JP3534807B2 - Laser cutting method - Google Patents

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 for irradiating a work with a laser beam and cutting the work with the energy of the laser beam.

[0002]

2. Description of the Related Art Conventionally, as a laser cutting method of this type, for example, first, as shown in Japanese Patent Application Laid-Open No. 2-303695, the temperature of an object to be processed is lowered at the tip of an edge of a corner portion. One in which the irradiation of the laser beam is once stopped and cooled by a gas or a liquid, and then the laser beam is again irradiated from the same position to restart the processing, or secondly, as disclosed in JP-A-4-237582. In order to avoid the effect of heat accumulation on the workpiece, the cutting condition may be changed near the corner.

[0003]

Since the conventional laser cutting method is constructed as described above, the first laser cutting method can suppress the melting loss to some extent, but it is a thin plate (soft rope, SS400). In the case of about 4.5 mm or less), a thicker plate has almost no effect. That is,
Although the work temperature can be lowered by cooling, the speed rises from 0 when the corner rises, and the moving speed of the laser beam becomes extremely unstable. Therefore, there is a range in which the laser beam output and the laser beam moving speed cannot be balanced, resulting in excessive heat input or insufficient heat input to the work. Therefore, there is a problem that abnormal cutting or insufficient combustion occurs at the lower part of the plate during cutting, resulting in melting loss.

FIG. 31 is an explanatory view of the second laser cutting method. In FIG. 31, 2 is a workpiece, 2a is a cutting groove, arrow 21 is a cutting proceeding direction, and PW is a cutting region by a low frequency pulse. , CW is a cutting region by a continuous wave or a high frequency pulse. This laser cutting method is shown in FIG.
As shown in (a), the machining conditions are changed a few millimeters before the corner, the corner is cut under the changed machining conditions, the machining conditions are changed again after passing the corner for several millimeters, and before the corner is cut. 31 (b) and the method of returning to the processing conditions of FIG.
As shown in, the cutting condition is changed at the edge of the corner, the corner is cut under the changed cutting condition, the cutting condition is changed again after passing a few millimeters, and the cutting condition before cutting the corner is changed. There is a method to return to.

The modified processing conditions in these two methods are, for example, the processing conditions for cutting near the corners are low frequency pulse conditions. Therefore, the state of the cut surface under high-speed processing conditions (for example, continuous wave output, high frequency pulse output) before and after the corner portion is different from the state of the cut surface at the time of low frequency pulse. In particular, the surface cut by the low-frequency pulse causes red rust on the surface. Due to such a change in the state of the cut surface, the processing quality is slightly deteriorated. Further, when the processing conditions are changed, defects such as scratches, disordered streaks, and burn through are likely to occur near the switching point, and the avoidance thereof becomes a problem. Further, since the low-frequency pulse processing condition is very low, there is a problem that the processing time increases.

The invention of claim 1 has been made to solve the above problems, and an object thereof is to prevent melting damage at the corner portion.

An object of the present invention is to accurately cut the corner portion.

It is an object of the invention of claim 3 to prevent melting damage at the corner portion even if the plate becomes thick.

An object of the invention of claim 4 is to shorten the processing time.

It is an object of the present invention to stabilize the cutting of the corner portion of a thick plate.

An object of the invention of claim 7 is to enable forced cooling easily.

The invention of claim 8 aims to increase the efficiency of the cooling effect.

An object of the invention of claim 9 is to shorten the processing conditions even when the plate thickness is increased.

The invention of claim 10 aims at shortening the processing time.

It is an object of the present invention to prevent melting damage even at an acute-angled corner portion.

[0016]

A thirteenth aspect of the present invention is intended to prevent melting damage even at an acute-angled corner portion.

[0018]

In the laser cutting method according to the first aspect of the present invention, when a position specified on the program of the corner portion is reached at the time of corner cutting, the same route as that used for cutting is retracted. Then, when you reach the position specified in the program on that route, advance the route again,
It is for corner cutting.

In the laser cutting method according to the second aspect of the invention, the position for starting the retreat designated by the program is set before the corner by the distance required for the falling of the cutting speed.

A laser cutting method according to a third aspect of the present invention irradiates a beam while temporarily stopping at a beam arrival position at the time of first cutting, and a laser cutting method according to the fourth aspect of the invention. The beam irradiation time is specified.

In the laser cutting method according to the present invention, the movement of the laser irradiation nozzle is stopped and the cooling time is taken while the laser irradiation is stopped.

According to a sixth aspect of the present invention, there is provided a laser cutting method, wherein the beam irradiation is interrupted during the entire process from the start of cutting to the end of cutting, while the laser irradiation nozzle and the workpiece are being moved, Alternatively, by spraying a liquid, the periphery of the first cut groove is cooled.

According to a seventh aspect of the present invention, there is provided a laser cutting method, wherein a gas for cooling an assist gas used for laser processing is kept in a state where the laser irradiation is stopped and the laser irradiation nozzle and the workpiece are relatively moved. It is sprayed around the cutting groove during movement.

