JPH07236987A - Method for cutting with laser beam and device therefor - Google Patents

Abstract

PURPOSE:To obtain a method for cutting with laser beam and device therefor to realize a high quality cutting without generating a rough cutting surface by eliminating the stagnation of molten matter at a lower part of the cutting surface of a work to be cut. CONSTITUTION:Cutting is executed while vibrating the irradiating position of a laser beam 1 or the irradiating diameter against the work 6 to be cut during cutting, in order to perform the cutting, a moving means 9 which relatively moves the work 6 to be cut and the laser beam 1, a beam diameter regulating means, or a changeover means is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser cutting method and apparatus for irradiating a workpiece with a laser beam and cutting the workpiece with the energy of the laser beam.

[0002]

2. Description of the Related Art FIG. 27 is a schematic diagram for explaining a conventional laser cutting method. In FIG. 27, 101 is a laser beam for irradiating a thick workpiece 106, 103 is a cutting front surface, and 107 is a laser beam 101. A processing lens for condensing the light, and 135 denotes the assist gas 121 for the laser beam 101
Nozzles sprayed onto the irradiated cutting portion 102a, and the arrow indicates the moving direction of the workpiece 106. In FIG. 27, the laser beam 1 is reflected by the processing lens 107 having a long focal length.
01 is focused, the focus position O is separated from the surface of the workpiece by a distance K, and the beam diameter on the surface of the workpiece is expanded and cut. In this conventional laser cutting method,
When the plate thickness of the workpiece 106 becomes thick, the workpiece 10
Even if the processing lens 107 having a long focal length is used so that the laser energy is effectively transmitted to the lower part of the laser beam 6, or the beam diameter incident on the processing lens 107 is made small to deepen the focal depth, the cutting groove is stably formed. Can no longer be formed. For example, when the workpiece 106 is mild steel, the laser beam 101 of 3 kW is very difficult to cut when the plate thickness exceeds 22 mm, and even if the laser beam 101 can be cut, as shown in FIG. In the above, the cut surface roughness was extremely rough like the lower scratches 122 as compared with the upper scratches 104, and the problem of deterioration of the processed product occurred.

The reason why such a situation occurs is that the focused spot diameter of the beam becomes too large and the laser energy incident on the deep portion of the cutting groove decreases because the depth of focus is deepened. As the focused spot diameter increases,
As shown in FIG. 9, the cutting groove 102 below the processing threshold value
The energy of the beam spot peripheral portion 101a that does not enter the inside is large, and the energy of the beam spot central portion 101b that enters the cutting groove 102 is small. For this reason, the amount of laser incident heat into the cutting groove 102 decreases, insufficient heat input occurs in the deep portion of the cutting groove, and the temperature of the melt decreases and the viscosity increases.

As a result, the molten material is retained in the lower part of the cut surface of the workpiece, and the cut surface becomes very rough. Further, the depth of the cutting groove becomes deep and the action of removing the molten material by the assist gas flow is reduced in the deep portion of the groove, so that the molten material stays in the lower part of the cut surface of the workpiece, and the cut surface roughness becomes very rough. Has become a factor of becoming.

In this case, if the laser beam 101 is defocused and the groove width is widened to increase the action of removing the molten material by the assist gas flow at the deep portion of the groove, the beam spot diameter is widened. The laser energy incident on the inside is reduced, which is not suitable.

Further, even in the case of a medium-thickness work piece that can be laser-cut, for example, with mild steel, the plate thickness is 22 mm.
Even in the following cases, the roughness of the cut surface becomes lower in the lower portion as compared with the upper portion of the cut surface, similarly to the workpiece having a plate thickness of 22 mm or more. In particular, there is a problem that the cut surface roughness is reduced due to the burn-through of the apex of the corner that occurs when the corner is cut.

As a laser cutting method for solving these problems, for example, there is a laser cutting method disclosed in Japanese Patent Application Laid-Open No. 4-284990. In this laser cutting method, the cross-sectional shape of the laser beam on the surface of the workpiece is elongated in the cutting direction, and at a predetermined depth or more inside the workpiece, the beam is elongated in the direction orthogonal to the cutting direction. The groove width in the vicinity of the back surface of No. 1 is widened to improve the retention of the melt and the roughness of the cut surface at the lower part of the cut surface of the workpiece.
However, with this method, although the reduction of the cut surface roughness can be improved, the groove width in the depth direction of the cutting groove changes greatly, and thus the cut surface after processing is not flat. Therefore, there is a problem that the assembling accuracy and weldability of the parts after cutting are deteriorated.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and claims
An object of the invention described in 11 is to obtain a laser cutting method capable of eliminating retention of a molten material in a lower portion of a cut surface of a workpiece and realizing high-quality cutting with no cut surface roughness.

It is an object of the present invention to provide a laser cutting device capable of solving the shortage of heat input in the deep portion of the cutting groove and realizing high quality cutting without lowering the roughness of the cutting surface.

It is an object of the present invention to provide a laser cutting method capable of improving the action of removing a molten material and realizing high quality cutting with no cut surface roughness.

[0011]

According to a first aspect of the present invention, there is provided a laser cutting method, wherein a workpiece and a laser beam are moved relative to each other during cutting so that the laser beam is moved relative to the workpiece. It vibrates the position or the beam diameter.

In the laser cutting method according to the second aspect of the present invention, the vibration frequency of the laser beam is calculated from the pitch of the scratches formed on the cut surface of the workpiece and the cutting speed when the laser beam is not vibrated. It is set to be higher than the streak generation frequency.

In the laser cutting method according to the third aspect of the present invention, the vibration direction of the laser beam is made parallel to the cutting proceeding direction.

According to a fourth aspect of the present invention, there is provided a laser cutting method, wherein a vibration amplitude parallel to a cutting proceeding direction of a laser beam is
The value is set to be smaller than the value calculated from the difference between the cutting groove lengths on the front surface and the back surface of the workpiece when the laser beam is not vibrated and the cutting groove width on the surface of the workpiece.

In the laser cutting method according to the fifth aspect of the present invention, the vibration direction of the laser beam is orthogonal to the cutting proceeding direction.

According to a sixth aspect of the present invention, there is provided a laser cutting method, wherein a vibration amplitude of a laser beam orthogonal to a cutting proceeding direction is:
The width is set to be smaller than the cutting groove width on the surface of the workpiece.

According to a seventh aspect of the present invention, there is provided a laser cutting method in which a central axis of a spot of a laser beam is rotationally moved on a radius of rotation on the surface of the workpiece.

