JP6851862B2 - Laser processing machine and its control method - Google Patents

Description

The present invention relates to a laser processing machine that processes an object to be processed by using a laser pulse transmitted through a condenser lens, and a control method thereof.

In the field of material processing, laser processing machines have been widely used in recent years. In material processing using a laser processing machine, laser light generated by a laser device such as a fiber laser is condensed using a condensing lens and irradiated to an object to be processed. In order to realize efficient and highly accurate processing using such a laser processing machine, from the condenser lens to the processing object so as to minimize the spot size of the laser beam on the surface of the processing object. Control that optimizes the distance is important.

Examples of documents that disclose such a control method include Patent Document 1. Patent Document 1 discloses a control method for optimizing the distance from the condenser lens to the object to be processed based on the time integral value of the intensity of the reflected pulse generated by the reflection of the laser pulse by the object to be processed. ing. In the control method described in Patent Document 1, the intensity of the reflected pulse is measured while changing the distance from the condenser lens to the object to be processed, and the distance at which the time integral value is the minimum is set as the optimum distance.

Special Table 2013-535340 Gazette (published on September 12, 2013)

The control method described in Patent Document 1 is based on the premise that the tendency that "the smaller the spot size of the laser pulse on the surface of the object to be processed, the smaller the time integral value of the intensity of the reflected pulse" is established. However, such a tendency does not hold depending on the material or surface condition of the object to be processed, that is, the distance from the condenser lens to the object to be processed is brought close to the optimum value by using the control method described in Patent Document 1. The inventor of the present application has found that this is not possible.

The present invention has been made in view of the above problems, and an object of the present invention is to make the distance from the condenser lens to the object to be processed close to the optimum value regardless of the material and surface condition of the object to be processed. The purpose is to realize a control method for a laser processing machine.

In order to achieve the above object, the control method according to the present invention is a control method for controlling a laser processing machine that processes an object to be processed by using a laser pulse transmitted through a condenser lens. Alternatively, a moving step of changing the distance from the condenser lens to the processing object by moving the processing object, irradiating the processing object with the laser pulse, and irradiating the processing object with the laser pulse are applied to the processing target. An irradiation detection step for detecting a reflected pulse generated by the reflection of an object, a time waveform of the reflected pulse detected in the irradiation detection step carried out after the moving step, and a time waveform of the reflected pulse carried out before the moving step. By comparing the time waveform of the reflected pulse detected in the irradiation detection step carried out last time, whether or not the distance from the condenser lens to the object to be processed approaches the optimum value by the moving step. It is characterized in that it includes a determination step of determining whether or not.

According to the above configuration, the distance from the condenser lens to the object to be processed can be brought close to the optimum value based on the determination result in the above determination step, regardless of the material and surface condition of the object to be processed.

In the control method according to the present invention, the time from the end of the irradiation of the laser pulse in the irradiation detection step carried out last time to the start of the irradiation of the laser pulse in the irradiation detection step carried out this time is the previous time. It is preferable that it is longer than the time required for the surface of the processed object melted in the irradiation detection step to solidify.

According to the above configuration, the time waveforms of the reflected pulses generated by the solidified processed object reflecting the laser pulse can be compared in the above determination step. Therefore, it is possible to more accurately determine whether or not the distance from the condenser lens to the object to be processed has approached the optimum value by the moving step.

In the control method according to the present invention, in the determination step, the pulse width of the reflection pulse detected in the irradiation detection step carried out this time is larger than the pulse width of the reflection pulse detected in the irradiation detection step carried out last time. It is preferable to determine that the distance from the condenser lens to the object to be processed approaches the optimum value when the value is narrow.

According to the above configuration, it is possible to easily and accurately determine whether or not the distance from the condenser lens to the object to be processed has approached the optimum value by the moving step.

In the control method according to the present invention, in the determination step, the falling edge width of the reflected pulse detected in the irradiation detection step carried out this time is the rise of the reflected pulse detected in the irradiation detection step carried out last time. It is preferable to determine that the distance from the condenser lens to the object to be processed approaches the optimum value when the width is narrower than the downlink edge width.

According to the above configuration, it is possible to easily and accurately determine whether or not the distance from the condenser lens to the object to be processed has approached the optimum value by the moving step.

In the control method according to the present invention, the moving step, the irradiation step, and the determination step are performed while bringing the condensing lens and the processing object closer to each other or keeping the condensing lens and the processing object away from each other. It is preferable to include a setting step of setting the distance from the condenser lens to the object to be processed by repeating the cycle including.

According to the above configuration, the distance from the condenser lens to the object to be processed can be accurately approached to the optimum value.

In the control method according to the present invention, the condenser lens is processed by repeating the cycle including the movement step, the irradiation detection step, and the determination step while bringing the condenser lens and the object to be processed close to each other. Before performing the first setting step of setting the distance to the object and the first setting step, or after performing the first setting step, while keeping the condenser lens and the processed object away from each other, the above A second setting step of setting the distance from the condenser lens to the processing object by repeating a cycle including the moving step, the irradiation detection step, and the determination step, the first setting step, and the second setting step. After performing the setting step, the distance from the condenser lens to the object to be processed is set to an intermediate value between the distance set in the first setting step and the distance set in the second setting step. It is preferable that the third setting step is included.

