JP7185436B2 - Laser processing method - Google Patents

Description

The present invention relates to a laser processing method .

2. Description of the Related Art Conventionally, laser processing has been employed as a means for performing processing such as cutting metal members and joining metal members together. This laser processing is generally carried out by irradiating a processing object with a laser beam having a high energy density which is focused by an optical element or the like and melting the base metal of the irradiation destination. Laser light can be focused by optics to a very small area, and the energy density can be high enough to melt the base metal that it hits. Therefore, according to laser processing, the processing time can be shortened compared to other welding methods, and it is possible to weld metal members having different melting points, which is considered difficult.

However, in laser processing, it is difficult to appropriately control the energy density of the irradiated area of the laser beam, which is the heat source, and there is a problem that the light intensity distribution of the irradiated area tends to vary. Therefore, it has been considered difficult to stably and appropriately perform processing that requires a desired penetration depth of metal. For example, spot welding requires high-strength welding without leaving weld marks on the surface opposite to the welding surface. Problems such as the penetration depth of the metal not reaching the desired depth at the welded portion and the laser beam penetrating the object to be processed and forming a hole are likely to occur.

In order to solve the above-described problem, for example, Patent Document 1 discloses a laser processing technique for uniformizing the light intensity distribution in a laser light irradiation area. Specifically, it is characterized by placing a mask in the center of the laser beam so that the cross-sectional shape of the laser beam is ring-shaped, and then condensing the laser beam until the ring-shaped hollow portion disappears. (See paragraph 0020 of Patent Document 1, etc.). According to the laser processing technology disclosed in Patent Literature 1, uniform laser processing can be performed over a wide range, and welding in a state in which thin metal plates are stacked is also possible.

Japanese Patent Laid-Open No. 07-214360

However, the laser processing technology disclosed in Patent Document 1 has variations in the light intensity distribution in the laser beam irradiation area. I couldn't go to Also, when forming a laser beam having a ring-shaped energy distribution, a method such as arranging a shielding mask in the center of the laser beam is adopted (see paragraphs 0021 and 0040 of Patent Document 1). ), it is difficult to form a ring-shaped laser beam with high accuracy by this method. Therefore, the processing quality could not be stabilized. Furthermore, since the laser light in the area where the mask is arranged is shielded from the object to be processed, the energy loss is large, and the energy intensity tends to decrease remarkably as the outer diameter of the laser light irradiation area increases, which is undesirable.

In view of the above problems, the present application proposes a laser processing method, a laser processing apparatus, and a laser irradiation that can stably reduce variations in the shape and light intensity distribution of the laser light irradiation area without causing energy loss. Intended to provide a head.

The laser processing method according to the present application: The laser processing method according to the present application is a laser processing method for processing an object to be processed using a laser beam, in which a laser beam from a laser oscillator is divided into a plurality of beams, and the surface of the object to be processed Separately and condensed into a plurality of focused spots, rotate and map the plurality of focused spots on the surface of the processing object to form a pseudo-annular laser beam ring, and process with the pseudo-annular laser beam ring Characterized by

Laser processing apparatus according to the present application: The laser processing apparatus according to the present application is a laser processing apparatus that uses laser light to process an object to be processed. and a laser beam rotating mechanism that rotates and maps the plurality of focused spots on the surface of the object to be processed to form a pseudo-annular laser beam ring. characterized by

Laser irradiation head according to the present application: The laser irradiation head according to the present application is a laser irradiation head used in a laser processing apparatus that processes an object to be processed using a laser beam, and the laser beam is emitted to a plurality of condensed spots. It is characterized by separating and condensing light.

The laser processing method, laser processing apparatus, and laser irradiation head according to the present application do not cause energy loss, and can stably reduce variations in the shape of the laser light irradiation region and the light intensity distribution compared to conventional methods. . Therefore, according to the laser processing method, the laser processing apparatus, and the laser irradiation head according to the present application, even when a plurality of thin metal plates are overlapped and welded, processing can be performed stably and with high precision.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram explaining the laser processing apparatus as one Embodiment of this application. It is a figure which shows the arrangement pattern of the condensing spot of the Example of this application. FIG. 3(1) is an observation diagram illustrating a case where the welding state of the welded portion is normal, and FIG. 3(2) is an observation diagram illustrating a case where the welded portion is poorly welded.

Embodiments of a laser processing method, a laser processing apparatus, and a laser irradiation head according to the present application will be described below. However, the laser processing method, laser processing apparatus, and laser irradiation head described below are aspects of the present application, and are not limited to the following aspects.

