JPH04200891A - Laser piercing method and device therefor - Google Patents

Abstract

PURPOSE:To smooth an operation by specifying a nozzle piercing height and a laser condensing position in a laser piercing operation, carrying out piercing and then returning the nozzle to the cutting height. CONSTITUTION:In the laser piercing wherein a material W to be machined is irradiated with condensed laser beam through the nozzle N and pierced as assistant gas is injected, the piercing operation is performed by setting the height of the nozzle N to the piercing height larger than the height in the time of cutting and the laser beam condensing position to a position in the time of cutting. After the piercing operation is completed, the nozzle N is returned to the height in the time of cutting. Hereby, fume of vaporized metal generated from the material W to be machined, molten metal and molten oxide, etc., can be prevented from sticking to a lens and the nozzle and the operation can be executed smoothly.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention irradiates a workpiece with a focused laser beam, and injects assist gas along the laser beam to remove the surface of the workpiece from the surface of the workpiece. The present invention relates to a laser piercing method and device for drilling a hole penetrating the back surface.

<Prior art> Plywood 1 A workpiece such as a synthetic resin plate, metal plate, or ceramic plate is irradiated with a focused laser beam from a nozzle spaced a predetermined distance from the surface of the workpiece. 2. Description of the Related Art A so-called laser processing method is widely used in which processes such as piercing, cutting, welding, and scribing are performed on a workpiece by injecting assist gas along the laser beam.

When cutting a metal plate, it is rare to start cutting from the end face of the workpiece, and the workpiece may deform due to heat.
Deformation due to positional deviation or release of internal stress in the workpiece 1
In order to prevent misalignment, cutting is generally started from the surface of the workpiece. In this way, when starting cutting from the surface of the workpiece, it is necessary to perform an operation called piercing in order to form a hole that penetrates from the front surface to the back surface of the workpiece.

The case of piercing a metal plate using the laser processing method is as follows.

In other words, the distance between the surface of the workpiece and the lower end surface of the nozzle (hereinafter referred to as "
The nozzle height j) is set to a predetermined value, and the position of the focal point of the focused laser beam (hereinafter referred to as "focal point J") is set to a predetermined position in the thickness direction of the workpiece. In this state, a laser beam is irradiated from the nozzle toward the workpiece, and assist gas is injected along the laser beam.

Here, when piercing the workpiece material,
Generally, the nozzle height is set to one height, the focal point is set near the surface of the workpiece, and oxygen gas is used as the assist gas.

The base material near the surface of the workpiece irradiated with the laser beam instantly melts and a portion of it vaporizes. At this time, the molten metal reacts with the oxygen gas injected from the nozzle and burns, while the momentum of the assist gas transforms the molten metal into molten metal particles, resolidified metal particles, and metal oxide particles (hereinafter collectively referred to as "spatter"). As a result, small depressions are formed on the surface of the workpiece.

The laser beam that is continuously irradiated to the hollow is repeatedly reflected on the side surfaces of the hollow, reaches the deepest part, and heats and melts the core again. Then, the base material melts, vaporizes, and burns, and the spatter is removed from the recessed opening.

By continuously repeating the above phenomenon, a hole penetrating from the front surface to the back surface of the workpiece is formed, and the piercing is completed.

<Problems to be Solved by the Invention> When performing laser piercing as in the above technology, as the piercing progresses, the metal base material removed from the workpiece inevitably becomes spatter and scatters upward. Occurs on. Therefore, unlike the conventional technology, the nozzle height is reduced to approximately 1
If it is installed in a cylinder, scattered spatter may adhere to the nozzle or may enter the inside of the nozzle and adhere to the light condensing part.

If spatter adheres to the nozzle, there is a problem that this spatter will interfere with the laser beam and cause turbulence in the assist gas flow.Also, if spatter adheres to the light condensing part, this spatter will interfere with the laser beam. There is a problem in that it causes diffraction of light or causes a local temperature increase in the light focusing component, changing the light focusing characteristics.

