JP2002137079A - Laser beam machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make use of a laser beam oscillator 2 which sets a laser beam M2 value in a range from 7 or more to 12 or less when a work 7 made of a steel plate exceeding 20 mm in thickness is cut by a laser beam machine 1. SOLUTION: When the work 7 made of a mild steel plate exceeding 20 mm in thickness is cut, it can excellently be cut compared with when it is cut according to conventional findings. Furthermore, cutting efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam machine, and more particularly, to a laser beam machine capable of suitably cutting a workpiece having a thickness exceeding 20 mm.

[0002]

2. Description of the Related Art Conventionally, there has been known a laser processing machine having a laser oscillator for outputting a laser beam and a focus head for irradiating a laser beam output from the laser oscillator toward a workpiece. I have. In this type of laser beam machine, the workpiece is cut while the focus head and the workpiece are relatively displaced.

[0003]

Conventionally, it is generally considered that a single-mode laser beam having excellent light-collecting characteristics and a high power density is good for cutting with a laser beam. However, when the workpiece is an iron metal material such as a steel plate, the longer the thickness, the longer it takes to penetrate, and the assist gas (oxygen) is reduced in the narrow cutting groove width in the single mode. Burning in which the molten metal cannot be burned properly because it cannot enter the cut groove sufficiently, so the heat input to the molten metal increases and the temperature becomes too high, and the molten metal reacts excessively with oxygen and the molten metal scatters. This causes a phenomenon, resulting in processing failure. Therefore, conventionally, when cutting a thick steel plate workpiece, the beam mode is multi-mode to increase the width of the cutting groove, and furthermore, pulse oscillation is performed to achieve appropriate combustion of the molten metal and a reduction in heat input. (See Japanese Patent No. 2623355,
Japanese Patent Publication No. 5-49396). However, even when cutting a workpiece made of a thick steel plate with a multi-mode laser beam, a multi-mode laser beam having a relatively high power density has been selected based on conventional knowledge. More specifically, have selected a range of 2-5 when converted to M ² value is an index showing the quality of the laser beam. 1 M ² value is the way a laser beam of single mode, but all greater than 1 is a laser beam of a multi-mode, the power density as the value increases is made lower. However, in particular, when cutting a steel workpiece having a thickness of more than 20 mm, it has been difficult to suitably perform cutting with a multi-mode laser beam set according to conventional knowledge. The present invention has been made in view of such a situation, and is capable of suitably cutting a workpiece having a thickness exceeding 20 mm.

[0004]

That is, the present invention comprises a laser oscillator for oscillating a laser beam, and a focus head for irradiating a laser beam oscillated from the laser oscillator to a workpiece. and the laser beam machine by relatively moving the workpiece perform cutting of the workpiece, upon cutting the workpiece thickness exceeds 20 mm, the M ² value of the laser beam 7 or more A laser oscillator set in a range of 12 or less is used.

[0005]

[Action] In the range value of 7 to 12 of M ² described above, the distribution of the power density of the laser beam is equalized (flattening)
However, the divergence angle of the laser beam does not become too large,
Since it is suitable for cutting a workpiece having a thickness exceeding 20 mm, it is cut according to the conventional knowledge by using a laser oscillator capable of oscillating a laser beam having an M ² value in the range of 7 to 12. The cutting can be performed more favorably than in the case of processing, and the laser beam can be continuously oscillated, which was difficult in the past, so that the cutting efficiency can be improved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG. 1, a laser beam machine 1 includes a carbon dioxide laser oscillator 2 (hereinafter referred to as a laser oscillator 2) that oscillates a laser beam L, and The apparatus includes a focus head 4 containing a condenser lens 3 for condensing the oscillated laser beam L, and a processing table 8 on which a workpiece 7 made of a mild steel plate is placed. The laser oscillator 2, the cavity length so that laser beam L can oscillate a predetermined M ² value which is selected in the range of 7 to 12, aperture diameter, and the mirror curvature is constructed by selecting The output of the laser oscillator 2 is controlled by a control device (not shown). Either one or both of the focus head 4 and the processing table 8 are configured to be movable in the horizontal direction, and the relative movement in a horizontal plane is controlled by the control device. The head 4 and the workpiece 7 are relatively moved in a horizontal plane to cut the workpiece 7. Further, the focus head 4 is configured to be able to move up and down in the vertical direction, and the height position is controlled by the control device according to the focal length of the condenser lens 3. L is focused at a predetermined position in the thickness direction of the workpiece 7, while assist gas (oxygen) is blown from the tip of the focus head 4 toward the focus position.
Thus constructed laser processing apparatus 1, a laser beam L consisting of the laser oscillator 2 to a predetermined M ² value by the control device (not shown) made to oscillate at a predetermined output, condensing the laser beam L in the focusing head 4 Then, while irradiating the workpiece 7, the assist gas is blown out, and the focus head 4 and the workpiece 7 are relatively moved at an appropriate speed to perform cutting.

