JP3131357B2 - Laser processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method for cutting a workpiece by a laser beam, and is mainly used for forming a through hole as a starting point of a cut point at a predetermined position on the workpiece. The present invention relates to a laser processing method for removing molten metal generated near the opening of a through hole.

[0002]

2. Description of the Related Art In a piercing process for forming a through-hole (piercing hole) at a predetermined position of a workpiece, which is a starting point of a cutting portion, and performing a laser beam cutting process from the through-hole, generally a starting point is set. Piercing process to perform piercing to open through holes, and after this piercing process,
And a cutting step of cutting the through hole into an arbitrary shape. 2. Description of the Related Art Conventionally, in laser processing of a thick plate of carbon steel, stainless steel, or the like, during processing of a through hole in a piercing step, molten metal generated in a piercing process is deposited around the through hole on the surface of a workpiece. Therefore, during the cutting process after the piercing process, processing defects occur when cutting the metal portion where the molten metal is deposited,
The following method was used.

FIG. 9 is a block diagram showing a laser processing apparatus used in a conventional laser processing method disclosed in Japanese Patent Application Laid-Open No. 5-123885, for example. In the figure, reference numeral 1 denotes a laser oscillator which oscillates and emits a laser beam L, 2 denotes a mirror for guiding the laser beam L emitted from the laser oscillator 1, and 3 denotes a lens on which the laser beam L guided by the mirror 2 is incident. The processing heads 3 and 5 having the laser beam 4 irradiate (emit) the laser beam L condensed at the lower focal point by the lens 4 to process the workpiece W, and coaxially generate the assist gas A with the laser beam L. A nozzle which is a laser irradiating means for injecting the laser beam at the upper irradiation point, 6 is an assist gas supply device for supplying an assist gas A for accelerating melting by a laser beam L and removing molten metal, and 7 is a processing head 3 A servo control circuit that controls a plurality of axes in a plurality of directions, for example, in the X, Y, and Z directions along the processing path. And a gap sensor 9 for detecting the distance from the tip of the nozzle 5 to the surface of the workpiece W. The gap sensor 9 has a preset value of the gap amount at the time of laser processing based on the detection data detected by the gap sensor 8. The gap controller 10 that controls the height of the nozzle 5 so that the processing head 3 is moved in the Z-axis direction, that is, the optical axis direction of the processing head 3 via the servo control circuit 7, so that the tip of the nozzle 5 and the workpiece W
The NC device controls the distance to the surface of the laser beam and controls the output value of the laser beam L output from the laser oscillator 1 by the laser oscillation control circuit 11. This is a laser oscillation control circuit that controls a value.

In FIG. 1, a laser beam L emitted from a laser oscillator 1 is guided by a mirror or the like and is incident on a processing lens 4 of a processing head 3. The laser beam L is condensed by the lens 4 at an outward focus of a nozzle 5. You. The processing head 3 is supplied with an assist gas A from the assist gas supply device 6.
Is ejected from the nozzle 5 to the irradiation point of the laser beam coaxial with the laser beam L, and the workpiece W is processed. The machining head 3 is controlled by the servo control circuit 7 along a machining path, for example, in a plurality of axes in X, Y, and Z directions.
At the same time, the distance from the tip of the nozzle 5 to the surface of the workpiece W, that is, the gap amount is detected by the nozzle 5 or the gap sensor 8 provided in the vicinity of the nozzle 5, and the gap controller is determined based on the detected data. 9 controls the height of the nozzle 5 so that the gap amount during processing becomes a predetermined amount.

Further, when piercing is performed on the workpiece W, the NC device 10 moves the processing head 3 through the servo control circuit 7 in the Z axis direction, that is, the optical axis direction, so that the tip of the nozzle 5 is moved. The gap amount between the workpiece W and the surface of the workpiece W is controlled. (See FIG. 10A.) At the same time, the laser processing is performed as follows while the output value of the laser beam L output from the laser oscillator 1 is controlled by the laser oscillation control circuit 11.

