JP2010240689A - Laser beam machining method and laser beam machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance pulse laser machining performance by improving data processing efficiency in controlling the output peak value of the pulse laser beam. <P>SOLUTION: A laser beam machining apparatus comprises a fiber laser beam oscillator 10, a laser beam power source 12, a laser beam incident unit 14, a fiber transmission system 15, a laser beam emission unit 16, a control unit 18, a touch panel 20 and the like. The control unit 18 has a CPU (a microcomputer), an FPGA (a field programmable gate array), a digital-analog (D/A) converter, an analog-digital (A/D) converter and the like. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser processing technique for performing desired laser processing by irradiating a workpiece with a series of pulse laser beams, and more particularly to a laser processing method and a laser processing apparatus for controlling an output peak value of a series of pulse laser beams. .

  The most typical example of laser processing for repeatedly irradiating a workpiece with pulsed laser light is laser seam welding. In laser seam welding, a laser beam spot is relatively moved along the welding line while irradiating the workpiece with pulsed laser light at a constant repetition frequency, and the spot welding is gradually shifted and overlapped. Together, continuous joints are formed.

  Conventionally, in laser seam welding, a technique of varying the output (power) of pulsed laser light with a pulse period within a single welding schedule has been used. For example, in laser seam welding that joins the outer peripheral edge of a metal cap, when the end part is overlapped with the start end part by slightly overrunning the circumference of the annular seam welding line, the output peak value of the pulse laser beam is pulsed at the start end part. Up-slope control that gradually increases with the period is applied, and down-slope control that gradually decreases the output peak value of the pulsed laser light with the pulse period is performed at the terminal portion.

  A conventional laser processing apparatus uses a memory write / read function of a CPU (microcomputer) to control a waveform for an output peak value of a series of pulsed laser beams (for example, up-slope control and / or down as described above).・ Slope control). More specifically, when a user sets and inputs a desired output peak value characteristic (usually a polygonal waveform) for a series of pulse laser beams in one schedule through a man-machine interface such as a touch panel, the CPU inputs the setting. The output peak value is encoded for each pulse based on the output peak value characteristic, and the binary code is written in the memory as reference peak value data. Then, when performing laser seam welding, the CPU sequentially reads out the reference peak value data from the memory for each pulse, and multiplies the pulse basic output waveform separately generated or reproduced by the reference peak value for each pulse to generate a digital signal. A reference pulse waveform is generated.

  Thus, a reference pulse waveform is generated by the memory reading function and arithmetic function of the CPU, and the digital value of the reference pulse waveform is converted into an analog reference pulse waveform signal by the D / A converter and used as the feedback control signal of the pulse laser generator. Used. The pulse laser generator measures the output (power) of the oscillated pulse laser beam or measures the drive current for electro-optic conversion, and performs feedback control so that the measured value follows the reference pulse waveform.

JP2007-190566

  However, the conventional technique that relies exclusively on the CPU memory write / read function and arithmetic processing function for the variable control over the output peak value of the series of pulsed laser beams as described above places a heavy burden on CPU tasks and memory resources. This makes it difficult to improve the performance of the laser processing apparatus.

  Specifically, for example, in laser seam welding, in many cases, several thousand or more pulsed laser beams are continuously oscillated and output at a constant repetition frequency within one welding schedule. In that case, several thousand pieces of data (binary codes) are stored in the memory only for the reference peak value per welding schedule. Normally, since a plurality of welding schedules are set, the data amount of the reference peak value becomes enormous.

  Further, the memory write / read function and arithmetic processing function of the CPU are used not only for restoring the reference peak value, but also for generating or restoring the original pulse waveform that is the source of the output waveform of the pulse laser beam. For this reason, there is a problem in that the CPU is overloaded and the speed or degree of freedom of pulse waveform control is reduced.

  Furthermore, when a function for determining the quality of pulse waveform control is installed, waveform integration calculation processing for determining quality is also a task of the CPU, so that it is more difficult to improve pulse waveform control and repetition rate.

  As described above, conventionally, when variable control of the output peak value is performed for a series of pulsed laser beams, a large burden is imposed on the CPU task and memory resources, and it becomes difficult to improve the performance of laser processing using a pulsed laser. It was.

  The present invention has been made in view of the above-described problems of the prior art, and a laser processing method and a laser for improving the performance of pulse laser processing by improving data processing efficiency in output peak value control of a pulse laser. An object is to provide a processing apparatus.

  In order to achieve the above object, a laser processing method of the present invention is a laser processing method for performing desired laser processing by irradiating a workpiece with a series of pulsed laser beams over a certain period of time. A first step of setting one or a plurality of linear reference peak value characteristics connected along the time axis over the predetermined period for a reference peak value defining a peak value of the output of the pulse laser beam of For each of the reference peak value characteristics, at least a second step of generating at least initial value data, unit variation data, and operation processing frequency data as one-stage parameter data, and performing the laser processing A third step of generating an original pulse waveform that is a source of an output waveform of each of the pulse laser beams, and the original pulse when performing the laser processing. In parallel with the generation of the shape, along the time axis, the reference peak value characteristic is obtained by performing an arithmetic process of repeatedly adding the unit change amount to the initial value at a predetermined cycle based on the parameter data for each stage. And a fifth step of generating a reference pulse waveform having a desired peak value based on the original pulse waveform and the restored reference peak value characteristic for each of the pulse laser beams. And a sixth step of controlling the output waveform and output peak value of each pulse laser beam based on the reference pulse waveform.

