JPH02135179A - Coating method - Google Patents

Abstract

PURPOSE:To reduce the swelling of a paint on the end of a material to be coated by depressing the part corresponding to the edge of the material from other parts before the surface of the material is coated with the paint in the thickness beyond the sagging limit. CONSTITUTION:The material W is coated with a paint in the thickness beyond the sagging limit, and the coating film in the thickness beyond the sagging limit is then dried. The material W is rotated on its almost horizontal axis in the drying stage until the coating film is cured and sagging is not caused. Furthermore, the part T of the surface 105 of the material W to be coated corresponding to the edge of the material W is depressed from the other parts in the coating stage before the part 106 is sprayed in the thickness beyond the sagging limit. As a result, a high-quality coating surface having high smoothness is obtained by utilizing the fluidity and rotation of the paint. In addition, the swelling of the paint on the edge of the material due to the coating beyond the sagging limit is reduced.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a coating method. (Prior art) When painting the outer surface of an object to be painted, such as an automobile body, there are a preparatory step to remove dust adhering to the object, a step to spray paint onto the object, and a step to remove the sprayed paint. It has a drying step of drying. This drying process is generally carried out in two stages: a setting process and a baking 1.1 process. As it is called, it is carried out in a temperature atmosphere of 40°C to 60°C (baking moisture level in the baking process is usually around 140°C). The object to be coated is usually conveyed by means of transportation such as a trolley while going through the above preparation process, painting process, and drying process. It is still being done. By the way, one of the criteria for evaluating the quality of painted surfaces is:
It has a degree of smoothness (moatness), and the higher the smoothness, the less uneven the painted surface is, resulting in a better painted surface. It is already known that in order to improve the smoothness of the painted surface, it is sufficient to increase the thickness of the paint film, that is, the film thickness of the applied paint. On the other hand, something that impedes the quality of the painted surface is paint sagging.This sagging occurs when the applied paint flows downward under the influence of gravity, resulting in a thin film of paint applied at one time. The cause of this "sagging" that tends to occur in thick culms is ultimately the effect of gravity, so it tends to occur on surfaces that extend in the vertical direction of the object to be coated, that is, so-called vertical surfaces. Therefore, on surfaces extending in the horizontal direction of the object to be coated, that is, so-called lateral surfaces, where the amount of paint sag is less of a problem, the thickness of the paint applied can be made larger than on the vertical surfaces. In addition, even if the thickness of the paint film on the horizontal surface and the thickness of the paint film on the vertical surface are the same, the unevenness on the horizontal surface will be reduced due to slight flow of the paint that does not cause sagging.
This results in better smoothness than in the vertical plane. From the point of view mentioned above, in the past, in order to obtain a painted surface with as much smoothness as possible while preventing the paint from sagging,
Painting was done using a paint with as little fluidity (low viscosity) as possible. The so-called sag limit, at which paint sag occurs on the vertical surface, was a maximum coating film thickness of about 40 am for conventionally widely used thermosetting paints. For example, in the case of thermosetting paints, sag in the paint tends to occur at the beginning of the setting process and the beginning of the baking process, especially at the beginning of the baking process. The thickness of the paint is determined, and the maximum value of this determined thickness, that is, the sagging limit value, is about 40 um.Therefore, if you want to obtain a painted surface with even greater smoothness,
In conventional painting methods, it has been necessary to repeat a series of steps from the painting process to the baking process multiple times, for example, by applying two coats. (Problems to be Solved by the Invention) Overcoming the sagging limit that is a problem when painting by spraying as described above, it is possible to overcome the problem of the sagging limit when painting by spraying as described above, and to achieve a coated surface with superior smoothness if the thickness of the paint film is as low as 100%. The applicant has developed a coating method that allows the following to be obtained. In other words, after spraying the paint onto the object to a film thickness that exceeds the sag limit, the object is sprayed around the approximately horizontal axis at least until the paint is cured to the point where no sag occurs on the painted surface of the object. We have developed a coating method that rotates the According to this method, the action of gravity, which is the fundamental cause of sagging, is actively used to prevent the paint from sagging by appropriately changing the direction of gravity acting on the paint applied to the object. By making full use of the fluidity of the paint, a coated surface with a high level of smoothness can be obtained. However, when implementing the above-mentioned painting method, contrary to the conventional method, a highly fluid paint is applied beyond the sag limit, which may cause the problem that the paint bulges at the edges of the object to be coated. found. When considering this problem with reference to Figures 28 to 30, as shown in Figures 28 and 29,
Paints with high fluidity are affected by surface tension (