According to the above configuration, the distance from the condenser lens to the object to be processed can be brought closer to the optimum value with higher accuracy.

In the control method according to the present invention, the portion of the workpiece to be irradiated with the laser pulse in the first setting step is different from the portion of the workpiece to be irradiated with the laser pulse in the second setting step. , Is preferable.

According to the above configuration, it is possible to avoid a situation in which the portion of the workpiece to be irradiated with the laser pulse in the setting process performed later is damaged by the laser pulse irradiated in the setting process performed earlier. it can. Therefore, the first setting step and the second setting step can be carried out under the same conditions, and as a result, the distance from the condenser lens to the object to be processed can be made closer to the optimum value with higher accuracy.

In the control method according to the present invention, it is preferable that the portion of the work object to be irradiated with the laser pulse is different for each cycle.

According to the above configuration, it is possible to avoid a situation in which the portion of the workpiece to be irradiated with the laser pulse in the later cycle is disturbed by the laser pulse irradiated in the earlier cycle. Therefore, each cycle can be carried out under the same conditions, and as a result, the distance from the condenser lens to the object to be processed can be made closer to the optimum value with higher accuracy.

The laser pulse is generated by a MOPA type fiber laser, and in the irradiation detection step, the reflected pulse included in the return light branched from the output end of the PA unit, or the output end of the MO unit and the PA unit. It is preferable to detect the reflected pulse contained in the return light branched from the input end of the.

According to the above configuration, the reflected pulse can be effectively detected.

A laser processing machine that processes an object to be processed by using a laser pulse transmitted through a condenser lens and is provided with a control unit that implements the above control method is also included in the scope of the present invention. included.

According to one aspect of the present invention, it is possible to optimize the distance from the condenser lens to the object to be processed regardless of the material and surface condition of the object to be processed.

It is a block diagram which shows the structure of the laser processing machine which concerns on one Embodiment of this invention. (A) is a block diagram showing a first specific example of the fiber laser included in the laser processing machine shown in FIG. 1, and (b) is a second specific example of the fiber laser included in the laser processing machine shown in FIG. It is a block diagram which shows an example. (A) is a block diagram showing a third specific example of the fiber laser included in the laser processing machine shown in FIG. 1, and (b) is a fourth specific example of the fiber laser included in the laser processing machine shown in FIG. It is a block diagram which shows an example. It is a flowchart which shows the flow of the focus adjustment process in the laser processing machine shown in FIG. (A) is a graph showing the time waveform of the laser pulse output from the laser processing machine shown in FIG. (B) and (c) are graphs showing the time waveform of the reflected pulse generated by the object to be processed reflecting the laser pulse shown in (a). It is a figure which shows the operation example of the laser processing machine shown in FIG. (A) is a graph showing the pulse width W1 of the reflected pulse for each cycle, and (b) is a schematic diagram showing the positional relationship between the condenser lens and the work for each cycle. In the operation example of the laser processing machine shown in FIG. 1, the first operation A in which the distance from the condensing lens to the work is gradually increased and the operation B in which the distance from the condensing lens to the work is gradually shortened are performed. It is a figure which shows the operation example. In the operation example of the laser processing machine shown in FIG. 1, a second operation A in which the distance from the condenser lens to the work is gradually increased and an operation B in which the distance from the condenser lens to the work is gradually shortened are performed. It is a figure which shows the operation example.

[Construction of laser processing machine]
The configuration of the laser processing machine 1 according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a laser processing machine 1.

The laser processing machine 1 is a device for processing a work 2 (“object to be processed” in the claims) using a laser pulse, and as shown in FIG. 1, a laser device 11, a laser head 12, and a stand. It includes 13, a stage 14, and a processing machine control unit 15.

The laser device 11 is configured to generate a laser pulse. In the present embodiment, the laser apparatus 11 is composed of (1) a fiber laser 111 that generates a laser pulse, and (2) a laser apparatus control unit 112 that controls the fiber laser 111. The fiber laser 111 includes a photodiode PD that converts reflected pulses into a current signal, and the laser device control unit 112, in addition to the function of controlling the fiber laser 111, converts the current signal obtained by the photodiode PD into a current signal. It has a function to carry out the determination step described later with reference. The laser pulse generated by the laser device 11 is supplied to the laser head 12 via the delivery fiber DF. A configuration example of the fiber laser 111 including the photodiode PD will be described later with reference to the drawings.

The laser head 12 is configured to irradiate the work 2 with a laser pulse generated by the laser device 11. In the present embodiment, the laser head 12 has (1) a collimating lens 121 that converts the laser pulse emitted from the delivery fiber DF from divergent light into parallel light, and (2) the progress of the laser pulse that has passed through the collimating lens 121. A mirror 122 that converts the direction from the x-axis positive direction to the z-axis negative direction in the illustrated coordinate system, and (3) a condenser lens 123 that converts the laser pulse reflected by the mirror 122 from parallel light to convergent light. It is composed of and. The laser pulse transmitted through the condenser lens 123 is applied to the surface of the work 2.

