JP3159621B2 - Laser processing method and apparatus - 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 processing method and apparatus for preventing burn-through at the processing end of a workpiece.

[0002]

2. Description of the Related Art Conventionally, in laser processing, as means for preventing burn-through at the processing end portion of a workpiece, for example, as shown in FIG. After cutting the piercing line 8 from the through-hole (piercing) 7 to form a predetermined trajectory, ending the processing in front of the end portion, and causing burn-out due to heat concentration when the pierce is cut off. Measures have been taken to prevent it. Such an intentional uncut portion is used for the end joint 9.
This is a commonly used method.

In laser drilling disclosed in Japanese Patent Application Laid-Open No. 4-33788, the output of laser processing parameters, pulse duty, speed, and processing gas pressure are appropriately controlled in accordance with the cutting position. This is to process the workpiece with high quality.

[0004]

Since the conventional laser processing method is configured as described above, when the end joint 9 is provided, the operation of extracting the product from the workpiece as a secondary operation after the operation is performed. Necessary, especially for thick plates, the amount of end joints is large, making it difficult to extract them.
Further, since the joint portion has a convex shape, accuracy is deteriorated at the time of drilling a hole or the like, so that there is a problem that post-processing is required to improve the accuracy.

On the other hand, in the case of laser drilling shown in Japanese Patent Application Laid-Open No. 4-33788, at the final stage of the processing, the pierce line 8 which is a groove already formed is cut at the final stage of the processing as shown in FIG. Progresses, heat generated at the cutting front face is reflected by the piercing line 8, and the workpiece does not reach the proper processing conditions, but becomes abnormally high in temperature and causes processing defects, that is, burn-through. Was. In particular, this phenomenon tends to occur as the plate thickness increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides a laser processing method and a processing apparatus which do not require an end joint and prevent burn-out at an end portion.

[0007]

A laser processing method according to the present invention controls the positioning of a processing head in accordance with a processing trajectory from a processing start point to a processing end point, and irradiates a laser beam onto a workpiece to a predetermined position. In the laser processing method for cutting into a shape, the processing head irradiates the laser beam from the processing start point and once irradiates the laser beam when the laser beam reaches a processing stop point which is located a predetermined distance before the processing end point. Stopping, moving the processing head to the processing end point, restarting the laser beam irradiation, moving the processing head from the processing end point toward the processing stop point, and continuing the cutting processing. It is.

Further, the processing conditions before the laser beam irradiation is temporarily stopped and the processing conditions after the laser beam irradiation is restarted are different.

Further, the surface temperature of the workpiece is detected at a predetermined position near the processing end point including the processing end point, and a processing stop point for temporarily stopping the laser beam irradiation is determined based on the detected temperature.

Further, when cutting is performed from the processing end point to the temporary stop point of the laser beam, the workpiece surface temperature near the temporary stop point is detected, and when this detected temperature reaches a preset temperature, This ends the cutting process.

A laser processing apparatus according to the present invention controls the positioning of a processing head in accordance with a processing trajectory from a processing start point to a processing end point, and irradiates a laser beam onto a workpiece to cut into a predetermined shape. In the processing apparatus, temperature detection means for detecting the surface temperature of the workpiece near the processing end point, and processing stop for temporarily stopping laser beam irradiation before processing based on temperature data obtained by the temperature detection means. Determining means for determining at least one of the position of the point and the processing conditions after restarting the irradiation of the laser beam.

[0012]

According to the laser processing method of the present invention, in a laser processing method for controlling the positioning of a processing head in accordance with a processing locus from a processing start point to a processing end point and irradiating a laser beam for cutting, a predetermined distance before the processing end point. When the laser beam reaches the processing stop point, the laser beam irradiation is stopped once, the processing head is moved to the processing end point, then the laser beam irradiation is restarted, and the processing head is moved from the processing end point to the processing stop point. By continuing the cutting, the temperature is prevented from abnormally rising near the processing end point due to heat reflection from the piercing line.

Further, by making the processing conditions before the laser beam irradiation is once stopped and the processing conditions after the laser beam irradiation is resumed different, the temperature near the processing end point is reduced by heat reflection from the piercing line. Is more effectively prevented from rising abnormally.

Further, the surface temperature of the workpiece is detected at a predetermined position near the processing end point including the processing end point, and the processing stop point for temporarily stopping the laser beam irradiation is appropriately determined based on the detected temperature.

Further, when cutting the laser beam from the processing end point to the temporary stop point of the laser beam, the surface temperature of the workpiece near the temporary stop point is detected, and when this detected temperature reaches a preset temperature, , To finish the cutting process,
Prevents overheating of processing points.