In the figure, the direction of action is indicated by an arrow), and the flow smoothes the unevenness of the painted surface. However, once the coating surface has been smoothed, as shown in FIG. 30, surface tension acts in one direction (in the illustrated direction of arrow E) toward the end T of the object W to be coated. The paint concentrates toward the edge T of the object W to be coated, and a paint buildup phenomenon 100 occurs (hereinafter referred to as edge pooling). The larger the fluidity of the paint and the thicker the paint film, the larger the edge pool becomes, resulting in a loss of appearance. In other words, even though a highly smooth painted surface has been obtained by actively utilizing the fluidity of the paint, the presence of large ridges in some areas has a significant impact on the appearance. . SUMMARY OF THE INVENTION Therefore, the object of the present invention is to suppress the bulges on the painted surface that occur before the 5th section in a painting method that uses spraying of paint above the sag limit and rotation of the object to be coated about a substantially horizontal axis. The objective is to provide a coating method that (Means and operations for solving the problems) In order to achieve the above-mentioned object, the present invention has the following configuration. That is, it includes a coating process in which the paint is spray-coated onto the object to be coated to a thickness that is above the sag limit, and a drying process that dries the coating film that has been made thicker than the sag limit. The object to be coated is rotated around a substantially horizontal axis until the paint film, which is thicker than the limit, does not sag. The surface of the workpiece before being coated has a structure in which the part corresponding to the edge part of the workpiece is lower than the other parts. Areas where sagging is likely to occur are made lower than other areas before the paint film is sprayed to a thickness that exceeds the sag limit, so the thickness of the paint film that is more likely to sag than the sag limit is obtained after drying. The painted surface will not swell up significantly at the edges. Before spraying the paint to a thickness that exceeds the sag limit, lower the part of the surface to be coated that corresponds to the edges in advance. This can be done, for example, by processing the object itself to make the area corresponding to the edge lower than the other areas. In this case, the coating itself is In addition, during the painting process, before spraying the paint to a thickness that exceeds the sag limit, it is possible to spray the edges of the surface of the object to be painted. Parts may be coated with a thinner coating than other parts.In other words, in this case, in condition iii, where the paint is sprayed to a thickness greater than the sag limit, the coating may be coated on the object beforehand. However, it is only necessary to make the coating film thickness at the edge portion of the object to be coated thinner than the coating film thickness at other portions of this pre-formed coating film. When spraying paint to a thickness that exceeds the sag limit, 1
It is possible to achieve the thickness below the sag limit by spraying once, but it is also possible to achieve the thickness above the sag limit before the final spraying by dividing the spray into two or three or more times (multi-stage spraying). Blowing). If the thickness is to exceed the sag limit before the final spraying by multiple spraying, the thickness of the paint film formed by spraying at the stage before the thickness reaches the sag limit or more, It is preferable that the edge portion be thinner than the pond portion. The above-mentioned paint may be sprayed by electrostatic coating, which particularly tends to cause edge buildup. Also, paint sag refers to the movement of paint that can be visually confirmed when the paint is left in the sprayed state (it appears as a part when the paint hardens), and is generally referred to as sagging.
Sagging is considered to have occurred when paint movement of about mm is confirmed. Therefore, spraying paint to a thickness that exceeds the sag limit means that the thickness must be such that if left as is, the paint will move by at least 2 mm, and the more fluid the paint used, the more the sag limit. becomes smaller. Furthermore, the rotation of the object to be coated around a substantially horizontal axis should be done in such a way that the paint does not move significantly due to the action of gravity, so the rotation should be done until the paint no longer has a large fluidity state that will not cause sag. between, i.e.
Until the paint hardens, rotation may be performed continuously in one predetermined direction, or forward and reverse rotation may be performed continuously or intermittently. As for the rotation angle range of the object to be coated, it is sufficient that the direction in which gravity acts is reversed for any part where the paint is sprayed to a thickness exceeding the sag limit, and 270 degrees is sufficient. . The axis of rotation of the object to be coated may be inclined within a range of about 30 degrees with respect to the true horizontal axis, and this axis of rotation may also be swung. (Example) Hereinafter, an example of the present invention will be described based on the attached drawings. Overall W1 Figure 1 shows the overall process when painting an automatic heavy duty body W as an object to be coated, and each process is indicated by PI-P4. First, the body W, which has been undercoated by electrodeposition coating in a known manner, is sent to the preparation step PI while being held on a trolley. In this /41-preparation step P1, dust inside and outside the body W is removed by, for example, air blowing or empty suction. After that, in step P2, paint is sprayed onto the body W. Then, the paint is dried in a setting step P3 and a baking step P4. If the steps P1 to P4 are for intermediate coating, the body W is sent to the top coating step after step P4. Also, process P
If 1 to P4 are for topcoating, the body W is transported to an assembly line in a known manner. Dust removal in the dust removal step PI is performed while rotating the body W around the horizontal axis Q, as shown in FIG. That is, for example, first, the rotation of the body W is stopped in the state shown in FIG. 2(a) to remove dust, and then the dust is removed as shown in FIG. 2(b).
