JP7549981B2 - Surface processing device and method - Google Patents

Description

This disclosure relates to a surface processing device and method for removing paint films, rust, and other deposits from the surface of an object to be processed.

When using a laser to remove a coating film that has been coated on the surface of an object to be processed, a CW (continuous wave) laser method or a short pulse laser method is generally used. Examples of such technologies include those described in the following patent documents:

JP 2013-103228 A

When removing paint films by laser irradiation using a CW (continuous wave) laser method or a short pulse laser method, the workpiece is generally steel. Since steel is a high melting point material, the structural transformation of the workpiece due to the heat input of the laser is not considered to be a big problem. However, when the workpiece is a low melting point material such as an aluminum alloy or resin, if the heat input of the laser is large, the surface temperature of the workpiece may exceed the melting point or aging temperature, which may have a negative effect on the fatigue characteristics. Therefore, when removing paint films from a workpiece that is a low melting point material, it is necessary to reduce the heat input to the workpiece. However, with a laser irradiation device using a CW (continuous wave) laser method or a short pulse laser method, the irradiation time is long compared to the non-irradiation time, and it is easy to perform thermal processing, so it is difficult to reduce the heat input to the workpiece. In addition, in this case, the workpiece is irradiated with a laser beam with a Gaussian distribution, which may have a negative effect on the surface roughness.

The present disclosure aims to solve the above-mentioned problems and provide a surface processing device and method that improves the fatigue life of a workpiece by reducing the amount of heat input to the workpiece during processing.

To achieve the above object, the surface processing device disclosed herein is a surface processing device that irradiates a laser onto the surface of an object to be processed to remove deposits, and is equipped with a laser oscillator capable of irradiating an extremely short pulsed laser, and a beam distribution adjustment device capable of adjusting the peak energy density of the extremely short pulsed laser.

The surface processing method disclosed herein is a surface processing method for removing deposits by irradiating a laser onto the surface of an object to be processed, and includes the steps of: adjusting the peak energy density of an extremely short pulse laser to a predetermined peak energy density range that does not affect thinning of the object to be processed and that can remove only the deposits, according to the material properties of the object to be processed; and irradiating the surface of the object to be processed with the extremely short pulse laser.

The surface processing device disclosed herein can improve the fatigue life of the workpiece by reducing the amount of heat input to the workpiece during processing.

FIG. 1 is a schematic diagram showing the configuration of a surface processing apparatus according to the first embodiment. FIG. 2 is a graph showing a comparison between an ultrashort pulse laser and a short pulse laser. FIG. 3 is a graph for explaining an appropriate energy density by the surface processing apparatus of the first embodiment. FIG. 4 is a graph depicting laser ablation depth versus laser fluence in different materials. FIG. 5 is a schematic diagram showing the configuration of a surface processing apparatus according to the second embodiment. FIG. 6 is a schematic diagram showing the processing of a laser beam by a conventional surface processing device. FIG. 7 is a schematic diagram showing the processing of a laser beam by the surface processing apparatus of the second embodiment. FIG. 8 is a schematic diagram showing a surface processing method using the surface processing apparatus of the second embodiment. FIG. 9 is a schematic diagram showing the configuration of a surface processing apparatus according to the third embodiment. FIG. 10 is a schematic diagram showing a surface processing method using the surface processing apparatus of the third embodiment.

Below, a preferred embodiment of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the various embodiments. Furthermore, the components in the embodiments include those that a person skilled in the art would easily imagine, those that are substantially the same, and those that are within the so-called equivalent range.

[First embodiment]
<Configuration of surface processing device>
FIG. 1 is a schematic diagram showing the configuration of a surface processing apparatus according to the first embodiment.

In the first embodiment, as shown in FIG. 1, the surface processing device 10 irradiates a laser onto the surface of the workpiece 100 to remove deposits. The workpiece 100 has deposits 102 on the surface of a base material 101. Here, the base material 101 of the workpiece 100 is a low-melting point material. Low-melting point materials include metal alloys such as aluminum alloys with an aging temperature of about 100 degrees or less than 100 degrees, and synthetic resin materials. Also, examples of deposits 102 include paint films and rust.

