JPH11156579A - Methods for laser cutting, laser piercing, laser welding and laser decoration, and laser processing heads therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser cutting method which enables the thick board cutting corresponding to a high power laser processing machine of 6 kW or so, a laser piercing method which enables the thick board piercing with less spatter, a welding method wherein an allowable range of size deviation of the gap between members to be butt welded is big and the gap management is simple, and a laser beam decoration method wherein various patterns can be applied on the surface of a workpiece at high speed, as well as to obtain laser heads to be used for each processing method, in a laser processing machine of middle power at the extent of 2 kW. SOLUTION: In a laser processing head 1 of a laser processing machine, a freely rotary drive decentering optical system 53, which decenters a laser beam LB from an optical axis 55 of an optical system 11 for condensing the laser beam, is provided at the bottom position of the optical system 11 for condensing the laser beam. An assist gas nozzle 75 is also provided, which coaxially ejects the assist gas as soon as the laser beam from the decentering optical system 53 is passed through.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser cutting method,
The present invention relates to a laser piercing method, a laser welding method, a laser decoration method, and a laser processing head used in each of the above methods.

[0002]

2. Description of the Related Art The cutting accuracy that can withstand practical use in laser cutting of a thick plate by a laser processing machine with a laser output of 2 kW class is limited to about 16 mm to 19 mm for mild steel sheet and about 15 mm for stainless steel. Have been.

In the butt welding process, a method of irradiating a laser beam defocused on a welding line and moving a workpiece relative to the laser beam, a method of intersecting the laser beam on the welding line in a direction crossing the welding line, There is known a method in which a workpiece is moved relative to the laser beam at the same time when the workpiece is scanned and welding is performed.

In the laser cutting method, the laser beam condensed at almost one point by the optical system and the workpiece are relatively moved, and at the same time, the laser beam is coaxially moved from the assist gas nozzle to the cutting section. Cutting is performed by injecting oxygen gas.

In a method of processing various patterns on a surface of a workpiece by a laser beam, that is, a laser decoration method, a work table on which a workpiece is mounted is moved relative to the laser beam by NC control. Laser decoration is being carried out.

[0006] Laser piercing includes a case where a continuous output laser is used and a case where a pulse output laser is used.

[0007] In the case of piercing with a continuous output laser, the piercing time is short, but spattering (oxidation product of molten metal)
Are scattered, and a bulge is formed around the pierced hole. The bulge interferes with the laser processing head, and spatter adheres to a nozzle of the laser processing head. In comparison with this, the pulse output laser is characterized in that spatter is less scattered but the piercing time is longer.

[0008] The thickness of a steel plate that can be used with the above-mentioned conventional piercing is limited to about 16 mm.

[0009]

In a laser processing machine with a laser output of 2 kW class using the conventional cutting processing method, the laser beam is cut from the assist gas nozzle coaxially with the laser beam condensed to almost one point by the optical system. The cutting process is performed by injecting oxygen gas into the part, so when cutting a thick plate, the pressure of the assist gas at the bottom or tip of the cutting becomes weak, oxygen gas is not sufficiently supplied, and an oxidation reaction occurs There is a problem that the cutting phenomenon cannot be maintained.

Further, in a laser processing machine having a laser output of 2 kW class, it is necessary to increase the size of the laser processing machine in order to cut a thick plate of 16 mm to 19 mm or more. The optical path length of the optical system to be extended becomes longer, and the attenuation of the laser output in the optical system such as a bend mirror also increases. Therefore, it is practically difficult to cut a thick plate more than the above, and in some cases, a cut of 19 mm. Nor is it guaranteed.

In the laser piercing, as described above,
A lot of spatter (molten metal oxide) is scattered,
A bulge is formed around the pierced hole, this bulge interferes with the laser processing head, spatter adheres to the nozzle of the laser processing head, and the thickness of a pierceable steel plate is limited to about 16 mm There is a problem.

In butt welding, the spot diameter of the focused laser beam is extremely small.
The dimensional error range of the gap between the members to be welded is 10% of the plate thickness
Therefore, there is a problem that the precision control of the dimensional error of the gap between the welding members becomes strict. Further, there is a problem that the dimensional error of the gap becomes difficult as the welding speed increases, unless the accuracy is improved.

Further, in the conventional laser decoration method, since the work table on which the workpiece is placed is moved by NC control, there is a problem that high-speed and high-precision processing is difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a medium-power laser processing machine having an output of about 2 kW and a high-power laser processing machine having a power of about 6 kW. Laser cutting method capable of cutting thick plates equivalent to the above, welding method with large tolerance of dimensional error of gap between butt-welded members, easy gap management, and piercing of thick steel plates up to approximately 25 mm in thickness A piercing method capable of reducing scattering of spatter and having a small bulge around a piercing hole and a decoration method using a laser beam capable of processing various patterns on the surface of a workpiece at a high speed. It is to provide a laser processing head to be used.

[0015]

According to a first aspect of the present invention, there is provided a laser cutting method comprising the steps of: collecting a laser beam focused by a laser beam focusing optical system of a laser processing head; An eccentric optical system for decentering from the optical axis of the optical system is provided, and a small laser beam spot that is decentered by the eccentric optical system and condensed at a focal position is centered on the axis of the optical system for condensing. Rotating and simultaneously supplying the assist gas from the assist gas nozzle of the laser processing head to the cutting portion of the workpiece, and cutting the workpiece by relatively moving the optical axis and the workpiece. It is the gist.

According to a second aspect of the present invention, in the laser cutting method according to the first aspect, the eccentric optical system is rotatably provided on the optical axis of the condensing optical system at an inclination angle α. The gist is that it is an optical flat having a plate thickness t.

According to a third aspect of the present invention, in the laser cutting method according to the second aspect, the inclination angle α is 10 degrees ± 5 degrees and the thickness t is 5 mm ± 2.5 mm.
The gist is that

A laser cutting method according to a fourth aspect of the present invention is the laser cutting method according to the first aspect, wherein the converging optical system is provided with a converging lens decentered with respect to an incident beam optical axis and the light is incident on the converging lens. The gist is that the beam optical axis is rotatably provided about the axis, and the condenser lens itself is an optical system for decentering.

According to a fifth aspect of the present invention, in the laser cutting method according to the first aspect, the converging optical system includes a converging lens that tilts the converging lens with respect to an incident beam optical axis by an angle α.
And the optical axis of the incident beam is rotatably provided about an axis, and the condensing lens itself is an optical system for decentering.

According to a sixth aspect of the present invention, in the laser cutting method, the condensing optical system has an F number that is about twice as large as a constant when cutting a thin plate having a maximum of about 16 mm, and the gas supplied from the assist gas nozzle is , 60-300Nl / min
The point is that the gas flow rate is set to a pseudo Gaussian assist gas.

According to a seventh aspect of the present invention, the gas pressure of the assist gas nozzle is set to 0.2 to 0.6 bar.

