Laser processing machine and control method for laser processing machine

Abstract

To provide a laser processing machine that can suppress gouging. [Solution] Based on the main movement command signal MCSx, the control device accelerates the processing head, moves it at a constant speed, decelerates it, and stops it. At this time, during the period when the processing head is moving at a constant speed, based on the sub-movement command signal, the control device positions the laser beam behind the center of the nozzle opening in the direction of movement of the processing head, as shown by the beam displacement amount BDx (Figure 12D), and after the deceleration of the processing head begins, it moves the laser beam to the center of the opening and then to the front of the center of the opening in the direction of movement of the processing head.

Description

Technical Field

[0001] The present invention relates to a laser processing machine and a control method thereof.

Background Art

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

[0003] With the above configuration, the laser processing machine described in Patent Document 1 moves the processing head at an angle gentler than the actual angle when changing the cutting progress direction of the workpiece, which is the direction in which the processing head moves, at a relatively large angle. The beam displacement mechanism displaces the laser beam so as to compensate for the difference between the actual angle and the gentle angle. Therefore, the position of the laser beam irradiated on the workpiece becomes equivalent to that when the processing head moves at the actual angle, and the workpiece can be cut along the processing path indicated by the processing program. According to the laser processing machine described in Patent Document 1, it is not necessary to temporarily stop the processing head or significantly decelerate the moving speed of the processing head when changing the cutting progress direction of the workpiece, and the processing time can be shortened.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In laser processing machines configured as described above, it has been confirmed that processing defects known as gouging occur. There is a need for a laser processing machine and a control method for such a machine that can process a workpiece by suppressing gouging, moving the processing head based on a main movement command signal obtained by filtering the movement command signal, and displacing the laser beam based on a sub-movement command signal, which is the 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 comprises a processing head having a circular opening at its tip and a nozzle attached to which a laser beam for processing a workpiece is emitted from the opening; a moving mechanism for moving the processing head relative to the workpiece along the surface of the workpiece; a beam displacement mechanism for displacing the laser beam traveling within the opening from the center of the opening; and a control device for controlling the movement of the processing head by the moving mechanism and the displacement of the laser beam by the beam displacement mechanism, wherein the control device filters a movement command signal for moving the processing head from a processing start position to a processing end position in order to process the workpiece, and generates a low-pass filter for moving the processing head by the moving mechanism. The present invention provides a laser processing machine comprising a filter, a delay unit 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 sub-movement command signal that displaces the laser beam by the beam displacement mechanism, wherein, based on the main movement command signal, the processing head is accelerated, then moved at a constant speed, and then decelerated and stopped, and during the period when the processing head is moving at the constant speed, the laser beam is positioned behind the center of the aperture in the direction of movement of the processing head based on the sub-movement command signal, and after the deceleration of the processing head begins, the laser beam is moved to the center of the aperture and then moved forward in the direction of movement of the processing head.