The laser processing apparatus according to the present invention controls the positioning of a processing head in accordance with a processing locus from a processing start point to a processing end point, and irradiates a laser beam onto a workpiece to cut into a predetermined shape. A temperature detecting means for detecting a workpiece surface temperature near a processing end point; and a processing stop point for temporarily stopping laser beam irradiation before processing based on temperature data obtained by the temperature detecting means. Determining means for determining at least one of the position and the processing condition after the restart of the laser beam irradiation, so that appropriate processing can be easily realized in the vicinity of the processing end point.

[0017]

【Example】

Embodiment 1 FIG. FIG. 1 shows a processing path at the time of processing a small hole in the laser processing method according to the first embodiment of the present invention. In the step S1 in the figure, piercing is performed, a through hole (piercing) 7 is formed, processing is performed on the piercing line 8, and further cutting is performed on a predetermined processing locus. The step S2 is a state in which the machining is temporarily stopped at the machining stop point 10 before the machining end point. Further S3
Is a state in which the processing head, which is a beam irradiator, has been moved in a non-irradiated state at the processing end point or the cut groove above the processing end point extension. The step S4 is a state in which the cutting is resumed from the moved point to the machining stop point 10 which is a temporary stop position.

FIG. 2 shows a machining path in the case of simply cutting off. First, in step S11, the machining head 1 is moving along a machining locus from the start point to the end point and is cutting. The process of S12 is a state where the machining is temporarily stopped just before the machining end point. Further, the step of S13 is a state in which the processing head 1 has been moved in a non-irradiated state on the space (outside the workpiece) on the extension of the processing end point or on the processing end point. S14 is a state in which the irradiation is restarted from the moved point and the cutting is temporarily performed to the stop position.

FIG. 3 shows the definition of the burn-through amount at the end of the processing of the workpiece. Hereinafter, the burn-through amount is measured according to this figure. FIG. 4 shows the result of comparing the burn-through amount at the terminal end when cutting along the processing path at the time of small hole processing by the laser processing method according to the first embodiment of the present invention and when cutting along the conventional processing path. It is clear that the end burn-through of the laser processing method according to the present invention is reduced as compared with the conventional method. In this case, since the relationship (distance) between the processing end point and the temporary stop position has an appropriate value related to the material and the thickness of the workpiece, the conditions according to the various materials and the thickness are set in advance by NC. Registered in the device or automatic programming device and can be set automatically.

Embodiment 2 FIG. FIG. 5 shows a closed-curve processing path of the laser processing method according to the second embodiment of the present invention. The processing path is basically the same as that of the first embodiment. Most of the processing path is cut by CW (continuous wave). FIG. 6 shows the variation due to the amount of burn-through at the end portion and the plate thickness when the mild steel material is processed with different end treatment methods for the shape of FIG. A. When cutting to the end under cutting conditions in the conventional laser processing method,
b. Is about 3 mm to the processing end point, for example, 30 Hz
Switching to low frequency pulse conditions of the order of c. Is b.
This is a case where the same conditions as in the above were cut along the path in the laser processing method of the present invention. a. , B. C. Is about 1/4 to 1/5.

The switching of the processing conditions at the end portion has substantially the same effect even when the processing gas pressure is lowered or the type of the assist gas is changed. The termination processing by CW is adopted only when the processing time can be shortened rather than the burn-through quality because the speed can be set high.

Embodiment 3 FIG. A shape (900 × 300 mm) having many holes as shown in FIG. A case where the stop position is once set to a point 3 mm from the processing end point in advance, b. The surface temperature of the workpiece is detected at a predetermined position near the processing end point including the processing end point by the temperature detecting means 2 as shown in FIG. 8, and based on the detected temperature, the processing stop point for temporarily stopping the irradiation of the laser beam is determined. FIG. 9 shows an example in which the machining time is compared with the case where the optimum stop position is determined.

For example, the work material at this time, mild steel SS40
0, plate thickness 16 mm, output 2200 W, CW, processing speed 0.7 m / min as processing conditions for high-speed cutting part, output 600 W, frequency 20 Hz, duty 20%, processing speed 0.03 m / min as processing conditions for end part When the stop position is previously set to a point 3 mm from the processing end point, the optimum stop position for temporarily stopping the laser beam irradiation obtained based on the detected temperature is 1 to 1 from the processing end point. The point (b) is 2 mm, so that the processing time is a. 9 minutes and 30 seconds, b. In this case, it was 7 minutes.
In addition, since there is a difference in heat accumulation of the workpiece depending on the plate thickness, the optimum stop position is different, and the plate thickness is 17 mm, 1 to 2.2 mm,
It becomes 1.5 to 2.8 mm when the plate thickness is 19 mm. The reason why the processing time becomes longer for a thick plate even when the thickness is fixed at 3 mm is that the cutting speed under high-speed conditions (continuous wave) is different (the slower the thicker the plate).