Therefore, according to the laser cutting method of the present invention, the minute beam spot of the condensed laser beam is rotated on the cutting line while the cutting front of the steel sheet (in the cutting process). Area) is cut (evaporated) or removed little by little. Since the depth of the cutting front is very small, assist gas such as oxygen is sufficiently supplied to the bottom of the cutting front, and the oxidation reaction is activated to generate heat of reaction, and discharge of metal and the like melted by the assist gas. Is performed immediately,
The cutting of the steel sheet proceeds with a cutting width B (2 × rotation radius). Further, in the above cutting process, the volume of the cutting front portion of the steel sheet W removed when the beam spot makes one rotation can be reduced by reducing the feed amount ΔL by the area of the crescent-shaped portion (S) × the minute depth (ΔH). ), The volume of this cutting front portion becomes very small, and the repeated rotation of the laser beam results in a state in which the material is pre-heated in advance. Medium power laser processing machine
A thick steel plate of about 5 mm can be cut.

According to a eighth aspect of the present invention, there is provided a laser welding method, comprising: an eccentric optical system for eccentrically deviating a laser beam focused by a laser beam focusing optical system of a laser processing head from an optical axis of the focusing optical system. A small laser beam spot decentered by the eccentric optical system and condensed at the focal position is rotated about the axis of the optical system for condensing, and simultaneously along the welding line of the workpiece. The gist of the invention is to weld the workpiece by relatively moving the optical axis of the laser processing head.

According to a ninth aspect of the present invention, in the laser welding method according to the eighth aspect, the eccentric optical system is rotatably provided on the optical axis of the condensing optical system at an inclination angle α. The gist is that it is an optical flat having a plate thickness t.

[0025] The laser welding method according to claim 10 is
10. The laser welding method according to claim 9, wherein the inclination angle α is 20 degrees ± 15 degrees and the plate thickness t is 5 mm ±.
The point is that the length is 2.5 mm.

Therefore, according to the laser welding method of the present invention, since a minute laser beam spot is rotated about the optical axis, a welding defect is generated even if the welding gap fluctuates slightly. A good welding can be performed without any.

[0027] The laser decorating method according to claim 11 is characterized in that:
An eccentric optical system for eccentrically deviating a laser beam condensed by a laser beam condensing optical system of a laser processing head from the optical axis of the condensing optical system is provided, and a focal position is decentered by the eccentric optical system. At the same time as rotating the minute laser beam spot focused on the axis of the focusing optical system, the workpiece is moved relative to the optical axis of the laser processing head. The point is to draw a pattern on the surface of the material.

The laser decorating method according to claim 12 is
12. The laser decoration method according to claim 11, wherein the decentering optical system includes at least one or more prisms (optical wedges) that are rotatably driven around the optical axis of the focusing optical system. It is the gist.

The laser decorating method according to claim 13 is
13. The laser decorating method according to claim 12, wherein the prism (optical wedge) includes two prisms (optical wedge) provided at a fixed distance, and each of the prisms (optical wedge) is independently positive. The gist of the present invention is to provide rotatable driving in the opposite direction.

Therefore, according to the laser decoration method of the present invention, the laser beam condensed by the eccentric optical system is rotated and the workpiece is moved with respect to the optical axis of the laser processing head. By moving the workpiece, various patterns can be drawn on the surface of the workpiece.

According to a fourteenth aspect of the present invention, there is provided a laser piercing method, wherein the laser beam focused by the laser beam focusing optical system of the laser processing head is decentered from the optical axis of the focusing optical system. A minute laser beam spot decentered by the eccentric optical system and condensed at the focal position is rotated about the axis of the converging optical system, and assisted by an assist gas nozzle of the laser processing head. The gist of the present invention is to supply a gas to a cut portion of a workpiece and to perform through-hole processing in the workpiece.

Therefore, according to the laser piercing method of the present invention, the minute beam spot of the condensed laser cuts a part of the cutting front (the area in the cutting process) of the steel sheet little by little while rotating. Evaporation) or removing. Since the depth of this cutting front is very small,
Assist gas such as oxygen is sufficiently supplied to the bottom of the cutting front, and the oxidation reaction is activated to generate reaction heat.
Further, since the molten metal or the like is discharged immediately by the assist gas, a laser piercing of a thick steel plate having a thickness of about 25 mm is possible even with a medium-power laser processing machine of about 2 kW.

The laser piercing method according to claim 15 is the laser piercing method according to claim 14,
A pulse laser is used for the laser beam incident on the laser beam focusing optical system, and the frequency and the pulse duty of the pulse laser are set low at the start of piercing, and the frequency and the pulse duty are set with the progress of the piercing. The gist is to complete the piercing process by increasing the laser output stepwise until the laser output reaches the command value.

The laser piercing method according to claim 16 is the laser piercing method according to claim 14 or 15, wherein the eccentric optical system rotates at an inclination angle α around the optical axis of the condensing optical system. The gist of the invention is that it is an optical flat with a thickness t provided so as to be freely driven.

The laser piercing method according to a seventeenth aspect is the laser piercing method according to the fourteenth or fifteenth aspect, wherein the condenser lens is provided so as to be eccentric with respect to the optical axis of the incident beam and the incident beam light is provided. The gist of the invention is that the shaft is rotatably provided about the axis, and the condenser lens itself is an optical system for decentering.

The laser piercing method according to claim 18 is the laser piercing method according to claims 14 and 15, wherein the condenser lens is provided at an inclination angle α with respect to the optical axis of the incident beam, and The gist is that the optical axis is rotatably provided around the axis, and the condenser lens itself is an optical system for decentering.

The laser piercing method according to claim 19 is characterized in that:
The condensing optical system has an F-number approximately twice as large as a constant for cutting a thin plate having a maximum of about 16 mm, and the gas supplied from the assist gas nozzle is 60 to 300 Nl / m2.
The gist is that the assist gas is a pseudo-Gaussian assist gas having a gas flow rate of in.

The laser piercing method according to claim 20, wherein the gas pressure of the assist gas nozzle is 0.2 to 0.6.
The gist should be bar.

Therefore, according to the laser piercing method according to claims 14 to 20, a laser piercing of a steel plate having a thickness of about 25 mm is possible even in a medium power laser processing machine of about 2 kW. Using a pulse laser, the frequency and pulse duty of this pulse laser are set low at the start of piercing, and as the piercing proceeds, the frequency and pulse duty are increased stepwise until the laser output reaches the command value. Since the piercing process is completed, spattering (oxidation product of molten metal) is less scattered, and no bulge is formed around the piercing hole.

A laser processing head according to a twenty-first aspect is a laser processing head of a laser processing apparatus,
When an eccentric optical system that is rotatably driven to eccentric the laser beam from the optical axis of the optical system for focusing is provided at a position below the optical system for focusing the laser beam, and the laser beam from the optical system for eccentricity is passed. The gist of the invention is to provide an assist gas nozzle for simultaneously injecting the assist gas coaxially.

The laser processing head according to claim 22 is the laser processing head according to claim 21,
The gist of the invention is that the decentering optical system is an optical flat having a plate thickness t provided rotatably at an inclination angle α on the optical axis of the condensing optical system.

