JPS5819395B2 - Laser processing method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser processing method and apparatus for processing various materials using a high-power pulsed laser.

A conventional laser processing apparatus is constructed as shown in FIG.

That is, the laser beam 2 emitted from the laser oscillator 1 is directed to the mirror 3.
After being reflected by the condenser lens 4, the condensing lens 4 condenses the condensed light to process the workpiece 6 placed near its focal point.

In this case, a pulsed laser with a high peak output, such as a Nd Niglass laser, a ruby laser, a TEA-CO2 laser,
When using an N2 laser, the power density near the focal point 6 may exceed 109Watt/crIL;
If processing is performed in air, the air near the focal point will ionize due to the high burr density and generate plasma.

This plasma is generally opaque to the laser light and absorbs most of it.

Therefore, Nd Niglass laser. Ruby laser, TEA
-CO2 laser light is not effectively used for processing.

For example, the TEA-CO2 laser has a wavelength of 10.6 μ, but the plasma generated by this is 7
Absorbs more than 0%.

This characteristic is shown in FIG.

In FIG. 2, the horizontal axis represents the energy of the TEA-CO2 laser pulse, and the horizontal axis represents the ratio of energy before and after the focused focal point (transmittance).

At low pulse energy when plasma is not generated, the transmittance is 100%, but when plasma is generated, this decreases to 30%.
It can be seen that the value decreases to below.

Next, FIG. 3 shows the relationship between the removal amount and pulse energy when drilling a hole in metal using this laser.

As shown here, when no plasma is generated, the removal amount increases with pulse energy from A to B, but
When plasma is generated, the energy used for machining decreases due to its energy absorption, so even if it drops to a certain point and the pulse energy increases after that, it will only increase like DE with a gentler slope than AB. .

The depth of the machined hole obtained when no plasma is generated with the pulse energy of E is C above E on the extension of AB, but the E actually obtained is only a fraction of this.

As mentioned above, the generation of plasma and the resulting absorption of laser light significantly reduce processing efficiency.

In Fig. 3. Although only the removal amount has been discussed, it goes without saying that exactly the same situation exists regarding the machining diameter, the machining hole depth, etc.

To solve this problem, there is a method to increase processing efficiency by creating a vacuum near the workpiece to prevent plasma generation, but this requires a vacuum chamber vacuum pump for this purpose, and it also requires evacuation and evacuation during work. This was unreasonable in terms of manufacturing because it added work such as air return, making it a complicated and inconvenient process.

The purpose of this invention is to eliminate the drawbacks of the above-mentioned conventional technology, eliminate the absorption of laser light by plasma generated during processing with a high-power laser, and improve the processing efficiency and the processing amount and processing depth without creating a vacuum near the workpiece. Another object of the present invention is to provide a laser processing method and apparatus for increasing the processing width.

That is, in the present invention, the energy of the pulsed laser beam is 125
Focusing on the fact that plasma emission due to gas ionization is prevented at mJoule or less, when high-power pulsed laser light of 200mJoule or more is output from a laser oscillator, this high-power pulsed laser light has 125mJoule.
This method is characterized in that it is divided into a plurality of pulsed laser beams of e or less, and each of the pulsed laser beams is simultaneously focused and irradiated onto different parts of the workpiece to process it.

The present invention will be specifically described below based on embodiments shown in the drawings.

In FIG. 3, the lowest pulse energy generated by the plasma is 125 mJoule.

This produces plasma when the dog is pulsed with energy.

This causes absorption of laser light.

If the pulse energy is smaller than this, no plasma will be generated and no absorption of laser light will occur.

Now, the maximum pulse energy that this laser can emit is 35
Assuming 0 mJoule, if this is irradiated as is, only a hole with a removal amount of <0.23 μg will be obtained as shown at point E.

Therefore, this laser beam is divided into several parts so that the pulse energy of each laser beam is 125 mJoule or less.

For example, if we divide a beam with a pulse energy of 350 mJoule into three beams, each with a pulse energy of 116.7 mJoule, and irradiate each part of the workpiece through a condenser lens, the energy of each beam will be Since it is smaller than 125 m Joule, no plasma is generated.

Therefore, the removal amount by each beam is 116.7 m in Figure 3.
0.22 μg corresponding to Joule is obtained.

Therefore, the total removal amount is 0.66 μg, which is three times this amount, which is much larger than the removal amount of 0.23 μg when the beam is not split.

In this way, the laser beam was split into several parts, and each beam was processed at a different point on the object so that the energy of each beam was at a level that did not generate plasma, so the beam was not split. The total removal amount can be greatly increased compared to the case where the processing efficiency can be greatly increased.

First, an embodiment of a method of dividing a laser beam into several beams, which is the most important in carrying out the present invention, will be explained in detail with reference to FIG.

That is, a semi-transparent mirror 12. The semi-transmissive mirror 13 is a semi-transmissive mirror having a reflectance of 33.3% and 50%, respectively, with respect to the laser beam, and the reflecting mirror 14 is a total reflective mirror.

