JP6895621B2 - Laser processing head and laser processing equipment - Google Patents

Description

The present invention relates to a laser processing head used for laser processing an object to be processed and a laser processing apparatus including the laser processing head, and more particularly to an improvement of a condenser lens of the laser processing head.

The laser light oscillated by the laser oscillator has excellent monochromaticity and directivity, and is coherent, so it is used for various industrial processing such as cutting, drilling, welding, surface treatment, and marking. ing.

A conventional laser processing apparatus and a laser processing head will be described with reference to FIG. FIG. 5 is a perspective view schematically showing the configuration of the laser processing apparatus. In the figure, members having the same configuration and function are designated by the same reference numerals.

The laser machining apparatus 2000 includes a laser oscillator 2100 that emits a laser beam LB, a process fiber 2300 that guides the laser beam LB, and a laser machining head 2400 that irradiates the laser beam LB toward a machining object (work W). , Equipped with.

The laser machining head 2400 includes a collimator lens 2410 and a condenser lens 2420. The laser beam LB that has reached the laser processing head 2400 is incident on the condenser lens 2420 (for example, an achromat lens) via the collimator lens 2410, and is irradiated to the work W in a state where the density is increased. The work W is fixed on the processing table 2500. On the other hand, the laser machining head 2400 can be moved by the X-axis motor 2710 and the Y-axis motor 2720, and predetermined machining is performed while moving the laser machining head 2400 relative to the work W. The laser oscillator 2100, the X-axis motor 2710, and the Y-axis motor 2720 are controlled by the machining control unit 2600, and the state thereof is synchronized with the machining control unit 2600.

In order to perform laser machining with high processing accuracy and productivity, not only the density of the laser beam LB but also the focused beam profile of the laser beam LB irradiated to the work W is important. The focused beam profile is a locus drawn when the laser beam LB focused by the focusing lens emits light from the focusing lens. For example, the depth of focus DF of the laser beam LB and the minimum beam diameter DW can be obtained. It is represented (see FIGS. 2A-2C, FIG. 6). The focused beam profile changes according to, for example, the optical properties of the focusing lens 2420 arranged on the laser processing head 2400.

Patent Documents 1 and 2 teach a method of increasing the depth of focus DF by condensing a laser beam having a plurality of wavelengths with a condensing lens so that a plurality of focal points are formed. FIG. 6 schematically shows a focused beam profile formed by the method of Patent Document 1. In Patent Document 1, a plurality of focal points are formed by condensing a plurality of laser beams LB having different wavelengths with a single condensing lens 2421.

Japanese Unexamined Patent Publication No. 2001-321978 JP-A-2010-158686

FIG. 7 shows a graph showing the relationship between the thickness of the work W and the cutting speed when the work W (stainless steel plate) is cut using three types of laser beams LB having different depths of focus. The laser beam LB is emitted from a laser oscillator having an output of 4 kW, and its depth of focus DF is 3 mm, 6 mm, and 9 mm, respectively.

As can be seen from this graph, the cutting speed is affected by the depth of focus of the laser beam LB and the thickness of the work W. For example, when the thickness of the work W is less than 2 mm, when the laser beam LB having a depth of focus of 3 mm is used, the cutting speed becomes faster as compared with the laser beam LB having another depth of focus. When the thickness of the work W is about 2 to 8 mm, when the laser beam LB having a depth of focus of 6 mm is used, the cutting speed becomes faster as compared with the laser beam LB having another depth of focus. When the thickness of the work W exceeds 8 mm, the cutting speed becomes faster when the laser beam LB having a depth of focus of 9 mm is used as compared with the laser beam LB having another depth of focus. Even when cutting mild steel having a plate thickness of 16 mm or more, if a laser beam LB having a depth of focus of 9 mm is used, the cutting speed becomes high. The depth of focus is a range in which the beam diameters are considered to be optically the same, and specifically, is a range (Rayleigh's range) until the beam diameter is expanded to a diameter of 2√2 times the beam radius. ..

