JP3487928B2 - Laser power pulse control method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a pulse of a laser power supply, and more particularly, to a method of controlling a laser power supply for outputting a pulsed laser suitable for fine shape processing. The present invention relates to a pulse control method. [0002] Conventionally, in laser processing, the laser output must be controlled in accordance with the processing purpose.
This is performed using a rectangular pulse waveform as shown in FIG. In the figure, τon is a pulse on time, and τoff is a pulse off time. τon and τoff are both fixed times. T is a pulse period, which is given by τon + τoff, and a pulse frequency f is given by 1 / T. Therefore, the duty ratio indicating the pulse-on ratio is τon /
It is given by T. [0003] However, such a rectangular pulse is suitable for processing a fine shape as compared with a CW waveform (continuous waveform), but is used for cutting a fine shape having a thickness of a middle plate or more. Has limitations. That is, when cutting a material having a thickness greater than the medium thickness, for example, when cutting a fine shape such as a small hole or an acute-angled edge, it is important to control the heat input of the laser beam and the flow rate of the assist gas so as to be greatly affected by the processing shape and the like. Become. That is, it is necessary to appropriately suppress the oxidation reaction of the material. If this control is not successful, burning will occur during cutting and the machining will be extremely unstable. Therefore, in order to perform fine processing with good stability, it is important to increase the pulse-off time to cool the material whose temperature has increased due to the heat generated during the processing and to eliminate the plasma generated in the processed part. It becomes. However, in order to lengthen the pulse-off time, it is necessary to reduce the pulse frequency to shorten the pulse-on time as much as possible. However, if this method is employed, gouging occurs unless the processing speed is similarly reduced. It cannot be cut. [0006] For this reason, when performing fine processing, the processing speed is extremely reduced in order to obtain processing stability, so that there is a problem that the processing efficiency is extremely deteriorated and the running cost is increased. Further, in processing stainless steel or the like, since the viscosity of chromium oxide is high, it is necessary to extremely increase the flow rate of the assist gas, and there is a problem that the running cost is further increased. On the other hand, during the pulse-on time, both the energy from the laser beam and the energy from the oxidation reaction are efficiently consumed. However, if the width of τon is too long, the latter half of the pulse may be caused by a rise in the temperature of the material or the generation of plasma in the processed part. Experiments have confirmed that the processing efficiency is reduced, and that the processing speed is reduced if τoff is too long. That is, it can be said that a higher pulse frequency is preferable for processing. SUMMARY OF THE INVENTION An object of the present invention is to pay attention to the above-described conventional techniques, and simultaneously satisfies both a high frequency suitable for high-speed processing and a long pulse-off time suitable for stable processing. An object of the present invention is to provide a pulse control method of a laser power supply that can supply a pulse waveform. [0010] pulse control method of the laser power of the present invention according to claim 1 Means for Solving the Problems] In order to achieve the above object, a single processing head of the laser beam from the laser oscillator
Laser processing system that irradiates the workpiece from above and performs laser processing
A method of controlling a laser power supply using a high-frequency power supply control pulse train composed of a pulse-on signal instructing a high-frequency power supply to output laser light and a pulse-off signal instructing the high-frequency power supply to stop output. The pulse train is composed of a first pulse-on signal and a first pulse-off signal having a low frequency, and the first pulse-on signal is composed of a plurality of second pulse-on signals and a second pulse-off signal having a high frequency; time shorten the time of the first pulse-off signal in comparison with the, and to shorten the time of each one of said second pulse-off signal compared to the time of the first pulse-off signal, the second
Keep the pulse-on signal output constant and
Stepwise shortening within the first pulse-on signal; and / or
Alternatively, the time of the second pulse-off signal is set to one first pulse.
It is characterized in that it is lengthened stepwise within the Soon signal . In the pulse control method for a laser power supply according to the first aspect, the pulse-on signal of the high-frequency power supply control pulse train controls the high-frequency power supply to output a laser beam, and the pulse-off signal controls the high-frequency power supply to produce a laser. Stop the light output. Here, the high-frequency power supply control pulse train is composed of a low-frequency first pulse-on signal and a low-frequency first pulse-off signal,
The first pulse-on signal is composed of a plurality of high-frequency second pulse-on signals and second pulse-off signals . Also, the first
The time of the first pulse-off signal is shorter than the time of the pulse-on signal, and the time of each second pulse-off signal is shorter than the time of the first pulse-off signal . Furthermore, the second
Keep the pulse-on signal output constant and
Stepwise shortening within the first pulse-on signal; and / or
Alternatively, the time of the second pulse off signal is set to one first pulse off signal.