Furthermore, when performing piercing with the focal point fixed near the surface of the workpiece, the diameter of the depression formed on the surface of the workpiece must be approximately 1 mm in order to stably perform the piercing.
It is necessary to keep the edges and sides smooth. When this condition collapses, the guidance of the laser beam within the depression is dispersed, and the heating and melting of the base material slows down.At the same time, a wide range of the base material is heated to the combustion temperature, resulting in an uncontrolled state called self-burning. Explosive combustion occurs, causing a phenomenon in which a large amount of spatter is scattered, forming a large slit-shaped depression, and the piercing stops. At this time, the nozzle was damaged by a large amount of spatter. The volume may increase, or the workpiece and nozzle may be welded together.

In order to avoid such problems, the laser output during piercing is controlled. In this method, the output of the laser oscillator is pulsed with a pulse duty of -10%.
Piercing is performed by repeating the cycle of heating, melting, and removing a minute part of the workpiece when the output is on, and cooling the workpiece when the output is off. However, this method has a problem in that the amount of workpiece material removed per unit time is very small, so the time required for piercing becomes long.

1. In the conventional piercing method, the thickness of the workpiece that can be reliably pierced is 9 mm to 12+ nm.
Moreover, the piercing time for the workpiece is approximately 20 seconds for a plate thickness of 9 mm, and approximately 40 seconds for a plate thickness of 12 mm.

SUMMARY OF THE INVENTION An object of the present invention is to provide a laser piercing method that solves the above problems and an apparatus for carrying out the method.

<Means for Solving the Problems> In order to solve the above problems, a first laser piercing method according to the present invention irradiates a workpiece with a focused laser beam from a nozzle and at the same time injects an assist gas. A laser piercing method for drilling holes in a workpiece, the height of the nozzle being set to a drilling height greater than the height for cutting, and focusing the laser beam. The position of the point is set to the predetermined position when performing the cutting work, and the drilling work is started.The drilling work is performed while maintaining the nozzle height and the position of the laser beam condensing point, and the drilling work is completed. After the cutting process is finished, the nozzle is returned to the height at which the cutting process was performed.

The second laser piercing method is a laser piercing method in which the workpiece is irradiated with a focused laser beam from a nozzle and an assist gas is injected to perform the drilling operation on the workpiece. On this occasion,
The height of the nozzle is set equal to the height at which the cutting operation will be carried out, and the position of the converging point of the laser beam is set at the position at which the cutting operation will be carried out, and the drilling operation is started, and the height of the nozzle is set equal to the height at which the cutting operation is carried out. Perform the drilling work while moving the position of the laser beam focal point in the thickness direction of the workpiece while maintaining the position of It is characterized by the fact that it can be returned to the same position as before.

The third laser piercing method is a laser piercing method in which the workpiece is irradiated with a focused laser beam from a nozzle and at the same time assist gas is injected to perform the drilling operation on the workpiece. On this occasion,
The height of the nozzle is set to a drilling height that is larger than the height when performing the cutting work, and the position of the convergence point of the laser beam is set to the position when performing the cutting work, and the drilling work is performed. As the drilling process progresses, the nozzle is moved to the cutting height, and the position of the laser beam focal point is moved in the same direction at the same time as the nozzle moves. The feature is that the position of the light condensing point is returned to the position when performing the cutting operation.

The fourth laser piercing method is a laser piercing method in which the workpiece is irradiated with a focused laser beam from a nozzle and at the same time assist gas is injected to perform the drilling operation on the workpiece. On this occasion,
The height of the nozzle is set to a drilling height greater than the height at which the cutting work is performed, and the position of the laser beam focal point is set to the position at which the cutting work is performed, and the drilling work is performed. Then, while maintaining the nozzle height, the drilling operation is carried out while shifting the position of the focal point of the laser beam in the thickness direction of the workpiece, and after the drilling operation is completed, the nozzle is used for cutting operation. This method is characterized by returning the height to the height used when cutting is performed, and returning the position of the focal point of the laser beam to the position used when cutting is performed.