The posture of the body W is changed to the state shown in FIG. 1, and the dust is removed again at this position. In this way, dust is removed while the body W is intermittently rotated as shown in (c), (d), . . . (i) in FIG. In this way, by removing dust while rotating the body W, it is possible to remove dust that has adhered to the closed cross section of the inner surface of the roof panel or side sill, for example, by rotating the body W. It becomes possible to completely remove even the garbage that does not fall. Spraying and Drying of Paint First, in the example, the spraying of paint in P2 causes sag in at least one of the drying steps P3 or P4, and the painted surface does not sag for at least 2 minutes after painting is completed. This is done using paints such as: The paint that causes this phenomenon varies depending on its film thickness, viscosity, and the content of the anti-sagging agent, and is not fixed in any way. This value of 2 minutes corresponds to the fact that it takes less than 2 minutes from the start of painting on one body W until the painting is completed over the entire body (including transition to setting step P3). More specifically, one body W
On the other hand, until the entire painting is completed before the entire painting is completed, the purpose is to prevent sag from occurring in the part where the painting is completed earliest, thereby reliably preventing the occurrence of sagging in the painting process P2. The thickness of the coating film can be made thicker than the conventional limit since sagging may occur during the drying step P3 or P4. Of course, it is possible to make the thickness the same as before or thinner than the conventional one. Applying the paint by spraying makes it possible to control the thickness of the paint film as desired. This is because the concept of spraying includes electrostatic painting (electrostatic atomization painting).On the other hand, (1i p p i n
The paint is applied by g (well, di).
When the object is lifted up from the pipping tank, a much larger movement of paint occurs, exceeding 1 to 2 mm by visual inspection as described above. If the paint is applied to a level exceeding the sag limit and then rotated after a -degree sag occurs, even after subsequent rotations, the painted surface where the -degree sag occurs will be replaced by another painted surface that does not sag. It is not possible to obtain such smoothness. After P2, the paint adhered to the body W is moved to the setting process of P3 without dripping. In this setting step P3, the body W is rotated horizontally as shown in FIGS. 2(a) to 2(i). That is, the body W is rotated about a rotation axis 2 that extends in the horizontal direction, and in the embodiment, this rotation axis a extends in the front-rear direction of the body W. The rotational speed of the body W varies depending on the film thickness and viscosity of the sprayed paint, but in front of Hanawamoto, the rotational speed is set within the range between the lower limit and upper limit as shown below. . That is, the lower limit of the rotational speed is the minimum value of the rotational speeds at which the painted surface can be at least changed from a vertical state to a horizontal state before the paint on the surface moves with a small force and sag. Further, the upper limit value is the maximum value of the rotational speed at which sagging does not occur due to the centrifugal force generated by rotation, but it is preferable that the rotational speed is 380 cm/sec or less at the rotation tip position. Note that when the body W is rotated around a substantially horizontal axis, the rotation axis may be inclined by about 30' with respect to the horizontal axis, but preferably this inclination is within 10'. The period during which the body W is rotated around the approximately horizontal axis is as follows:
At least in the drying step, it may be from before sagging occurs on the coated surface until it is cured until no sagging occurs. Of course, the object to be coated may be rotated throughout the drying process depending on the equipment and the like. Further, this rotation may be continuous rotation in one direction, forward/reverse rotation that alternates forward rotation and rotation, or intermittent rotation with a rotation stop period in between. Note that the temperature atmosphere in this setting step P3 is set to room temperature in the example, but it may be set to an appropriate temperature in a lower temperature range than the temperature atmosphere in the next baking step P4, such as 40° to 60°C. It is possible. Of course, this setting process P3
This is to volatilize the low-boiling point components in the paint in advance, thereby preventing the generation of pinholes on the painted surface due to the rapid volatilization of the low-boiling point components in the next baking step P4. In the baking step P4, the paint is baked in an atmosphere at a temperature of, for example, 140°C. Even in this P4, P
2 (a) to (i)
The body W is rotated in the horizontal direction as shown in FIG. The horizontal rotation of the body W at P3 and P4 described above dries the paint without causing any sag. As a result, a high-quality coated surface with extremely high smoothness that could not be obtained with conventional coating methods can be obtained. Relationship between paint film thickness, sag limit, beach smoothness, and manual rotation Figure 3 shows the effect of film thickness on the sag limit. In this Figure 3, the coating film thickness is 40um,
Three cases of 53 g m and 65 u'm are shown. It is understood that for any of these thicknesses, peaks of "-sag" occur both at the initial concavity in the setting process and at the baking process.Also, the sag limit is 1 to 2 mm during the drying process. This is the value when the paint sag during the drying process from the point where it adhered.
