Laser processing machine and control method for laser processing machine

Abstract

The present invention provides a laser processing machine that can process a workpiece by precisely positioning and displacing the laser beam within the nozzle opening. [Solution] The low-pass filter 522 filters the movement command signal CS to generate a main movement command signal MCS that moves the processing head by the movement mechanism. The delay unit 523 delays the movement command signal CS to generate a delayed movement command signal DCS. The subtractor 524 subtracts the main movement command signal MCS from the delayed movement command signal DCS to generate a sub-movement command signal SCS that displaces the laser beam by the beam displacement mechanism. By setting the order of the low-pass filter 522 and the delay time by the delay unit 523, the cutoff frequency of the low-pass filter 522 is set to obtain a laser beam displacement amount that keeps the laser beam displaced by the beam displacement mechanism within the nozzle opening.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 describes a laser processing machine including a moving mechanism that moves a processing head and a beam displacement mechanism that displaces 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 a filtering process 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 a sub-movement command signal that is the difference signal output from the subtractor.

[0003] With the above configuration, when the laser processing machine described in Patent Document 1 changes the cutting progress direction of the workpiece, which is the direction in which the processing head moves, at a relatively large angle, the processing head is moved at an angle gentler than the actual 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, when changing the cutting progress direction of the workpiece, it is not necessary to temporarily stop the processing head or significantly decelerate the moving speed of the processing head, and the processing time can be shortened.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[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 such a machine that can move the processing head based on a main movement command signal obtained by filtering the movement command signal, and then precisely displace the laser beam within the nozzle opening while processing the workpiece 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 the movement command signal for moving the processing head from a processing start position to a processing end position in order to process the workpiece. The present invention provides a laser processing machine comprising: a low-pass filter that performs a processing to generate a main movement command signal for moving the processing head by the movement mechanism; 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 for displacing the laser beam by the beam displacement mechanism, wherein the cutoff frequency of the low-pass filter is set by setting the order of the low-pass filter and the delay time of the delay unit, thereby obtaining a displacement amount of the laser beam such 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 control method for a laser processing machine, which involves filtering a movement command signal that moves the processing head from a processing start position to a processing end position in order to process a workpiece using a low-pass filter to generate a main movement command signal, delaying the movement command signal using a delay unit 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 processing head along the 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 sub-movement command signal, and setting the cutoff frequency of the low-pass filter to obtain a displacement amount of the laser beam such that the laser beam displaced by the beam displacement mechanism fits within the opening, by setting the order of the low-pass filter and the delay time of the delay unit. [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 the movement command signal, and the workpiece can be processed by displacing the laser beam while accurately positioning it within the nozzle opening 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 a movement command using a movement command signal and a main movement command signal, with the delay time of the movement command signal set to 0. [Figure 8] Figure 8 shows the beam displacement when the delay time of the movement command signal is set to 0, and the movement command by the movement command signal and the main movement command signal is as shown in Figure 7. [Figure 9] Figure 9 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 10] Figure 10 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 9. [Figure 11] Figure 11 shows the machining axis speeds resulting from the movement command signal, the delayed movement command signal, and the main movement command signal, when the order of the low-pass filter in Figure 5 is set to 6, the cutoff frequency to 25 Hz, and the delay time of the delay element to the group delay time of the low-pass filter. [Figure 12A] Figure 12A 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 11. [Figure 12B] Figure 12B shows the beam displacement when the movement command is given by a movement command signal, a delayed movement command signal, and a main movement command signal, with the low-pass filter order set to 6, the cutoff frequency to 24.784 Hz, and the delay time of the delay element set to 30 ms, as shown in Figure 5. [Figure 13]FIG. 13 is a diagram showing the machining axis speed according to the movement command by the movement command signal, the delayed movement command signal, and the main movement command signal when the delay time of the delay device is 10 ms and the cut-off frequency of the low-pass filter is 74.352 Hz. [Figure 14] FIG. 14 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. 13. [Figure 15] FIG. 15 is a diagram showing the beam displacement amount when the workpiece is cut by moving the machining head in the X-axis direction and the Y-axis direction under the same conditions as in FIG. 13. [Figure 16] FIG. 16 is a diagram showing the machining axis speed according to the movement command by the movement command signal, the delayed movement command signal, and the main movement command signal when the delay time of the delay device is 70 ms and the cut-off frequency of the low-pass filter is 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. 16. [Figure 18] FIG. 18 is a diagram showing the beam displacement amount when the workpiece is cut by moving the machining head in the X-axis direction and the Y-axis direction under the same conditions as in FIG. 16. [Figure 19] FIG. 19 is a diagram showing the machining axis speed according to the movement command by the movement command signal, the delayed movement command signal, and the main movement command signal when the delay time of the delay device is 65 ms and the cut-off frequency of the low-pass filter is 11.439 Hz. [Figure 20] FIG. 20 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. 19. [Figure 21] FIG. 21 is a diagram showing the beam displacement amount when the workpiece is cut by moving the machining head in the X-axis direction and the Y-axis direction under the same conditions as in FIG. 19. [Figure 22] FIG. 22 is a flowchart showing the procedure for determining the beam displacement amount.

