JP2022053804A - Laser processing method and laser processing machine - Google Patents

Abstract

To improve the processing quality of a workpiece.SOLUTION: The laser processing method for laser-cutting a workpiece K made of soft steel by using oxygen as an assist gas reduces a cutting speed V from a prescribed first speed V1 to zero while the irradiation position M of a laser beam LB reaches the tip Ct of a corner C from the front side of the top Ct of the corner C on a processing route SR. The method accelerates the cutting speed V to the first speed V1 while the irradiation position M of the laser beam LB reaches a prescribed place SRa from the tip Ct of the corner C. The absolute value of acceleration for reducing the cutting speed V while the irradiation position M of the laser beam LB reaches the tip Ct of the corner C from the front side of the top Ct of the corner C is set smaller than that of acceleration for accelerating the cutting speed V while the irradiation position M of the laser beam LB reaches the place SRa from the tip Ct of the corner C.SELECTED DRAWING: Figure 3

Description

The present invention relates to a laser processing method and a laser processing machine for performing laser cutting processing on a work.

When laser cutting is performed on a thick plate work made of mild steel along a processing path, oxygen processing using oxygen as an assist gas is selected. In oxygen processing, the work can be melted by the heat of the oxidation reaction in addition to the energy of the laser beam. In addition, when the processing path includes a corner portion (acute angle portion or edge portion), when the irradiation position of the laser beam reaches the tip of the corner portion of the processing path, it is used as a processing method for the corner portion of the laser processing machine. , The cutting speed and laser output of the laser processing machine are lowered to suppress the occurrence of burning (see Patent Document 1 and Patent Document 2).

Japanese Patent No. 3211902 Japanese Unexamined Patent Publication No. 7-195186

By the way, as the plate thickness of the work increases, the delay of the locus of the molten metal (trajectory of the cutting position) on the back surface side of the work with respect to the locus of the irradiation position of the laser beam becomes large, and a large dent is formed on the corner portion side on the back surface of the work. Occurs. In particular, when the cutting speed and the laser output of the laser processing machine are increased in order to shorten the cutting time of the laser processing machine, the dent becomes larger.

Further, in order to reduce the delay of the trajectory of the molten metal on the back surface side of the work, in addition to the processing method of the corner portion that lowers the cutting speed and the laser output of the laser processing machine, the irradiation position of the laser beam is located at the tip of the corner portion. After reaching the point, the irradiation position of the laser beam may be stopped at the tip of the corner portion for a predetermined time. When this method is adopted, the dent on the inner corner side of the corner portion on the back surface of the work can be reduced, but the dent on the outer corner side of the corner portion on the back surface of the work becomes large.

That is, when laser cutting is performed on a thick plate work made of mild steel, there is a problem that it is difficult to reduce the dents on the outer corner side and the inner corner side of the corner portion on the back surface of the work. Further, when processing is performed to reduce the cutting speed and the laser output before and after the corner portion, there arises a problem that the cut surface (the portion following the tip of the corner portion) after passing through the tip of the corner becomes rough.

Therefore, in the above-mentioned case, the present invention reduces the dents on the outer and inner corners of the corner portion on the back surface of the work while suppressing the portion of the cut surface of the work that follows the tip of the corner portion from becoming rough. It is an object of the present invention to provide a laser processing method and a laser processing machine for improving the processing quality of a work.

The laser processing method according to the first embodiment is a laser processing method in which oxygen is used as an assist gas and laser cutting is performed on a workpiece made of mild steel along a processing path including a corner portion, and is irradiated with a laser beam. The cutting speed (machining speed) is reduced from a predetermined first speed to zero while the position reaches the tip of the corner portion from the front side of the tip (top) of the corner portion in the machining path. While the irradiation position of the laser beam reaches a predetermined position from the tip of the corner portion in the processing path, the cutting speed is accelerated to the predetermined first speed. The acceleration that reduces the cutting speed (acceleration during deceleration) when the irradiation position of the laser beam is from the front side of the tip of the corner portion to the tip of the corner portion is that the irradiation position of the laser beam is the tip of the corner portion. It is set to be smaller than the acceleration for accelerating the cutting speed (acceleration at the time of acceleration) from the to the predetermined position.