FIG. 10 is a conceptual diagram for removing molten metal deposited on the material surface. FIG. 11A shows the height of the Z axis (height of the focal point), and FIG. 11B shows the laser oscillation output. , FIG.
FIG. 1 (c) is a diagram showing a relationship between assist gas pressures. In the laser processing method for cutting the workpiece W with the laser beam L, at the start of piercing, the processing head 3 is set at a predetermined height position as shown by the chain line in FIG. 10 and FIG. A through hole h is formed in the workpiece W. After the through hole h is formed, the processing head 3 is moved to the position shown in FIG.
11B, the laser oscillator 1 is instantaneously moved upward by a predetermined height as shown by the solid line, and the output of the laser oscillator 1 is made lower than that at the time of piercing as shown in FIG. 11B, and as shown in FIG. The pressure of the assist gas A supplied from the assist gas supply device 6 is set higher than at the time of piercing, and the processing head 3 is gradually lowered as shown in FIG. Due to the strong pressure of the assist gas A injected from the processing head 3 at the highest position, the molten metal in the molten state attached to the vicinity of the opening of the through hole h of the workpiece W is scattered outward and removed. Thereafter, the processing head 3 is stopped at the cutting height position, and in this state, the processing shifts to cutting of the workpiece W.

[0007]

Generally, the laser beam absorptance of a metal material is a relational diagram showing the temperature dependence of the absorptance of various metals at 10.6 μm calculated by free electron theory in FIG. Processing Technology Manual: Welding Association)
As shown in (1), the temperature largely depends on the temperature of the metal material irradiated with the laser beam L. For example, in the characteristics of Fe, 1
At 00 ゜ K, the absorption rate is about 0.01,
At 0 ゜ K, it reaches 0.12, and when further melting occurs, it reaches 0.92.
Reach Further, between the focal position and the energy density of the portion of the workpiece surface irradiated with the laser beam L,
As the focus of the laser beam L on the workpiece is blurred, the irradiation area of the laser beam L is increased, and the energy density is reduced.

Therefore, from the characteristics of the workpiece W and the laser beam L to be irradiated, the irradiation of the laser beam L is stopped after the conventional piercing is completed, the processing head 3 is raised, and the processing head 3 is irradiated with the laser beam L. In the conventional processing method of lowering the focus, the relationship between the focal point of the laser beam L and the focus of the workpiece W is as shown in FIG. Processing head 3
From the state where the laser beam L has risen to the predetermined height position (FIG. 13A), the processing head 3 is gradually lowered while irradiating the molten metal near the opening of the through hole h on the surface of the workpiece W. (FIGS. 13B and 13C), the energy density with respect to the molten metal gradually increases, and the absorption and melting of the laser beam L are promoted.

As a result, the molten metal near the opening of the through hole h on the surface of the workpiece W is excessively molten, and the excessively molten metal explosively expands the through hole h.
For this reason, there has been a case where the workpiece W cannot be cut satisfactorily and a high-quality finished product of the workpiece cannot be obtained. In addition, abnormal combustion may be induced by the expansion of the through hole h, and spatters, which are granular molten metal, may be ejected upward from the periphery of the through hole h of the workpiece W and adhere to the nozzle 5. In some cases, the irradiation of the laser beam L from the nozzle 5 and the injection of the assist gas A are hindered. Further, there is a case where the molten metal cannot be scattered and removed only by the injection of the assist gas A coaxial with the laser beam L.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a first object is to provide a cutting process for cutting a workpiece from a piercing process for forming a through hole in the workpiece. The present invention is to provide a laser processing method capable of removing molten metal deposited near the opening of a through hole on the surface of a workpiece without excessive melting when the process shifts to. Another object of the present invention is to provide a laser processing method capable of preventing spatter generated at the time of removing molten metal from adhering to a nozzle. Still another object of the present invention is to provide a laser processing method capable of reliably scattering and removing the molten metal when removing the molten metal.

[0011]

In a laser processing method according to the present invention, a workpiece is irradiated with a laser beam,
A first step of forming a through hole at the predetermined location;
A second step of irradiating the laser beam to the molten metal generated in the vicinity of the through hole opening by the step while gradually expanding the beam diameter, and injecting the assist gas to an irradiation point of the laser beam; After the second step, a third step of stopping irradiation and injection of the laser beam and the assist gas, and after the third step, irradiation and injection of the laser beam and the assist gas again to cause the workpiece to A fourth step of cutting from the position of the through hole;
It is provided with.