  The laser processing apparatus of the present invention is a laser processing apparatus that performs desired laser processing by irradiating a workpiece with a series of pulsed laser beams over a certain period of time, and outputs the series of pulsed laser beams. A reference peak value characteristic setting unit that sets one or a plurality of linear reference peak value characteristics connected along the time axis over the predetermined period for the reference peak value that defines the peak value, and each of the reference For the peak value characteristics, at least when performing the laser processing, a stage parameter data generation unit that generates at least initial value data, unit variation data, and calculation processing frequency data as one stage parameter data, When performing the laser processing, an original pulse waveform generation unit that generates an original pulse waveform signal that is the source of the output waveform of each pulse laser beam, In parallel with the generation of the original pulse waveform signal, along the time axis, an arithmetic processing is performed to repeatedly add the unit change amount to the initial value at a predetermined cycle based on the parameter data for each stage. A reference peak value characteristic restoring unit for restoring a reference peak value characteristic, and a reference pulse waveform having a desired peak value based on the original pulse waveform signal and the restored reference peak value characteristic for each of the pulse laser beams A reference pulse waveform generation unit that generates a signal; and a pulse laser generation unit that controls an output waveform and an output peak value of each pulse laser beam based on the reference pulse waveform signal.

  In the present invention, for a repetitively pulsed laser beam used in a single welding schedule, for example, a broken line waveform of a reference peak value set and inputted through a man-machine interface such as a touch panel is directly sampled at a pulse period and encoded. Instead, the broken line waveform on the time axis is decomposed into a plurality of linear reference peak value characteristics that are its constituent elements, and predetermined attributes (initial value, unit change amount, A plurality of parameter data indicating the number of times of arithmetic processing) is generated, and information management of the parameter data for each stage is performed. When laser processing is performed with the above welding schedule, the parameters for each stage along the time axis are generated in parallel with the generation of the original pulse waveform that is the source of the output waveform of each pulse laser beam. Based on the data, the unit peak is repeatedly added to the initial value at a predetermined cycle to restore the reference peak value characteristics, and the reference pulse waveform is restored based on the original pulse waveform and the restored reference peak value characteristics. Based on this reference pulse waveform, the output waveform and output peak value of each pulse laser beam generated from the pulse laser generator are controlled.

  According to a preferred aspect of the present invention, in the second step (or stage parameter data generation unit), the first flag data indicating the cycle of the arithmetic processing with respect to the repetition cycle of the pulse laser beam is further stored in the stage. It is generated as one of the parameter data, and in the fourth step (or the reference peak value characteristic restoring unit), the above arithmetic processing is performed at the cycle indicated by the first flag. Alternatively, in the second step (or stage parameter data generation unit), the second flag data representing the calculation resolution is further generated as one of the stage parameter data, and the fourth step (or reference peak value) is generated. In the characteristic restoring unit), arithmetic processing is performed with the arithmetic resolution indicated by the second flag. By such a flag function of the calculation processing period or a flag function of the calculation resolution, the efficiency and accuracy of the calculation processing for restoring each reference peak value characteristic can be simultaneously optimized.

  According to a preferred aspect of the present invention, in the third step (or the original pulse waveform generator), the original pulse waveform is generated as a pulse signal having an arbitrary value between 0% and 200%, In the fifth step (or reference pulse waveform generation unit), a reference pulse waveform is generated by multiplying the value of the original pulse waveform by the value of the reference peak value characteristic. In this case, the original pulse waveforms generated in the third step (or the original pulse waveform generation unit) may all have the same waveform over a certain period, or the third step (or the original pulse waveform generation unit) The original pulse waveform generated in) may have each independent waveform. In the present invention, since the data necessary for restoring the reference peak value that defines the peak value of the output of a series of pulsed laser beams is substantially only parameter data for each stage, the task of the arithmetic processing unit and the memory resources Is greatly reduced, and the degree of freedom and accuracy of waveform control for the original pulse waveform can be improved.

  In a preferred aspect of the present invention, the reference peak value characteristic setting unit and the stage parameter data generation unit are configured by a CPU (microcomputer), and the reference peak value characteristic restoration unit is provided in an FPGA (field programmable gate array). Built. In this case, it is preferable that a parameter data memory for receiving and holding parameter data relating to the reference peak value characteristic from the CPU is further built in the FPGA, and the parameter of the stage is restored every time the reference peak value characteristic is restored. A buffer memory for transferring and holding data from the parameter data memory may be further constructed.

  According to the laser processing method or the laser processing apparatus of the present invention, the data processing efficiency in the output peak value control of the pulse laser can be improved and the performance improvement of the pulse laser processing can be achieved by the configuration and operation as described above. .

It is a block diagram which shows the structure of the laser processing apparatus (fiber laser welding machine) in one Embodiment of this invention. It is a block diagram which shows the structure of the control part in the laser processing apparatus of embodiment. It is a schematic plan view which shows irradiation of the pulse laser beam to the starting end part of a welding line in laser seam welding. It is a schematic plan view which shows irradiation of the pulse laser beam to the terminal part of the welding line in laser seam welding. It is a figure which shows the example of a setting of the main condition items of the welding schedule in the said laser seam welding. It is a figure which shows the attribute value of the reference | standard peak value characteristic of the 1st stage of the reference | standard peak value broken line waveform of FIG. It is a figure which shows the attribute value of the reference | standard peak value characteristic of a 2nd stage. It is a figure which shows the attribute value of the reference | standard peak value characteristic of a 3rd stage. It is a figure which shows the attribute value of the reference | standard peak value characteristic of a 4th stage. It is a figure which shows the attribute value of the reference | standard peak value characteristic of a 5th stage. It is a figure which shows the example of a format of the parameter data of 1 stage in embodiment. It is a block diagram which shows the circuit structure in FPGA in embodiment. It is a figure which shows the effect | action of the decompression | restoration of the reference peak value characteristic in a 1st stage, and the production | generation of a reference peak value waveform. It is a figure which shows the effect | action of the reconstruction | restoration of the reference peak value characteristic in the start part of a 2nd stage, and the production | generation of a reference peak value waveform. It is a figure which shows the effect | action of the decompression | restoration of the reference peak value characteristic in the termination | terminus part of a 2nd stage, and the production | generation of a reference peak value waveform. It is a figure which shows the effect | action of the decompression | restoration of the reference peak value characteristic in a 3rd stage, and the production | generation of a reference peak value waveform. It is a figure which shows the effect | action of the decompression | restoration of the reference peak value characteristic in the 4th and 5th stage, and the production | generation of a reference peak value waveform. It is a wave form diagram which shows one modification of the output peak value variable control in embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  In FIG. 1, the structure of the laser processing apparatus in one Embodiment of this invention is shown. This laser processing apparatus is configured as a fiber laser welding machine capable of performing a desired laser welding process by irradiating a workpiece W with a series of pulsed laser beams FB within a certain period of time. 12, a laser incident unit 14, a fiber transmission system 15, a laser emitting unit 16, a control unit 18, a touch panel 20, and the like.