While the irradiation position of the laser beam reaches the predetermined position from the tip of the corner portion, the cutting speed is accelerated from zero to a predetermined second speed lower than the predetermined first speed to maintain the speed, and then the speed is maintained. , The cutting speed may be accelerated to the predetermined first speed. In this case, when the irradiation position of the laser beam reaches the tip of the corner portion of the processing path, the laser output is switched from the predetermined first output to a predetermined second output or zero lower than the predetermined first output. Alternatively, the output may be switched to the predetermined second output after the value is once set to zero. When the irradiation position of the laser beam reaches the predetermined position of the processing path, the laser output is switched from the predetermined second output or zero to the predetermined first output, or once set to zero, the predetermined second output is performed. You may switch to one output.

According to the laser processing method according to the first embodiment, after the irradiation position of the laser beam reaches the tip of the corner portion, the laser is maintained while keeping the acceleration of the cutting speed equal to or the same as the standard (normal) acceleration. It is possible to reduce only the acceleration of the cutting speed (acceleration during deceleration) when the irradiation position of the beam is from the front side of the tip of the corner portion to the tip of the corner portion. As a result, while suppressing excessive heat input to the work when accelerating the cutting speed, the locus of the molten metal on the back surface side of the work (trajectory of the cutting position) is delayed with respect to the locus of the irradiation position of the laser beam. Can be reduced.

The laser processing machine according to the second embodiment is optically connected to a laser oscillator that oscillates (outputs) a laser beam and the laser beam while injecting oxygen as an assist gas toward a workpiece made of mild steel. It is provided with a processing head that irradiates the laser, a head moving unit that moves the processing head in a horizontal direction relative to the work, and a control device that controls the laser oscillator and the head moving unit. In the control device, the cutting speed (machining speed) is decelerated from a predetermined first speed to zero while the irradiation position of the laser beam is from the front side of the tip of the corner portion in the machining path to the tip of the corner portion. The head moving portion is controlled in such a manner. The control device controls the head moving portion so that the cutting speed accelerates to the predetermined first speed while the irradiation position of the laser beam reaches a predetermined position from the tip of the corner portion in the processing path. Then, in the control device, the acceleration at which the irradiation position of the laser beam is from the front side of the tip of the corner portion to the tip of the corner portion is the acceleration for decelerating the cutting speed, and the irradiation position of the laser beam is the corner portion. It is set to be smaller than the acceleration that accelerates the cutting speed between the tip and the predetermined location.

The control device accelerates the cutting speed from zero to a predetermined second speed lower than the predetermined first speed while the irradiation position of the laser beam reaches the predetermined position from the tip of the corner portion. The head moving unit may be controlled so as to maintain the above speed, and then the head moving unit may be controlled so that the cutting speed accelerates from the predetermined second speed to the predetermined first speed. In this case, when the irradiation position of the laser beam reaches the tip of the corner portion of the processing path, the control device has a predetermined second output whose laser output is lower than the predetermined first output to the predetermined first output. The laser oscillator may be controlled to switch to an output or zero, or once to zero and then to the predetermined second output. When the irradiation position of the laser beam reaches the predetermined position of the processing path, the control device switches the laser output from the predetermined second output or zero to the predetermined first output, or temporarily sets the laser output to zero. The laser oscillator may be controlled so as to later switch to the predetermined first output.

According to the configuration of the laser processing machine according to the second embodiment, the laser beam after the irradiation position of the laser beam reaches the tip of the corner portion while keeping the acceleration of the cutting speed equal to or the same as the standard acceleration. It is possible to reduce only the acceleration of the cutting speed (acceleration during deceleration) between the irradiation position from the front side of the tip of the corner portion to the tip of the corner portion. As a result, it is possible to reduce the delay of the locus of the molten metal on the back surface side of the work with respect to the locus of the irradiation position of the laser beam while suppressing the excessive heat input to the work when accelerating the cutting speed.

