Laser processing machine and method for controlling the laser processing machine

Abstract

A laser processing machine capable of suppressing gouging is provided. [Solution] Based on a primary movement command signal MCSx, the control device accelerates the machining head, moves it at a constant speed, and then decelerates and stops it. During the period when the machining head is moving at a constant speed, the control device positions the laser beam rearward of the center of the nozzle opening in the direction of movement of the machining head, as shown by a beam displacement amount BDx (Fig. 12D), based on a secondary movement command signal, and after the machining head starts to decelerate, moves the laser beam to the center of the opening and then forward of the center of the opening in the direction of movement of the machining head.

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 along the processing path specified 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] It has been confirmed that a processing defect known as gouging occurs in a laser processing machine configured as described above. 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 a processing head based on a main movement command signal obtained by filtering a movement command signal, and displacing a laser beam based on a sub-movement command signal that is a difference signal between the delayed movement command signal and the main movement command signal, while suppressing gouging. [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 is 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 filter, 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 displaces the laser beam by the beam displacement mechanism, and when the machining head is accelerated and then moved at a constant speed based on the main movement command signal and then decelerated and stopped, the laser beam is positioned further rearward in the movement direction of the machining head than the center of the opening based on the secondary movement command signal during the period when the machining head is being moved at the constant speed, and after the machining head starts to decelerate, the laser beam is moved to the center of the opening and then moved further forward in the movement direction of the machining head than the center of the opening.

[0007] A second aspect of one or more embodiments is a method for processing a workpiece by filtering a movement command signal for moving a processing head from a processing start position to a processing end position using a low-pass filter 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, and moving a beam attached to the processing head using a beam displacement mechanism based on the secondary movement command signal. and displacing a laser beam emitted from a circular opening at the tip of a nozzle attached to the laser processing machine, and when accelerating the processing head and then moving it at a constant speed based on the main movement command signal and then decelerating and stopping it, during the period when the processing head is moving at the constant speed, based on the sub-movement command signal, positioning the laser beam behind the center of the opening in the movement direction of the processing head, and after the processing head starts to decelerate, moving the laser beam to the center of the opening and then moving it forward in the movement direction of the processing head based on the sub-movement command signal. [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 can be moved based on a main movement command signal obtained by filtering a movement command signal while suppressing gouging, and the laser beam can be displaced based on a sub-movement command signal which is a differential signal between the delayed movement command signal and the main movement command signal, thereby processing the workpiece. [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 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 8] FIG. 8 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 9] FIG. 9 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 10] FIG. 10 is a diagram showing an example of a case where gouging occurs during machining of a workpiece. [Figure 11] FIG. 11 is a diagram showing a case where gouging occurs and a case where gouging does not occur. [Figure 12A] FIG. 12A is a diagram showing the amount of beam displacement in Case No. 1 in which gouging occurs as shown in FIG. [Figure 12B] FIG. 12B is a diagram showing the amount of beam displacement in Case No. 2 in which gouging occurs as shown in FIG. [Figure 12C] FIG. 12C is a diagram showing the amount of beam displacement in Case No. 3 in which no gouging occurs as shown in FIG. [Figure 12D]FIG. 12D is a diagram showing the amount of beam displacement in Case No. 4 in which no gouging occurs as shown in FIG. [Figure 13] FIG. 13 is a diagram comparing the laser beam displacement based on the beam displacement amount between Case No. 1 in which gouging occurs and Case No. 4 in which gouging does not occur, as shown in FIG. 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] FIG. 7 shows an example of a movement command signal CS, a delayed movement command signal DCS, and a main movement command signal MCS. Here, 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 are 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 are 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 in the X-axis and Y-axis directions within the opening 36a of the nozzle 36 are referred to as beam displacement amounts BDx and BDy, respectively.

[0038] In Figure 7, the solid line indicates a movement command generated by the movement command signal CSx to linearly increase the machining axis speed of the machining head 35 in the X-axis direction from time 0, maintain a constant speed for a predetermined period of time, and then linearly decrease 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. The dot-dash line indicates a movement command generated by the delayed movement command signal DCSx, which is obtained by delaying the movement command signal CS using the delay unit 523 by approximately the same time as the time required for the LPF 522 to filter the main movement command signal MCSx.

[0039] 8 shows the beam displacement amount BDx. The beam displacement amount by the galvano scanner unit 32 can be adjusted by adjusting the delay time of the movement command signal CS by the delay device 523. 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 beam displacement amount becomes. The smaller the difference, the smaller the secondary movement command signal SCS becomes, and the smaller the beam displacement amount becomes.

