JP4340945B2 - Laser processing machine - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
2. Description of the Related Art Conventionally, a laser processing machine that includes a laser oscillator that outputs a laser beam and a focus head that irradiates a workpiece with the laser beam output from the laser oscillator is known.
In this type of laser processing machine, the workpiece is cut while the focus head and the workpiece are relatively displaced.
[0003]
[Problems to be solved by the invention]
By the way, conventionally, it is considered that a single mode laser beam having excellent light condensing characteristics and a high power density is preferable for a cutting process using a laser beam.
However, in the case where the workpiece is an iron metal material such as a steel plate, it takes time to penetrate as the thickness increases, and the assist gas (oxygen) is generated with a narrow cutting groove width by the single mode. Burning in which molten metal cannot be properly burned and the molten metal cannot be combusted appropriately, so the amount of heat input to the molten metal increases and the temperature becomes too high, and the molten metal scatters due to excessive reaction with oxygen. This causes a phenomenon that causes processing defects.
Therefore, conventionally, when cutting a thick steel plate workpiece, the beam mode is set to multi-mode to widen the cutting groove width, and further, pulse oscillation is performed to appropriately burn the molten metal and reduce the heat input. Burning is suppressed (Japanese Patent No. 2623355, Japanese Patent Publication No. 5-49396).
However, even when a thick steel plate workpiece is cut with a multimode laser beam, a multimode laser beam having a relatively high power density is selected in accordance with conventional knowledge.
More specifically, the range of 2 to 5 was selected when converted to an M ² value that is an index indicating the quality of the laser beam. Incidentally, an M ² value of 1 is a single-mode laser beam, and all of those greater than 1 are multi-mode laser beams, but the power density decreases as the value increases.
However, particularly when cutting a workpiece of a steel sheet having a thickness of more than 20 mm, it has been difficult to suitably cut with a multimode laser beam set according to conventional knowledge.
In view of such circumstances, the present invention is capable of suitably cutting a workpiece having a thickness exceeding 20 mm.
[0004]
[Means for Solving the Problems]
That is, the present invention includes a laser oscillator that oscillates a laser beam, and a focus head that irradiates a workpiece with the laser beam oscillated from the laser oscillator,
In a laser processing machine for cutting the workpiece by relatively moving the focus head and the workpiece,
When a workpiece having a thickness exceeding 20 mm is cut, a laser oscillator in which the M ² value of the laser beam is set in the range of 7 to 12 is used.
[0005]
[Action]
When the M ² value is in the range from 7 to 12, the power density distribution of the laser beam is equalized (flattened), but the divergence angle of the laser beam does not become too large, and the thickness exceeds 20 mm. Compared to the case of cutting according to conventional knowledge by using a laser oscillator that can oscillate a laser beam having an M ² value in the range of 7 or more and 12 or less because it is suitable for cutting a workpiece. Therefore, the cutting efficiency can be improved and the laser beam can be continuously oscillated, which has been difficult in the prior art, so that the cutting efficiency can be improved.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
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 a laser beam L oscillated from the laser oscillator 2. And a processing table 8 on which a workpiece 7 made of a mild steel plate is placed.
The laser oscillator 2 is configured by selecting a resonator length, an aperture diameter, and a mirror curvature so that a laser beam L having a predetermined M ² value selected within a range from 7 to 12 can be oscillated. The output of the laser oscillator 2 is controlled by a control device (not shown).
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 the horizontal plane is controlled by the control device. The workpiece 7 is cut by moving the head 4 and the workpiece 7 relative to each other in a horizontal plane.
Further, the focus head 4 is configured to be vertically movable, and the height position is controlled by the control device in accordance with the focal length of the condenser lens 3, whereby the laser beam The focus of L is connected 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.
The laser beam machine 1 configured as described above oscillates a laser beam L having a predetermined M ² value from the laser oscillator 2 with a predetermined output by the control device (not shown) and condenses the laser beam L with the focus head 4. Then, the assist gas is blown out while irradiating the workpiece 7, and the focus head 4 and the workpiece 7 are relatively moved at an appropriate speed to perform the cutting process.