The laser processing head according to claim 23 is the laser processing head according to claim 22,
The inclination angle α is 10 degrees ± 5 degrees and the plate thickness t is 5 mm ±
The point is to be 2.5 mm.

The laser processing head according to claim 24 is the laser processing head according to claim 21,
The condensing optical system is provided such that the condensing lens is decentered with respect to the incident beam optical axis, and the incident beam optical axis is rotatably provided about the axis, and the condensing lens itself is used as the decentering optical system. It is the gist.

The laser processing head according to claim 25 is the laser processing head according to claim 21,
The condensing optical system is provided with a condensing lens at an inclination angle α with respect to the incident beam optical axis, and is provided rotatably around the incident beam optical axis, and the condensing lens itself is used as an eccentric optical system. The gist is that.

Therefore, according to the laser processing head of the present invention, the minute beam spot of the condensed laser beam is rotated on the cutting line while the cutting front of the workpiece (the cutting process). A small portion (evaporation) or removal. But,
Since the depth of the cutting front that is removed by one rotation of the laser beam is very small, assist gas such as oxygen is sufficiently supplied to the bottom of the cutting front to generate a large amount of heat of oxidation reaction and melt by the assist gas. Discharge of metal etc. is performed immediately. Also, the workpiece is cut with a cutting width of "2 x radius of rotation", and the volume of the cutting front part of the workpiece removed when the laser beam makes one rotation can be removed by reducing the feed amount. The volume of the front portion is very small, and a thick steel plate of about 25 mm can be cut by a medium-power laser processing machine of about 2 kW.

The laser processing head according to claim 26 is the laser processing head according to claim 21 or 22, wherein the inclination angle α is 20 degrees ± 15 degrees and the plate thickness t is 5 mm ± 2.5 mm The point is that there is something.

Therefore, according to the laser processing head of the present invention, since the minute laser beam spot is rotated about the optical axis, even if the welding gap fluctuates somewhat, good welding can be achieved without any welding defect. Welding can be performed.

The laser processing head according to claim 27 is the laser processing head according to claim 21,
The eccentric optical system comprises at least one or more prisms (optical wedges) rotatably driven around the optical axis of the condensing optical system.

The laser processing head according to claim 28 is the laser processing head according to claim 27,
The prism (optical wedge) is composed of two prisms (optical wedge) provided at a fixed distance, and each of the prisms (optical wedge) is independently rotatably driven in forward and reverse directions. It is assumed that.

Therefore, according to the laser processing head according to the twenty-seventh and twenty-eighth aspects, the laser beam condensed by the eccentric optical system is rotated and the workpiece is moved with respect to the optical axis of the laser processing head. By moving, various patterns can be drawn on the surface of the workpiece.

[0051]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of a laser processing head according to the present invention. Referring to FIG. 1, a laser processing head 1 includes, for example, a lens unit mounting member 5 having a lens unit 3 provided with a condenser lens for condensing a laser beam from a carbon dioxide gas laser oscillator (not shown), It is composed of four cylinders, nozzles and the like which are sequentially coupled to the lens unit mounting member 5.

A screw hole 7 for mounting the lens unit 3 is provided at the axis of the lens unit mounting member 5, and a male screw portion 9 provided on the lens unit 3 is screwed into the screw hole 7. . The lens unit 3 is provided with a suitable condenser lens 11 for condensing the laser beam LB.

Inside the lens unit mounting member 5, there is provided a cooling liquid channel 13 through which a cooling liquid of an appropriate temperature for cooling the lens unit mounting member 5 flows. From the coolant supply port 15
For example, a coolant such as water is supplied, and the coolant supplied from the coolant supply port 15 is discharged from a coolant discharge port (not shown).

With the above configuration, the lens unit 3 can be cooled to an appropriate temperature via the lens unit mounting member 5. Therefore, the condenser lens 11 can be maintained at an appropriate temperature.

A first cylindrical body 17 is integrally connected to a lower portion of the lens unit mounting member 5 by a plurality of bolts 19. In addition, the first cylindrical body 17 has a first
A second cylinder 21 having an outer diameter substantially equal to that of the cylinder 17 is integrally connected. In addition, the first cylindrical body 17 and the second cylindrical body 21 are connected by a plurality of bolts formed by a flange 23 provided at a lower part of the first cylindrical body 17 and a flange 25 provided at an upper part of the second cylindrical body 21. 27.

At the lower end of the second cylindrical body 21, an annular member 29 having a bearing mounting portion on the inner diameter is mounted by a plurality of bolts 31. Further, the second cylindrical body 21
There is also a bearing mounting part at the upper inside diameter of
The bearing mounting portion of the annular member 29 and the second cylindrical body 2
A rotating cylinder 35 is rotatably supported on inner rings of upper and lower bearings 33 which are fixedly attached to the outer ring to the first bearing mounting portion. The upper and lower bearings 33 are fixed by bearing retainers 34.

A driven pulley 37 is attached to the outer diameter of the rotary cylinder 35 by bolts or the like. In addition, the second
A motor bracket 39 is integrally provided on the cylindrical body 21 so as to protrude to the side. A motor base 41 is provided on the upper surface of the motor bracket 39 so as to be movable and fixed. The rotating cylinder 3 is placed on the motor base 41.
5 is provided with a motor 43 for rotationally driving the motor 5.
A drive pulley 47 is attached to the output shaft 45 of the motor 43, and a drive belt 49 is looped between the drive pulley 47 and the driven pulley 37.

It is preferable that a toothed pulley and a toothed belt are used for the driven pulley 37, the driving pulley 49 and the driving belt 47. Further, the drive belt 49 is provided with a window 51 provided on a side of the second cylindrical body 21.
It is hung between both pulleys via. In addition, the laser beam LB is placed on the optical axis 55 above the rotary cylinder 35.
The thickness t (m
m) the optical flat 53 with the laser beam L
An annular optical flat support 57 that supports the optical axis 55 of B at an angle α is attached. Note that the optical flat is generally circular, but does not necessarily have to be circular.

The lower part of the annular member 29 has a third
A cylindrical body 59 is integrally attached by a plurality of bolts 61. An optically transparent upper portion inside the third cylindrical body 59 for preventing an assist gas such as oxygen, air or nitrogen gas and dust in the air from entering the second cylindrical body 21. Window 63 is attached. And
An assist gas supply port 64 for supplying the assist gas is provided on a side portion of the third cylindrical body 59 below the window 63. Preferably, the window 63 is made of an optical material or an optical glass coated with an anti-reflection coating so as to transmit the laser beam LB well.

