JP4493967B2 - CO2 laser processing method and laser processing apparatus - Google Patents

Description

The present invention relates to a CO ₂ laser processing method and a laser processing apparatus in which a pulsed laser is output by forming an RF electric field, and processing is performed by irradiating a processing portion with the output laser.

FIG. 4 is a schematic diagram of a CO ₂ laser oscillator.
An impedance matching network (not shown) is connected to the oscillator 1. The RF power source 6 is adjusted by the impedance matching network so that the output laser 4 satisfies the specifications. One of the pair of discharge electrodes 2 is connected to the RF power source 6 and the other is connected to the ground 7. A pair of resonator mirrors 3 is installed inside the oscillator 1 (Patent Document 1).

When an oscillation command 5 is input to the RF power source 6, power is supplied to the discharge electrode 2 installed inside the oscillator 1, and an RF electric field is formed between the discharge electrodes 2 by the supplied power. The mixed gas containing CO ₂ is electrically excited by this RF electric field, and plasma is formed between the discharge electrodes 2. A laser 4 is generated by a resonator mirror 3 arranged in a direction orthogonal to the discharge electrode 2 using this plasma as a gain medium.

Next, the pulse oscillation process will be described.
FIG. 5 is a diagram showing a waveform of a conventional laser 4, where the horizontal axis represents time and the vertical axis represents energy intensity.
While the oscillation command 5 is being input to the RF power source 6, an RF electric field is formed on the discharge electrode 2. Plasma is generated by this RF electric field, and after a certain time has elapsed (in the figure, about 10 μs after the oscillation command 5 is input), the output of the laser 4 starts, and the intensity of the laser 4 grows exponentially with time. When the oscillation command 5 is stopped, the RF electric field disappears, the intensity of the laser 4 falls exponentially with the gain relaxation, and then disappears.

6A and 6B are diagrams showing temporal changes in laser intensity, where FIG. 6A shows a state immediately after oscillation and FIG. 6B shows a state after 1 second of oscillation.
A CO ₂ laser oscillator (hereinafter referred to as “reference laser oscillator”) having a laser oscillation period of 1 kHz and a maximum duty of 10% was operated at an oscillation frequency of 1 kHz and a pulse width of 35 μs (that is, a duty of 3.5%). In this case, the peak intensities of 20 pulses immediately after oscillation and 1 second after oscillation are almost the same. (Note that the peak intensity after 1 second of oscillation is maintained thereafter as long as oscillation continues.)
U.S. Pat. No. 4,169,251

  By the way, the reference laser oscillator described above is a laser oscillator having a large peak intensity and a large pulse energy, and can process a large hole with high efficiency.

  However, the diameter of the hole to be processed is not only large but also small. In addition, it is desired to increase the processing speed.

FIG. 7 is a diagram showing a temporal change of a laser pulse by a conventional control method. Immediately after oscillation when a reference laser oscillator is operated with a pulse width of 35 μs and a laser oscillation period of 250 μs (duty 14%) (FIG. 7) It is a figure which shows the peak intensity of 20 pulses after (a)) and 1 second of oscillation (the figure (b)).
As shown in the figure, when the duty is increased beyond the specification of the laser oscillator, the intensity of the pulses after the third pulse immediately after the oscillation decreases rapidly, and after 1 second, it decreases to about 70% immediately after the oscillation. . Therefore, when drilling is performed under these conditions, the hole shape varies, and the processing quality deteriorates.

  Although explanation is omitted, when the laser oscillation frequency is set to be higher than the rated frequency (for example, 4 kHz) under the condition that the duty is below the specification by the reference laser oscillator, the peak intensity of the laser tends to decrease immediately after the oscillation. is there.

  In addition, when the laser oscillation frequency is higher than the rated frequency (for example, 4 kHz), the laser cannot oscillate continuously. For example, after oscillating several pulses of laser, a pause time of about 1 ms is required. It is necessary to provide it.

  In this way, when the laser oscillation frequency and duty are increased beyond the specifications, not only the variation in the peak intensity of the laser pulse increases, but also the processing efficiency cannot be improved. The maximum rating available.

  As a means for suppressing the change in peak intensity, for example, impedance matching may be performed under the conditions of an oscillation period of 250 μs and a duty of 14%. However, in the laser processing apparatus, it is necessary to change the laser irradiation period and pulse width depending on the processing pattern and the type of workpiece. Therefore, it is not practical to perform impedance matching that requires time for each processing.

  The object of the present invention is to improve the processing quality by reducing the variation in the peak intensity of the laser during processing even when the rating of the laser oscillator is the same, and to increase the laser oscillation frequency (for example, 4 kHz). However, the present invention is to provide a laser processing method and a laser processing apparatus capable of improving the processing efficiency by continuously oscillating a laser.

In order to achieve the above object, the invention of claim 1 is characterized in that an RF electric field is formed by the discharge electrode by an RF power source connected to the discharge electrode of a laser oscillator, thereby outputting a pulsed laser, and the laser In the CO2 laser processing method in which processing is performed by irradiating the processing portion, the RF electric field is formed in one on / off cycle in which the ON period and the OFF period of the RF power source are equal, and 1 of the RF power source is formed. One pulse-shaped laser is output by repeating the formation of the RF electric field with an on / off period in which the laser does not oscillate during the on-period.

