JPH0655282A - Laser marking device for steel sheet and method therefor - Google Patents

Abstract

PURPOSE:To easily execute deep marking in dot patterns at a high speed by introducing the laser beam from a normal pulse YAG laser oscillator to a beam scanning system utilizing two sets of galvano-scan mirrors. CONSTITUTION:The oscillation frequency of the YAG laser oscillator 1 is not directly controlled by a pulse generator but a signal for on/off of laser oscillation is sent toward a gate controller from a control computer 6 and a gate is applied to the signal of the pulse generator by the gate controller to form a signal, by which the laser oscillator 1 is controlled. The driving signal from the computer 6 is subjected to DA conversion in a galvano-scan mirror controller and is sent to a galvano-scan mirror driver, by which the signal is formed to drive the galvano-scan mirror 3 for an X direction and the galvano-scan mirror 4 for a Y direction. The control system is constituted by a combination of such simple controllers and the production of the device is facilitated.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an apparatus and method for marking on a steel sheet surface 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, the manual work requires a long working time in a bad working environment. Further, the automatic marking machine has drawbacks that it cannot cope with noise, consumption of the marking punch, and changes in character size and marking direction. For these reasons, 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. Japanese Patent Publication Sho 62
No. 57-142785, and a device for dividing a laser beam, which is proposed in Japanese Laid-Open Patent Publication No. 13117, transmitted by a fiber, collected in a focusing head, and moved by moving the focusing head, and JP-A-57-142785. There is a method in which a moving carriage equipped with such an optical system is scanned by a motor for marking. But the former because control a laser oscillation by the 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 galvanoscan mirror and a laser has already been put to 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. Further, since a Q-switched laser capable of high repetition rate is used, it is a method in which characters or symbols to be marked are expressed as a dot pattern.
There is a method of marking each dot while keeping a timing of laser oscillation with a scanning device such as a galvano scan mirror as proposed in Japanese Patent No. 53444, and this method complicates data exchange, and repeats. However, there is a problem that it takes time in marking using a slow normal pulse laser.

[0003]

DISCLOSURE OF THE INVENTION The present invention does not provide a laser marking device and method for simply and rapidly performing deep marking with a dot pattern that does not disappear by shot blasting in a device for laser marking on the surface of a steel sheet. It is what

[0004]

The gist of the present invention for solving the above-mentioned problems is to provide an apparatus for marking a steel sheet with a laser, in which a normal pulse laser and two sets of galvano-scan mirrors for scanning the laser beam are used. Beam scanning system, a drive system for driving the galvano scan mirror, and fθ for condensing the laser beam
A laser for a steel plate, comprising a lens or a mirror, a control computer for processing marking information, and 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 marking is not performed. It is a marking device.

In the above laser marking device, the characters and symbols to be engraved are recognized as a set of line segments, not as a set of dots, and the galvanoscan mirror is used for the two points of the start and end points of the line segments that make up each character and symbol. Scanning based on the information of the galvano scan mirror, and assuming that the actual movement of the galvano scan mirror is delayed with respect to the drive signal of the galvano scan mirror, a certain waiting time corresponding to that is inserted in advance to scan the galvano scan mirror. The beam spot is scanned without confirming the position of the mirror, and the normal pulse laser is adjusted from the end point to the start point of the line segment in the line segment set by the pulse control system at a predetermined timing matched with the galvano scan mirror. Oscillation is stopped only at the gap between each line segment, and a galvano scan mirror is used during marking. Without completely recognize the information of the scanning position of Zabimu, by free oscillation independently to allow high speed and sharp marking on the steel sheet, a laser marking method of the steel sheet.

[0006]