A fourth end of the third cylinder 59 is provided with a fourth end.
A cylinder 65 is provided. A flange 67 is provided at the upper end of the fourth cylinder 65 so that the axis of the fourth cylinder 65 can be moved to a position eccentric with respect to the optical axis 55 of the laser beam LB. Is radially movably fitted in a circular concave portion 69 provided at the lower end of the fourth cylinder 65, and presses the flange 67 of the fourth cylinder 65 to move the axis of the fourth cylinder 65 in an appropriate direction. For this purpose, at least three setscrews 71 are provided on the third cylinder 59 at an equal angle. Further, a flange fixing member 73 for fixing the axis of the fourth cylinder 65 to the third cylinder 59 is provided.

An assist gas nozzle 75 is screwed into a male thread provided on the outer diameter of the lower end of the fourth cylinder 65. A nozzle tip 79 having an assist gas injection port 77 is detachably screwed to the tip of the assist gas nozzle 75.

With the above configuration, the laser beam LB focused by the focusing lens 11 of the laser processing head 1
Is focused on a plane having a focal length f through the optical flat 53 supported by the optical flat support 57 at an angle α. At this time, the position of the laser beam focused on the position of the focal length f on the plane is determined by the law of refraction described later.
A small distance δ of about 0.1 mm to several mm from the optical axis 55 of
The light is condensed only at the eccentric position. Therefore, when the motor 43 is driven, the rotary cylinder 35 supporting the optical flat 53 is rotated, so that the laser beam converged on a plane moves circularly about the optical axis 55 with a radius r = δ. Will do.

By appropriately adjusting the three setscrews 71, the center of the assist gas ejection port 77 of the nozzle tip 77 is set to the above-mentioned radius r = δ with respect to the optical axis 55 of the laser beam LB. Can easily be adjusted to the center of the circular motion of

The diameter of the assist gas outlet 77 is at least 2 * δ so as not to interfere with the circular movement of the laser beam.

Referring to FIG. 2, the optical flat 53 made of a material having a thickness t (mm) and a refractive index n larger than 1 is moved with respect to the optical axis 55 of the laser beam LB from the condenser lens 11. When the laser light is inclined by the angle α, the incident angle I formed between the laser light incident on the optical flat 53 and the normal 80 erected on the plane of the optical flat 53 differs depending on the position of the outer peripheral portion of the incident laser light.

In FIG. 2, the incident angle of the incident light at the right end of the laser beam LB is I ₁ , the refraction angle is R ₁ , the incident angle of the incident light at the left end of the laser beam LB is I ₂ , and the refraction angle is R ₂ Then, according to Snell's law, the refractive index n is
n = SinI ₁ / SinR ₁ . First, since n> 1, I ₁ > R ₁ , and similarly, n = SinI ₂ / Sin
R ₂ , and hence I ₂ > R ₂ , and since the upper and lower surfaces of the optical flat 53 are parallel, the light beam emitted from the optical flat 53 is parallel to the incident light. Therefore, the focal position f of the laser beam LB emitted from the optical flat 53 is a position decentered by δ with respect to the optical axis 55 of the laser beam LB.

Next, a method for laser cutting a steel sheet using the laser processing head 1 will be described with reference to FIGS. 3 and 4. When cutting a steel sheet W, which is a workpiece having a thickness of t (mm), along a cutting line 81, a laser whose focal position is decentered by r = δ with respect to the optical axis 55 of the laser beam LB. Processing head 1
In the case of, the optical flat 53 is rotated at a high speed of several hundred to several thousand rotations by the motor 43,
An assist gas of several atmospheres to several tens atmospheres is injected into the cut portion of the steel sheet W, and the laser processing head 1
Are relatively moved.

In the cutting process of the above-described cutting method, the minute beam spot 83 of the condensed laser is rotated on the cutting line 81 with a radius r (= δ) while cutting the steel sheet W (in the cutting process). A part of (a certain area) 85 is gradually cut (evaporated) or removed at a high speed. Further, since the depth ΔH of the cutting front (region in the cutting process) 85 is very small, an assist gas such as oxygen is sufficiently supplied to the bottom of the cutting front 85 to activate the oxidation reaction and generate reaction heat. At the same time, the metal and the like melted by the assist gas are immediately discharged,
The cutting of the steel sheet W proceeds with the cutting width B (= 2r = 2δ).

In the above cutting process, the volume of the cutting front portion 85 of the steel plate W removed when the laser beam makes one rotation is only the area (S) of the crescent-shaped portion 86 × the depth ΔH. If the amount ΔL is reduced, the volume of the cutting front portion 85 becomes very small and 2
25mm even for medium power laser processing machines around kW
About thick steel plate can be cut.

According to the experiment using the above method, the laser output was 1.6 kW and the relative feed speed was 200 mm / min.
In the range of 400 mm / min, good cutting with a cutting width of 2 mm or less was possible up to a maximum thickness of about 25 mm of the steel sheet. The focal position was set inside the cutting material.

The eccentricity δ is determined by the thickness t (mm) of the optical flat 53 and the angle α with respect to the optical axis 55.
It is possible to obtain a desired appropriate amount of eccentricity δ by changing the thickness of the steel sheet.
When cutting a thick plate of about 5 mm, α = 10 degrees ± 5
It is desirable that t = 5 ± 2.5 mm.

Next, a method of laser welding a steel sheet W using the laser processing head 1 will be described with reference to FIG. For example, in FIG. 5 (a) ~ FIG 5 (b), a known X, as weld members on the work table with Y positioning mechanism (not shown), the weld between the steel plate W ₁ and the steel plate W ₂ is opposed by providing appropriate welding gap is placed fixed on the center line of the welding gap of the steel plate W ₁ and the steel plate W _2, that is, over the welding line 87, the laser processing head 1 (the focal position of the laser r = The optical axis 55 (eccentric by δ), that is, the rotation center of the laser processing head 1 is aligned, and the minute beam spot 83 of the laser beam LB condensed on almost the surface of the steel plate W is rotated with a radius r (δ). 5 and along this welding line 87, FIG.
In the example of (a), the side of the steel plate to be welded is moved relative to the optical axis 55 in parallel with the welding line.

As the input energy to the welding portion, an appropriate energy suitable for each welding process is input, and a penetration region region 89 effective for welding is formed around the minute beam spot 83. The side of the steel plate W to be welded may be fixed, and the optical axis 55 of the laser processing head 1 may be moved along the welding line of the steel plate W to be welded. Note that the principle described here is the same in the case of cutting.

In the welding process shown in FIG. 5A, the relative feed speed V ₁ of the steel sheet W with respect to the optical axis 55 is set.
Is large (about 1,000 mm / min), and the trajectory 91 of the beam spot 83 has a spiral shape with a large interval. Therefore, the positions P ₁ and P ₂ of the beam spot 83 on the welding line 87 are slightly separated from each other, and the penetration region 89 effective for welding does not overlap.

[0075] FIG. 5 (b), and the rotational speed of the optical axis 55 of the laser processing head 1 the same as in the case of FIG. 1, the relative feed speed with respect to the optical axis 55 of the steel sheet W, the V ₁
This shows a case where V ₂ is smaller than V ₂ (V ₂ <V ₁ ). The interval between the trajectories 91 of the spiral beam spot 83 is narrower than that in FIG. ₁ and P ₂ and the penetration region 89 effective for welding partially overlap.