Further, a typical piercing device includes a laser oscillator, a condensing section for condensing laser light, and a nozzle for emitting the condensed laser light and injecting assist gas. a first moving means for integrally moving the light part and the nozzle along the optical axis of the laser beam; and a first moving means for driving the first moving means to move the converging point of the laser beam or the nozzle to a cutting operation on the workpiece. a first control means for setting the position at which the laser beam will be focused; a second moving means for moving either the condensing section or the nozzle along the optical axis of the laser beam; and a condensing point position or the nozzle for the laser beam. a second control means for setting the laser beam to a position when performing a drilling operation on the workpiece, and setting the laser beam focal point position or the nozzle to a position when performing a cutting operation after the drilling operation is completed; It is constructed with the following.

<Function> According to the first laser piercing method described in Section 2, when performing piercing, the nozzle height is adjusted to the position during the cutting operation with the focal point position relative to the workpiece being set at the position when performing the cutting operation. Piercing can be performed by setting higher than the height.

By increasing the height of the nozzle when performing piercing in this way, the length of the airflow of the assist gas injected from the nozzle becomes longer, and the flow rate decreases as it expands as it moves away from the nozzle. Therefore, even if assist gas is injected at a flow rate higher than that required to prevent fume or spatter from flowing back from the nozzle to the nozzle, the momentum of the assist gas at the focal point will be small, and this will reduce the amount of spatter that is scattered. The kinetic energy of can be reduced. Further, a secondary airflow of the atmosphere is generated on the side of the assist gas airflow, and this secondary airflow has the effect of pushing the scattered spatter downward.

By increasing the nozzle height as described above, it is possible to reduce the amount of spatter that scatters upward from the surface of the workpiece, and to scatter this spatter from obliquely upward to within a horizontal range. Furthermore, even if there is spatter scattered upward, this spatter is cooled down before reaching the nozzle and is not welded to the nozzle. Therefore, according to this method, if the quality of the holes formed in the workpiece, such as the variation in the holes and the shape of the holes, does not affect the subsequent process, the output of the laser beam to be irradiated can be increased to produce a large amount of Piercing can be performed in a short time while scattering spatter.

According to the second laser piercing method, as the piercing operation progresses, piercing is performed while the focal point is shifted from near the surface of the workpiece, which is the position when performing the cutting operation, toward the back surface of the workpiece. I can do it. By setting the focus position to the bottom of the depression formed in the workpiece,
Piercing can always be started using the maximum energy of the laser beam. Therefore, the workpiece can be heated, melted, and burned efficiently, and the piercing time can therefore be shortened.

In this case, since piercing is carried out with the nozzle height maintained at the height used for cutting, it is preferable to suppress the amount of spatter scattered by using the output of the laser oscillator as pulse oscillation.

This method is advantageous when the quality of the through hole formed in the workpiece is important.

According to the third laser piercing method, during the progress of piercing, the nozzle height continuously shifts from the piercing start height to the cutting height, and the focal point moves from near the surface of the workpiece toward the back surface. Transition continuously.

Therefore, if variations in the diameter or shape of the through-hole do not affect the subsequent process, piercing can be performed in a short time by increasing the output of the laser beam to scatter a large amount of spatter. You can.

That is, a workpiece that is irradiated with a high-output laser beam scatters a large amount of spatter from the surface, creating a bee-like depression all at once. However, as the focal point shifts toward the back surface as the beer song progresses, the bottom surface of the formed depression is constantly irradiated with a laser beam with high energy density, and a large amount of spatter is scattered again, causing the beer song to continue. Ru.

Therefore, according to this method, a hole with a relatively large diameter can be formed in a workpiece in a short time.

Furthermore, since a recess with a relatively large diameter is formed on the surface of the workpiece, spatter generated during the piercing process is scattered over a wide range and does not adhere to the nozzle.

According to the fourth laser piercing method, the nozzle height is maintained higher than the height when performing cutting, and piercing can be performed while shifting the focus position on the workpiece from near the surface toward the back surface. I can do it. Therefore, it is possible to prevent spatter from adhering to the nozzle and to shorten the time required for piercing.

Further, according to the laser piercing device described above, each of the above methods can be automatically performed.

