JPH10296465A - Method for monitoring laser welding and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monitoring method/device to solve the problem that in the case of welding a butting part of sheet metal work for example by YAG laser welding robot or the like, even the gap or the melt down is bigger than the standard size, the welding is continued as it is without any regard to possible defective welding following the prescribed working program. SOLUTION: In the nozzle 4 of laser beam working head 2, an optical sensor 11 such as photodiode or infrared sensor or the like is arranged to detect the reflected light from the surface of the work W. Then, the detected light is introduced to the control unit, generation of defective welding is foreseen from the prescribed threshold, and suspension of working by the apparatus, or reoperation of welding or so by enlargement of spot diameter of converted beam and supply of filler metal and the like is commanded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a laser welding machine,
More particularly, the present invention relates to a method and an apparatus for monitoring laser welding of a sheet metal work.

[0002]

2. Description of the Related Art FIG. 2 shows an example of an overall perspective view of a pair of sheet metal workpieces which are opposed to each other and are opposed to each other during welding by a laser welding robot.

[0003] 1 is a YAG laser welding robot, 2 is a processing head thereof, and a laser (light) beam is a YA (not shown).
Processing head 2 from G laser oscillator through optical fiber 3
The nozzle 4 is guided to the nozzle 4 at the tip end of the work, and performs butt welding of the welding line 5 of the sheet metal work W in accordance with a predetermined processing program.

When a pair of sheet metal workpiece W edges are brought into contact with each other, a certain amount of clearance is generated. However, when these are subjected to laser welding, a laser beam from the nozzle 4 is condensed by a condenser lens (described later). The focused spot diameter on the work W surface is about 0.8 mm, and when the clearance or burn-through during welding is larger than this, the laser beam penetrates the clearance and normal welding cannot be performed, Poor welding results.

FIGS. 3 (a) and 3 (b) are enlarged cross-sectional schematic views of a main portion of the welding process. (A) is a schematic explanatory view of a normal (good) processing state in which an appropriate fused portion 5a is provided, and (b) is a schematic explanatory view of a processing failure state when the clearance C is excessive.

FIG. 3A shows a normal processing state in which the laser beam 6 is focused on the welding line 5 by the condenser lens 7 inside the processing head 2.

FIG. 3B shows a clearance C between the abutting works W.
Is too large, and the laser beam 6 passes through it, indicating that normal welding cannot be performed, and the laser beam 6 proceeds according to a predetermined processing program with poor welding.

[0008] Due to the above-mentioned progress, it takes a lot of time and cost to repair a defective welding portion after the completion of the working operation, which hinders the improvement of the working throughput.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and immediately detects the occurrence of this type of welding failure during laser beam welding of a workpiece W. In order to prevent this kind of failure from continuing, this process should be temporarily interrupted immediately, skipped to the next process, or transferred to reworking means to prevent this. It is an object of the present invention to provide a monitoring method and an apparatus for enabling a transition from one to another.

[0010]

Therefore, in the present invention, the object is achieved by providing a method and apparatus for monitoring a laser welding process according to any one of the following items (1) to (3). Is what you do.

(1) In a laser welding machine for performing butt welding of a sheet metal work, a laser beam reflected light on the work surface, a visible light on the work surface, an amount of welding spatter, a welding fume, Sensor means for detecting at least one of the amount and the assist gas concentration, and comparing the output with a predetermined threshold value set in advance, respectively, to determine the occurrence of welding failure. A method and apparatus for monitoring a laser welding process, further comprising a control unit for shifting to a unit for preventing the laser welding process.

(2) The transition means for preventing the occurrence of the welding defect includes stopping the current welding processing described below, skipping to the next processing operation, reworking by changing a laser beam focusing, and supplying a welding filler element. The method for monitoring a laser welding process according to the above (1), which is any one of the following reworking.

(3) A monitoring apparatus for laser beam welding, wherein the monitoring method for laser beam welding according to any one of the above (1) and (2) is adopted.

[0014]

According to the method / apparatus of the present invention as described above, it is possible to quickly detect the occurrence of welding defects due to an excessively large gap in a laser beam welded portion, etc., and to take appropriate measures to reduce post-cost / time, etc. You can choose to migrate.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described in detail based on a plurality of embodiments.

[0016]

【Example】

(Structure) FIG. 1 is a sectional view showing the structure of a working head 2 of a YAG laser welding machine according to an embodiment of the present invention. Reference numeral 3 denotes an optical fiber for guiding a laser (light) beam from a YAG laser oscillator (not shown), and reference numeral 3a denotes an emission port to the processing head 2. The laser beam from the emission port 3a is diffused and reaches a collimator lens (collimator) 8, where it is distributed into a uniform parallel beam. The laser beam passes through the nozzle 4 by the condenser lens 7 shown in FIG. Is focused to a spot diameter of about 0.8 mm on the surface of the welding line 5 so that concentrated energy can be irradiated onto the welding line 5. In the figure, reference numeral 9 denotes a protection window.

A feature of the embodiment of the present invention is that a photodiode or an infrared sensor for detecting reflected light reflected from the surface of the work W is provided outside the laser beam focusing line cone area inside the nozzle portion 4. And the detected reflected light is input to a control device (not shown) via the cable 11.

(Operation / Operation) Next, the operation and operation will be described: the contact clearance C between the two works W of the welding line 5 which are brought into contact with each other for welding (see FIG. 3B).
Is set smaller than the focused beam spot diameter (≒ 0.8 mm), and when the laser beam is irradiated from the nozzle 4 onto the surface of the work W and normal welding is performed, There is an absorbed beam and a reflected beam, and the sensor 10 monitors the latter reflected beam.

If the clearance C is too large, or if an abnormality such as the material of the work W in the processed portion melts off, the laser beam passes through the clearance C, and the surface of the work W is not irradiated with the laser beam. Therefore, since no reflected light is generated, the reflected light is detected by the sensor 10, and the control unit (not shown) can determine the degree of normality / abnormality based on each predetermined threshold value.

With the above determinations, the control unit can instruct any of the following processes.

1) When it is determined that the clearance C has become excessively large, the processing of the defective product is stopped so as to be interrupted. 2) Or, the processing is skipped to the next product. 3) Or, if the clearance C is excessively large. Returning to the time point of the judgment (the processing location), the laser beam by the condenser lens 7 is slightly defocused (blurred out of focus), and the re-processing is attempted by increasing the diameter of the focused spot. 4) or 3) Returning to the time point of judgment, and trying reworking while supplying an appropriate filler element and the like.

(Other Embodiments) In the above embodiment, the laser beam reflected on the surface of the workpiece is detected as the welding monitoring method. However, the present invention is not limited to this. The following amounts may be detected and determined using appropriate sensor means.

1) the amount of light in the visible region during welding, 2) the amount of scattered spatter during welding, 3) the amount of fume during welding, 4) the assist gas on the upper surface of the work W that is converted by the amount of the gap 8 Concentration, etc.

[0024]

As described above, according to the present invention,
Since the possibility of occurrence of welding defects during laser welding can be detected at an early stage, it is possible to shift to an appropriate countermeasure, thereby contributing to a reduction in overall cost and an improvement in throughput.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a processing head of a YAG laser welding machine according to an embodiment.

FIG. 2 is an overall perspective view during processing by a YAG laser welding robot.

FIG. 3 is an explanatory view of a good processing state (a) and a poor processing state (b) of a main part of the welding processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 YAG laser welding robot 2 Processing head 3 Optical fiber 3a Optical fiber emission port 4 Nozzle 5 Welding line 5a Fused part 6 Laser beam 7 Condensing lens 8 Collimating lens 9 Protection window 10 Sensor 11 Cable C Clearance W Work

Claims (3)

[Claims] In a laser welding machine for performing butt welding of a sheet metal work, a laser beam machining head is provided with:
The laser beam reflected light of the following work surface, visible light of the work surface, welding spatter amount, welding fume amount,
A sensor means for detecting at least one of the assist gas concentration, and comparing the output with a predetermined threshold value respectively set in order to prevent the occurrence of welding defects. A method and apparatus for monitoring a laser welding process, further comprising a control means for shifting to a means for performing the process. 2. The transfer means for preventing the occurrence of the welding defect involves stopping the current welding processing described below, skipping to the next processing operation, reworking by changing a laser beam focusing, and supplying a welding filler element. 2. The method for monitoring laser welding according to claim 1, wherein the method is any of re-machining. 3. A monitoring apparatus for laser beam welding, wherein the monitoring method for laser beam welding according to claim 1 is adopted.