands by the movement command signal CSx, delayed movement command signal DCSx, and main movement command signal MCSx when the delay time of the delay device 523 is set to 65 ms and the cutoff frequency fc of the LPF 522 is set to 11.439 Hz. The beam displacement amount BDx at this time is smaller than the beam displacement amount BDx shown in FIG. 17, as shown in FIG. 20. When the processing head 35 is moved in the X-axis and Y-axis directions to cut the metal sheet W under the same conditions as in FIG. 19, the beam displacement amount is as shown in FIG. 21. The laser beam traveling within the opening 36a moves from the center within a distance less than the radius of the opening 36a, allowing the laser beam to be accurately contained within the opening 36a.

[0053] The procedure for determining the maximum value of the beam displacement amount will be described using the flowchart shown in Fig. 22. The beam displacement amount is the beam displacement amounts BDx and BDy. In Fig. 22, the operator of the laser processing machine 100 sets the order n of the LPF 522 in step S1, and sets the delay time of the delay device 523 in step S2. The order of steps S1 and S2 may be reversed. In step S3, the operator applies the delay time of the delay device 523 to the group delay time Td of the LPF 522 to calculate the cutoff frequency fc.

[0054] In step S4, the operator determines whether the maximum beam displacement amount is an optimal value close to the radius of the opening 36a of the nozzle 36. The operator may check whether the maximum beam displacement amount is the optimal value using the actual laser processing machine 100, or may check whether the maximum beam displacement amount is the optimal value through simulation. The optimal value is the distance from the center of the opening 36a to a position a predetermined distance away from the edge of the opening 36a toward the center. The predetermined distance is, for example, 0.2 mm. If the nozzle diameter is 2 mm, the optimal value of the maximum beam displacement amount from the center of the opening 36a is 0.8 mm.

[0055] Setting the distance from the edge of the opening 36a to 0.2 mm prevents the laser beam from hitting the inner circumferential surface of the nozzle 36 around the opening 36a when the laser beam is displaced. Also, the laser beam is less likely to get too close to the edge of the opening 36a and cause heat damage to the nozzle 36. Furthermore, the amount of beam displacement can be made sufficiently large.

[0056] If the maximum value of the beam displacement amount is not the optimum value in step S4 (NO), the operator determines in step S5 whether the maximum value of the beam displacement amount is greater than the optimum value. If the maximum value of the beam displacement amount is greater than the optimum value (YES), the operator shortens the delay time of delay unit 523 in step S6, recalculates cutoff frequency fc, and returns the process to step S4. If the maximum value of the beam displacement amount is not greater than the optimum value (NO), the operator lengthens the delay time of delay unit 523 in step S7, recalculates cutoff frequency fc, and returns the process to step S4.

[0057] Steps S4 to S7 are repeated until the maximum value of the beam displacement amount reaches the optimum value in step S4. If the maximum value of the beam displacement amount reaches the optimum value in step S4, the operator finally determines the delay time of the delay device 523 and the cutoff frequency fc of the LPF 522, and ends the procedure for determining the beam displacement amount.

[0058] As described above, the laser processing machine 100 sets the cutoff frequency fc at which the laser beam displaced by the beam displacement mechanism will fit within the opening 36a by setting the order n of the LPF 522 and the delay time of the movement command signal CS by the delay device 523. Therefore, according to the laser processing machine 100, the processing head 35 is moved based on the main movement command signal MCS obtained by filtering the movement command signal CS, and the laser beam is displaced while accurately fitting within the opening 36a of the nozzle 36 based on the sub movement command signal SCS, which is the difference signal between the delayed movement command signal DCS and the main movement command signal MCS, thereby processing the sheet metal W.

[0059] The present invention is not limited to one or more of the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0060] 10 Laser oscillator 20 Laser processing unit 22 X-axis carriage (movement mechanism) 23 Y-axis carriage (movement mechanism) 30 Collimator Unit 31 Collimating lens 32 Galvano scanner unit (beam displacement mechanism) 33 Bend Mirror 34 focusing lens 35 Processing head 36 nozzles 40 Control section 50 NC device 51 NC control unit 52 Filter control section 53 Movement mechanism control unit 54 Beam displacement control section 60 Machining program database 70 Processing condition database 80 Assist gas supply device 100 Laser Processing Machine 321,323 Scan Mirror 220,230,322,324 Drive unit 521 Interpolation Calculation Unit 522 Low-pass filter 523 Delay 524 Subtractor W Sheet metal (workpiece)

Claims

1. a processing head having a circular opening at its tip and a nozzle attached thereto for emitting a laser beam for processing a workpiece from the opening; a moving mechanism that moves the machining head relative to the workpiece along a surface of the workpiece; a beam displacement mechanism that displaces the laser beam traveling within the aperture from the center of the aperture; a control device that controls the movement of the processing head by the movement mechanism and the displacement of the laser beam by the beam displacement mechanism; Equipped with The control device a low-pass filter that filters a movement command signal that moves the machining head from a machining start position to a machining end position in order to machine the workpiece, and generates a main movement command signal that moves the machining head by the movement mechanism; a delay unit that delays the movement command signal to generate a delayed movement command signal; a subtractor that subtracts the primary motion command signal from the delayed motion command signal to generate a secondary motion command signal that causes the beam displacement mechanism to displace the laser beam; and By setting the order of the low-pass filter and the delay time of the delay device, the cutoff frequency of the low-pass filter is set, which allows the laser beam displaced by the beam displacement mechanism to fit within the aperture. Laser processing machine.

2. 2. The laser processing machine according to claim 1, wherein the control device defines the distance from the center of the opening to a position a predetermined distance away from the edge of the opening in the direction of the center as the maximum displacement of the laser beam, and sets the cutoff frequency of the low-pass filter at which the maximum displacement is obtained.

3. A movement command signal for moving the machining head from the machining start position to the machining end position in order to machine the workpiece is filtered by a low-pass filter to generate a main movement command signal; delaying the movement command signal by a delay device to generate a delayed movement command signal; subtracting the primary movement command signal from the delayed movement command signal by a subtractor to generate a secondary movement command signal; Based on the main movement command signal, the machining head is moved along the surface of the workpiece relative to the workpiece by a movement mechanism; a beam displacement mechanism displaces a laser beam emitted from a circular opening at a tip end of a nozzle attached to the processing head based on the auxiliary movement command signal; By setting the order of the low-pass filter and the delay time of the delay device, the cutoff frequency of the low-pass filter is set, which allows the laser beam displaced by the beam displacement mechanism to fit within the aperture. A method for controlling a laser processing machine.

4. 4. A method for controlling a laser processing machine according to claim 3, wherein the distance from the center of the opening to a position a predetermined distance away from the edge of the opening in the direction of the center is defined as the maximum displacement of the laser beam, and the cutoff frequency of the low-pass filter at which the maximum displacement is obtained is set.

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