JPH05285683A - Laser beam machine and its monitor method - Google Patents

Abstract

PURPOSE:To stabilize processing by preventing the generation a processing defect by the thermal influence, etc., on optical parts. CONSTITUTION:Beam diameter measuring means 7, 8 which measure the diameter D of a laser beam L in a condenser means 4A in at least the position B where processing ends are provided. A change in lapse of time in the diameter of the incident beam on the condenser means is actually measured and is compared with a range for managing the beam diameter corresponding to the processing defect state. Abnormality is detected and the exchanging or cleaning of the optical parts 2 is urged. As a result, the recognition of the time for exchanging the optical parts, etc., is enabled and the management is facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention makes it possible to detect fluctuations in beam diameter during processing due to thermal effects of laser beam output on optical components, etc., to prevent processing defects from occurring and to realize stable processing. And a monitoring method thereof.

[0002]

2. Description of the Related Art Conventionally, a laser processing apparatus for irradiating a work with a laser beam to perform heat treatment, welding, cutting and the like has been well known. FIG. 4 is a configuration diagram showing an optical path of a conventional laser processing apparatus described in, for example, Japanese Patent Laid-Open No. 63-60092.

In the figure, 1 is a laser oscillator for emitting a laser beam L, 2 is an output window of the laser oscillator 1 which serves as an emission window of the laser beam L, 3 is a mirror for switching the direction of the laser beam L, and 4 is a mirror 3. A condenser lens 5 for converging the reflected laser beam L is a work which is irradiated with a spot S of the laser beam L via the condenser lens 4 and is subjected to desired processing.

Between the output window 2 and the condenser lens 4,
A correction lens (not shown) for correcting the beam diameter D or the like may be inserted as an optical component. Further, the mirror 3 and the condenser lens 4 can be replaced with a condenser mirror having both functions.

Next, the operation of the conventional laser processing apparatus shown in FIG. 4 will be described. The laser beam L emitted from the output window 2 of the laser oscillator 1 is reflected by the mirror 3 and converged by the condenser lens 4 to become a spot, which is applied to the work 5. After that, for example, by sweeping the mirror 3 and the condenser lens 4 along the surface of the work 5, the work 5 is subjected to desired processing.

At this time, the use of the output of the laser beam L, the focal length of the condenser lens 4, etc. is preset according to the processing conditions. However, when processing is performed for a long time, the transparent optical component including the output window 2 has heat, and a change in the refractive index distribution due to a local temperature rise and a shape change due to thermal stress occur. For example, when the output window 2 normally made of a transparent plate is transformed into a convex lens by the thermal lens action, the laser beam L which has passed through the output window 2 and is once converged is diverged by the time it reaches the condenser lens 4. The diameter D diffuses, and the mode and output of the laser beam L change from the normal state.

This phenomenon becomes more remarkable as the absorptance of the optical components such as the output window 2 increases and the output of the laser beam L increases. Therefore, when the output window 2 becomes dirty due to long-term use, or when high-power laser processing of about 10 KW is performed, even if normal processing can be performed immediately after the start of processing,
Machining becomes defective from the middle. In order to prevent this, it is conceivable to change the processing conditions, for example, by reducing the laser output, but it takes a long processing time.

Particularly, in recent years, not only a low-power laser beam of about 5 KW but also a high-power laser beam of about 10 KW tends to be frequently used. The heat effect of is no longer negligible. Therefore, the optical component including the output window 2 is apt to undergo a thermal change due to deterioration over time, and the already adjusted machining specification of the workpiece 5 cannot be satisfied.

Further, even if a processing defect may occur, since the quantitative relationship between the beam diameter D of the laser beam L and the processing state is not known, after the processing defect actually occurs, The transparent optical component including the output window 2 is replaced or cleaned, and the work 5 is reprocessed.

[0010]

As described above, the conventional laser processing apparatus and the monitoring method therefor do not detect the beam diameter fluctuation due to the thermal change of the optical component including the output window 2, so that the laser beam is processed during processing. When the beam diameter D of L fluctuates and the processing on the work 5 becomes unstable, a processing defect actually occurs, and there is a problem that desired processing cannot be performed.

The present invention has been made to solve the above-mentioned problems, and makes it possible to detect a beam diameter variation during processing due to a thermal influence of a laser beam output on an optical component or the like, thereby causing a processing defect. It is an object of the present invention to obtain a laser processing apparatus and a monitoring method thereof, which are prevented in advance to realize stable processing.

[0012]

The laser processing apparatus according to the present invention is provided with beam diameter measuring means for measuring the diameter of the laser beam at the focusing means at least at the processing end position.

Further, in the method for monitoring a laser processing apparatus according to the present invention, the diameter of the laser beam at the focusing means is measured at least at the processing end position, and an abnormality is detected when the beam diameter is out of the control range. It was done.

[0014]

According to the present invention, the time-dependent change of the beam diameter incident on the focusing means is measured and compared with the beam diameter control value corresponding to the processing defect state, and when the beam diameter is out of the control range, it is abnormal. Is detected to prompt replacement or cleaning of the optical component, and prevent the occurrence of processing defects.

[0015]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a laser processing apparatus applied to an embodiment of the present invention, and reference numerals 1, 2 and 5 are the same as those described above. Reference numeral 4a is a condenser mirror having the functions of the mirror 3 and the condenser lens 4 described above, and 5a and 5b are works made of two plate materials. Here, the works 5a and 5b are butted against each other, the condenser mirror 4A is moved to the position of the broken line, and the line 5c
It shows the case of welding in the direction of arrow C from point A (start point) to point B (end point) via.

Reference numerals 7 and 8 are van pattern measuring plates made of an acrylic plate or the like, which constitute a beam diameter measuring means for measuring the diameter D of the laser beam L at the converging mirror 4A at the processing end position, that is, point B. ..

The bun pattern measuring plate 7 is arranged at the solid line position during the processing, but is moved to the broken line position by the manual operation or the driving means immediately after the processing, so that it is located between the output window 2 and the condenser mirror 4A. The laser beam L is emitted by being inserted into the optical path. Further, the bun pattern measuring plate 8 is arranged at an extension position from the condenser mirror 4A to the processing end point B, and the laser beam L passing through the point B is irradiated immediately after the processing end. Therefore, the van pattern measurement plates 7 and 8 are adapted to measure the beam diameter D at the condenser mirror 4A at the position corresponding to the point B.

FIG. 2 shows the laser beam L with respect to the oscillation time t.
FIG. 5 is a characteristic diagram showing the relationship between the beam diameter D and the back bead width W of welding. Usually, the beam diameter D must be narrowed down to about 55 mm or less in order to secure a desired processing capability. Further, the welding width at the line 5c viewed from the back of the work 5 after the welding process, that is, the back bead width W corresponds to the degree of completion of welding. A value of about 2 mm or more is required.

In FIG. 2, a curve Da shows the characteristics when the output window 2 is new (absorption rate α is about 0.2%) and a high output oscillation of 10 KW is generated, and a curve Db shows the absorption rate α of the output window 2. Shows the characteristics when high-power oscillation is performed when is increased to about 0.51% due to surface contamination due to long-term use. Also, Wa and Wb are
Plate thickness 3.2m by laser beam L of each beam diameter Da and Db
It is the back bead width characteristic when welding the workpiece 5 of m,
t = 0 corresponds to the welding start point A, and t = 60 seconds corresponds to the welding end point B.

FIG. 3 is an explanatory view showing the thermal lens action.
(a) is the optical path of the laser beam L when the output window 2 is in a normal state,
(b) shows the optical path of the laser beam L when the output window 2 is deformed by the thermal lens action, and when the thermal lens action of the output window 2 occurs as shown in (b), the beam diameter D'is in the normal state. It is shown that the beam diameter becomes larger than the beam diameter D.

Next, referring to FIGS. 2 and 3, FIG.
The operation of the embodiment of the present invention shown in FIG.
First, when the work 5 is processed, the condenser mirror 4A moves, the laser beam L is scanned from the welding start point A to the welding end point B in the direction of arrow C, and the works 5a and 5b are welded via the line 5c. ..

At this time, the laser beam L is irradiated on the bun pattern measuring plate 8 immediately after passing the welding end point B, and an irradiation mark is left on the bun pattern measuring plate 8. Therefore, by measuring this irradiation trace, the beam diameter D at the converging mirror 4A at the end of welding can be known. After the welding is completed, the van pattern measuring plate 7 is moved to the position of the broken line so that the condenser mirror after an arbitrary time has passed.
The beam diameter D at 4A can be known.

Incidentally, the relationship between the beam diameter D and the back bead width W is assumed to be measured in advance as shown in FIG. 2, and the beam diameter D is controlled when the processing failure, that is, the back bead width W becomes 1 mm or less. The value is set to 55 mm, for example. Therefore, if the beam diameter D becomes equal to or larger than the control value (55 mm), processing becomes defective. Therefore, when the beam diameter D approaches the control value, the output window 2 must be replaced or cleaned immediately.

In general, the beam diameter D initialized as shown in FIG. 3A varies as shown in FIG. 3B due to the thermal lens action of the output window 2. For example, when the thermal lens action becomes remarkable due to deterioration with time or the like, the focal length of the output window 2 as a convex lens becomes short, and D '(> D) accompanies divergence of the laser beam L.
To enlarge. When the laser beam L is focused in front of the condenser mirror 4A in this way, the processing performance is significantly reduced. That is, the laser beam L having a beam diameter characteristic of Db (FIG. 2)
When the welding is performed in, the back bead width W fluctuates as shown by Wb (broken line), the welding capacity decreases as the beam diameter D increases, and the back bead width W becomes 1 mm or less and welding failure occurs. Resulting in.

Since the output window 2 generally changes slowly with time, the beam diameter measurement by the van pattern measurement plates 7 and 8 may be periodically performed. As a result, it is possible to know the cleaning and replacement times, and it becomes easy to manage the optical components. When an abnormality in the beam diameter D is detected, the output window 2
By exchanging or cleaning, the processing defects are prevented in advance, the welding of the back bead width W of a required value or more is reliably performed, and the processing is stabilized.

Example 2. In the above embodiment, the van pattern measuring plates 7 and 8 were arranged to measure the beam diameter D.
The measurement may be performed with only one of the bun pattern measuring plates 7 or 8. In this case, since the thermal lens action of the output window 2 increases as the oscillation time elapses, it is necessary to measure the beam diameter D at the focusing mirror 4A at least at the welding end point B.

Example 3. Further, the beam diameter D is measured immediately after the actual processing is performed, but by monitoring the beam diameter D immediately before performing the processing, it is possible to more reliably prevent the occurrence of processing defects. In this case, the laser beam L
Is oscillated to perform a pseudo scan from the processing start point A to the processing end point B, and the beam diameter D at the end point is measured. Therefore, a beam shutter (not shown) is inserted so that the work 5 is not irradiated with the laser beam L,
It is necessary to block the optical path to the work 5 during monitoring.

Example 4. Further, the case where the laser processing is welding has been described as an example, but it goes without saying that the same effects can be obtained by being similarly applied to other processing such as heat treatment and cutting. In this case, the control value for determining the abnormality of the beam diameter D is set to a value that allows normal processing, based on a separate actual measurement.

Example 5. Moreover, as shown in FIG. 3B, the case where the processing defect occurs due to the divergence of the beam diameter D is shown.
Even when the distance from the laser oscillator 1 to the condensing mirror 4A is shorter than the focal length and the beam diameter D is in a condensing state, the spot on the work 5 is incomplete, and a processing defect similarly occurs. .. Therefore, as the control value of the beam diameter D, it is necessary to set not only the upper limit value but also the lower limit value.

Example 6. Further, the condensing mirror 4A is used as the condensing means for forming the spot on the work 5, but the condensing lens 4 whose function is separated from the reflecting mirror 3 may be used as in FIG.

[0031]

As described above, according to the present invention, the beam diameter measuring means for measuring the diameter of the laser beam at the focusing means at least at the processing end position is provided, and the beam diameter incident on the focusing means changes with time. By measuring the change and comparing it with the beam diameter control value corresponding to the processing defect state, when the beam diameter is out of the control range, it detects an abnormality and prompts replacement or cleaning of the optical component. There is an effect that it is possible to obtain a laser processing apparatus that realizes the stabilization of processing by preventing the occurrence of processing defects due to the heat influence on the processing.

Further, according to the present invention, the diameter of the laser beam at the focusing means is measured at least at the processing end position, and when the beam diameter is out of the control range, an abnormality is detected, and the optical component is replaced or cleaned. Therefore, there is an effect that it is possible to obtain a monitoring method for a laser processing apparatus, in which the occurrence of processing defects due to thermal influence on optical components is prevented and the processing is stabilized.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a laser processing apparatus according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between an oscillation time, a beam diameter, and a back bead width according to the monitoring method of the laser processing apparatus of the present invention.

FIG. 3 is an explanatory diagram showing a thermal lens action of a general laser processing apparatus.

FIG. 4 is a configuration diagram showing an optical path of a conventional laser processing apparatus.

[Explanation of symbols]

 1 Laser Oscillator 2 Output Window 4A Condensing Mirror 5 Workpiece 7, 8 Van Pattern Measuring Plate (Beam Diameter Measuring Means) B Processing End Point D Beam Diameter L Laser Beam

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Tanaka 1-1 Tobahata-cho, Tobata-ku, Kitakyushu City Nippon Steel Co., Ltd. Yawata Works (72) Inventor Tsutomu Kitagawa 8-1-1 Tsukaguchihonmachi, Amagasaki Issue Mitsubishi Electric Co., Ltd. Itami Works (72) Inventor Katsumi Morikawa 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Co., Ltd. Itami Works

Claims (2)

[Claims] 1. A laser processing apparatus comprising: a laser oscillator having an output window for emitting a laser beam; and a condensing unit for converging the laser beam into a spot and irradiating the work with at least processing. A laser beam machining apparatus comprising beam diameter measuring means for measuring the diameter of the laser beam in the focusing means at a position. 2. A method of monitoring a laser processing apparatus, wherein a laser beam of a processing oscillation output is emitted from an output window of a laser oscillator, and a laser beam is focused on a spot by a focusing means to irradiate a work, at least a processing end position. 2. A method for monitoring a laser processing apparatus, comprising: measuring the diameter of the laser beam in the condensing means, and detecting an abnormality when the beam diameter is out of a control range.