JPH10328870A - Laser cutting method and laser machining head used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always obtain a superior cross section of a product to be cut in a laser cutting method in which an eccentric laser beam is rotated. SOLUTION: This laser machining head is such that an optical system 7 for eccentricity is provided in a position downward from a condensing lens 3 for converging a laser beam, a system which makes a laser beam eccentric from the optical axis of the condensing lens and which is freely rotatably driven, and that an assist gas nozzle 11 is provided which passes a laser beam from the optical system 7 for eccentricity and which injects an assist gas coaxially; the machining head is also provided with a servo motor 9 for rotatably driving the optical system 7, controllably changing the rotary direction of the servo motor 9 in accordance with a positional relation of a product to be cut against the cutting advancing direction, and is further provided with an NC device 33 that arithmetically controls the number of revolution of the servo motor 9 on the basis of a speed for cutting the product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a laser cutting method and a laser processing head used in the laser cutting method.

[0002]

2. Description of the Related Art The applicant of the present invention has applied for a laser cutting method related to the present invention and an invention of a laser processing head used in the cutting method (Japanese Patent Application No. Hei 8-305031).

[0003] The laser cutting method of the present invention is as follows.
This is a method capable of cutting a thick plate (about 19 to 25 mm) of a mild steel sheet with practical accuracy. For example, when cutting a work W of a mild steel sheet having a thickness t as shown in FIGS. A laser beam condensed and decentered by δ from the axis of a head (not shown) is rotated at a high speed with a radius δ around the axis of the processing head, and assist gas is injected to a cutting portion of the workpiece W. , The workpiece W is relatively moved along the cutting line 101 with respect to the laser processing head.

In the laser cutting method, a minute beam spot 103 of the condensed laser moves in the direction of the cutting line 101 while rotating at a radius δ to form a part of a cutting front (a region in the cutting process) 105. Cut or remove at high speed little by little. Since the depth ΔH of the cutting front 105 portion is very small, an assist gas such as oxygen is sufficiently supplied to the bottom of the cutting front 105 to activate the oxidation reaction, generate reaction heat, and melt by the assist gas. The metal is immediately discharged, and the cutting of the work W proceeds with the cutting width A (2δ).

[0005] In the cutting process, the volume of the cutting front portion 105 removed when the laser beam makes one rotation is a very small volume consisting of the area (S) of the crescent-shaped portion and the depth ΔH. Further, due to the repeated rotation of the laser beam, the cutting front portion 105 is consequently formed in a preheated state and the temperature is promoted, so that a thick steel plate (19 to 25 mm) with a medium output laser of about 2 kW is used.
This enables cutting with practical accuracy.

[0006]

In the laser cutting method of the present invention, which is filed by the present applicant, the laser beam is rotated during the cutting movement, so that the relative velocities of the laser beam on the left and right sides of the cutting groove are different from the work. I do. From this, for example, when the laser beam is rotating counterclockwise when viewed from the upper surface of the work W, the cutting quality of the cutting groove on the left bank becomes better than that of the right bank in the cutting progress direction, and the lower surface of the right bank is “ "Egret", "Dross adhesion"
Etc. occur and cutting quality deteriorates. Therefore, this cutting method requires a cutting method that makes use of the cut one side.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a laser cutting method for rotating an eccentric laser beam, in which a product to be cut can always be cut with a good cut surface. And to provide a laser processing head used for the same cutting method.

[0008]

According to a first aspect of the present invention, there is provided a laser cutting method for rotating an eccentric laser beam.
The gist of the invention is to change the direction of rotation of the eccentric laser beam according to the positional relationship between the cutting direction and the product to be cut.

According to a second aspect of the present invention, there is provided a laser cutting method according to the first aspect, wherein the rotational direction of the eccentric laser beam is set such that the rotational direction of the eccentric laser beam is in a positional relationship between the cutting direction and the product to be cut. Counterclockwise when the product to be cut is located on the left
When the product to be cut is located on the right side with respect to the cutting progress direction, the gist is to change clockwise.

Therefore, according to the laser cutting method of the first or second aspect, even if a cutting method for rotating an eccentric laser beam having different cutting surface qualities on the left and right sides of the cutting groove is used, the cutting surface has a "surface". It is possible to obtain a good product with little scramble and dross adhesion.

