JPH06312280A - Method for laser beam marking onto steel plate - Google Patents

Abstract

(57) [Abstract] [Object] The present invention does not provide a laser marking method for performing simple, high-speed, deep marking with a uniform dot pattern that does not disappear due to shot blasting or the like in a device for laser marking on the surface of a steel sheet. It is what [Structure] In a device for marking a steel plate with a laser, characters and symbols to be engraved are recognized as a set of line segments, and a galvano-scan mirror is used to display information on two points, that is, the start point and the end point of the line segments that make up each character and symbol. The beam spot is scanned without confirming the position of the galvano-scan mirror based on it, and the normal pulse laser is oscillated only at the gaps between the line segments from the end point to the start point of the line segment set. A laser marking method for steel sheets that enables high-speed and clear marking on steel sheets.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for marking on the surface of a steel sheet using a laser beam.

[0002]

2. Description of the Related Art As a method of marking a product number, a company mark, an inspection agency mark, etc. on the surface of a steel sheet, there are a method of manually marking with a hammer and an automatic marking machine by a hammer drop type. . However, there are drawbacks in that the manual work environment is bad and it takes a long time, and the automatic marking machine cannot cope with noise, consumption of the marking punch, and changes in the character size and marking direction. Under such circumstances, laser marking has been devised which has a clear and uniform marking state and is easy to automate. The laser-marked steel plate is required to have a depth that does not disappear by exposure to the atmosphere, shot blasting, heat treatment, etc. Generally, the depth must be about 100 μm or more. Therefore, a high-power pulse laser having an energy on the order of J per pulse is required. As a laser marking device for a steel sheet, a device for marking by dividing a laser beam as described in Japanese Patent Publication No. 62-13117 and transmitting it with a fiber and collecting it into a focusing head and moving the focusing head is disclosed. There is a method of performing marking by scanning a moving carriage equipped with an optical system as proposed in Japanese Patent Publication No. 57-142785 by a motor. But the former because control a laser oscillation by a shutter, and the latter has a disadvantage that neither too much time since the moving carriage to scan by a motor. Further, a marking device using a galvano scan mirror and a laser has already been put into practical use for ICs and the like, but this has a small character size, uses a Q-switch laser, and has a marking depth of about several μm. It cannot be used as a marking. Also, high repeatability Q
Since a switch laser is used, this is a method of representing characters or symbols to be engraved as a dot pattern.
A method of marking each dot while keeping the timing of laser oscillation with a scanning device such as a galvano scan mirror as proposed in Japanese Patent No. 53444 is adopted, and this method complicates data exchange, Marking using a normal pulse laser with slow repetition has a problem that it takes time.

As a means for solving such a problem, the inventors of the present invention have disclosed in Japanese Patent Application No. 04-232575 that a normal pulse laser is used in a laser marking device for a steel sheet.
A beam scanning system composed of two sets of galvano scan mirrors for scanning the laser beam, a drive system for driving the galvano scan mirrors, an fθ lens or mirror for condensing the laser beam, and a control computer for processing marking information. A laser marking device for a steel plate, which comprises a pulse control system for controlling the oscillation of a laser oscillator so as to stop the oscillation of the laser in a portion where the marking is not performed, and the marking character in the laser marking device. , The symbol is recognized not as a set of dots but as a set of line segments, and the galvanoscan mirror is scanned based on the information of two points of the start and end points of the line segments forming each character and symbol, and further the galvanoscan mirror Drive signal, the actual movement of the galvano scan mirror is delayed with respect to the drive signal. Assuming things, by putting in advance a certain waiting time corresponding thereto scans without beam spot to check the position of the galvano-scan mirror,
In addition, the pulse control system stops the oscillation of only the gap between the line segments in the line segment set from the end point to the start point of the normal pulse laser at a pre-determined timing matched with the galvano scan mirror, and during engraving. The invention of a laser marking method for a steel sheet enables high-speed and clear marking on a steel sheet by freely oscillating independently without recognizing the information on the scanning position of the laser beam by the galvano scan mirror. Is pending.

