Method for drying heat-resistant paint

Abstract

To enable utilization of a laser beam to dry a coating film of heat-resistant paint.SOLUTION: A method for drying heat-resistant paint includes the steps of irradiating a painted surface of a member to which heat-resistant paint is coated with a laser beam, and scanning an irradiation position to dry a coating film of the heat-resistant paint, where a laser irradiation condition includes a temperature at which heat-resistant paint is heated with the laser beam is 150 to 270 degrees, a scan speed of the laser beam is 0.5 to 6 m / s, and output of the laser beam is 460 to 2800 W.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for drying a heat-resistant paint, in which a surface of a member coated with the heat-resistant paint is irradiated with a laser to dry the paint. [Background technology]

[0002] Patent Document 1 describes a method of drying a solid lubricant coating applied to the skirt portion of a piston of an internal combustion engine, in which the solid lubricant coating is irradiated with a laser. On the other hand, for components to which heat-resistant paint is applied, such as automobile mufflers, a drying oven is used to dry the heat-resistant paint. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5755820 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, a drying oven is used to dry heat-resistant paint because heat-resistant paint contains resins and solvents, and irradiating a heat-resistant paint film with a laser may cause discoloration or scratches on the film.

[0005] However, drying ovens use electricity or gas to heat the interior of the oven and dry the entire component coated with the heat-resistant paint to harden the coating, which creates the problem of increased energy consumption (and therefore CO2 emissions).

[0006] One aspect of the present disclosure aims to reduce CO2 emissions by enabling the use of lasers to dry heat-resistant paint coatings. [Means for solving the problem]

[0007] A method for drying heat-resistant paint according to one embodiment of the present disclosure is a method for drying the coating of heat-resistant paint by irradiating a laser onto the painted surface of a component to which the heat-resistant paint has been applied and scanning the irradiation position. In the drying method of the present disclosure, the laser irradiation conditions are set within the ranges of a laser heating temperature of 150 to 270 degrees, a laser scanning speed of 0.5 to 6 m / s, and a laser output of 460 to 2800 W.

[0008] The irradiation conditions are set by irradiating a sample coated with a heat-resistant coating with a laser and evaluating the state of the coating after irradiation, as described in the embodiment below. Note that the laser output represents the average output.

[0009] Therefore, according to the drying method of the present disclosure, the coating film on a member coated with a heat-resistant paint can be dried well using a laser. Furthermore, the laser can be irradiated onto the coated surface of the member and scanned to directly heat the coating film, thereby drying and hardening it, which reduces energy consumption and CO2 emissions compared to using a drying oven.

[0010] Here, in the method for drying a heat-resistant paint of the present disclosure, the surface of the coating film may be dried by blowing air before irradiating with a laser under the irradiation conditions. In other words, because heat-resistant paints contain resins and solvents, depending on the type of heat-resistant paint, it is thought that the volatile solvents contained in the paint film may be more likely to ignite when irradiated with a laser. However, if air is blown onto the paint film before irradiating with a laser, there is no need to evaporate the solvent by natural drying, and the solvent can be forcibly evaporated by blowing air, so that laser drying can be carried out in a short time after the heat-resistant paint is applied.

[0011] The method for drying heat-resistant paint disclosed herein can be applied to any component to which heat-resistant paint is applied, but since heat-resistant paint is used to paint automobile mufflers, the component to which the heat-resistant paint is dried may also be an automobile muffler. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a configuration diagram illustrating a drying facility according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing laser irradiation conditions. [Figure 3] FIG. 3 is an explanatory diagram illustrating an example of an experiment conducted to set the irradiation conditions of FIG. 2. [Figure 4] FIG. 4 is an explanatory diagram showing the results of the experiment shown in FIG. 3. [Figure 5] FIG. 10 is an explanatory diagram showing an example of a drying process performed after a muffler painting process. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [composition] The drying equipment 1 of this embodiment shown in Figure 1 is intended to dry a coating film 10A on an automobile muffler 10 to which heat-resistant paint has been applied using a painting tool such as a spray gun, and is equipped with a mounting table 20 for the automobile muffler 10 and a drying robot 30.

[0014] The muffler 10 for an automobile comprises a muffler body 12 that functions as a silencer, a first pipe 14 that guides exhaust gas emitted from the engine to the muffler body 12, and a second pipe 16 that discharges the exhaust gas that has passed through the muffler body 12 from an exhaust port 18.