Embodiment 4 FIG. Fourth Embodiment In the fourth embodiment of the present invention, when the machining is once stopped, the workpiece is moved to the machining end point, the cutting is again performed toward the machining stop point, and the cutting distance toward the machining stop point when the machining is completed is optimized. Things. In the case of this cutting, although the scale is smaller than that of the conventional burn-through at the end of the laser processing path, burn-through occurs at the last part of the cut. In order to prevent this burn-through, it is preferable to stop the cutting immediately before burn-through occurs in view of the short cutting distance and efficiency. The remaining distance of the cutting is naturally cut off by the reaction between the hot workpiece and the assist gas.

In the fourth embodiment, in order to stably achieve the above, when cutting is again performed toward the machining stop point, the temperature near the machining stop point is measured in the same manner as in FIG. The cutting is terminated immediately before the occurrence of burn through based on the temperature measurement data near the processing stop point. FIG. 10 shows the relationship between the burn-through amount and the plate thickness when the processing end point is optimized by temperature measurement and when the processing end point is always 0.5 mm from the stop point. By optimizing the processing end point by temperature measurement, variation in the burn-through amount due to the plate thickness is reduced, and the burn-through amount is also reduced.

Embodiment 5 FIG. FIG. 11 shows Embodiment 5 of the present invention.
1 is a configuration diagram showing a laser processing apparatus according to the present invention. The laser processing apparatus irradiates the surface of the workpiece 3 with the laser beam oscillated from the laser oscillator 4 by the processing head 1 and cuts the laser beam. The cutting direction and speed are controlled by the servo motor 5
It is determined by moving the table equipped with. In order to measure the surface temperature of the workpiece 3 in the vicinity of the laser beam irradiated to such a laser processing apparatus, for example, an infrared sensor 2a and a temperature measuring unit that perform 360-degree omnidirectional measurement in accordance with the servo motor 5 for moving the table 2b is provided.

That is, the workpiece 3 always near the processing front surface
The surface temperature of the workpiece 3 is measured just before the processing end point by the temperature detecting means 2 installed to measure the surface temperature of the workpiece 3, and the surface temperature of the workpiece 3 reaches a preset temperature due to a heat storage phenomenon. When this is detected, the beam irradiation is stopped. In this state, the workpiece is moved to the machining end point or an already cut groove or space on the extension of the machining end point. Therefore, based on the measured temperature results, the optimum processing condition for cutting the material having the surface temperature is selected from the processing condition memory in the NC device 6. Next, processing is started under the selected processing conditions up to the beam irradiation stop point. Also at this time, the surface temperature of the workpiece 3 near the processing front surface is always measured, and the processing is terminated when the surface temperature of the work reaches a temperature at which burnout occurs under any processing conditions due to heat storage. Also, as in Example 4,
In order to determine the processing end point, the temperature of the workpiece 3 is also measured by the temperature detecting means 2 at the time of reprocessing, and the measured temperature data of the workpiece 3 is sent to the NC device 6 to cause the burn-off temperature under the selected condition. To determine the processing end point.

[0028]

As described above, according to the present invention, when the laser beam reaches the processing stop point which is a position before the processing end point by a predetermined distance, the laser beam irradiation is temporarily stopped, and the processing head is moved to the processing end point. After that, the laser beam irradiation was restarted, and the processing head was moved from the processing end point to the processing stop point to continue cutting processing, so the temperature of the processing point near the processing end point was abnormal due to heat reflection from the piercing line This has the effect of preventing the occurrence of processing defects due to rising and burn-through.

Further, since the processing conditions before the laser beam irradiation is temporarily stopped and the processing conditions after the laser beam irradiation is restarted are different, the processing point near the end point due to heat reflection from the piercing line is changed. More effectively prevents abnormal temperature rise and machining failure due to burn-through.

Further, when the processing head whose position is controlled approaches the processing end point while irradiating a laser beam from the processing start point to the processing end point, the surface temperature of the workpiece near the processing end point is detected. However, since the stop position at which the irradiation of the laser beam is temporarily stopped is determined based on the detected temperature, there is an effect that the stop point is appropriately determined once and the burn-through amount is minimized.