1. Laser processing method according to the present application The laser processing method according to the present application is a laser processing method for processing an object to be processed using a laser beam. A quasi-annular laser light ring is formed by separating and condensing light into a plurality of converging spots, rotating and mapping the plurality of converging spots on the surface of the object to be processed, and processing with the quasi-annular laser light ring. and The laser processing method according to the present application can utilize the original energy of the laser beam emitted from the laser oscillator without loss, so that variations in the processing speed and light intensity distribution in the laser beam irradiation region can be stably reduced. Below, the present application will be described in detail.

Object to be processed: The object to be processed by the laser in this application is not particularly limited as long as it can be laser processed. For example, it includes surface shape processing of electronic component materials and decorative materials, cutting processing of metal members and carbon fiber materials, welding processing of metal materials, metal and carbon fiber composite materials, and the like.

Condensed spot: The condensed spot in the present application is a portion where the laser beam from the laser oscillator is split into a plurality of parts, and which is a plurality of separated and condensed spots on the surface of the object to be processed. FIG. 1 shows a plurality of focused spots X obtained by splitting the laser beam 10 from the laser oscillator 2 into a plurality of beams and focusing them on the surface of the workpiece 11 . FIG. 2 also shows variations in appearance patterns of the condensed light spots X appearing on the surface of the object 11 to be processed. It should be noted that the separation and collection of light at this time is preferably performed using the optical element 4, which will be described later.

It is preferable that the plurality of condensed spots are separated and condensed at 2 or more and 7 or less points on the surface of the object to be processed. Unless the number of focused spots is two or more, there is no concept of a plurality, and it is difficult to obtain a pseudo-annular laser beam ring, which will be described later, which is not preferable. On the other hand, even if there are more than seven condensed spots, the effect of improving the light intensity distribution of the laser light tends to be saturated, and rather the processing speed of the irradiated area tends to decrease, which is not preferable. Further, an optical element for increasing the number of condensed spots to more than seven is not preferable because the shape becomes complicated and the cost increases. Considering the data obtained as a result of research, it is more preferable that the number of condensed spots is 2 or more and 4 or less.

Considering the arrangement of the focused spots on the surface of the object to be processed, it is preferable that the laser beam from the laser oscillator is divided into a plurality of beams so that the energy of the laser beam is uniform without loss. This is because if there is variation in the energy of the split laser light, there is a high possibility that the processing accuracy will be lowered. At this time, it is preferable that each of the plurality of condensed spots be present at positions that are rotationally symmetrical about a predetermined rotation axis of the plurality of condensed spots. "Positions where multiple focused spots are rotationally symmetrical about a predetermined rotation axis" means that the trajectory in which multiple focused spots rotate draws an arc, and each focused spot passes through that arc. means In such a state, the laser irradiation is not continuous but discontinuous without lowering the processing energy, so that the thermal effect due to the temperature rise during processing can be minimized. A condensed spot that travels along a constant arc track in this way is called a "planetary condensed spot".

As for the arrangement of the condensed spots on the surface of the object to be processed, there are cases where it is desirable to continuously irradiate the laser beam to the rotating shaft portion of the above-described planetary condensed spot depending on the object to be processed. In such a case, it is also possible to arrange one of the plurality of focused spots on the intersection of the surface of the object to be processed and the rotation axis. This focused spot is called a "central focused spot".

This central focused spot is required when the melting point of the object to be processed is high or when a deep processing depth is required. It is also preferable to set the energy of the laser light of the central condensed spot to be stronger than the energy of the laser light to be focused.

Pseudo-toric ring of laser light: The quasi-toric ring of laser light in this application is obtained by rotating a plurality of focused spots. The position of the rotation axis at this time is not particularly limited, but it is preferable to set the axis substantially at the center of the area where a plurality of condensed spots appear on the surface of the object to be processed. When the plurality of condensed spots are rotated at high speed and mapped, the plurality of condensed spots draw a circular trajectory, and as long as the laser light is visually confirmed, it becomes an annular laser beam. This is called a "quasi-annular laser light ring". By using such a quasi-annular laser light ring, heat can be transferred to a wider area than when processing with a single point of laser light, suppressing processing defects due to deviation of the laser light irradiation position, and processing time. It is possible to suppress the deformation of the object to be processed by shortening, and to realize welding of metal members having different melting points. In addition, the energy intensity in the laser beam irradiation area can be made uniform, and the processing accuracy can be improved.

