JP3027654B2 - Laser marking method for steel plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for marking a steel sheet surface using a laser beam.

[0002]

2. Description of the Related Art As a method of engraving a product number, company mark, inspection organization mark, etc. on a steel sheet surface, there are a method of engraving manually with a hammer and the like and an automatic engraving machine of a hammer drop type. . However, manual work has a bad working environment and takes a long time. Further, the automatic stamping machine has disadvantages that it cannot cope with noise, consumption of the stamp, and changes in the character size and the stamping direction. For this reason, laser marking has been devised in which the engraved state is clear and uniform, and automation is easy. Laser-marked steel sheets are required to have a depth that does not disappear by exposure to air, shot blasting, heat treatment, and the like, and generally have a depth of about 100 μm or more. Therefore, a high-output pulse laser having energy on the order of J per pulse is required. As a laser marking device for steel plate
Japanese Patent Application Laid-Open No. 57-142785 proposes a device for dividing a laser beam, transmitting the divided laser beam through a fiber, collecting the laser beam at a focusing head, and moving the focusing head to perform marking. There is a method of performing marking by scanning a movable carriage equipped with such an optical system with a motor. 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. A galvano scan mirror and a marking device using a laser have already been put into practical use for ICs and the like. However, the size of the character is small, the marking depth is about several μm using a Q-switched laser, and the It is impossible to use as marking. Further, since a Q-switch laser capable of high repetition is used, characters and symbols to be engraved are represented as a dot pattern.
Japanese Patent Application Laid-Open No. 53444/1993 proposes a method for marking while taking the timing of laser oscillation with a scanning device such as a galvano scan mirror for each dot as proposed in JP-A-53444. Marking using a normal pulse laser having a low speed has a problem that it takes a long time.

[0003]

SUMMARY OF THE INVENTION The present invention does not provide a laser marking apparatus and a method for performing a simple and high-speed dot marking on a steel sheet surface by a dot pattern in a deep marking which is not erased by shot blasting or the like. It is assumed that.

[0004]

The gist of the present invention for solving the above problems is to provide a laser pulse of a normal pulse laser.
For scanning the beam on a flat surface
Laser mark on steel plate
Laser marking method for steel sheet to be
The size, position and character of the character to be engraved
Based on each data in the array of
Before the start point and end point of each recognized line segment
The scanning timing of the two galvano scan mirrors is changed.
Determined from the operation speed and operation delay time,
The normal oscillated based on the scanning timing
When irradiating a pulsed laser beam, the scanning
Only the section whose timing corresponds to the start point and end point of the line segment
Laser marking method for steel plate characterized by irradiation
Is the law.

That is, the character or symbol to be engraved is recognized not as a set of dots but as a set of line segments, and the galvano scan mirror recognizes each character or symbol based on information on two points, the start point and the end point of the line segment. Scanning and further confirming the position of the galvano scan mirror by assuming that the actual movement of the galvano scan mirror with respect to the drive signal is delayed with respect to the drive signal of the galvano scan mirror and adding a certain waiting time corresponding thereto in advance. The beam spot without scanning, and the normal pulse laser is adjusted to the galvano scan mirror at a predetermined timing. Only stop oscillation,
A laser marking method for steel sheets that enables high-speed and clear marking on steel sheets by independently oscillating independently without recognizing information on the scanning position of the laser beam by the galvano scan mirror during engraving is there.

[0006]

FIG. 1 shows a laser marking device used in the present invention.
The outline of is shown. The laser beam 2 emitted from the normal pulse YAG laser oscillator 1 is guided to a high-speed, high-precision beam scanning system 9 using two sets of galvano scan mirrors 3, 4. The galvano scan mirrors 3, 4 move the laser beam two-dimensionally by the drive system 10,
Further, the laser beam is applied to an fθ lens (or mirror) 5.
Is focused on the surface of the steel plate at a spot. On the other hand, the control computer 6 and the pulse control system 7 are for processing the marking information and controlling the laser oscillator 1. The side nozzle 8 is for blowing a gas such as dry air or argon to a processing point to promote evaporation during processing and to remove a melt. The marking information is composed of marking parameters and marking data input to the control computer. The marking parameter specifies the size of the character and the position of the character, and the marking data specifies the array of characters to be laser-marked. In response to the two pieces of information and the marking start command, the control computer operates a previously formed character forming program to convert the characters and symbols to be engraved into patterned data, and drives the galvano scan mirror 3 through the drive system 10. , 4 are scanned. After setting the frequency and output for the first time, the laser oscillator 1 receives an oscillation start signal from the control computer through a pulse control system at the start point of marking, and starts oscillation.

Next, an actual operation will be described with reference to a timing chart of signals at the time of marking shown in FIG. FIG.
(A) and (b) are signals sent from the drive system to the galvano scan mirror based on a command 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 moving speed of the galvano scan mirror is slower than the moving command speed, and the control computer sets a predetermined waiting time (~, ~, ~, ~) at a location where the movement pattern of the galvano scan mirror changes. ) Is incorporated, and a pattern command for engraving is transmitted to the drive system. This waiting time is a fixed time set in advance.When the movement pattern of the beam spot changes, such as when the character or symbol to be engraved is bent or cut, the position where the beam spot trajectory by the galvano scan mirror should be accurately engraved is determined. This is the time to pass. The galvano scan mirror scans the beam spot according to this signal, and does not transmit a signal for confirming that the beam spot has certainly arrived at the on / off position of laser oscillation as in the case of the above. The control computer transmits the laser oscillation start and end instructions to the pulse control system at a predetermined time based on an operation signal to the galvano scan mirror, at a location where marking is necessary and at an unnecessary location. The pulse control system transmits a signal of a pulse cycle 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 with the galvano scan mirror. Proceed with engraving.