That is, by emitting the laser beam focused by the condensing section from the nozzle and injecting the assist 1 gas from the nozzle, it is possible to perform piercing on the workpiece. The light condensing section and the nozzle are integrally moved by the first moving means whose drive is controlled by the first control means, and the light condensing section or the nozzle is moved integrally by the second moving means whose drive is controlled by the second control means. By moving independently of each other, the nozzle height can be set to a desired value and the focal point position can be set to a desired position depending on the laser piercing method employed.

<Example> A laser piercing method and apparatus to which the above means are applied will be described below with reference to the drawings.

In each example described later, a carbon dioxide laser oscillator with a pulse frequency of 50 Hz and a peak output of 2 kW, and a focal path 1 are used.
Viasig was performed using a mild steel material with a plate thickness of 12 mm as the workpiece W using an apparatus configured with a lens with 11 finches. The pulse frequency is a preferable frequency for heating, melting, and cooling the laser beam irradiation position when piercing the workpiece W. Further, the height of the nozzle N when cutting the workpiece W is set to 1 height.

[First Embodiment] FIGS. 1(a) and 1(b) are explanatory diagrams of a piercing method corresponding to the first claim.

In the same figure (al indicates the state when cutting the workpiece W, and this state is taken as the initial state.

The distance between the lower end surface of the nozzle N and the workpiece W in the initial state is set to 1 mm, which is the cutting height dc.

The focal point F is set on the surface of the workpiece W by setting the distance H between the lens L and the workpiece W to 190 points.

While maintaining the position of lens I at distance H, set the height of nozzle N to the piercing height dp of 7 mm, and while maintaining this height dp, turn on the laser oscillator or pulse laser with a lap pulse duty of 25%. When piercing was performed with oscillation, the required piercing time was 20 seconds.

This value is a 50% reduction compared to conventional piercing time.

(Second Embodiment) FIGS. 2(a) and 2(b) are explanatory diagrams of a piercing method according to the second claim.

In the same figure (a), the positions of the nozzle N and the lens L with respect to the workpiece W are the same as in the first embodiment described above.
The height dc of the lens L is set to 1 mm, and the distance of the lens L is set to 1 mm.
11 is set to 190mm.

While maintaining the height dc of the nozzle N, the laser oscillator oscillates a pulsed laser with a pulse duty of -10% to start piercing, and as the piercing progresses,
Change the distance of lens L from 190 mm (old model) to 184 mm (
When changing to H2) and moving the position of the focal point F by 6 mm from the front surface of the workpiece W toward the back surface, the required piercing time was 25 seconds. This value is approximately 37% shorter than conventional piercing time.

[Third Embodiment] FIG. 3 is an explanatory diagram of a piercing method corresponding to FIGS. 3(a) to 3(C) and the third claim.

In the same figure (a), the position of the nozzle N and the lens L with respect to the liquid processed material W is the same as in the first embodiment described above.
The height dc of the lens L is set to l+n+n, and the distance 111 of the lens L is set to 190+nm.

While maintaining the position of the lens L at the same distance, the height of the nozzle N is set to 7 mm, which is the piercing height dp, and the laser oscillator oscillates a pulsed laser with a pulse duty of -20% to start piercing. As the piercing progresses, the distance of lens L has been changed from 190mm to 184m.
m (H2), moved the position of the focal point F by 6 mm from the front surface of the workpiece W toward the back surface, and moved the nozzle N from the piercing height dP to the cutting height dc, and the required piercing time was It was 12 seconds. This value is 70% shorter than conventional piercing time.

[Fourth Embodiment] FIGS. 4(a) to 4(C) are explanatory diagrams of a piercing method corresponding to the fourth claim.

In the same figure (a), the positions of the nozzle N and the lens L with respect to the workpiece W are the same as in the first embodiment described above.
The height dc of the lens is set to 1 mm, and the distance of the lens -20 is set to 190++++++.