In general, the depth of focus DF increases as the minimum beam diameter of the laser beam LB (hereinafter, beam waist diameter DW) increases. That is, the beam waist diameter DW of the laser beam LB having a depth of focus of 9 mm is larger than the beam waist diameter DW of the other laser beam LB. The cutting process by the laser beam LB is performed while injecting a high-pressure gas onto a part (dross) of the molten work W and blowing the dross from the cut portion. Therefore, in the above case, the cutting speed is the fastest when the laser beam LB having a large beam waist diameter DW (that is, a wider cutting width) and a depth of focus of 9 mm is used. Even in laser processing other than cutting processing such as welding, the appropriate depth of focus differs depending on the material of the work W and the like.

However, in the conventional laser processing apparatus, the depth of focus (that is, the focused beam profile) of the laser beam LB cannot be changed according to the work W or the processing conditions. Therefore, the processing accuracy and productivity are likely to decrease, and the quality of the workpiece to be processed is also likely to decrease.

One aspect of the present invention is an incident port into which a laser beam having a plurality of wavelengths is incident, a first condensing lens that condenses the laser beam, and the laser beam condensed by the first condensing lens. Laser processing including a second condensing lens that further condenses light, and a position adjusting mechanism that moves at least one of the first condensing lens and the second condensing lens along the traveling direction of the laser beam. The head.

Another aspect of the present invention is a laser processing apparatus including a laser oscillator that emits a laser beam having a plurality of wavelengths and the laser processing head that the laser beam is incident on.

According to the laser processing head of the present invention, it is possible to irradiate a laser beam having an optimum focused beam profile according to various workpieces. Therefore, if a laser processing apparatus equipped with this is used, laser processing having excellent processing accuracy and productivity becomes possible, and a high-quality laser processed product can be obtained.

It is sectional drawing which shows typically the structure of the laser processing head which concerns on this invention. It is a schematic diagram which shows the positional relationship of two condensing lenses, and the condensing beam profile of the laser beam LB focused by this. It is a schematic diagram which shows the other positional relationship of two condensing lenses, and the condensing beam profile of the laser beam LB focused by this. It is a schematic diagram which shows the other positional relationship of two condensing lenses, and the condensing beam profile of the laser beam LB condensed by this. It is a graph which shows the relationship between the distance D between two condensing lenses and the depth of focus DF. It is a perspective view which shows typically the structure of the laser processing apparatus which concerns on this invention. It is a perspective view which shows typically the structure of the conventional laser processing apparatus. It is a schematic diagram which shows the condensed beam profile of the laser beam focused by one condenser lens. It is a graph which shows the relationship between the thickness of a work and cutting speed.

The refractive index of the laser beam LB due to the condenser lens differs depending on the wavelength. Therefore, when the laser beam LB containing a plurality of wavelengths is focused by a condenser lens, it is dispersed and chromatic aberration is generated. The focused beam profile changes depending on the degree of chromatic aberration. The laser processing head of the present embodiment uses this chromatic aberration to change the focused beam profile to generate a laser beam LB corresponding to various laser processing conditions.

Specifically, a plurality of condensing lenses are arranged on the laser processing head, and the condensing beam profile of the laser beam LB is appropriately changed by changing the distance between them. As a result, the work W can be irradiated with a laser beam LB having a depth of focus according to the processing content, the thickness and material of the work W, the processing shape, and the like. This embodiment is particularly suitable for laser processing using a laser beam LB having a plurality of wavelengths over a wide wavelength range.

Hereinafter, the present embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 is a cross-sectional view schematically showing the configuration of the laser processing head of the present embodiment. 2A to 2C are schematic views showing the positional relationship between the two focusing lenses and the focused beam profile of the laser beam focused thereby. FIG. 3 is a graph showing the relationship between the distance D between the two condenser lenses and the depth of focus DF. FIG. 4 is a perspective view schematically showing the configuration of the laser processing apparatus according to the present embodiment. In the figure, members having the same configuration and function are designated by the same reference numerals.