[0007]
Accordingly, selection of the M ² value will be described below with reference to FIGS. 2 to 9 showing intensity distributions of different M ² values of the laser beam L oscillated from the laser oscillator 2 having an output of 9 kW.
First, when the M ² value shown in FIG. 2 is 6, although the power density is dispersed, the power density at the center portion still protrudes, and the portion with a high power density as a whole is closer to the center of the focused spot diameter. It can be seen that they are distributed.
According to the laser beam showing such an intensity distribution, even if the condensing spot diameter is set so that a necessary cutting width can be obtained, the width in which the power effectively acts for cutting is actually narrower than that. Therefore, in the cutting test of the workpiece 7 of a mild steel plate having a thickness of more than 20 mm, particularly a thickness of 25 mm, burning still tends to occur.
On the other hand, when the M ² value is increased from 6 to 7 (FIG. 3), the central portion does not have a protruding power density and the power density distribution is in the radial direction as compared with the case where the M ² value is 6. Since it spreads outward, the power acts almost uniformly on the cutting groove width (spot radius of about 0.5 ± 0.1 mm) required when the plate thickness exceeds 20 mm. Thus, the tendency that the power density is equalized (flattened) with respect to the cutting groove width becomes more prominent as the M ² value is increased, as is apparent from FIGS. 4 to 9.
Further, in the case of cutting the workpiece 7 of a mild steel plate having a thickness exceeding 20 mm, cutting is likely to occur when the maximum power density exceeds 1.5 × 10 ⁶ W / cm ^2. It is known from the test, and when the focused spot diameter is set to a diameter necessary for the cutting 7 of the mild steel plate having a thickness exceeding 20 mm as described above, the M ² value of the laser beam L is 7 or more. It is also clear that the maximum value of the power density is 1.5 × 10 ⁶ W / cm ² or less.
By the way, it is known that the Rayleigh length of a laser beam becomes shorter as the M ² value becomes larger. Thus, when the Rayleigh length of the laser beam is shortened, the change in the power density decreases as the distance from the focal point increases, and the power transmitted in the thickness direction of the workpiece 7 becomes weak, so that it is necessary to slow down the cutting speed. . However, if the cutting speed is slowed, the heat input time to the molten metal in the cutting groove becomes long, so that burning tends to occur.
The Rayleigh length indicates a distance from the beam waist where the beam radius of the laser beam becomes √2 times the beam waist radius. In the cutting test of the workpiece 7 of the mild steel plate having a thickness exceeding 20 mm, the Rayleigh length Experimental results show that the occurrence frequency of burning increases when the value is approximately 23 mm or less. Considering this experimental result, if the M ² value shown in FIG. 9 is 13, the Rayleigh length is short and burning is likely to occur, and if the M ² value is 12 or less (FIGS. 3 to 8), a good cutting result is obtained. Can be obtained.
As can be understood from the above description, by using the laser oscillator 2 in which the M ² value is set in the range of 7 or more and 12 or less, it is possible to prevent the workpiece 7 of the mild steel plate having a thickness exceeding 20 mm from being burned. 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 prior art, the processing efficiency can be improved.
[0008]
In the above embodiment, the case of 9 kW output has been described. However, the present invention is not limited to this, and can be applied to other outputs.
That is, in general, the output of the laser beam L is generally set so as to increase as the thickness of the workpiece increases. However, the intensity distribution of the power density indicated by the M ² value is 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 of a mild steel plate having a thickness exceeding 30 mm or 40 mm, when the output of the laser beam L is 12 kW, the spot diameter of the laser beam L is 9 kW. , The power density may exceed 1.5 × 10 ⁶ W / cm ² . However, in this case, the power in the thickness direction can be sufficiently obtained even if the cutting groove width is widened as the output is increased, so the diameter of the focused spot is appropriately increased to increase the power density to 1.5 ×. By setting it to be less than 10 ⁶ W / cm ² , it is possible to obtain an equalized intensity distribution (see FIGS. 11 to 16, where FIG. 10 shows an M ² value of 6, FIG. ^This shows the case where the binary value is 13.