This is the limit of the paint film thickness at which traces of paint movement can be seen on the painted surface after drying by moving ~2mm)
The maximum coating thickness that can be obtained within the range below this sag limit is about 35 to 40 um with conventional paints. On the other hand, FIG. 4 shows the influence on the smoothness when the body W is rotated in the horizontal direction and when it is not rotated. A in FIG. 4 shows a state in which the body W is not rotated (conventional painting method). FIG. 4B shows the case where the body W is rotated 90' and then reversed (second
Forward/reverse rotation between figures (a) and (c)). Figure 4C is
This figure shows a case where the body W is rotated by 135 degrees and then reversed (forward and reverse rotation between FIG. 2(a) and FIG. 2(d)). The fourth diagram shows the case where the body W is rotated tso' and then reversed (forward and reverse rotation between FIGS. 2(a) and (e)). FIG. 4E shows the case where the body W is continuously rotated in the same direction (FIGS. 2(a), (b), (
c)... Take the posture in the order of (i) and return to (a) again). As is clear from Fig. 4, if the thickness of the coating is the same, it is better to rotate the body W (Fig. 4 B, C, D, E).
), thicker smoothness can be obtained than in the case of no rotation (FIG. 4A). Furthermore, it is understood that even if the rotation is the same, it is preferable to rotate 360 degrees in the same direction in order to improve the smoothness. Of course, if the body W does not rotate,
Since there is a limit to the thickness of the coating film, there is a limit to how much smoothness can be increased. By the way, if the thickness of the coating film is 65 am and the body W is rotated 360 degrees, the result is obtained! I7-Smoothness is the image sharpness 1. G is rg7J (lower limit of PGD value of 1.0). In addition, when the thickness of the coating film is 40 μm, when the body W does not rotate, f and G are r58
J (1) G D (lower limit of 0.7 in direct view), whereas when body W is rotated 360°, it is 1. G
and r68J (lower limit of PGD value of 0.8). As is known, IG (Image Cross) in image sharpness indicates the ratio of sharpness to mirror surface (black glass) as 100. This is a value at which the smoothness of the painted surface decreases as the degree of discrimination decreases from 1.0. The test conditions for the data shown in FIGS. 3 and 4 are as follows, and this test &14= indicates the same conditions as when -F painting is performed at P2. a, Paint: Melamine alkyd (black) Viscosity Koford cup #4, 22 sheets/20°C b, Coating machine: Minibell (16, OOOrpm) Shaving air -2,0 kg/cmz C1 discharge sparrow: divided into 2 times First time spraying...
l0Occ/min 2nd time 150-200cc/min, Cerading time: 10 minutes x constant drying, Baking conditions: 140°C x 25 molecules, Base
Severity: 0.6 (PGI) (intermediate coating, PE
(on tape) g0 Rotation or reversal operating range: Setting (10 minutes) to baking (10 minutes) h, Painted on the side of a rectangular cylinder with a knee side of 30 cm, Supported rotatably in the center i, Worked object Rotation speed: 6rpm, 30rpm, 60r
pm, but there was virtually no difference in performance due to the difference in rotational speed.In the case of the paint shown in Figure 3, especially the one coated with a thickness of 65 μm, there was a
If it starts to shake within minutes and rotates immediately after painting is completed, there is no problem, but if you do not have equipment that can rotate it immediately after painting, it will move from the painting process to the setting process. There is a risk that blurring may occur during the time it takes (approximately 1 minute). (Left below) Tamayu”koL

[Size]' 14 As a result of experiments, the edge reservoir 100 is closely related to the paint used and the thickness of the coating, and if these are constant, the thickness H and width X of the edge reservoir 100 are almost constant. Something became clear (see Figure 30). That is, the test results conducted using the automatic tontanaka coating paint and the -hi coating paint are shown in Table 1 below. (Hereinafter, blank space) From the above test results, in order to make the edge pool 100 visually inconspicuous by forming a step on the body W, the edge pool 1
It is sufficient to provide a step with a depth of 015 mm or less and a width of 5 mm or less at the location where 00 occurs. Appearance of the Ir'-type acid forming device One step was formed in the window washer nozzle mounting hole lot and the ornament mounting hole 102 of the bonnet W' shown in FIG. 16, and its curing was tested. That is, as shown in FIG. 17, the window washer nozzle mounting hole 101
A stepped portion 101a (depth 05
Inn+, width 4mm+), and as shown in FIG.