The laser head 12 is movably held by the stand 13 in the direction parallel to the z-axis in the illustrated coordinate system, and the work 2 is moved by the stage 14 in the direction parallel to the xy plane in the illustrated coordinate system. It is held possible. The processing machine control unit 15 moves the laser head 12 in a direction parallel to the z-axis by controlling the stand 13, and moves the work 2 in a direction parallel to the xy plane by controlling the stage 14. be able to.

The laser machining machine 1 performs the focus adjustment process before starting the machining of the work 2. This focus adjustment process includes (1) a moving step of changing the distance from the condenser lens 123 to the work 2, (2) an irradiation step of irradiating the work 2 with a laser pulse, and (3) a work 2 performing a laser pulse. A cycle including a detection step of detecting a reflection pulse generated by reflection and a determination step of (4) determining whether or not the distance from the condenser lens 123 to the work 2 has approached the optimum value by the moving step. This is achieved by repeating until the determination result in the determination step becomes "false".

In the present embodiment, the moving step is realized by the stand 13 moving the laser head 12 in a direction parallel to the z-axis under the control of the processing machine control unit 15. Further, the irradiation step is realized by the fiber laser 111 generating a laser pulse under the control of the laser apparatus control unit 112. Further, the detection step is realized by converting the reflected pulse into a current signal by the photodiode PD and acquiring the current signal by the laser apparatus control unit 112. Further, in the determination step, the laser apparatus control unit 112 sets the time waveform of the reflected pulse detected in the detection step of the current cycle (that is, the time waveform of the current signal acquired from the photodiode PD) and the detection step of the previous cycle. It is realized by comparing the time waveform of the reflected pulse detected in the above. A specific example of the focus adjustment process will be described later instead of the reference drawing.

As a determination method for determining whether or not the distance from the condenser lens 123 to the work 2 has approached the optimum value in the determination step, for example, (a) the pulse width of the reflected pulse detected in the detection step of the current cycle is used. A method of determining that the distance from the condenser lens 123 to the work 2 has approached the optimum value when the pulse width of the reflected pulse detected in the irradiation detection step of the previous cycle is narrower, or (b) the current cycle. The distance from the condenser lens 123 to the work 2 is optimal when the falling edge width of the reflected pulse detected in the detection step is narrower than the falling edge width of the reflected pulse detected in the detection step of the previous cycle. Examples thereof include a determination method for determining that the value is approaching. The reason why it is possible to determine whether or not the distance from the condenser lens 123 to the work 2 has approached the optimum value by such a determination method will be described later instead of the reference drawing.

In this embodiment, the stand 13 is used to move the laser head 12 in a direction parallel to the z-axis to change the distance from the condenser lens 123 to the surface of the work 2. However, the present invention is not limited to this. That is, a configuration may be adopted in which the distance from the condenser lens 123 to the surface of the work 2 is changed by moving the work 2 in a direction parallel to the z-axis using the stage 14.

Further, in the present embodiment, a configuration is adopted in which the position where the laser pulse is irradiated on the surface of the work 2 is changed by moving the work 2 in a direction parallel to the xy plane using the stage 14. , The present invention is not limited to this. That is, a configuration may be adopted in which the position where the laser pulse is irradiated is changed on the surface of the work 2 by moving the laser head 12 in a direction parallel to the xy plane using the stand 13.

[Structure example of fiber laser]
A configuration example of the fiber laser 111 included in the laser processing machine 1 shown in FIG. 1 will be described with reference to FIGS. 2 and 3.

FIG. 2A is a block diagram showing a first configuration example of the fiber laser 111, and FIG. 2B is a block diagram showing a second configuration example of the fiber laser 111.

The fiber lasers 111 shown in FIGS. 2 (a) and 2 (b) both have an MO (Master Oscillator) unit MO that generates laser light and a PA (Power) that amplifies the laser light generated by the MO unit MO. This is a MOPA type fiber laser including an amplifier) unit PA and a delivery fiber DF that guides the laser beam amplified by the PA unit PA to the laser head 12.

As shown in FIGS. 2A and 2B, the MO unit MO is composed of a laser diode LD1 that functions as a seed light source. The laser diode LD1 uses the drive current supplied from the current source I1 to generate a laser beam. The laser light generated by the laser diode LD1 is supplied to the PA unit PA.

As shown in (a) and (b) of FIG. 2, the PA section PA includes (1) a plurality of laser diodes LD21 to LD24 functioning as an excitation light source, and (2) one input port of the MO section MO (from the MO section MO. Specifically, for amplification, a pump combiner PC connected to the radar diode LD1) and the remaining input ports connected to the laser diodes LD21 to LD24, and (3) the incident end connected to the output port of the pump combiner PC. It is equipped with a fiber AF. The amplification fiber AF is a double-clad fiber in which a rare earth element is added to the core.