In the second step, the irradiation means for irradiating the workpiece with the laser beam is raised, and the beam diameter is gradually enlarged by raising the focal position of the laser beam accordingly.

Further, in the second step, the side gas is injected to the laser irradiation point from an axial direction different from the injection axis of the assist gas.

[0014]

In the laser processing method configured as described above, after a through hole is formed in a predetermined portion of the workpiece by piercing, the focus of the laser beam is shifted from above the workpiece and the beam diameter is gradually enlarged. While reducing the energy density of the laser beam to the molten metal generated near the opening of the through hole of the workpiece, the laser beam continues to be irradiated, and the assist gas is applied to the laser beam irradiation point of the workpiece. Since the injection is continued, the unnecessary molten metal in the vicinity of the opening of the through hole is melted to such an extent that excessive melting does not occur, whereby the bonding force is reduced and the metal can be scattered and removed by the assist gas.

Further, by raising the laser irradiating means by the elevating means while irradiating the laser beam and shifting the focal position of the laser beam from the through hole, unnecessary molten metal generated near the opening of the through hole is excessively melted. And the distance of the laser irradiating means from the molten metal is gradually increased, so that obstacles to the laser irradiating means due to the scattering of the molten metal can be reduced.

Further, even for the molten metal which cannot be scattered and removed only by the assist gas, the assist gas is injected coaxially with the laser beam, and the side gas is injected from an axial direction different from the assist gas injection axis. In addition, gas is injected from multiple directions to the molten metal on the workpiece, and can be reliably scattered and removed.

[0017]

【Example】

Embodiment 1 FIG. FIG. 1 shows a height (a) of a processing head 3 in a Z-axis direction, a laser oscillation output (b) of a laser oscillator 1, and an assist gas supply device for illustrating a laser processing method according to an embodiment of the present invention. FIG. 6 is a relationship diagram showing a relationship of a pressure (c) of an assist gas A of No. 6; With reference to FIG. 1, a detailed description will be given focusing on the operation related to the removal of the molten metal in the laser processing apparatus (see FIG. 9) configured similarly to the conventional one. In the figure, the workpiece W is irradiated with a laser beam L, and the formation of the through hole h of “b” is completed from the start of the piercing step of “a”, which is the first step of forming the through hole h at a predetermined location. In the piercing process up to the end of piercing,
From the setting of conditions for shortening the piercing time required for drilling the through hole h (piercing hole) and preventing the occurrence of machining failure due to abnormal combustion, the height of the machining head 3 in the Z-axis direction, the laser oscillation of the laser oscillator 1 The through-hole h is formed in the workpiece W by controlling the output and the assist gas pressure from the assist gas supply device 6 to be constant.

In the piercing step, the second step from the point "b" where the through hole h is formed to the point "c" where the scattered removal of the molten metal in the vicinity of the opening of the through hole h is completed is described in the second step. The molten metal generated in the vicinity of the opening of the through hole h by one process is irradiated with the laser beam L while gradually expanding the beam diameter, and is shown in the figure for a predetermined time t1 during which the assist gas A is injected. As described above, the processing head 3 is gradually moved upward by a predetermined height, and the laser oscillation output of the laser oscillator 1 is adjusted so as to remain at the output value at the end of the piercing processing. Note that the pressure of the assist gas A supplied from the assist gas supply device 6 is also adjusted to be the same pressure as at the end of the piercing processing. During this time, during the piercing process, the molten metal deposited (adhered) near the opening of the through hole h of the workpiece W is melted by the laser beam L and completely removed by the injection of the assist gas A. .