I set this up and actually applied the paint to a level that exceeded the sagging limit. The conditions for the coating experiment were as follows. (1) Base coating cationic electrodeposition 20μm Baking at 175℃ x 30 minutes (
2) Intermediate coating: 40um, baked at 140℃ for 25 minutes (thermosetting oil-free polyester paint; gray) Intermediate coating: #800 waterproof paper (3) Topcoat: thermosetting melamine alkyd paint (black) Spraying viscosity
22 seconds/Ford Cup #4.20℃ (4) Topcoating conditions ■ Painting machine Mini Bell (bell TL = 60 mm) Rotation speed 22.00 Orpm, Voltage -90 KV Shaving air pressure 3.0 kg/cm2 Gun distance 30 cm ■Position for spraying: Set the bonnet horizontally ■Number of stages: 2 stages (interval: 3 minutes) ■Booth environment: Temperature: 20℃ Wind speed: 0.2m/sec ■Baking conditions: Setting 10: 140℃ x 25 minutes (heating rate: 8 minutes) /20℃→140℃)
■ Film thickness level (μm) 40 50 60 70 30 (Dry film thickness) The experimental results are as shown in Table 2) and Table 3 below. still,
Table 2) In Table 3, the conventional structure refers to one in which a step is not provided at the periphery of the opening end of the window washer nozzle attachment hole 101, etc. (Hereinafter, blank space) Table 2) As is clear from Table 3, the stepped portions 101a, 1
According to the stepped structure provided with 02a, it was possible to visually make the buildup of paint due to edge accumulation less noticeable. Other Examples (FIGS. 19 to 27) In the examples described below, the prevention of edge accumulation is carried out from the viewpoint of coating film formation. That is, in the stage of forming the coating film before the coating thickness is increased to the sag limit or more before final coating, the coating thickness at the edge portions is formed to be thinner than the coating thickness at other portions. To form a thin film on the edge part, for example, use the following methods 1 to 4. First, the first method is to spray paint onto the surface of the body W using a paint gun. In this case, the coating gun is not allowed to come near the edge portion T. As a result, as shown in FIG. The thickness of the coating film 105 is made thinner than the film thickness of other parts. When a coating film 106 is applied to a thickness of more than the sag limit on the coating film 105 as shown in FIG. (See Fig. 20), and as shown in Fig. 21, the thickness of the coating film 100 below the edges of this coating film 106 obtained after drying is approximately the same thickness as the other parts, and no edge accumulation occurs ( Even if this occurs, it will not cause any problem in terms of appearance.) As a second method, as shown in Fig. 22, from the edge portion T of the body W as the object to be coated, to the vertical surface of the body W, The masking 111 is placed higher than the side surface, and the upper end of the masking 111 is bent so as to cover the edge portion T from above.In this state, the coating gun 112 is moved as shown in FIG. While displacing the body W in the left and right direction,
A coating film 110 is formed on the surface of. At this time, paint gun 1
12 is located near the edge portion T, the painting gun 1
The paint sprayed from 12 is blocked by the masking 111, and the thickness of the paint film 110 at the edge portion T is made thinner than that of other parts (the paint film 110 is different from the paint film 105 in FIG. 19). formed in the same way). Note that the masking 111 is preferably made of a material that can absorb paint and is made of a sweat layer so that the paint adhering to it does not drip onto the body W (below the edges thereof). As a third method, as shown in FIG. 23A, the surface of the edge portion T is completely covered with a thin masking 202, and then a coating film 201 is formed using a coating gun. This coating 1
If the masking 202 is removed after the formation of i201,
A film in which the coating thickness at the edge portion T is zero is obtained. In this way, the case where a coating film 203 having a thickness exceeding the sag limit is formed on the iU rough coating film 201 is as follows.
It is shown in FIG. 23B (edge accumulation prevention +h). As a fourth method, as shown in FIG. 24A, the coating film 2
11, the thickness of the coating film 100 at the edge part T is the same as that of other parts, or the thickness (formed (same as conventional method))
. After this coating film 211 is cured, as shown in FIG. 24B, the coating film 100 at the edge portion T is removed by scraping the coating film 100 below the edge with sandpaper 212.
The thickness of the coating film 100 (after being scraped) is made thinner than other parts. In this case, it is necessary to sand the coating film 100 with the sandpaper 212, but the thickness of the edge portion T is not taken into account when forming the coating film 211.
It has the advantage of being unnecessary. This is advantageous when the thickness of the coating film 211 is greater than the sag limit. Of course, the second
The coating film 211 in FIG. 4B is in the same state as the coating film 105 in FIG. 19. Note that instead of using the sandpaper 212, polishing may be performed using a grindstone, a compound, or the like. Next, when spraying paint to a thickness that exceeds the sag limit,
With one spray or multiple sprays of two or more times,
The thickness may be adjusted to be at least the desired sagging limit before the final step. For example, when spraying paint twice to a thickness that exceeds the desired sag limit, the coating thickness from the first spraying should be within the sagging limit, and the coating thickness from the second spraying should be The thickness can be greater than the sag limit. An example of this case is shown in FIG. In FIG. 25, a top coat is sprayed onto the cured intermediate coat 221 to a thickness within the sag limit to form a first top coat 222. Then, before this first top coat 222 is cured (while in a wet state), a second top coat 223 is formed by spraying a top coat to a thickness greater than the sag limit. In addition, as another method, the thickness may be divided into two times to reach a desired sag limit or above, but the thickness may be within the sag limit in both the first and second sprayings. An example of this case is shown in FIG. In FIG. 26, a top coat is sprayed onto the hardened intermediate coat 221 to a thickness within the sag limit to form the first top coat 221.