In the signal. Therefore, to the material
And / or controls the amount of heat input to the
It promotes cooling of the heat stored in the material. A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of a laser processing system 1 using a pulse control method for a laser power supply according to the present invention. A processing table 3 provided so as to be movable and positioned in the X-axis direction and the Y-axis direction;
And a work W is placed on the pallet 5. Therefore, the workpiece W is positioned at the processing position by moving the processing table 3 in the X-axis and Y-axis directions. On the other hand, a control device 9 is provided to perform laser processing according to the automatic processing program 7, and a laser oscillator 11 controlled by the control device 9 is provided. The laser oscillator 11 includes a high-frequency power supply 13, a control unit 15 for controlling the high-frequency power supply 13, and a resonance unit 17. Further, a bend mirror 21 and a condenser lens 23 for guiding the laser beam LB from the laser oscillator 11 to the processing head 19 are provided. Therefore, the processing table 3 is moved and positioned in the X-axis and Y-axis directions under the control of the controller 9, and the laser oscillator 11 is controlled to irradiate the work W on the processing table 3 with laser light LB to perform laser processing. Is performed. FIG. 3 shows an embodiment of a pulse train generator 25 for generating pulses used in the present invention. The pulse train generator 25 controls the high frequency power supply 13 to generate a pulse to emit a laser beam LB, and includes a CPU 27, a PC (program counter) 29, and a CLK (clock) 31. Therefore, τon, τof can be obtained from an input device or a memory device (not shown).
The set value relating to f is sent to the CPU 27, and based on this information, the CPU 27 controls the PC 29 to generate a pulse train, and this pulse train is sent to the high frequency power supply 13 to become a discharge pulse, and a desired light pulse is obtained. FIG . 1 shows a pallet of a laser power supply according to the present invention.
Various pulse trains used in the pulse control method are shown. Figure
1 (A) shows an example of each embodiment shown in FIGS. 1 (B) to 1 (E).
Features common to pulse trains are shown. In FIG. 1 (A)
As shown, this pulse consists of two pulse groups. One is a first pulse having a low frequency, which includes a first pulse on and a first pulse off. Another is the first
Within the pulse on, the second pulse is a high frequency second pulse in which the second pulse on and the second pulse off are repeated at regular intervals. That is, in the pulse waveform of FIG. 1A, the first pulse on is composed of τon1 to τon3, τoff2 and τoff3, and the first pulse off is equivalent to τoff4 (τoff1). Therefore, in order to obtain the same average output as that of the normal pulse shown in FIG. 4, this pulse has a longer first pulse on time and a shorter first pulse off time. Since this has the same effect as increasing the frequency, the processing speed can be increased. On the other hand, if the pulse-off time is shortened with a normal pulse, fine processing cannot be performed due to excessive heat input. This is because the second pulse-off time provided within the first pulse-on time is a cooling period. Can be avoided because it serves as Thereby, it is possible to stably perform the fine processing with the processing speed increased. FIG. 1B shows an embodiment of a pulse waveform used in the pulse control method for a laser power supply according to the present invention . This pulse is considered to be composed of two pulse groups as in the case of FIG. 1A, but the output of the second pulse-on having a high frequency is kept constant as shown in the figure.