  The fiber laser oscillator 10 includes an oscillation optical fiber (hereinafter referred to as “oscillation fiber”) 22, an electro-optical excitation unit 24 that irradiates one end surface of the oscillation fiber 22 with pumping excitation light MB, and an oscillation fiber. And a pair of optical resonator mirrors 26 and 28 that are optically opposed to each other via 22, and an electro-optic conversion unit that converts electrical energy supplied from the laser power source 12 into laser energy of laser light in the entire oscillator. Is configured.

The electro-optic excitation unit 24 includes a laser diode (LD) 30 as an excitation light source and a condensing optical lens 32. When laser processing using the pulsed laser beam FB is performed, the LD 30 is driven to emit light by supplying or injecting an LD drive current (or LD excitation current) _ID having a desired pulse waveform from the laser power source 12 to a predetermined wavelength. Pulse excitation light (LD light) MB is generated. The optical lens 32 condenses and enters the pulse excitation light MB from the LD 30 onto one end face of the oscillation fiber 22. The optical resonator mirror 26 disposed between the LD 30 and the optical lens 32 transmits the pulse excitation light MB incident from the LD 30 side, and transmits all the oscillation light incident from the oscillation fiber 22 side on the optical axis of the resonator. It is configured to reflect.

To measure the LD drive current I _D supplied to the laser power source 12 from the LD 30, the current sensor 25 and the LD current measurement circuit 27 are provided. The current sensor 25 is composed of, for example, a Hall element, and detects the LD drive current _ID without contact. LD current measurement circuit 27 inputs the output signal of the current sensor 25 a current measuring value of the LD drive current I _D (eg, current effective value) is calculated M _ID. The current measurement value M _ID obtained by the LD current measurement circuit 27 is supplied to the laser power source 12 as a feedback signal and to the control unit 18 as a monitor signal.

  Although not shown, the oscillation fiber 22 has a core doped with, for example, rare earth element ions as a light emitting element, and a clad surrounding the core coaxially. The core is used as an active medium, and the clad is used as the propagation of excitation light. The light path. The pulse excitation light MB incident on one end face of the oscillation fiber 22 as described above propagates in the oscillation fiber 22 in the axial direction while being confined by total reflection at the cladding outer peripheral interface. Across the core, photoexcites rare earth ions in the core. In this way, an oscillating light beam having a predetermined wavelength is emitted in the axial direction from both end faces of the core, and this oscillating light beam travels back and forth between the optical resonator mirrors 26 and 28 and is resonantly amplified. The pulse laser beam FB having the predetermined wavelength is extracted from the optical resonator mirror 28.

  In the optical resonator, the optical lenses 32 and 34 collimate the oscillating light beam emitted from the end face of the oscillating fiber 22 into parallel light and pass it to the optical resonator mirrors 26 and 28. The oscillation light beam reflected and returned by 28 is condensed on the end face of the oscillation fiber 22. The pulse excitation light MB that has passed through the oscillation fiber 22 passes through the optical lens 34 and the optical resonator mirror 28, and is then folded back toward the side laser absorber 38 by the folding mirror 36. The pulsed laser beam FB output from the optical resonator mirror 28 passes straight through the folding mirror 36 and then passes through the beam splitter 40 before entering the laser incident portion 14.

The beam splitter 40 reflects a small portion (for example, 1%) of the incident pulse laser beam FB in a predetermined direction, that is, the power sensor photosensor (PD) 42 side, and transmits the remaining most (99%) straight. Let A condensing lens 44 that condenses the reflected light from the beam splitter 40 or the monitor light R _FB is disposed in front of the photo sensor (PD) 42.

The photosensor (PD) 42 photoelectrically converts the monitor light R _FB from the beam splitter 40 and outputs an electrical signal (laser output measurement signal) representing the laser output (power) of the pulsed laser light FB. The laser output measurement circuit 45 obtains the laser output measurement value M _FB of the pulsed laser light FB by analog signal processing based on the output signal of the photosensor 42. The laser output measurement value M _FB obtained by the laser output measurement circuit 45 is supplied to the laser power source 12 as a feedback signal and to the control unit 18 as a monitor signal.

  The pulsed laser beam FB that passes straight through the beam splitter 40 and enters the laser incident portion 14 is first folded in a predetermined direction by the vent mirror 46 and then condensed by the condenser lens 50 in the incident unit 48 and transmitted through the fiber. The light is incident on one end face of a transmission optical fiber (hereinafter referred to as “transmission fiber”) 52 of the system 15. The transmission optical fiber 52 is made of, for example, an SI (step index) fiber, and transmits the pulsed laser light FB incident in the incident unit 48 to the emission unit 54 of the laser emission unit 16. The emission unit 54 includes a collimator lens 56 that collimates the pulse laser beam FB emitted from the end face of the transmission fiber 52 into parallel light, and the parallel pulse laser beam FB at a predetermined focal position, that is, a workpiece on the processing stage 60. And a condensing lens 58 for condensing light on the WP.

  In the workpiece WP, the workpiece material is melted by laser energy on the welding point or welding line where the pulsed laser beam FB is focused and irradiated, and solidifies after the pulse irradiation to form a nugget. When the workpiece WP is repeatedly irradiated with a large number (a series) of pulsed laser beams FB at a constant cycle in a single welding schedule, the operation of each part described above is repeated at the constant cycle (repetition frequency).