[0007] A second aspect of one or more embodiments involves filtering a movement command signal for moving a machining head from a machining start position to a machining end position to machine a workpiece using a low-pass filter to generate a main movement command signal, delaying the movement command signal using a delayer 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 sub-movement command signal, moving the machining head relative to the workpiece along the surface of the workpiece using a movement mechanism based on the main movement command signal, and attaching the machining head using a beam displacement mechanism based on the sub-movement command signal. The present invention provides a control method for a laser processing machine that displaces a laser beam ejected from a circular opening at the tip of a nozzle, accelerates the processing head based on the main movement command signal, moves it at a constant speed, decelerates it, and stops it, and during the period when the processing head is moving at the constant speed, the laser beam is positioned behind the center of the opening in the direction of movement of the processing head based on the sub-movement command signal, and after the deceleration of the processing head begins, the laser beam is moved to the center of the opening and then forward of the center of the opening in the direction of movement 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 the movement command signal, while suppressing gouging, and the workpiece can be processed by displacing the laser beam based on a sub-movement command signal which is the difference signal between the delayed movement command signal and the main movement command signal. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows an example of the overall configuration of a laser processing machine according to one or more embodiments. [Figure 2]Figure 2 is a perspective view showing a detailed configuration example of a collimator unit and a processing head included in one or more embodiment of a laser processing machine. [Figure 3] Figure 3 is a diagram illustrating the displacement of the laser beam's irradiation position onto the workpiece due to the beam displacement mechanism. [Figure 4] Figure 4 is a block diagram showing an example of the functional configuration of an NC device included in a laser processing machine according to one or more embodiments. [Figure 5] Figure 5 is a block diagram showing a detailed configuration example of the filter control unit 52 in Figure 4. [Figure 6] Figure 6 shows an example of the movement trajectory of the machining head based on the movement command signal and the movement trajectory of the machining head based on the main movement command signal. [Figure 7] Figure 7 shows an example of machining axis speed based on movement commands using a movement command signal, a delayed movement command signal, and a main movement command signal. [Figure 8] Figure 8 shows the beam displacement when the movement commands, based on the movement command signal, delayed movement command signal, and main movement command signal, are as shown in Figure 7. [Figure 9] Figure 9 shows the beam displacement when cutting a workpiece by moving the machining head in the X-axis and Y-axis directions under the same conditions as in Figure 7. [Figure 10] Figure 10 shows an example of when gouging occurs during workpiece machining. [Figure 11] Figure 11 shows cases where gouging occurs and cases where gouging does not occur. [Figure 12A] Figure 12A shows the beam displacement in Case No. 1, where gouging occurs as shown in Figure 11. [Figure 12B] Figure 12B shows the beam displacement in case No. 2, where gouging occurs as shown in Figure 11. [Figure 12C] Figure 12C shows the beam displacement in case No. 3, where gouging does not occur, as shown in Figure 11. [Figure 12D]FIG. 12D is a diagram showing the beam displacement amount in Case No. 4 where the gousing shown in FIG. 11 does not occur. [Figure 13] FIG. 13 is a diagram comparing the displacement of the laser beam based on the beam displacement amount between Case No. 1 where the gousing shown in FIG. 11 occurs and Case No. 4 where the gousing does not occur.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, a laser processing machine and a control method for the laser processing machine according to one or more embodiments will be described with reference to the accompanying drawings.

[0011] In FIG. 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. The NC device 50 is connected to a processing program database 60 and a processing condition database 70 via, for example, 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 by computer equipment.

[0012] The processing program database 60 and the processing condition database 70 are external configurations of the laser processing machine 100, but the laser processing machine 100 may include the processing program database 60 and the processing condition database 70.

[0013] As the laser oscillator 10, a laser oscillator that amplifies the excitation light emitted from a laser diode and emits a laser beam having a predetermined wavelength, or a laser oscillator that directly uses the laser beam emitted from a laser diode is suitable. The laser oscillator 10 is, for example, a solid-state laser oscillator, a fiber laser oscillator, a disk laser oscillator, or 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 includes a processing table 21 on which a sheet metal W, which is a workpiece to be processed, is placed, a gantry-type 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 moving mechanism for moving the processing head 35 along the surface of the sheet metal W in the X-axis direction, the Y-axis direction, or an arbitrary combined direction of the X-axis and the Y-axis. The X-axis and the Y-axis may be referred to as processing axes.

[0016] Instead of moving the processing head 35 along the surface of the sheet metal W, the position of the processing head 35 may be fixed and the sheet metal W may be configured to move. The laser processing machine 100 only needs to include a moving mechanism for relatively moving the processing head 35 with respect to the surface of the sheet metal W.

[0017] The processing head 35 has a circular opening 36a at its tip, and a nozzle 36 for emitting a laser beam from the opening 36a is attached. The laser beam emitted from the opening 36a of the nozzle 36 is irradiated onto the sheet metal W. The assist gas supply device 80 supplies nitrogen, oxygen, a mixture of nitrogen and oxygen, or air as the assist gas to the processing head 35. During the processing of the sheet metal W, the assist gas is blown from the opening 36a onto the sheet metal W. The assist gas discharges the molten metal within the kerf width where the sheet metal W is melted.