While maintaining the position of the lens L at the distance H1, the height of the nozzle N is set to 7 mm, which is the piercing height dp, and while maintaining the height dp of the nozzle N, the pulse duty is -25% from the laser oscillator. Start piercing by oscillating the pulse laser, and as the piercing progresses, change the distance of the lens from 190n++n to 184mm.
When the method was changed to ()12) and the position of the focal point F was moved 6 mm from the front surface of the workpiece W toward the back surface, the required piercing time was 6 seconds.

This value is 85% shorter than conventional piercing time.

[Piercing Apparatus] Next, a piercing apparatus for carrying out the above piercing method will be described. FIG. 5 is a schematic explanatory diagram of the piercing device A.

In the figure, a laser beam 1 emitted from a laser oscillator 4 is guided along an optical axis 5 through an optical system including mirrors, prisms, etc. (not shown), and is guided through a lens 6 which serves as a condenser.
The spot 7 is formed by focusing an image on a predetermined position in the thickness direction of the workpiece.

The lens 6 is fixed to a cylindrical body 9 fixed to a lifting bracket 8 serving as a first moving means. The lifting bracket 8
is attached to the machine frame 13 and is driven by a motor 8a to move up and down, thereby allowing the nozzle 3 and lens 6 to move up and down integrally. Incidentally, reference numeral 8b denotes a motor control section serving as a first control means for controlling the drive of the motor 8a, and is configured to be connected to a central control device (not shown) to send and receive signals.

The nozzle 3 is fitted into the cylindrical body 9 so as to be movable up and down along the optical axis 5. A rack 10a serving as a second moving means is fixed to a predetermined position of the nozzle 3, and a motor 11a is fixed to the lifting bracket 8. Also, the motor 11a
A pinion 10b is fixed to the shaft of the pinion 10b, which meshes the pinion 10b with the rank 10a and controls the rotation of the motor 11a by a motor control section 1 serving as a second control section.
．． 1b, the nozzle 3 is moved along the optical axis 5 and the height of the nozzle 3 can be set. The motor control section 11b is configured to be connected to a central control device (not shown) to exchange signals.

A chamber 3a is formed inside the nozzle 3, and a hole 3b for passing the laser beam 1 and the assist gas 2 is formed at the tip coaxially with the optical axis 5. Also nozzle 3
A supply hole 3c for supplying the assist gas 2 to the chamber 3a is formed at a predetermined position on the side surface of the chamber 3a. The assist gas 2 adjusted to a predetermined pressure can be supplied from the gas supply device 12 to the chamber 3a through the supply hole 3o.

As the assist gas 2, oxygen gas, nitrogen gas, or an inert gas such as argon gas is selectively used depending on the material of the workpiece A. Namely, steel plate.

Oxygen gas is often used when piercing a stainless steel plate, etc., and subsequently cutting, and care must be taken to avoid oxidation or other effects on the base material in the processed part. In this case, an inert gas is often used.

=23- The gas supply device 12 includes a bong 12a for supplying oxygen gas or inert gas, etc., a pressure adjustment device 12b,
It is configured by a valve 12c and a valve 12a.
After the high-pressure gas filled in the nozzle 3 is adjusted to a predetermined supply pressure in the pressure regulator 12b, the assist gas 2 is supplied to the chamber 3a of the nozzle 3 by opening and closing the valve 12c, which is driven in accordance with the piercing. The structure is such that the supply can be started or stopped.

Next, a procedure for piercing a workpiece W using the piercing apparatus A configured as described above will be described.

First, the motor control units 8b and 11b are provided with piercing time data preset according to the material, plate thickness, etc. of the workpiece W, height data of the nozzle 3 when piercing, and nozzle when cutting. 3. Memorize the height data etc.
Next, the nozzle 3 is set at a predetermined drilling position on the workpiece A.

Next, a central control device (not shown) is operated to control the laser oscillator 4. Gas supply device 12. Motor control section 8b, llb
When a signal to start the piercing operation is transmitted to the nozzle 3 and the lens 6, the motor 8a is controlled by the motor control section 8b to raise and lower the nozzle 3 and the lens 6 integrally to a height at which a spot 7 can be formed near the surface of the workpiece W. Next motor 1.1
a moves the nozzle 3 along the optical axis 5 to a predetermined piercing height under the control of the motor control section 11b. Then, the laser beam 1 is emitted from the laser oscillator 4, and at the same time, the assist gas 2 is supplied to the nozzle 3 from the gas supply device 12, and is ejected from the hole 3b of the nozzle 3 along the laser beam 1.