The laser processing head according to claim 3 is
At a position below the condensing lens for condensing the laser beam, an eccentric optical system that is rotatably driven to decenter the laser beam from the optical axis of the condensing lens is provided, and the laser beam from the eccentric optical system is provided. A laser processing head provided with an assist gas nozzle for injecting the assist gas coaxially with the passage, and a servo motor for rotating and driving the eccentric optical system is provided. The present invention is characterized in that an NC device is provided which performs change control according to the positional relationship with a product and calculates and controls the rotation speed of the servo motor from the product cutting speed.

The laser processing head according to claim 4 is
4. The laser processing head according to claim 3, wherein the rotational direction of the servomotor is such that, in a positional relationship between the cutting direction and the product to be cut, the product to be cut is located on the left side with respect to the cutting direction. Is counterclockwise,
When the product to be cut is located on the right side with respect to the cutting progress direction, the rotation is controlled clockwise, and the calculation of the rotation speed of the servo motor is calculated from the relational expression between the product cutting speed and the rotation speed of the laser beam. The gist is that.

Therefore, according to the laser processing head according to the third or fourth aspect, the positional relationship between the cutting progress direction and the product to be cut, and the relational expression between the product cutting speed and the number of rotations of the laser beam are obtained. In addition, it is possible to automatically set the rotation direction and the number of rotations of the eccentric laser beam, which cause less surface scuffing and dross adhesion on the cut surface of the product.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a laser processing head according to the present invention. Referring to FIG. 1, a laser processing head 1 includes a condenser lens 3 for condensing a laser beam LB, and an eccentric optical system for decentering the laser beam LB from the condenser lens from the optical axis of the condenser lens. An optical flat 7, a servo motor 9 that rotationally drives the optical flat 7,
It is composed of an assist gas nozzle 11 and the like.

The condenser lens 3 is exchangeably screwed to the inner diameter of a hollow cylindrical optical system support member 13 via a lens holder 15. An optical flat 7 is provided on the optical system support member 13 as an eccentric optical system which is located below the condenser lens 3 and decenters the laser beam LB from the optical axis of the condenser lens 3.

The optical flat 7 is provided at the upper end of a hollow rotary cylinder 19 at an appropriate angle to the optical axis of the condenser lens 3. The rotating cylinder 19 is rotatably provided via upper and lower bearings 17 provided separately from the inner diameter of the optical system support member 13. 21 is attached.

A motor bracket 23 is provided on the optical system support member 13 so as to extend laterally, and the servo motor 9 is mounted on the motor bracket 23. A belt 27 is looped between a driving pulley 25 provided on the output shaft of the servomotor 9 and the driven pulley 21. It is desirable to use toothed pulleys for the driven pulley 21 and the drive pulley 25 and the like.

At the lower end of the optical system support member 13, there is provided an assist gas nozzle 11 for passing a laser beam from the optical flat 7 and for injecting an assist gas coaxially. An optically transparent window 29 for preventing an assist gas such as oxygen, nitrogen or air and dust in the air from entering the optical flat 7 is mounted on the upper part of the assist gas nozzle 11. In the nozzle 11, an assist gas supply port 31 to be supplied at the time of cutting is provided at a side position below the window 29.

In the above configuration, the laser beam LB incident on the optical flat 7 from the condenser lens 3 is
The optical flat 7 provided at the upper end of the rotary cylinder 19 at an appropriate angle to the optical axis 5 of the condenser lens 3 provides
It is possible to converge and irradiate a position eccentric by δ from the optical axis 5 on the surface of the work W. Therefore, when the servo motor 9 is rotationally driven, the rotary cylinder 19 supporting the optical flat 7 is rotated, so that the laser beam LB condensed on the surface of the work W is circled around the optical axis 5 with a radius δ. You will exercise.

The diameter of the assist gas injection port of the assist gas nozzle 11 is set to 2 * δ or more so as not to interfere with the circular movement of the laser beam. Also, an optical wedge can be used instead of the optical flat 7 as the decentering optical system. Further, the nozzle tip of the assist gas nozzle 11 can be a replaceable nozzle tip.