  The processing stage 60 has, for example, an XY table mechanism, and when laser seam welding is performed, the control unit 18 so that the beam spot of the pulsed laser beam FB moves along the welding line on the workpiece WP. The workpiece WP is configured to move in the XY directions under the above control.

  The fiber laser oscillator 10 oscillates and outputs pulsed laser light FB with a narrow beam diameter and a small beam divergence angle because the oscillation fiber 22 uses an elongated core having a diameter of about 10 μm and a length of several meters as an active medium. . In addition, since the excitation light MB incident on one end face of the oscillation fiber 22 propagates through the long optical path of several meters in the oscillation fiber 22 and exhausts the excitation energy many times, the oscillation efficiency is very high. The pulse laser beam FB can be generated. The fiber laser oscillator 10 has a very stable beam mode because the core of the oscillation fiber 22 does not cause a thermal lens effect.

  As will be described later, this fiber laser welder has desired output (power) peak values for a series of pulsed laser beams FB within a single welding schedule for each of a plurality of sections. In addition, the burden on the CPU and memory in the control unit 18 regarding the output peak value control of the pulse laser is greatly reduced as compared with the prior art. These functions (pulse waveform control, pass / fail judgment, etc.) can be used with sufficient margin to meet the strict requirements for precision welding.

  FIG. 2 shows a specific configuration example of the control unit 18 in this embodiment. As illustrated, the control unit 18 includes a CPU (microcomputer) 64, an FPGA (field programmable gate array) 66, a digital-analog (D / A) converter 68, an analog-digital (A) in terms of hardware. / D) converters 70 and 72 and a connecting device 74 are provided.

  The CPU 64 includes a central processing unit, a program memory, a data memory, an interface circuit, and the like, and controls the operation of the entire apparatus or each unit according to various programs (software) stored in the program memory. In particular, regarding the output peak value control in the laser processing using the pulse laser beam FB repeatedly in one welding schedule, the CPU 64 can be used by the user (worker, maintenance staff, etc.) via the display unit 20a and the input unit 20b of the touch panel 20. Enter the desired reference peak value characteristics.

Here, as shown in FIG. 3, laser processing for joining the outer peripheral edge of a circular metal cap 76 to a base body (not shown) by laser seam welding is taken as an example. In this laser seam welding, a beam spot BS _FB of a series of pulsed laser beams FB is moved little by little along the annular welding line 78 set at the outer peripheral edge of the metal cap 76 while being overlapped. In this case, in order to ensure the joining finish or joining strength of the starting end portion or the terminal end portion, as shown in FIG. 4, the seam welded portion is slightly overrun by one round to overlap the terminal end portion with the starting end portion. .

  For laser seam welding (FIGS. 3 and 4) as described above, the user inputs desired characteristics or values for each condition item that can be set in the welding schedule through the touch panel 20.

More specifically, the number (n) of the repetitive pulse laser beams FB _{1 to} FB _n used for the processing of the welding schedule, the repetitive cycle, and the characteristics of the original pulse waveform fb that is the basis of the output waveform of each pulse laser light FB ( Waveform shape, peak value, pulse width) etc. are set and input. In the setting input example of FIG. 5, 5000 repetitive pulse laser beams FB _{1 to} FB ₅₀₀₀ are set within the machining time selected in the welding schedule, and 5000 corresponding to the pulse laser beams FB _{1 to} FB ₅₀₀₀ respectively. The same waveform shape (rectangle), peak value, and pulse width are set for each of the original pulse waveforms fb _{1 to} fb ₅₀₀₀ . Here, the peak value of the original pulse waveform fb _i is represented by a relative value having an arbitrary value of 0 to 200%.

Further, in this embodiment, for the reference peak values that define the peak values of the outputs of the pulse laser beams FB _{1 to} FB _n , for example, linear reference peak value characteristics A of a plurality of (for example, five) stages connected serially. ₁ , A ₂ , A ₃ , A ₄ , A ₅ are set and input in the form of a broken line waveform and / or data table.

The reference peak value characteristic A ₁ of the first stage is for the _{1st to 99th} pulse laser beams FB _{1 to} FB ₉₉ , and is an up-slope that rises linearly with a considerably large gradient as the number of pulse repetitions increases. A waveform is shown, and the starting value (initial value) is 10 W.

Reference peak value characteristic A ₂ of the second stage is for the pulsed laser beam FB ₁₀₀ ~FB ₂₉₉₉ of 100-2999 shot eyes, down to decrease to a very linear with small slope in accordance with the number of repetitions of the pulse is increased The waveform of the slope is shown, and the starting value (initial value) is 500 W.

The third stage reference peak value characteristic A ₃ is for the _{3000 to} 3999th pulse laser beams FB _{3000 to} FB ₃₉₉₉ , and shows a flat waveform that keeps a constant value regardless of the number of pulse repetitions. The starting value (initial value) is 400W.

The reference peak value characteristic A ₄ of the fourth stage is for the _{4000 to} 4999th pulse laser beams FB _{4000 to} FB ₄₉₉₉ , and is a down / linear decrease with a relatively small gradient as the number of pulse repetitions increases. The waveform of the slope is shown, and the starting value (initial value) is 400W.

Reference peak value characteristic A ₅ of the fifth stage (final) are those against only pulsed laser light FB ₅₀₀₀ 5000 shots th (last), the value of the start (and end) is 10 W.

In the control unit 18, the CPU 64 does not sample and encode the broken line waveform of the reference peak value set and inputted through the touch panel 20 as it is in the pulse period as in the prior art, but the broken line waveform on the time axis. The waveform is decomposed into a plurality of (five) linear reference peak value characteristics A ₁ , A ₂ , A ₃ , A ₄ , and A ₅ as its constituent elements, and as shown in FIGS. For each of the reference peak value characteristics A _{1 to} A _5, predetermined parameter data indicating the attribute is generated.