[0007] Thus, described selection of the M ² value by 9 in FIG. 2 showing the intensity distribution of the different M ² value of the laser beam L oscillated by the laser oscillator 2 having an output of 9kW below. First, when the M ² value shown in FIG. 2 is 6, the power density is dispersed, but the power density in the central portion still protrudes, and the portion with a high power density as a whole is closer to the center in the focused spot diameter. It can be seen that they are distributed. According to the laser beam having such an intensity distribution, even if the focused spot diameter is set so as to obtain a required cutting width, the width where the power effectively acts for cutting is actually smaller than that. Therefore, in a cutting test of the work piece 7 made of a mild steel plate having a thickness of more than 20 mm, particularly, a thickness of 25 mm, burning still easily occurs. In contrast, M
When 7 raised one ^binary to 6 (Fig. 3), since the distribution of power density with the protrusion of the power density is eliminated in the central portion as compared with the case M ² value is 6 spreads radially outward When the thickness exceeds 20 mm, the power acts almost uniformly on the cutting groove width (spot radius of about 0.5 ± 0.1 mm) required. Tendency to power density equalization for such cut groove width (flattening) will have a noticeable higher the M ² value as is apparent by reference to FIGS. 4-9. In addition, thickness is 20m
In the case of cutting the work piece 7 of a mild steel sheet exceeding m,
It is known from a cutting test that when the maximum value of the power density exceeds 1.5 × 10 ⁶ W / cm ² , burning is likely to occur.
When the diameter required for cutting 7 of the mild steel sheet exceeding 5 mm is used, the maximum value of the power density is 1.5 × 10 ⁶ W / cm ² or less if the M ² value of the laser beam L is 7 or more. It is clear that it will. Incidentally, it is known that the Rayleigh length of the laser beam is shortened in accordance with M ² value increases. When the Rayleigh length of the laser beam is shortened in this way, the change in the decrease in the power density increases as the distance from the focal point increases, and the power transmitted in the thickness direction of the workpiece 7 decreases, so that it is necessary to reduce the cutting speed. . However, if the cutting speed is reduced, the time for heat input to the molten metal in the cutting groove becomes longer, so that burning tends to occur. The above-mentioned Rayleigh length indicates the distance from the beam waist at which the beam radius of the laser beam becomes √2 times the beam waist radius. In the cutting test of the work piece 7 made of a mild steel plate having a thickness exceeding 20 mm, the Rayleigh length is shown. It has been experimentally obtained that the burning frequency increases when the distance is approximately 23 mm or less. In view of this experimental result, the Rayleigh length is shorter burning easily generated when is M ² value 13 shown in Figure 9, M ² value 12
Below (FIGS. 3 to 8), a good cutting result can be obtained. As understood from the above description, the object 7 of mild steel plate having a thickness greater than 20mm by using a laser oscillator 2 is set to M ² value in the range of 7 to 12 better to prevent burning Can be cut into pieces. In addition, since the laser beam L can be continuously oscillated at this time, which has been difficult in the past, the processing efficiency can be improved.

In the above embodiment, the case of 9 kW output has been described. However, the present invention is not limited to this, and the present invention can be applied to other outputs.
That is, generally, the output of the laser beam L is set to be higher as the thickness of the workpiece increases, but the intensity distribution of the power density indicated by the M ² value is not related to the output of the laser beam L. This is because they have almost the same shape. However, for example, when cutting the workpiece 7 made of a mild steel sheet having a thickness exceeding 30 mm and 40 mm, when the output of the laser beam L is 12 kW, the spot diameter of the laser beam L is 9 kW. Is the same as
The power density may exceed 1.5 × 10 ⁶ W / cm ² . However, in this case, even if the cutting groove width is increased, sufficient power in the thickness direction can be obtained by increasing the output power. By setting the value to be less than 10 ⁶ W / cm ² , an equalized intensity distribution can be obtained (see FIGS. 11 to 16, and FIG. 10 shows M ²
If the value is 6, FIG. 17 shows a case where M ² value is 13). On the other hand, even when the output is relatively low, specifically, when the output of the laser beam L is 5 kW, the power density as a whole is considered assuming that the focused spot diameter of the laser beam is the same as that at the time of 9 kW output. However, since the amount of heat input to the molten metal in the cutting groove decreases as the output decreases, the spot diameter is appropriately reduced, so that the power is almost uniformly applied to the cutting groove width. can be applied (see FIGS. 19 to 24, Note 18 when ^{M 2} value is 6, FIG. 25 shows a case where ^{M 2} value is 13). As understood from the above description, even when using a laser oscillator 2 having different output of the laser beam L in accordance with the thickness or machining conditions of the workpiece 7 of the mild steel plate to be cut, the M ² value 7 The same operation and effect as described above can be obtained by setting the number within the range of 12 or less.
Incidentally, the choose specifically which numeric M ² value in the range of 7 to 12, may be appropriately selected depending on the thickness and machining quality of the workpiece 7, conditions such as processing speed, which The laser processing machine 1 is configured using a laser oscillator corresponding to the above.

