Coat removal method

Abstract

To provide a coat removal method that enables a coat to be effectively removed even when the thickness of the coat is large.SOLUTION: A coat removal method for removing a coat provided on a surface of a processing object includes a first step of applying a laser beam to the coat, and a second step of peeling the coat after laser beam irradiation from the processing object by using an ultrasonic chipper.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a coating removal method for removing a coating provided on the surface of an object to be treated. [Background technology]

[0002] For example, Patent Document 1 describes a conventional technique for surface treatment using laser light, in which a wedge prism that deflects the laser light by a predetermined deflection angle is provided in an irradiation head that irradiates the laser light onto an object to be irradiated, and the laser light is irradiated while rotating this wedge prism around the optical axis of the incident light, so that the irradiated area (beam spot) scans the surface of the object to be irradiated while rotating in an arc, and coatings such as old paint films and foreign matter adhering to the surface of the object to be irradiated are removed (cleaned). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5574354 Summary of the Invention [Problem to be solved by the invention]

[0004] When attempting to remove a relatively thick coating film, for example, a coating film having a thickness of about 1.0 to 1.8 mm, using the above-mentioned laser irradiation method, it is difficult to remove the coating film by laser irradiation alone, and furthermore, the surface quality after laser irradiation may be degraded in some cases. As an alternative to this, it has been considered to remove the coating using a power tool such as a cup wire brush, but this has the problem of increasing the reaction force and vibration load that the worker is subjected to. In view of the above problems, an object of the present invention is to provide a coating removal method that can effectively remove a coating even when the coating is thick. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, a coating removal method according to one embodiment of the present invention is a coating removal method for removing a coating provided on the surface of a processing object, characterized in that it includes a first step of irradiating the coating with laser light, and a second step of peeling the coating after the laser light is irradiated from the processing object using an ultrasonic chipper that ultrasonically vibrates a tool. In this specification and claims, the term "coating" includes not only a coating made of a paint film, but also a film made of a resin-based material such as a lining material. According to this method, a relatively thick coating that is difficult to remove using only a laser can be thermally softened or weakened by laser irradiation and then peeled off using an ultrasonic chipper, making it possible to effectively remove the coating even when the coating is thick.

[0006] The present invention may further comprise a third step of irradiating the surface on which the second step has been performed with laser light. According to this, the coating remaining on the surface of the object to be treated that was not peeled off by the ultrasonic chipper can be removed by the laser light, thereby improving the finishing quality. In the present invention, the third step may be configured to expose a surface of the base material of the processing object. According to this, the object to be treated can be repainted immediately after the third step is carried out. In addition, the formation of irradiation marks from the laser light makes it possible to roughen the surface of the object to be treated, which is advantageous in terms of adhesion to the new coating film.

[0007] In the present invention, in the first step, the laser light can be irradiated so that the irradiated area of ​​the laser light rotates along a predetermined scanning pattern and the scanning pattern moves relative to the object to be processed. In the present invention, in the third step, the laser light can be irradiated so that the irradiated area of ​​the laser light rotates along a predetermined scanning pattern and the scanning pattern moves relative to the object to be processed. This allows a relatively wide area to be efficiently irradiated with a continuous wave (CW) laser.

[0008] In the present invention, the first step may be configured to perform construction while an irradiation head that irradiates the laser light is held by a robot, and the second step may be configured to perform construction while the tool is held by a robot. In the present invention, the third step may be configured to perform construction in a state where an irradiation head that irradiates the laser light is held by a robot. According to each of these inventions, it is possible to promote automation of construction work and further reduce the burden on workers. Effect of the Invention

[0009] As described above, according to the present invention, a coating removal method capable of effectively removing a coating even when the coating is thick can be provided. [Brief description of the drawings]

[0010] [Figure 1] 2 is a cross-sectional view of an irradiation head of a laser irradiation device used in the coating removal method of the embodiment. FIG. [Diagram 2] 2 is a schematic diagram showing a scanning state of a laser beam on a surface of a processing object in the irradiation head of FIG. 1. [Diagram 3] 1 is a diagram showing a schematic configuration of an ultrasonic chipper used in a coating removal method according to an embodiment; [Figure 4] 4 is a photograph showing the surface of a sample before the coating removal method of the embodiment is performed. [Diagram 5] 1 is a photograph showing the surface of a sample after the first step is completed. [Figure 6] 4 is a photograph showing the surface of a sample after the first and second steps have been completed. [Figure 7] 1 is a photograph showing the surface of a sample after a third step has been carried out subsequent to a second step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of a coating removal method according to the present invention will be described. In the embodiment, the coating to be removed is, for example, a coating provided on the surface of a processing object, which is a metal structure such as a steel material. The coating removal method of the embodiment includes the following first to third steps. <First step> The coating is irradiated with laser light to thermally soften or weaken the coating. <Second step> After being irradiated with the laser light, the coating is peeled off from the object to be treated using an ultrasonic chipper. <Third process> After the coating has been peeled off, the object is again irradiated with laser light to remove a portion of the coating remaining on the surface of the object.