As shown in FIG.
Is the rotation speed (rotation speed) under the control of the NC device 33.
The rotation direction is controlled by a CPU (not shown). More specifically, the NC device 33 is provided with a processing condition storage unit 35, a cutting shape program unit 37, and a rotation speed calculation unit 39. The rotation speed calculation unit 39 stores the processing speed data from the processing condition storage unit 35. Is calculated based on the rotation speed, and an appropriate control command (voltage value) is output from the motor drive unit 41 to the servomotor 9 based on the rotation speed. Further, the rotation direction of the servo motor 9 is controlled in the motor drive unit 41 based on the rotation direction command from the cutting shape program unit 37. The servo motor 9 may be an AC servo motor, a DC servo motor, a stepping motor, or the like.

In the processing condition storage unit 35, a relational expression between a plate thickness t of various materials described later and a maximum cutting speed Fmax and a relational expression between the cutting speed F and the laser beam rotation speed N are registered. Further, the cutting shape program created by the automatic programming device 43 is input to the cutting shape program unit 37 via the external storage device 45, and the cutting shape program is stored. The cutting shape program unit 37 includes commands such as the rotation direction of the eccentrically rotating laser beam, the designation of the material and the thickness, the processing start position (piercing position), and the cutting progress direction.

The NC unit 33 controls the output of a laser oscillator 49 via a laser control unit 47, and uses a work moving device or a laser processing head of a laser processing machine (not shown) as an axis control unit 51 and a servo amplifier. 5
Positioning control can be performed via the drive motor 3 and the drive motor 55. The contents of the processing condition storage unit 35 can be appropriately edited by a processing condition editing unit 57 provided with a display device.

FIG. 2 shows the automatic programming device 4 described above.
3 illustrates the work process when cutting the product P inside the work W. First, the material of the work W,
Set the thickness and laser processing machine to be used. next,
Automatic programming device 4 for cutting shape (hole and outer circumference)
3 on the display.

In the process of creating the cut shape (hole and outer periphery), a piercing start position as a cutting start point is designated, and the product P to be cut is inside a closed loop curve formed by a tool path (cutting line). Set whether to be outside. Further, for both the hole and the outer circumference, whether the cutting direction is clockwise or counterclockwise is set, and “tool diameter correction right” or “tool diameter” is determined depending on whether the outer circumference or the inner circumference of the product P is cut. Either "correction left" (NC code for shifting the cutting position rightward or leftward in the traveling direction; G42, G41). That is, in the example of the product P in FIG. 2, the cutting direction is clockwise, the product P is inside the closed loop curve, “tool diameter correction left” is used in the outer peripheral cutting path of the product P, and “ Tool diameter correction right "is specified.

In the process of forming the cut shape (hole and outer periphery), the rotational direction of the eccentric laser beam 6
In 1, the automatic programming device 43 automatically determines a program command from the four types of patterns shown in FIG.

The four types of patterns have a cutting direction 5
9 and the product P are classified into the following four types of patterns. (A) the cutting progress direction 59 is counterclockwise, and the product P is inside the closed loop curve C formed by the cutting path;
(B) The cutting progress direction is counterclockwise, and the product P is outside the closed loop curve C formed by the cutting path. (C) The cutting progress direction is clockwise, and the product P is inside the closed loop curve C formed by the cutting path. d) The cutting progress direction is clockwise, and the product P is outside the closed loop curve C formed by the cutting path.

In the four types of patterns, in the case of (a) and (d), the setting of the counterclockwise rotation of the beam is selected, and in the case of (b) and (c), the rotation direction of the beam is selected. Reference numeral 61 indicates that the clockwise setting is selected. That is, in the positional relationship between the cutting progress direction 59 and the product P to be cut, the product P to be cut is
The counterclockwise direction is selected when the product P to be cut is located on the left side with respect to the nine directions, and the clockwise rotation is selected when the product P to be cut is located on the right side with respect to the cutting progress direction 59. Therefore, the cutting quality of the product P to be cut is always good.

Through the above-described cutting shape creation process,
A cutting program is automatically created by the automatic programming device 43 and output to the external storage device 45,
Then, the data is input from the external storage device 45 to the NC device 33.

Referring to FIGS. 4 and 5, FIG.
FIG. 13 is a plot of the results obtained by experiments on the relationship between the plate thickness and the maximum cutting speed in S304. The horizontal axis represents the cutting plate thickness t (mm), and the vertical axis represents the maximum cutting speed Fmax (mm / m).
in). The relational expression shown in FIG. 4 indicates that this experimental data is obtained by using a natural logarithmic curve, Fmax = −247.71L.
n (t) +971.06. Therefore, the cutting speed F (mm / min) can be set during the program with the maximum cutting speed Fmax (mm / min) at the plate thickness t in the range shown in the graph as the upper limit.