FIG. 5C shows an example of the laser processing head 1.
The rotation speed of the optical axis 55 is the same as that in FIG.
This shows a case where the relative feed speed of the steel material W with respect to the optical axis 55 is V ₃ (about 300 mm / min) smaller than V ₂ (about 300 mm / min) (V ₃ <V ₂ ), and a spiral beam spot is shown. The interval between the trajectories 91 of the beam 83 is further narrowed, and the positions P ₁ and P _{2 of the} beam spot 83 and the penetration region 89 effective for welding completely overlap.

Therefore, when a high welding strength is required, as shown in FIG. 5C, the positions P ₁ and P _{2 of} the beam spot 83 and the penetration region 89 effective for welding.
However, a welding method that completely overlaps is appropriate. Further, when much larger weld strength is not required, as in FIG. 5 (b), the welding method of the position P ₁ and P ₂ and welding effective penetration area region 89 in the beam spot 83 partially overlaps Can be used. Further, when an appropriate strength is required at a high welding speed, a welding method as shown in FIG. 5A can be employed. 5A to 5C.
Since the minute beam spot 83 of the laser beam LB is rotated at the radius r (δ) as shown in FIG. 7, even if the welding gap fluctuates somewhat, good welding can be performed without generating welding defects.

Appropriate processing conditions in the above-mentioned welding are appropriately selected depending on the thickness and the material of the steel material to be welded and the required welding strength. According to the experiment using the above method, Laser power 1.6 kW, relative feed speed 500 mm / min to 1,000 mm / mi
In n, good welding was possible when the thickness of the steel sheet was at most about 3 mm and the welding gap was in the range of 4 mm to 5 mm. The thickness t of the optical flat 53
And the inclination angle α with respect to the optical axis 55 is α = 20 degrees ± 15 degrees and t = 5 ± 2.5 mm when used for surface modification centering on surface treatment such as welding or surface hardening. It is desirable.

FIG. 6 shows a second embodiment of the laser processing head 1 shown in FIG. 1, and shows only the optical system of the laser processing head. This laser processing head 93
A pair of prisms (optical wedges) 95 and 97 are disposed below the condenser lens 11 as a decentering optical system for decentering the laser beam with respect to the optical axis 55, instead of the optical flat 53, at a fixed interval D. It is arranged with open. The prisms (optical wedges) 95 and 97
Are provided so as to be rotatable about the optical axis 55 independently by drive motors M ₁ and M ₂ , respectively. Since the prisms (optical wedges) 95 and 97 have the same shape, the same portions are denoted by the same reference numerals. The first refracting surfaces 9 of the prisms (optical wedges) 95 and 97
9 and the second refracting surface 101, that is, the prism angle is θ
It is formed every time.

The prism (optical wedge) 95 is arranged such that the first refracting surface 99 of the prism (optical wedge) 95 is on the condenser lens side 11 and the first refracting surface 99 is perpendicular to the optical axis 55. It is arranged. Further, the prism (optical wedge) 97 provided at a certain interval D,
The second refracting surface 101 is arranged so as to face the second refracting surface 101 of the prism (optical wedge) 95.

In the above configuration, the prism (optical wedge) 95 and the prism (optical wedge) 97 are arranged as shown in FIG.
When the second refracting surface 101 of the prism (optical wedge) 95 and the second refracting surface 101 of the prism (optical wedge) 97 are positioned in parallel with each other as shown in FIG. The laser beam LB incident on the pair of prisms (optical wedges) 95 and 97 is refracted by the prisms (optical wedges) 95 and 97 as shown in FIG. The focal point can be moved eccentrically to a position offset rightward (in FIG. 6) by δ ′ from the axis 55.

Therefore, if the pair of prisms (optical wedges) 95 and 97 are synchronously rotated in the same direction by the drive motors M ₁ and M ₂ while maintaining the positional relationship as shown in FIG. The small beam spot 83 of the emitted laser can be rotated around the optical axis 55 with a rotation radius r = δ '. Also, the prism angles θ in the prisms (optical wedges) 95 and 97
If a different prism (optical wedge) is used, it is possible to change the radius of rotation r = δ ′. Furthermore, a prism (optical wedge) 95 and a prism (optical wedge)
The rotation trajectory of the beam spot 83 can be changed in various ways by making the rotation speed of the beam spot 83 different from that of the beam spot 97 or by reversing the rotation direction of the prism (optical wedge) 95 and the prism (optical wedge) 97.

The prism (optical wedge) 95
Alternatively, it is possible to decenter the laser beam with respect to the optical axis 55 even with only one 97.

A method of drawing a pattern on the surface of various materials with a laser beam using the laser processing head 93 having the above-described structure, and a laser decoration method will be described below.
As described above, the laser beam condensed by the condenser lens 11 is rotated at various rotational speeds at a rotational radius r = δ 'with respect to the axis 55 of the laser processing head 93 as described above, and at the same time, the workpiece is processed by the laser processing head. By moving the shaft 93 relative to the shaft center 55 at various speeds, FIG.
Various patterns as shown in (h) can be drawn on the surface of the workpiece.

For example, a wave-like pattern as shown in (a) or (e) of FIG. 7, a triangular wave-like pattern as shown in (b) to (e), a spiral (spiral) as in (g) or (h). ,
A dotted line as in (f), a thick straight line as in (k), and the like can be drawn. When drawing a thick straight line, the turning radius r =
If δ ′ is appropriately reduced and the rotation speed of the laser processing head 93 is increased, it is possible to draw a pattern. In addition,
The output of the laser in the laser decoration method can be generally performed at a lower output than the output of the material at the time of cutting.

Although the various patterns shown in FIG. 7 are all drawn in a straight line, an arbitrary curve can be obtained by appropriately moving the laser processing head or the material side in the X and Y axis directions. It is easily understood that various patterns can be decorated on the surface of the workpiece according to the above.

In the case where the workpiece is fed and cut in accordance with the above-described cutting principle, the relative cutting speeds on the left and right sides of the cutting width differ with the rotation of the laser beam. From this, in particular, the cutting of the right bank is better than that of the left bank, but the quality of cutting the lower surface of the left bank is poor. This tendency is remarkable in mild steel, and is not so noticeable in stainless steel. Therefore, mild steel requires a cutting method that makes use of one side of the product. It is conceivable that the above-described cutting characteristics can be dealt with by changing the motor for rotating and driving the laser beam to a DC motor and appropriately switching the cutting speed as needed.

FIGS. 8 and 9 show only the decentering optical system 53 of FIG. 1 described above.
1 shows an embodiment of the present invention.

The decentering optical system according to the second embodiment has
A condensing lens is used in place of the optical flat of the decentering optical system 53. A condensing lens 110 is provided above the rotary cylinder 35, and the optical axis of the lens is relative to the optical axis 55 of the laser beam LB. And provided so as to be rotatable by the motor 43.