1 shows the outline of the laser marking apparatus of the present invention. The laser beam 2 emitted from the normal pulse YAG laser oscillator 1 has two sets of galvano scan mirrors 3 and 4.
To a high-speed and high-precision beam scanning system 9 utilizing Galvano scan mirrors 3 and 4 are drive system 1
The laser beam is two-dimensionally moved by 0, and the laser beam is converged by a spot on the surface of the steel plate by the fθ lens (or mirror) 5. 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 blowing gas such as dry air or argon to the processing point in order to promote evaporation during processing and to remove the molten material. The marking information is composed 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 characters, symbols, etc. to be engraved into patterned data, and the galvano scan mirror 3 through the drive system 10. , 4 are 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 signals at the time of marking shown in FIG. Figure 2
(A) and (b) are signals sent from the drive system to the galvano scan mirror based on commands from the control computer,
(C) is the signal sent from the control computer to the pulse control system, (d) is the signal sent from the pulse signal 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 (~, ~, ~, ~) is set at the changing point of the movement pattern of the galvanoscan mirror. ) Is incorporated and a marking pattern command is transmitted to the drive system. This waiting time is a preset fixed time, and when the beam spot movement pattern changes due to changes in the movement pattern of the beam spot, such as bending or breaking of the characters or symbols to be engraved, the position of the beam spot traced by the galvano scan mirror should be accurately marked. It is time to set up to pass. 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 commands for starting and ending laser oscillation to the pulse control system at required and unmarked points at predetermined times based on operation signals to the galvanoscan mirror. 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 only unilaterally sends commands to the drive system and 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 the conventional marking method (for example, Japanese Unexamined Patent Publication No.
No. 8-53444) 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.
The number of times of transmission and reception was extremely large, and as a result, the time required for exchanging signals in the marking was long and the time required for marking was long. On the other hand, in this method, 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 imprinted is determined by the frequency and the speed of the galvanoscan mirror, the number of pulses is determined according to the size of the characters so as not to impair the visibility. Generally, it is sufficient if this distance is within 0.2 to 2 times the dot diameter.
At this time, the depth of 1 dot is required to be 100 μm or more so as not to disappear by shot blasting, etc.
The energy of the laser pulse is required to be about 1 J or more,
Considering practical use, pulse repetition also requires about 30 Hz or more. 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 convenience, it is of course possible to use a non-voltage signal such as TTL.

[0010]

EXAMPLE FIG. 3 is a block diagram of the control system 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, laser oscillation on / of is directed from the control computer 6 to the gate controller 12.
The signal of f was sent and the signal of the pulse generator 11 was gated by the gate controller 12 to produce the signal of FIG. 2 (d) to control the laser oscillator. The galvano scan mirror driving 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 6 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 Y The directional galvanoscan mirror 4 was driven. The control system of the present invention can be constructed by such a simple combination of controllers, and one of the features is that the device can be easily manufactured.

In the above laser marking device, 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" for hot rolled sheet
When the 9 letters of BCDEFGHI ”were engraved with each character size of 8 mm square, 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. The depth was 500 μm, which sufficiently satisfied the conditions necessary for marking a steel sheet.Also, similar marking characters were decomposed into dot information, and the position of the galvanoscan mirror was confirmed for each dot, and the laser beam was emitted. When the marking method used in the conventional IC to irradiate is used, the marking time is about 8 seconds, and the present invention makes it possible to realize high-speed marking three times or more as compared with the conventional marking technology. did it.

Further, not only a YAG laser but also a pulsed CO ₂ 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 handling of the beam and simplifies the device configuration.

[0013]

As described above, 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 that is an embodiment of the present invention.

FIG. 2 is a conceptual diagram of a marking method by a laser marking device that is an embodiment of the present invention.

FIG. 3 is a block diagram of a control system of a laser marking device used in an embodiment 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 Galvo scan mirror controller 14 Galvo scan mirror driver

 ─────────────────────────────────────────────────── --- Continuation of front page (72) Inventor Fumihiko Nishizawa 2-6-3 Otemachi, Chiyoda-ku, Tokyo Within Nippon Steel Corporation (72) Inventor Tetsuo Kiyoto 46-59 Nakahara, Tobata-ku, Kitakyushu (72) Inventor, Yuji Otsuka Yuji, Kimitsu City, Chiba Prefecture, Nippon Steel Co., Ltd., Kimitsu Works, Ltd. (72) Inventor, Yoshio Takahashi, 18-4, Misawa Minamimachi, Kanagawa-ku, Yokohama

Claims (2)

[Claims] 1. A device for marking a steel sheet with a laser, comprising: a normal pulse laser; a beam scanning system including two sets of galvano scan mirrors for scanning a laser beam; and a drive system for driving the galvano scan mirrors. An fθ lens or mirror for condensing the laser beam, a control computer for controlling the marking information, and a pulse control system for controlling the oscillation of the laser oscillator so as to stop the oscillation of the laser in a portion where the marking is not performed are provided. Laser marking device for characteristic steel sheets. 2. The laser marking device according to claim 1, wherein the characters and symbols to be engraved are not a set of dots,
Recognized as a set of line segments, the galvanoscan mirror is scanned based on the information of the two points of the start and end points of the line segments that make up each character and symbol, and the drive signal of the galvanoscan mirror is compared with the drive signal. Assuming that the actual movement of the galvano scan mirror is delayed, a certain waiting time corresponding to it is set 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 galvano scan mirror. At the timing determined in advance according to the mirror, the pulse control system stops oscillation only at the gaps between the line segments from the end point to the start point of the line segment set, and during engraving the laser beam by the galvano scan mirror By oscillating independently, without recognizing the information of the scanning position of Laser marking method of the steel sheet, characterized in that to enable fast and clear marking.