[0018] As shown in Figure 2, the collimator unit 30 includes a collimating lens 31 that converts the divergent 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 downwards in the Z-axis direction perpendicular to the X and Y axes. The processing head 35 includes a focusing lens 34 that focuses the laser beam reflected by the bend mirror 33 and irradiates the sheet metal W.

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

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

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

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

[0023] Figure 3 shows a state in which either or both of the scan mirrors 321 and 323 are tilted, causing the laser beam irradiated onto the sheet metal W to be displaced. In Figure 3, the thin solid line bent by the bend mirror 33 and passing through the focusing lens 34 indicates the optical axis of the laser beam when the laser processing machine 100 is in its reference state.

[0024] More specifically, the operation of the galvanometer scanner unit 32, located in front of the bend mirror 33, changes the angle of the optical axis of the laser beam incident on the bend mirror 33, causing the optical axis to deviate from the center of the bend mirror 33. In Figure 3, for simplification, the incident position of the laser beam on the bend mirror 33 is assumed to be the same before and after the operation of the galvanometer scanner unit 32.

[0025] Assume 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 galvanometer 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 sheet metal W will be 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 × sinθ.

[0026] If the galvanometer scanner unit 32 tilts the laser beam by an angle θ in the opposite direction to that shown in Figure 3, the irradiation position of the laser beam onto the sheet metal W can be displaced by a distance Δs in the opposite direction to that shown in Figure 3. The distance Δs is less than the radius of the aperture 36a, and preferably less than or equal to the maximum distance, which is the radius of the aperture 36a minus a predetermined margin.

[0027] The NC device 50 can displace the laser beam in a predetermined direction within the plane of the sheet metal W by controlling the drive units 322 and 324 of the galvanometer scanner unit 32. 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 sheet metal W with a laser beam emitted from the laser oscillator 10 to produce a product having a predetermined shape. The processing program database 60 stores processing programs for cutting sheet metal W. The NC device 50 reads a processing program from the processing program database 60 and selects one of the processing condition files stored in the processing condition database 70. The NC device 50 controls the laser processing machine 100 to cut the sheet metal W based on the processing program read and the processing conditions set in the selected processing condition file.

[0029] Figures 4 and 5 will be used to explain how the NC device 50 specifically controls the movement mechanism and the beam displacement mechanism. As shown in Figure 4, the NC device 50 has a functional configuration comprising 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 the central processing unit of the NC device 50. When the operation unit 40 instructs the NC control unit 51 to read a processing program, it reads the instructed processing program from the processing program database 60. Based on the read processing program, the NC control unit 51 acquires information indicating the start position and end position for cutting the sheet metal W.

[0030] As described later, the filter control unit 52 generates a movement command signal to move 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 to control the movement mechanism control unit 53 and a sub-movement command signal SCS to control 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 the sub-movement command signal SCS to the beam displacement control unit 54.

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

[0032] As shown in Figure 5, the filter control unit 52 includes an interpolation calculation unit 521, a low-pass filter (LPF) 522, a delay unit 523, and a subtractor 524. The interpolation calculation unit 521 calculates the interpolation between the processing start position and the processing end position based on information indicating the processing start position and processing end position for cutting the sheet metal W, and generates a movement command signal CS. The interpolation calculation unit 521 performs linear interpolation or circular interpolation between the processing start position and the processing end position according to the processing program.

[0033] The LPF522 generates the main movement command signal MCS by performing a filtering process that allows frequency bands below a predetermined cutoff frequency to pass through the movement command signal CS and blocks frequency bands above the cutoff frequency. It is preferable to use a Bessel filter as the LPF522. The Bessel filter is an IIR (Infinite Impulse Response) filter. The delay unit 523 delays the movement command signal CS by a predetermined delay time and supplies the delayed movement command signal DCS to the subtractor 524. The subtractor 524 subtracts the main movement command signal MCS from the delayed movement command signal DCS output from the delay unit 523 to generate the sub-movement command signal SCS.