Thereafter, at the point "c" when the scattered removal of the molten metal in the vicinity of the opening of the through hole h is completed, as a third step, the laser oscillation output of the laser oscillator 1 and the assist gas A from the assist gas supply device 6 are processed. Is stopped, and the processing head 3 is gradually lowered to a position suitable for the cutting process in the cutting process. (Refer to FIG. 1 (a).) At the point of "d" when the lowering of the processing head 3 is completed,
During the period of the predetermined time t2 up to the point of "e", the pressure of the assist gas A from the assist gas supply device 6 is increased without performing the laser oscillation from the laser oscillator 1 and the piercing process pressure during the piercing process and the cutting process. The pressure is made higher than the assist gas pressure at the time, and the gas is injected into the through hole h. This strong pressure assist gas A removes the oxidized metal present inside the through hole h, lowers the temperature around the through hole h, reduces the incidence of defects in the cutting process, and ends the piercing process. I do. Then, when the point of time “e” is reached, the process shifts to the cutting step, which is the fourth step, so that the height of the processing head 3 in the Z-axis direction, the laser oscillation output of the laser oscillator 1 and the assist gas supply device 6 The assist gas pressure is set as a predetermined value required for the cutting process, and irradiation and injection are performed again to perform the cutting process.

Next, the removal of scattered molten metal will be described using actual numerical values. Change the material of the workpiece W to “SS40
0 ", plate thickness" 12mm ", through hole h" 0.8mm "
, The piercing in FIG.
In the case of “b”), the laser output is set to “700 W” and the assist gas pressure is set to “0.2 kg / cm ² ”. By setting the laser output and the assist gas pressure as described above, the workpiece W having a thickness of “12 mm” has a diameter of “0.8 m”.
Then, in the blow-off step (“B” to “C”) in the drawing, the machining head 3 is moved in the Z-axis direction at a rising speed of “10 m / min”.
0 mm ”, and at the same time, keep outputting the laser output and the assist gas pressure at a constant level. As a result, the molten metal deposited near the opening of the through hole h of the workpiece W is not excessively melted. Scattering can be removed.

When the scattered removal of the molten metal is completed, the processing head 3 is moved to a predetermined height for performing the cutting step ("C" to "D"), and then the assist gas of "2 kg / cm ² " is used. A is injected into the through-hole h for about 1 second ("d" to "e"), and the piercing step is completed. Then, the laser output of the laser beam L is set to “1800 W”,
Set the assist gas pressure of the assist gas A to "0.4 to 0.5k
g / cm ² ″, and the process proceeds to the cutting process.

Next, the diameter of the laser beam L will be described with reference to a relationship diagram showing the relationship between the height of the processing head 3 in the Z-axis direction and the focal point of the laser beam L in FIG. In the piercing process (at points “A” to “B” in FIG. 1), the focal point of the laser beam L irradiates the workpiece W to form the through hole h. (See FIG. 2A) Thereafter, the focus of the laser beam L directly irradiates the workpiece W until the process shifts from the piercing to the cutting process (at points “B” to “C” in FIG. 1). Instead, the out-of-focus laser beam L irradiates the molten metal near the opening of the through hole h of the workpiece W while gradually increasing the laser beam diameter. (See FIGS. 2A and 2B.) Since the energy density due to the irradiation of the laser beam L decreases with the elevation of the processing head 3, the molten metal near the opening of the through hole h of the workpiece W has The absorption of the laser beam is reduced, and excessive melting due to the irradiation of the laser beam L does not occur. Sputtering does not occur. The swelling of the molten metal near the opening of the through hole h can be scattered and removed.

For example, FIG. 3 shows the conventional method and the processing method of the present invention described above under the conditions shown in FIG.
FIG. 4 is a comparison diagram showing a rate of occurrence of processing defects when a workpiece W is pierced 100 times for each plate thickness, that is, a processing defect rate. As shown in the figure, when the plate thickness is 9 mm or less, there is no difference between the conventional method and the present embodiment, and both are good. However, when the plate thickness is 9 mm or more, the processing failure rate in the conventional method tends to increase significantly. However, in the method according to the present invention, the failure rate is only slightly increased. Thickness 22
Even with mm, the processing failure rate is about 7.5%.

According to the method of the present embodiment described above, excessive melting of the molten metal around the through hole h on the surface of the workpiece W is prevented,
The generation of spatter can be suppressed without inducing abnormal combustion, the swelling of the molten metal can be easily removed in a short time, and processing defects can be suppressed without being affected by the sheet thickness. Further, since the molten metal around the through-hole h on the surface of the workpiece W is reliably removed, the gap sensor 8 provided near the processing head 3 is provided between the workpiece W and the processing head 3. Can be detected accurately, the workpiece W can be cut smoothly under stable gap control, and the processing accuracy is improved. Further, since the molten metal is scattered and removed while ascending, the position of the molten metal and the position of the processing head 3 gradually move away from each other. Never do.