The surface processing device 10 has a laser oscillation device 11, a laser processing head 12, a transmission fiber 13, a moving device 14, and a control device 15.

The laser oscillation device 11 is capable of emitting an extremely short pulse laser L. The extremely short pulse laser L is a pulse laser with a pulse width of picoseconds or less. In this case, the shorter the pulse width of the extremely short pulse laser L, the more preferable it is, and it may be a pulse laser of femtoseconds or less. Since the laser oscillation device 11 is capable of emitting a pulse laser with a pulse width of picoseconds or less or femtoseconds or less, it is possible to reduce the amount of heat input to the workpiece 100 compared to a short pulse laser.

The laser processing head 12 has a focusing optical system 21, a galvanometer motor 22, and a processing nozzle 23. Although not shown, the focusing optical system 21 is composed of, for example, multiple convex lenses and concave lenses. It is preferable that the extremely short pulse laser L is focused once between each lens.

The focusing optical system 21 functions as the beam distribution adjustment device of the present invention. The focusing optical system 21 can adjust the beam distribution of the extremely short pulse laser L. Specifically, the focusing optical system 21 adjusts the beam distribution by adjusting the beam diameter of the extremely short pulse laser L. The focusing optical system 21 focuses the extremely short pulse laser L and outputs it from the processing nozzle 23. The focusing optical system 21 adjusts the beam diameter depending on the difference in the irradiation position. The galvanometer motor 22, not shown, scans the extremely short pulse laser L by the angle of the galvanometer mirror.

The laser oscillator 11 and the laser processing head 12 are connected by a transmission fiber 13. The transmission fiber 13 guides the extremely short pulse laser L oscillated from the laser oscillator 11 to the laser processing head 12.

The moving device 14 can move the laser processing head 12 at least along the laser irradiation direction and the laser scanning direction. The laser scanning direction is a direction perpendicular to the laser irradiation direction. The control device 15 can control the laser oscillation device 11.

The laser processing head 12 also has a polarizing plate (polarizing member) 24. The extremely short pulse laser L oscillated by the laser oscillator 11 is a single mode laser, and may be polarized. The polarizing plate 24 controls the polarization state so that the laser beam of the extremely short pulse laser L oscillated from the laser oscillator 11 becomes circularly polarized. By circularly polarizing the extremely short pulse laser L with the polarizing plate 24, the uniformity within the surface is improved, and output bias in the scanning direction can be suppressed.

The extremely short pulse laser L is often used for micromachining because of its high peak energy density. However, when such an extremely short pulse laser L is applied to remove adhesions (paint film) 102 from the surface of the workpiece 100, not only the adhesions 102 but also the surface of the base material 101 is processed, causing roughness on the surface of the base material 101. Therefore, the surface processing device 10 of the first embodiment adjusts the irradiation position of the extremely short pulse laser L from the focusing optical system 21 to adjust the beam diameter, thereby reducing the peak energy density of the extremely short pulse laser L and optimizing the energy density according to the material properties of the workpiece 100.

Figure 2 is a graph showing a comparison between an ultrashort pulse laser and a short pulse laser, Figure 3 is a graph explaining the appropriate energy density using the surface processing device of the first embodiment, and Figure 4 is a graph showing the laser removal depth versus laser fluence in different materials.

As shown in Figures 1 and 2, the ultrashort pulse laser and the short pulse laser are oscillated at a predetermined cycle. At this time, the pulse width W1 of the ultrashort pulse laser L is narrower than the pulse width W2 of the short pulse laser, and the laser output density P1 of the ultrashort pulse laser L is higher than the laser output density P2 of the short pulse laser. Therefore, as shown in Figures 1 and 3, the peak energy density of the ultrashort pulse laser L is adjusted to a predetermined peak energy density range that does not affect the thinning of the workpiece 100 according to the material properties of the workpiece 100 (base material 101) and can remove only a predetermined depth.