Each part of PA part PA amplifies the laser light generated by MO part MO as follows. That is, the laser diodes LD21 to LD24 generate excitation light by using the drive current supplied from the current source I2. The pump combiner PC combines the excitation light generated by the laser diodes LD21 to LD24 and transmits the laser light supplied from the MO unit MO. The amplification fiber AF amplifies the laser light transmitted through the pump combiner PC by using the excitation light combined with the pump combiner PC. The laser light amplified by the amplification fiber AF is supplied to the above-mentioned laser head 12 via the delivery fiber DF.

The fiber laser 111 shown in FIGS. 2A and 2B is a direct modulation type fiber type pulse laser. That is, when a constant drive current is supplied from the current source I2 to the laser diodes LD21 to LD24 and a drive current having a certain pulse pattern is supplied from the current source I1 to the laser diode LD11, the laser beam having the pulse pattern is a fiber laser. It is output from 111. The laser device control unit 112 controls the current source I1 and the current source I2.

In the laser processing machine 1, the laser pulse output from the fiber laser 111 is applied to the work 2 via the laser head 12. Then, the reflected pulse generated by the work 2 reflecting this laser pulse is input to the laser device 11 via the laser head 12. The fiber laser 111 shown in FIGS. 2A and 2B includes an optical coupler C and a photodiode PD as a configuration for detecting the reflected pulse.

In the fiber laser 111 shown in FIG. 2A, the optical coupler C is inserted between the delivery fiber DF and the amplification fiber AF, and is one of the reflected pulses that enter the amplification fiber AF from the delivery fiber DF. The part is led to the photodiode PD. The photodiode PD converts the reflected pulse into a current signal and supplies the obtained current signal to the laser apparatus control unit 112.

On the other hand, in the fiber laser 111 shown in FIG. 2B, the optical coupler C is inserted between the input port of the pump combiner PC and the low reflection fiber Bragg grating FBG2, and is low from the input port of the pump combiner PC. A part of the reflected pulse entering the reflective fiber Bragg grating FBG2 is guided to the photodiode PD. The photodiode PD converts the reflected pulse into a current signal and supplies the obtained current signal to the laser apparatus control unit 112.

In the focus adjustment process described above, the laser apparatus control unit 112 carries out a determination step based on the current signal obtained by the photodiode PD. That is, by comparing the time waveform of the current signal acquired from the photodiode PD in the current cycle with the time waveform of the current signal acquired from the photodiode PD in the previous cycle, the distance from the condenser lens 123 to the work 2 Determines whether or not is close to the optimum value.

FIG. 3A is a block diagram showing a third configuration example of the fiber laser 111, and FIG. 3B is a block diagram showing a fourth configuration example of the fiber laser 111.

The fiber laser 111 shown in FIGS. 3 (a) and 3 (b) is the same as the fiber laser 111 shown in FIGS. 2 (a) and 2 (b). It is a MOPA type fiber laser including a PA unit PA that amplifies the generated laser light and a delivery fiber DF that guides the laser light amplified by the PA unit PA to the laser head 12.

However, the fiber laser 111 shown in FIGS. 3A and 3B is a Q-switch type fiber type pulse laser, and an acoustic optical element AOM is provided between the MO section MO and the PA section PA. .. In the fiber laser 111 shown in FIGS. 3A and 3B, the acoustic optical element AOM has a certain pulse pattern while supplying a constant drive current from the current sources I1 and I2 to the laser diodes LD11 to 15 and LD21 to LD24. When ON / OFF control is performed, laser light corresponding to the Q value of the resonator corresponding to the pulse pattern is output from the fiber laser 111. The laser device control unit 112 controls the current sources I1 and I2 and the acoustic optical element AOM.

[Specific example of focus adjustment processing]
A specific example of the focus control process performed by the laser machine 1 shown in FIG. 1 will be described with reference to FIG. FIG. 4 is a flowchart showing the flow of the focus adjustment process. FIG. 4 shows in parallel a process in which the processing machine control unit 15 is the control main body and a process in which the laser device control unit 112 is the control main body.

First, the processing machine control unit 15 gives a mode change instruction instructing the laser device control unit 112 to change the operation mode to the adjustment mode (step S11). In response to this mode change instruction, the laser device control unit 112 changes the operation mode from the normal mode to the adjustment mode, and returns a mode change completion notification to the processing machine control unit 15 (step S21). When the laser device control unit 112 completes the change of the operation mode, the laser device control unit 112 waits for the laser ON instruction from the processing machine control unit 15 (step S22: NO).