form 2. Then, before the first top coat 222 is cured (during the wet state), a second top coat 223 is formed by spraying the top coat to a thickness within the sag limit. Of course, in Figure 26, both top coats I! 222 and 22
The total film thickness of 3 and 3 is the film thickness that is equal to or greater than the sag limit. In both the cases of FIG. 25 and FIG. 26 above, the first top coat film 22
2, the thickness at the edge portion T of the body W is made thinner than the thickness at other portions to prevent edge accumulation. In the cases shown in FIGS. 25 and 26, the thickness below the edge of the intermediate coating film 221 may be made thinner than the other portions (in this case, 1. The thickness of the top coat 222 may be made uniform over the entire surface.As can be understood from the above explanation, there is a method in which the thickness of the coating film below the edge is made thinner than the thickness of the coating film in other parts. ,
The method of spraying the paint to a thickness above the desired sag limit before final coating and the selection of which paint layer is to be thinned below the edge can be combined as appropriate. Next, the present invention will be explained in more detail with reference to test examples. In this test example, as shown in FIG. 27, an intermediate coat layer IC is formed on the surface of the body W on which the undercoat has been completed (the undercoat layer is the path shown in the figure). A top coat layer OC is formed. Then, measure the dimensions a = d and H (edge pool width) of each part, and
This is to determine the quality of the appearance of the painted surface obtained before final coating, especially the quality of the appearance below the edges. In addition,
The dimensions C and () are at the m-point position of the swell of the paint.The paints used in the above test examples are thermosetting paints (solvent-containing paints), two-component reactive paints, and powder paints. There are three types of body paints.In addition, there are intermediate coat layers IC and -Nana film layers OC.
The formation method was carried out in the following five ways (1) to (2). ('D Intermediate coating layer IC is sprayed to a thickness within the sag limit, so that the coating thickness at the edge portion T is thinner than other parts. Also, the top coating layer OC is sprayed once. In other words, this ■ corresponds to Figures 19 to 21. ■ The intermediate coating layer IC is sprayed to a thickness that is within the sag limit. In this case, the thickness of the coating film below the edge is set to zero.Furthermore, the thickness of the overcoat film layer OC is set to be greater than the sagging limit with one spraying.In other words, in this Figure 23B. ■ Middle r! IAφ film layer IC is sprayed to a thickness exceeding the sag limit, and after curing, the intermediate coat film below the edge is scraped. Also, the top coat film layer OC is When sprayed, the thickness is greater than the sag limit.This ■ is shown in Figures 24A and 24B.
20 and 21. ■The thickness of the intermediate coating layer IC is within the sag limit, and the 1 m thickness of the edge portion T is not actively made thinner than other portions (painting according to the usual method). Moreover, the top coat layer OC is formed by spraying twice. The first top coat is sprayed to a thickness within the sag limit, and the coating film thickness at the edge portion T is thinner than the thickness at other portions. Then, spraying the second top coat of paint,
The first top coat is applied while the paint is still wet, with a thickness that is above the sag limit. This ■ corresponds to FIG. 25. ■The intermediate coating film layer IC is the same as in the case of ■ above.
The top coat layer OC is formed by spraying twice,
The first top coat is sprayed to a thickness that is within the sag limit, and the coating film thickness below the edge is thinner than other parts. The second top coat is sprayed to a thickness within the sag limit, and is performed while the first top coat is still wet. Then, by spraying the top coat twice, the thickness of the top coat layer OC is made to be more than the sag limit before the final coating. This ■ corresponds to FIG. 26. The test examples mentioned above are summarized in Tables 4 to 6 below, with Table 4 for thermosetting paints, Table 5 for two-part reactive paints, and Table 5 for thermosetting paints. Table 6 shows the case of powder coating. In Tables 4 to 6 above, the conventional method is the case where the film thickness of the edge portion T is not treated to be thinner than the other portions. In addition,
The calculation formula for each dimension a to d is (c+d)-(a
If the value of +b) is 150 JLm or less, the appearance will be good. (Hereinafter, blank spaces) In Tables 4 to 6 above, the details of the coating conditions according to each type of paint are as follows. Thermosetting paint (1) Intermediate coating a, Paint: Thermosetting oil-free polyester paint (gray) Spraying viscosity 22 paper/Food cup #4.20℃ b, Painting machine Minibell (bell diameter 60mm) Rotation t12