According to a eighth aspect of the present invention, there is provided a laser cutting method in which a component parallel to a cutting proceeding direction in which a laser beam is rotationally moved is cut groove lengths of front and back surfaces of the workpiece when the laser beam is not rotated. It is set to be smaller than a value calculated from the difference in depth and the cutting groove width on the surface of the workpiece, and the component orthogonal to the cutting proceeding direction is set to be smaller than the width of the cutting groove on the surface of the workpiece.

According to a ninth aspect of the laser cutting method of the present invention, the rotational movement direction of the laser beam is set in a direction opposite to the direction in which the cutting proceeding direction changes.

In the laser cutting method according to the tenth aspect of the present invention, the oscillation direction of the laser beam is made parallel to the incident axis direction of the laser beam.

In the laser cutting method according to the eleventh aspect of the present invention, the maximum value of the laser beam diameter on the surface of the workpiece is set smaller than about 1.5 times the width of the cutting groove.

According to a twelfth aspect of the present invention, there is provided a laser cutting device, wherein, even if a cutting proceeding direction is changed, an angle of a vibration direction of the laser beam with respect to the workpiece is kept constant. A moving means for moving the laser beam relatively is provided.

The laser cutting device according to the thirteenth aspect of the present invention comprises a beam diameter control means for changing the laser beam diameter on the surface of the workpiece.

A laser cutting apparatus according to the fourteenth aspect of the present invention comprises a plurality of laser beam transmission lines having different transmission distances to the surface of the workpiece, and switching means for switching the laser beam transmission lines during processing. It is a thing.

The laser cutting method according to the fifteenth aspect of the invention is to cool the assist gas and blow it onto the cutting portion.

In the laser cutting method according to the sixteenth aspect of the present invention, the cooled assist gas is blown onto the cutting portion from behind the cutting portion irradiated with the laser beam in the cutting proceeding direction.

[0027]

The laser beam according to the invention of claim 1 is
By vibrating the position with respect to the work piece or the beam diameter, it is possible to increase the laser energy irradiated to the deep part of the cutting groove, eliminate the insufficient heat input in the deep part of the cutting groove, raise the temperature of the melt and increase the viscosity. Get lower. as a result,
In the lower part of the cut surface of the work piece, the molten material is prevented from staying, and high-quality cutting is realized without a decrease in cut surface roughness.

In the laser beam according to the second aspect of the present invention, the vibration frequency is set to be higher than the generation frequency of the scratches generated on the cut surface, so that the vibration of the laser beam can prevent the cutting phenomenon from becoming unstable.

In the invention of claim 3, the laser beam is oscillated parallel to the cutting proceeding direction, and in the invention of claim 4, the vibration amplitude is set to be smaller than the width of the cutting groove so that the power is deep in the cutting groove. The vicinity of the central axis of the high-density beam is directly irradiated, the insufficient heat input in the deep part of the cutting groove is resolved, the temperature of the melt rises, and the viscosity becomes low. As a result, in the lower part of the cut surface of the work piece, the retention of the melt is eliminated, and high-quality cutting without lowering the roughness of the cut surface is realized.

According to the invention of claim 5, the laser beam vibrates a beam having a small focused spot diameter in a vertical direction orthogonal to the cutting proceeding direction, and in the invention of claim 6, the vibration amplitude is set to the cutting groove width. By making the setting smaller, the laser energy incident on the groove and the power density P of the laser increase, the insufficient heat input in the deep portion of the cutting groove is eliminated, the temperature of the melt rises, and the viscosity becomes low. As a result, in the lower part of the cut surface of the work piece, the retention of the melt is eliminated, and high-quality cutting without lowering the roughness of the cut surface is realized.

In the laser beam according to the invention described in claim 7, a beam having a small focused spot diameter is rotated, and in the invention according to claim 8, the component parallel to the cutting proceeding direction of the rotation diameter is defined by the length of the cutting groove. And the width and the component orthogonal to the cutting direction is smaller than the cutting groove width, the effect of vibrating the beam parallel to the cutting direction, and the beam orthogonal to the cutting direction. Due to the effect of vibrating, the lack of heat input in the deep part of the cutting groove is resolved,
The temperature of the melt rises and the viscosity decreases. As a result, the retention of the melt is eliminated in the lower part of the cut surface of the workpiece,
A high-quality cutting that does not reduce the cut surface roughness is realized.

In the laser beam according to the ninth aspect of the invention, since the rotational movement direction is opposite to the change of the cutting proceeding direction, the melt can be prevented from flowing to the corner edge portion, and the temperature of the corner edge portion can be prevented. The rise can be suppressed.
As a result, burn-through at the corner edges is eliminated, and high-quality corner cutting that does not reduce the cut surface roughness is realized.

According to the tenth aspect of the invention, the laser beam oscillates the focal position in the direction of the incident axis of the laser beam. In the eleventh aspect of the invention, the maximum value of the laser beam diameter is approximately 1.5 of the cutting groove width. By setting it smaller than double, the cutting groove width is specified near the maximum beam diameter, and when the beam diameter is less than that, all the laser energy enters the cutting groove and the insufficient heat input in the deep cutting groove is eliminated. , The temperature of the melt rises and the viscosity decreases. As a result, in the lower part of the cut surface of the work piece, the retention of the melt is eliminated, and high-quality cutting without lowering the roughness of the cut surface is realized.

In the moving means according to the twelfth aspect of the invention, even if the cutting advancing direction changes, the angle between the cutting advancing direction and the vibration direction of the laser beam on the surface of the workpiece is always kept constant. Insufficient heat input in the deep part of the cutting groove is eliminated, and high quality cutting of a shape with no reduction in cut surface roughness is realized.

The beam diameter control means in the thirteenth aspect of the invention changes the beam diameter on the surface of the workpiece, and in the fourteenth aspect of the invention the beam diameter is changed by switching the laser beam transmission path by the switching means. By
The cutting groove width is specified near the maximum beam diameter, and when the beam diameter is less than that, all the laser energy enters the cutting groove, the insufficient heat input in the deep cutting groove is resolved, and the temperature of the melt rises. The viscosity becomes low. As a result, in the lower part of the cut surface of the work piece, the retention of the melt is eliminated, and high-quality cutting without lowering the roughness of the cut surface is realized.

By cooling the assist gas in the invention according to the fifteenth aspect, the straightness increases and the action of removing the molten material improves. As a result, in the lower part of the cut surface of the work piece, the retention of the melt is eliminated, and high-quality cutting without lowering the roughness of the cut surface is realized.