[0034] In Figure 6, the solid line shows the movement trajectory of the machining head 35 based on the movement command signal CS, and the dashed line shows the movement trajectory of the machining head 35 based on the main movement command signal MCS. The movement mechanism control unit 53 controls the drive unit 220 or 230, or both 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 showing the movement trajectory in Figure 6 can be generated in the interpolation calculation unit 521 by combining linear interpolation and circular interpolation.

[0035] The beam displacement control unit 54 controls the drive unit 322 or 324, or both, of the galvanometer scanner unit 32 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. Accordingly, the galvanometer scanner unit 32 displaces the laser beam to compensate for the difference between the movement trajectory determined by the movement command signal CS and the movement trajectory determined by the main movement command signal MCS. As a result, the laser processing machine 100 can move the processing head 35 along the movement trajectory determined by the main movement command signal MCS while moving the laser beam irradiated onto the sheet metal W along the movement trajectory determined by the movement command signal CS.

[0036] According to the laser processing machine 100, there is no need to temporarily stop the processing head 35 at the corners of its movement path or to significantly reduce the movement speed of the processing head 35, thus shortening the processing time.

[0037] Figure 7 shows an example of a movement command using a movement command signal CS, a delayed movement command signal DCS, and a main movement command signal MCS. Here, it is assumed that the movement mechanisms 22 and 23 move the processing 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. Movement command signal CSy is 0. The main movement command signal MCS and sub-movement command signal SCS based on the movement command signal CSx are referred to as main movement command signal MCSx and sub-movement command signal SCSx, respectively. The beam displacement amounts that the galvanometer scanner unit 32 displaces in the X-axis and Y-axis directions within the aperture 36a of the nozzle 36 are referred to as beam displacement amounts BDx and BDi, respectively.

[0038] In Figure 7, the solid line represents a movement command, 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 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 represents a movement command, MCSx, obtained by filtering the movement command signal CSx using the LPF 522. The dashed line represents a movement command, DCSx, obtained by delaying the movement command signal CS using the delay unit 523 for approximately the same amount of time required for filtering the main movement command signal MCSx by the LPF 522.

[0039] Figure 8 shows the beam displacement BDx. The beam displacement by the galvanoscanner unit 32 can be adjusted by adjusting the delay time of the movement command signal CS from the delay unit 523. The larger the difference between the delayed movement command signal DCS output from the delay unit 523 and the main movement command signal MCS output from the LPF 522, the larger the sub-movement command signal SCS becomes, and the larger the beam displacement. The smaller the difference, the smaller the sub-movement command signal SCS becomes, and the smaller the beam displacement.

[0040] If the group delay time of the LPF522 is Td, the cutoff frequency is fc, and the order is n, then the group delay time Td can be calculated using equation (1), and the cutoff frequency fc can be calculated using equation (2).

[0041]

number

[0042]

number

[0043] By setting the delay time of the delay element 523 to, for example, 65 ms, and applying the delay time of the delay element 523 to the group delay time Td of the LPF 522, the cutoff frequency fc can be determined, and the beam displacement BDx can be adjusted as shown in Figure 8. The position of the beam displacement BDy in the Y-axis direction is the center of the aperture 36a of the nozzle 36. The cutoff frequency fc of the LPF 522 is 11.439 Hz.

[0044] As shown in Figure 8, the beam displacement BDx includes a portion that is a negative constant value during the period when the processing head 35 is accelerating. The beam displacement BDx is zero in the section where the processing head 35 is moving at a constant speed, and the position of the laser beam coincides with the center of the aperture 36a. That is, in the section where the processing head 35 is moving at a constant speed, the laser beam traveling within the aperture 36a is located at the center of the aperture 36a and does not displace. The beam displacement BDx includes a portion that is a positive constant value during the period when the processing head 35 is decelerating. The diameter of the aperture 36a (nozzle diameter) is 2 mm. As shown in Figure 8, the beam displacement BDx is less than ±1.0 mm.