200 Orpm Voltage-90KV Shaving Air Pressure 3. 0 kg/am 2 Cancer? iI 30 crm C6 drying conditions: 10 minutes after setting (room temperature), 14
0°C x 25 minutes (2) Top coat a, 41'4: Alkyd melamine Hytsurilad thermosetting paint (main resin common average molecular weight JII: 2800: Hue Niblack) b, Spraying viscosity: 20 seconds (Ford Cup #4/ 20℃) C3 non-volatile content: 48% by weight d, Solvent: Toluene = 25 parts by weight/Tsurupez 1
00: 25 parts by weight / Tsurupetz 150: 50 parts by weight e, anti-sag agent 1L double-crosslinked acrylic resin powder; 3% by weight based on non-volatile content) f, coating coater: Minibell (bell diameter 60mm: Nippon Landsburg Rip) ) Mini bell rotation speed: 1600 rpm Shaving pressure: 3 kg/cm 2 voltage: 90 KV Gunning fi: 30 cm For 2 sprays, interval 5 minutes g, spray atmosphere: Temperature 20°C ± 2°C Booth wind speed 0.3 ± 0 .1m/sec
Pull down flow h, Setting conditions: Setting start temperature 20℃±
2℃/setting time 10 minutes i, baking conditions: temperature 140℃/time 25 minutes culm temperature speed: 8 minutes (20℃→140℃) j1 rotation condition horizontal 75cm away from the center axis of the object to be coated The object to be coated was rotated about the axis so that both end surfaces were parallel. The rotation speed is 6 rpm. Curing agent: Hexamethylene diol Mixing ratio (weight ratio): Ratio of 1 part curing agent to 4 parts main resin. Painting machine: Pressure-feeding spray gun (manufactured by Iwata Painting Machine Co., Ltd., trade name Wipe-W71) C1 spraying Viscosity: 16 seconds/Ford Cup #4, 20℃ d, atomization air pressure + 4.0kg/am 2e, spraying distance: 30cm f, drying conditions: 90% after setting 10 minutes (room temperature)
℃ x 25 minutes 21 nights Reactive paint (1) Intermediate coating a, paint main resin polyester urethane paint (hue gray, manufactured by Nippon Sha B Chemical Co., Ltd., product name PO26): Polyester polyol, (2) Top coating a , Paint main resin: Polyester urethane paint white (manufactured by Nippon B Chemical Co., Ltd., product name P-263): Polyester polyol white Curing agent: Hexalmethylene diisocyanate Mixing ratio (1,000-forger ratio): 4 to main resin Ratio of curing agent: Torn damage: Pressure-feeding air spray gun (manufactured by Yoshikawa Painting Machine Co., Ltd., product name: Wider W71 C8 spraying, viscosity: 16 seconds/Ford cup #4d, coating I
2 + discharge + 2: 350c/min e, atomization air pressure:
4, Okg/cnI2f, spraying distance i1! I:3
0cm g, 5 minutes interval for 2 coats, drying conditions: Setting 10 minutes (room temperature) 90℃ x 25 minutes (#Drying speed 5 minutes (20℃-90'C)) e9 Rotation speed:
Powder coating same as thermosetting paint (1) Intermediate coating a, Paint: Epoxy powder coating (manufactured by Nippon Paint (Special), trade name Parabutshu E) b, Coating machine: Electrostatic powder coating equipment (Onoda) cement(
Manufactured by Aji), product name GX 0N C1 Applied voltage knee 60KV d, Paint discharge amount: 180gr7'min e, Paint conveying air pressure: 2, Okg/c1112
f, Distance for blowing: 25 cm g, Drying conditions = 170°C/25 minutes (Serima speed 8 minutes (20°C → 170°C)) (2) - Paint a, Paint S, Paint machine C1 Applied voltage Niacrylic powder Paint (manufactured by Nippon Paint@, trade name Powdax△): Electrostatic powder coating equipment (manufactured by Ono EII Cement Co., Ltd., trade name GXIOI) Knee 60 ■ d, Paint discharge grinder: 180 gr/min e, Paint conveying air pressure : 2,0 kg/Cm2f,
Spraying distance: 25cm g, 5 minute interval for 2 coats, drying conditions
: 170℃/25 minutes (heating rate 8 minutes (20℃-170℃)) i9 rotation speed
:It requires the same amount as thermosetting pear paint, but it is undesirable because it discharges a lot of solvent.Furthermore, for latex polymers with a number average molecular weight exceeding 20,000, the viscosity increases immediately after spraying.
This is undesirable because it becomes difficult to reduce the smoothness. (The following is a blank space) Preferred paints for moving bodies Here, as shown in Table 7 below, paints used for painting automobile bodies W have a number average molecular weight of paint resin in the range of 2000 to 2000'0. preferable. The number average molecular weight is 2000 to 20 as a car paint rat.
The reason why it is preferable to use a range of 000 is that anything less than 2000 corresponds to paints that are cured by electron beams or ultraviolet rays, and these paints have a high crosslinking density and are brittle, so they are not durable (
2 to 3 years), which is not very preferable for use in automatic heavy duty outer panels. In addition, if the viscosity exceeds 20,000, the viscosity becomes high, so the solvent must be attenuated. I will explain about it. Figure 5 shows the front jig I attached to the front of the body W.