It is characterized by the tau-on (τon) control in which the time is controlled so as to be gradually reduced . The average output is set to be the same as a normal pulse. In this pulse waveform, the second pulse-on time is gradually shortened within one first pulse-on time, but the second pulse-off time is constant, and the pulse-off time is divided into two stages, the first pulse-off and the second pulse-off. It is changing. That is, if τoff2 is set to the same width as τoff1, cooling and extinction plasma can be sufficiently performed, but since the processing speed is significantly reduced, τoff2 to τoff5 are τoff1
(Τoff6). Therefore, in the pulse waveform of FIG. 1B, the first pulse on is composed of τon1 to τon5 and τoff2 to τoff5, and the first pulse off is equivalent to τoff6 (τoff1). When such a pulse is used, the cooling of the material and the extinction of the plasma in the processed portion are sufficiently performed at τoff1, so that the width of τon1 can be increased. Therefore, the processing speed can be increased in this portion. The heat generated at τon1 can be cooled by τoff2 to extinguish the plasma, but the effect is smaller than τoff1. Therefore, the following τon
2 prevents processing efficiency per unit pulse width from being reduced by making it shorter than τon1. At this time, τon
When 2 is set to the same width as τon1, not only the processing efficiency is reduced due to the heat of the material and the plasma of the processing portion, but also the processing has a bad influence such as burn-through of an edge portion or a burning phenomenon. Because. In the same manner, by gradually shortening to τon3, τon4, and τon5, processing can be performed without lowering the processing efficiency per pulse width. Then, since the first pulse is turned off at τoff6, the material can be cooled again and the plasma depleted in the processed portion can be sufficiently performed again, and stable processing can be performed. FIG. 1C shows another embodiment of the pulse waveform used in the pulse control method of the laser power supply according to the present invention . This pulse is a tau-off (τoff) control in which the second pulse-on time in FIG. 1A is made constant and the second pulse-off time is gradually increased. When such a pulse waveform is used, the material is cooled sufficiently at τoff1 corresponding to the first pulse-off, and the plasma depleted in the processed portion is sufficiently performed. Therefore, τoff2 after processing τon1 is too long. No need. But,
Since the temperature rise of the material and the generation of plasma in the processed part cannot be ignored as the processing proceeds, τoff must be increased stepwise. Thereby, processing can be performed without reducing the processing efficiency of each τon. [0029] The in FIG. 1 (D) is and (E) further pulse waveform used in the pulse control method of the laser power according to the present invention
Shows another embodiment . This pulse waveform is
And Tauon (τon) control in FIG. 1 (B), the 1
(C) is combined with the tau-off (τoff) control, and the output of the second pulse on is kept constant as shown in the figure.
This time is gradually reduced while the second pulse off time is gradually increased. Further, FIG. 1E shows a case where the first pulse off time is also changed. That is, the lengths of τoff1 and τoff6 are changed. These cases are suitable for ultrafine processing. According to an experiment for confirming the effect of the pulse control method of the laser power supply according to the present invention, for example, when laser processing 6t of mild steel with the same average output, a processing speed approximately twice as high as that of laser processing using normal pulses is obtained. Was done. At the same time, even in fine processing of complex shapes, more stable processing can be performed at a higher processing speed than when using normal pulses, reducing running costs and applying to new fields of laser processing. Became possible. In the case of stainless steel, the area in which stable processing can be performed is approximately doubled, and the processing speed is approximately doubled. At the same time, the flow rate of the assist gas conventionally used can be reduced to about half, and the running cost can be further reduced. The present invention is not limited to the above-described embodiment, but can be embodied in other modes by making appropriate changes. For example, laser processing includes not only cutting processing by laser but also welding processing. As described above, the present invention provides a laser oscillator
Irradiates the workpiece with laser light from a single processing head
Laser processing systems that perform laser processing
A pulse-on signal that commands the high-frequency power supply to output the light
And pulse-off signal to command the high-frequency power supply to stop output
Using a high-frequency power supply control pulse train composed of
A method of controlling a laser power supply, comprising:
Whether the first pulse-on signal and the first pulse-off signal have a low wave number
And the first pulse-on signal has a high frequency.
From a plurality of second pulse-on signals and second pulse-off signals
The first pulse is compared with the time of the first pulse on signal.
When the off signal time is short and the first pulse off signal
The time of each second pulse-off signal is shorter than
And the output of the second pulse-on signal is kept constant.
The time is stepped within one first pulse-on signal.
And / or shorten the time of the second pulse off signal.
In the first pulse-on signal.
With this configuration , even when processing is performed with the same average output, the amount of heat input to the material is reduced as compared with the case where output is performed using a normal pulse. As a result, the processing speed can be increased, and stable processing can be performed with the processing speed increased. In addition, the amount of heat input can be easily controlled, and fine processing of a complicated shape can be stably performed at a high processing speed. Further, by increasing the processing speed, the usage amount of the assist gas is reduced, and the processing cost can be reduced. Further, the output of the second pulse-on signal is kept constant.