The height of the processing head 3 in the Z-axis direction, the laser oscillation output of the laser oscillator 1,
The relationship between the piercing step of the assist gas pressure from the assist gas supply device 6 and the conditions of the cutting step has various patterns depending on the material and the plate thickness of the workpiece W. In the present embodiment, an example is shown. The laser beam output and the assist gas pressure may be increased or decreased depending on the processing state of the workpiece W to be processed. Further, the high pressure condition of the assist gas A before the cutting process after the piercing process may be possible even under the low pressure condition depending on the material and the plate thickness of the workpiece W.

Embodiment 2 FIG. In the present embodiment, in order to be able to instantaneously melt and discharge the workpiece W in the through-hole h over a wide range during the piercing process as the first step (at points “A” to “B” in FIG. 5). 5 (a), (b),
(C) the height of the processing head 3 in the Z-axis direction,
This is another embodiment showing a case where the laser oscillation output of the laser oscillator 1 and the assist gas pressure from the assist gas supply device 6 are controlled.
1 to 2), compared to the first embodiment, the laser oscillator 1 has a large laser oscillation output (actually, 2000 W) for processing the workpiece W at once, and the assist gas pressure from the assist gas supply device 6. Is set to a high pressure condition in order to make the oxidation reaction proceed at a stretch.

Since the laser output is large and the assist gas pressure is high, the through-hole h
However, it can be formed quickly with a large diameter (actually 3 mm) which is equal to or larger than the diameter (0.8 mm) of the through hole h shown in the first embodiment. After the through hole h is formed, the processing head 3 is moved upward by a predetermined height as shown in FIG. 5B, the laser oscillation output is changed to an output smaller than the output value at the end of the piercing, as shown in FIG. 5B, the irradiation is continued for a predetermined time t3, and the laser oscillation output is supplied from the assist gas supply device 6. As shown in FIG. 5C, the pressure of the assist gas A continues to be injected for a predetermined time t3 at the same pressure as in the piercing step. For this reason, during the period from "B" to "C", the molten metal attached to the vicinity of the surface of the piercing hole of the workpiece W in the piercing is melted by the laser beam L and completely removed by the injection of the assist gas. Is done.

Then, at the point of time "c" when the removal of the molten metal near the surface of the piercing hole is completed, the laser oscillation output of the laser oscillator 1 and the supply of the assist gas A from the assist gas supply device 6 are stopped as a third step. And processing head 3
Is gradually lowered to a position suitable for the cutting process in the cutting process. (Refer to FIG. 5 (a).) At the time "d" when the lowering of the processing head 3 is completed,
During the period of the predetermined time t4 up to the point of "e", the pressure of the assist gas A from the assist gas supply device 6 is set higher than the piercing processing pressure in the piercing step without performing laser oscillation from the laser oscillator 1. Then, it is injected into the through hole h. This strong pressure assist gas A removes the oxidized metal present in the through hole h, lowers the temperature around the through hole h, and reduces the defect occurrence rate when shifting from the piercing process to the cutting process. Let it. And
When the fourth step “e” is reached, the processing shifts to the cutting step, so that the height of the processing head 3 in the Z-axis direction, the laser oscillation output of the laser oscillator 1, and the assist from the assist gas supply device 6 Cutting is performed with the gas A pressure as a predetermined value required for cutting.

In this embodiment, a through hole having a large diameter can be obtained in a short time, and the swelling of the molten metal in the vicinity of the opening of the through hole h on the surface of the workpiece W is eliminated by the excessive melting of the molten metal. It can be easily performed in a short time while suppressing generation of spatters, and does not induce processing defects. Further, since the molten metal in the vicinity of the opening of the through hole h on the surface of the workpiece W is reliably removed, the gap sensor 8 provided in the vicinity of the processing head 3 makes the gap between the workpiece W and the processing head 3 Can be detected accurately, the workpiece W can be cut smoothly under stable gap control, and machining accuracy is improved.