In the laser cutting method according to the eighth aspect of the invention, the movement of the laser irradiation nozzle is stopped and the position at which the assist gas is blown is defined at the tip of the cutting groove in the first step of the first aspect. The laser cutting method according to the invention of claim 9 defines the spraying time.

In the laser cutting method according to the tenth aspect of the invention, the necessary retreat distance in the first step based on the first to ninth aspects of the invention is set by the material, plate thickness, and machining shape of the workpiece. Depending on the type, it can be set arbitrarily.

In the laser cutting method according to the eleventh aspect of the present invention, the cutting advancing direction is changed to a right angle after changing the cutting advancing direction to an obtuse angle, or the cutting advancing direction is changed to an obtuse angle after changing the cutting advancing direction to a right angle. It is changed to cut an acute-angled corner portion.

In the laser cutting method according to the twelfth aspect of the present invention, when the beam axis reaches the corner portion, the cutting path so far is retracted, the beam path is advanced again to the corner portion along the cutting path, and an acute angle is formed. The corners are cut into right angles and obtuse angles.

[0028]

According to a thirteenth aspect of the present invention, there is provided a laser cutting method in which a space having a width equal to or larger than a cutting groove width is provided on an extension of the cutting proceeding direction up to the corner, or a direction opposite to the cutting proceeding direction at the corner rising. A space having a width larger than the width of the cutting groove is provided on the extension of.

[0030]

In the laser cutting method according to the present invention, the beam is moved backward and forward along the cutting groove that has been once formed, and after cutting the normal front corner,
Unlike the case where the corner rising is continuously cut, melting damage of the corner portion due to the delay of the cutting front surface does not occur.
In addition, by setting a sufficient distance for advancing again, the beam moving speed reaches the set value, and excessive heat input or insufficient heat input does not occur during cutting.

In the laser cutting method according to the second aspect of the present invention, the position where the retreat is first started is set in front of the corner by the distance required for the falling of the cutting speed, so that the outer portion of the corner can be accurately controlled. Can be cut well.

The laser cutting method according to the third aspect of the invention is temporarily stopped, and in the fourth aspect of the invention, the beam irradiation is continued by defining the stop time, so that the workpiece can be thick even if it is thick. A cut surface is obtained.

In the laser cutting method according to the fifth aspect of the present invention, the laser irradiation is stopped, the relative speed of the laser irradiation nozzle and the workpiece is stopped, and cooling time is taken, so that the corner is cut even if the workpiece is thick. Can be prevented from melting.

In the laser cutting method according to the sixth aspect of the invention, in the process of retracting and cutting the corner, the temporary beam irradiation is interrupted, and the beam moving locus is cooled by a gas or a liquid, so that the corner is cut. The cutting can be stable.

In the laser cutting method according to the seventh aspect of the present invention, forced cooling can be easily performed by blowing the assist gas around the cutting groove.

In the laser cutting method according to the eighth aspect of the present invention, the efficiency of the cooling effect is improved by designating the place where the assist gas is blown.

In the laser cutting method according to the ninth aspect of the invention, the cooling time can be set efficiently and the processing time can be shortened by defining the blowing time of the assist gas.

In the laser cutting method according to the tenth aspect of the invention, the processing time can be shortened by setting the minimum required retreat amount according to the processing conditions and the shape of the workpiece.

In the laser cutting method according to the eleventh and twelfth aspects of the present invention, the sharp corner can be accurately cut by dividing the sharp angle into a right angle and an obtuse angle.

[0040]

In the laser cutting method according to the thirteenth aspect of the present invention, since a space having a width equal to or larger than the cutting groove width is provided on the extension of the cutting proceeding direction, cutting can be performed accurately without melting loss even at an acute corner.

[0042]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an apparatus for carrying out a laser cutting method according to the present invention. In FIG. 1, 1 is a laser beam, 2 is a workpiece, 3 is a mirror for reflecting the laser beam 1, 4 is a laser. Processing lens for focusing beam 1, 5
Is a processing head for accommodating the processing lens 4 and ejecting a gas or a liquid 6 as a cooling medium from a nozzle 5a at the tip, 7
Is a processing table on which the workpiece 2 is placed and which can be moved in the orthogonal axes X, Y, and Z, and 8 is a CPU 8a as an arithmetic control means.
A servo control circuit 9 that receives an instruction signal from the NC device 8 and drives the machining table 7 in the orthogonal axis direction is a laser oscillator that generates a laser beam 1.

The calculation and control for carrying out the laser cutting method according to the present invention are performed by the CPU 8a, and the basic processing thereof is steps ST2-1 to ST2-4 shown in FIG. 2 (a). Program MP-1 at the start of laser beam movement, program MP-2 at steps ST2-5 to ST2-8 shown in FIG. 2B when the laser beam movement is stopped, and step ST2 shown in FIG. 2C.
Perform the program MP-3 when changing the cutting advancing direction at the corners from -9 to ST2-14.