The means for tilting and fixing the condenser lens 110 to the rotary cylinder 35 is provided, for example, with a hollow cylindrical lens support 111 fitted and connected to the upper hole of the rotary cylinder 35. The lens 11 is α
Hollow cylindrical lower spacer 113 that is supported at an angle
And a hollow cylindrical lens holder 115 for holding the periphery of the upper surface of the lens supported by the lower spacer 113 is similarly fitted and provided.
Flange 15 is screwed to the lens support 111.
Fixed at 2.

In order to make the inclination angle of the lower spacer 113 and the lens holder 115 coincide with each other, a key groove 117 is provided in the lens support 111, and a positioning pin 119 engaging with the key groove 117 is attached to the lower spacer 113 and the lens. It is provided on the retainer 115. Also, the condenser lens 1
The laser beam LB focused at 10 is provided so as to be focused at a position eccentric from the optical axis 55 by a minute distance δ of about 0.1 mm to several mm.

When the motor 43 is driven to rotate in the above configuration, the rotary cylinder 35 supporting the condenser lens 110 is rotated, so that the condensed laser beam has a radius r = δ about the optical axis 55. Will make a circular motion.

FIGS. 10 and 11 show only the decentering optical system 53 shown in FIG. 1 as in FIGS.
13 shows a third embodiment of the decentering optical system 53.

In the decentering optical system according to the third embodiment, the condensing lens 120 is provided above the rotary cylinder 35 so that the amount of eccentricity of the condensing lens optical axis with respect to the optical axis 55 can be adjusted. In addition, the motor 43 is provided so as to be rotatable by the motor 43.

The optical system support 121 is provided above the hollow cylindrical optical system support 121 fitted and fixed to the rotary cylinder 35.
A bottomed eccentric hole 123 having a diameter larger than the inner diameter of the hole is provided. The axis 125 of the eccentric hole 123 is provided so as to be eccentric from the axis 127 (concentric with the optical axis 55) of the optical system support 121 by an eccentric amount e.

An annular lens holder 129 is fitted into the eccentric hole 123 so as to be rotatable and fixed to the optical system support 121. The lens holder 129 is fitted to the lens holder 129 from the center of rotation of the lens holder 129, that is, the eccentric hole. Shaft center 12
5, the lens mounting seat 131 is further decentered by an eccentric amount e. And this lens mounting seat 13
1, the condenser lens 120 is fixed by a holding ring 133.

The means for rotating or fixing the lens holder 129 to the optical system support 121 can be provided by a set screw 135 provided on the optical system support 121 as shown in the figure. Further, the lens holder 129 can be rotated by using a plurality of pins 137 standing on the upper surface of the lens holder 129.

In the above configuration, the amount of eccentricity of the condensing lens 120 with respect to the axis 127 (concentric with the optical axis 55) is reduced from the amount of eccentricity of 0 by loosening the holding screw 135 and rotating the lens holder 129 appropriately. It can be adjusted in the range up to 2e. (FIGS. 10 and 11 show a state where the amount of eccentricity is 0.) When the amount of eccentricity is δ, if the motor 43 is driven to rotate, the rotating cylinder 35 supporting the condenser lens 120 rotates. The focused laser beam is transmitted through the optical axis 55.
Make a circular motion with a radius r = δ centered at.

Next, a laser piercing method using the laser processing head 1 will be described with reference to FIG.

FIG. 12 is an explanatory diagram of the output control of the pulse laser used for the laser piercing according to the present invention. In this output control, the pulse frequency and duty are set low at the start of piercing, and the piercing is performed by stepwise increasing the frequency and duty with the progress of piercing until the laser output reaches the command value. Things.

Therefore, the minute beam spot of the laser beam condensed by the laser processing head gradually cuts (evaporates) or removes a part of the cutting front (the area in the cutting process) of the steel plate while rotating. Since the depth of the cutting front is very small, assist gas such as oxygen is sufficiently supplied to the bottom of the cutting front, and the oxidation reaction is activated to generate reaction heat. Further, since the metal or the like melted by the assist gas is immediately discharged, the laser piercing of a thick steel plate having a thickness of about 25 mm becomes possible. Also, there is little scattering of spatter and little swelling around the piercing hole.

FIG. 13 shows test results of piercing using the laser processing head and the above-described pulse laser output control. The main processing conditions at this time are as follows.

Initial duty 10%, duty increment 1%, pulse frequency initial 70Hz, pulse frequency increment 1Hz, number of steps 23, step time 0.
1 second, beam rotation speed 500 rpm, laser output 3.6
kW (peak value), work material SUS304.

As shown in FIG. 13, according to the laser piercing method of the present invention, a good piercing is possible up to a plate thickness of 22 mm, whereas the conventional piercing method (laser beam non-rotation) is practical. 15m thick to withstand heavy use
m.

In the first embodiment, it is described by a cutting experiment that good cutting with a cutting width of 2 mm or less can be performed up to a maximum thickness of about 25 mm. The detailed conditions at this time are listed below.

In this description, the processing will be described using a processing head 140 shown in FIG. A lens holder 142 for holding the concave lens 141 is provided above the processing head 140. Further, between the nozzle part 143 and the concave lens 141, a focus lens part 144 formed of a group lens is provided. A window 145 is provided above the nozzle section 143.

The focus lens unit 144 is configured to move up and down along the optical axis 55 by a focus lens drive mechanism (not shown). Also, the nozzle part 143
Above the window 145 of the optical flat 5
3 is provided so as to be interlocked with the nozzle unit 143. Further, the nozzle unit 143 is provided with a nozzle driving mechanism (not shown).
Thus, it is configured to move up and down along the optical axis 55.

When such a processing head 140 is used, the focal length can be changed as shown in FIG.

FIG. 15 shows that the focal length f can be changed to 7.5 inches by moving the focus lens 144 and the nozzle 143 up and down.

The focus lens 144 or the nozzle 14
In the cutting experiment when moving No. 3 up and down, under the following processing conditions, good cutting was possible in a steel plate having a thickness of up to about 25 mm.

That is, a laser output of 1.6 kW or 2
kW, relative feed rate 200 mm / min to 400 mm
In the range of / min, beam mode is a Gaussian mode (single mode) or near Gaussian mode, the mode coefficient M ² (M square) is in the Gaussian distribution of the TEM ⁰⁰ 1.00, the TEM ₀₁ ^* (zero position Star) 1.75 or less. Even in mixed mode,
It is necessary that at least pseudo Gauss is formed. In the case of the multi-mode, the dross is attached more or the cutting is incomplete.

The F number (focal length f / incident beam diameter D) of the condensing lens is also an important factor in determining the condensing property in the cutting method of the present invention. For the F number for cutting, D is a value determined by the optical path length of the light emitted from the oscillator, and if this is DL,

(Equation 1) Given by

Here, Z is the optical path length λ is the wavelength of the laser beam ωo is the radius at the narrowest point where Z = 0 called the beam waist f is the focal length Further, the focal length f is

(Equation 2) Indicated by

In particular, DL is set to 14 mm (1/1 of the Gaussian distribution).
and e diameter of ²⁾ before and after, F-number in the case where the f front and rear 190mm will be able cut from 11.5 to 14.5, and the maximum 25mm about steel in the F-number.