According to the present invention, when laser cutting is performed on a thick plate work made of mild steel, the corner on the back surface of the work is suppressed while suppressing the portion following the tip of the corner on the cut surface of the work from becoming rough. By reducing the dents on the outer and inner corners of the part, the processing quality of the work is improved.

FIG. 1 is a schematic view of a laser processing apparatus according to the present embodiment. FIG. 2 is a diagram illustrating a processing path including a corner portion. FIG. 3 is a diagram for explaining the laser processing method according to the present embodiment, and is a diagram showing the relationship between the cutting speed, the laser output, and the time. FIG. 4A is a photograph showing a part of the back surface of the work that has been laser-cut by the laser machining method according to the present embodiment. FIG. 4B is a photograph showing a part of the cut surface of the work subjected to the laser cutting process by the laser processing method according to the present embodiment. FIG. 5 is a diagram showing the relationship between the acceleration for decelerating the cutting speed (acceleration during deceleration) and the amount of dent on the corner portion side on the back surface of the work. FIG. 6 is a diagram for explaining the laser processing method according to Comparative Example 1, and is a diagram showing the relationship between the cutting speed, the laser output, and the time. FIG. 7A is a photograph showing a part of the back surface of the work that has been laser-cut by the laser machining method according to Comparative Example 1. FIG. 7B is a photograph showing a part of the cut surface of the work subjected to the laser cutting process by the laser processing method according to Comparative Example 1. FIG. 8 is a diagram for explaining the laser processing method according to Comparative Example 2, and is a diagram showing the relationship between the cutting speed, the laser output, and the time. FIG. 9A is a photograph showing a part of the back surface of the work that has been laser-cut by the laser machining method according to Comparative Example 2. FIG. 9B is a photograph showing a part of the back surface of the work that has been laser-cut by the laser machining method according to Comparative Example 3. FIG. 10 is a diagram for explaining the laser processing method according to Comparative Example 3, and is a diagram showing the relationship between the cutting speed, the laser output, and the time.

Hereinafter, this embodiment will be described with reference to FIGS. 1 to 5. In the specification and claims of the present application, the "machining path" is a moving path of the irradiation position of the laser beam set in the machining program. In the specification of the present application, the "X-axis direction" is one of the horizontal directions indicated by arrows in the drawings, and is also referred to as a left-right direction. The "Y-axis direction" is one of the horizontal directions indicated by arrows in the drawing and is orthogonal to the X-axis direction, and is also referred to as a front-back direction. "And / or" means to include one or both of the two. In FIG. 1, "FF" indicates the forward direction, "FR" indicates the backward direction, "L" indicates the left direction, "R" indicates the right direction, "U" indicates the upward direction, and "D" indicates the downward direction. ..

As shown in FIGS. 1 and 2, the laser processing machine 10 according to the present embodiment is a processing machine that performs laser cutting processing on a plate-shaped work (sheet metal) K along a processing path SR. By the laser cutting process of irradiating the laser beam LB, the cut slit S of the two-dot chain line indicated by the width Sw is continuously formed in the work K. The laser processing machine 10 includes a processing table 12 that supports the work K, and a fiber laser oscillator 14 as a laser oscillator that oscillates (outputs) a laser beam (laser light) LB at a position separated from the processing table 12. Is provided. As the laser oscillator, a carbon dioxide gas laser oscillator, a YAG laser oscillator, a disk laser oscillator, a direct diode laser oscillator, or the like may be used instead of the fiber laser oscillator 14.

Above the processing table 12, a processing head 16 that irradiates the laser beam LB while injecting an assist gas toward the work K is provided via a support frame (not shown) or the like. The processing head 16 has a nozzle 18 at the tip thereof for irradiating the laser beam LB. The positions of the nozzle 18 in the X-axis direction and the Y-axis direction correspond to the irradiation positions of the laser beam LB. The machining head 16 is configured to be movable in the X-axis direction and the Y-axis direction with respect to the machining table 12. The processing head 16 is optically connected to the fiber laser oscillator 14. The processing head 16 is connected to an assist gas supply source (not shown) such as a gas cylinder that supplies the assist gas.