[0040] 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).

[0041]

number

[0042]

number

[0043] If the delay time of delay device 523 is set to, for example, 65 ms and applied to the group delay time Td of LPF 522 to determine the cutoff frequency fc, the beam displacement amount BDx can be adjusted as shown in Figure 8. The position of beam displacement amount BDy in the Y-axis direction is the center of the opening 36a of the nozzle 36. The cutoff frequency fc of LPF 522 is 11.439 Hz.

[0044] As shown in FIG. 8, the beam displacement amount BDx includes a portion that is a constant negative value during the period when the machining head 35 is accelerating. The beam displacement amount BDx is 0 during the period when the machining head 35 is moving at a constant speed, and the position of the laser beam coincides with the center of the opening 36a. In other words, during the period when the machining head 35 is moving at a constant speed, the laser beam traveling within the opening 36a is located at the center of the opening 36a and does not displace. The beam displacement amount BDx includes a portion that is a constant positive value during the period when the machining head 35 is decelerating. The diameter (nozzle diameter) of the opening 36a is 2 mm. As shown in FIG. 8, the beam displacement amount BDx is less than ±1.0 mm.

[0045] For example, to cut out square or rectangular parts from sheet metal W, if the processing head 35 is moved in the X-axis and Y-axis directions under the same conditions as in Figure 7 to cut the sheet metal W, the beam displacement amount will be as shown in Figure 9. The laser beam traveling through the opening 36a moves from the center within less than the radius of the opening 36a, allowing the laser beam to accurately fit within the opening 36a. The laser processing machine 100 determines 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.

[0046] The inventors' verification of the laser processing machine 100 configured as described above confirmed that a processing defect known as gouging occurs. FIG. 10 illustrates an example of gouging occurring during processing of a metal sheet W. In FIG. 10, (a) is a partial plan view of the metal sheet W viewed from above, showing the state in which the periphery of a rectangular part P is being cut out of the metal sheet W. Assume that the laser beam is irradiated in a straight line from corner c1 to corner c2 of the part P to cut the edge of the part P. At this time, the NC device 50 controls the processing axis speed of the processing head 35 as shown in FIG. 10(b). In FIG. 10(b), in addition to the main movement command signal MCSx based on the movement command signal CSx, the main movement command signal MCSy based on the movement command signal CSy is also shown. FIG. 10(c) illustrates the beam displacement BDx.

[0047] As shown by hatching in Figure 10(a), gouging occurs when the processing head 35 starts to decelerate. As can be seen from Figure 10(c), gouging occurs when the laser beam located at the center of the opening 36a is displaced forward.

[0048] Further testing by the inventors confirmed two cases: one in which gouging occurred and one in which the sheet metal W could be cut normally without gouging, as shown in Figure 11. In Case No. 1, the order n was set to 7, the cutoff frequency fc was set to 20.013 Hz, and the maximum beam displacement was set to ±0.350. In Case No. 2, the order n was set to 6, the cutoff frequency fc was set to 25.623 Hz, and the maximum beam displacement was set to ±0.186. In Case No. 3, the order n was set to 7, the cutoff frequency fc was set to 20.163 Hz, and the maximum beam displacement was set to ±0.629. In Case No. 4, the order n was set to 6, the cutoff frequency fc was set to 25.803 Hz, and the maximum beam displacement was set to ±0.355.

[0049] Fig. 12A shows the beam displacement amount BDx for Case No. 1 shown in Fig. 11. As with Fig. 8, the beam displacement amount BDx shown in Fig. 12A is 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. Fig. 12B shows the beam displacement amount BDx for Case No. 2 shown in Fig. 11. The beam displacement amount BDx shown in Fig. 12B is a small positive value in the section where the movement of the processing head 35 is constant, and the laser beam is positioned slightly forward in the movement direction of the processing head 35.

[0050] Fig. 12C shows the beam displacement amount BDx for Case No. 3 shown in Fig. 11. The beam displacement amount BDx shown in Fig. 12C is a constant value ranging from -0.150 mm to -0.425 mm during the section where the movement of the processing head 35 is constant, and the laser beam is positioned further rearward in the movement direction of the processing head 35 than the center of the opening 36a. During the period when the processing head 35 is accelerating, the beam displacement amount BDx includes a portion where the negative value gradually increases, and during the period when the processing head 35 is decelerating, the beam displacement amount BDx includes a portion where the positive value gradually increases.