(Laser processing head)
The laser processing head 400 further includes an incident port 440 on which the laser beam LB is incident, a first condensing lens 421 that condenses the incident laser beam LB, and a laser beam LB focused by the first condensing lens 421. A second condensing lens 422 that condenses light and a position adjusting mechanism 430 are provided. The laser beam LB incident on the incident port 440 has a plurality of wavelengths. The position adjusting mechanism 430 moves at least one of the first condensing lens 421 and the second condensing lens 422 along the traveling direction of the laser beam LB.

The laser processing head 400 may further include a collimator lens 410. As shown in FIG. 4, the laser beam LB propagates inside the process fiber 300 after being emitted from the laser oscillator 100 and reaches the laser processing head 400. The laser beam LB that has reached the laser processing head 400 passes through the collimator lens 410, is increased in density by the first condensing lens 421 and the second condensing lens 422, and is irradiated on the work W.

The work W is fixed on the processing table 500. On the other hand, the laser machining head 400 can be moved by the X-axis motor 710 and the Y-axis motor 720, and predetermined machining is performed while moving the laser machining head 400 relative to the work W. The laser oscillator 100, the X-axis motor 710, and the Y-axis motor 720 are controlled by the machining control unit 600, and the state thereof is synchronized with the machining control unit 600.

At least one of the first condensing lens 421 and the second condensing lens 422 is movable, and the distance D between the two can be changed. In the illustrated example, both the first condensing lens 421 and the second condensing lens 422 are movable along the traveling direction of the laser beam LB by the position adjusting mechanism 430 (431, 432). In this case, the distance D between the first condensing lens 421 and the second condensing lens 422 and the distance between the collimator lens 410 and the first condensing lens 421 can be changed.

As shown in FIG. 2A, a state in which at least a part of the first condensing lens 421 and the second condensing lens 422 are in contact (distance D = 0) is defined as a reference position D ₀ . This has the same configuration as an achromatic lens commonly used in optical systems. When an achromatic lens is used, the focal point of the laser beam LB is converged to almost one point. That is, when the first condensing lens 421 and the second condensing lens 422 are at the reference position D ₀ , the chromatic aberration of the laser beam LB is the smallest, and the _{depth of focus DF 0 is the minimum.} Therefore, a high-density laser beam LB can be obtained. This laser beam LB is suitable for cutting a thin work W, for example.

When the first condensing lens 421 and / or the second condensing lens 422 is _{moved from the reference position D 0} to increase the distance D between the condensing lenses, the condensing beam profile of the laser beam LB changes. For example, as shown in FIGS. 2B and 2C, a laser beam LB having a larger beam waist diameter DW can be obtained. When the distance between the condensing lenses in FIG. 2B is the distance D ₁ and the distance between the condensing lenses in FIG. 2C is the distance D ₂ and the distance D ₁ <D ₂ , the respective depths of focus are DF ₁ <DF. ₂ and each beam waist diameter becomes DW ₁ <DW ₂ . That is, as the distance D between the lenses increases, the depth of focus DF and the beam waist diameter DW also increase. The laser beam LB of FIG. 2C, which has the largest beam waist diameter DW, is suitable for cutting a thicker workpiece, for example.

A graph showing an example of the relationship between the distance D between the condenser lenses and the depth of focus DF is shown in FIG. Here, the laser beam LB is irradiated from the laser processing head 400 of the laser processing apparatus 1000 shown in FIG. The laser beam LB is propagated to the laser processing head 400 via the process fiber 300 having a core diameter of 100 μm. The laser beam LB has a plurality of wavelengths in the wavelength range of 950 nm to 1000 nm. Focal length of the collimator lens 410 is 100 mm, the condensing lens 420 (first condensing lens 421 and the second condenser lens 422 in the reference position _{D 0} is in contact with at least a portion, is regarded as one of the condenser lens The focal length of the lens) is 150 mm.