The laser machine 10 includes a head moving unit 20 that moves the machining head 16 in the X-axis direction and the Y-axis direction relative to the work K on the machining table 12. The head moving unit 20 has an X-axis motor 22 for moving the machining head 16 in the X-axis direction and a Y-axis motor 24 for moving the machining head 16 in the Y-axis direction. The moving speed of the machining head 16 in the X-axis direction and / or the Y-axis direction corresponds to the cutting speed (machining speed). Instead of the head moving unit 20 moving the machining head 16 in the X-axis direction and the Y-axis direction, the machining head 16 may be moved in the X-axis direction and the machining table 12 may be moved in the Y-axis direction.

According to the above configuration, the machining head 16 is moved in the X-axis direction and / or the Y-axis direction by driving the head moving portion 20. Then, the nozzle 18 of the machining head 16 can be positioned with respect to the work K supported by the machining table 12. Then, while positioning the nozzle 18 of the machining head 16, the laser beam LB is irradiated while injecting an assist gas from the nozzle 18 of the machining head 16 toward the work K, whereby desired laser cutting is performed on the work K. Perform processing.

The laser processing machine 10 includes a control device 26 that controls a fiber laser oscillator 14 and a head moving unit 20 based on a processing program. The control device 26 is composed of a computer, and has a memory for storing a machining program and the like, and a CPU (Central Processing Unit) for executing the machining program. The configuration of the characteristic portion of the control device 26 is as follows.

As shown in FIGS. 1 to 3, the control device 26 has a cutting speed until the irradiation position M of the laser beam LB reaches the front side of the tip (top) Ct of the corner portion C in the processing path SR in a predetermined case. (Machining speed) The head moving unit 20 is controlled so that V maintains a predetermined first speed V ₁ . The predetermined case is a case where oxygen is used as an assist gas and laser cutting is performed on a work K made of mild steel having a plate thickness of 12 mm or more along a processing path SR including a corner portion C. In the present embodiment, the predetermined first speed V ₁ is, for example, 15 mm / s. Further, the control device 26 cuts the laser beam LB during the irradiation position M from the predetermined position on the front side of the tip Ct of the corner portion C to the tip Ct of the corner portion C in the predetermined case. The head moving unit 20 is controlled so that the speed V gradually decelerates from a predetermined first speed V ₁ to zero. The predetermined position is a deceleration start position where the speed becomes zero at the tip Ct of the corner portion C when decelerating at a constant decelerating acceleration (acceleration at the time of deceleration). Note that T ₁ in FIG. 3 is the time when the irradiation position M of the laser beam LB reaches the tip Ct of the corner portion C.

In the predetermined case, the control device 26 has a cutting speed V from zero to a predetermined position while the irradiation position M of the laser beam LB is from the tip Ct of the corner portion C in the machining path SR to the predetermined position SRa in the vicinity thereof. The head moving unit 20 is controlled so as to gradually accelerate to a predetermined second speed V ₂ lower than the first speed V ₁ with acceleration (acceleration during acceleration). Then, the control device 26 controls the head moving unit 20 so as to maintain the predetermined second speed V ₂ . In the present embodiment, the predetermined second speed V ₂ is, for example, 0.83 mm / s. In the predetermined case, when the irradiation position M of the laser beam LB reaches the predetermined position SRb that maintains the predetermined _second speed V2 for a predetermined time from the predetermined position SRa of the processing path SR, the control device 26 reaches the cutting speed V. Controls the head moving unit 20 so as to gradually accelerate from a predetermined second speed V ₂ to a predetermined first speed V ₁ . The acceleration at this time is the same as the acceleration at the time of acceleration from the tip Ct of the corner portion C to the predetermined position SRa. Note that T ₂ in FIG. 3 is the time when the irradiation position M of the laser beam LB reaches the predetermined position SR b of the corner portion C.