The assist gas according to the sixteenth aspect of the invention is sprayed onto the cutting portion from behind the cutting portion irradiated with the laser beam in the cutting direction, so that the laser beam does not pass through the assist gas blowing nozzle. The degree of freedom in nozzle design is expanded, and the assist gas flow rate can be improved. As a result, in the lower part of the cut surface of the work piece, the retention of the melt is eliminated, and high-quality cutting without lowering the roughness of the cut surface is realized.

[0038]

【Example】

Example 1. FIG. 1 is a schematic view showing a laser cutting method according to an embodiment of the invention described in claims 1 to 4. In FIG. 1, reference numeral 1 is a laser beam, and 2 is a cutting groove formed in the workpiece 6. In the present Example 1, mild steel having a thickness of 4.5 mm, 12 mm, and 25 mm was used as the workpiece 6, the laser beam 1 was a continuous wave output of 1.5 kW, 1.75 W, and 3 kW, and the focal length was 190.5 mm. ZnSe lenses (not shown) of 0.5 mm from the surface of the workpiece, respectively.
The surface of the workpiece was irradiated so as to focus on 5 mm and 1.5 mm. Cutting speed is 2.5m / min, 1.0m / min
Min., 0.5 m / min., And at this time, the nozzle base pressure was 1.0 kgf / cm ² , 0.6 kgf / cm ² , 0. 0, from a nozzle (not shown) coaxial with the laser beam 1 and having a hole diameter of 2 mm. 5
Oxygen as an assist gas was blown to the cut portion at a pressure of kgf / cm ² . This laser beam 1 was oscillated parallel to the cutting advancing direction indicated by the arrow on the surface of the workpiece using a beam scanner (not shown) installed 500 mm above the surface of the workpiece. By such an operation, as shown in FIG. 2, the vicinity of the central axis of the beam with high power density is directly irradiated to the deep portion of the cutting groove, and the heat input to the lower portion of the workpiece 6 increases. As a result, the retention of the melt was eliminated, and high-quality cutting with no reduction in cut surface roughness was realized. In the figure, 3 is a cutting front surface.

FIG. 3 shows the relationship between the beam vibration frequency F and the cut surface roughness R below the cut surface for mild steel materials having plate thicknesses of 4.5 mm, 12 mm, and 25 mm when the beam vibration amplitude is 0.3 mm. FIG. As is clear from FIG. 3, the cut surface roughness R sharply deteriorates when the frequency F reaches a certain frequency, and the roughness R sharply improves at frequencies higher than that before the deterioration and becomes saturated when the frequency becomes high to some extent. To do. In the first embodiment, the frequency at which the roughness R sharply deteriorates is about 250 Hz when the plate thickness is 4.5 mm, and the plate thickness is 12 mm.
Was about 100 Hz, and a plate thickness of 25 mm was about 50 Hz. This value is calculated from the pitch P of the scratches 4 formed on the cut surface and the cutting speed V when the laser beam 1 shown in FIG. 4 is not oscillated and the generation frequency H of the scratches 4 = P / V.
Was almost consistent with. The pitch P and the cutting speed V of the striations 4 differ depending on the material of the workpiece, the plate thickness, and the processing shape, but in any case, the striations 4
When the vibration frequency of the laser beam 1 was set to be higher than the generation frequency of, the effect of improving the cut surface roughness was obtained. FIG. 5 shows a plate thickness of 4.5 mm, 12 mm, and 25 as a workpiece.
Beam frequency of 300H for each mm steel
It is a figure which shows the relationship between the amplitude A on the surface of a to-be-processed object of beam vibration at z, 200 Hz, and 200 Hz, and the cut surface roughness R of the cut surface lower part. The cutting surface roughness R is improved to a certain value, but the cutting surface roughness R has an amplitude value for each plate thickness.
The improvement effect of is not seen, and the roughness is worse than when the beam does not vibrate, that is, at the point O on the horizontal axis.

In this embodiment, the value of this amplitude is 4.5 mm.
About 0.4 mm for mm, about 1.0 m for 12 mm plate thickness
m and plate thickness 25 mm were about 1.5 mm. This value is represented by the difference B between the upper and lower portions of the cutting front surface 3 when the beam is not oscillated as shown in FIG. 6 and the distance D between the cutting front surface 3 and the beam center O on the workpiece surface (on the workpiece surface). It is calculated from (B-W / 2) /
It almost agrees with the value C of 2. FIG. 7 is a processing condition diagram showing the delay of the cutting front surface 3 with respect to the plate thickness, the cutting groove width W, and the calculated value C.

Even if the beam amplitude on the surface of the workpiece is the same, the delay B of the cutting front surface 3 and the cutting groove width W differ depending on the material of the workpiece, the plate thickness, and the machining shape. In any case, the beam is smaller than the calculated value C calculated from the difference B between the upper and lower portions of the cutting front surface 3 when the laser beam 1 is not vibrated and 1/2 of the cutting groove width W on the surface of the workpiece. When the amplitude of is set, the cut surface roughness R
The improvement effect of was obtained.

Example 2. FIG. 8 is a schematic view showing a laser cutting method according to an embodiment of the invention described in claims 5 and 6,
The same parts as those in FIG. In the second embodiment, a laser beam 1 is installed 500 mm above the surface of the workpiece, and a beam scanner (not shown) is used to generate frequencies of 300 Hz, 200 Hz and 2 Hz, respectively.
At the frequency of 00 Hz, the surface of the workpiece is oscillated in the vertical direction orthogonal to the cutting direction, as shown in FIG. P increases. Therefore, insufficient heat input in the deep portion of the cutting groove is eliminated, the temperature of the melt rises, and the viscosity becomes low. As a result, the material and thickness of the workpiece 6,
By setting the output of the laser beam 1, the cutting speed, the blowing pressure of oxygen as an assist gas, etc. to be the same as those in the first embodiment, the retention of the melt is eliminated, and high-quality cutting without lowering the cut surface roughness is achieved. It was realized.

FIG. 10 shows a plate thickness of 4.5 in the second embodiment.
FIG. 11 is a diagram showing the relationship between the amplitude A of the beam vibration and the cut surface roughness R of the cut surface lower portion on the surface of the workpiece of mm, 12 mm, and 25 mm of the mild steel material, and as is clear from FIG. R is improved within a certain range of the amplitude A. In Example 2, the plate thickness of 4.5 mm is 1.5 mm or less, and the plate thickness is 12
mm is about 1.2 mm or less, 25 mm thickness is about 1.0
It was less than mm. This upper limit is approximately equal to 1/2 of the cutting groove W.