BEST MODE 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 a computer device.

[0012] Although the processing program database 60 and the processing condition database 70 are external configurations of the laser processing machine 100, 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 excitation light emitted from a laser diode and emits a laser beam having a predetermined wavelength, or a laser oscillator that directly uses a 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 having 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 having a wavelength of 1060 nm to 1080 nm, and the DDL oscillator emits a laser beam having a wavelength of 910 nm to 950 nm.

[0015] The laser processing unit 20 includes a processing table 21 on which the sheet metal W 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 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-axis and Y-axis. The X-axis and Y-axis are sometimes referred to as processing axes.

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

[0017] The processing head 35 is fitted with a nozzle 36 that has a circular opening 36a at its tip and emits a laser beam from the opening 36a. 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 an assist gas to the processing head 35. During processing of the sheet metal W, the assist gas is blown onto the sheet metal W from the opening 36a. The assist gas discharges the molten metal within the kerf width of the melted sheet metal W.

[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] Next, using Figures 7 to 21, a specific method for accurately positioning the laser beam within the aperture 36a of the nozzle 36 will be explained. Here, it is assumed that the moving 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 will be 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 will be 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 within the aperture 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 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. If the delay time by the delay unit 523 is 0, the delayed movement command signal DCS will be the same as the movement command signal CS. The main movement command signal MCSx lags behind the movement command signal CSx due to the time required for filtering by the LPF 522, so the difference between the movement command signal CSx and the main movement command signal MCSx becomes 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. As a result, as shown in Figure 8, the beam displacement amount BDx becomes a large value that prevents the laser beam from staying within the aperture 36a of the nozzle 36.

[0040] In Figure 9, the dashed line indicates a movement command using a delayed movement command signal DCSx, which is generated by delaying the movement command signal CS by the delay unit 523 for approximately the same amount of time required for filtering the main movement command signal MCSx by the LPF 522. When the subtractor 524 subtracts the main movement command signal MCSx from the delayed movement command signal DCSx to generate a sub-movement command signal SCSx, the sub-movement command signal SCSx becomes a small value. As a result, the beam displacement BDx becomes a small value, as shown in Figure 10, and the laser beam is more likely to stay within the aperture 36a of the nozzle 36.

[0041] In other words, the amount of beam displacement by the galvanometer scanner unit 32 can be adjusted by adjusting the delay time of the movement command signal CS by 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 becomes. The smaller the difference becomes, the smaller the sub-movement command signal SCS becomes, and the smaller the beam displacement becomes.

[0042] 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).

[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 from equation (1) as 0.0297406 s = 29.7406 ms. Figure 11 shows the movement command signal CSx, the delayed movement command signal DCSx, and the main movement command signal MCSx when the delay time of the delay unit 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 the beam displacement amount BDy in the Y-axis direction is the center of the opening 36a of the nozzle 36.

[0046] Assuming the control cycle 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 fractional part of less than 1 ms, set as the delay time of the delay unit 523. Therefore, as shown in Figure 12A, the beam displacement amount BDx becomes a constant value of approximately -0.150 mm in the section where the movement of the processing head 35 is constant speed, and the position of the laser beam shifts from the center of the aperture 36a. During the period when the processing head 35 is accelerating, the beam displacement amount BDx includes a portion in which the negative value increases sequentially, and during the period when the processing head 35 is decelerating, the beam displacement amount BDx includes a portion in which the positive value increases sequentially.

[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. Figure 12B shows the beam displacement BDx when the delay time of the delay unit 523 is 30 ms and the cutoff frequency fc of the LPF 522 is 24.784 Hz. As shown in Figure 12B, the beam displacement BDx is a constant value of almost 0 in the section where the movement of the processing head 35 is constant speed, and the position of the laser beam coincides with the center of the aperture 36a. That is, in the section where the movement of the processing head 35 is constant speed, the laser beam traveling within the aperture 36a is located at the center of the aperture 36a and does not displace.