Here, the control device 26 decelerates the cutting speed V (acceleration during deceleration) when the irradiation position M of the laser beam LB is from the front side of the tip Ct of the corner portion C to the tip Ct of the corner portion C. The absolute value of is set smaller than the absolute value of the acceleration (acceleration at the time of acceleration) for accelerating the cutting speed V between the irradiation position M of the laser beam LB from the tip Ct of the corner portion C to the predetermined position SRa. In the present embodiment, the absolute value of the acceleration during deceleration is smaller than the absolute value of the standard (normal) acceleration, for example, 20 mm / s ² . The absolute value of the acceleration during acceleration is the same as or similar to the absolute value of the standard acceleration, for example, 4900 mm / s ² . Normally, the absolute value of the acceleration during acceleration and the absolute value of the acceleration during deceleration are controlled to be the same, but in the present embodiment, the absolute values of the respective accelerations are significantly different. In FIG. 3, for comparison with the present embodiment, a two-dot chain line shows how the cutting speed V is decelerated at a standard acceleration. Since the absolute value of the acceleration to be decelerated is set smaller than the absolute value of the standard acceleration, the predetermined position for starting deceleration on the front side of the tip Ct of the corner portion C is on the front side.

Since the acceleration during acceleration has a positive value and the acceleration during deceleration has a negative value, in the present invention, the acceleration during acceleration and the acceleration during deceleration are compared, and either one is smaller, larger, or Regarding the description of the same or the same degree, it is assumed that the absolute values of the respective accelerations are compared.

In the predetermined case, the control device 26 maintains the laser output P at the predetermined first output P ₁ until the irradiation position M of the laser beam LB reaches the front side of the tip Ct of the corner portion C in the processing path SR. The fiber laser oscillator 14 is controlled in such a manner. In the present embodiment, the predetermined first output P ₁ is, for example, 5400 W (frequency 2000 Hz, duty ratio 90%). Further, in the control device 26, when the irradiation position M of the laser beam LB reaches the tip Ct of the corner portion C in the processing path SR, the laser output P becomes higher than the predetermined first output P ₁ to the predetermined first output P ₁ . The fiber laser oscillator 14 is controlled so as to switch to a lower predetermined second output P ₂ . Instead of switching from the predetermined first output P ₁ to the predetermined second output P ₂ , the laser output P may be switched to zero or once set to zero and then switched to the predetermined second output P ₂ .

In the present embodiment, the predetermined second output P ₂ is, for example, 1200 W (frequency 10 Hz, duty ratio 20%). The control device 26 is a fiber laser oscillator so that when the irradiation position M of the laser beam LB reaches a predetermined position SRb of the processing path SR, the laser output P is switched from the predetermined second output P ₂ to the predetermined first output P ₁ . 14 is controlled. When the laser output P is switched to zero instead of the predetermined second output P ₂ , the state of switching to zero is switched to the predetermined first output P ₁ .

Subsequently, the laser processing method according to the present embodiment will be described. The laser processing method according to the present embodiment is a method of performing laser cutting processing on the work K.

As shown in FIGS. 1 to 3, in the above-mentioned predetermined case, the control device 26 is the head moving portion 20 until the irradiation position M of the laser beam LB reaches the front side of the tip Ct of the corner portion C in the processing path SR. Is controlled to maintain the cutting speed V at a predetermined first speed V ₁ . Further, the control device 26 controls the fiber laser oscillator 14 to maintain the laser output P at a predetermined first output P ₁ .