Keep that time within one first pulse-on signal
In the case where the configuration is such that the step length is shortened stepwise, the second pulse-on signal, that is, the command time of the laser output is shortened stepwise according to the progress of the processing. That is, since the first pulse-off time is long, the cooling of the material and the erasing plasma of the processing portion are sufficiently performed, and the first second pulse-on time that comes next can be long, so that high-speed processing is possible. . Thereafter, the influence of heat and plasma due to the second pulse on gradually accumulates as the processing progresses. Therefore, the amount of heat input to the material is limited by gradually shortening the second pulse on time. Therefore, high-speed and high-precision processing can be realized even in fine processing. The time of the second pulse-off signal is set to one
So that it gradually increases in the first pulse-on signal
In this case, the second pulse-off signal, that is, the command time for stopping the laser output, increases stepwise according to the progress of the processing. That is, since the first pulse-off time is long, the material is cooled sufficiently and the plasma in the processed portion is sufficiently removed, and heat and plasma are still accumulated in the material in the next processing using the second pulse-on time. Since there is no second pulse off time, the second pulse off time can be short. After that, the second pulse-off time gradually increases, so that the second pulse
The influence of heat or plasma due to pulse-on can be prevented from gradually accumulating, and high-speed and high-precision processing can be realized even in fine processing. Further, the output of the second pulse-on signal is kept constant.
And keep that time within one first pulse-on signal.
At the time of the second pulse off signal.
The interval is gradually increased within one first pulse-on signal.
In such a case, the amount of heat input to the material performed according to the progress of processing is more effectively restricted. Thereby, high-speed and high-precision processing can be realized even in fine processing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing various pulse trains used in a pulse control method for a laser power supply according to the present invention. FIG. 2 is a configuration diagram showing a laser processing system used in a laser power supply pulse control method according to the present invention. FIG. 3 is a block diagram showing one embodiment of a pulse train generating device used in the pulse control method of the laser power supply according to the present invention. FIG. 4 is a graph showing a rectangular pulse waveform conventionally used. [Description of Signs] 13 High-frequency power supply LB Laser light τon Pulse-on signal τoff Pulse-off signal

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Fuse 1-6-43, Kokubukita, Ebina-shi, Kanagawa (56) References JP-A-4-313476 (JP, A) JP-A-4-313475 (JP, A) JP-A-6-681 (JP, A) JP-A-1-254392 (JP, A) JP-A-2-205281 (JP, A) JP-A-1-278982 (JP, A) JP-A-7 JP-A-214348 (JP, A) JP-A-7-185851 (JP, A) JP-A-8-141758 (JP, A) JP-A-7-246482 (JP, A) JP-A-63-313681 (JP, A) JP-A-64-5686 (JP, A) JP-A-63-248585 (JP, A) JP-A-59-174288 (JP, A) JP-A-59-78793 (JP, A) JP-A 63-248793 207485 (JP, A) JP-A-63-207484 (JP, A) JP-A-56-160892 (JP, A) JP-A-63-224886 (J , A) JP Akira 59-92190 (JP, A) JitsuHiraku flat 1-139988 (JP, U) JitsuHiraku Akira 58-81084 (JP, U) (58 ) investigated the field (Int.Cl. ^7, DB Name) B23K 26/0-26/42 H01S 3/00-3/30 JICST file (JOIS) WPI (DIALOG)

Claims (1)

(57) [Claim 1] A laser beam from a laser oscillator is applied to a single
Laser that irradiates the workpiece from the machining head and performs laser processing
In a processing system, a method of controlling a laser power supply using a high-frequency power supply control pulse train including a pulse-on signal instructing a high-frequency power supply to output laser light and a pulse-off signal instructing the high-frequency power supply to stop output. The first pulse-on signal having a low frequency and the first pulse-on signal.
The first pulse-on signal is composed of a plurality of high-frequency second pulse-on signals and a second pulse-off signal, and the time of the first pulse-off signal is shorter than the time of the first pulse-on signal. and, the shorter the time for each one of said second pulse-off signal compared to the time of the first pulse-off signal, a first one that time <br/> keeping the output of the second pulse-on signal constant Stepwise shorter within the pulse-on signal
And / or increasing the time of the second pulse-off signal stepwise within one first pulse-on signal.