[0012] In the coating removal method of this embodiment, the laser light irradiation process in the first and third steps involves scanning the irradiation spot (beam spot BS) on the surface of the object to be processed O by rotating it along a relatively large circumference (circle of rotation) having a diameter of, for example, 10 mm or more. FIG. 1 is a cross-sectional view of an irradiation head of a laser irradiation device used in a coating removal method according to an embodiment.

[0013] The irradiation head 1 irradiates a processing object O with a continuous wave (CW) laser beam B transmitted from a laser oscillator (not shown) via a fiber (not shown). The irradiation head 1 is, for example, a handheld type that can be held by an operator to perform irradiation work, but it can also be used by attaching the irradiation head 1 to a robot that can move along a predetermined path. Moreover, with the irradiation head 1 fixed, the processing object O may be displaced relative to the irradiation head.

[0014] The irradiation head 1 includes a focus lens 10, a wedge prism 20, a protective glass 30, a rotating cylinder 40, a motor 50, a motor holder 60, a protective glass holder 70, a housing 80, a duct 90, and the like.

[0015] The focus lens 10 is an optical element onto which the laser beam B, which is transmitted from a laser oscillator to the irradiation head 1 via a fiber, passes through a collimator lens (not shown) and then enters. A collimating lens is an optical element that collimates the laser light emitted from the end of the fiber into a substantially parallel beam. The focus lens 10 is an optical element that condenses (focuses) the laser beam B emitted by the collimator lens at a predetermined focal position. The focus lens 10 may be, for example, a convex lens having a positive power.

[0016] Furthermore, the beam spot BS, which is the point irradiated on the surface of the processing object O by the laser beam B, is positioned either coincident with this focal position or in a close state included within the focal depth (focused state), or spaced apart from the focal position (defocused state).

[0017] The wedge prism 20 is an optical element that deflects the laser beam B emitted by the focus lens 10 by a predetermined deflection angle θ, thereby making the optical axis angles of the incident side and the exit side different. The wedge prism 20 is formed in the shape of a plate whose thickness changes continuously so that the thickness on one side in a direction perpendicular to the optical axis direction on the incident side is greater than the thickness on the other side. The protective glass 30 is an optical element made of a flat glass or the like and arranged adjacent to the focal position side (the processing object O side, the beam spot BS side) of the wedge prism 20 along the optical axis direction.

[0018] The protective glass 30 is a protective member that prevents foreign matter, such as spatters, peeling material, and dust, scattered from the processing object O side, from adhering to other optical elements, such as the wedge prism 20. The protective glass 30 is an optical element that is located closest to the focal position along the optical axis direction among the optical systems possessed by the irradiation head 1, and is exposed to the treatment object O side through the space A and the inside of the duct 90 described later. The focus lens 10, the wedge prism 20, and the protective glass 30 are configured by applying a coating for the purpose of anti-reflection, surface protection, etc. to the surface of a member made of a transparent material such as optical glass.

[0019] The rotating cylinder 40 is a cylindrical member that holds the focus lens 10 and the wedge prism 20 on its inner diameter side. The rotating cylinder 40 is formed concentrically with the optical axis of the focus lens 10 and the optical axis of the laser beam B incident on the focus lens 10 (the optical axis of the collimator lens). The rotating cylinder 40 is supported by a bearing (not shown) to be rotatable about a central axis of rotation that coincides with the optical axis of the focus lens 10 relative to the housing 80 . The rotating cylinder 40 is made of, for example, a metal such as an aluminum alloy, or an engineering plastic.

[0020] The motor 50 is an electric actuator that drives the rotating cylinder 40 to rotate about the central axis of rotation relative to the housing 80 . The motor 50 is configured, for example, concentric with the rotating cylinder 40 and configured as a circular motor provided on the outer diameter side of the rotating cylinder 40 . A rotor (not shown) of the motor 50 is fixed to the rotary cylinder 40 . The motor 50 is controlled by a motor drive device (not shown) so that the rotation speed of the rotating cylinder 40 substantially coincides with a desired target rotation speed.