Even if the amplitude A of the laser beam 1 is the same, the cutting groove width W varies depending on the material, plate thickness, and processing shape of the workpiece, but in any case, the cutting width W
When setting the beam amplitude within the range of less than / 2,
The effect of improving the cut surface roughness was obtained.

Example 3. FIG. 11 is a schematic view showing a laser cutting method according to an embodiment of the invention described in claims 7 and 8. In FIG. 11, 1 is a laser beam, and 2 is a cutting groove formed in the workpiece. In the third embodiment, the workpiece 6 is made of mild steel having a thickness of 4.5 mm, 12 mm and 25 mm, and the laser beam 1 has a power of 1.5 kW and a power of 1.75 k, respectively.
With a continuous wave output of W and 3 kW, a ZnSe lens (not shown) having a focal length of 190.5 mm (not shown) is used to focus on 0.5 mm, 1.5 mm, and 1.5 mm above the surface of the workpiece. The surface of the object was irradiated. Cutting speed is 2.5m each
/ Min, 1.0 m / min, 0.5 m / min. At this time, from a nozzle (not shown) having a hole diameter of 2 mm which is coaxial with the laser beam 1,
Nozzle source pressure is 1.0 kgf / cm ² and 0.6 kgf, respectively
/ Cm ² , 0.5 kgf / cm ² , and oxygen as an assist gas was blown to the cut portion. The laser beam 1 was set up at a frequency of 300 by using two beam scanners (not shown) installed 500 mm above the surface of the workpiece.
It was rotated on the surface of the workpiece at Hz, 200 Hz, and 200 Hz. By such an operation, the amount of heat input to the lower portion of the workpiece 6 is increased, so that the retention of the molten material is eliminated, and high quality cutting without lowering the roughness of the cut surface is realized. In the third embodiment, by satisfying the condition of the vibration amplitude of the laser beam 1 on the surface of the workpiece described in the first and second embodiments, the proper radius range of the rotational movement is determined. it can. That is, the length of the component of the radius of gyration on the surface of the work piece in the direction parallel to the cutting proceeding direction is determined by the difference B between the upper and lower parts of the cutting front surface when the laser beam 1 is not oscillated. 1/2 of the value obtained by subtracting 1/2 of the cutting groove width W
If the vibration amplitude of the laser beam 1 on the surface of the workpiece is smaller than the cutting width W / 2, the length of the component of the radius of gyration on the surface of the workpiece in the direction perpendicular to the cutting direction is smaller than the cutting width W / 2. The effect of improving the cut surface roughness R was obtained.

Even if the diameter and vibration amplitude of the laser beam 1 on the surface of the workpiece are the same, the cutting groove width W varies depending on the material of the workpiece 6, the plate thickness, and the machining shape. Also, when the range of the radius of gyration was kept and the radius of gyration on the surface of the workpiece was set, the effect of improving the roughness of the cut surface was obtained.

Particularly, when the rotation locus of the laser beam 1 on the surface of the workpiece is a perfect circle and the condition of the radius of rotation on the surface of the workpiece is satisfied, the axis of symmetry with the center of the beam irradiation portion as an axis Since it becomes a state, the direction of cutting disappears,
High-quality shape cutting is possible without changing the vibration direction according to the cutting progress direction.

Example 4. FIG. 12 is a schematic view showing a laser cutting method for corner portions according to an embodiment of the invention of claim 9. In FIG. 12, 1 is a laser beam, and 2 is a cutting groove formed in the workpiece 6. In the present Example 4, mild steel having a thickness of 4.5 mm, 12 mm and 25 mm was used as the work piece, and the laser beam 1 was 1.5 kW and 1.75 k, respectively.
With a continuous wave output of W and 3 kW, a ZnSe lens (not shown) having a focal length of 190.5 mm (not shown) is used to focus on 0.5 mm, 1.5 mm, and 1.5 mm above the surface of the workpiece. The surface of the object was irradiated. Cutting speed is 2.5m each
/ Min, 1.0 m / min, and 0.5 m / min. At this time, the nozzle original pressure is 1.0 kgf / cm ² and 0.6 kgf from a nozzle (not shown) coaxial with the laser beam 1 and having a hole diameter of 2 mm. /
Oxygen as an assist gas was blown to the cut portion at a pressure of cm ² and 0.5 kgf / cm ² . This laser beam 1
When the cutting advancing direction changes using two beam scanners (not shown) installed 500 mm above the surface of the workpiece, the direction of rotational movement of the laser beam 1 is set in the direction opposite to the changing direction. , Each frequency 300Hz,
The workpiece was moved in the cutting direction while rotating on the surface of the workpiece at 200 Hz and 200 Hz. At this time, the amplitude in the direction parallel to the cutting direction was 0.2 mm, and the amplitude in the direction orthogonal to the cutting direction was 0.2 mm. By such an operation, the amount of heat input to the lower portion of the workpiece 6 is increased, the retention of the melt in the corner is eliminated, and the melt flowing to the outer cut surface is increased, and the temperature of the edge is increased. Since the rise is suppressed, high-quality corner cutting that does not cause a reduction in cut surface roughness due to burn-through at the edge was realized.

Example 5. 13 and 14 are claims 10 and 1.
2 is a schematic diagram showing a laser cutting method according to an embodiment of the invention described in FIG. In FIGS. 13 and 14, 1 is a laser beam, 3 is a cutting front surface, 4 is an upper streak, 5 is a lower streak, and 6 is a workpiece. In Example 5, a mild steel having a thickness of 25 mm was used as a workpiece, the laser beam 1 was a continuous wave output of 3 kW, and a surface of the workpiece was processed with a ZnSe processing lens (not shown) having a focal length of 190.5 mm. The light was focused so as to focus 1.0 mm above.

Here, a ZnSe lens (not shown) for controlling the beam diameter having a focal length of 500 mm is arranged in the transmission path of the laser beam 1 50 mm before the processing lens, and the beam diameter controlling lens is set in the beam transmission direction. The beam diameter incident on the processing lens was changed by moving the beam back and forth at 200 Hz.