Next, while the irradiation position M of the laser beam LB is from the front side of the tip Ct of the corner portion C in the machining path SR to the tip Ct of the corner portion C, the control device 26 controls the head moving portion 20 to cut. The speed V is gradually decelerated from a predetermined first speed V ₁ to zero at a predetermined acceleration (acceleration during deceleration). Then, while the irradiation position M of the laser beam LB reaches the predetermined position SRa from the tip Ct of the corner portion C in the machining path SR, the control device 26 controls the head moving portion 20 to reduce the cutting speed V from zero to a predetermined position. It gradually accelerates to the second speed V ₂ at a predetermined acceleration (acceleration at the time of acceleration) and maintains the speed V ₂ . Further, when the irradiation position M of the laser beam LB reaches the tip Ct of the corner portion C in the processing path SR, the control device 26 controls the fiber laser oscillator 14 to determine the laser output P from the predetermined first output P ₁ . Switch to the second output P ₂ of. Instead of switching the laser output P from the predetermined first output P ₁ to the predetermined second output P ₂ , it may be switched to zero or once set to zero and then switched to the predetermined second output P ₂ .

After that, when the irradiation position M of the laser beam LB reaches the predetermined position SRa of the processing path SR, the control device 26 controls the head moving unit 20 to set the cutting speed V from the predetermined second speed V ₂ to the predetermined first speed V 2. It gradually accelerates to the speed V ₁ with a predetermined acceleration (acceleration at the time of acceleration). Further, the control device 26 controls the fiber laser oscillator 14 to switch the laser output P from the predetermined second output P ₂ to the predetermined first output P ₁ . When the laser output P is switched to zero instead of the predetermined second output P ₂ , the laser output P is once switched to zero and then switched to the predetermined first output P ₁ .

Here, as described above, the acceleration at which the irradiation position M of the laser beam LB decelerates the cutting speed V from the front side of the tip Ct of the corner portion C to the tip Ct of the corner portion C (acceleration during deceleration). Is set to be smaller than the acceleration (acceleration at the time of acceleration) for accelerating the cutting speed V between the tip Ct of the corner portion C and the predetermined position SRa at the irradiation position M of the laser beam LB.

Subsequently, the action and effect of this embodiment will be described.

According to the configuration of the present embodiment, after the irradiation position M of the laser beam LB reaches the tip Ct of the corner portion C, the acceleration of the cutting speed V is kept at the same level as or the same as the standard acceleration of the laser beam LB. Only the acceleration for decelerating the cutting speed V (acceleration during deceleration) between the irradiation position M from the front side of the tip Ct of the corner portion C to the tip Ct of the corner portion C can be reduced. As a result, while suppressing excessive heat input to the work K when accelerating the cutting speed V, the locus of the molten metal on the back surface side of the work K with respect to the locus of the irradiation position of the laser beam LB (trajectory of the cutting position). ) Can be reduced.

Therefore, as shown in FIG. 4A, according to the present embodiment, when laser cutting is performed on the work K of a thick plate made of mild steel, the outer corner side of the corner portion C on the back surface of the work K and the outer angle side of the corner portion C By making the dent on the inner angle side sufficiently small, the processing quality of the work K is improved. As shown in FIG. 4B, according to the present embodiment, in the above case, the portion of the cut surface of the work K following the tip Ct of the corner portion C (see FIG. 4A) becomes rough. Can be suppressed.

Hereinafter, Examples and Comparative Examples will be described with reference to FIGS. 2, 5 to 10.

As shown in FIG. 2, the acceleration of the cutting speed V (acceleration during deceleration) between the irradiation position M of the laser beam LB from the front side of the tip Ct of the corner portion C to the tip Ct of the corner portion C is used as a parameter. A cutting test was performed on a work K made of mild steel and having a plate thickness of 22 mm. The predetermined first output P ₁ was set to 5400 W, and the predetermined second output P ₂ was set to 1200 W. Then, as a result of the cutting test, the relationship between the acceleration for decelerating the cutting speed V (acceleration during deceleration) and the amount of dents on the outer and inner corners of the corner portion C on the back surface of the work K can be summarized. It becomes as shown in 5. That is, it was found that the smaller the acceleration during deceleration, the smaller the amount of dent on the corner C side. Note that 4900 mm / s ² in FIG. 5 is a standard acceleration.