[0015] In this embodiment, the muffler body 12 has a cylindrical shape, and the first pipe 14 is connected to one end of the cylinder in the direction of the central axis Z, and the second pipe 16 is connected to the other end of the cylinder in the direction of the central axis Z. A heat-resistant paint is applied to the outer wall of the muffler body 12 on the side of the first pipe 14 in a painting process, thereby forming a coating film 10A.

[0016] The mounting base 20 includes a rotating base 24 on which the automotive muffler 10 is mounted with the second pipe 16 facing downward, and a mounting base main body 22 that supports the rotating base 24 so that it can rotate on a horizontal plane.

[0017] The mounting base main body 22 houses an actuator that rotates the rotating base 24 by rotation of a motor. The rotating base 24 is provided with a jig (not shown) for fixing the automotive muffler 10 so that the central axis Z of the muffler main body 12 coincides with the central axis of rotation of the actuator.

[0018] For this reason, the automobile muffler 10 is fixed to the rotating table 24 via a jig so that it can rotate around the central axis Z of the muffler body 12, and is rotated around the central axis Z of the muffler body 12 as the rotation axis by an actuator housed in the mounting table body 22.

[0019] Next, the drying robot 30 is used to irradiate the coating film 10A of the automobile muffler 10 fixed to the rotating table 24 with a laser, thereby drying and hardening the coating film 10A. The drying robot 30 comprises a base 32 installed around the mounting table 20, a first arm 34 having one end fixed onto the base 32, a second arm 36 having one end fixed to the other end of the first arm 34, and a head 50 fixed to the other end of the second arm 36.

[0020] The first arm 34 is fixed to the base 32 via a first motor 38 and a second motor 40 provided on the base 32 so as to be rotatable around the rotation axes of the first motor 38 and the second motor 40. The rotation axis of the first motor 38 is in a vertical direction perpendicular to the upper surface of the base 32, and the rotation axis of the second motor 40 is in a horizontal direction perpendicular to the rotation axis of the first motor 38.

[0021] The second arm 36 is fixed to be rotatable around the rotation axis of a third motor 42 provided on the opposite side of the first arm 34 from the base 32. The rotation axis of the third motor 42 is parallel to the rotation axis of the second motor 40.

[0022] Furthermore, a length adjustment unit 44 that can adjust the length of the second arm 36 is provided on the opposite side of the second arm 36 from the first arm 34. The length adjustment unit 44 is configured, for example, with a cylinder that can adjust the amount of protrusion of the rod.

[0023] Therefore, the head 50 of the drying robot 30 can be adjusted in position in three dimensions via the first motor 38, the second motor 40, the third motor 42, and the length adjustment unit 44. In addition, as shown by the dotted lines in Figure 1, the head 50 houses a light source that can irradiate the automobile muffler 10 with a laser, a lens that can adjust the irradiation range of the laser from the light source, and an actuator that can adjust the irradiation direction of the laser.

[0024] Therefore, the head 50 can adjust the output (average output) of the laser from the light source when irradiating and drying the coating film 10A of the automotive muffler 10. In addition, the irradiation range (area) of the laser irradiated onto the coating film 10A can be adjusted via the lens, and the irradiation position of the laser can be adjusted via the actuator.

[0025] [Drying method] In the drying equipment 1 of this embodiment, when drying the automobile muffler 10 placed on the mounting table 20, the rotating table 24 is rotated at a constant speed by an actuator provided on the mounting table main body 22, causing the automobile muffler 10 to rotate around the central axis Z.

[0026] At the same time, the drying robot 30 is operated in accordance with a preset control program to bring the head 50 close to the automotive muffler 10 and irradiate the coating film 10A on the muffler body 12 with a laser.

[0027] At this time, since the laser is irradiated from the light source onto the coating film 10A via a lens, the laser irradiation range is dot-shaped, and the diameter (hereinafter referred to as the spot diameter) changes depending on the lens position.

[0028] Furthermore, the position at which the laser is irradiated from the head 50 onto the coating film 10A changes with the rotation of the automotive muffler 10 on the mounting table 20. Therefore, the laser is scanned around the central axis Z on the outer circumferential surface of the muffler body 12, and the scanning speed changes according to the rotation speed of the mounting table 20.

[0029] In addition, the drying robot 30 moves the head 50 in an axial direction parallel to the central axis Z of the muffler body 12 in synchronization with the rotation of the automobile muffler 10, thereby moving the laser irradiation position in the direction of the central axis Z by the length of the spot diameter per rotation of the muffler body 12.

[0030] Therefore, the drying robot 30 can irradiate the entire area of ​​the heat-resistant paint coating film 10A on the automobile muffler 10 with a laser, thereby drying and hardening the coating film 10A. Here, the temperature to which the coating film 10A is heated by irradiating it with a laser (hereinafter referred to as irradiation temperature) is determined by the laser output from the light source and the laser irradiation time, and the irradiation time varies depending on the laser scanning speed.