The invention of claim 2 is characterized in that, in claim 1, the on period is 1 μs and the off period is 1 μs .

According to a third aspect of the present invention, an RF electric field is formed by the discharge electrode by an RF power source connected to the discharge electrode of the laser oscillator so that a pulsed laser is output, and the laser beam is irradiated to the processing portion. in CO2 laser processing apparatus that performs processing Te, thereby forming the RF field and the on period and the off period of the RF power source in a single on-off period equal to the laser at one of the on period of the RF power supply One pulsed laser is output by repeating the formation of the RF electric field with an on / off period in which the laser does not oscillate.

Since the variation in the peak intensity of the laser can be reduced, the processing quality can be improved.
Further, since the laser oscillation frequency can be increased, the processing efficiency can be improved.

Hereinafter, the present invention will be described based on the illustrated embodiments.
In the present invention, an RF electric field is intermittently formed to output one laser.

  FIG. 1 is a diagram showing a temporal change of a laser according to the present invention, in which a reference laser oscillator is operated with a pulse width of 35 μs and a laser oscillation period of 250 μs (duty 14%). The horizontal axis represents time, and the vertical axis represents energy intensity. Further, an RF electric field is formed with a period of 2 μs (the RF power supply 6 has an on time of 1 μs and an off time of 1 μs) in order to output one laser.

  In the case shown, the pulse energy of the laser is reduced by about 25% compared to the conventional case indicated by the dotted line.

2A and 2B are diagrams showing temporal changes in the peak intensity of the laser according to the present invention. FIG. 2A shows a state immediately after oscillation, and FIG. 2B shows one second after the start of oscillation.
As shown in the figure, according to the present invention, the peak intensity one second after the start of oscillation is about 90% immediately after the oscillation. Therefore, a large difference does not occur in the machining shape. That is, according to the present invention, when the pulse energy of the laser may be small, it is possible to perform processing by quadrupling the laser oscillation frequency, and the processing efficiency can be quadrupled compared to the conventional one. In addition, the variation in machining shape is small.

  Note that, as shown in FIG. 3A, the RF electric field can be formed when a pulse is generated by repeating the on-time 13 and off-time 14 with the on-time 13 and off-time 14 of the RF power source 6 as one set. It is good to combine several types of on-time 13 and off-time 14, for example, as shown in FIG. 5B, an RF electric field is continuously formed until the pulse rises, and the RF electric field is changed after the pulse rises. You may make it form intermittently.

  In the inventor's test, the switching shown in (a) compared with (b) was able to align the peak intensity of the entire pulse train.

  When a large pulse energy is required, a conventional RF electric field forming method, that is, an RF electric field may be continuously formed during laser output.

  Further, according to the present invention, as shown in FIG. 3C, the magnitude of the pulse energy is obtained by changing the combination of the on time 13 and the off time 14 of the RF power source 6 when outputting one laser. Therefore, machining quality can be improved.

  The peak intensity can be made constant by intermittently forming the RF electric field because the efficiency of absorbing energy supplied from the RF electric field of the plasma generated between the RF electric fields is related to the magnitude of the duty. It is estimated that this is because it is almost constant.

  In addition, when processing the hole of the same shape, when it was made to form RF electric field intermittently, it has confirmed that energy consumption could be made small compared with the case where RF electric field was formed continuously.

It is a figure which shows the time change of the laser which concerns on this invention. It is a figure which shows the time change of the peak intensity of the laser by this invention. It is a figure which shows the on-off control method of RF electric field which concerns on this invention. It is a schematic diagram of a CO ₂ laser oscillator. It is a figure which shows the waveform of the conventional laser. It is a figure which shows the time change of the conventional laser intensity. It is a figure which shows the time change of the laser pulse by the conventional control method.

Explanation of symbols

1 RF power supply 4 Laser

Claims (3)

A CO2 laser in which an RF electric field is generated at the discharge electrode by an RF power source connected to the discharge electrode of a laser oscillator, thereby outputting a pulsed laser and irradiating the laser beam onto the processing portion. In the processing method,
The RF electric field is formed in one on / off cycle in which the on period and the off period of the RF power source are equal, and the RF electric field is formed in an on / off cycle in which the laser does not oscillate in one on period of the RF power source. A CO2 laser processing method characterized by outputting one pulsed laser by repeating the above.   The CO2 laser processing method according to claim 1, wherein the on period is 1 μs and the off period is 1 μs. A CO2 laser in which an RF electric field is generated by the discharge electrode by an RF power source connected to a discharge electrode of a laser oscillator so that a pulsed laser is output and the laser beam is irradiated to the processing portion. In processing equipment,
And forming said RF field and the on period and the off period of the RF power source in a single on-off period equal, the laser forms the RF field in OFF period does not oscillate in one ON period of the RF power supply A CO2 laser processing apparatus that outputs one pulsed laser by repeating the above.

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