As the piercing condition, a condition that allows the workpiece to penetrate the workpiece at once is used, but for that purpose, CW (continuous wave) and pulse are not distinguished.
In this example, the laser oscillation output was shown to be the same as the piercing step for removing the molten metal.However, in the case of a material in which the adhesion of the molten metal was strong, the laser oscillation output was increased and the adhesive force was weak. May reduce the laser oscillation output. Further, the assist gas pressure may be set in the same manner in accordance with the adhesive force of the molten metal.

Embodiment 3 FIG. In the present embodiment, the output time T of the laser beam L output from the processing head 3 when the process shifts from the piercing process to the cutting process using the parameter indicating the height of the Z axis in FIG. Laser beam L
The output time T is a time t during which the processing head 3 is raised in order to irradiate the laser beam L onto the molten metal in the through hole h in an enlarged manner, and the processing head 3 is held at a predetermined height, and h is determined from the residence time Δt for promoting the melting of the molten metal in the vicinity of the opening.

In general, the speed at which the machining head 3 is raised (for example, at times “b” to “c” in FIG. 5) is determined by the NC control device 10 via the servo control circuit 7, and Since the upward movement amount is determined in advance in relation to the enlarged irradiation of the laser beam L, the time t for raising the processing head 3 is determined. During the time t for raising the processing head, first, the laser beam L
From the state where the energy density of the beam irradiating portion where the molten metal directly irradiates the molten metal near the opening of the through-hole h is high, the focal point of the laser beam L is changed to the melting near the opening of the through-hole h as the working head 3 is raised. No longer directly irradiates metal,
Displaced into a state where the energy density of the beam irradiation part is low.

When the focus of the laser beam L is directly applied to the molten metal near the opening of the through hole h, the molten metal near the opening of the through hole h is instantaneously melted. Once melting occurs, the beam absorptivity increases, so the processing head 3
Therefore, even if the energy density of the beam irradiating part is lowered due to the rise of the temperature, the molten metal in the vicinity of the opening of the through-hole h can sufficiently be melted continuously.

In this embodiment, by the above-described operation,
Since the molten metal in the vicinity of the opening of the through-hole h can be continuously melted while the processing head 3 is being raised, the processing head 3 is necessarily held at a predetermined height in a state where the processing head 3 is raised. It is not necessary to take a residence time Δt for promoting the melting of the molten metal in the vicinity of the portion, and Δt may be set to 0. Therefore, the transition from the piercing process to the cutting process can be performed quickly, and the productivity is improved.

Embodiment 4 FIG. In the above-described embodiment, the assist gas A supplied from the assist gas supply device 6 is injected from the nozzle 5 coaxially with the laser beam L as in the conventional device. As shown in the figure, the side nozzle 12 provided near the nozzle 5
The side gas B during the piercing step and through hole h
You may make it inject | pour at the process of blowing off molten metal near an opening. Here, it goes without saying that conditions such as the pressure of the side gas B, the injection start time, and the stop time are controlled by the NC control device 10.

FIG. 8 shows a laser processing apparatus according to an embodiment of the present invention, in which the height (a) of the processing head 3 in the Z-axis direction, the laser oscillation output (b) of the laser oscillator 1, and the assist gas supply apparatus. 6 is a relationship diagram showing the relationship between the pressure (c) of the assist gas A and the side gas pressure (d) of the side gas B ejected from the side nozzle 12 in FIG. In the figure,
From the start of the piercing process of “A”, which is the first step, to the end of the piercing process of “B”, conditions for shortening the piercing time required for drilling the through-hole h and preventing the occurrence of processing defects due to abnormal combustion. From the settings, the height of the processing head 3 in the Z-axis direction, the laser oscillation output of the laser oscillator 1, and the assist gas pressure from the assist gas supply device 6 are controlled to be constant, and a through hole h is formed in the workpiece W. I do. Further, in the present embodiment, the side gas B is also injected from the side nozzle 12 to remove the molten metal near the opening of the through hole h which could not be completely scattered and removed by the assist gas A coaxial with the laser beam L. Remove and scatter.