In this embodiment, with respect to the reference peak value characteristics A _{1 to} A ₅ of each stage, (1) “initial value” data representing the start value, and (2) “unit change” representing the amount of change per calculation process. Amount ”data, (3)“ Number of times of operation ”data indicating the number of times of calculation processing (time-axis resolution) repeatedly adding the amount of change to the initial value, and (4) Indicates the cycle and resolution of the calculation for the pulse period. Four types of parameter data, “calculation cycle flag / resolution flag” data, are generated by the CPU 64.

  In generating the parameter data, the initial value (W) and the unit change amount (W) are converted into a digital value having a predetermined bit width corresponding to the voltage (V). In this embodiment, the minimum value of the initial value (W) that can be set is 0 (W) and the maximum value is 625 (W), which is converted into a 13-bit (0 to 4095) digital value.

  For the “unit change amount”, 15-bit (0 to 30000) data representing an absolute value and 1-bit data representing a sign (+/−) are used. Here, the position of the decimal point of the “unit change amount” data is indicated by a 2-bit “resolution flag”. That is, when the arithmetic processing is performed assuming that the digital value of the “unit change amount” is 0 to 3000.0, the normal resolution mode is set and (0, 0) is set in the “resolution flag”. When the arithmetic processing is performed assuming that the digital value of “unit change amount” is 0 to 300.00, the high resolution mode is set, and (0, 1) is set in the “resolution flag”. When the arithmetic processing is performed assuming that the digital value of “unit change amount” is 0 to 30.000, the mode is set to the super-high resolution, and (1,0) is set in the “resolution flag”.

  In the example shown in the figure, the “calculation count” is made to coincide with the pulse repetition count, and the “calculation cycle” is made to coincide with the pulse cycle, but this is an example, and each can be set to an independent value.

The CPU 64 manages the above four types of parameter data for one stage generated for each of the reference peak value characteristics A _{1 to} A ₅ in a set as shown in FIG. 11, for example.

  FIG. 12 shows an example of the configuration of various circuits built in the FPGA 66 in this embodiment. As illustrated, the FPGA 66 includes a data memory 80, a control circuit 82, a stage parameter data buffer memory 84, an original pulse waveform generation circuit 86, a reference peak value calculation circuit 88, a set reference peak value register 90, and a buffer register 92. , Reference pulse waveform generation circuit 94, cycle counter 96, reference pulse waveform output circuit 98, reference pulse waveform integration circuit 100, current monitor waveform buffer memory 102, laser output monitor waveform buffer memory 104, current monitor waveform integration circuit 106, laser output A monitor waveform integration circuit 108, a comparison determination circuit 110, and the like are built in. A clock necessary for the operation of these circuits 80 to 110 is supplied from an external clock circuit 112.

  Prior to the start of the laser welding process, data necessary for generating a feedback control signal (reference pulse waveform signal CS) to be given to the laser power source 12 in the welding schedule is written in the data memory 80 by the CPU 64. Among them, parameter data (FIG. 11) used for restoring the reference peak value characteristics and data used for generating or reproducing the original pulse waveform fb are particularly important.

  The control circuit 82 receives a required control signal and various data related to the control from the CPU 64 and controls each part in the FPGA 66.

  The stage parameter data buffer memory 84 fetches and holds the parameter data (FIG. 11) from the data memory 80 for each stage when sequentially executing the restoration processing of each reference peak value characteristic.

The original pulse waveform generation circuit 86 repeatedly generates the original pulse waveform fb set in the welding schedule with a pulse period. In the example of FIG. 5, the original pulse waveforms fb ₁ , fb ₂ , fb ₃ ,... Having the same waveform (rectangular wave) are set on the touch panel 20 over the entire period of the welding schedule. The original pulse waveform generation circuit 86 generates original pulse waveform data obtained by sampling the original pulse waveform fb at a constant period, or original pulse waveform data obtained by compressing or decomposing the original pulse waveform fb with a predetermined algorithm. Are received from the CPU 80 via the data memory 80, and digital signals of the original pulse waveforms fb ₁ , fb ₂ , fb ₃ ,... Are generated based on the original pulse waveform data.

The reference peak value calculation circuit 88 performs a predetermined calculation (calculation that adds the unit change amount to the initial value) based on the parameter data (FIG. 11) of each stage along the time axis under the control of the control circuit 82. Are repeatedly performed at a constant period (period designated by the “calculation period” flag), and the respective reference peak value characteristics (A _{1 to} A ₅ ) are sequentially restored. For this arithmetic processing, the parameter data of each stage is transferred from the data memory 80 to the stage parameter data buffer memory 86 by overwriting.

The set reference peak value register 90 is used when a mode in which the output peak values of a series of pulse laser beams FB _{1 to} FB _n are all set to a constant value is selected in the welding schedule, and a representative value (set value) of the reference peak value is set. Value). For example, in the setting example of FIG. 5, when the user selects 500 W as the representative value (setting value), the digital value (“3276”) of the voltage (V) corresponding to 500 W is transmitted from the CPU 64 via the data memory 80. The setting reference peak value register 90 is loaded.

The buffer register 92 holds the values a _i of the respective reference peak value characteristics (A _{1 to} A ₅ ) obtained from the reference peak value calculation circuit 88 at the above-mentioned fixed period by sequentially overwriting, and gives them to the reference pulse generation circuit 94. When the representative value (set value) held in the set reference peak value register 90 is used as the reference peak value, the representative value (set value) is given to the reference pulse generation circuit 94 via the buffer register 92. It is done.

The reference pulse waveform generation circuit 94 includes a multiplication circuit. The reference pulse value characteristic value a _i from the reference peak value calculation circuit 88 is added to the original pulse waveform signal fb _i output from the original pulse waveform generation circuit 86 at the pulse repetition frequency. To generate a reference pulse waveform signal CS _i . The reference pulse waveform signal CS _i is a digital signal that defines or indicates the output (waveform and peak value) of the pulse laser beam FB _i .