Upon confirming this mode change completion notification, the processing machine control unit 15 gives a laser ON instruction to the laser device control unit 112 (step S12). When the fiber laser 111 is a direct modulation type fiber pulse laser shown in FIG. 2, the laser apparatus control unit 112 switches the current source I2 to the ON state in response to a laser ON instruction from the processing machine control unit 15. The laser diodes LD21 to LD24 are turned on. After that, the laser device control unit 112 momentarily switches the current source I1 to the ON state while the laser diodes LD21 to LD24 are lit, and momentarily turns on the laser diode LD11 to turn on the fiber laser 111. Output a single laser pulse. On the other hand, when the fiber laser 111 is a Q-switch type fiber pulse laser shown in FIG. 3, the laser device control unit 112 turns on the current sources I1 and I2 in response to a laser ON instruction from the laser device control unit 112. The state is switched and the laser diodes LD11, LD21 to LD24 are turned on. After that, the laser device control unit 112 controls the acoustic optical element AOM while the laser diodes LD11 and LD21 to LD24 are lit to momentarily switch the Q value of the resonator to a high state, thereby causing a fiber laser. Have 111 output a single laser pulse. As a result, the photodiode PD is subjected to an irradiation step of irradiating the work 2 with the laser pulse generated by the laser device 11 using the laser head 12, and a reflected pulse generated by the work 2 reflecting the laser pulse. The detection step of using and detecting is executed (step S23).

After that, the processing machine control unit 15 gives a laser OFF instruction to the laser device control unit 112 (step S13). The laser device control unit 112 switches the current source I2 to the OFF state and turns off the laser diodes LD21 to LD24 in response to the laser OFF instruction. After that, the laser device control unit 112 executes a determination step of determining whether or not the distance from the condenser lens 123 to the work 2 approaches the optimum value, and notifies the processing machine control unit 15 of the determination result (step). S25). In the determination step, the laser apparatus control unit 112 compares the time waveform of the reflected pulse detected in the detection step of the current cycle with the reflected pulse detected in the detection step of the previous cycle, and thereby the condensing lens 123. It is determined whether or not the distance from the work 2 to the work 2 has approached the optimum value. More specifically, (a) when the pulse width W1 of the reflected pulse detected in the detection step of the current cycle is narrower than the pulse width W1 of the reflected pulse detected in the irradiation detection step of the previous cycle, or (B) When the falling edge width W2 of the reflected pulse detected in the detection step of the current cycle is narrower than the falling edge width W2 of the reflected pulse detected in the detection step of the previous cycle, the condenser lens 123 It is determined that the distance from the work 2 to the work 2 has approached the optimum value.

When the truth value of the judgment result notified from the laser device control unit 112 is "true" as in the judgment result of the previous cycle, that is, when the distance from the condenser lens 123 to the work 2 is approaching the optimum value. (Step S14: NO), the processing machine control unit 15 executes a moving step of changing the distance from the condenser lens 123 to the work 2 (step S15). Then, when the processing machine control unit 15 completes the execution of the moving process, the processing machine control unit 15 gives the laser ON instruction to the laser device control unit 112 again (step S12). In this case, steps S12 to S14 and S22 to S25 described above are repeated.

On the other hand, when the truth value of the determination result notified from the laser device control unit 112 is "false" unlike the determination result of the previous cycle, that is, the distance from the condenser lens 123 to the work 2 exceeds the optimum value. When it becomes too small or too large (step S14: YES), the processing machine control unit 15 executes a moving step of returning the distance from the condenser lens 123 to the work 2 to the distance when the detection step of the previous cycle is performed. (Step S16). Then, the processing machine control unit 15 gives a mode change instruction instructing the laser device control unit 112 to change the operation mode to the normal mode (step S17). The laser apparatus control unit 112 changes the operation mode from the normal mode to the adjustment mode in response to the mode change instruction (step S26). As a result, the focus control process is completed.

In the focus adjustment process described above, a configuration in which a laser pulse is irradiated to the same portion of the work 2 in the irradiation step of each cycle is adopted, but the present invention is not limited to this. That is, in the irradiation step of each cycle, a configuration in which the laser pulse is irradiated to different parts of the work 2 may be adopted. When the latter configuration is adopted, the processing machine control unit 15 moves the laser head 12 in a direction parallel to the z-axis to change the distance from the condenser lens 123 to the work 2 when the work 2 is changed. By moving in a direction parallel to the xy plane, the portion of the work 2 to which the laser pulse is irradiated may be changed.

Further, in the above-mentioned focus adjustment process, when the determination result in the determination step is "true", a configuration is adopted in which the irradiation step in the next cycle is started immediately after the irradiation step in the current cycle is completed. The present invention is not limited to this. That is, when the determination result in the determination step is "true", a configuration may be adopted in which the irradiation step in the next cycle is started after a predetermined waiting time elapses after the irradiation step in the current cycle is completed. When the latter configuration is adopted, the above-mentioned waiting time is preferably longer than the time required for the surface of the work 2 melted in the irradiation step of the current cycle to solidify. The time required for the surface of the work 2 melted in the irradiation step of each cycle to solidify is about the same as the pulse width of the laser pulse. Therefore, the above-mentioned standby time is preferably twice or more the pulse width of the laser pulse, and more preferably three times or more the pulse width of the laser pulse.

FIG. 5A is a graph showing the time waveform of the laser pulse output by the laser processing machine 1, and FIG. 5B is a reflection of the laser pulse when it is not in focus on the surface of the work 2. It is a graph which shows the time waveform of a pulse, and (c) of FIG. 5 is a graph which shows the time waveform of the reflected pulse when a laser pulse is focused on the surface of the work 2.