[0045] For example, to cut out a square or rectangular part from a 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, the beam displacement will be as shown in Figure 9. The laser beam traveling within the aperture 36a moves within less than the radius of the aperture 36a from the center, and the laser beam can be accurately contained within the aperture 36a. The laser processing machine 100 determines the cutoff frequency fc at which a beam displacement amount is obtained in which the laser beam displaced by the beam displacement mechanism is contained within the aperture 36a, by setting the order n of the LPF 522 and the delay time of the movement command signal CS by the delay unit 523.

[0046] In the laser processing machine 100 configured as described above, verification by the inventors confirmed that a processing defect called gouging occurs. Figure 10 shows an example of when gouging occurs when processing sheet metal W. In Figure 10, (a) is a partial plan view of the sheet metal W viewed from above, showing the state in which an attempt is made to cut out part P by cutting the outer circumference of a rectangular part P from the sheet metal W. Assume that the side of part P is cut by irradiating a laser beam in a straight line from corner c1 to corner c2. At this time, assume that the NC device 50 controls the processing axis speed of the processing head 35 as shown in Figure 10(b). In Figure 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 shown. Figure 10(c) shows the beam displacement amount BDx.

[0047] As shown in the hatched area in Figure 10(a), gouging occurs when the deceleration of the machining head 35 begins. As can be seen in Figure 10(c), gouging occurs at the moment when the laser beam located at the center of the aperture 36a is displaced forward.

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

[0049] Figure 12A shows the beam displacement BDx for Case No. 1 shown in Figure 11. In Figure 12A, similar to Figure 8, the beam displacement BDx is 0 in the section where the processing head 35 is moving at a constant speed, and the position of the laser beam coincides with the center of the aperture 36a. Figure 12B shows the beam displacement BDx for Case No. 2 shown in Figure 11. In Figure 12B, the beam displacement BDx is a small positive value in the section where the processing head 35 is moving at a constant speed, and the laser beam is positioned slightly forward in the direction of movement of the processing head 35.

[0050] Figure 12C shows the beam displacement BDx for Case No. 3 shown in Figure 11. In Figure 12C, the beam displacement BDx is a constant value from -0.150 mm to -0.425 mm during the section where the processing head 35 is moving at a constant speed, and the laser beam is located behind the center of the aperture 36a in the direction of movement of the processing head 35. During the period when the processing head 35 is accelerating, the beam displacement BDx includes a portion where the negative value increases sequentially, and during the period when the processing head 35 is decelerating, the beam displacement BDx includes a portion where the positive value increases sequentially.

[0051] Figure 12D shows the beam displacement BDx for Case No. 4 shown in Figure 11. In Figure 12D, the beam displacement BDx is a constant value from -0.150 mm to -0.325 mm during the section where the processing head 35 is moving at a constant speed, and the laser beam is located behind the center of the aperture 36a in the direction of movement of the processing head 35. During the period when the processing head 35 is accelerating, the beam displacement BDx includes a portion where the negative value increases sequentially, and during the period when the processing head 35 is decelerating, the beam displacement BDx includes a portion where the positive value increases sequentially.

[0052] In Figures 12A and 12B, gouging occurs. Based on the main movement command signal MCS, the movement mechanism control unit 53 accelerates the processing head 35, moves it at a constant speed, decelerates it, and stops it. As shown in Figure 12A, it was confirmed that gouging occurs when, during the period when the processing head 35 is moving at a constant speed, the beam displacement amount BDx is set to 0 based on the sub-movement command signal SCS, and the laser beam is positioned at the center of the aperture 36a of the nozzle 36. As shown in Figure 12B, it was confirmed that gouging occurs when, during the period when the processing head 35 is moving at a constant speed, the beam displacement amount BDx is set to a positive value based on the sub-movement command signal SCS, and the laser beam is positioned forward of the center of the aperture 36a of the nozzle 36 in the direction of movement of the processing 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 the period when the processing head 35 is moving at a constant speed, the beam displacement amount BDx is set to a negative value based on the sub-movement command signal SCS, thereby positioning the laser beam behind the center of the aperture 36a of the nozzle 36 in the direction of movement of the processing head 35. In Figures 12C and 12D, the beam displacement control unit 54 moves the laser beam to the center of the aperture 36a after the deceleration of the processing head 35 has started, and then moves it forward in the direction of movement of the processing head 35 beyond the center of the aperture 36a.