In FIG. 3, when the distance D between the condenser lenses is 0 mm, the depth of focus DF is about 3 mm. The imaging ratio is 1.5 times, and the beam waist diameter is 150 μm. The imaging ratio in this case is emitted from the condenser lens 420 via the collimator lens 410 with respect to the beam diameter of the laser beam LB incident on the collimator lens 410 (specifically, the core diameter of the process fiber 300 is 100 μm). It is a ratio of the beam waist diameter DW of the laser beam LB. The image formation ratio changes depending on the distance D between the condenser lenses. When the distance D between the condensing lenses is 4 mm, the depth of focus DF is about 6 mm, and when the distance D between the condensing lenses is 8 mm, the depth of focus DF is about 9 mm.

The position adjusting mechanism 430 is not particularly limited, and a known mechanism used for positioning may be used. Examples of the position adjusting mechanism 430 include a servomotor and the like. The position adjusting mechanism 430 only needs to be able to move at least one of the condenser lenses 420 arranged on the laser processing head 400.

A condenser lens 420 other than the first condenser lens 421 and the second condenser lens 422 may be arranged on the laser processing head 400. In this case, the focused beam profile may be controlled by appropriately adjusting the distance between the focusing lenses 420.

The shape of the condenser lens 420 is also not particularly limited. As shown in the illustrated example, a biconvex lens (first condensing lens 421) having two convex surfaces and a concave meniscus lens (second condensing lens 422) may be arranged in combination, or other lenses. May be combined. The condenser lens 420 includes, in addition to the above-mentioned biconvex lens and concave meniscus lens, a plano-convex lens having a convex surface and a flat surface, a convex meniscus lens having a convex surface and a concave surface, and a convex meniscus lens having a thicker center than the peripheral edge. Examples thereof include a biconcave lens provided, a plano-concave lens having a concave surface and a flat surface, and the like. These are used in appropriate combinations of two or more depending on the desired focused beam profile.

(Laser processing equipment)
As shown in FIG. 4, the laser machining apparatus 1000 according to the present embodiment includes a laser oscillator 100 that emits a laser beam LB and a laser machining head 400 that is incident with a laser beam LB emitted from the laser oscillator 100. Be prepared. The laser beam LB is irradiated from the laser processing head 400 toward the work W. The laser beam LB emitted from the laser oscillator 100 may be guided by the process fiber 300 and incident on the laser processing head 400. The laser oscillator 100 emits a laser beam LB having a plurality of wavelengths (usually from the visible light region to the near infrared region) capable of propagating in the process fiber 300.

When the work W is cut or drilled by the laser machining apparatus 1000 (hereinafter collectively referred to as laser cutting), the laser machining head 400 is provided with a high-pressure gas (high-pressure oxygen, nitrogen, etc.) coaxially with the laser beam LB on the work W. A gas hole for blowing air) and a gas path for supplying high-pressure gas to the gas hole are arranged (neither is shown). In laser cutting, the work W is cut or drilled while removing a part of the work W melted by the laser beam LB with a high-pressure gas.

When two or more workpieces W are welded by the laser processing apparatus 1000 (laser welding), the laser processing head 400 has a gas hole for blowing an inert gas (argon, helium, etc.) onto the workpiece W at a low pressure, and the gas. A gas path for supplying an inert gas is arranged in the pores (neither is shown). The workpieces W are welded to each other while suppressing the oxidation of the workpieces W melted by the laser beam LB with an inert gas. When the work W is surface-treated by the laser processing apparatus 1000, the work W is irradiated with the laser beam LB while spraying, for example, an inert gas, in the same manner as described above. When marking the work W with the laser processing apparatus 1000, the work W is irradiated with the laser beam LB while blowing a gas corresponding to a desired color.