With reference to FIGS. 5A and 5B, the time waveform of the reflected pulse when the laser pulse is not in focus on the surface of the work 2 has the same shape as the time waveform of the laser pulse in terms of relative power. It turns out that. On the other hand, referring to FIGS. 5A and 5C, the time waveform of the reflected pulse when the laser pulse is in focus on the surface of the work 2 is the time waveform of the laser pulse even when viewed in terms of relative power. It can be seen that the shapes are different and the spread of the time waveform of the laser pulse is small. For example, the pulse width W1 and the falling edge width W2 of the reflected pulse are such that when the laser pulse is in focus on the surface of the work 2, the laser pulse is not in focus on the surface of the work target 2. Is also getting smaller. The reason for this difference is that when the laser pulse is not in focus on the surface of the work 2, the laser pulse is not absorbed by the work 2 (its energy is not consumed to melt the work 2). It is considered that this is because when the laser pulse is focused on the surface of the work 2, the laser pulse is absorbed by the work 2 (the energy is consumed to melt the work 2).

As is clear from FIG. 5, the closer the distance from the lens 123 to the work 2 is to the optimum value, that is, the closer the focus of the laser pulse is to the surface of the workpiece 2, the more the time waveform of the reflected pulse is. Spread becomes smaller. Therefore, whether or not the distance from the lens 123 to the work 2 approaches the optimum value can be determined depending on whether or not the spread of the time waveform of the reflected pulse is reduced. For example, (a) when the pulse width W1 of the reflected pulse detected in the detection step of the current cycle is narrower than the pulse width W1 of the reflected pulse detected in the irradiation detection step of the previous cycle, or (b) the current cycle. The distance from the lens 123 to the work 2 when the falling edge width W2 of the reflected pulse detected in the cycle detection step is narrower than the falling edge width W2 of the reflected pulse detected in the detection step of the previous cycle. This is the reason why it can be determined that is approaching the optimum value.

In FIG. 5, the pulse width W1 is defined as the time width in which the power becomes 50% or more of the peak power, but the method of taking the lower limit value is arbitrary. That is, the above conclusion can be obtained even if the time width in which the power becomes 40% or more of the peak power is the pulse width W1 or the time width in which the power becomes 60% or more of the peak power is the pulse width W1. Therefore, the pulse width W1 can be generalized to a time width in which the power becomes α% or more of the peak power, with α (0 <α <100) as a predetermined constant. However, by setting α to 30 ≦ α ≦ 70 or less, a pulse width W1 that appropriately reflects the time waveform of the laser pulse can be obtained.

Further, in FIG. 5, the time required for the power to decrease from 90% of the peak power to 10% of the peak power is defined as the falling edge width W2, but the upper limit value and the lower limit value can be taken arbitrarily. .. That is, the time required for the power to decrease from 85% of the peak power to 15% of the peak power can be set as the falling edge width W2, or the power decreases from 95% of the peak power to 5% of the peak power. The above-mentioned conclusion can be obtained even if the time required for this is set to the falling edge width W2. Therefore, the falling edge width W2 is the time required for the power to decrease from β2% of the peak power to β1% of the peak power, with β1 and β2 (0 <β1 <β2 <100) as predetermined constants. Can be generalized as.

FIG. 6 is a diagram showing a first operation example of the laser processing machine 1 shown in FIG. In FIG. 6, FIG. 6A is a graph showing the pulse width W1 of the reflected pulse for each cycle, and FIG. 6B is a schematic diagram showing the positional relationship between the condenser lens 123 and the work 2. In this operation example, as shown in FIG. 6B, when the condensing lens 123 is gradually brought closer to the object to be processed 123, particularly, the condensing lens 123 that focuses the laser pulse on the surface of the work 2 This is an operation example when the position is near the position of the condenser lens 123 in the cycle of N = 4.

In the cycle from N = 1 to N = 4, as shown in FIG. 6A, the pulse width W1 of the reflected pulse detected in the current cycle is smaller than the pulse width W2 of the reflected pulse detected in the previous cycle. Become. Therefore, in the cycle from N = 1 to N4, as shown in FIG. 6B, a moving step of bringing the condenser lens 123 closer to the work 2 is carried out, and the condenser lens 123 to the work 2 in the next cycle is carried out. Is shorter than the distance from the condenser lens 123 to the object to be processed in the current cycle. On the other hand, in the cycle of N = 5, as shown in FIG. 6A, the pulse width W1 of the reflected pulse detected in the current cycle becomes larger than the pulse width W1 of the reflected pulse detected in the previous cycle. Therefore, in the cycle of N = 5, as shown in FIG. 6B, the moving step of returning the condenser lens 123 to the position in the cycle of N = 4 is carried out, and the focus adjustment process is completed in this cycle. To do. Thereby, the distance from the condenser lens 123 to the work 2 can be set to a value close to the optimum value.

Although this operation example is an operation example in which the distance from the condenser lens 123 to the work 2 is gradually shortened, the method for changing the distance from the condenser lens 123 to the work 2 is not limited to this. That is, even when the distance from the condenser lens 123 to the work 2 is gradually increased, the laser processing machine 1 operates in the same manner as in this operation example.