In the piercing step, as shown in the drawing, the processing head 3 is gradually moved for a predetermined time t5 in the second step from the point "B" where the through hole h is formed to the point "C". Then, the laser oscillation output of the laser oscillator 1 is changed to an output smaller than the output value at the end of the piercing processing, as shown in FIG.
The irradiation is continued for 5 hours, and the pressure of the assist gas A supplied from the assist gas supply device 6 is adjusted to be the same as the pressure at the end of the piercing process. Further, the side gas B continues to be jetted from the side nozzle 12 in the same manner as in the piercing process. When the assist gas A and the side gas B are injected into the molten metal near the opening of the through hole h, the through hole h of the workpiece W is formed at the time of piercing.
The molten metal deposited (adhered) in the vicinity of the opening is melted by the laser beam L and completely scattered and removed by the injection of the assist gas A and the side gas B.

Thereafter, at the point of time "c" at which the scattered removal of the molten metal near the opening of the through hole h is completed, as a third step, the laser oscillation output of the laser oscillator 1 and the assist gas A from the assist gas supply device 6 are processed. And the side nozzle 12
The supply and injection of the side gas B from are stopped, and the processing head 3 is gradually lowered to a position suitable for the cutting process in the cutting process. (See FIG. 8 (a).) At the point of “d” when the lowering of the processing head 3 is completed,
During the period of the predetermined time t6 up to the point of "e", the pressure of the assist gas A from the assist gas supply device 6 is increased without performing the laser oscillation from the laser oscillator 1 and the piercing pressure during the piercing process and the cutting process. The pressure is made higher than the assist gas pressure at the time, and the gas is injected into the through hole h. This strong pressure assist gas A removes the oxidized metal present inside the through hole h, lowers the temperature around the through hole h, reduces the incidence of defects in the cutting process, and ends the piercing process. I do. Further, the high pressure condition of the assist gas before cutting may be possible even under the low pressure condition depending on the material and the thickness of the workpiece. Then, when reaching the time point of “e” which is the fourth step, the processing is shifted to the cutting step, so that the height of the processing head 3 in the Z-axis direction, the laser oscillation output of the laser oscillator 1 and the assist gas supply device 6 The cutting process is performed by setting the assist gas pressure at a predetermined value required for the cutting process.

In this embodiment, in addition to the effect similar to the second embodiment, the strong gas pressure (for example, 2 kg /
cm ² ), the swelling of the molten metal in the vicinity of the opening of the through hole h on the surface of the workpiece W can be more reliably removed while suppressing generation of spatter due to excessive melting of the molten metal. . Therefore, the gap sensor 8 provided in the vicinity of the processing head 3 can detect an accurate gap between the workpiece W and the processing head 3, and the workpiece W can be detected under stable gap control.
Is performed smoothly, and the processing accuracy is improved.

The Z-axis height, laser oscillation output, assist gas pressure, and side gas pressure shown in the above-described embodiments have various patterns depending on the material and plate thickness of the workpiece. This is just one example. Further, the high pressure condition of the assist gas before cutting may be possible even under the low pressure condition depending on the material and the thickness of the workpiece. Further, in some cases, the molten metal adhered to the vicinity of the through hole h of the workpiece W can be removed only by injecting the side gas B. In this case, the piercing step is performed without the process of raising the Z axis. Only the injection of the gas B may be performed.

Embodiment 5 FIG. In the above-described embodiment, in the second step after the piercing, the processing head 3 is moved to a predetermined height by the elevating means while outputting the laser beam L, and the piercing is performed by the injection of the assist gas A. The laser beam L is expanded and irradiated to the hole h,
Although the configuration has been described in which molten metal is scattered and removed while preventing excessive melting, if a focusing function is added to the lens 4 so that the focal position of the lens 4 can be set variably, the position of the processing head is raised by the elevating means. This eliminates the need to perform the operation, and it is possible to eliminate unnecessary lifting and lowering of the processing head 3 with respect to the workpiece W, thereby further improving productivity.