[0031] Therefore, if the relationship between the irradiation temperature required to dry the coating film 10A of the desired thickness cleanly with an appropriate hardness and the laser output and scanning speed is known, these parameters (i.e., irradiation temperature, output, scanning speed) can be set as the drying conditions for the coating film 10A.

[0032] Therefore, in this embodiment, the allowable range of the film thickness of the coating film 10A was set to 17.5 μm to 22.5 μm, which is suitable for the coating film 10A of the automobile muffler 10, and the irradiation temperature, output, and scanning speed suitable for drying and curing the coating film 10A of this film thickness with a laser were determined through experiments.

[0033] As a result, as shown in Figure 2, it was found that when the irradiation temperature was within the range of 150 to 270 degrees, the scanning speed was 0.5 to 6 m / s, and the output was 460 to 2800 W, the coating film 10A with a film thickness of 17.5 μm to 22.5 μm could be dried and cured well.

[0034] Therefore, in this embodiment, the coating film 10A having a thickness of 17.5 μm to 22.5 μm is dried by operating the mounting table 20 and the drying robot 30 so that the laser irradiation temperature, scanning speed, and output satisfy the irradiation conditions shown in Fig. 2. The thickness of the coating film 10A can be said to be one of the laser irradiation conditions in this embodiment.

[0035] [Setting the lighting conditions] Next, an experiment conducted to determine the irradiation conditions shown in FIG. 2 will be described. In this experiment, as shown in Figure 3A, a number of samples were prepared with heat-resistant paints applied to surfaces with thicknesses ranging from 17.5 μm to 22.5 μm, and the laser output and scanning speed were changed for each sample, and the laser was irradiated over the entire painted surface with a constant spot diameter. In this experimental example, the spot diameter was 42 mm.

[0036] In addition, in the irradiation area of ​​each sample irradiated with the laser in this way, measurement points P1, P2, and P3 were set at predetermined intervals in the laser scanning direction, and the temperature (i.e., irradiation temperature) and film thickness during laser irradiation at each measurement point P1 to P3 were measured, as shown in Fig. 3B. Therefore, the measurement results shown in Fig. 3B were created for each sample, starting with sample No. 1.

[0037] Furthermore, for each sample whose coated surface was irradiated with a laser in the above experiment, a visual inspection and a well-known pencil hardness test were carried out to determine whether the drying state of the coating film 10A was good or bad. In the visual inspection, an inspector visually inspects the painted surface, judging whether the appearance is normal (for example, whether there are no scratches or discoloration), assuming that the solvent in the heat-resistant paint has evaporated and no moisture is visible. In the pencil hardness test, a painted surface with a hardness of "B" or higher is judged as normal, and one with a hardness of "2B" or lower is judged as defective.

[0038] From the measurement results, the laser irradiation temperature was extracted for samples that were judged to be normal by both the visual inspection and the pencil hardness test. As a result, it was found that the irradiation temperature range suitable for drying the coating film 10A with a film thickness of 17.5 μm to 22.5 μm is 150 to 270 degrees as mentioned above.

[0039] Furthermore, from the above measurement results, as shown in Figure 4A, the laser output and scanning speed for samples that were judged to be normal by both the visual inspection and the pencil hardness test were extracted as conditions for keeping the laser irradiation temperature within the above irradiation temperature range (the non-defective range shown in the figure).

[0040] As a result, it was found that, among the laser irradiation conditions, the laser output should be in the range of 460 W to 2800 W, and the scanning speed should be in the range of 0.5 to 6 m / s. The relationship between the irradiation temperature (Y), scanning speed (X1), output (X2), and film thickness (X3) obtained from the above measurement results can be expressed by the following multiple regression equation.

[0041]

number

[0042] Furthermore, since the irradiation temperature changes depending on the laser output and scanning speed, if "output ÷ scanning speed" is taken as one parameter in the above measurement results, the irradiation temperature changes in proportion to "output ÷ scanning speed" as shown in Figure 4B.

[0043] Therefore, if the irradiation temperature is Y and "output ÷ scanning speed" is X, the relationship between the irradiation temperature (Y) and "output ÷ scanning speed" (X) can be expressed by the following simple regression equation through simple regression analysis. In Figure 4B, R2 is called the coefficient of determination or contribution rate, and is a parameter that indicates the accuracy of the simple regression equation.