The reference pulse waveform output circuit 98 latches each reference pulse waveform signal CS _i generated by the reference pulse waveform calculation circuit 94 and outputs it as a feedback control signal for the laser power source 12 at a predetermined timing.

  The cycle counter 96 counts a predetermined pulse generated at the end of each calculation process from the reference pulse waveform generation circuit 94 (or the reference peak value calculation circuit 88). When the count value reaches a set value, the cycle counter 96 calculates the corresponding stage. A signal K is sent to the control circuit 82 to notify that all processing has been completed.

The reference pulse waveform integration circuit 100 takes in the instantaneous value (digital value) of each reference pulse waveform signal CS _i output from the reference pulse waveform output circuit 98 and cumulatively adds it to obtain an integrated value of the reference pulse waveform CS _i .

The current monitor waveform buffer memory 102 latches the LD drive current measurement value M _ID sent from the LD current measurement circuit 27 via the connection circuit 74 and the A / D converter 70 (FIG. 2). The current monitor waveform integration circuit 106 takes in the LD drive current measurement value M _ID from the current monitor waveform buffer memory 102 at regular intervals, and cumulatively adds it to obtain the integrated value of the LD drive current monitor waveform.

The laser output monitor waveform buffer memory 104 latches the laser output measurement value M _FB sent from the laser output measurement circuit 45 via the connection circuit 74 and the A / D converter 72 (FIG. 2). The laser output monitor waveform integration circuit 108 takes in the laser output measurement value _MFB from the laser output monitor waveform buffer memory 104 at regular intervals, and accumulates and calculates the integrated value of the laser output monitor waveform.

  The comparison / determination circuit 110 is configured such that the integration value of the reference waveform obtained by the reference pulse waveform integration circuit 100 and the LD drive current monitor obtained by the current monitor waveform integration circuit 106 each time one monitoring period ends. The integrated value of the waveform or the integrated value of the laser output monitor waveform obtained by the laser output monitor waveform integrating circuit 108 is compared to obtain a difference (error), and whether the error is within a predetermined allowable range. Judgment of whether or not (good or bad judgment) is performed. And when the determination result of a defect comes out, this is transmitted to CPU64.

  Note that, when the result of the failure determination is sent to the CPU 64, the monitor waveform data stored in the buffer memories 102 and 104 can also be sent to the CPU 64.

Although not shown, the laser power source 12 (FIG. 1) includes a DC power source, an LD drive circuit, a comparator, a feedback signal selection circuit, and the like. The DC power source is composed of, for example, an inverter circuit or a switching regulator circuit, and outputs a constant LD drive voltage. The LD drive circuit includes a V-I conversion circuit that generates an LD drive current _ID from the LD drive voltage, and is sent from the reference waveform output circuit 90 of the FPGA 66 through the D / A converter 68 and the connection circuit 74. The LD drive current _ID is varied so as to follow the analog reference pulse waveform signal CS. The comparator inputs the analog reference pulse waveform signal CS from the FPGA 66 as a command signal, and also inputs the LD drive current measurement value M _ID or the laser output measurement value M _FB as a feedback signal from the feedback signal selection circuit, and both input signals An error signal representing the difference is output. The LD drive circuit varies the LD drive current _ID in a direction to make the error signal zero. Feedback signal selection circuit, under the control of the CPU 64, selects the LD drive current measurement value M _ID when applying feedback control for the LD drive current I _D, the feedback control for the output of the fiber laser beam FB When applying, the laser output measurement value _MFB is selected.

  FIGS. 13 to 17 are waveform diagrams showing main actions (particularly, restoration of the reference peak value and generation of the reference pulse waveform) in the FPGA 66 when laser seam welding (FIGS. 3 and 4) according to the setting example of FIG. 5 is performed. It shows with.

When the laser seam welding process is started, the original pulse waveform generation circuit 86 has rectangular original pulse waveforms fb ₁ and fb ₂ having the same waveform and peak value based on the original pulse waveform data stored in the data memory 80. , Fb ₃ ,... Are sequentially generated with a constant period ΔT _B. In this example, it is assumed that the top peak value of the original pulse waveform fb ₁ is set to 100%.

On the other hand, the reference peak value calculation circuit 88 is based on the parameter data (FIG. 11) related to the reference peak value characteristic A ₁ of the first stage held in the stage parameter data buffer memory 86, and the initial value a ₁ ( 66) is repeatedly added to the unit variation ΔPeak (32.424), and the values a ₁ and a of the reference peak value characteristic A ₁ corresponding to the original pulse waveforms fb ₁ , fb ₂ , fb ₃ ,. ₂ , a ₃ ,... Are sequentially output at a constant period ΔT _A1 . Here, for example, a ₂ is output as a ₂ = 98 by rounding down the decimal point below a ₁ (66) + ΔPeak (32.424) ≈98.42. a ₃ is the same or later. The corresponding original pulse waveforms fb _i and a _i are generated in synchronization with each other, but a _i is output at a timing earlier than fb _i .

The reference pulse waveform generation circuit 94 multiplies each original pulse waveform fb _i (top peak value 100%) generated by the original pulse waveform generation circuit 86 by the value a _i of the reference peak value characteristic A ₁ to generate a reference pulse waveform. A digital signal representing CS _i is generated.

As shown in FIG. 13, in response to the fact that the reference peak value characteristic A _{1 of} the first stage is an up-slope characteristic that rises linearly with a large gradient as the number of pulse repetitions increases, the reference pulse waveform CS _i The peak value (and hence the output peak value of the pulsed laser beam FB _i ) also increases linearly with the same or proportional gradient as the reference peak value characteristic A ₁ .