However, in the above-mentioned inventions of the inventors, since the marking is not performed while sequentially sensing the actual marking position, for example, if there is a point where a line segment intersects in a character, it happens to occur. In addition, there is a possibility that only the marking near the intersection will become deeper by irradiating the laser near the intersection multiple times. In the engraving of steel sheets, the hole shape of the engraving is often specified in detail in order to maintain the characteristics of the steel sheet, and there is a problem that such deep engraving of the engravings may deteriorate the characteristics of the steel sheet. .

[0005]

DISCLOSURE OF THE INVENTION The present invention is a laser marking method for performing a deep and uniform marking with a uniform dot pattern at a simple and high speed so as not to be erased by shot blasting in a device for laser marking on the surface of a steel sheet. It is intended to provide a method.

[0006]

The gist of the present invention for solving the above problems is to provide a normal pulse laser and a beam scanning system comprising two sets of galvano scan mirrors for scanning a laser beam, A drive system for driving the galvanoscan mirror, an fθ lens or mirror for converging a laser beam, a control computer for processing marking information, and a laser oscillator for stopping laser oscillation in a portion where no marking is performed. In the method of marking on the surface of a steel sheet using a device that marks a steel sheet with a laser equipped with a pulse control system for controlling, the letters and symbols to be marked are recognized not as a set of dots but as a set of line segments and Or, at the point where the line segments in the symbol intersect, other line segments except one that intersect The galvanoscan mirror is configured by a pattern that is interrupted later, and the galvanoscan mirror is scanned based on the information of two points of the start point and the end point of the line segment that configures each character and symbol. On the other hand, assuming that the actual movement of the galvano-scan mirror is delayed, a certain waiting time corresponding to that is inserted in advance to scan the beam spot without confirming the position of the galvano-scan mirror, and the normal pulse laser is used to scan the beam spot. At the timing determined in advance according to the scan mirror, the pulse control system stops the oscillation of only the gap between the line segments from the end point to the start point of the line segment set, and the laser by the galvano scan mirror during the marking. Freely oscillates independently without recognizing beam scanning position information It is a high speed and the laser marking method of the steel sheet to enable a clear marking.

[0007]

FIG. 1 schematically shows a laser marking device used in the present invention. A laser beam 2 emitted from a normal pulse YAG laser oscillator 1 is guided to a high-speed and high-precision beam scanning system 9 using two sets of galvano scan mirrors 3 and 4. Galvano scan mirrors 3 and 4
The laser beam is moved two-dimensionally by the drive system 10,
Further, the laser beam is fθ lens (or mirror) 5
Is focused by a spot on the surface of the steel sheet. On the other hand, the control computer 6 and the pulse control system 7 are for processing marking information and controlling the laser oscillator 1. The side nozzle 8 is for spraying a gas such as dry air or argon to a processing point for promoting evaporation during processing and removing a molten material. The marking information is
It consists of marking parameters and marking data input to the control computer. The marking parameter is to specify the size of the character and the position of the character, and the marking data is to specify the array of characters to be laser-marked. Based on these two pieces of information and the marking start command, the control computer operates a pre-made program for forming characters to form the characters and symbols to be engraved into patterned data, and through the drive system 10, the galvano scan mirror 3 4 is scanned. The laser oscillator 1 receives an oscillation start signal from the control computer through the pulse control system at the marking start point after first setting the frequency and output, and starts oscillation.