As a result, the beam focus position after passing through the processing lens oscillated at 200 Hz in the direction parallel to the beam incident direction (direction of arrow 50 in FIG. 14) with an amplitude of 1.0 mm. The cutting speed was 0.5 m / min, and the nozzle base pressure was 0.5 kgf / cm ² from a nozzle (not shown) coaxial with the laser beam 1 and having a hole diameter of 2 mm, and oxygen as an assist gas was supplied to the cutting portion. Sprayed. At this time, the beam diameter on the surface of the workpiece changed in the range of 0.3 mm to 0.9 mm, and the cutting groove width became 0.8 mm. By such an operation, the amount of heat input to the lower portion of the workpiece 6 is increased, so that the retention of the molten material is eliminated, and high quality cutting without lowering the roughness of the cut surface is realized.

FIG. 15 shows a plate thickness of 25 mm as the workpiece 6.
FIG. 6 is a diagram showing the relationship between the vibration amplitude A at the focal position of the laser beam 1 and the cut surface roughness R of the lower cut surface with respect to the mild steel material of FIG. The cut surface roughness R is improved within a certain range of the vibration amplitude of the focal position. In Example 5, the proper range of the vibration amplitude of the focus position was about 3.0 mm. This value was about 2.0 mm when converted into the maximum beam diameter on the surface of the workpiece.
The groove width at this time was about 1.4 mm, which was about 1 / 1.5 times the maximum beam diameter.

Even if the changing conditions of the laser beam 1 on the surface of the workpiece are the same, the cutting groove width W varies depending on the material of the workpiece, the plate thickness, and the processed shape. When the vibration center and the amplitude of the focus position were set so that the maximum beam diameter on the surface of the workpiece was smaller than 1.2 times the groove width, the effect of improving the cut surface roughness R was obtained.

In the fifth embodiment, since the laser beam 1 always changes while keeping the axial symmetry, the directionality of the cutting is lost. Therefore, the vibration direction is not changed according to the cutting proceeding direction, and the high quality shape is obtained. It became possible to disconnect.

Example 6. FIG. 16 is a schematic view showing a laser cutting device according to an embodiment of the invention described in claim 12 (device for executing the laser cutting method according to the invention described in claims 1 to 4). 16 in which the same parts as those in FIGS. 1 to 13 are designated by the same reference numerals and duplicate description is omitted, 7 is a processing lens, 8 is a laser oscillator for outputting a laser beam 1, and 9 is a laser oscillator.
Is a galvano scanner (hereinafter, abbreviated as a reflection mirror) as a moving unit that is driven in the direction of the arrow by a swing motor (not shown), 10 is a workpiece 6 on which the orthogonal axes X, Y,
A processing table movable in the Z direction, 19 is a folding mirror, and 20 is a nozzle. FIG. 17 is a block diagram showing the control circuit, and the same parts as those in FIG. In FIG. 17, reference numeral 11 denotes a mirror oscillating circuit that outputs a reflection mirror oscillating signal. The reflective mirror oscillating circuit 11 is, for example, the CPU 1 of the NC device 12.
When the rocking start command is received from 2a, the trigger pulse TP
And a second pulse generator 11b that outputs a reflection mirror swing signal M when a phase difference and amplitude value command is received from the trigger pulse TP and the CPU 12a. The output signal of the second pulse generator 11b is amplified by the amplifier 27, and the output signal of the amplifier 27 drives the swing motor (not shown) to swing the reflection mirror 9.

When the processing table moving signal is received from the CPU 12a, the processing table 10 is moved to the X, Y,
It is a servo control circuit that moves in the Z-axis direction, and includes, for example, a position control circuit 13a, a servo amplifier 13b, and a servo motor 13c. Reference numeral 14 is an excitation power supply which receives a command signal from the CPU 12a and drives the laser oscillator 8.

The operation of the sixth embodiment will be described below. In Example 6, a mild steel having a thickness of 25 mm was used as the workpiece 6, a laser beam 1 was a continuous wave output of 3 kW, and a focal length of 190.5 mm was a ZnSe processing lens. The focus was made 5 mm upward. The cutting speed is 0.5 m / min. As the assist gas, a nozzle (not shown) coaxial with the laser beam 1 and having a hole diameter of 2 mm is used to set the nozzle original pressure to 0.5 kgf / cm ^{2 and} oxygen is used as the assist gas. Sprayed on.

The workpiece 6 is fixed on a machining table 10 controlled by the NC device 12, and the machining table 10 is fixed.
Was moved in the directions of the orthogonal axes X, Y and Z in accordance with the processed shape. At this time, the processing table movement signal from the NC device 12 was transmitted to the reflection mirror swing circuit 11, and the reflection mirror 9 was swung in the direction of the arrow to oscillate the laser beam 1. In this case, the reflection mirror swing circuit 11 receives a signal from the NC device 12 and controls the swing of the reflection mirror 9 or the movement of the processing table 10 so that the table movement direction and the beam oscillation direction are always constant.

In the sixth embodiment, the laser beam 1 was oscillated by the oscillating reflection mirror 9 at 200 Hz in the vertical direction parallel or orthogonal to the cutting proceeding direction on the surface of the workpiece. By such an operation, the angle formed by the beam vibration direction and the cutting progress direction can be kept constant even if the shape is cut, and high-quality shape cutting without lowering the cut surface roughness is realized. .

Example 7. 18 is a perspective view showing a laser cutting device according to another embodiment of the invention as set forth in claim 12, FIG.
9 is a front view thereof. In the sixth embodiment, the reflection mirror 9 is swung to vibrate the position of the laser beam 1 with respect to the workpiece 6, but in the seventh embodiment, the reflection mirror 9 is fixed and the workpiece 6 is vibrated. 18 and 19, 22 is a working table placed on the working table 10 via rollers 23, and 24 is a fixing jig for fixing the workpiece 6 on the working table 22. Reference numerals 25a and 25b are vibrators for vibrating the work table 22 in the orthogonal axes X and Y directions. Reference numeral 26 is a vibrator for receiving drive signals from the CPU 12a.
5b is a vibrator driving circuit for driving either one or both of them at the same time. Since Example 7 has the above-mentioned configuration,
The laser beam 1 from the laser oscillator 8 is applied to the workpiece 6 through the processing lens 7 to perform the cutting process. When one of the vibrators 25a and 25b is driven during this cutting process, the processing table 22 vibrates in the orthogonal axis X or Y direction,
The same effect as that of the sixth embodiment can be obtained.