The first stage ends with the 99th pulse and shifts from the 100th to the second stage. As shown in FIGS. 14 and 15, in the second stage, the original pulse waveform generation circuit 86 has the same period as the original pulse waveforms fb ₁₀₀ , fb ₁₀₁ , fb ₁₀₂ ,. Are sequentially generated with a constant period ΔT _B. However, in the reference peak value calculation circuit 88, the stage parameter data (FIG. 11) is switched, and the values a ₁₀₀ , a ₁₀₁ , a ₁₀₂ ,... Of the reference peak value characteristics A ₂ are set at a constant period ΔT _A2 . Output sequentially. Here, for example, a ₁₀₁ is output as a ₁₀₁ = 3275 by rounding down the decimal point of a ₁₀₀ (3276) + ΔPeak (−0.2258) ≈3275.774. Subsequent a ₁₀₂ ,... Are obtained by the same calculation.

As shown in FIGS. 14A and 14B, in response to a characteristic of the down-slope of the reference peak value characteristic A ₂ of the second stage is reduced to a very linear small gradient in accordance with the pulse number of repetitions increases, The peak value of the reference pulse waveform CS _i (and hence the output peak value of the pulse laser beam FB _i ) also decreases linearly with a gradient that is the same as or proportional to the reference peak value characteristic A ₂ .

The second stage ends with the 2999th pulse, and shifts from the 3000th stage to the third stage. As shown in FIG. 15, even in the third stage, the original pulse waveform generation circuit 86 still has the same original pulse waveforms fb ₃₀₀₀ , fb ₃₀₀₁ , fb ₃₀₀₂ ,... With the same period as in the first and second stages. The digital signals are sequentially generated with a constant period ΔT _B. However, in the case of the reference peak value calculation circuit 88, the stage parameter data (FIG. 11) is switched, and the values a ₃₀₀₀ , a ₃₀₀₁ , a ₃₀₀₂ ,... Of the third stage reference peak value characteristic A ₃ are constant. The signals are sequentially output with a period ΔT _A3 . Here, for example, a ₃₀₀₁ is output as a ₃₀₀₀ (2621) + ΔPeak (0) = 2621. Subsequent values a ₃₀₀₁ , a ₃₀₀₂ ,... Are also output with the same value (2621).

As shown in FIG. 15, in response to the fact that the reference peak value characteristic A _{3 of} the third stage is a flat characteristic that keeps a constant value regardless of the number of pulse repetitions, the peak value of the reference pulse waveform CS _i ( Therefore, the output peak value of the pulse laser beam FB _i also keeps a constant value in a flat manner as in the reference peak value characteristic A ₃ .

  As another example, when the reference peak value characteristic is flat as described above, the number of “arithmetic processing” in the stage parameter data is extremely reduced or the “arithmetic cycle” is extremely increased. Is also possible.

The third stage ends with the 3999th pulse, and shifts from the 4000th to the fourth stage. As shown in FIG. 16, in the fourth stage, the original pulse waveform generation circuit 86 still has the same original pulse waveforms fb ₄₀₀₀ , fb ₄₀₀₁ , fb ₄₀₀₂ ,... With the same period as in the first to third stages. The digital signals are sequentially generated with a constant period ΔT _B. However, towards the reference peak value calculating circuit 88, the stage parameter data (FIG. 11) is switched, the value a ₄₀₀₀ reference peak value characteristic A ₄ of the fourth stage, a _4001, a _4002, a ... constant The signals are sequentially output with a period ΔT _A4 . Here, for example, a ₄₀₀₁ is output as a ₄₀₀₁ = 2618 by rounding down the decimal point of a ₄₀₀₀ (2621) + ΔPeak (−2.555) ≈2618.445. Subsequent a ₄₀₀₂ ,... _Are obtained by the same calculation.

As shown in FIG. 16, in response to the fact that the reference peak value characteristic A _{4 of} the fourth stage is a down slope characteristic that linearly decreases with a relatively small gradient as the number of pulse repetitions increases, the reference pulse waveform The peak value of CS _i (and therefore the output peak value of the pulsed laser beam FB _i ) also decreases linearly with the same or proportional gradient as the reference peak value characteristic A ₄ .

The fourth stage ends with the 4999th pulse, and the last 5000th pulse is the fifth stage. In this case, the reference peak value calculation circuit 88 need only output the initial value a ₅₀₀₀ of the fifth stage.

The setting example of FIG. 5 described above is merely an example for explaining the operation of the embodiment, and it is possible to set an arbitrary number and an arbitrary aspect of reference peak value characteristics in one welding schedule. . Various modifications can be made to other setting items. For example, as shown in FIG. 17, the waveforms (waveform shape, peak value, pulse width, etc.) of the original pulse waveforms fb _i , fb _{i + 1} , fb _{i + 2} ,. It is also possible to vary.

  As described above, in the fiber laser welding machine of this embodiment, when variable control of the output peak value is performed for a series of pulsed laser beams included in one welding schedule, one united along the time axis. Alternatively, a plurality of linear reference peak value characteristics are set, and for each reference peak value characteristic, initial value data, unit variation data, calculation processing count data, calculation processing count, and calculation resolution flag data are set. Generated as one-stage parameter data. When laser processing is performed, the initial pulse waveform is generated based on the parameter data for each stage along the time axis in parallel with the generation of the original pulse waveform that is the source of the output waveform of each pulse laser beam. A reference peak value characteristic is restored by performing an arithmetic process of repeatedly adding a unit change amount to a value at a predetermined cycle, and a reference pulse waveform is generated based on the original pulse waveform and the restored reference peak value characteristic. Based on the pulse waveform, the output waveform and output peak value of each pulse laser beam generated from the pulse laser generator are controlled.

  According to such a configuration or method, the data necessary for restoring the reference peak value that defines the peak value of the output of a series of pulsed laser beams can be substantially only parameter data for each stage. The load on the FPGA 66 is greatly reduced, and the data processing capability of the CPU 64 and the FPGA 66 can be used for other functions (pulse waveform control, pass / fail judgment, etc.), thereby improving the performance of the pulse laser processing and precision welding processing. Strict requirements can be met with sufficient margin.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above does not limit this invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and technical scope of the present invention.

  For example, in the output peak value control of the embodiment, it is also possible to fix the calculation cycle and resolution to one type of scale. In this case, the flag data of “calculation cycle” or “resolution” is set in the stage parameter data. It can be omitted.