Further, the operation A for gradually increasing the distance from the condensing lens 123 to the work 2 and the operation B for gradually shortening the distance from the condensing lens 123 to the work 2 are performed, respectively, and the condensing set by the operation A is performed. An intermediate value (for example, an average value) between the distance ZA from the lens 123 to the work 2 and the distance ZB from the condenser lens 123 to the work 2 set by the operation B is set to the final condenser lens 123 to the work 2. It may be set as the distance Z to. The setting of the distance ZA by the operation A and the setting of the distance ZB by the operation B may be performed before setting the distance Z, and after the setting of the distance ZA by the operation A is completed, the distance ZB by the operation B may be set. The setting may be performed, or the distance ZA may be set by the operation A after the setting of the distance ZB by the operation B is completed.

FIG. 7 shows a first operation example in which both operation A and operation B are performed. The operation example shown in FIG. 7 is an operation example in the case where the place where the laser pulse is irradiated in the operation A and the place where the laser pulse is irradiated in the operation B are the same in the work 2. In the operation A, the distance Z from the condenser lens 123 to the work 2 is gradually increased in the order of ZA1 → ZA2 → ZA3. At this time, the pulse width W1 of the reflected pulse changes from WA1 to WA2 to WA3, and the pulse width W1 changes from decreasing to increasing in the third cycle. Therefore, the distance ZA from the condenser lens 123 to the work 2 obtained by the operation A is the position ZA2 in the second cycle. On the other hand, in the operation B, the distance Z from the condenser lens 123 to the work 2 is gradually reduced in the order of ZB1 → ZB2 → ZB3 → ZB4. At this time, the pulse width W1 of the reflected pulse changes in the order of WB1 → WB2 → WB3 → WB4, and the pulse width W1 changes from decreasing to increasing in the fourth cycle. Therefore, the distance ZA from the condenser lens 123 to the work 2 obtained by the operation B is the position ZB3 in the third cycle. Therefore, the final distance Z from the condenser lens 123 to the work 2 in the operation example shown in FIG. 7 is Z = (ZA2 + ZB3) / 2.

FIG. 8 shows a second operation example in which both operation A and operation B are performed. The operation example shown in FIG. 8 is an operation example in which the place where the laser pulse is irradiated in the operation A and the place where the laser pulse is irradiated in the operation B are different in the work 2. In the operation A, the distance Z from the condenser lens 123 to the work 2 is gradually increased in the order of Z1 → Z2 → Z3 → Z4. At this time, the pulse width W1 of the reflected pulse changes in the order of W11 → W12 → W13 → W14, and the pulse width W1 changes from decreasing to increasing in the fourth cycle. Therefore, the distance ZA from the condenser lens 123 to the work 2 obtained by the operation A is the position Z3 in the third cycle. On the other hand, in the operation B, the distance Z from the condenser lens 123 to the work 2 is gradually reduced in the order of Z6 → Z5 → Z4 → ZB3. At this time, the pulse width W1 of the reflected pulse changes in the order of W11 → W12 → WB13 → WB14, and the pulse width W1 changes from decreasing to increasing in the fourth cycle. Therefore, the distance ZA from the condenser lens 123 to the work 2 obtained by the operation B is the position Z4 in the third cycle. Therefore, the final distance Z from the condenser lens 123 to the work 2 in the operation example shown in FIG. 8 is Z = (Z3 + Z4) / 2.

Further, in this operation example, when the pulse width W1 of the reflected pulse detected in the current cycle is narrower than the pulse width W1 of the reflected pulse detected in the previous cycle, the distance from the lens 123 to the work 2 approaches the optimum value. Although it is an operation example in the case of determination, the method of determining whether or not the distance from the lens 123 to the work 2 has approached the optimum value is not limited to this. That is, when the falling edge width W2 of the reflected pulse detected in the current cycle is narrower than the falling edge width W2 of the reflected pulse detected in the previous cycle, it is determined that the distance from the lens 123 to the work 2 has approached the optimum value. Even in this case, the laser processing machine 1 operates in the same manner as in this operation example.

[Additional notes]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

1 Laser machining machine 2 Work (workpiece)
11 Laser device 111 Fiber laser 112 Laser device control unit 12 Laser head 13 Stand 14 Stage 15 Processing machine control unit 123 Condensing lens MO MO unit PA PA unit W1 Pulse width W2 Falling edge width

Claims (10)