As auxiliary processing, the program SP-1 at the time of laser beam off of steps ST3-1 to ST3-4 shown in FIG. 3A, and steps ST3-5 to ST3 shown in FIG. 3B. -8 program SP-2 when the laser beam is turned on, steps ST3-9 to ST3-9 shown in FIG.
Program SP for changing assist gas pressure in ST3-12
-3, a program SP-4 for holding any time in steps ST3-13 and 14 shown in FIG. 3D, and an in-position state when the laser beam movement is stopped in steps ST3-15 and 16 shown in FIG. Program SP-5 is executed.

In addition, as the arithmetic processing, a calculation program CP-1 for calculating the distance traveled when the speed Fs falls at the time t shown in FIG. 4A, and the C shown in FIG. 4B.
A calculation program CP-2 for shortening the movement distance by the distance obtained in P-1 and a calculation program CP-3 for the laser beam movement distance L at the corner shown in FIG.

Then, the above basic processes MP-1 to M
The laser cutting method of the present invention is executed by combining P-3, auxiliary processes SP-1 to SP-5, and calculation programs CP-1 to CP-3. Therefore, MP-1, SP-1, CP- described in the flowcharts corresponding to each claim
1 etc. have shown each said process.

FIG. 5 is a schematic view showing a laser beam cutting method according to an embodiment of the invention described in claim 1. In FIG. 5, 2a is a cutting groove, A is a cutting direction changing position designated by a program in advance, and B is a cutting direction changing position. Is the position to start re-advancing when retreating,
R is the position where the cutting direction is actually changed.

5 (1) shows the state during cutting, FIG. 5 (2) shows the state where the laser beam 1 has reached the position A designated by the program in advance, and FIG. 5 (3) shows the state when the laser beam 1 is used. 5 (4) shows a state in which the laser beam 1 is retracted along the same path in the formed cutting groove 2a, and FIG. 5 (4) shows a state in which the laser beam 1 is retracted to the position B determined by the position A preprogrammed. The backward movement from the position A to the position B may be performed at either the processing speed or the rapid feed speed. The processing states from (1) to (4) above are the first step. FIG. 5 (5) shows a state in which the laser beam 1 has reached the position R where the cutting advancing direction actually starts to change, while FIG.
(7) shows a state in which the laser beam 1 has risen at the corner after the change of the cutting advancing direction is completed. The above-mentioned processing states (5) to (7) are the second step. A flow chart showing the above operation sequence is shown in FIG.

One of the reasons why the laser cutting method of the first embodiment can suppress the melting loss is that when the laser beam 1 reaches the position A in FIG. 5, the beam moving speed decelerates slightly from the front to stop. Therefore, the heat input is temporarily increased and the delay of the cutting front is eliminated. Furthermore, once the beam moves backward and forward and the beam moving speed reaches the set speed, the path at the corner becomes smooth and the melt flow is not interrupted. Unlike the conventional example, the speed does not become 0, This is because excessive heat input does not occur when the corner rises. In actuality, the stereoscopic microscope was used to measure the amount of melt loss at the corners, and a burn-through amount of up to 1 mm was considered good.

When 50 samples were each cut by the laser cutting method of the first embodiment and the conventional laser cutting method of cooling by the corner, the defect occurrence rate was 40% in the conventional method, while the conventional method was used. It was 2% in the method of No. 1, and the defect occurrence rate was greatly improved.

At this time, mild steel (SS40
0) was used, the plate thickness was 6 mm, and the angle of the corner to be cut was 90 degrees. The output of CO2 laser is 1.3.
Continuous wave (CW) of kW, oxygen gas (gas pressure 1.0 kg / cm ² ) as assist gas, and processing speed 1.5
Processing was performed at mm / min. At this time, the distance (retraction distance) between the positions A and B in FIG. 5 was set to 10 mm, and when the position A was set to the edge portion by the numerical control device, the direction change was actually 500 μm before the position A. did.

Example 2. FIG. 7 is a schematic diagram showing a laser cutting method according to an embodiment of the invention as set forth in claim 2.
Is a flowchart showing an operation sequence.

In the first embodiment, as shown in FIG. 5 (7), the corner is formed before the tip of the first cut groove. In the second embodiment, in order to prevent such a situation, as shown in FIG. 7, a distance l required for falling the laser beam moving speed is obtained in advance, and the distance l is obtained.
Is set in front of the desired corner position A. In FIG. 7, 1-1 indicates the laser beam position when the direction change is actually started, and 2-1 indicates the tip of the cutting groove formed first.

As a specific example, the distance l from the position A described in the first embodiment to the actual start point of the direction change coincides with the distance required from the start of deceleration of the table speed to the completion of the fall. Based on the first embodiment, the position A set by the numerical controller is set to 0.5 mm more than that in the first embodiment.
(500 μm). By such an operation, the outer portion of the corner could also be cut into a good state.

Note that this operation is referred to as overshooting, and the operating distance l is referred to as an overshoot amount. Figure 7 shows the overshoot amount
As shown in, it is determined by the laser beam moving speed and the time required from the start of deceleration of the laser beam moving speed to the completion of falling.