Example 8. FIG. 20 shows a laser cutting device according to yet another embodiment of the invention as set forth in claim 12 (claims 7 to
9 is a schematic view showing an apparatus for executing the laser cutting method according to the invention described in 9, and two reflecting mirrors 9 having swing axes (not shown) orthogonal to each other are used as the reflecting mirrors 9 in the sixth embodiment.
a and 9b are used. FIG. 21 is a block diagram showing a reflection mirror swing circuit 11 that swings the reflection mirrors 9a and 9b. The first pulse generator outputs a trigger pulse TP when a swing start command is received from the CPU 12a of the NC device 12. 11a and two second pulse generators 11b-1 and 11b-2 that output the reflection mirror swing signal M when the trigger pulse TP and the phase difference and amplitude value command are received from the CPU 12a. The output signals of the pulse generators 11b-1 and 11b-2 of the reflection mirror 9 are transmitted through amplifiers 27a and 27b.
Reflecting mirror swing motors 28a, 28 for swinging a, 9b
b.

In the eighth embodiment, the reflection mirror swing motor 2
In the sixth embodiment, the two reflecting mirrors 9a and 9b are independently swung by 8a and 28b.
The same effect as the above can be obtained, and the laser beam 1
When the center axis of the spot is rotationally moved on the radius of gyration on the surface of the workpiece, and when the cutting advancing direction changes, the rotational movement direction of the laser beam 1 is set in the direction opposite to the changing direction. It is possible to achieve high quality corner cutting.

Example 9. FIG. 22 is a schematic diagram showing a laser cutting device according to an embodiment of the invention described in claims 13 and 14, and the same parts as those of the embodiment 6 shown in FIG. . In FIG. 22, 29
Reference numerals a and 29b are rotary disk mirrors serving as switching means, a part of which is axisymmetrically cut away, 30a and 30b are photoelectric sensors for detecting the positions of the rotary disk mirrors 29a and 29b, and 31.
a and 31b are optical paths (laser beam transmission path) 32b different from the optical path (laser beam transmission path) 32a of the laser beam 1.
Bending mirrors 33a, 33b are pulse motors for rotating the rotary disk mirrors 29a, 29b, and 34 is a beam diameter control means for inputting detection signals of the photoelectric sensors 30a, 30b and supplying drive signals to the pulse motors 33a, 33b. It is a rotating disk mirror control circuit.

FIG. 23 shows the rotating disk mirror control circuit 34.
3 is a block diagram showing an example of the CPU of the NC device 12; FIG.
12a receives a rotation speed command from the pulse motor 33a,
Drivers 34a-1 and 34 for supplying drive signals to 33b
a-2 and the detection signal S from the photoelectric sensors 30a and 30b
1, S2 are input, a sum of both signals is calculated, and a matching signal is supplied to the CPU 12a. In the ninth embodiment, the workpiece 6 has a thickness of 25
mm of mild steel was used, the laser beam 1 was a continuous wave output of 3 kW, and a ZnSe processing lens 7 having a focal length of 190.5 mm was used to focus and irradiate the workpiece 6. Cutting speed is 0.5m / min, hole diameter 2mm coaxial with laser beam 1
Nozzle source pressure of 0.5 kgf /
cm ² and oxygen as an assist gas is used as the cutting portion 2a.
Sprayed on.

At this time, the light reflecting portions 29a-1 and 29b-1 and the transmitting portions 29a-2 of the rotating disk mirrors 29a and 29b,
The position of 29b-2 is monitored by the photoelectric sensors 30a and 30b, and the rotating disk mirror is so arranged that the laser transmission path is switched to the optical path 32a and the optical path 32b at a desired frequency sequentially as shown in FIGS. 24 (a) and 24 (b). The rotational disc mirror control circuit 34 controls the rotational speed and the phase shift of 29a and 29b. In addition,
In the present embodiment, the switching between the optical path 32a and the optical path 32b is switched to two.
It was performed at 00 Hz.

By such an operation, the beam diameter incident on the processing lens 7 was vibrated at 200 Hz, and the focal position was vibrated in the beam axis direction within the range of 0 mm to 2.0 mm from the surface of the workpiece. As a result, the amount of heat input to the lower portion of the workpiece 6 is increased, the retention of the melt is eliminated, and high quality cutting without lowering the roughness of the cut surface is realized.

Example 10. FIG. 25 is a schematic view showing a laser cutting method according to an embodiment of the invention of claim 15. In FIG. 25, reference numeral 1 is a laser beam, and the processing lens 7
The workpiece 6 is irradiated via the. In the tenth embodiment, the workpiece 6 has a thickness of 4.5 mm, 12 mm, and 25 mm.
mm mild steel, laser beam 1 is 1.5 kW each,
1.75kW, 3kW continuous wave output, focal length 19
The surface of the work piece was irradiated with the 0.5 mm processing lens 7 made of ZnSe so as to focus on the surface of the work piece by 0.5 mm, 1.5 mm and 1.5 mm, respectively. The cutting speeds are 2.5 m / min, 1.0 m / min, and 0.5 m / min, respectively, and at this time, the nozzle base pressure is 1.0 kgf / cm ² from the nozzle 20 having a hole diameter of 2 mm coaxial with the laser beam. 0.6 kgf
/ Cm ² , 0.5 kgf / cm ² , and oxygen 21 was blown to the cutting portion 2a as an assist gas. At this time, liquid nitrogen was used to cool to −50 ° C. by the gas cooling device 22. By such an operation, the ability to remove the melt of oxygen as an assist gas was improved, retention was eliminated, and high quality cutting without reduction in cut surface roughness was realized.

Example 11. FIG. 26 is a schematic diagram showing a laser cutting method according to an embodiment of the invention of claim 16. In FIG. 26, 1 is a laser beam, and the processing lens 7
The workpiece 6 is irradiated via the. In Example 11, the thickness of the workpiece 6 was 4.5 mm, 12 mm, 25 mm.
mm mild steel, laser beam 1 is 1.5 kW each,
1.75kW, 3kW continuous wave output, focal length 19
The surface of the work piece was irradiated with the 0.5 mm processing lens 7 made of ZnSe so as to focus on the surface of the work piece by 0.5 mm, 1.5 mm and 1.5 mm, respectively. The cutting speeds are 2.5 m / min, 1.0 m / min, and 0.5 m / min, respectively, and at this time, the nozzle base pressure is 1.0 kgf / cm ² from the nozzle 20 having a hole diameter of 2 mm and coaxial with the laser beam 1. 0.6 kgf /
Oxygen as an assist gas was blown to the cutting portion 2a at a pressure of cm ² and 0.5 kgf / cm ² . Further, by a straight type, crater number # 2 (cutting oxygen outlet diameter 1.3 mm) nozzle 20 for cutting LP gas, a gas cooling device 22 using liquid nitrogen is aimed toward the lower part of the cutting surface from the rear of the cutting direction. Oxygen cooled to −50 ° C. was blown at a nozzle original pressure of 3 kgf / cm ² . By such an operation, retention in the lower part of the workpiece 6 was eliminated, and high quality cutting without reduction in cut surface roughness was realized.