It is a control method that controls a laser processing machine that processes an object to be processed using a laser pulse transmitted through a condenser lens.
A moving step of changing the distance from the condensing lens to the processed object by moving the condensing lens or the processed object.
An irradiation detection step of irradiating the processed object with the laser pulse and detecting a reflected pulse generated by reflecting the laser pulse on the processed object.
The time waveform of the reflection pulse detected in the irradiation detection step carried out after the movement step, and the time waveform of the reflection pulse detected in the irradiation detection step carried out before the movement step. A determination step of determining whether or not the distance from the condenser lens to the object to be processed has approached the optimum value by the moving step is included.
In the determination step, when the pulse width of the reflection pulse detected in the irradiation detection step carried out this time is narrower than the pulse width of the reflection pulse detected in the irradiation detection step carried out last time, the condenser lens It is determined that the distance from the object to the object to be processed has approached the optimum value.
A control method characterized by that. It is a control method that controls a laser processing machine that processes an object to be processed using a laser pulse transmitted through a condenser lens.
A moving step of changing the distance from the condensing lens to the processed object by moving the condensing lens or the processed object.
An irradiation detection step of irradiating the processed object with the laser pulse and detecting a reflected pulse generated by reflecting the laser pulse on the processed object.
The time waveform of the reflection pulse detected in the irradiation detection step carried out after the movement step, and the time waveform of the reflection pulse detected in the irradiation detection step carried out before the movement step. A determination step of determining whether or not the distance from the condenser lens to the object to be processed has approached the optimum value by the moving step is included.
In the above determination step, when the falling edge width of the reflected pulse detected in the irradiation detection step carried out this time is narrower than the falling edge width of the reflected pulse detected in the irradiation detection step carried out last time. It is determined that the distance from the condenser lens to the object to be processed has approached the optimum value.
A control method characterized by that. The time from the end of the irradiation of the laser pulse in the irradiation detection step carried out last time to the start of the irradiation of the laser pulse in the irradiation detection step carried out this time was melted in the irradiation detection step carried out last time. Longer than the time it takes for the surface of the object to be processed to solidify,
The control method according to claim 1 or 2. By repeating the cycle including the movement step, the irradiation detection step, and the determination step while bringing the condenser lens and the processing object closer to each other or keeping the condenser lens and the processing target away from each other. Includes a setting step to set the distance from the condenser lens to the object to be processed.
The control method according to any one of claims 1 to 3 , wherein the control method is characterized by the above. It is a control method that controls a laser processing machine that processes an object to be processed using a laser pulse transmitted through a condenser lens.
A moving step of changing the distance from the condensing lens to the processed object by moving the condensing lens or the processed object.
An irradiation detection step of irradiating the processed object with the laser pulse and detecting a reflected pulse generated by reflecting the laser pulse on the processed object.
The time waveform of the reflection pulse detected in the irradiation detection step carried out after the movement step, and the time waveform of the reflection pulse detected in the irradiation detection step carried out before the movement step. A determination step of determining whether or not the distance from the condenser lens to the object to be processed has approached the optimum value by the moving step is included.
The distance from the condenser lens to the processing target is set by repeating the cycle including the moving step, the irradiation detection step, and the determination step while bringing the condenser lens and the processing target close to each other. 1 setting process and
Before performing the first setting step, or after performing the first setting step, the moving step, the irradiation detection step, and the determination step are performed while keeping the condenser lens and the object to be processed away from each other. A second setting step of setting the distance from the condenser lens to the object to be processed by repeating the including cycle, and
After performing the first setting step and the second setting step, the distance from the condenser lens to the object to be processed is set by the distance set in the first setting step and the second setting step. Includes a third setting step, which sets an intermediate value to the distance set.
A control method characterized by that. The portion of the workpiece to be irradiated with the laser pulse in the first setting step is different from the portion of the workpiece to be irradiated with the laser pulse in the second setting step.
The control method according to claim 5 , wherein the control method is characterized by the above. It is a control method that controls a laser processing machine that processes an object to be processed using a laser pulse transmitted through a condenser lens.
A moving step of changing the distance from the condensing lens to the processed object by moving the condensing lens or the processed object.
An irradiation detection step of irradiating the processed object with the laser pulse and detecting a reflected pulse generated by reflecting the laser pulse on the processed object.
The time waveform of the reflection pulse detected in the irradiation detection step carried out after the movement step, and the time waveform of the reflection pulse detected in the irradiation detection step carried out before the movement step. A determination step of determining whether or not the distance from the condenser lens to the object to be processed has approached the optimum value by the moving step is included.
By repeating the cycle including the movement step, the irradiation detection step, and the determination step while bringing the condenser lens and the processing object closer to each other or keeping the condenser lens and the processing target away from each other. Includes a setting step to set the distance from the condenser lens to the object to be processed.
The location where the laser pulse is applied to the above-mentioned object to be processed differs from cycle to cycle.
A control method characterized by that. The laser pulse is generated by a MOPA type fiber laser.
In the irradiation detection step, the reflected pulse contained in the return light branched from the output end of the PA unit is detected.
The control method according to any one of claims 1 to 7 , wherein the control method is characterized by the above. The laser pulse is generated by a MOPA type fiber laser.
In the irradiation detection step, the reflected pulse included in the return light branched from the output end of the MO unit and the input end of the PA unit is detected.
The control method according to any one of claims 1 to 7 , wherein the control method is characterized by the above. A laser processing machine that processes an object to be processed by using a laser pulse transmitted through a condenser lens, and includes a control unit that implements the control method according to any one of claims 1 to 9. A laser processing machine characterized by.

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