Laser beam 2 emitted from laser oscillator 1 passes through semi-transparent mirror 12
33.3% of the laser beam is reflected as a laser beam 9.

The remaining 66.7% passes through the semi-transmissive mirror 12 and becomes the laser beam 7, and 50% of this, that is, 33.3% of the original laser beam 2, is reflected by the mirror 13 and becomes the laser beam 10. .

Furthermore, 50% of the laser beam 7, that is, 33.3% of the original laser beam 2, passes through the semi-transmissive mirror 13 to become the laser beam 8, and is totally reflected by the reflecting mirror 14 to become the laser beam 11.

Therefore, the output laser beam 2 of the laser oscillator 1 is divided into three laser beams 9 and 10 degrees 11, each having an intensity 1/3 of the original beam.

Although there are three mirrors in this example, it is clear that it is possible to use other numbers of mirrors to split the beam.

Furthermore, the divided laser beams do not necessarily have to have equal intensities.

FIG. 5 is a diagram showing another embodiment of the method of dividing the laser beam.

In this figure, the mirror 15 placed with respect to the laser beam 2 consists of three parts: small mirrors 15a, 15b, and 15c.The small mirrors 15a, 15b, and 15c are each plane mirrors, and their inclinations are slightly different. A portion of the laser beam 2 that is incident on the mirror 15a is reflected and becomes a laser beam 9, and the portion of the laser beam 2 that enters the mirror 15a is reflected.
The portion incident on the mirror 15c is reflected and becomes the laser beam 10, and the portion incident on the mirror 15c is reflected and becomes the laser beam 11.

In this way, the laser beam 2 becomes the laser beam 9, 10
．． It is divided into 11 parts.

In this case, if the small mirrors 15a, 15b, and 15c are arranged and set in consideration of the cross-sectional intensity distribution of the laser beam 2,
Each of the beams 9, 10, 11 can be made to have an appropriate intensity.

Although a mirror is used in this example, it is clear that the same effect can be achieved using a polygonal prism.

Next, an embodiment of a method of performing processing using the laser beam divided in this manner will be described.

The laser beams divided as described above are each focused by a lens and irradiated onto an object to be processed, but in this case, it is not possible to irradiate exactly the same location.

This is because if simultaneously split laser beams are focused on the same spot, the power density at that point will be the sum of the burr densities of each beam, which may exceed the power density required for plasma generation.

Since plasma will be generated, there is no point in dividing the beam into many parts.

Therefore, in order to prevent the generation of plasma, the diameter of the focused spot of the laser beam (several μ to several 1
It is necessary to perform simultaneous irradiation at a distance of 00μ) or more.

Taking these characteristics into consideration, the following processing methods can be considered.

In other words, when the amount of removal is a problem, such as when balancing a rotating body using a laser, and it does not matter if there is some error in the irradiation position on the order of the diameter of the laser condensed spot, the divided laser beam as shown in Figure 6 is used. 9.10.11 is changed in direction with a mirror or the like and made incident on the condensing lenses 16, 17, 18 to produce slightly different outer peripheral positions 19, 20, 21 on the rotating body 19 rotating around the axis 20 to be processed. Processing is performed by focusing the light on the

That is, it is assumed that the focused spots 19, 20, and 21 are separated from each other by a distance approximately equal to the diameter of the focused spots.

When balancing a rotating body using a laser, it is necessary to remove as much computation as possible in one irradiation, and with this method, the amount removed in one irradiation increases compared to when the beam is not divided. can.

In addition, when processing a large number of samples at the same time, in production processing, a large number of workpieces are processed one after another, but in this case, 1
After completing the processing of the first sample, the next processing begins.

Although the line processing method does not have the effect of beam splitting, it simultaneously processes as many samples as the number of split beams in parallel.

Using a batch processing method can significantly reduce the overall processing time.

This is shown in FIG.

In FIG. 7, laser beams 9, 10, 11 obtained by dividing the output beam of the same laser oscillator are incident on condensing lenses 16, 17, 18, respectively, to workpieces 21, 22,
23 are processed at the same time.

In this way, the same effective energy that can be obtained when machining one workpiece without splitting the beam can be obtained at three machining points without generating plasma, reducing the total machining time. It will be about one-third.

In addition, when machining multiple locations on one sample at the same time, there is a case where three locations on one workpiece 24 are simultaneously processed using divided beams as shown in FIG.

This is almost the same as the case shown in FIG. 7, and no explanation is required.

In addition, when processing the front and back sides of one sample at the same time, the 9th
As shown in the figure, there is a method in which the beam is divided into two parts so that the beam has energy smaller than that required for plasma generation, and the same part of one sample 25, for example, a thin plate, is processed simultaneously from the front side and the back side.

Such a method increases processing efficiency in processing through the sample.

It is also obvious that the method of FIG. 7 and the method of FIG. 9, and the method of FIG. 8 and the method of FIG. 9 may be used in combination.