Example 3. Due to the effect of the temporary excessive heat input at the time of the fall of the laser beam moving speed as described above, the delay of the cutting front can be eliminated up to a certain thickness. However, in the case of thick plates, the delay of the cutting front face cannot be eliminated only by the time of this speed change (the delay of the cutting front face 2-1 is about 0.6 mm at a plate thickness of 6 mm and about 0.9 m at a plate thickness of 9 mm.
m, plate thickness 12 mm, about 1.3 mm, and so on. Therefore, if the laser beam is surely moved to a position designated in advance (position A in FIG. 5) and the delay is not eliminated by laser beam irradiation, the beam is again moved along the same path and the corner is eliminated. Melting loss occurs due to the delay.

In order to solve the above-mentioned problems, the invention according to claim 3 surely decelerates and stops when the laser beam 1 reaches a position designated in advance by the operation sequence shown in the flowchart of FIG. It is provided with a step of performing the next movement after irradiation with the laser beam. In the case where the beam surely moves to a position A designated in advance in FIG. 5 and then stops, and the laser beam is irradiated, the beam moves to the next movement.
Comparing the defect occurrence rate at the corners when 50 deceleration stop commands are not specified on the program, it is 4% in the case of the method of the third embodiment.
It was 28% by the latter method.

However, mild steel (SS40
0) was used, the plate thickness was 9 mm, and the angle of the corner to be cut was 90 degrees. The output of the CO ₂ laser is 1.2
Continuous wave (CW) of kW, oxygen gas (gas pressure 1.0 kg / cm ² ) as assist gas, and processing speed 1.0
Processing was performed at mm / min. In addition, the amount of overshoot was 300 μm and the receding distance was 10 mm.

Example 4. FIG. 10 is a flow chart showing the operation sequence of the laser cutting method according to the fourth embodiment of the invention, and FIGS. 11 and 12 are cutting characteristic diagrams according to the present embodiment. As described above, the thicker the plate thickness of the work piece 2 is, the more difficult it is to eliminate the delay of the cutting front surface 4a, and the more difficult it is to suppress the melting loss. Therefore, in order to more positively eliminate the delay on the cutting front surface, the laser beam 1 is stopped at the position A in FIG. Figure 1
1 is a work piece 2 and has a plate thickness of 12 m of mild steel (SS400)
It shows the stop time and the difference (delay) between the upper part and the lower part of the cutting front in the case of m, 16 mm, 19 mm, and 25 mm.

When the plate thickness is 12 mm (circled in FIG. 11), CO
The continuous wave (CW) of 1.4 kW was used for the output of ₂ lasers, and the oxygen gas (0.6 kg / cm ² ) was used as the assist gas.
Processing was performed at a processing speed of 0.8 m / min. Board thickness 16m
m (square mark in FIG. 11), the output of the CO ₂ laser is 2.
Continuous wave (CW) of 2 kW, oxygen gas (0.5 kg / cm ² ) as assist gas, and processing speed 0.8 m / m
Processed in. (In FIG. 11, triangles) thickness 19mm in CO ₂ laser continuous wave 2.5kW output of (C
W), oxygen gas as an assist gas (0.4 kg / cm
^{Using 2} ), processing was performed at a processing speed of 0.7 m / min. With a plate thickness of 25 mm (marked with X in FIG. 11), a continuous wave (CW) of 3.0 kW was used as the output of the CO ₂ laser, and oxygen gas (0.7 kg / cm ² ) was used as the assist gas, and the processing speed was 0.65 m / min. Was processed in.

Furthermore, the plate thickness of mild steel (SS400) is 12 m.
FIG. 12 shows changes in the amount of melting loss at the corners when m is actually machined according to the laser cutting method of Example 1 at the respective stop times in FIG. 11 under the above-mentioned machining conditions. As a result, the laser beam 1 is irradiated for a long time, and the cutting front surface 2-1
The amount of melt-through was reduced by reducing the delay of. Moreover, after irradiation for a certain period of time, the delay amount did not decrease.
As a result, the irradiation time of the laser beam 1 is 10 seconds or less. The overshoot amount at this 12 mm is 25
The retreat distance was 0 μm and the retreat distance was 10 mm.

Example 5. FIG. 13 is a flow chart showing the operation sequence of the laser cutting method according to an embodiment of the invention described in claims 5, 6 and 7, and FIGS. 14 and 15 are cutting characteristic diagrams according to the fifth embodiment. As described above, as the plate thickness of the work piece 2 increases, in order to eliminate the delay of the cutting front surface 2-1, the time during which the laser beam 1 is continuously irradiated is longer, but the stop time is longer. Then, the workpiece 2 was excessively heated, and the melting loss could not be suppressed.

FIG. 14 shows a mild steel (SS40 as the workpiece 2).
The plate thickness of 0) is 16 mm, and the output of the CO ₂ laser is 2.2 kW.
Continuous wave (CW), oxygen gas (gas pressure 0.5 kg / cm ² ) as assist gas, and processing speed 0.8 m / m
In, the overshoot amount is 250 μm, the retreat distance is 1
The stop time and the amount of melting loss are shown by taking the case of processing at 0 mm as an example.

Therefore, after stopping and irradiating the laser beam for a certain period of time, while the laser beam irradiation processing head 5 is moving, Ar gas or the like is blown by the ejection device 11 as shown in FIG. 16 to cool the workpiece 2. . As a result, melting loss can be suppressed even in the workpiece 2 having a large plate thickness.

With respect to the plate thicknesses of 16 mm and 19 mm of mild steel (SS400) as the workpiece 2, the defect occurrence rate of the corners when cooled is 2% at 16 mm and 4% at 19 mm, and the laser beam is not cooled for the same time. When irradiated, it was 42% at 16 mm and 56% at 19 mm.

However, the number of samples is 50 and the plate thickness is 16
mm, the output of the CO ₂ laser is 2.2 kW continuous wave (C
W), oxygen gas as assist gas (gas pressure 0.5 kg
/ Cm ² ), the processing speed was 0.8 m / min, the overshoot amount was 250 μm, and the receding distance was 10 mm. When the plate thickness is 19 mm, the CO ₂ laser output is 2.
Continuous wave (CW) of 5 kW, oxygen gas (gas pressure 0.4 kg / cm ² ) as assist gas, and processing speed 0.7
Processing was performed at m / min with an overshoot amount of 220 μm and a receding distance of 10 mm.

The time for irradiating the laser beam and stopping is 1
6 mm was 4 seconds and 19 mm was 5 seconds. In addition, the failure occurrence rate was 94% in the case of not stopping at all. In this case, a similar effect was obtained even when cooling was performed using a liquid such as water instead of gas. However, in the case of a liquid, secondary work such as drying after cooling is required.

As a cooling method as described above, after stopping the laser beam and moving the laser beam irradiation processing head 5 while ejecting an assist gas such as N ₂ or O ₂ from the tip nozzle 5a of the processing head 5, A sufficient cooling effect was obtained. Further, when the assist gas pressure was made higher than during processing, the cooling action was further increased.

FIG. 15 shows the corner portion of the case where the plate thickness is 16 mm and the assist gas pressure during cooling is changed (circles: 1 kg / cm ² , squares: kg / cm ² , triangles: 3 kg / cm ² ). It shows changes in the amount of erosion loss, and if N ₂ or O ₂ that is often used as an assist gas is cheaper than Ar, and unlike liquids, it also requires a secondary operation such as drying after cooling. Moreover, it is simple because it can be ejected with the same system as when cutting.

Example 6. FIG. 17 is a flow chart showing the operation sequence of a laser cutting method according to an embodiment of the present invention described in claims 8 and 9, and FIGS. 18 and 19 are cutting characteristic diagrams according to the sixth embodiment. Although the above is the method of cooling the laser beam irradiation processing head 5 while moving, the cooling effect can be obtained even if the assist gas is jetted for a certain period of time while the movement of the laser beam irradiation processing head 5 is stopped. FIG. 18 shows changes in the stop position and the amount of melting loss. As a work piece, mild steel (SS40
0) with a plate thickness of 19 mm, a continuous wave (CW) of 2.5 kW was used for the output of the CO ₂ laser, and oxygen gas (gas pressure 0.4 kg / cm ² ) was used as an assist gas at a processing speed of 0.7 m / min. , The overshoot amount is 220 μm,
Processing was performed with a retreat distance of 10 mm. The gas pressure during the stop was 1.0 kg / cm ² ) and the stop time was 3 seconds.

A and B in FIG. 18 are positions A and B in FIG.
And H is the middle of positions A and B in FIG. In this way, even if the cooling is stopped and cooled, the cooling effect can be obtained as in the case of cooling while moving, but it was found that the cooling effect is particularly high when the cooling is performed at the position A (beam irradiation time is 5 seconds). .

Further, in FIG. 19, as a workpiece, mild steel (SS
400), using plate thicknesses of 19 mm and 25 mm, the assist gas pressure was changed with respect to the cooling time at the position A in FIG. 5 and the melting loss occurrence rate (circles: 1 kg / cm ² , squares: 2 k).
g / cm ² , triangle mark 3 kg / cm ² ) (beam irradiation time was 5 seconds). From this, it has been found that if the assist gas pressure is increased, the defect rate is reduced in a short time, but if the time is extended to some extent, the defect rate is improved even if the pressure is not so high. It can be said that it is better to take a little longer cooling time at low pressure to reduce gas consumption. From this result, it was found that the cooling time may be 10 seconds or less even if the assist gas pressure is a low pressure set as the processing condition.

The processing conditions at this time were such that a continuous wave (CW) of 2.5 kW was used for the output of the CO ₂ laser, oxygen gas (gas pressure 0.4 kg / cm ² ) was used as the assist gas, and the processing speed was 0.7 m. / Min, the overshoot amount is 220
The processing was performed with a μm and a retreat distance of 10 mm. Plate thickness 25m
At m, the output of CO ₂ laser is 3.0 kW continuous wave (C
W), oxygen gas as an assist gas (0.7 kg / cm
² ) was used, the processing speed was 0.65 m / min, the overshoot amount was 210 μm, and the retreat distance was 10 mm.

Example 7. 20 is a cutting characteristic diagram showing a laser cutting method according to an embodiment of the present invention. In order to shorten the processing time, it is necessary to set the retreat distance to an appropriate value based on the data described so far. The factor that determines this distance is that the laser beam moving speed reaches a steady state when the laser beam reaches the edge portion. Therefore, it is necessary to set the retreat distance in consideration of the distance required for the rise of the laser beam moving speed in advance. This distance is determined by the moving speed of the laser beam in the steady state and the time required from the speed 0 to the completion of rising, and in this case, it is determined based on the following equation. Fa = F {1-EXP (-t / λ)} Fa: Speed at time t F: Beam moving speed t set by numerical control t: Time from start of rising λ: Time constant of speed The above equation is integrated. That is, the distance required for rising is obtained by obtaining the area of the shaded portion in FIG. The thick plate is processed at low speed as described so far,
The thin plate is processed at high speed.

Actually, 1.0 mm of mild steel SPCC and SS
Taking the maximum practical speed for each of 25 mm of 400 and 1.0 mm of aluminum as an example, the distance required for rising is calculated from the above formula.
0 mm is about 1.7 mm, SS400 25 mm is about 0.1 mm.
2 mm, 1.0 mm of aluminum was about 0.7 mm. By setting the retreat distance from these values, each workpiece will not burn through the corners,
It was possible to cut at high speed. Therefore, the receding distance is determined by the material of the workpiece, the plate thickness, and the processed shape. However, the processing speed when SPCC is 1.0 mm is 5.0 m.
The processing speed at m / min and SS400 of 25 mm was 0.65 m / min, and the processing speed at 1.0 mm of aluminum was 2.0 mm / min.

Example 8. One of the causes of melting loss in acute-angle cutting is that when a new cut is made at the time of rising of a corner portion, the heat source behaves as if it advances to the acute-angle side as indicated by arrow G in FIG. Therefore, the molten metal at the time of cutting flows toward the acute-angled edge portion. This causes burn-through at the edge portion. In the eleventh aspect, paying attention to this point, and capturing the acute angle as an assembly of a right angle and an obtuse angle, the direction of the flow of the molten metal according to the behavior of the heat source is controlled.

FIG. 22 is a flow chart showing the operation sequence of the laser cutting method according to the eleventh aspect of the present invention, and FIG. 23 is a schematic view showing the laser cutting method.
When moving from an obtuse angle to an acute angle (or from an acute angle to an obtuse angle), if the distance traveled by the laser beam is too long, the edge will disappear, and if it is too short, it will be similar to the acute corner cutting by the conventional laser cutting method, causing melting damage. . Therefore, it is necessary to calculate an appropriate length from the cutting groove width and the angle.

From this right angle to the obtuse angle (or from the obtuse angle to the right angle)
At the time of transition to
Cutting was performed according to the laser beam cutting method according to the invention described in claims 1 and 2 described above. FIG. 24 is a flow chart showing the operation sequence of the laser cutting method according to this embodiment, and FIG. 25 is a schematic view showing the laser cutting method. Comparing the defect occurrence rate between this laser cutting method and the conventional laser cutting method for cooling the corners with 50 samples, it is 6% in the method of this embodiment, whereas it is 7 in the conventional method.
It was 0%.

However, mild steel (SS40
0) was used, the plate thickness was 9 mm, and the angle of the corner to be cut was 60 degrees. The output of the CO ₂ laser is 1.2
Continuous wave (CW) of kW, oxygen gas (gas pressure 1.0 kg / cm ² ) as assist gas, and processing speed 1.0
Processing was performed at mm / min, the overshoot amount was 300 μm, and the receding distance was 10 mm.

Further, based on FIG. 25, when the distance L that the laser beam travels when shifting from a right angle in the case of 60 degrees to an acute angle (or an obtuse angle to a right angle) is calculated, the cutting groove width is 0.56 mm. Therefore, r = 0.28 in the figure.
mm, and the distance L that the laser beam moves is 0.35
It was mm.

Example 9. FIG. 26 is a flow chart showing the operation sequence of the laser cutting method according to the thirteenth embodiment of the invention, and FIG. 27 is a characteristic diagram according to the ninth embodiment.
By changing the time required for the rise and fall of the laser beam moving speed, the machining path at the time of corner cutting became smooth as shown in FIG. 26, and melting damage did not occur. Although the corner portion is not a right angle, it is sufficient because, in practical use, the plate does not require so much accuracy.

However, when a thick plate and a thin plate were actually placed on the same table at the rise and fall of the changed laser beam moving speed and both plates were machined successively, it was extremely difficult to machine a hole having a small diameter. It became distorted and the roundness was remarkably reduced. In order to prevent this, the rise and fall times of the laser beam moving speed can be set separately for thick and thin plates, which eliminates melting damage at the corners of thick plates, and is also sufficient for machining small holes in thin plates. High accuracy was obtained.

Example 10. 28 is a flowchart showing the operation sequence of a laser cutting method according to an embodiment of the invention described in claim 14, FIG. 29 is a schematic diagram showing the laser cutting method of the tenth embodiment, and processing two patterns as shown. Processed along the route. In this case, the failure occurrence rate was 6% in FIG. 28 (a) and 6% in FIG. 28 (b). On the other hand, in the conventional method of cooling the edge, the defect occurrence rate is 74
%Met.

However, the number of samples was 50, a mild steel (SS400) plate thickness of 12 mm was used as a workpiece, the corner angle was 45 degrees, and the output of the CO ₂ laser was 1.4 kW continuous wave (CW) and assist gas. As oxygen gas (0.6k
g / cm ² ) and processing was carried out at a processing speed of 0.8 m / min. The length of the extended cutting groove 2a in FIGS. 29 (a) and 29 (b) is 5 mm.

Example 11. FIG. 30 is a schematic view showing a laser cutting method according to another embodiment of the invention as set forth in claim 14, and processing is performed by the processing path as shown in the drawing. This is a combination of the two molten metal escape paths of the tenth embodiment, and the reference numeral 12
The part indicated by is cut off. As a work piece, mild steel (SS400) having a plate thickness of 16 mm was cut at a corner angle of 45 degrees, and the number of samples was 50. The defect occurrence rate was 6%. It was also effective for a fairly thick work piece.

However, the processing conditions were that a continuous wave (CW) of 2.2 kW was used as the output of the CO ₂ laser, oxygen gas (gas pressure 0.5 kg / cm ² ) was used as the assist gas, and the processing speed was 0.8 m / min. Processed.

[0087]

As described above, according to the first aspect of the present invention, since the laser beam is moved backward and forward along the cutting groove that has been formed once, after cutting the normal front corner. Unlike the case where the corner rising is continuously cut, melting damage at the corner portion due to the delay of the cutting front surface does not occur. Further, by setting a sufficient distance for advancing again, the beam moving speed reaches the set value, and excessive heat input or insufficient heat input does not occur during cutting.

According to the second aspect of the invention, since the position where the retreat is first started is set to be before the corner by the distance required for the cutting speed to fall, the outer portion of the corner is also favorably formed. Can be cut with high precision.

According to the third aspect of the invention, the laser beam irradiation is temporarily stopped and the laser beam irradiation is continued, and according to the fourth aspect of the invention, the stop time is defined. However, a good cut surface can be obtained.

According to the fifth aspect of the present invention, the laser irradiation is stopped, the relative movement of the laser irradiation nozzle and the workpiece is stopped, and a cooling time is taken, so that the corner melts even if the workpiece is thick. Loss can be prevented.

According to the sixth aspect of the invention, the laser beam irradiation is temporarily interrupted in the process of retracting and cutting the corner, and the laser beam moving locus is cooled by gas or liquid. It is possible to stably cut the corner.

According to the invention described in claim 7, since the assist gas is blown around the cutting groove, forced cooling can be easily performed.

According to the invention described in claim 8, since the place where the assist gas is blown is designated, the efficiency of the cooling effect is improved.

According to the ninth aspect of the invention, since the blowing time of the assist gas is defined, the cooling time can be set efficiently and the processing time can be shortened.

According to the tenth aspect of the present invention, since the minimum necessary retreat amount is set according to the processing conditions and the shape of the workpiece, the processing time can be shortened.

According to the eleventh and twelfth aspects of the invention, since the acute angle is divided into the right angle and the obtuse angle for cutting, the acute corner can be accurately cut.

[0097]

According to the thirteenth aspect of the present invention, since a space having a width equal to or larger than the width of the cutting groove is provided on the extension of the cutting direction, the cutting can be performed accurately even at an acute-angled corner without melting damage.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus for performing a laser cutting method.

FIG. 2 is a flowchart showing a basic process performed by a CPU to carry out the laser cutting method according to the present invention.

FIG. 3 is a flowchart showing an auxiliary process performed by a CPU for carrying out the laser cutting method according to the present invention.

FIG. 4 is a flowchart showing a calculation process performed by a CPU for carrying out the laser cutting method according to the present invention.

FIG. 5 is a schematic diagram showing a laser cutting method according to an embodiment of the present invention.

FIG. 6 is a flowchart showing an operational sequence of an embodiment of the invention described in claim 1;

FIG. 7 is a schematic diagram showing a laser cutting method according to an embodiment of the present invention.

FIG. 8 is a flowchart showing an operational sequence of an embodiment of the invention described in claim 2;

FIG. 9 is a flow chart showing an operation sequence of an embodiment of the invention described in claim 3;

FIG. 10 is a flow chart showing an operation sequence of an embodiment of the invention described in claim 4;

FIG. 11 is a cutting characteristic diagram according to an embodiment of the invention as set forth in claim 4;

FIG. 12 is another cutting characteristic diagram according to an embodiment of the invention as set forth in claim 4;

FIG. 13 is a flowchart showing an operational sequence of an embodiment of the invention described in claims 5, 6 and 7.

FIG. 14 is a cutting characteristic diagram according to an embodiment of the invention described in claims 5, 6, and 7.

FIG. 15 is another cutting characteristic diagram according to an embodiment of the invention described in claims 5, 6, and 7. It

FIG. 16 is a perspective view showing a cooling gas jetting device according to an embodiment of the invention described in claims 5, 6, and 7.

FIG. 17 is a flow chart showing the operation sequence of an embodiment of the invention described in claims 8 and 9;

FIG. 18 is a cutting characteristic diagram according to an embodiment of the invention described in claims 8 and 9;

FIG. 19 is another cutting characteristic diagram according to an embodiment of the invention described in claims 8 and 9;

FIG. 20 is a cutting characteristic diagram according to an embodiment of the present invention.

FIG. 21 is an explanatory diagram of a cause of melting loss in acute-angle cutting.

FIG. 22 is a flowchart showing the operational sequence of an embodiment of the invention as set forth in claim 11;

FIG. 23 is a schematic diagram showing a laser cutting method according to an embodiment of the invention as set forth in claim 11;

FIG. 24 is a flowchart showing the operational sequence of an embodiment of the invention as set forth in claim 12;

FIG. 25 is a schematic view showing a laser cutting method according to an embodiment of the invention as set forth in claim 12;

FIG. 26 is a flowchart showing the operational sequence of an embodiment of the invention as set forth in claim 13;

FIG. 27 is a characteristic diagram according to an embodiment of the invention as set forth in claim 13.

FIG. 28 is a flow chart showing the operation sequence of an embodiment of the invention set forth in claim 14;

FIG. 29 is a schematic view showing a laser cutting method according to an embodiment of the invention as set forth in claim 14;

FIG. 30 is another schematic diagram showing the laser cutting method according to one embodiment of the invention as set forth in claim 14;

FIG. 31 is another schematic view showing the conventional laser cutting method.

[Explanation of symbols]

1 laser beam 2 Workpiece 2a Cutting groove (cutting locus) 6 Gas or liquid (cooling medium) A beam arrival position B preset position C position to change

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Kanaoka 5-14 Yada Minami 5-chome, Higashi-ku, Nagoya Sanryo Electric Co., Ltd. Nagoya Works (56) Reference Japanese Patent Laid-Open No. 2-30388 (JP, A) Kai 62-24885 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 26/38

Claims (13)

(57) [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, when the laser beam reaches a predetermined beam arrival position during cutting. A first step of retracting the laser beam along a cutting trajectory up to a preset position, and advancing the laser beam from the retracted position along the cutting trajectory to a position where the cutting advancing direction is changed. Second to change the cutting direction at the position
And the step of sequentially performing the steps of (1) and (2) by relatively moving the workpiece and the laser beam. 2. The laser cutting method according to claim 1, wherein the beam arrival position is set to a predetermined distance before a desired corner position depending on cutting conditions. 3. A third step of irradiating a beam by stopping the movement of the laser beam when the laser beam reaches the beam arrival position.
The laser cutting method described. 4. The laser cutting method according to claim 3, wherein the third step is set to 10 seconds or less. 5. The movement of the laser beam is stopped again after the movement and irradiation of the laser beam are interrupted for a preset time at a time point from the start of the first step to the end of the change of the cutting advancing direction. The laser cutting method according to claim 1, wherein the irradiation and the irradiation are restarted. 6. The laser beam irradiation is interrupted during the period from the start of the first step to the end of the change of the cutting proceeding direction, or a part thereof, along the laser beam moving in the interrupted period. The laser cutting method according to claim 1, wherein a cooling medium is blown onto the cutting processing locus. 7. The laser cutting method according to claim 6, wherein the cooling medium is an assist gas. 8. The laser cutting method according to claim 6, wherein a position at which the movement and irradiation of the laser beam are interrupted is set to the beam arrival position. 9. The laser cutting method according to claim 6, wherein the time for interrupting the movement and irradiation of the laser beam is set to 10 seconds or less depending on the material, plate thickness and cutting shape of the workpiece. . 10. The laser cutting method according to claim 1, wherein a receding distance from the beam reaching position is set according to a material, a plate thickness, and a cutting shape of the workpiece. 11. 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 cutting proceeding direction is changed to an obtuse angle and then to a right angle. The laser cutting method is characterized in that after changing the cutting advancing direction at a right angle, the cutting advancing direction is changed to an obtuse angle to cut an acute-angled corner portion. 12. A laser cutting method of irradiating a workpiece with a laser beam and cutting the workpiece with the energy of the laser beam, when the laser beam reaches a predetermined beam arrival position during cutting. A first step of retracting the laser beam along a cutting trajectory up to a preset position, and advancing the laser beam from the retracted position along the cutting trajectory to a position where the cutting advancing direction is changed. The second step of changing the cutting advancing direction at the position is sequentially executed by relatively moving the workpiece and the laser beam, and the cutting advancing direction is changed to an obtuse angle at the cutting advancing direction changing position. After changing the cutting direction, change the cutting direction to a right angle, or change the cutting direction to a right angle and then change the cutting direction to an obtuse angle to cut an acute-angled corner. The characteristic laser cutting method. 13. A laser cutting method for irradiating a workpiece with a laser beam and cutting the workpiece with the energy of the laser beam, wherein a broader width than a cutting groove width is provided on an extension line of a cutting groove in a traveling direction up to a corner. Or a space having a width larger than the width of the cutting groove is provided on an extension line in the direction opposite to the traveling direction of the cutting groove at the corner rising, and the corner portion is cut.