Next, the actual operation will be described based on the timing chart of the signal at the time of marking shown in FIG. Figure 2
(A) and (b) are signals sent from the drive system to the galvanoscan mirror based on a command from the control computer, (c)
Is a signal sent from the control computer to the pulse control system,
(D) is a signal sent from the pulse control system to the laser oscillator, (e) is the output of the laser oscillator, and (f) is the actual marking. The control computer anticipates that the actual movement speed of the galvanoscan mirror will be delayed with respect to the movement command speed, so that a predetermined waiting time (~
, ~, ~, ~) Are incorporated and the pattern command of the marking is transmitted to the drive system. This waiting time is a preset fixed time, and when the movement pattern of the beam spot changes, such as when the characters or symbols to be engraved are bent or broken, the trajectory of the beam spot by the galvano scan mirror passes through the point that should be engraved accurately. It is time to set it up. The galvanoscan mirror scans the beam spot according to this signal, and does not send a signal for confirming that the beam spot has certainly arrived at the on / off position of laser oscillation. The control computer transmits a laser oscillation start / end command to the pulse control system at a predetermined time based on the operation signal to the galvano scan mirror, indicating the necessary and unnecessary portions for marking. The pulse control system transmits a signal having a pulse period corresponding to laser repetition to the laser oscillator in accordance with the laser oscillation start and end signals. As can be seen, the control computer unilaterally only sends commands to the drive system and the pulse control system, and oscillates and stops the laser without checking the position of the beam spot by scanning the galvano scan mirror. I will proceed with the engraving.

In such a method in which the position of the beam spot during marking is not sequentially sensed and controlled, if there is an intersection in the marking character or symbol as shown in FIG. 3, there is a risk that the laser beam will be hit twice at that intersection. There is. Alternatively, it is possible that the marking dots partially overlap even if they do not completely overlap. Since many of the steel sheets to which the present invention is symmetrical are used for special purposes, their characteristics are strictly controlled, and the dot shape of the engraving is defined in terms of depth and curvature in order to prevent deterioration of steel sheet characteristics. There is a case. Therefore, in the present invention, in order to avoid such dot overlap, when creating data of characters and symbols to be imprinted, as shown in FIG.
Except for one line segment, other line segments are created so that the line segments are interrupted before and after the intersection. As a result, it is possible to carry out double-printing and uniform marking with no change in the marking dot depth or shape due to partial overlap.

In the conventional marking method (for example, Japanese Patent Laid-Open No.
(8-53444 gazette) Characters are decomposed into all dot information, and laser irradiation is performed after confirming that the galvanoscan mirror has moved to a predetermined dot each time, so the number of transmissions and receptions becomes very large. As a result, the time required for exchanging signals in marking was increased, and the time required for marking was increased. On the other hand, in the present invention, the control computer sends a command unilaterally and controls the galvanoscan mirror and the laser oscillator independently, so that the time required for them is greatly saved and high-speed marking is possible. Since the distance between the dots forming the characters or symbols to be engraved is determined by the frequency and the speed of the galvanometer mirror, the number of pulses is determined according to the size of the characters so as not to impair the visibility. Generally, this distance is sufficient if the distance between the centers of the dots is within 0.2 to 2 times the dot diameter. At this time, the depth of 1 dot is required to be about 100 μm or more so as not to be erased by shot blasting or the like, so the energy of the laser pulse is required to be about 1 J or more, and the pulse repetition rate is 30
z or more is required. It is not possible to use a Q switch to mark the steel sheet under such oscillation conditions, and it is desirable to use a normal pulse laser.

Although each signal in FIG. 2 is shown as a voltage signal for the sake of convenience, it is of course possible to use a non-voltage signal such as TTL.

[0012]

EXAMPLE FIG. 5 is a block diagram of the marking device used in the example. In the embodiment, the pulse control system 7 is composed of the pulse generator 11 and the gate controller 12. Instead of directly controlling the oscillation frequency of the YAG laser oscillator 1 by the pulse generator 11, a laser oscillation on / off signal is sent from the control computer 6 to the gate controller 12, and the gate controller 12 gates the pulse generator signal. The signal of (d) of FIG. 2 was produced by multiplying by, and the laser oscillator was controlled. The galvano scan mirror drive system 10 is composed of a galvano scan mirror controller 13 and a galvano scan mirror driver 14. The drive signal from the control computer is DA converted in the galvanoscan mirror controller 13 and sent to the galvanoscan mirror driver 14 to generate the signals shown in FIGS. 2 (a) and 2 (b), and the galvanoscan mirror 3 for the X direction and the Y direction. The galvanoscan mirror 4 was driven. One of the features of the control system of the present invention is that it can be constructed by combining such simple controllers and that the device can be easily manufactured.