[0042]

Since the present invention is configured as described above, it has the following effects. A first step of irradiating the workpiece with a laser beam and forming a through hole at a predetermined position thereof; and applying the laser beam to the molten metal generated in the vicinity of the through hole opening in the first step. A second method of irradiating the laser beam while gradually expanding it and injecting the assist gas to an irradiation point of the laser beam.
And a third step of stopping irradiation and injection of the laser beam and the assist gas after the second step, and irradiating and jetting the laser beam and the assist gas again after the third step, And a fourth step of cutting the workpiece from the position of the through hole, so that when the process shifts from the first step of forming the through hole in the workpiece to the fourth step of cutting the workpiece, Unnecessary molten metal deposited near the opening of the through hole on the surface of the workpiece can be reliably removed without excessive melting, and the expansion of the through hole due to the excessively molten metal can be prevented. for that reason,
The workpiece can be cut well, the occurrence of defects can be reduced, and a high quality finished product can be obtained.

In the second step, the irradiating means for irradiating the workpiece with the laser beam is raised, and the beam diameter is gradually increased by raising the focal position of the laser beam. When performing, the scattered molten metal can be prevented from adhering to the irradiation means.

Further, in the second step, since the side gas is injected to the laser irradiation point from an axial direction different from the injection axis of the assist gas, the molten metal on the workpiece is injected from a variety of directions to ensure the injection of the gas. Scattering can be removed.

[Brief description of the drawings]

FIG. 1 is a relationship diagram showing a relationship among a height of a Z-axis, a laser output, and an assist gas pressure in an electric discharge machine according to an embodiment of the present invention.

FIG. 2 is a relationship diagram showing the relationship between the height of a processing head and the focal point of a laser beam L according to the present invention.

FIG. 3 is a comparison diagram showing the processing failure occurrence rates of the present invention and the conventional apparatus.

FIG. 4 is a condition diagram showing conditions for obtaining a processing defect occurrence rate of the present invention and the conventional apparatus.

FIG. 5 is a relationship diagram showing a relationship among a height of a Z-axis, a laser output, and an assist gas pressure in the electric discharge machine according to the second embodiment of the present invention.

FIG. 6 is a diagram showing parameters of a Z-axis height of a processing head.

FIG. 7 is a configuration diagram illustrating a configuration of a laser processing apparatus that is Embodiment 4 of the present invention.

FIG. 8 is a relationship diagram showing a relationship among a height of a Z-axis, a laser output, and an assist gas pressure in an electric discharge machine according to a fourth embodiment of the present invention.

FIG. 9 is a configuration diagram showing a configuration of a conventional laser processing apparatus.

FIG. 10 is a conceptual diagram for removing a conventional molten metal (sputter).

FIG. 11 shows the height of the Z-axis in a conventional electric discharge machine,
FIG. 4 is a relationship diagram showing a relationship between a laser output and an assist gas pressure.

FIG. 12 is a relationship diagram showing the temperature dependence of the absorptivity of various metals at 10.6 μm.

FIG. 13 is a relationship diagram showing a relationship between a height of a conventional processing head in a Z-axis direction and a focal point of a laser beam.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Laser oscillator 3 Processing head 6 Assist gas supply device 7 Servo control circuit 10 NC device 11 Laser oscillator control circuit 12 Side nozzle

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-57469 (JP, A) JP-A-5-123885 (JP, A) Jiko 3-27752 (JP, Y2) (58) Field (Int.Cl. ⁷ , DB name) B23K 26/14 B23K 26/00 B23K 26/04

Claims (3)

(57) [Claims] A first step of irradiating a workpiece with a laser beam to form a through-hole at a predetermined position thereof; and applying a laser beam to the molten metal generated in the vicinity of the through-hole opening in the first step. A second step of irradiating the beam while gradually expanding the beam diameter and injecting the assist gas to an irradiation point of the laser beam; and, after the second step, irradiating and ejecting the laser beam and the assist gas. A third step of stopping, and after the third step, a fourth step of irradiating and jetting the laser beam and the assist gas again and cutting the workpiece from the position of the through hole. A laser processing method characterized by the above-mentioned. 2. The method according to claim 1, wherein in the second step, the irradiation means for irradiating the workpiece with the laser beam is raised, and the beam diameter is gradually increased by raising the focal position of the laser beam accordingly. 2. The laser processing method according to claim 1. 3. The laser processing method according to claim 1, wherein in the second step, a side gas is injected to a laser irradiation point from an axial direction different from an injection axis of the assist gas.