As described above, if the number and shape of the condensing lenses arranged on the laser processing head 400 and the core diameter of the process fiber 300 are determined, the depth of focus DF is calculated according to the distance D between the condensing lenses. Therefore, the depth of focus DF corresponding to the thickness of the work W and the corresponding distance D may be stored in a storage device (not shown). At this time, the position control unit 800 that controls the position adjustment mechanism 430 is arranged in the laser processing device 1000. The position control unit 800 sets at least one of the first condensing lens 421 and the second condensing lens 422 in the traveling direction of the laser beam LB so as to satisfy the distance D corresponding to the depth of focus DF set according to the work W. The position adjusting mechanism 430 is controlled so as to move along the above. As a result, during laser processing, for example, by inputting a desired depth of focus DF to an input unit (not shown) connected to the position control unit 800, the depth of focus DF and the distance D stored in the storage device can be obtained. The distance D is set based on the relationship of the above, and the first condensing lens 421 and / or the second condensing lens 422 automatically move so as to satisfy this distance D. This system further improves productivity.

The laser oscillation mechanism of the laser oscillator 100 is not particularly limited, and in addition to a semiconductor laser that uses a semiconductor as a medium for laser oscillation, a _{gas laser that uses a gas such as carbon dioxide (CO 2} ) as a medium, a solid-state laser that uses YAG or the like, and a solid-state laser. , Fiber laser and the like. These may be used alone or in combination of two or more. Among them, a semiconductor laser is preferable because it is excellent in light quality and oscillation efficiency.

Due to its characteristics, the semiconductor laser emits a laser beam LB in which a plurality of laser beams are combined. The difference in wavelength between these plurality of laser beams is relatively large, and the laser beam LB may include laser beams over a wide wavelength range of 950 to 1000 nm. Therefore, when the laser processing head 400 of the present embodiment is used with respect to the laser beam LB emitted from the semiconductor laser, the degree of change in the focused beam profile becomes large. Therefore, it is possible to correspond to a wider range of processing conditions or work W.

According to the laser processing head of the present invention, since a laser beam having a focused beam profile according to the processing content, the thickness and material of the work, the processing shape, etc. can be emitted, it can be applied to various laser processing. Further, the laser processing apparatus provided with this laser processing head is excellent in processing accuracy and productivity, and also has high versatility.

1000: Laser processing device 100: Laser oscillator 300: Process fiber 400: Laser processing head 410: Collimeter lens 420: Condensing lens 421: 1st condensing lens 422: 2nd condensing lens 430, 431, 432: Position adjustment mechanism 440: Incident port 500: Machining table 600: Machining control unit 710: X-axis motor 720: Y-axis motor 800: Position control unit 2000: Laser processing equipment 2100: Laser oscillator 2300: Process fiber 2400: Laser processing head 2410: Collimeter lens 2420, 2421: Condensing lens 2500: Machining table 2600: Machining control unit 2710: X-axis motor 2720: Y-axis motor

Claims (3)

A laser oscillator that emits a laser beam with multiple wavelengths,
A laser processing head into which the laser beam is incident, an incident port into which a laser beam having a plurality of wavelengths is incident, a first condensing lens that condenses the laser beam, and condensing by the first condensing lens. A second condensing lens that further condenses the laser beam, which functions as an achromat lens together with the first condensing lens in contact with the first condensing lens, and the above. A laser processing head having a position adjusting mechanism for moving at least one of the first condensing lens and the second condensing lens along the traveling direction of the laser beam.
A position control unit for controlling the position adjustment mechanism is provided.
The first condensing lens and the second condensing lens so that the position control unit satisfies the distance between the first condensing lens and the second condensing lens set according to the object to be processed. A laser processing apparatus that controls the position adjusting mechanism so as to move at least one of the lenses along the traveling direction of the laser beam. The laser processing apparatus according to claim 1, wherein the laser oscillator is a semiconductor laser oscillator. The laser processing head further has a collimator lens provided between the incident port and the first condensing lens.
The laser processing apparatus according to claim 1 or 2, wherein the position adjusting mechanism moves both the first condensing lens and the second condensing lens along the traveling direction of the laser beam.

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