As shown in FIG. 3, region A1 is a peak energy density range where thinning of the workpiece 100 may occur. Here, the peak energy density of the extremely short pulse laser L is reduced so that the peak value is located in region A2. Region A2 is a predetermined peak energy density range that does not affect thinning of the workpiece 100 and can remove only a predetermined depth, that is, the extremely short pulse laser L. Note that if the peak energy density of the extremely short pulse laser L is further reduced by the focusing optical system 21, the peak value will be located in region A3. This region A3 is a peak energy density range that does not affect thinning of the workpiece 100 but cannot remove the deposit 102.

Area A2, which is a predetermined peak energy density range that does not affect the thinning of the workpiece 100 and can remove a predetermined depth, differs depending on the material properties of the base material 101 of the workpiece 100. As shown in FIG. 4, the removal depth per laser pulse relative to the laser fluence (peak energy density) differs depending on the material properties of the base material 101. For example, PMMA acrylic resin and polyimide as low melting point materials, and steel as high melting point material, have different relationships between the laser fluence and the removal depth per laser pulse. Area A2 is an area where the ratio of the removal speed between the low melting point material of the base material 101 and the surface deposit 102 is preferably about 10 or more.

<Operation of the surface treatment device>
As shown in FIG. 1, in the surface processing device 10, the control device 15 controls the laser oscillation device 11 to oscillate an extremely short pulse laser L. The extremely short pulse laser L is guided to the laser processing head 12 by a transmission fiber 13. Here, the peak energy density of the extremely short pulse laser L is adjusted by adjusting the beam diameter or focal length of the extremely short pulse laser L. Specifically, the peak energy density of the extremely short pulse laser L is adjusted to a predetermined peak energy density range that does not affect the thinning of the workpiece 100 according to the material characteristics of the workpiece 100 (base material 101) and can remove the deposit 102. When adjusting the peak energy density of the extremely short pulse laser L, the thickness of the deposit 102 to be removed from the surface of the base material 101 is also taken into consideration.

The polarizing plate 24 controls the extremely short pulse laser L so that the laser beam becomes circularly polarized. This improves uniformity in a plane perpendicular to the laser irradiation direction of the extremely short pulse laser L. In this state, the control device 15 scans the extremely short pulse laser L using the galvanometer motor 22. As a result, the surface of the workpiece 100 is peeled off by a predetermined thickness by irradiation with the extremely short pulse laser L, and only the deposits 102 are removed without damaging the surface of the base material 101.

[Second embodiment]
5 is a schematic diagram showing the configuration of a surface processing device according to a second embodiment of the present invention. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions thereof are omitted.

In the second embodiment, as shown in FIG. 5, the surface processing device 10A has a laser oscillation device 11, a laser processing head 12, a transmission fiber 13, a moving device 14, and a control device 15. Here, the laser oscillation device 11, the transmission fiber 13, the moving device 14, and the control device 15 are the same as those in the first embodiment, so detailed explanations are omitted.

The laser processing head 12 has a beam shaping device 25 in addition to a focusing optical system 21, a galvanometer motor 22, and a processing nozzle 23. Here, the focusing optical system 21 and the processing nozzle 23 are the same as those in the first embodiment, so detailed explanations are omitted.

The beam shaping device 25 has a diffractive optical element 26 and an aperture 27. The extremely short pulse laser L is a Gaussian beam, and the diffractive optical element 26 shapes the Gaussian beam to have a flat peak value by diffracting and interfering with it. The aperture 27 reduces the beam diameter of the extremely short pulse laser (Gaussian beam) L by removing unnecessary parts of the light separated by the diffractive optical element 26.

Conventionally, as shown in FIG. 6, the peak energy density of an extremely short pulse laser (a) emitted from a laser oscillator is reduced and the beam diameter is expanded (b). Then, an aperture is used to remove all areas except for those a specified distance away from the center position of the extremely short pulse laser. In this case, even if the energy density is reduced, a peak value still exists in the energy distribution, which may adversely affect the base material of the workpiece.