When cutting steel having a maximum of about 25 mm with an F number of 11.5 to 14.5, the focused beam spot diameter (heat source) is about φ0.4 mm (e).
-2 diameter). In addition, the value (width when moving) converted by the cutting width of the material is 0.3 to 0.7.
mm. The radius of rotation of the beam spot is within r = 0.5 mm regardless of the thickness of the cut plate. In addition,
The focal position was set inside the cutting material.

It is important that the assist gas supplied to the assist gas nozzle is supplied so as not to generate turbulence in the nozzle. The volume of the container provided with the nozzle is required to be at least 30 cm 3, and about 100 cm 3. It is desirable to spray from the nozzle at the tip with the required pressure from the state where the container is filled.

Generally, the relationship among the gas flow rate Gf, the nozzle diameter Nd, and the gas pressure P in the container is as shown in FIG.

That is, the gas flow rate Gf in FIG.
Is

(Equation 3) Where Gf is the flow rate of the assist gas Gp is the pressure of the assist gas C is a constant n is the flow rate increase rate or ratio (decimal number display) when an arbitrary nozzle diameter is adopted based on the nozzle diameter φ = 1.0 a is a coefficient Is required.

The gas flow rate is 60 to 260 NL / mi.
When cutting in the range of n, as shown in FIG. 16, the gas pressure in the above-described container is desirably about 0.2 to 0.6 bar, and may be at most within 1.0 bar. The nozzle diameter is desirably 2 to 4 mm.

Further, the desired amount of eccentricity δ can be obtained by changing the thickness t (mm) of the optical flat 53 and the angle α with respect to the optical axis 55. As a result, the thickness of the steel plate
When cutting a thick plate of about 25 mm, α = 10 degrees ± 5
It is desirable that t = 5 ± 2.5 mm.

That is, when cutting a steel having a maximum of 25 mm at an output of 2 kW, the optical flat 53 is eccentric while the F number, spot diameter, turning radius, chamber volume, gas pressure, and nozzle diameter are set as described above. The work is irradiated with a laser beam. For this reason, the focal point is deeply formed in the work, and the focal point is shaken to enlarge the processing hole, and the assist gas flows into the processing hole to further promote the dissolution, so that the maximum thickness is 25 mm. Even with this, cutting is performed with high precision.

[0122]

According to the first to seventh aspects of the present invention, in a laser processing machine having a laser output of 2 kW class, cutting with practical accuracy in a thick steel plate having a thickness of about 19 mm to 25 mm is performed. It can be carried out.

According to the invention as set forth in claims 8 to 10, good welding can be performed even in a wide welding gap of about 4 mm to 5 mm, and the allowable range of the gap dimensional error in butt welding is reduced. It becomes large and gap management becomes easy.

According to the eleventh to thirteenth aspects, various curves such as straight lines and wide straight lines, curved lines, spiral curves, and the like are decorated (drawn) on the surface of the workpiece. Can be.

According to the fourteenth aspect, 2 kW
The laser piercing of a thick steel plate of about 25 mm is also possible with a middle and low power laser processing machine before and after.

According to the invention of claims 15 to 20, a laser piercing of a thick steel plate having a thickness of about 25 mm can be performed even with a medium power laser processing machine of about 2 kW, There is little scattering of molten oxide) and no bulge is formed around the pierced hole.

According to the twenty-first to twenty-fifth aspects of the present invention, in a laser processing machine with a laser output of 2 kW class, cutting with practical accuracy is performed on a thick steel plate having a thickness of about 19 mm to 25 mm. Becomes possible.

According to the twenty-sixth aspect, the allowable range of the dimensional error of the gap in the butt welding is increased, and the gap management becomes easy.

According to the twenty-seventh and twenty-eighth aspects, the laser beam focused by the eccentric optical system is rotated and the workpiece is moved with respect to the optical axis of the laser processing head. Various patterns can be decorated (depicted) on the surface of the workpiece.

[Brief description of the drawings]

FIG. 1 is a first embodiment of a laser processing head according to the present invention.

FIG. 2 is an explanatory diagram of an eccentric optical system (optical flat) used in a laser processing head according to the present invention.

FIG. 3 is an explanatory view of the principle of the laser cutting method according to the present invention.

4 is an explanatory view of the principle of the laser cutting method according to the present invention, and is a cross-sectional view taken along the line IV-IV in FIG.

FIG. 5 is an explanatory view of the principle of the laser welding method according to the present invention.

FIG. 6 is a second embodiment of the laser processing head according to the present invention.

FIG. 7 is an example in which various patterns are decorated on the surface of a workpiece by the laser decoration method according to the present invention.

FIG. 8 shows a second embodiment of an eccentric optical system for a laser processing head according to the present invention.

FIG. 9 is a sectional view taken along the line IX-IX of FIG. 8;

FIG. 10 shows an optical system for decentering a laser processing head according to a third embodiment of the present invention.

FIG. 11 is a sectional view taken along the line XI-XI in FIG. 10;

FIG. 12 is an explanatory diagram of output control of a pulse laser used for a laser piercing according to the present invention.

FIG. 13 shows a test result of piercing by a laser piercing according to the present invention.

FIG. 14 is an explanatory diagram of a focus changeable head.

FIG. 15 is an explanatory diagram illustrating the relationship between the focal length and the amount of movement when the head of FIG. 14 is used.

FIG. 16 is an explanatory diagram illustrating a relationship among a gas flow rate, a gas pressure, and a nozzle diameter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Laser processing head 3 Lens unit 5 Lens unit mounting member 7 Screw hole 11, 110, 120 Condensing lens 13 Coolant flow path 15 Coolant supply port 17 First cylinder 21 Second cylinder 29 Ring member 33 Bearing 34 Bearing Hold down 35 Rotating cylinder 37 Followed pulley 39 Motor bracket 41 Motor base 43 Motor 47 Driving pulley 49 Driving belt 51 Window 53 Optical flat 55 Optical axis 57 Optical flat support 59 Third cylindrical body 63 Window 65 Fourth cylindrical body 71 Push screw 73 Flange fixing member 75 Assist gas nozzle 77 Assist gas injection port 79 Nozzle tip 80 Normal line 81 Cutting line 83 Beam spot 85 Cutting front (area in the cutting process) 87 Welding line 89 Penetration area area 91 Bee Spot trajectory 93 Laser processing head 95, 97 Prism (optical wedge) 99 First refraction surface 101 Second refraction surface 111 Lens support 113 Lower spacer 115 Lens press 121 Optical support 129 Lens holder B Cutting width D Interval LB Laser Beam e Eccentricity f Focal length I, I ₁ , I ₂ Incident angle R ₁ , R ₂ Refraction angle r Radius t Thickness α Angle θ Prism angle δ, δ ′ Eccentricity ΔL Feed amount ΔH Depth W, W ₁ , W ₂ steel plate