In the above laser marking apparatus, the laser oscillator is a normal pulse Y with a maximum rated output of 400 W.
Using an AG laser oscillator, pulse energy 3 J / P,
The marking was repeated under the condition of 130 pps. The optical system used an fθ lens with f = 100 mm. "A" on hot rolled sheet
The 9 letters of BCDEFGHI ”were engraved with each character size of 8 mm square, and the engraving was completed in about 2.5 seconds. The laser irradiation mark forming each engraved character had a hole diameter of 500 μm and a hole depth. The size is 500 μm, which sufficiently satisfies the conditions necessary for marking steel plates, and the dot overlapping near the intersections of the line segments of the characters was not found, and the marking with uniform dots was realized. When the marking method used in the conventional IC etc. which decomposes into dot information and confirms the position of the galvanoscan mirror for each dot and irradiates the laser beam, the marking time is about 8 seconds. According to the present invention, it is possible to realize high-speed marking three times or more compared with the conventional marking technology.

Further, not only a YAG laser but also a pulsed CO2 laser can be used as the laser of the present invention. Although not used in this embodiment, using an optical fiber to guide the laser beam to the galvanoscan mirror simplifies the beam handling and simplifies the device configuration.

[0015]

EFFECTS OF THE INVENTION The present invention enables high-speed and clear laser marking on a steel sheet.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a laser marking device.

FIG. 2 is a conceptual diagram of a laser marking method of the present invention.

FIG. 3 is a conceptual diagram in the case where marking dots are not uniform at intersections.

FIG. 4 is a conceptual diagram of a method for avoiding the occurrence of marking dot nonuniformity at intersections according to the present invention.

FIG. 5 is a configuration diagram of a laser marking device used in an example of the present invention.

[Explanation of symbols]

 1 Normal pulse YAG laser oscillator 2 Laser beam 3,4 Galvano scan mirror 5 fθ lens (mirror) 6 Control computer 7 Pulse control system 8 Side nozzle 9 Beam scanning system 10 Galvano scan mirror drive system 11 Pulse generator 12 Gate controller 13 Galvano Scan mirror controller 14 Galvano scan mirror driver

Claims (1)

[Claims] 1. A beam scanning system comprising a normal pulse laser, two sets of galvano scan mirrors for scanning the laser beam, a drive system for driving the galvano scan mirror, and an fθ lens or mirror for condensing the laser beam. And a control computer that processes the marking information and a pulse control system that controls the oscillation of the laser oscillator so as to stop the oscillation of the laser in the portion where the marking is not performed. In the method of marking on the surface, the characters or symbols to be marked are recognized not as a set of dots but as a set of line segments, and at the intersection of line segments in a character or symbol, one line segment that intersects is excluded. The line segment is composed of a pattern that is interrupted before and after the intersection. Scanning based on the information of the two points of the start point and the end point of the line segment that makes up the signal, and assuming that the drive signal of the galvanoscan mirror delays the actual movement of the galvanoscan mirror with respect to the drive signal, The beam spot is scanned without confirming the position of the galvanoscan mirror by inserting a certain waiting time corresponding to it, and the line is controlled by the pulse control system at a predetermined timing matched with the normal pulse laser to the galvanoscan mirror. Oscillation is stopped only at the breaks between each line segment from the end point to the start point in the segment set, and during engraving, the information on the laser beam scanning position by the galvano scan mirror is not recognized at all and can be set independently. Laser marking method for steel plates that enables high-speed and clear marking on steel plates by oscillating .