On the other hand, as shown in FIG. 7, the beam shaping device 25 of the second embodiment reduces the peak energy density of the extremely short pulse laser (a) emitted from the laser oscillator by the diffractive optical element 26, separates the beam in the radial direction, and shapes each peak value to be flat (b). Then, the aperture 27 removes the extremely short pulse laser L except for the area a predetermined distance away from the center position. Then, the extremely short pulse laser L has a beam distribution with a flat peak value and a small radial outer skirt portion. Therefore, the aperture 27 does not irradiate the extremely short pulse laser to areas other than the area a predetermined distance away from the center, so that damage caused by the extremely short pulse laser to areas other than the object 100 to be processed can be suppressed. In addition, the peak value of the extremely short pulse laser L is almost flat, resulting in a uniform energy density, and the deposit 102 can be uniformly removed.

As shown in FIG. 8, the beam shaping device 25 shapes the beam shape of the ultrashort pulse laser L into a rectangular shape at the irradiation position where the ultrashort pulse laser L reaches the surface of the workpiece 100. The ultrashort pulse laser L has a beam shape with a flat peak value and a small radially outer base. Therefore, a rectangular attachment removal area La can be formed on the surface of the workpiece 100 with one pulse of the ultrashort pulse laser L. Then, when the ultrashort pulse laser L is irradiated onto the surface of the workpiece 100 while moving the laser processing head 12, the attachment removal area La can be removed in an area of width Wa and length Sa in which the attachment removal area La is continuous in the scanning direction, as if the rectangular attachment removal area La is spread out, and the attachment 102 can be removed uniformly without wasting energy.

[Third embodiment]
9 is a schematic diagram showing the configuration of a surface processing device according to a third embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions thereof are omitted.

In the third embodiment, as shown in FIG. 9, the surface processing device 10B has a laser oscillation device 11, a laser processing head 12, a transmission fiber 13, a moving device (support device) 14, and a control device 15. The surface processing device 10B also has an air ejection device 31, a recovery device 32, and a cooling device 33.

Here, the laser oscillation device 11, the laser processing head 12, the transmission fiber 13, and the control device 15 are the same as those in the first embodiment. The moving device 14 is a multi-joint robot. The multi-joint robot supports the laser processing head 12 and is capable of moving along the laser scanning direction. The control device 15 is capable of controlling the multi-joint robot as the moving device 14.

The air ejection device 31 has a compressed air supply source 41 and a cleaning filter 42, and is connected to the laser processing head 12 via the piping 13a. The air ejection device 31 supplies compressed air from the compressed air supply source 41 to the laser processing head 12 from the piping 13a through the cleaning filter 42. The laser processing head 12 ejects compressed air at the laser irradiation position on the workpiece 100 to remove the removed attachments 102, fumes, etc. from the laser irradiation position. The recovery device 32 is connected to the laser processing head 12 via the piping 13b. The recovery device 32 recovers the attachments 102, fumes, etc. removed from the workpiece 100 via the piping 13b. The cooling device 33 cools the laser oscillation device 11 by circulating a cooling medium.

9 and 10, in the surface processing device 10B, the control device 15 controls the laser oscillation device 11 to oscillate an extremely short pulse laser L from the laser processing head 12 to the workpiece 100. The control device 15 also scans the extremely short pulse laser L using the galvanometer motor 22. Here, parameters such as the output of the extremely short pulse laser L oscillated by the laser oscillation device 11, the laser scanning speed of the laser processing head 12, and the laser scanning pattern of the laser processing head 12 are set as a control program. The control device 15 controls the laser oscillation device 11 and the moving device 14 based on the control program. At this time, the air ejection device 31 ejects compressed air from the laser processing head 12 to the laser irradiation position on the workpiece 100, thereby removing the removed attachment 102, fumes, etc. from the laser irradiation position. The recovery device 32 also recovers the attachment 102, fumes, etc. removed from the workpiece 100 via the piping 13b. Therefore, the surface of the workpiece 100 is peeled off by a predetermined thickness by irradiation with the ultrashort pulse laser L, and only the attached matter 102 is removed without damaging the surface of the base material 101.