On the contrary, 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 assumed to be the same as when the laser beam has a focused spot diameter of 9 kW. However, since the amount of heat input to the molten metal in the cutting groove is reduced by the amount of output reduction, the spot diameter is appropriately reduced, so that the power is substantially even with respect to the cutting groove width. (See FIGS. 19 to 24, FIG. 18 shows a case where the M ² value is 6, and FIG. 25 shows a case where the M ² value is 13.)
As understood from the above description, even when the laser oscillator 2 having a different output of the laser beam L is used in accordance with the thickness of the workpiece 7 of the mild steel sheet to be cut or the processing conditions, the M ² value is set to 7 By setting in the range of 12 or less, the same effect as described above can be obtained.
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 beam machine 1 is configured using a laser oscillator corresponding to the above.
[0009]
In the above embodiment, a carbon dioxide laser is used as the laser oscillator 2, but the present invention is not limited to this, and other gas lasers or solid lasers such as YAG may be used.
[0010]
【The invention's effect】
As described above, according to the present invention, when a workpiece exceeding 20 mm is cut, it can be cut more favorably than when cutting according to conventional knowledge. The effect that the processing efficiency can be improved by continuously oscillating the laser beam is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic front view of a laser beam 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 9 kW output.
FIG. 3 is a characteristic diagram showing an intensity distribution of power density when an M ² value is set to 7 at 9 kW output.
FIG. 4 is a characteristic diagram showing an intensity distribution of power density when the M ² value is set to 8 at 9 kW output.
FIG. 5 is a characteristic diagram showing an intensity distribution of power density when an M ² value is set to 9 at the time of 9 kW output.
FIG. 6 is a characteristic diagram showing the power density intensity distribution when the 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 an M ² value is set to 11 at 9 kW output.
FIG. 8 is a characteristic diagram showing the 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 the 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 the intensity distribution of power density when the M ² value is set to 6 at 12 kW output.
FIG. 11 is a characteristic diagram showing an intensity distribution of power density when the M ² value is set to 7 at 12 kW output.
FIG. 12 is a characteristic diagram showing an intensity distribution of power density when the M ² value is set to 8 at 12 kW output.
FIG. 13 is a characteristic diagram showing the intensity distribution of power density when the M ² value is set to 9 at 12 kW output.
FIG. 14 is a characteristic diagram showing the power density intensity distribution when the M ² value is set to 10 at 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 12 kW output.
FIG. 16 is a characteristic diagram showing the power density intensity distribution when the M ² value is set to 12 at 12 kW output.
FIG. 17 is a characteristic diagram showing the intensity distribution of power density when the M ² value is set to 13 at 12 kW output.
FIG. 18 is a characteristic diagram showing the intensity distribution of power density when the M ² value is set to 6 at the time of 5 kW output.
FIG. 19 is a characteristic diagram showing the power density intensity distribution when the M ² value is set to 7 at the time of 5 kW output.
FIG. 20 is a characteristic diagram showing the 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 the 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 power density intensity distribution when the M ² value is set to 10 at the time of 5 kW output.
FIG. 23 is a characteristic diagram showing the intensity distribution of power density when the M ² value is set to 11 at the time of 5 kW output.
FIG. 24 is a characteristic diagram showing the 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 the intensity distribution of power density when the M ² value is set to 13 at the time of 5 kW output.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Laser processing machine 2 ... Laser oscillator 4 ... Focus head 7 ... Workpiece 8 ... Processing table L ... Laser beam

Claims (2)

A laser oscillator that oscillates the laser beam, and a focus head that irradiates the workpiece with the laser beam oscillated from the laser oscillator;
In a laser processing machine for cutting the workpiece by relatively moving the focus head and the workpiece,
A laser processing machine using a laser oscillator in which an M ² value of the laser beam is set in a range of 7 or more and 12 or less when 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.

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