[0069]

As described above, according to the first aspect of the invention, since the position or diameter of the laser beam with respect to the workpiece is vibrated, the laser energy applied to the deep portion of the cutting groove is increased. In this way, the insufficient heat input in the deep part of the cutting groove is eliminated, the temperature of the melt rises, and the viscosity becomes low. As a result, in the lower part of the cut surface of the work piece,
There is an effect that retention of the melt is eliminated and high quality cutting can be realized without lowering the cut surface roughness.

According to the second aspect of the invention, since the vibration frequency of the laser beam is set to be higher than the generation frequency of the scratches generated on the cut surface, the vibration of the laser beam makes the cutting phenomenon unstable. There is an effect that can prevent this.

According to the invention described in claim 3, the laser beam is vibrated in parallel with the cutting direction, and according to the invention described in claim 4, the vibration amplitude is smaller than the width of the cutting groove. The vicinity of the central axis of the beam having a high power density is directly irradiated to the deep portion of the cutting groove, the insufficient heat input in the deep portion of the cutting groove is resolved, the temperature of the melt rises and the viscosity becomes low. As a result, in the lower part of the cut surface of the workpiece, the stay of the melt is eliminated, and there is an effect that high quality cutting can be realized without lowering the roughness of the cut surface.

According to the invention of claim 5, the laser beam is vibrated in parallel with the cutting proceeding direction, and according to the invention of claim 6, the vibration amplitude is made smaller than the width of the cutting groove. The laser energy incident on the cutting groove and the laser power density P increase, the insufficient heat input in the deep portion of the cutting groove is resolved, the temperature of the melt rises, and the viscosity decreases. As a result, in the lower part of the cut surface of the workpiece, the stay of the melt is eliminated, and there is an effect that high quality cutting can be realized without lowering the roughness of the cut surface.

According to the invention described in claim 7, the beam having a small focused spot is rotated, and according to the invention described in claim 8, the component parallel to the cutting advancing direction of the rotating diameter is changed to the length of the cutting groove. The width of the beam is smaller than the value calculated from the width and the width, and the component orthogonal to the cutting direction is smaller than the width of the cutting groove. Due to the effect of vibrating orthogonally, insufficient heat input in the deep portion of the cutting groove is eliminated, the temperature of the melt rises, and the viscosity becomes low. As a result, in the lower part of the cut surface of the workpiece, the stay of the melt is eliminated, and there is an effect that high quality cutting can be realized without lowering the roughness of the cut surface.

According to the invention described in claim 9, since the rotational movement direction of the laser beam is set to the direction opposite to the change of the cutting proceeding direction, the melt can be prevented from flowing to the corner edge portion, The temperature rise at the corner edge can be suppressed. As a result, there is an effect that the burn-through at the corner edge portion is eliminated, and high-quality corner cutting can be realized without lowering the cut surface roughness.

According to the tenth aspect of the invention, the focal position is vibrated in the direction of the incident axis of the laser beam. According to the eleventh aspect of the invention, the maximum value of the laser beam diameter is approximately 1. Since it is configured to be smaller than 5 times, the cutting groove width is specified near the maximum beam diameter, and when the beam diameter is less than that, all the laser energy enters the cutting groove, and the heat input in the deep portion of the cutting groove is insufficient. Is eliminated, the temperature of the melt rises and the viscosity decreases. As a result, in the lower part of the cut surface of the workpiece, the stay of the melt is eliminated, and there is an effect that high quality cutting can be realized without lowering the roughness of the cut surface.

According to the twelfth aspect of the invention, even if the cutting advancing direction changes, the angle between the cutting advancing direction and the vibration direction of the laser beam on the surface of the workpiece is always kept constant. Even in shape cutting, insufficient heat input in the deep portion of the cutting groove is resolved, and there is an effect that high-quality shape cutting can be realized without lowering the cut surface roughness.

According to the thirteenth aspect of the invention, the beam diameter on the surface of the workpiece is changed, and according to the fourteenth aspect of the invention, the beam diameter is changed by switching the laser beam transmission path by the switching means. Since the cutting groove width is specified near the maximum beam diameter, when the beam diameter is less than that, all the laser energy enters the cutting groove, and the insufficient heat input in the deep cutting groove is eliminated, and the melt The temperature rises and the viscosity decreases. As a result, in the lower part of the cut surface of the work piece,
There is an effect that the retention of the melt is eliminated and high quality cutting can be realized without lowering the roughness of the cut surface.

According to the fifteenth aspect of the present invention, since the assist gas is cooled, the straightness is increased,
The action of removing the melt is improved. As a result, in the lower part of the cut surface of the workpiece, the stay of the melt is eliminated, and there is an effect that high quality cutting can be realized without lowering the roughness of the cut surface.

According to the sixteenth aspect of the present invention, the assist gas is blown to the cutting portion from behind the cutting portion irradiated with the laser beam in the cutting proceeding direction.
Since the laser beam does not pass through the assist gas blowing nozzle, the degree of freedom in nozzle design is expanded and the assist gas flow rate can be improved. As a result, the retention of the melt is eliminated in the lower part of the cut surface of the workpiece,
There is an effect that it is possible to realize high-quality cutting that does not cause reduction in cut surface roughness.

[Brief description of drawings]

FIG. 1 is a schematic view showing a laser cutting method according to an embodiment of the invention described in claims 1 to 4.

FIG. 2 is a schematic diagram illustrating the operation of the laser cutting method of FIG.

FIG. 3 is a characteristic diagram illustrating the operation of the laser cutting method of FIG.

4 is a front view of a cut surface cut by the laser cutting method of FIG. 1. FIG.

FIG. 5 is a characteristic diagram illustrating an operation of the laser cutting method of FIG.

6 is a front view of a cut surface cut by the laser cutting method of FIG. 1. FIG.

7 is a processing condition diagram in the laser cutting method of FIG.

FIG. 8 is a schematic view showing a laser cutting method according to an embodiment of the invention described in claims 5 and 6.

FIG. 9 is a schematic diagram illustrating the operation of the laser cutting method of FIG.

FIG. 10 is a schematic diagram for explaining the operation of the laser cutting method of FIG.