The laser processing head 12 is fitted with a processing nozzle 23 made of a translucent laser absorbing material at its tip, and the moving device 14 moves the laser processing head 12 while pressing the processing nozzle 23 of the laser processing head 12 against the surface of the workpiece 100. As a result, the deposits 102 and fumes removed from the workpiece 100 by the processing nozzle 23 do not scatter into the surrounding area, and can be properly collected by the collection device 32.

[Effects of this embodiment]
The surface processing apparatus of the first aspect is a surface processing apparatus 10, 10A, 10B that irradiates a laser onto the surface of an object to be processed 100 to remove adhesions 102, and is equipped with a laser oscillation device 11 capable of irradiating an extremely short pulse laser L, and a beam distribution adjustment device capable of adjusting the peak energy density of the extremely short pulse laser L.

The surface processing device according to the first aspect can reduce the amount of heat input to the workpiece 100 during processing with the ultrashort pulse laser L by irradiating the surface of the workpiece 100 with an extremely short pulse laser L whose peak energy density has been properly adjusted, and can improve the fatigue life of the workpiece 100 by properly removing only the deposits 102.

The surface processing device according to the second aspect adjusts the peak energy density of the ultrashort pulse laser L to a preset peak energy density range that does not affect thinning of the workpiece 100 and can remove the deposits 102 to a predetermined depth according to the material characteristics of the workpiece 100. This makes it possible to irradiate the surface of the workpiece 100 with an ultrashort pulse laser L whose peak energy density has been appropriately adjusted, regardless of the material characteristics of the workpiece 100, and to reduce the amount of heat input to the workpiece 100 during processing with the ultrashort pulse laser L, thereby appropriately removing only the deposits 102.

In the surface processing device according to the third aspect, the beam distribution adjustment device adjusts the peak energy density by adjusting at least one of the beam diameter and focal length of the extremely short pulse laser L. This makes it possible to appropriately adjust the peak energy density of the extremely short pulse laser L in a simple manner.

The surface processing device according to the fourth aspect is provided with a focusing optical system 21 as a beam distribution adjustment device. This allows for a simplified structure.

The surface processing device according to the fifth aspect is provided with a polarizing plate (polarizing member) 24 capable of polarizing the beam of the extremely short pulse laser L. As a result, the polarization state of the extremely short pulse laser L oscillated from the laser oscillation device 11 is controlled by the polarizing plate 24 so that the laser beam becomes circularly polarized, improving the uniformity in the plane perpendicular to the irradiation direction of the extremely short pulse laser L and suppressing output bias in the scanning direction.

In the surface processing device according to the sixth aspect, the extremely short pulse laser L is a Gaussian beam, and a beam shaping device 25 is provided that diffracts and interferes with the Gaussian beam to shape the peak value to be flat and reduce the beam diameter. As a result, the extremely short pulse laser L has a beam distribution with a flat peak value and a small radially outer skirt portion, improving the removal efficiency of the deposit 102, and since it has a uniform energy density, the deposit 102 can be removed uniformly.

In the surface processing device according to the seventh aspect, the beam shaping device 25 shapes the beam shape of the extremely short pulse laser L into a rectangular shape at the irradiation position of the workpiece 100. As a result, when the extremely short pulse laser L is irradiated onto the surface of the workpiece 100 while moving the laser processing head 12, the attachments 102 can be removed so as to completely cover the rectangular attachment removal area La without any gaps, and the attachments 102 can be removed uniformly without wasting energy.

The surface processing device according to the eighth aspect connects a laser processing head 12 to a laser oscillation device 11 via a transmission fiber 13, and connects to the laser processing head an air ejection device 31 that ejects air at the laser irradiation position on the workpiece 100, and a recovery device 32 that recovers the deposits 102 removed from the workpiece 100. This allows the deposits 102 to be removed from the workpiece 100 with high accuracy.

The surface processing device according to the ninth aspect connects a laser processing head 12 to a laser oscillation device 11 via a transmission fiber 13, provides a moving device (support device) 14 capable of moving the laser processing head 12 along the scanning direction, and provides a control device 15 capable of controlling the moving device 14. This allows the attachment 102 to be removed from the workpiece 100 with high accuracy.