[0021] The orientation of the irradiation head 1 is maintained so that the central axis of rotation of the rotating cylinder 40 is perpendicular to the surface of the object to be processed O near the irradiation point, and the motor 50 rotates the wedge prism 20 together with the rotating cylinder 40, so that the beam spot BS circularly scans around the central axis of rotation of the rotating cylinder 40 along the surface of the object to be processed O. In this state, when the irradiation head 1 is translated along the surface of the processing object O, the beam spot BS scans the surface of the processing object O while revolving circumferentially (arcuately). As a result, when focusing on an arbitrary point on the processing object O, the laser beam B is intermittently incident for only a short period of time, and rapid heating and rapid cooling are sequentially performed within a short period of time. At this time, the surface portion of the treatment object O is crushed and scattered.

[0022] The motor holder 60 is a support member that holds the stator (not shown) of the motor 50 in a predetermined position. The main body of the motor holder 60 is formed in a cylindrical shape, and is fixed in a state where it is inserted into the inner diameter side of the housing 80 . The inner peripheral surface of the motor holder 60 is disposed opposite the outer peripheral surface of the motor 50 and is fixed to the stator of the motor 50 .

[0023] A purge gas flow passage 61 through which the purge gas PG flows is formed in part of the gap between the outer peripheral surface and the inner peripheral surface of the motor holder 60 in the axial direction of the motor 50. The purge gas PG is a gas that is ejected toward the treatment object O from space A inside the inner tube 91 of the duct 90 described later, where the surface of the protective glass 30 on the treatment object O side is in contact, when the irradiation head 1 is in use (irradiation). The purge gas PG has a function of preventing debris, such as sputters, dust, and foreign matter, scattered from the processing object O side from flying into the inside of the housing 80 and adhering to the protective glass 30.

[0024] The protective glass holder 70 is a member that is fixed to the inner diameter side of the housing 80 while holding the protective glass 30 . The protective glass holder 70 is formed, for example, in a disk shape with a circular opening formed in the center. The laser beam B passes through the opening from the wedge prism 20 side to the processing object O side. A recess into which the protective glass 30 is fitted is formed on the surface of the protective glass holder 70 facing the treatment object O. The protective glass 30 is held inside the housing 80 in a state where it is fitted into this recess.

[0025] The protective glass 30 is removably attached to a protective glass holder 70 so that it can be replaced if it becomes contaminated or burned out. A surface portion of the protective glass holder 70 opposite to the treatment object O side is disposed opposite to the end face of the motor holder 60 facing the treatment object O side across a gap allowing the purge gas PG to flow.

[0026] The housing 80 is a cylindrical member that constitutes the case of the main body of the irradiation head 1. Inside the housing 80, in addition to the above-mentioned focus lens 10, wedge prism 20, protective glass 30, rotating cylinder 40, motor 50, motor holder 60, protective glass holder 70, etc., the end of the fiber on the irradiation head 1 side (not shown), a collimating lens, etc. are contained.

[0027] The duct 90 is a double-tube member provided so as to protrude from the end of the housing 80 on the treatment object O side. The duct 90 includes an inner cylinder 91, an outer cylinder 92, a dust collector connection cylinder 93, and the like. The motor holder 60, the protective glass holder 70, and the housing 80 described above are formed from, for example, a metal such as an aluminum alloy, engineering plastic, or the like.

[0028] The inner cylinder 91 is formed in a cylindrical shape. The laser beam B passes through the inner diameter side of the inner cylinder 91 and is emitted to the processing object O side. The inner cylinder 91 has an end portion on the housing 80 side formed with a small diameter portion 91a that is stepped smaller in diameter than the other portions. A purge gas PG is introduced from the inside of the housing 80 into the space A inside the small diameter portion 91a.

[0029] At the end of the inner cylinder 91 on the side of the object to be treated O, a tapered portion 91b is formed which tapers toward the object to be treated O so that the diameter of the side of the object to be treated O becomes smaller. The tapered portion 91b has a function of allowing the laser beam B to pass therethrough, while throttling the flow of the purge gas PG to increase the flow rate.