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

[0049] Thus, instead of first setting the cutoff frequency fc of the LPF522 and then determining the delay time of the movement command signal CS by the delay unit 523, it is better to first set the delay time of the delay unit 523 and then apply the delay time of the delay unit 523 to the group delay time Td of the LPF522 to determine the cutoff frequency fc.

[0050] Figure 13 shows the movement commands issued by the movement command signal CSx, the delayed movement command signal DCSx, and the main movement command signal MCSx, with the delay time of the delay element 523 set to 10 ms and the cutoff frequency fc of the LPF 522 set to 74.352 Hz. The beam displacement BDx at this time is a very small value, as shown in Figure 14. For example, to cut 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 13, the beam displacement will be as shown in Figure 15. The laser beam traveling within the aperture 36a moves only slightly from the center. Here, the diameter of the aperture 36a (nozzle diameter) is set to 2 mm.

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

[0052] Figure 19 shows the movement commands issued by the movement command signal CSx, the delayed movement command signal DCSx, and the main movement command signal MCSx, with the delay time of the delay element 523 set to 65 ms and the cutoff frequency fc of the LPF 522 set to 11.439 Hz. The beam displacement BDx at this time is smaller than the beam displacement BDx shown in Figure 17, as shown in Figure 20. Under the same conditions as in Figure 19, when the processing head 35 is moved in the X-axis and Y-axis directions to cut the sheet metal W, the beam displacement is as shown in Figure 21. 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.

[0053] The procedure for determining the maximum beam displacement is explained using the flowchart shown in Figure 22. The beam displacements are BDx and BDY. In Figure 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 element 523 in step S2. The order of steps S1 and S2 may be reversed. In step S3, the operator calculates the cutoff frequency fc by applying the delay time of the delay element 523 to the group delay time Td of the LPF 522.

[0054] In step S4, the operator determines whether the maximum value of the beam displacement is an optimal value close to the radius of the aperture 36a of the nozzle 36. The operator may verify whether the maximum value of the beam displacement is an optimal value on the actual laser processing machine 100, or they may verify whether the maximum value of the beam displacement is an optimal value through simulation. The optimal value is the distance from the center of the aperture 36a to a position a predetermined distance away from the edge of the aperture 36a in the direction 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 from the center of the aperture 36a is 0.8 mm.

[0055] By setting a distance of 0.2 mm from the edge of the aperture 36a, the laser beam will not strike the inner surface of the nozzle 36 around the aperture 36a when the laser beam is displaced. Furthermore, the laser beam is less likely to come too close to the edge of the aperture 36a, thus reducing the likelihood of thermal damage to the nozzle 36. Moreover, the amount of beam displacement can be made sufficiently large.

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

[0057] Steps S4 to S7 are repeated until the maximum value of the beam displacement in step S4 becomes the optimal value. If the maximum value of the beam displacement in step S4 is the optimal value, the operator finalizes the delay time of the delay unit 523 and the cutoff frequency fc of the LPF 522, thereby ending the procedure for determining the beam displacement.

[0058] As described above, the laser processing machine 100 sets a cutoff frequency fc that yields a beam displacement amount such that the laser beam displaced by the beam displacement mechanism fits 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. Therefore, the laser processing machine 100 moves the processing head 35 based on the main movement command signal MCS obtained by filtering the movement command signal CS, and displaces the laser beam while accurately fitting it within the aperture 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 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]

[0060] 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 the 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, By setting the order of the low-pass filter and the delay time of the delay element, the cutoff frequency of the low-pass filter is set to obtain a displacement amount of the laser beam such that the laser beam displaced by the beam displacement mechanism fits within the aperture. Laser processing machine.

2. The laser processing machine according to claim 1, wherein the control device sets the cutoff frequency of the low-pass filter that yields the maximum displacement of the laser beam, with the distance from the center of the aperture to a position a predetermined distance away from the end of the aperture in the direction toward the center being defined as the maximum displacement of the laser beam.

3. 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. By setting the order of the low-pass filter and the delay time of the delay element, the cutoff frequency of the low-pass filter is set to obtain a displacement amount of the laser beam such that the laser beam displaced by the beam displacement mechanism fits within the aperture. A control method for a laser processing machine.

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

Images