JPH06148026A - Method for detecting failure in laser marking - Google Patents

Abstract

PURPOSE:To rationalize quality control and inspection processes by detecting a failure in laser marking at the same time as applying laser-marking to a product having a narrow curved rim such as a piston ring. CONSTITUTION:At the same time as marking by laser 6, luminous intensity at a marked portion of a product 1 is sensed by a photoelectric sensor 2, so that the sensed luminous intensity and a luminous time pattern are compared with preset intensity and time pattern according to processing conditions thereby determining whether the product is good or defective.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser marking abnormality detection method.

[0002]

2. Description of the Related Art Laser marking has recently gained momentum to replace mechanical and chemical marking. In laser marking, as illustrated in FIG. 2, a laser beam emitted from a laser oscillator 6 is focused on a workpiece 1 to be marked via a driving mirror 5 and a condenser lens 4 to form a mark shape. Accordingly, the driving mirror 5 is driven to deflect the direction of the reflected light, thereby moving the laser spot formed on the surface of the workpiece 1 to record a required mark.

However, in the laser marking device having this structure, the laser oscillator and the mirror drive system have a failure, the workpiece to be marked has a low rigidity such as a piston ring, and the workpiece is marked. The laser spot deviates from the machined surface of the workpiece, including the problem of the transport system for transporting the workpiece to the processing position when marking the portion where the width of the workpiece is narrow and sandwiched by curves.
If the head or upper part of the mark is missing, or if it is severe, problems such as no mark occur.

Regarding the confirmation of the presence or absence of laser oscillation, for example, in the 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 the laser oscillation signal. Although the presence or absence of laser oscillation is confirmed by the semi-closed control by the method of, the mirror drive system failure and the marking state of the workpiece cannot be confirmed during processing. There is a problem that a visual inspection or a confirmation process by an automatic mark inspection machine is separately required.

[0005]

SUMMARY OF THE INVENTION The present invention is conceived in view of the above-mentioned problems relating to marking abnormality detection by a conventional laser marking device, and for example, metal working having a narrow width and a curved edge such as a piston ring. An object of the present invention is to provide a laser marking abnormality detection method capable of detecting marking abnormalities at the same time as laser marking on an object and achieving quality control and rationalization of an inspection process.

[0006]

A laser marking abnormality detection method for a metal work piece according to the present invention for solving the above-mentioned problems is to detect a light emission intensity of a marking part of a work piece by a photoelectric sensor at the same time as marking by a laser. Then, the detected emission intensity and temporal emission pattern are set in advance according to the processing conditions such as the material of the workpiece, the surface treatment, the surface condition, the laser intensity, and the shape of the processing mark, and the intensity is stored in the storage means. It is characterized in that the abnormality is judged from the difference by comparing with the temporal pattern.

[0007]

According to the laser marking abnormality detection method of the present invention, when a laser spot is struck on a workpiece when a metal surface is irradiated with the laser for marking, a light emission phenomenon occurs at that portion due to the energy of the laser. This is what is used. It is known that this light emission phenomenon has a substantially constant light emission intensity depending on the intensity of the laser, 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 a quantity of electricity by the 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, etc. Then, by comparing the stored emission intensity with the temporal pattern, it is possible to detect the positional deviation of the marking with respect to the workpiece as well as the abnormality of the laser oscillation intensity. From the misalignment of the marking with respect to the workpiece, it is estimated that the mirror drive system is faulty, the workpiece is abnormally conveyed, or different products are mixed. By checking these points, it is possible to take corrective action against the abnormality without delay. .

[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 apparatus provided with an apparatus for carrying out the laser marking abnormality detection method of the present invention. In this device, the photoelectric sensor 2 is provided at a position where the emission intensity of a portion emitted from the laser oscillator 6, passed through the driving mirror 5 and the condenser lens 4 and laser-marked on the surface of the workpiece 1 can be detected. Has been. The light emission intensity detected by the photoelectric sensor 2 is converted into an electric signal and 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, a pattern which is set in advance in accordance with processing conditions such as laser emission intensity, material of work, surface state, shape of mark to be marked, etc. and stored in the memory is also displayed for comparison. By comparing the two, it is determined whether the marking is performed normally or abnormally, and if the pattern shape is normal and the level is low overall, it is determined that the output of the laser oscillator is reduced, and If the temporal light emission pattern is different from the stored pattern, a mode such as top chipping or head chipping is determined depending on the difference. Further, the laser oscillation confirmation sensor 7 of the conventional device is unnecessary.

Table 1 shows a marking state and a temporal light emission pattern in the case of normal, top chipping, and head chipping in an example in which the abbreviation of the manufacturer name is marked on the end of the abutment part of the piston ring.

[0011]

[Table 1]

In a normal state, a light emitting pattern in which three patterns having a width corresponding to the width of each character of RIK are arranged is obtained. In the case of the top chipping, the part that connects horizontally at the center of the heights of the letters R and K is chipped, resulting in a pattern in which a plurality of parts with small widths are lined up, and the light emission intensity also decreases. In the case of a head loss, the left part of the letter R is missing, so the width becomes narrower.
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, and the processed product can be conveyed poorly, so that countermeasures can be taken promptly.

[0013]

As described above, according to the present invention, it is possible to carry out laser marking on a metal workpiece and at the same time detect an abnormality in laser marking, and obtain a remarkable effect in rationalizing quality control and inspection processes. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a laser marking device provided with a means for carrying out 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]

 1 Metal Workpiece 2 Photoelectric Sensor 3 Pattern Recognition Device 4 Condensing Lens 5 Drive Mirror 6 Laser Oscillator

Claims (1)

[Claims] 1. In a marking abnormality detection method for marking a metal workpiece with a laser, at the same time as the laser marking, the photoelectric sensor detects the emission intensity of the marking portion of the workpiece, and the detected emission intensity is Comparing the temporal emission pattern with the temporal pattern preset and stored in the storage means according to the processing conditions such as the material of the workpiece, the surface treatment, the surface condition, the laser intensity, and the shape of the processing mark. An abnormality detection method characterized by determining an abnormality from the difference.