FIG. 5 is a plot of the relationship between the cutting speed and the number of revolutions of the laser beam in SUS304, obtained by experiments, as in FIG. 4. The horizontal axis represents the cutting speed F (mm / min), and the vertical axis represents the result. Is the beam rotation speed N (rp
m). The relational expression shown in FIG. 5 indicates that the experimental data is obtained by using a natural logarithmic curve and N = −615.51 Ln.
(F) Approximated by +2031.4. Therefore, if the cutting speed F is designated by the program, the rotation speed N of the laser beam can be obtained by calculation from the above-mentioned relational expression.

Although the graphs and the relational expressions in FIGS. 4 and 5 are examples of SUS304, the relational expressions are similarly obtained for other materials.

[0033]

According to the first or second aspect of the present invention, even if a cutting method for rotating an eccentric laser beam having different cut surface qualities on the left and right sides of a cut groove is used, the cut surface can be formed as a "surface". It is possible to obtain a good product with little scramble and dross adhesion.

According to the third or fourth aspect of the present invention, the positional relationship between the cutting direction and the product to be cut is determined.
From the relational expression between the product cutting speed and the number of rotations of the laser beam, it is possible to automatically set the rotation direction and number of rotations of the laser beam, which causes less "slipping" and dross adhesion on the cut surface of the product. There is no possibility that the product side is defective due to the wrong rotation direction of the beam. Also, material,
Since the number of rotations of the laser beam relating to the plate thickness and the cutting speed is automatically controlled, adjustment errors and mistakes by the operator can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a laser processing head according to the present invention.

FIG. 2 is an explanatory diagram of a work process in the automatic programming device.

FIG. 3 is an explanatory diagram of a laser beam rotating direction in four patterns of a cutting progress direction and a relative positional relationship between products.

FIG. 4 is a graph and a relational expression of a relationship between a plate thickness and a maximum cutting speed in SUS304.

FIG. 5 is a graph and a relational expression of a relationship between a cutting speed and a rotation speed of a laser beam in SUS304.

FIG. 6 is an explanatory diagram of a method of cutting a thick plate by rotating a laser beam condensed and decentered by δ from an axis of a laser processing head by a radius δ.

FIG. 7 is a sectional view of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser processing head 3 Condensing lens 5 Optical axis of condensing lens 7 Optical flat 9 Servo motor 11 Assist gas nozzle 19 Rotating cylinder 33 NC unit 35 Processing condition storage unit 37 Cutting shape program unit 39 Rotation speed calculation unit 41 Motor drive unit 43 Automatic programming device 45 External storage device 57 Processing condition editing unit 59 Cutting progress direction 61 Beam rotation direction C Closed loop curve P Product W Work

Claims (4)

[Claims] 1. A laser cutting method for rotating an eccentric laser beam, wherein the direction of rotation of the eccentric laser beam is changed according to a positional relationship between a cutting direction and a product to be cut. 2. The rotation direction of the eccentric laser beam,
In the positional relationship between the cutting direction and the product to be cut, when the product to be cut is located on the left side with respect to the cutting direction, the product to be cut is on the right side with respect to the cutting direction. 2. The laser cutting method according to claim 1, wherein the position is changed in a clockwise direction. 3. An eccentric optical system rotatably driven to decenter the laser beam from the optical axis of the condenser lens is provided below the condenser lens that condenses the laser beam. A laser processing head provided with an assist gas nozzle for coaxially injecting an assist gas while allowing a laser beam from the laser beam to pass therethrough, and a servo motor for rotationally driving the eccentric optical system is provided, and the rotational direction of the servo motor is cut off. NC for controlling the change according to the positional relationship between the traveling direction and the product to be cut and calculating and controlling the rotation speed of the servo motor from the product cutting speed.
A laser processing head provided with a device. 4. A method according to claim 1, wherein the direction of rotation of the servomotor is determined by a positional relationship between the cutting progress direction and a product to be cut.
When the product to be cut is located on the left side with respect to the cutting progress direction, the rotation is controlled in a counterclockwise direction. When the product to be cut is located on the right side with respect to the cutting direction, the rotation is controlled in a clockwise direction. The laser processing head according to claim 3, wherein the calculation of the number of rotations is performed from a relational expression between the product cutting speed and the number of rotations of the laser beam.