Further, when cutting the laser beam from the processing end point to a temporary stop point of the laser beam, the surface temperature of the workpiece near the temporary stop point is detected, and when the detected temperature reaches a preset temperature. Since the cutting process is terminated at the step (1), overheating of the processing point is prevented, and burn-out due to overheating is prevented.

A laser processing apparatus according to the present invention comprises a temperature detecting means for detecting a surface temperature of a workpiece near a processing end point and a laser beam once before processing based on temperature data obtained by the temperature detecting means. Determining means for determining at least one of the position of the processing stop point for stopping the irradiation of the laser beam and the processing conditions after the laser beam irradiation is resumed, so that appropriate processing can be realized in the vicinity of the processing end point. This is effective in preventing burn-through and improving product quality.

[Brief description of the drawings]

FIG. 1 is a diagram showing a processing path at the time of processing a small hole in a laser processing method according to a first embodiment of the present invention.

FIG. 2 is a view showing a processing path at the time of cutting off in the laser processing method according to the first embodiment of the present invention.

FIG. 3 is a diagram defining a burn-through amount.

FIG. 4 is a diagram comparing the burn-through amount between the cutting method according to the first embodiment of the present invention and a conventional ordinary cutting method.

FIG. 5 is a view showing a processing path of a laser processing method according to a second embodiment of the present invention.

FIG. 6 is a diagram comparing the amount of burn-through in the case of changing the processing conditions at the end between the conventional laser processing method, the conventional laser processing method, and the laser processing method according to the second embodiment of the present invention.

FIG. 7 is a diagram showing a processing shape used in a laser processing method according to a third embodiment of the present invention.

FIG. 8 is a diagram showing a state of temperature detection on a surface of a workpiece in a laser processing method according to a third embodiment of the present invention.

FIG. 9 is a diagram comparing processing times in a case where a terminal distance is fixed and a case of a laser processing method according to a third embodiment of the present invention.

FIG. 10 is a diagram comparing the burn-through amount between the case where the processing end point is fixed and the case of the laser processing method according to the fourth embodiment of the present invention.

FIG. 11 is a schematic configuration diagram showing a laser processing apparatus according to Embodiment 5 of the present invention.

FIG. 12 is an explanatory diagram showing a piercing line and a thermal effect at the time of cutting.

FIG. 13 is an explanatory diagram showing a processing path of a conventional laser processing method.

[Explanation of symbols]

1 processing head, 2 temperature detection means, 3 processed products, 4
Laser oscillator 5 Servo motor, 6 NC device, 7 through hole (piercing), 8 piercing line, 9 end joint, 10
Stop point

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-214356 (JP, A) JP-A-6-344162 (JP, A) JP-A-6-269967 (JP, A) JP-A 5- 309484 (JP, A) Japanese Utility Model 62-105777 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 26/00 B23K 26/02

Claims (5)

(57) [Claims] 1. A laser processing method for positioning a processing head in accordance with a processing locus from a processing start point to a processing end point and irradiating a laser beam onto a workpiece to cut the workpiece into a predetermined shape. Irradiates the laser beam from the processing start point, temporarily stops the laser beam irradiation when reaching a processing stop point which is a position before the processing end point by a predetermined distance, and moves the processing head to the processing end point A laser processing method, wherein the laser beam irradiation is restarted, and the processing head is moved from the processing end point to the processing stop point to continue the cutting processing. 2. The laser processing method according to claim 1, wherein a processing condition before the laser beam irradiation is temporarily stopped and a processing condition after the laser beam irradiation is restarted are different. 3. The method according to claim 1, wherein a surface temperature of the workpiece is detected at a predetermined position near the processing end point including the processing end point, and a processing stop point for temporarily stopping the laser beam irradiation is determined based on the detected temperature. The laser processing method according to claim 1, wherein the laser processing method is performed. 4. When cutting from a processing end point to a temporary stop point of a laser beam, a workpiece surface temperature near the temporary stop point is detected, and when the detected temperature reaches a preset temperature, 4. The laser processing method according to claim 1, wherein the cutting process is terminated. 5. A laser processing apparatus for controlling the positioning of a processing head in accordance with a processing locus from a processing start point to a processing end point and irradiating a laser beam onto a workpiece to cut the workpiece into a predetermined shape. Temperature detection means for detecting the surface temperature of a nearby workpiece, and determination based on temperature data obtained by the temperature detection means
Once stop the irradiation of the laser beam at once position and the machining stop point of the machining stop point for stopping the irradiation of the laser beam
Stop and move the processing head to the processing end point,
When cutting from the processing end point to the above processing stop point
Determining means for determining at least one of the processing conditions.