Further, a case where linear continuous processing such as cutting, scribing, etc. is performed is shown in FIG. 10.

That is, the laser beam emitted from the same laser source is divided into laser beams 9 and 10.

Each beam 9゜10 is condensed by a condenser lens 16.17 and focused on a point 26゜27 without generating plasma, 77
0 workpiece 28 is processed.

Now, when the table holding the workpiece 28 is moved in the direction parallel to the straight line connecting the points 26 and 27 (in the direction of the arrow), the workpiece 28 will first be machined by the spot 26 to form a Loe groove 29, and then the same groove will be formed. is machined using spot 27 to form machined groove 3.
Set to 0.

In this way, a single groove is processed twice in the absence of plasma, thereby achieving a faster processing speed.

It is clear that the same thing holds true when the workpiece is moved in two directions and the laser beam is scanned over the workpiece to perform simple machining of the workpiece.

As explained above, according to the present invention, absorption of laser light by plasma is eliminated using high-power lasers such as Nd glass laser, ruby laser, N2 laser, TEA-CO□ laser, etc. This has the effect of enabling machining with large effective power.

Therefore, according to the present invention, since processing is carried out in the air, special equipment and work for vacuum desorption are not required, so it is possible to significantly reduce processing time and to reduce the amount of removal, which was difficult in the past. Large machining can be easily achieved.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram showing an apparatus for implementing a conventional laser processing method, and Figure 2 shows the relationship between the transmittance of CO2 laser light and the laser pulse energy for plasma generated by conventional TEA-C02 laser processing. 3 is a diagram showing the relationship between the pulse energy of the TEA-CO2 laser shown in FIG. 2 and the removal amount during processing, and FIG. 4 is a diagram showing one of the pulsed laser beam splitting devices according to the present invention. FIG. 5 is a schematic configuration diagram showing another embodiment of the pulsed laser beam splitting device according to the present invention, and FIG. 6 is a schematic diagram showing another embodiment of the pulsed laser beam splitting device according to the present invention. 7 is a schematic configuration diagram showing a case in which the pulsed laser beam divided by the device is applied to the rotating body to balance the rotating body.
The figure shows a state in which a large number of workpieces are irradiated with pulsed laser light divided by the apparatus shown in Fig. 4 or 5, and each workpiece is processed simultaneously. Figure 9 is a diagram showing a state in which a pulsed laser beam divided by the apparatus shown in Figure 4 or Figure 5 is irradiated to multiple locations on one workpiece and each location is processed simultaneously. Figure 10 is a diagram showing a state in which pulsed laser light divided by the apparatus shown in Figures 4 and 5 is irradiated to the same location on the front and back of the workpiece, and each location is processed simultaneously. Irradiating two locations on the same line of the workpiece with a pulsed laser beam divided by the device shown in FIG. 5, and
FIG. 3 is a diagram illustrating a case where a workpiece is moved in a straight line to perform continuous linear processing such as cutting. 1... Laser oscillator, 12, 13...
Semi-transparent mirror, 14...Reflecting bell, 15...
Mirror, 15a, 15b. 15c...Small mirror, 9,1011...
・Laser beam, 16, 17, 18... Condensing lens, 19... Rotating body, 21, 22, 23, 2
4,25°28...Workpiece.

Claims (1)

[Claims] 1. In a method of focusing a high-power pulsed laser beam and processing an object placed at the focusing point, even if the high-power pulsed laser beam is focused, plasma due to ionization of the gas is generated. A laser processing method characterized by dividing a pulsed laser beam into a plurality of pulsed laser beams with energy that does not generate energy, and simultaneously focusing each pulsed laser beam and irradiating different parts of a workpiece to process it. 2. In the laser processing method according to claim 1, the output of the high-power pulsed laser beam is 200 mtJ.
A laser processing system characterized in that the output of each of a plurality of pulsed laser beams divided into 125 mJoule or more is 125 mJoule or less.3 A laser oscillator that oscillates a high-output pulsed laser beam, and A semi-transmitting mirror that reflects a part of the output high-power pulsed laser beam and transmits the other part, a reflecting mirror that reflects the pulsed laser beam that passes through the semi-transmitting mirror, and the semi-transmitting mirror a condenser lens that focuses the reflected pulsed laser beam on a predetermined location on the workpiece; and a condenser lens that focuses the pulsed laser beam reflected from the reflecting mirror on a location different from the predetermined location on the workpiece. Equipped with a condensing lens 1. A laser processing device characterized by being able to simultaneously process different parts of a workpiece without emitting plasma. 4 a laser oscillator that oscillates a high-power pulsed laser beam; an optical means that reflects or refracts the high-power pulsed laser beam output from the laser oscillator in a plurality of mutually different directions and divides it into a plurality of pulsed laser beams;
It is equipped with a plurality of condenser lenses that focus each of the pulsed laser beams split by the optical means on different parts of the workpiece, and processes different parts of the workpiece at the same time without emitting plasma. A laser processing device characterized by: