JP3262391B2 - Laser marking abnormality detection 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 method for detecting an abnormality in laser marking.

[0002]

2. Description of the Related Art In recent years, laser marking has been increasingly used to replace mechanical and chemical marking. In laser marking, as illustrated in FIG. 2, a laser beam emitted from a laser oscillator 6 is condensed on a workpiece 1 to be marked via a driving mirror 5 and a condensing lens 4 to form a mark. By driving the drive mirror 5 in response to deflect the direction of the reflected light, the laser spot formed on the surface of the workpiece 1 is moved to record a required mark.

However, in the laser marking apparatus of this configuration, the laser oscillator and the mirror drive system are broken, and the workpiece to be marked has low rigidity, such as a piston ring, and the workpiece is marked. When marking the part between the curves where the width of the part is thin and narrow, the laser spot deviates from the processing surface of the workpiece, including the problem of the transport system for transporting the workpiece to the processing position,
If the head or upper part of the mark is missing or severe, problems such as no mark occur.

[0004] To confirm the presence or absence of laser oscillation, for example, in a commercially available laser marker device having the configuration shown in FIG. 2, a laser oscillation confirmation sensor 7 is attached to the laser oscillator 6 to feed back a laser oscillation signal. Although the presence or absence of laser oscillation is confirmed by semi-closed control by the method described above, it is not possible to confirm the failure of the mirror drive system or the marking state of the workpiece during machining, so after machining, There was a problem that a visual inspection or a confirmation step by an automatic mark inspection machine was required separately.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems relating to the detection of abnormal marking by a conventional laser marking apparatus, and has been made of, for example, a metal working having a narrow width and a curved edge like a piston ring. It is an object of the present invention to provide a laser marking abnormality detection method that can detect marking abnormality simultaneously with laser marking on an object and can control quality and rationalize an inspection process.

[0006]

According to the present invention, there is provided a method for detecting an abnormality in laser marking of a metal workpiece, which comprises the steps of: The detected light emission intensity and the temporal light emission pattern are set in advance according to processing conditions such as the material of the workpiece, surface treatment, surface condition, laser intensity, and the shape of the processing mark, and stored in the storage means. And comparing it with a temporal pattern to determine an abnormality from the difference.

[0007]

According to the laser marking abnormality detection method of the present invention, when marking is performed by irradiating the surface of a metal with a laser, when a laser spot hits a workpiece, a light emission phenomenon occurs at that portion due to the energy of the laser. It is a thing that utilizes that. It is known that this light emission phenomenon has a substantially constant light emission intensity depending on the laser intensity, the material of the workpiece, and the surface condition.

Therefore, at the same time as the laser marking, the light emission intensity and the temporal pattern of the marking portion are detected as an electric quantity by a photoelectric sensor, and are set in advance according to the laser intensity, the material of the workpiece, the surface condition, the shape of the mark to be marked, and the like. By comparing the stored light emission intensity with the temporal pattern, it is possible to detect the laser oscillation intensity abnormality and the displacement of the marking with respect to the workpiece. It is presumed that the mirror drive system is faulty, the workpiece is transported abnormally, or a different type of product is mixed in, based on the misalignment of the marking with respect to the workpiece. .

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing an example of a laser marking device provided with a device for performing the laser marking abnormality detection method of the present invention. In this device, a photoelectric sensor 2 is provided at a position where the light emission intensity of a portion that is emitted from a laser oscillator 6 and passes through a driving mirror 5 and a condenser lens 4 and is laser-marked on the surface of the workpiece 1 can be detected. Have been. The light emission intensity detected by the photoelectric sensor 2 is converted into an electric signal, and is input to the pattern recognition device 3, and the temporal pattern of the light emission intensity is displayed on an image display means such as a CRT. On the image display means, patterns set in advance in accordance with processing conditions such as the laser emission intensity, the material of the workpiece, the surface condition, the shape of the mark to be marked, and the like and stored in the memory are also displayed in comparison. By comparing the two, it is determined whether the marking is performed normally or abnormally. If the pattern shape is normal and the overall level is low, it is determined that the output of the laser oscillator has decreased, and If the temporal light emission pattern is different from the stored pattern, an aspect such as top missing or head missing is determined according to the manner of the difference. Further, the laser oscillation confirmation sensor 7 of the conventional device becomes unnecessary.

Table 1 shows the marking state and the temporal light emission pattern in the case of normal, top missing, and head missing in an example where the abbreviation of the manufacturer name is marked at the end of the abutment portion of the piston ring.

[0011]

[Table 1]

In a normal state, a light emitting pattern in which three patterns each having a width corresponding to the width of each character of RIK are obtained. In the case of an upper chip, a portion connecting horizontally at the center of the heights of the characters R and K is missing, so that a pattern in which a plurality of small width portions are arranged respectively is obtained, and the light emission intensity is also reduced. In the case of a missing head, the left portion of the letter R is missing, so that the width is reduced.
Therefore, the marking state can be determined by looking at the light emission pattern. As a result, the output of the laser oscillator can be reduced, the drive mirror can be broken, the conveyance of the processed product can be estimated, and a countermeasure can be taken promptly.

[0013]

As described above, according to the present invention, laser marking abnormalities can be detected at the same time as laser marking is performed on a metal workpiece, and a remarkable effect can be obtained in quality control and rationalization of the inspection process. be able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a laser marking device provided with a means for performing a laser marking abnormality detection method of the present invention.

FIG. 2 is a sectional view showing an example of a conventional laser marking device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal workpiece 2 Photoelectric sensor 3 Pattern recognition device 4 Condensing lens 5 Drive mirror 6 Laser oscillator

Claims (1)

(57) [Claims] In a marking abnormality detecting method for marking a metal workpiece with a laser, simultaneously with the marking by the laser, a light emission intensity of a marking portion of the workpiece is detected by a photoelectric sensor. a temporal light emission pattern, the material of the workpiece, surface treatment, surface condition, laser intensity, depending on the processing conditions such as the shape of the machining marks originating having stored in the preset memory means
An abnormality detection method characterized by comparing a light intensity with a temporal light emission pattern to determine a marking abnormality from the difference.