[0030] The outer cylinder 92 is a cylindrical member that is arranged concentrically with the inner cylinder 91 and is provided on the outer diameter side of the inner cylinder 91 . Between the inner peripheral surface of the outer cylinder 92 and the outer peripheral surface of the outer cylinder 91, a continuous gap is formed around the entire circumference. The outer cylinder 92 has an end portion on the housing 80 side formed with a small diameter portion 92a that is stepped smaller in diameter than the other portions. The small diameter portion 92a is fitted into and fixed to the end of the housing 80 on the object to be treated O side. The edge of the end 92b of the outer cylinder 92 on the side of the object to be processed O is formed at an angle with respect to the central axis of rotation of the rotating cylinder 40 so that during normal use when irradiating the object with the central axis of rotation of the rotating cylinder 40 horizontal, the upper side is on the housing 80 side relative to the lower side.

[0031] The dust collection device connecting tube 93 is a cylindrical body that protrudes outward from the outer tube 92 and is connected in a communicated state to the inner diameter side of the outer tube 92 near the end of the outer tube 92 on the side of the material to be treated O. The dust collector connection tube 93 is provided below the outer tube 92 during normal use as described above. The dust-collection device connection tube 93 is disposed at an angle with respect to the outer tube 92 so as to approach the housing 80 side from the treatment object O side and to move away from the outer tube 92. The other end of the dust collector connection tube 93 is connected to a dust collector 140 (described later) and is adapted to be vacuum-suctioned so that the inside becomes negative pressure.

[0032] FIG. 2 is a schematic diagram showing a state in which the surface of the processing object is scanned with a laser beam by the irradiation head of FIG. In this embodiment, by rotating the rotating cylinder 40 and the wedge prism 20 while emitting the laser beam B, the beam spot BS rotates circularly along a rotation circle C having a predetermined diameter (rotation diameter) D along the surface of the object to be processed O. In this state, by moving the irradiation head 1 in a translational manner relatively along the surface of the object to be processed O, it is possible to perform a process in which the beam spot BS scans the surface of the object to be processed O while the turning circle C moves on the irradiated surface at a predetermined feed speed.

[0033] The second step involves using an ultrasonic chipper (ultrasonic vibration peeling device) that ultrasonically vibrates a tool with a cutting edge to peel off the coating. FIG. 3 is a diagram showing a schematic configuration of an ultrasonic chipper used in the coating removal method of the embodiment. The ultrasonic chipper 200 includes an oscillator 210, a cable 220, a handpiece 230, a tool 240, and the like.

[0034] The oscillator 210 generates power to drive a transducer provided in the handpiece 230 . The oscillator 210 has an output of, for example, 500W. The oscillator 210 can be configured to oscillate by, for example, a sweep-locked PLL automatic tracking method. The cable 220 transmits the power generated by the generator 210 to the handpiece 230 .

[0035] The handpiece 230 is provided with a tool 240 and is held by an operator to perform the coating peeling operation. The handpiece 230 includes a transducer that converts the power transmitted from the oscillator 210 via the cable 220 into ultrasonic vibrations. As the vibrator, for example, a Langevin type PZT vibrator can be used. The handpiece 230 is, for example, a handheld type that can be held by an operator to perform the peeling operation, but it is also possible to use the handpiece 230 by attaching it to a robot that can move along a predetermined path.

[0036] Tool 240 is attached to the tip of handpiece 230 and has a cutting edge 241 that separates the coating from the base material during chipping operation. The tool 240 is vibrated by a vibrator provided in the handpiece 230 at a frequency of, for example, about 21 kHz±1.5 kHz. The cutting edge width and tip angle of cutting edge 241 of tool 240 can be changed as appropriate depending on the properties of the coating to be removed. In the second step, the tool 240 is preferably inserted between the coating P and the processing object O from a direction substantially perpendicular to the irradiation direction of the laser light in the first step.

[0037] The results of performing the coating removal method of the embodiment on actual samples will be described below. FIG. 4 is a photograph showing the surface of the sample before the coating removal method of the embodiment is performed. The samples used are, for example, scraps of railway bridges having coatings with thicknesses of about 1.0 to 1.8 mm. The surface area of ​​the area to be removed is, for example, 0.03 m 2 It is. As shown in FIG. 4, the coating is provided over the entire area to be removed.

[0038] FIG. 5 is a photograph showing the surface of the sample after the first step was completed. Although a part of the coating is removed by the laser irradiation in the first step, another part of the coating remains on the surface of the processing object. The areas where the coating remains are believed to be areas where the coating was relatively thick. The remaining coating is thermally softened or weakened by the laser irradiation.