Control of quasi-annular laser light ring: It is preferable to perform processing while moving the quasi-annular laser light ring on the surface of the object to be processed, from the viewpoint of improving the degree of freedom in processing. Further, by moving the quasi-annular laser beam ring on the surface of the object to be processed in this manner, the "laser beam irradiation area" and the "laser beam non-irradiation area" are alternately positioned in the processed portion. Therefore, it is possible to avoid the continuous irradiation of the laser beam to one point, more efficiently avoid the influence of heating, and perform high-quality laser processing. The movement of the quasi-annular laser beam ring on the surface of the object to be processed means that the quasi-annular laser beam ring emitted from the laser irradiation head moves while the object to be processed is stationary. is stationary, and the stage on which the object to be processed is placed moves", and either method may be adopted.

Utilization of pseudo-annular laser light ring: In the pseudo-annular laser light ring according to the present application, if the pseudo-annular laser light ring is a simple ring, the outer peripheral portion of this light ring is the "laser irradiation site". The peripheral portion is the "laser non-irradiated portion". Therefore, if one point on the surface of the object to be processed is defined as a "processing point", when a pseudo-annular laser beam ring obtained by rotating a plurality of focused spots is moved on the surface of the object to be processed, the pseudo-annular laser beam A discontinuous laser irradiation behavior is repeated in which the non-laser-irradiated portion passes after the laser-irradiated portion of the laser light ring passes. As a result, by repeatedly melting the base material by discontinuous laser irradiation, it becomes possible to discharge the dissolved gas generated by the discontinuous laser irradiation behavior and once dissolved in the base material to be processed.

In addition, by repeating the same discontinuous laser irradiation behavior as described above, the base material to be processed is repeatedly melted, and by intermittent laser irradiation, it is also possible to roughen the surface of the target to be processed. be.

2. 1. Laser processing apparatus according to the present application A description will be given with reference to FIG. The laser processing apparatus 1 according to the present application is a laser processing apparatus that processes a processing target 11 using a laser beam 10, and is described as "dividing the laser light 10 from the laser oscillator 2 into a plurality of beams, A laser irradiation head 3 that separates and focuses light on a plurality of focused spots X, and a laser beam rotation mechanism 5 that rotates and maps the plurality of focused spots X on the surface of the workpiece 11 to form a pseudo-annular laser beam ring. ”. With these configurations, it is possible to stably reduce variations in the shape of the laser light irradiation region and the intensity distribution of the laser light without causing energy loss. The laser processing apparatus 1 will be specifically described below. Hereinafter, in describing the laser processing apparatus 1 according to the present application, the laser oscillator 2, the laser irradiation head 3, the laser light rotating mechanism 5, and the laser moving mechanism 6 will be described in this order.

Laser Oscillator: The laser oscillator 2 according to this embodiment is a device that amplifies light and emits a laser beam 10 with excellent directivity and convergence. In general, solid-state lasers (YAG laser, Nd:YAG laser, fiber laser, etc.) and gas lasers (argon ion laser, carbon dioxide laser, excimer laser, etc.) can be used. It is preferred to use FIG. 1 shows a configuration in which a laser beam 10 is directly incident from a laser oscillator 2 to a laser irradiation head 3, which will be described later, but the configuration is not limited to this. For example, an optical fiber may be used as means for transmitting the laser beam 10 from the laser oscillator 2 to the laser irradiation head 3 to facilitate transmission of the laser beam 10 .

Laser irradiation head: The laser irradiation head 3 according to the present application splits the laser beam 10 emitted from the laser oscillator 2 described above, and separates and converges the laser beam 10 into a plurality of focused spots X on the processing surface of the processing object 11. be. The laser irradiation head 3 has a function of separating and condensing light into a plurality of focused spots X and a function of adjusting conditions required for the focused spots X (size of irradiation area, spot shape, amount of energy, etc.).

This laser irradiation head 3 preferably includes an optical element 4 for separating and condensing the laser beam 10 from the laser oscillator 2 into a plurality of converging spots X. As shown in FIG. The laser irradiation head 3 has such an optical element 4 and splits the laser beam 10 oscillated from the laser oscillator 2 into a plurality of laser beams, thereby eliminating the need to use a plurality of laser light sources. As a result, simplification of the structure of the laser processing apparatus 1 can be achieved. When adjusting the size of the irradiation area of the laser beam 10, the distance from the laser oscillator 2 is adjusted by moving the optical element 4 in the optical axis direction by optical element position adjusting means (not shown). can be easily done with

Laser Beam Rotation Mechanism: The laser beam rotation mechanism 5 according to the present application is for rotating the above-described plurality of focused spots X about a predetermined central axis in order to form the above-described quasi-annular laser beam ring. . Here, an optical element 4 for separating and condensing light onto a plurality of condensed spots X provided in the laser irradiation head 3 is rotated horizontally with respect to the lens surface. The rotating means used at this time is not particularly limited, and the optical element 4 can be rotated by, for example, a motor drive.