  Various modifications can be made in each part of the fiber laser welder. For example, the fiber laser oscillator 10 can be replaced with a YAG laser oscillator or the like. The laser processing method and laser processing apparatus of the present invention are not limited to laser seam welding, but can be applied to other types of laser welding, and can also be applied to other laser processing such as drilling, cutting, and marking. is there.

DESCRIPTION OF SYMBOLS 10 Fiber laser oscillator 12 Laser power supply 18 Control part 20 Touch panel 22 Optical fiber for oscillation 24 Electro-optical excitation part 64 CPU
66 FPGA (Feed Programmable Gate Array)
80 data memory 84 stage parameter data buffer memory 86 original pulse waveform generation circuit 88 reference peak value calculation circuit 94 reference pulse waveform generation circuit

Claims (15)

A laser processing method for performing desired laser processing by irradiating a workpiece with a series of pulsed laser beams over a certain period of time,
For a reference peak value that defines a peak value of the output of the series of pulsed laser beams, a first reference characteristic that sets one or more linear reference peak values connected along the time axis over the predetermined period is set. Steps,
For each of the reference peak value characteristics, at least a second step of generating, as one-stage parameter data, at least initial value data, unit variation data, and arithmetic processing frequency data;
A third step of generating an original pulse waveform that is a source of an output waveform of each of the pulsed laser beams when performing the laser processing;
When performing the laser processing, in parallel with the generation of the original pulse waveform, along the time axis, the unit change amount is repeated at a predetermined cycle on the initial value based on the parameter data for each stage. A fourth step of restoring the reference peak value characteristic by performing arithmetic processing to be added;
A fifth step of generating a reference pulse waveform having a desired peak value based on the original pulse waveform and the restored reference peak value characteristic for each of the pulse laser beams;
And a sixth step of controlling an output waveform and an output peak value of each pulsed laser beam based on the reference pulse waveform. In the second step, further, data of a first flag representing a cycle of the arithmetic processing with respect to a repetition cycle of the pulse laser beam is generated as one of stage parameter data,
In the fourth step, the calculation process is performed in a cycle indicated by the first flag.
The laser processing method according to claim 1. In the second step, the second flag data representing the calculation resolution is further generated as one of the stage parameter data,
In the fourth step, the calculation processing is performed with the calculation resolution indicated by the second flag.
The laser processing method according to claim 1 or 2. In the third step, the original pulse waveform is generated as a pulse signal having an arbitrary value continuous between 0% and 200%,
In the fifth step, the reference pulse waveform is generated by multiplying the value of the original pulse waveform by the value of the reference peak value characteristic,
The laser processing method as described in any one of Claims 1-3.   The laser processing method according to claim 4, wherein all of the original pulse waveforms generated in the third step have the same waveform over the predetermined period.   The laser processing method according to claim 4, wherein the original pulse waveform generated in the third step has an independent waveform. A laser processing apparatus for performing desired laser processing by irradiating a workpiece with a series of pulsed laser beams over a certain period of time,
A reference peak value that sets one or a plurality of linear reference peak value characteristics that are connected along the time axis over the certain period with respect to a reference peak value that defines a peak value of the output of the series of pulsed laser beams. A characteristic setting section;
For each of the reference peak value characteristics, at least a stage parameter data generating unit that generates at least initial value data, unit change amount data, and operation processing frequency data as one stage parameter data;
When performing the laser processing, an original pulse waveform generation unit that generates an original pulse waveform signal that is a source of an output waveform of each of the pulse laser beams,
When performing the laser processing, in parallel with the generation of the original pulse waveform signal, along the time axis, the unit change amount is set to the initial value based on the parameter data for each stage at a predetermined cycle. A reference peak value characteristic restoring unit for performing the arithmetic processing to repeatedly add and restoring the reference peak value characteristic;
A reference pulse waveform generator for generating a reference pulse waveform signal having a desired peak value based on the original pulse waveform signal and the restored reference peak value characteristic for each of the pulse laser beams;
And a pulse laser generator that controls an output waveform and an output peak value of each pulsed laser beam based on the reference pulse waveform signal. The stage parameter data generation unit further generates, as one of the stage parameter data, data of a first flag that represents a cycle of the arithmetic processing with respect to a repetition cycle of the pulse laser beam,
The reference peak value characteristic restoration unit performs the calculation process at a cycle indicated by the first flag.
The laser processing apparatus according to claim 7. The stage parameter data generation unit further generates second flag data representing calculation resolution as one of stage parameter data,
The reference peak value characteristic restoration unit performs the calculation process with the calculation resolution indicated by the second flag.
The laser processing apparatus according to claim 7 or 8. The original pulse waveform generation unit generates the original pulse waveform signal as a pulse signal having an arbitrary value continuous between 0% and 200%,
The reference pulse waveform generation unit generates the reference pulse waveform signal by multiplying the value of the original pulse waveform signal by the value of the reference peak value characteristic;
The laser processing apparatus as described in any one of Claims 7-9.   The laser processing apparatus according to any one of claims 7 to 10, wherein the original pulse waveform generation unit generates the original pulse waveform signal having the same waveform over the predetermined period.   The laser processing apparatus according to any one of claims 7 to 10, wherein the original pulse waveform generation unit generates the original pulse waveform signal having an independent waveform. The reference peak value characteristic setting unit and the stage parameter data generation unit are constituted by a CPU (microcomputer),
The reference peak value characteristic restoration unit is constructed in an FPGA (Field Programmable Gate Array),
The laser processing apparatus as described in any one of Claims 7-12.   The laser processing apparatus according to claim 13, wherein a parameter data memory that receives and holds parameter data related to the reference peak value characteristic from the CPU is further built in the FPGA.   The laser processing according to claim 14, wherein a buffer memory is further built in the FPGA to store the parameter data of the stage from the parameter data memory when restoring each of the reference peak value characteristics. apparatus.

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