[0039] FIG. 6 is a photograph showing the surface of the sample after the first and second steps have been completed. Even if the coating cannot be completely removed by the laser irradiation in the first step, the coating is weakened by the laser irradiation. In this state, the second step is carried out and the coating is peeled off by an ultrasonic chipper, whereby the coating can be peeled off effectively. Peeling using such an ultrasonic chipper can reduce the amount of dust that is scattered compared to when using a power tool such as a wire cup brush, and can reduce the load on the dust collector. In addition, from the viewpoint of the load on the operator, the load of reaction force and vibration compared to other power tools is suppressed. However, in the state shown in FIG. 6, a portion of the coating that was not peeled off by the ultrasonic chipper remains on the surface of the processing object.

[0040] FIG. 7 is a photograph showing the surface of the sample after the third step has been carried out subsequent to the second step. In the state shown in FIG. 7, the remaining coating has been removed by the laser irradiation in the third step, and as a result, the surface of the base material (typically a steel material) of the processing object is exposed over its entirety. In the state shown in FIG. 7, the surface after treatment exhibits substantially the metallic base color (silver) over the entire surface. In addition, in the state shown in FIG. 7, the excavation marks by the laser beam are distributed over substantially the entire surface of the sample, and the surface roughness is rougher than before the processing. This is advantageous in terms of adhesion with new coatings when repainting.

[0041] According to the embodiment described above, the following effects can be obtained. (1) A relatively thick coating that is difficult to remove using only a laser can be weakened by laser irradiation (first step) and then peeled off using an ultrasonic chipper (second step), thereby enabling the coating to be effectively removed even when it is thick. (2) By performing a third process of irradiating the surface after processing with the ultrasonic chipper with laser light, the coating that was not peeled off by the ultrasonic chipper and remains on the surface of the object to be processed can be removed by the laser light, thereby improving the finishing quality. (3) By exposing the surface of the steel material, which is the base material of the object to be treated, in the third step, the object to be treated can be repainted immediately after carrying out the third step. In addition, by performing the third step by laser irradiation, excavation marks are formed on the surface of the object to be treated by the laser light, and the surface roughness is increased, which improves adhesion with the new coating when repainting is performed. (4) In the first and third steps, the beam spot BS is configured to rotate along a rotation circle C, which is a predetermined irradiation pattern, so that a comparatively wide area can be efficiently irradiated with a continuous wave (CW) laser. (5) When the irradiation head 1 and the handpiece 230 of the ultrasonic chipper 200 are held by a robot during the work, the burden on the worker can be further reduced.

[0042] (Modification) The present invention is not limited to the above-described embodiment, and various modifications and variations are possible, which are also within the technical scope of the present invention. The specific configuration of the coating removal method is not limited to the above-described embodiment, and can be modified as appropriate. Furthermore, the hardware configuration and specifications of the laser irradiation device (irradiation head) and the ultrasonic chipper are not particularly limited. [Explanation of symbols]

[0043] 1 Irradiation head 10 Focus lens 20 Wedge prism 30 Protective glass 40 Rotating cylinder 50 Motor 60 Motor holder 70 Protective glass holder 80 Housing 90 Duct 91 Inner cylinder 91a Small diameter section 91b Tapered portion 92 Outer cylinder 92a Small diameter part 92b End part 93 Dust collector connection tube O Processing object BS Beam spot PG Purge gas B Laser beam 200 Ultrasonic chipper 210 Oscillator 220 Cable 230 Handpiece 240 Tool P Coating

Claims

1. A coating removal method for removing a coating provided on a surface of an object to be treated, comprising the steps of: a first step of irradiating the coating with laser light; a second step of peeling the coating after the laser light irradiation from the processing object using an ultrasonic chipper that ultrasonically vibrates a tool; A coating removal method comprising:

2. A third step of irradiating the surface on which the second step has been performed with laser light is provided. The coating removal method according to claim 1, further comprising the steps of:

3. The third step exposes a surface of the base material of the processing object. The coating removal method according to claim 2, further comprising the steps of:

4. In the first step, the laser light is irradiated so that the irradiation location of the laser light rotates along a predetermined scanning pattern and the scanning pattern moves relative to the processing object.

3. The coating removal method according to claim 1 or 2, characterized in that:

5. In the third step, the laser light is irradiated so that the irradiation location of the laser light rotates along a predetermined scanning pattern and the scanning pattern moves relative to the processing object. The coating removal method according to claim 2 or 3, characterized in that

6. In the first step, the work is performed in a state where an irradiation head for irradiating the laser light is held by a robot; In the second step, the work is performed while the tool is held by a robot. The coating removal method according to claim 1, further comprising the steps of:

7. In the third step, the work is performed in a state where an irradiation head for irradiating the laser light is held by a robot. The coating removal method according to claim 2, further comprising the steps of:

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