[0051] Fig. 12D shows the beam displacement amount BDx for Case No. 4 shown in Fig. 11. The beam displacement amount BDx shown in Fig. 12D is a constant value ranging from -0.150 mm to -0.325 mm during the section where the movement of the processing head 35 is constant, and the laser beam is positioned further rearward in the movement direction of the processing head 35 than the center of the opening 36a. During the period when the processing head 35 is accelerating, the beam displacement amount BDx includes a portion where the negative value gradually increases, and during the period when the processing head 35 is decelerating, the beam displacement amount BDx includes a portion where the positive value gradually increases.

[0052] Gouging occurs in Figures 12A and 12B. Based on the primary movement command signal MCS, the movement mechanism control unit 53 accelerates the machining head 35, then moves it at a constant speed, and then decelerates and stops it. As shown in Figure 12A, gouging was confirmed to occur when, while the machining head 35 is moving at a constant speed, the beam displacement amount BDx is set to 0 based on the secondary movement command signal SCS to position the laser beam at the center of the opening 36a of the nozzle 36. As shown in Figure 12B, gouging was confirmed to occur when, while the machining head 35 is moving at a constant speed, the beam displacement amount BDx is set to a positive value based on the secondary movement command signal SCS to position the laser beam forward of the center of the opening 36a of the nozzle 36 in the movement direction of the machining head 35.

[0053] On the other hand, gouging does not occur in Figures 12C and 12D. As shown in Figures 12C and 12D, it was confirmed that gouging does not occur when, during a period in which the machining head 35 is moved at a constant speed, the beam displacement amount BDx is set to a negative value based on the sub-movement command signal SCS, and the laser beam is positioned rearward of the center of the opening 36a of the nozzle 36 in the movement direction of the machining head 35. In Figures 12C and 12D, after the machining head 35 starts to decelerate, the beam displacement control unit 54 moves the laser beam to the center of the opening 36a and then moves it forward of the center of the opening 36a in the movement direction of the machining head 35.

[0054] Figure 13 is a diagram comparing the laser beam displacement based on the beam displacement amount BDx shown in Figure 12A and the beam displacement amount BDx shown in Figure 12D. The white circle shown in the opening 36a indicates the position of the laser beam. The dashed arrow shown in the opening 36a indicates the displacement of the laser beam. The beam displacement amount BDx shown in Figures 12C and 12D may be set, for example, as follows.

[0055] As shown in Figure 8 or Figure 10(c), the order n and cutoff frequency fc of the LPF 522 and the delay time of the delay device 523 are set so that the beam displacement amount BDx becomes 0 while the processing head 35 is moving at a constant speed. By changing the cutoff frequency fc while maintaining the delay time of the delay device 523, the beam displacement amount BDx can be changed as shown in Figures 12C and 12D. The cutoff frequency fc of the LPF 522 can be adjusted in 0.01 Hz increments, so it is possible to set the beam displacement amount BDx to the desired characteristics.

[0056] In this way, when cutting the metal sheet W, the NC device 50 accelerates the machining head 35, moves it at a constant speed, and then decelerates and stops it, and during the period when the machining head 35 is moving at a constant speed, the NC device 50 positions the laser beam rearward of the center of the opening 36a in the movement direction of the machining head 35. In addition, after the machining head 35 starts to decelerate, the NC device 50 moves the laser beam to the center of the opening 36a and then moves it forward of the center of the opening 36a in the movement direction of the machining head 35. This allows the laser processing machine 100 to cut the metal sheet W while suppressing gouging.

[0057] Even when the beam displacement control unit 54 controls the beam displacement amount BDx as shown in Figures 12C and 12D, the laser beam traveling within the opening 36a moves from the center within a distance less than the radius of the opening 36a, and the laser beam is maintained within the opening 36a.

[0058] 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]

[0059] 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 When the machining head is accelerated and then moved at a constant speed based on the main movement command signal, and then decelerated and stopped, during the period in which the machining head is moved at the constant speed, the laser beam is positioned on the rear side of the center of the opening in the moving direction of the machining head based on the sub-movement command signal, and after the machining head starts to decelerate, the laser beam is moved to the center of the opening and then moved to the front side of the center of the opening in the moving direction of the machining head. Laser processing machine.

2. 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; When the machining head is accelerated and then moved at a constant speed based on the main movement command signal, and then decelerated and stopped, during the period in which the machining head is moved at the constant speed, the laser beam is positioned on the rear side of the center of the opening in the movement direction of the machining head based on the sub-movement command signal, After the processing head starts to decelerate, the laser beam is moved to the center of the opening based on the auxiliary movement command signal, and then moved forward of the center of the opening in the movement direction of the processing head. A method for controlling a laser processing machine.

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