In the above embodiment, a carbon dioxide laser is used as the laser oscillator 2. However, the present invention is not limited to this, and other gas lasers or solid-state lasers such as YAG may be used.

[0010]

As described above, according to the present invention, 20 m
In the case of cutting a workpiece exceeding m, the cutting can be performed better than in the case of cutting according to conventional knowledge, and the processing efficiency can be improved by continuously oscillating a laser beam. The effect that improvement can be achieved is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic front view of a laser processing machine 1 according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a power density intensity distribution when an M ² value is set to 6 at the time of 9 kW output.

FIG. 3 is a characteristic diagram showing a power density intensity distribution when an M ² value is set to 7 at 9 kW output.

FIG. 4 is a characteristic diagram showing a power density intensity distribution when an M ² value is set to 8 at the time of 9 kW output.

FIG. 5 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 9 at the time of 9 kW output.

FIG. 6 is a characteristic diagram showing a power density intensity distribution when an M ² value is set to 10 at the time of 9 kW output.

FIG. 7 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 11 at the time of 9 kW output.

FIG. 8 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 12 at the time of 9 kW output.

FIG. 9 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 13 at the time of 9 kW output.

FIG. 10 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 6 at the time of 12 kW output.

FIG. 11 is a characteristic diagram showing an intensity distribution of power density when an M ² value is set to 7 at the time of 12 kW output.

[12] characteristic diagram showing the intensity distribution of the power density at the time of setting the M ² value to 8 during 12kW output.

FIG. 13 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 9 at the time of 12 kW output.

FIG. 14 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 10 at the time of 12 kW output.

FIG. 15 is a characteristic diagram showing the power density intensity distribution when the M ² value is set to 11 at the time of 12 kW output.

FIG. 16 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 12 at the time of 12 kW output.

FIG. 17 is a characteristic diagram showing an intensity distribution of power density when the M ² value is set to 13 at the time of 12 kW output.

FIG. 18 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 6 at the time of 5 kW output.

[19] characteristic diagram showing the intensity distribution of the power density at the time of setting the M ² value 7 at the time of 5kW output.

FIG. 20 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 8 at the time of 5 kW output.

FIG. 21 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 9 at the time of 5 kW output.

FIG. 22 is a characteristic diagram showing the intensity distribution of the power density when the M ² value is set to 10 at the time of 5 kW output.

FIG. 23 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 11 at the time of 5 kW output.

FIG. 24 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 12 at the time of 5 kW output.

FIG. 25 is a characteristic diagram showing a power density intensity distribution when the M ² value is set to 13 at the time of 5 kW output.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser machine 2 ... Laser oscillator 4 ... Focus head 7 ... Workpiece 8 ... Processing table L ... Laser beam

Continuation of the front page (72) Inventor Hideki Yamaguchi 58 Kou, Ozutahonmachi, Kanazawa-shi, Ishikawa F-term (reference) in Shibuya Corporation 4E068 AE00 CD05 DB01 5F072 AA05 HH03 JJ02 KK09 MM08 MM09 SS01 YY06

Claims (2)

[Claims] A laser oscillator for oscillating a laser beam;
A laser processing machine comprising: a focus head for irradiating a laser beam emitted from the laser oscillator toward a workpiece; and a cutting machine for cutting the workpiece by relatively moving the focus head and the workpiece. ^2. A laser processing machine according to claim 1, wherein a laser oscillator in which the M2 value of the laser beam is set in a range of 7 to 12 is used for cutting a workpiece having a thickness exceeding 20 mm. 2. The laser beam machine according to claim 1, wherein the maximum value of the power density of the laser beam is 1.5 × 10 ⁶ W / cm ² or less.