[0044]

number

[0045] [effect] According to the drying equipment 1 of this embodiment, the heat-resistant paint applied to the automobile muffler 10 can be satisfactorily dried and cured by operating the mounting table 20 and the drying robot 30 so that the laser irradiation temperature, scanning speed, and output satisfy the irradiation conditions shown in FIG. 2.

[0046] Therefore, there is no need to use a drying oven to dry and harden the heat-resistant paint applied to the automotive muffler 10, and energy consumption such as electricity and gas (and ultimately CO2 generation) can be reduced compared to when a drying oven is used. Therefore, according to this embodiment, an environmentally friendly drying facility can be provided.

[0047] [Other embodiments] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0048] For example, in the above embodiment, the coating film 10A of the automotive muffler 10, to which heat-resistant paint has been applied in the painting process, is described as being dried using a laser in the drying equipment 1 shown in Fig. 1. However, because the heat-resistant paint contains resin and solvent, if the coating film 10A is irradiated with a laser immediately after painting, there is a risk that the volatile solvent contained in the coating film 10A will ignite.

[0049] Therefore, it is desirable to dry the surface of the coating film 10A before irradiating it with the laser in the drying equipment 1. In this case, if the coating film 10A is allowed to dry naturally, the waiting time from the painting process to the drying process in the drying equipment 1 becomes long, and the production efficiency of the automotive muffler 10 decreases.

[0050] 5, between the painting process and the second drying process by laser irradiation in drying equipment 1, a first drying process may be carried out in which a blower is used to blow air onto the coating film 10A, thereby forcibly evaporating the solvent on the surface of the coating film 10A and drying it. In this way, drying by laser irradiation can be carried out in a short time after the application of the heat-resistant paint, thereby improving the production efficiency of automotive mufflers 10.

[0051] Next, in the above embodiment, the drying equipment 1 has been described as including the mounting table 20 and the drying robot 30, but this configuration is merely an example. In other words, the drying equipment used to realize the drying method of the present disclosure may be configured to dry the entire coating film 10A of heat-resistant paint by scanning it with a laser.

[0052] Furthermore, in the above embodiment, the drying equipment 1 has been described as drying the coating film 10A of heat-resistant paint applied to the automotive muffler 10, but it may also be used to dry the coating film 10A of heat-resistant paint applied to a member other than the automotive muffler 10. In other words, the drying method of the present disclosure can also be applied to the case of drying the coating film of heat-resistant paint applied to a member other than the automotive muffler 10.

[0053] Furthermore, the experiments conducted to set the laser drying conditions in the above embodiment are merely examples, and the drying conditions may be set under stricter quality conditions by changing the sample material, the components of the heat-resistant paint, the thickness of the coating film, etc., in accordance with the actual coating conditions. Note that even in this case, the drying conditions will fall within the above range.

[0054] The drying method of the present disclosure can also be realized in various forms, such as drying equipment, a system for driving and controlling the drying equipment, a computer program for controlling this system, and a non-transitory tangible recording medium such as a semiconductor memory on which this program is recorded.

[0055] [Technical idea disclosed in this specification] [Item 1] A method for drying a heat-resistant paint, comprising irradiating a surface of a member coated with a heat-resistant paint with a laser and scanning the irradiation position to dry the coating film of the heat-resistant paint, The laser irradiation conditions are a temperature heated by the laser of 150 to 270 degrees, a scanning speed of the laser of 0.5 to 6 m / s, and an output of the laser of 460 W to 2800 W.

[0056] [Item 2] The method for drying a heat-resistant paint according to Item 1, wherein the surface of the coating film is dried by blowing air before irradiating the laser under the irradiation conditions. [Item 3] The method for drying a heat-resistant paint according to Item 1 or 2, wherein the component is an automobile muffler. [Explanation of symbols]

[0057] 1...drying equipment, 10...automotive muffler, 10A...paint film, 20...mounting table, 30...drying robot, 50...head.

Claims

1. A method for drying a heat-resistant paint, comprising irradiating a laser beam onto a surface of a member to which the heat-resistant paint has been applied, and scanning the irradiation position to dry a coating of the heat-resistant paint, The laser irradiation conditions are: The temperature heated by the laser is 150 to 270 degrees, The scanning speed of the laser is 0.5 to 6 m / s; The output of the laser is 460 W to 2800 W; This is a method for drying heat-resistant paint.

2. 2. The method for drying a heat-resistant paint according to claim 1, wherein the surface of the coating film is dried by blowing air before irradiating the laser under the irradiation conditions.

3. 3. The method for drying heat-resistant paint according to claim 1, wherein the component is a muffler for an automobile.

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