Laser Moving Mechanism: The laser moving mechanism 6 for moving the laser beam 10 with respect to the processing object 11 is, as described above, a quasi-annular laser light ring itself irradiated from the laser irradiation head 3 while the processing object is stationary. is moved", and "the stage on which the object to be processed is placed is moved while the quasi-annular laser light ring is stationary". It is sufficient to adopt the laser movement mechanism 6 arbitrarily depending on which movement method is adopted.

Although the configuration of the laser processing apparatus 1 according to the present application has been described above, high-quality processing can be performed by the laser irradiation head 3 forming the above-described pseudo-annular laser light ring on the surface of the processing target 11. . Since the effect obtained by forming the quasi-annular laser light ring has already been described in the section "Laser processing method", description thereof will be omitted here.

Next, the optical element 4 of the present application will be described below.

Optical element: The optical element 4 used in this application has at least two focal points in the imaging plane. By having such characteristics, the optical element 4 can split the laser beam 10 from the laser oscillator 2 into a plurality of beams and separate and focus them as a plurality of beam spots X on the surface of the object 11 to be processed. . That is, according to this optical element 4, the energy in the vicinity of the center of the laser beam 10 can be dispersed to suppress the decrease in the total energy of the laser beam irradiation area.

Although there is no particular limitation on the number of optical elements 4 used in the laser processing apparatus 1 according to the present application, it is possible to form the above-described quasi-annular laser beam ring with only one optical element. Therefore, it is possible to suppress an increase in equipment cost and improve maintainability.

At this time, the optical element 4 is composed of, for example, at least one aspherical lens having a free-form surface that is rotationally symmetrical n times with respect to the number n (n is an integer of 2 or more) of the focused spots X. be able to. The optical element 4 of the present application employs a multifocal lens in which the intervals of the condensed spots X on the circumference are uniform, and can stably equalize the intensity distribution of the laser light in the laser light irradiation area. . Further, by providing three or more condensed spots X, it is possible to form the quasi-annular laser light ring without increasing the rotational speed of the condensed spots X more than necessary. It is possible to suppress the harmful effects of vibration caused by driving the light rotating mechanism 5 .

Moreover, it is also preferable to use a diffractive optical element as the optical element 4 that performs such a function. Since the diffractive optical element can split the laser light 10 into a plurality of components while minimizing the energy loss of the laser light 10, the total energy in the laser light irradiation area can be maintained high. It is also preferable to use an axicon lens, which is a prism lens, as the optical element 4 . This is because the axicon lens can also obtain the same effect as the diffractive optical element described above.

Examples of the present application are presented below to describe the present application in more detail. In addition, this application is not limited at all by these examples.

In Example 1, two hot-dip galvanized steel sheets (Z22) having a thickness of 1.0 mm were prepared as objects to be processed. Then, a laser beam oscillated with an output of 2.0 kW from a fiber laser oscillator (manufactured by IPG) is dispersed using an optical element, and a plurality of focused spots on the surface to be processed are rotated at 1000 rpm to 6000 rpm by the operation of a rotating motor. While scanning at a feed rate of 1.0 to 7.0 m/min, laser lap welding was performed on this workpiece. After welding, the state of the weld was observed with a microscope.

Table 1 shows the relationship between the feeding speed of the condensed spots and the arrangement pattern of the condensed spots. The arrangement pattern of condensed spots in Table 1 is shown in FIG. Table 2 shows the relationship between the feed speed of the condensed spot and the rotational speed of the condensed spot. In Tables 1 and 2, "○" indicates that no defect is found in the weld bead (see Fig. 3 (1)), and "X" indicates that the weld bead has defects such as rough surface and bead breakage. ” (see FIG. 3 (1)).

From Tables 1 and 2, according to the method of the present application, by adjusting the feeding speed of the focused spot and the rotation speed of the focused spot, laser lamination of thin metal plates made of galvanized steel, which has been considered difficult in the past, can be achieved. It was confirmed that welding could be performed without problems.

In Example 2, two aluminum plates (A1050) having a thickness of 1.0 mm were prepared as objects to be processed. Then, a laser beam oscillated with an output of 2.0 kW from a fiber laser oscillator (manufactured by IPG) is dispersed using an optical element, and a plurality of focused spots on the surface to be processed are rotated at 1000 rpm to 6000 rpm by the operation of a rotating motor. While scanning at a feed rate of 1.0 to 7.0 m/min, laser lap welding was performed on this workpiece. After welding, the state of the weld was observed with a microscope.