In the conventional marking method (for example, see
JP-A-8-53444) Characters are decomposed into all pieces of dot information, and laser irradiation is performed after confirming that the galvano scan mirror has moved to a predetermined dot each time.
The number of times of transmission / reception has become very large, and as a result, the time for signal exchange in the marking has been increased, and the time taken for the marking has been increased. On the other hand, in the present method, since the control computer unilaterally sends a command and independently controls the galvano scan mirror and the laser oscillator, the time required for these can be greatly reduced, and high-speed marking can be performed. Since the distance between dots forming characters and symbols to be engraved is determined by the frequency and the speed of the galvano scan mirror, the number of pulses is determined according to the size of the character so as not to impair visibility. Generally, it is sufficient if this distance is within about 0.2 to 2 times the dot diameter.
At this time, the depth of one dot is required to be about 100 μm or more so as not to be lost by shot blast processing or the like.
The energy of the laser pulse is required to be about 1J or more,
Considering practical use of pulse repetition, about 30 Hz or more is required. Due to such oscillation conditions, marking on a steel sheet is impossible with a Q switch, 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]

FIG. 3 is a block diagram of a control system of the marking device used in the embodiment. In the embodiment, the pulse control system 7 is constituted by the pulse generator 11 and the gate controller 12.
The oscillation frequency of the YAG laser oscillator 1 is not directly controlled by the pulse generator 11, but the laser oscillation is turned on / off from the control computer 6 to the gate controller 12.
The signal f was sent, the signal from the pulse generator 11 was gated by the gate controller 12 to produce the signal shown in FIG. 2D, and the laser oscillator was controlled. The galvano scan mirror driving system 10 includes 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 galvano scan mirror controller 13 and sent to the galvano scan mirror driver 14 to generate the signals shown in FIGS. The directional galvano scan mirror 4 was driven. The control system of the present invention can be constituted by such a simple combination of controllers, and one of its features is that the manufacture of the apparatus is easy.

In the above laser marking device, the laser oscillator is a normal pulse Y having a maximum rated output of 400 W.
Using an AG laser oscillator, pulse energy 3 J / P,
Marking was repeatedly performed under the condition of 130 pps. The optical system used was an fθ lens with f = 100 mm. "A" for hot rolled sheet
When 9 characters of the alphabet “BCDEFGHI” were engraved in each character size of 8 mm square, engraving was completed in approximately 2.5 seconds. The laser irradiation mark forming each engraved character had a hole diameter of 500 μm and a hole diameter of 500 μm. The depth was 500 μm, which sufficiently satisfied the conditions required for engraving on a steel plate.The same engraved characters were decomposed into dot information, and the position of the galvano scan mirror was checked for each dot, and the laser beam was emitted. In the case of using the marking method used in the conventional irradiating IC or the like, the engraving time is about 8 seconds. According to the present invention, it is possible to realize a high-speed engraving three times or more as compared with the conventional engraving technology. did it.

The laser of the present invention is not limited to a YAG laser, but may be a pulsed CO ₂ laser. Although not used in the present embodiment, using an optical fiber to guide the laser beam to the galvano scan mirror simplifies the handling of the beam and simplifies the device configuration.

[0013]

As described above, according to the present invention, high-speed and clear laser marking on a steel plate can be performed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a laser marking device according to one embodiment of the present invention.

FIG. 2 is a conceptual diagram of a marking method using a laser marking device according to an embodiment of the present invention.

FIG. 3 is a block diagram of a control system of the laser marking device used in one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 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

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Fumihiko Nishizawa 2-6-3 Otemachi, Chiyoda-ku, Tokyo Inside Nippon Steel Corporation (72) Inventor Tetsuo Seito 46-59 Nakahara, Oaza, Tobata-ku, Kitakyushu New Nippon Steel Corporation Machinery & Plant Division (72) Inventor Yuji Otsuka 1 Kimitsu, Kimitsu City, Chiba Prefecture Inside Kimitsu Works, Nippon Steel Corporation (72) Inventor Yoshio Takahashi 18- 18 Misawa Minamicho, Kanagawa-ku, Yokohama-shi 4 (56) References JP-A-57-142785 (JP, A) JP-A-58-53444 (JP, A) JP-A-2-299786 (JP, A) JP-A-3-178462 (JP, A) JP-A-63-295080 (JP, A) JP-A-60-106686 (JP, A) JP-A-1-224192 (JP, A) JP-B-62-13117 (JP, B2) (58) (Int.Cl. ⁷ , DB name) B23K 26/00

Claims (1)

(57) [Claims] 1. A laser beam of a normal pulse laser
Sets of galvanometer scans for scanning
Laser marking on the steel sheet after passing through the mirror
In the method of laser marking on steel plate, the size of the character to be engraved, the position of the character, the text
A set of line segments for each character and symbol based on the data in the character array
Recognized as the start and end points of each recognized line segment
The scanning timing of the two galvano scan mirrors is
Determined from the operation speed and operation delay time
The normalizer that oscillates freely based on the scanning timing
When irradiating the laser beam of
The inspection timing is the section corresponding to the start point and end point of the line segment
Marking on steel plate characterized by irradiation
Method.