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

[0055] As shown in Figure 8 or Figure 10(c), the order n of the LPF522, the cutoff frequency fc, and the delay time of the delay element 523 are set so that the beam displacement BDx is 0 during the period when the processing head 35 is moving at a constant speed. By changing the cutoff frequency fc while maintaining the delay time of the delay element 523, the beam displacement BDx can be changed as shown in Figures 12C and 12D. Since the cutoff frequency fc of the LPF522 can be adjusted in 0.01Hz increments, it is possible to set the beam displacement BDx to the desired characteristics.

[0056] In this way, when the NC device 50 cuts the sheet metal W, it accelerates the processing head 35, moves it at a constant speed, and then decelerates and stops it. During the period when the processing head 35 is moving at a constant speed, the laser beam is positioned behind the center of the aperture 36a in the direction of movement of the processing head 35. In addition, after the deceleration of the processing head 35 begins, the NC device 50 moves the laser beam to the center of the aperture 36a, and then moves it forward in the direction of movement of the processing head 35 in the direction of movement of the processing head 35. As a result, the laser processing machine 100 can cut the sheet metal 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 aperture 36a moves within a radius less than the aperture 36a from the center, and the state in which the laser beam is contained within the aperture 36a is maintained.

[0058] The present invention is not limited to the one or more embodiments described above, and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0059] 10. Laser Oscillator 20 Laser Processing Units 22 X-axis carriage (movement mechanism) 23. Y-axis carriage (movement mechanism) 30 Collimator Units 31 Collimating Lens 32. Galvanometer Scanner Unit (Beam Displacement Mechanism) 33 Bend Mirror 34 Focusing lens 35 Machining heads 36 nozzles 40 Control section 50 NC device 51 NC Control Unit 52 Filter Control Unit 53 Mobile Mechanism Control Unit 54 Beam displacement control unit 60 Processing Program Database 70 Processing Conditions Database 80 Assist gas supply device 100 laser processing machines 321,323 Scan Mirror 220, 230, 322, 324 Drive unit 521 Interpolation Calculation Unit 522 Low-Pass Filter 523 Delay device 524 Subtractor W Sheet metal (work)

Claims

1. A processing head having a circular opening at its tip, with a nozzle attached to which a laser beam for processing a workpiece is emitted from the opening, A moving mechanism for moving the machining head along the surface of the workpiece relative to 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 moving mechanism and the displacement of the laser beam by the beam displacement mechanism, Equipped with, The control device is A low-pass filter filters a movement command signal that moves the machining head from the machining start position to the 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 aforementioned movement command signal to generate a delayed movement command signal, A subtractor that subtracts the main movement command signal from the delayed movement command signal to generate a sub-movement command signal that displaces the laser beam by the beam displacement mechanism, It has, When the processing 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 when the processing head is moving at the constant speed, the laser beam is positioned behind the center of the aperture in the direction of movement of the processing head based on the sub-movement command signal, and after the deceleration of the processing head begins, the laser beam is moved to the center of the aperture and then moved forward in the direction of movement of the processing head in the direction of movement of the aperture. Laser processing machine.

2. A movement command signal that moves 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. The aforementioned movement command signal is delayed by a delay device to generate a delayed movement command signal. A subtractor subtracts the main movement command signal from the delayed movement command signal to generate a sub-movement command signal. Based on the main movement command signal, the movement mechanism moves the machining head along the surface of the workpiece relative to the workpiece. Based on the aforementioned sub-movement command signal, the beam displacement mechanism displaces the laser beam emitted from the circular opening at the tip of the nozzle attached to the processing head. When the processing 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 when the processing head is moving at the constant speed, the laser beam is positioned behind the center of the aperture in the direction of movement of the processing head based on the sub-movement command signal. After the deceleration of the processing head begins, based on the sub-movement command signal, the laser beam is moved to the center of the aperture, and then moved forward in the direction of movement of the processing head from the center of the aperture. A control method for a laser processing machine.

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