In the above state, piercing of the workpiece W is performed. Then, when a preset piercing time has elapsed, the motor controller 11b controls the motor 11a.
rotates to move the nozzle 3 to a predetermined cutting height, and at the same time transmits a piercing end signal from the motor controller 11b to the central controller. The control device to which the piercing end signal is transmitted determines whether or not to continue the cutting operation, stops the laser oscillator 4 and the gas supply device 12, or moves the nozzle 3 and the workpiece A relatively. Then carry out the cutting work.

FIG. 6 is an explanatory diagram of the piercing device B. In the drawings, the same parts and parts having the same functions as those in the above-described embodiment are designated by the same reference numerals, and explanations thereof will be omitted.

In the figure, a nozzle 3 is fixed to an elevating bracket 8 serving as a first moving means, and a cylinder 9 to which a lens 6 is fixed is fitted to the nozzle 3 so as to be movable along the optical axis 5. .

At a predetermined position on the side of the cylindrical body 9 is a rack 1 serving as a second moving means.
A motor 15a serving as a driving means is fixed to the lifting bracket 8. A pinion 1. is attached to the shaft of the motor 15a. , lb are fixed,
By meshing the binion 14b with the rack 14a, the cylindrical 9° lens 6 is moved along the optical axis 5 by the motor 15a. Said motor 1
The rotation of 5a is controlled by a motor control section 15b.

Therefore, in this embodiment, the nozzle 3 and the lens 6 are raised and lowered integrally by the lifting bracket 8, and the lens 6
is configured to be movable along the optical axis 5.

When piercing the workpiece W using the piercing apparatus B configured as described above, piercing can be carried out in the same manner as in the above embodiment.

In the above piercing devices A and B, the motor control section 8
b, Ilb, and i5b each have a motor 8a.

A measuring member such as a rotary encoder is provided to measure the amount of rotation of the nozzles 11a and 15a in one rotational direction. It is configured to be able to store the position at which the lens 6 is cut or the position at which piercing is performed.

and nozzle 3. When the lens 6 moves from a predetermined position to a different position (for example, from an initial position to a piercing position), these stored data are calculated by the central controller to determine the relative position of the nozzle 3 or lens 6 with respect to the workpiece ItW. They are configured so that their relative positions can be changed without changing their positions.

<Effects of the Invention> As explained in detail above, according to each method according to the present invention, when piercing a workpiece such as a metal plate, vaporized metal generated in the workpiece is fume, molten metal, molten oxide, etc. removed from the workpiece will not adhere to the lens or nozzle. Therefore,
When carrying out piercing and cutting work subsequent to piercing, the work can be carried out smoothly by preventing the harmful effects of fumes and molten substances.

Further, there is no need to perform work such as cleaning the nozzle or lens, and work can be carried out efficiently.

Further, according to the piercing device according to the present invention, each of the above methods can be automatically performed. Therefore, the nozzle and lens have the characteristics of being maintenance-free.

[Brief explanation of the drawing]

1st [ff1(a), (1-+) is an explanatory diagram of the piercing method corresponding to the first claim, FIG. 2(a), (b) is a piercing method corresponding to the second claim. Explanatory diagram of the method, Figure 3 (a)-(
C) 1''S An explanatory diagram of the piercing method corresponding to the third claim, FIGS. 4(a) to (C) are explanatory diagrams of the piercing method corresponding to the fourth claim, and FIG. 5 is an explanatory diagram of the piercing method corresponding to the fourth claim. A schematic explanatory diagram, FIG. 6 is an explanatory diagram of piercing device B. A and B are piercing devices, W is a workpiece, ■ is a laser beam, 2 is an assist gas, N, 3 is a nozzle, 3a is a chamber, 3
b is the hole, 4 is the laser oscillator, 5 is the optical axis, L, 6 is the lens, F, 7 is the spot, 8 is the lifting bracket,
9 is a cylinder, 10a +' 14a is a rack, 10b, 1
4b is a binion, 8a, 'lla, 15a is a motor, 8b, Ilb, 15b is a motor control section, 12 is a gas supply device, and 13 is a machine frame. Patent applicant Koike Oxygen Industry Co., Ltd.