FIG. 11 is a schematic diagram showing a laser cutting method according to an embodiment of the invention described in claims 7 and 8.

FIG. 12 is a schematic view showing a laser cutting method according to an embodiment of the present invention.

FIG. 13 is a schematic view showing a laser cutting method according to an embodiment of the invention described in claims 10 and 11.

14 is a front view of a cut surface cut by the laser cutting method of FIG.

FIG. 15 is a characteristic diagram illustrating the operation of the laser cutting method of FIG.

FIG. 16 is a schematic view showing a laser cutting device according to an embodiment of the present invention.

FIG. 17 is a block diagram of a control circuit that executes the laser cutting method of FIG.

FIG. 18 is a perspective view showing a laser cutting device according to another embodiment of the present invention.

19 is a front view of the laser cutting device of FIG. 18. FIG.

FIG. 20 is a schematic view showing a laser cutting device according to still another embodiment of the invention as set forth in claim 12.

21 is a block diagram of a reflection mirror swing circuit in the laser cutting apparatus of FIG.

FIG. 22 is a schematic view showing a laser cutting device according to an embodiment of the invention described in claims 13 and 14.

23 is a block diagram of a rotary disk mirror control circuit in the laser cutting device of FIG. 22.

FIG. 24 is an explanatory diagram of a transmission line in the laser cutting device of FIG. 22.

FIG. 25 is a schematic view showing a laser cutting method according to an embodiment of the invention as set forth in claim 15;

FIG. 26 is a schematic view showing a laser cutting method according to an embodiment of the invention as set forth in claim 16;

FIG. 27 is a schematic view showing a conventional laser cutting method.

28 is a front view of a cut surface cut by the laser cutting method of FIG. 27. FIG.

FIG. 29 is a schematic diagram for explaining the operation of the laser cutting method of FIG. 27.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 laser beam 2 cutting groove 2a cutting part 3 cutting front surface 4 upper streak 5 lower streak 6 workpiece 7 processed lens 8 laser oscillator 9, 9a, 9b reflection mirror (moving means) 11 reflection mirror swing circuit 21 assist gas 22 gas cooling device 29a, 29b rotating disk mirror (switching means) 32a optical path (laser beam transmission path) 32b optical path (laser beam transmission path) 34 rotating disk mirror control circuit (beam diameter control means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B23K 26/14 Z G02B 26/10 C (72) Inventor Masayuki Kaneko 8-1-1 Tsukaguchihonmachi, Amagasaki No. 1 Mitsubishi Electric Co., Ltd. Production Technology Laboratory (72) Inventor Yu Kanaoka 5-14 Yanda Minami 5-chome, Higashi-ku, Nagoya City Mitsubishi Electric Co., Ltd. Nagoya Works

Claims (16)

[Claims] 1. A laser cutting method for irradiating a workpiece with a laser beam and cutting the workpiece with the energy of the laser beam, wherein the workpiece and the laser beam are relatively moved during cutting. The laser cutting method is characterized by vibrating the position of the laser beam or the diameter of the laser beam with respect to the workpiece. 2. The oscillation frequency of the laser beam is set to be higher than the generation frequency of the streak calculated from the pitch and the cutting speed of the streak generated on the cut surface of the workpiece when the laser beam is not vibrated. The laser cutting method according to claim 1, wherein: 3. The laser cutting method according to claim 1, wherein the vibration direction of the laser beam is parallel to the cutting proceeding direction. 4. The difference between the cutting groove lengths of the front surface and the back surface of the workpiece when the laser beam is not vibrated and the vibration amplitude parallel to the cutting progress direction of the laser beam and the cutting on the surface of the workpiece. The laser cutting method according to claim 3, wherein the value is set smaller than a value calculated from the groove width. 5. The laser cutting method according to claim 1, wherein a vibration direction of the laser beam is orthogonal to a cutting proceeding direction. 6. A vibration amplitude orthogonal to the cutting direction of the laser beam is approximately 1 / the cutting groove width on the surface of the workpiece.
The laser cutting method according to claim 5, wherein the laser cutting method is set to be smaller than 2. 7. The laser cutting method according to claim 1, wherein the central axis of the spot of the laser beam is rotationally moved on the surface of the workpiece on a radius of gyration. 8. A component parallel to a cutting proceeding direction of a rotation diameter in which a central axis of the spot of the laser beam is rotationally moved is a cutting groove length of the front surface and the back surface of the workpiece when the laser beam is not rotated. The difference should be smaller than the value calculated from the cutting groove width on the surface of the workpiece, and the component orthogonal to the cutting proceeding direction should be set smaller than about 1/2 of the cutting groove width on the surface of the workpiece. The laser cutting method according to claim 7, wherein: 9. The laser cutting method according to claim 7, wherein when the cutting proceeding direction changes during cutting, the rotational movement direction of the laser beam is set in a direction opposite to the changing direction. . 10. The laser cutting method according to claim 1, wherein the oscillation direction of the laser beam is parallel to the incident axis direction of the laser beam. 11. When the laser beam is oscillated parallel to the incident axis direction of the laser beam, the maximum value of the laser beam diameter on the surface of the workpiece is approximately 1 of the width of the cutting groove on the surface of the workpiece. 11. The laser cutting method according to claim 10, wherein the laser cutting method is set to be smaller than 0.5 times. 12. A laser cutting device for irradiating a laser beam onto a workpiece and cutting the workpiece with the energy of the laser beam, the laser beam of the laser beam with respect to the workpiece even if the cutting direction changes. A laser cutting device comprising moving means for relatively moving the workpiece and the laser beam so as to keep the angle of the vibration direction constant. 13. A laser cutting device for irradiating a laser beam onto a workpiece and cutting the workpiece with the energy of the laser beam, a beam diameter control means for changing the diameter of the laser beam on the surface of the workpiece. Laser cutting device equipped with. 14. The apparatus according to claim 13, further comprising a plurality of laser beam transmission paths having different transmission distances to the surface of the workpiece, and switching means for switching the laser beam transmission paths during processing. Laser cutting device. 15. A laser cutting method for irradiating a workpiece with a laser beam, melting the workpiece with the energy of the laser beam, removing the melt with an assist gas, and cutting the workpiece. A laser cutting method characterized in that an assist gas is cooled and sprayed onto a cutting portion. 16. The laser cutting method according to claim 15, wherein the cooled assist gas is sprayed onto the cutting portion from behind the cutting portion irradiated with the laser beam in the cutting proceeding direction.