In the surface processing device according to the tenth aspect, the workpiece 100 is a low melting point material. As a result, by irradiating the surface of the workpiece 100 with an extremely short pulse laser L whose peak energy density has been properly adjusted, the amount of heat input to the workpiece 100 during processing with the extremely short pulse laser L can be reduced, and the fatigue life of the workpiece 100 can be improved even if the workpiece 100 is a low melting point material.

The surface processing method according to the eleventh aspect is a surface processing method for irradiating a laser onto the surface of a workpiece 100 to remove an attachment 102, and includes the steps of adjusting the peak energy density of the extremely short pulse laser L to a predetermined peak energy density range that does not affect the thinning of the workpiece 100 and can remove only the attachment according to the material characteristics of the workpiece 100, and irradiating the surface of the workpiece 100 with the extremely short pulse laser L. As a result, by irradiating the surface of the workpiece 100 with the extremely short pulse laser L whose peak energy density has been appropriately adjusted, the amount of heat input to the workpiece 100 during processing with the extremely short pulse laser L can be reduced, and by appropriately removing only the attachment 102, the fatigue life of the workpiece 100 can be improved.

10, 10A, 10B Surface processing device 11 Laser oscillation device 12 Laser processing head 13 Transmission fiber 14 Moving device (support device)
15 Control device 21 Focusing optical system (beam distribution adjustment device)
22 Galvano motor 23 Processing nozzle 24 Polarizing plate (polarizing member)
25 Beam shaping device 26 Diffractive optical element 27 Aperture 31 Air ejection device 32 Recovery device 33 Cooling device 41 Compressed air supply source 42 Cleaning filter 100 Processing object 101 Base material 102 Adherent matter L Ultrashort pulse laser

Claims (9)

A surface processing device for removing deposits by irradiating a laser onto a surface of an object to be processed , the surface being an aluminum alloy or a low-melting-point material having an aging temperature of 100° C. or less, comprising:
A laser oscillator capable of emitting an extremely short pulse laser;
a beam distribution adjusting device capable of adjusting a peak energy density of the ultrashort pulse laser;
Equipped with
the beam distribution adjustment device adjusts the peak energy density of the ultrashort pulse laser to a predetermined peak energy density range that is set in advance in accordance with the thickness of the deposit, which is one of the material properties of the workpiece, and that is capable of removing the deposit to a predetermined depth without affecting thinning of the workpiece.
Surface processing equipment. The beam distribution adjustment device adjusts the peak energy density by adjusting at least one of a beam diameter and a focal length of the ultrashort pulse laser.
The surface processing device according to claim 1. The beam distribution adjustment device has a focusing optical system.
The surface processing device according to claim 2. A polarizing member capable of polarizing the beam of the ultrashort pulse laser,
The surface processing device according to any one of claims 1 to 3. The ultrashort pulse laser is a Gaussian beam, and a beam shaping device is provided that diffracts and interferes with the Gaussian beam to flatten a peak value and reduce a beam diameter.
The surface processing device according to any one of claims 1 to 4. The beam shaping device shapes the beam shape of the extremely short pulse laser into a rectangular shape at the irradiation position of the workpiece.
The surface processing apparatus according to claim 5. A laser processing head is connected to the laser oscillation device via a laser transmission fiber, and the laser processing head is connected to an air ejection device that ejects air at a laser irradiation position on the processing object, and a recovery device that recovers the deposit removed from the processing object.
The surface processing device according to any one of claims 1 to 6. A laser processing head is connected to the laser oscillation device via a laser transmission fiber, a support device capable of moving the laser processing head along a scanning direction is provided, and a control device capable of controlling the support device is provided.
The surface processing device according to any one of claims 1 to 7. A surface processing method for removing deposits by irradiating a laser onto a surface of an object to be processed , the surface being an aluminum alloy or a low-melting-point material having an aging temperature of 100° C. or less, comprising:
adjusting a peak energy density of the ultrashort pulse laser to a predetermined peak energy density range that is set in advance according to a thickness of the deposit, which is one of the material properties of the object, and that does not affect thinning of the object and can remove only the deposit;
irradiating a surface of the object with the ultrashort pulse laser;
The surface processing method includes the steps of:

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