Claims (28)

[Claims] 1. An eccentric optical system for eccentrically deviating a laser beam condensed by a laser beam condensing optical system of a laser processing head from an optical axis of the condensing optical system. At the same time as rotating the small laser beam spot focused at the focal position around the axis of the focusing optical system, the assist gas from the assist gas nozzle of the laser processing head is applied to the cutting portion of the workpiece. A laser cutting method, comprising cutting the workpiece by supplying and moving the optical axis and the workpiece relative to each other. 2. The optical system according to claim 1, wherein the decentering optical system is an optical flat having a plate thickness t provided rotatably at an inclination angle α on an optical axis of the condensing optical system. Laser cutting method. 3. The laser cutting method according to claim 2, wherein the inclination angle α is 10 degrees ± 5 degrees and the plate thickness t is 5 mm ± 2.5 mm. 4. The condensing optical system is provided with a condensing lens decentered with respect to an incident beam optical axis, and is provided so as to be rotatable about the incident beam optical axis. The laser cutting method according to claim 1, wherein the laser cutting method is an optical system. 5. The condensing optical system includes a converging lens provided at an inclination angle α with respect to an optical axis of an incident beam and rotatably provided around the optical axis of the incident beam. The laser cutting method according to claim 1, wherein the laser cutting method is an optical system. 6. The condensing optical system has an F number that is about twice as large as when cutting a thin plate having a maximum of about 16 mm, and the gas supplied from the assist gas nozzle has a gas flow rate of 60 to 300 Nl / min. The laser cutting method according to claim 1, wherein the assist gas is a pseudo Gaussian assist gas. 7. The gas pressure of the assist gas nozzle is set to 0.1.
2. The laser cutting method according to claim 1, wherein the laser cutting speed is set to 2 to 0.6 bar. 8. An eccentric optical system for eccentrically deviating a laser beam focused by a laser beam focusing optical system of a laser processing head from an optical axis of the focusing optical system. At the same time as rotating the minute laser beam spot focused at the focal position about the axis of the focusing optical system, the optical axis of the laser processing head is relatively aligned along the welding line of the workpiece. A laser welding method, characterized in that a material to be welded is welded by moving the laser beam. 9. The optical system according to claim 8, wherein the decentering optical system is an optical flat having a plate thickness t provided rotatably at an inclination angle α on an optical axis of the condensing optical system. Laser welding method. 10. The laser welding method according to claim 9, wherein the inclination angle α is 20 degrees ± 15 degrees and the thickness t is 5 mm ± 2.5 mm. 11. An eccentric optical system for eccentrically deviating a laser beam focused by a laser beam focusing optical system of a laser processing head from an optical axis of the focusing optical system,
A minute laser beam spot decentered by the eccentric optical system and condensed at the focal position is rotated about the axis of the converging optical system, and at the same time, the workpiece is moved to the optical axis of the laser processing head. A laser decorating method characterized by drawing a pattern on the surface of a workpiece by relatively moving the workpiece. 12. The optical system according to claim 11, wherein the decentering optical system includes at least one or more prisms (optical wedges) rotatably provided around the optical axis of the light collecting optical system. Laser decoration method described in 1. 13. The prism (optical wedge) is composed of two prisms (optical wedge) provided at a fixed distance, and each of the prisms (optical wedge) is independently rotatable in forward and reverse directions. The laser decorating method according to claim 12, wherein the laser decorating method is provided. 14. An eccentric optical system for eccentrically deviating a laser beam focused by a laser beam focusing optical system of a laser processing head from an optical axis of the focusing optical system,
At the same time as rotating the minute laser beam spot decentered by the eccentric optical system and condensed at the focal position about the axis of the converging optical system, assist gas is supplied from the assist gas nozzle of the laser processing head. A laser piercing method, wherein the laser piercing method comprises supplying the material to a cut portion of the work material and performing through-hole processing in the work material. 15. A pulse laser is used for a laser beam incident on the laser beam focusing optical system, and the frequency and pulse duty of the pulse laser are set low at the start of piercing, and the frequency is set as piercing proceeds. The laser piercing method according to claim 14, wherein the piercing is completed by increasing stepwise and the pulse duty until the laser output reaches the command value. 16. The optical system according to claim 14, wherein the decentering optical system is an optical flat having a plate thickness t provided rotatably at an inclination angle α on the optical axis of the condensing optical system.
The laser piercing method according to claim 15. 17. The method according to claim 17, wherein the condensing lens is provided so as to be decentered with respect to the optical axis of the incident beam, and the optical axis of the incident beam is rotatably provided about the axis. The laser piercing method according to claim 14, wherein the laser piercing method is used. 18. The condensing lens is provided at an inclination angle α with respect to an incident beam optical axis, and is rotatably provided around the incident beam optical axis, and the condensing lens itself is an optical system for decentering. The laser piercing method according to claim 14, wherein: 19. The condensing optical system has an F number that is about twice that of a thin plate having a maximum thickness of about 16 mm, and the gas supplied from the assist gas nozzle has a gas flow rate of 60 to 300 Nl / min. 15. A pseudo Gaussian assist gas.
The described laser piercing method. 20. The laser piercing method according to claim 14, wherein the gas pressure of the assist gas nozzle is set to 0.2 to 0.6 bar. 21. A laser processing head of a laser processing apparatus, wherein an eccentric optical system rotatably driven for eccentricity of a laser beam from an optical axis of the optical system for focusing is provided below the optical system for focusing the laser beam. A laser processing head, further comprising an assist gas nozzle for passing the laser beam from the eccentric optical system and simultaneously injecting the assist gas coaxially. 22. The optical system according to claim 21, wherein the decentering optical system is an optical flat having a plate thickness t provided rotatably at an inclination angle α on an optical axis of the condensing optical system. Laser processing head. 23. The laser processing head according to claim 22, wherein the inclination angle α is 10 degrees ± 5 degrees and the plate thickness t is 5 mm ± 2.5 mm. 24. The condensing optical system according to claim 1, wherein the condensing lens is provided so as to be decentered with respect to the incident beam optical axis, and the incident beam optical axis is rotatably provided about the axis. 22. The laser processing head according to claim 21, wherein the laser processing head is an optical system. 25. The condensing optical system is provided with a condensing lens at an inclination angle α with respect to the incident beam optical axis, and is provided rotatably about the incident beam optical axis. 22. The laser processing head according to claim 21, wherein the laser processing head is an optical system for use. 26. The laser processing head according to claim 22, wherein the inclination angle α is 20 degrees ± 15 degrees and the plate thickness t is 5 mm ± 2.5 mm. 27. The decentering optical system comprises at least one or more prisms (optical wedges) provided rotatably about the optical axis of the condensing optical system as an axis. The laser processing head according to 1. 28. The prism (optical wedge) is composed of two prisms (optical wedge) provided at a fixed distance, and each of the prisms (optical wedge) is independently rotatable in the forward and reverse directions. The laser processing head according to claim 27, wherein the laser processing head is provided.