(Comparative Example 1)
As shown in FIGS. 2 and 6, the laser processing method according to Comparative Example 1 is a method for performing laser cutting processing on the work K, and has the same configuration as the laser processing method according to the present embodiment. There is. Of the configurations of the laser machining method according to Comparative Example 1, only the points different from the configurations of the laser machining method according to the present embodiment will be described.

The acceleration for accelerating the cutting speed V (acceleration during acceleration) is set to be the same as the acceleration for decelerating the cutting speed V (acceleration during deceleration). The acceleration for accelerating the cutting speed V and the acceleration for decelerating the cutting speed V are set smaller than the standard acceleration, respectively. In FIG. 6, for comparison with Comparative Example 1, a two-dot chain line shows how the cutting speed V is decelerated and accelerated at a standard acceleration.

According to the laser machining method according to Comparative Example 1, as shown in FIG. 7A, when laser cutting is performed on the work K of a thick plate made of mild steel in the same manner as the laser machining method according to the present embodiment. In addition, the dents on the outer corner side and the inner corner side of the corner portion C on the back surface of the work K can be sufficiently reduced. On the other hand, according to the laser machining method according to Comparative Example 1, as shown in FIG. 7 (b), a portion (one-dot chain line) following the tip Ct of the corner portion C on the cut surface of the work K (see FIG. 7 (a)). It was confirmed that the part surrounded by) became rough. It is considered that this is due to the excessive heat input to the work K when accelerating the cutting speed V.

(Comparative Example 2)
As shown in FIGS. 2 and 8, the laser processing method according to Comparative Example 2 is a method for performing laser cutting processing on the work K, and has the same configuration as the laser processing method according to the present embodiment. There is. Of the configurations of the laser machining method according to Comparative Example 2, only the points different from the configurations of the laser machining method according to the present embodiment will be described.

The acceleration for accelerating the cutting speed V (acceleration during acceleration) is set to be the same as the acceleration for decelerating the cutting speed V (acceleration during deceleration). The acceleration during acceleration and the acceleration during deceleration are set to be the same as or about the same as the standard acceleration, respectively.

Then, according to the laser processing method according to Comparative Example 2, as shown in FIG. 9A, it was confirmed that large dents were generated on the outer corner side and the inner corner side of the corner portion on the back surface of the work K. It is considered that this is due to the large delay in the locus of the molten metal (trajectory of the cutting position) on the back surface side of the work K with respect to the locus of the irradiation position of the laser beam LB (see FIG. 1).

(Comparative Example 3)
As shown in FIGS. 2 and 10, the laser processing method according to Comparative Example 3 is a method for performing laser cutting processing on the work K, and has the same configuration as the laser processing method according to Comparative Example 2. There is. Of the configurations of the laser machining method according to Comparative Example 3, only the points different from the configuration of the laser machining method according to Comparative Example 2 will be described.

After the irradiation position M of the laser beam LB reaches the tip Ct of the corner portion C in the processing path SR, the irradiation position M of the laser beam LB is stopped at the tip Ct of the corner portion C for a predetermined time Ta. Further, when the irradiation position M of the laser beam LB reaches the tip Ct of the corner portion C, the laser output P is lowered from the predetermined first output P ₁ to the predetermined first output P ₁ and is lower than the predetermined second output P ₂ Also switches to a high predetermined intermediate output Pa. After a predetermined time Ta elapses after the irradiation position M of the laser beam LB reaches the tip Ct of the corner portion C, the laser output P is switched from the predetermined intermediate output Pa to the predetermined first output P ₁ .

Then, according to the laser processing method according to Comparative Example 3, as shown in FIG. 9B, although the dent on the inner angle side of the corner portion C on the back surface of the work K can be reduced, the corner portion C on the back surface of the work K can be reduced. It was confirmed that the dent on the outer angle side became large. It is considered that this is because the heat input to the work K becomes excessive when the irradiation position M of the laser beam LB is stopped at the tip Ct of the corner portion C.

The present invention is not limited to the above description of the embodiment, and can be implemented in various embodiments by making appropriate changes. The scope of rights included in the present invention is not limited to the description of the above-described embodiment.