Table 3 shows the relationship between the feeding speed of the condensed spots and the arrangement pattern of the condensed spots. The arrangement pattern of condensed spots in Table 3 is shown in FIG. Table 4 shows the relationship between the feed speed of the condensed spot and the rotational speed of the condensed spot. Since the "◯" and "x" shown in Tables 3 and 4 have already been explained in the first embodiment, the explanation is omitted here.

From Tables 3 and 4, according to the method of the present application, laser lap welding of thin metal plates made of aluminum, which has been considered difficult in the past, can be achieved by adjusting the feeding speed of the focused spot and the rotational speed of the focused spot. It was confirmed that it could be done without problems.

In Example 3, two pure copper plates with a thickness of 1.0 mm were prepared as objects to be processed. Then, a laser beam oscillated with an output of 2.0 kW from a fiber laser oscillator (manufactured by IPG) is dispersed using an optical element, and a plurality of focused spots on the surface to be processed are rotated at 1000 rpm to 6000 rpm by the operation of a rotating motor. While scanning at a feed rate of 1.0 to 7.0 m/min, laser lap welding was performed on this workpiece. After welding, the state of the weld was observed with a microscope.

Table 5 shows the relationship between the feeding speed of the condensed spots and the arrangement pattern of the condensed spots. The arrangement pattern of condensed spots in Table 5 is shown in FIG. Table 6 shows the relationship between the feed speed of the condensed spot and the rotational speed of the condensed spot. Since the "◯" and "x" shown in Tables 5 and 6 have already been explained in the first embodiment, the explanation is omitted here.

From Tables 5 and 6, according to the method of the present application, laser lap welding of thin metal plates made of pure copper, which was conventionally considered difficult, can be performed by adjusting the feeding speed of the focused spot and the rotation speed of the focused spot. It was confirmed that it could be done without problems.

According to the laser processing method, the laser processing apparatus, and the laser irradiation head according to the present application, the shape and light intensity distribution of the laser light irradiation region can be made more stable and uniform than before. Therefore, the laser processing method, the laser processing apparatus, and the laser irradiation head according to the present application can be applied to various types of laser processing, and are also suitable for welding performed by overlapping thin metal plates, which has been considered difficult in the past.

REFERENCE SIGNS LIST 1 laser processing device 2 laser oscillator 3 laser irradiation head 4 optical element 5 laser beam rotating mechanism 6 laser moving mechanism 10 laser beam 11 processing object X focused spot

Claims (4)

A laser processing method for processing a processing target using a laser beam,
The laser beam from the laser oscillator is divided into a plurality of beams, separated into a plurality of focused spots on the surface of the object to be processed, and the plurality of focused spots are rotated and mapped on the surface of the object to be processed to create a pseudo-annular laser. forming an optical ring, processing with the pseudo-annular laser optical ring,
By moving the quasi-annular laser beam ring, which has a laser-irradiated portion and a non-laser-irradiated portion, on the surface of the object to be processed, the laser-irradiated portion of the quasi-annular laser beam ring passes through the processing point of the object to be processed. After that, repeat the discontinuous laser irradiation behavior that the laser non-irradiated part passes through and process it,
A laser processing method characterized by discharging and removing a gas component generated by the discontinuous laser irradiation behavior and dissolved in a base material to be processed by repeatedly melting the base material by laser irradiation. A laser processing method for processing a processing target using a laser beam,
The laser beam from the laser oscillator is divided into a plurality of beams, separated into a plurality of focused spots on the surface of the object to be processed, and the plurality of focused spots are rotated and mapped on the surface of the object to be processed to create a pseudo-annular laser. forming an optical ring, processing with the pseudo-annular laser optical ring,
By moving the quasi-annular laser beam ring, which has a laser-irradiated portion and a non-laser-irradiated portion, on the surface of the object to be processed, the laser-irradiated portion of the quasi-annular laser beam ring passes through the processing point of the object to be processed. After that, repeat the discontinuous laser irradiation behavior that the laser non-irradiated part passes through and process it,
A laser processing method characterized by roughening a surface of an object to be processed by repeatedly melting a base material to be processed by the discontinuous laser irradiation behavior. 3. The laser processing method according to claim 1 , wherein the plurality of condensed spots are obtained by separating and condensing the laser beam from the laser oscillator into 2 or more and 7 or less points. 4. The laser processing method according to any one of claims 1 to 3 , wherein energy of the laser beam separated and focused on the plurality of focused spots is substantially uniform among the focused spots.

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