Claims (6)

[Claims] (1) A laser piercing method in which a workpiece is irradiated with a focused laser beam from a nozzle and at the same time an assist gas is injected to make a hole. The drilling height is set to a height greater than the height at which the cutting operation will be performed, and the position of the laser beam condensing point is set at a predetermined position at which the cutting operation will be performed, and the drilling operation is started, and the nozzle A laser piercing method characterized by performing drilling work while maintaining the height and the position of the focal point of the laser beam, and returning the nozzle to the height at which cutting work is performed after the drilling work is completed. (2) A laser piercing method in which a workpiece is irradiated with a focused laser beam from a nozzle and at the same time an assist gas is injected to drill the workpiece, and when performing drilling work on the workpiece, the height of the nozzle is The nozzle height is set equal to the height at which the cutting operation will be performed, and the position of the laser beam condensing point is set at the position at which the cutting operation will be performed, and the drilling operation is started, maintaining the nozzle height. Drilling is performed while moving the laser beam focal point in the thickness direction of the workpiece, and after the drilling is completed, the laser beam focal point is adjusted to the position when cutting. A laser piercing method characterized by returning to. (3) A laser piercing method in which a workpiece is irradiated with a focused laser beam from a nozzle and at the same time an assist gas is injected to drill the workpiece, and when performing the drilling operation on the workpiece, the height of the nozzle is Start the drilling work by setting the height to a drilling height that is larger than the height at which the cutting work will be performed and the position of the laser beam focal point to the position at which the cutting work will be performed. As the hole progresses, the nozzle is moved to the height at which cutting is performed, and the position of the laser beam focal point is moved in the same direction at the same time as the nozzle moves. A laser piercing method characterized by returning the position to the position when performing cutting work. (4) A laser piercing method in which a workpiece is irradiated with a focused laser beam from a nozzle and at the same time an assist gas is injected to make the hole. The nozzle is set to a drilling height that is larger than the height at which the cutting operation will be performed, and the position of the laser beam condensing point is set to the position at which the cutting operation will be performed, and the drilling operation is started. Perform the drilling work while shifting the position of the laser beam condensing point in the thickness direction of the workpiece while maintaining the same height, and after the drilling work is completed, adjust the nozzle to the height at which the cutting work will be performed. A laser piercing method characterized by returning the focal point of the laser beam to the position at the time of cutting. (5) It has a laser oscillator, a condensing part for condensing laser light, and a nozzle for emitting the condensed laser light and injecting assist gas, and the condensing part and nozzle are a first moving means that integrally moves the laser beam along the optical axis; and a position at which the first moving means is driven to position the converging point of the laser beam or the nozzle when cutting the workpiece. a first control means for moving either the light condensing section or the nozzle along the optical axis of the laser beam; It is characterized by having a second control means for setting the position at which the drilling operation is to be carried out and also setting the laser beam focal point position or the nozzle to the position at which the cutting operation is to be carried out after the drilling operation is completed. Laser piercing device. (6) It has a laser oscillator, a condensing part for condensing the laser beam, and a nozzle for emitting the condensed laser beam and injecting assist gas, and the condensing part and the nozzle are a first moving means for integrally moving along the optical axis of the laser beam; a second moving means for moving either the condensing section or the nozzle along the optical axis of the laser beam; The position of the convergence point of the laser beam in the thickness direction and the position of the first moving means and the second moving means when the nozzle is at the height when performing cutting work are taken as the measurement origin, and the By calculating the movement amount of the first moving means and the second moving means, the relative position of the laser beam focusing point and the nozzle can be determined without changing the position of the laser beam focusing point in the thickness direction of the workpiece or the nozzle height. A laser piercing device characterized by having a control means for controlling to change.