10 Laser Machining Machine 12 Machining Table 14 Fiber Laser Oscillator (Laser Oscillator)
16 Machining head 18 Nozzle 20 Head moving part 22 X-axis motor 24 Y-axis motor 26 Control device LB Laser beam K work (sheet metal)
S Cutting slit M Laser beam irradiation position SR Machining path SRa Predetermined location C Corner part Ct Tip of corner part

Claims (6)

It is a laser machining method that uses oxygen as an assist gas and performs laser cutting on a workpiece made of mild steel along a machining path including a corner portion.
While the irradiation position of the laser beam reaches the tip of the corner portion from the front side of the tip of the corner portion in the processing path, the cutting speed is reduced from a predetermined first speed to zero.
While the irradiation position of the laser beam reaches a predetermined position from the tip of the corner portion in the processing path, the cutting speed is accelerated to the predetermined first speed.
The acceleration that reduces the cutting speed while the laser beam irradiation position is from the front side of the tip of the corner portion to the tip of the corner portion is such that the irradiation position of the laser beam reaches the predetermined location from the tip of the corner portion. A laser machining method that is set to be smaller than the acceleration that accelerates the cutting speed in between. While the irradiation position of the laser beam reaches the predetermined position from the tip of the corner portion, the cutting speed is accelerated from zero to a predetermined second speed lower than the predetermined first speed to maintain the speed, and then the speed is maintained. The laser processing method according to claim 1, wherein the cutting speed is accelerated to the predetermined first speed. When the irradiation position of the laser beam reaches the tip of the corner portion of the processing path, the laser output is switched from the predetermined first output to a predetermined second output or zero lower than the predetermined first output, or once. After setting it to zero, switch to the predetermined second output,
When the irradiation position of the laser beam reaches the predetermined position of the processing path, the laser output is switched from the predetermined second output or zero to the predetermined first output, or once set to zero, the predetermined second output is performed. The laser processing method according to claim 2, which switches to one output. A laser oscillator that oscillates a laser beam and
A processing head that is optically connected to the laser oscillator and irradiates a laser beam while injecting oxygen as an assist gas toward a work made of mild steel.
A head moving portion that moves the processing head in a horizontal direction relative to the work,
A control device for controlling the laser oscillator and the head moving unit is provided.
The control device is
The head moving portion is controlled so that the cutting speed is reduced from a predetermined first speed to zero while the irradiation position of the laser beam reaches the tip of the corner portion from the front side of the tip of the corner portion in the processing path. ,
While the irradiation position of the laser beam reaches a predetermined position from the tip of the corner portion in the processing path, the head moving portion is controlled so that the cutting speed accelerates to the predetermined first speed.
The acceleration at which the laser beam irradiation position reduces the cutting speed between the front side of the tip of the corner portion and the tip of the corner portion, and the laser beam irradiation position reaches the predetermined location from the tip of the corner portion. A laser machine that sets the cutting speed smaller than the acceleration that accelerates the cutting speed. The control device is
While the irradiation position of the laser beam reaches the predetermined position from the tip of the corner portion, the cutting speed is accelerated from zero to a predetermined second speed lower than the predetermined first speed and maintained at the predetermined speed. The laser processing machine according to claim 4, wherein the head moving unit is controlled, and then the head moving unit is controlled so that the cutting speed accelerates from the predetermined second speed to the predetermined first speed. The control device is
When the irradiation position of the laser beam reaches the tip of the corner portion of the processing path, the laser output switches from the predetermined first output to a predetermined second output or zero lower than the predetermined first output, or once. The laser oscillator is controlled so as to switch to the predetermined second output after being set to zero.
When the irradiation position of the laser beam reaches the predetermined position of the processing path, the laser output is switched from the predetermined second output or zero to the predetermined first output, or is once set to zero and then the predetermined second output. The laser processing machine according to claim 5, wherein the laser oscillator is controlled so as to switch to one output.

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