Indicates F. This jig IF includes a pair of left and right mounting brackets 2, a pair of left and right stays 3 welded to each of the left and right brackets 2, a connecting bar 4 that connects the left and right pair of stays 3, and a connecting bar 4. It has a rotating shaft 5 integrated with. The bracket 2 portion of such a jig IF is fixed to the front strength member of the body W, for example, to the front end of the front side frame 11. That is, since a bracket 12 for normally mounting a bumper (not shown) is welded to the front side frame 11, this body W
The bracket 2 is fixed to the side bracket 12 using bolts (not shown). On the other hand, the rear jig IR attached to the rear part of the body W is shown in FIG. The rear jig IR has a similar configuration to the front jig IF, and the same reference numerals are given to the components corresponding to the front jig IF. The rear jig IR is attached to the body W by fixing the bracket 2 to the floor frame 13 as a strength member at the rear end of the body W with bolts. Of course, at the rear end of the floor frame 13,
Since the bumper mounting bracket is generally welded for mounting the bumper, the rear jig IR can also be mounted using this bumper mounting bracket. When the front and rear jigs IF and IR are attached to the body W, their rotating shafts 5 are positioned on the same straight line extending in the front-rear direction of the body W. This same straight line becomes the rotational axis e of the body W, and preferably, this rotational axis C is the center of gravity G of the body W (see Fig. 7).
It is made to pass through. Note that since the rotational axis C passes through the center of gravity G, large fluctuations in the rotational speed are prevented when the body W rotates. This prevents impact from occurring on the body W due to rotational fluctuations, which is more preferable in terms of preventing sagging. Note that the front and rear jigs IF and IR are specially prepared in advance according to the vehicle type (type of body W).廿” (also used in P3 and P4, it is a trolley equipped with the function of rotating the body W. In FIG. 7, the trolley has a base 21, and this base 2
Wheels 22 attached to the vehicle 1 are run on a road surface 23. This base 21 has one front strut 24, two intermediate struts 25, 26, and one front strut 24, two intermediate struts 25, 26, and one front strut 24, two intermediate struts 25, 26, each extending in the -F direction from the front side in the running direction to the rear side (from the right side to the left side in FIG. 7). It has a rear strut 27, an intermediate strut 25, 26 and a rear strut 27.
The support space 28 is wide in the front-rear direction (spaced
It is said that The body W is disposed in the support space 28, and its front part is rotatably supported with respect to the intermediate support 26 using the front jig IF, while its rear part is supported by the rear jig IR. It is rotatably supported by the rear support 27 using the same function. The front and rear jigs IF and IR (rotary shafts 5 of them) can be freely engaged with and disengaged from the columns 26 and 27 from above and below, and the rear jig IR is immovably engaged in the direction of the rotation axis C. Ru. For this reason, the intermediate support 26 is formed with a notch 26a that opens at its upper end surface (see FIGS. 10 to 12).
, a notch 27a opening in the upper end surface of the rear strut 27 is formed (see FIGS. 1O, 14, and 15).
. Both notches 26a and 27a have a size that allows the rotating shafts 5 of the jigs IF and 1R to fit therein. A flange portion 5a is formed on the rotating shaft 5 of the rear jig 1 ['t, while a notch 27b having a shape corresponding to the flange portion 5a that communicates with the notch 27a is formed in the rear support 27. has been done. As a result, the rear jig IR is engaged with and disengaged from the notches 27a and 27b of the rear column 27 from above and below, and is made immovable in the front and rear direction with respect to the rear column 27 by the stopper action of the flange portion 5a. Ru. Note that the rotational force is applied to the body W via the rotation shaft 5 of the front jig IF, and for this reason, a connection portion 5b (see FIG. 5), which will be described later, is provided at the tip of the rotation shaft 5 of the front jig IF. (see also) is formed. A stay 29 is provided to protrude downward from the base 21,
A traction wire 30 is connected to the lower end of this stay 29. This wire 30 is of an endless type,
It is driven in one direction by a motor (not shown), and thereby the trolley is driven in a predetermined transport direction. Of course, the motor is installed in a safe location from an explosion-proof point of view. The rotation of the body W is performed by using the movement of the truck 111, that is, by using the displacement of the truck with respect to the running road surface 23. The rotation extraction mechanism 31 for extracting the displacement of the base width as rotation is configured as follows. That is, the rotary take-out mechanism 3] includes a rotary shaft 32 extending vertically 17 and rotatably supported on the base 21;
It consists of a sprocket 33 fixed to the lower end of the sprocket, and a chain 34 meshed with the sprocket 33. This chain 34 is disposed in parallel with the wire 30 in an immovable state with respect to the running road surface 23. As a result, when the truck is towed via the wire 30, the rotating shaft 32 is rotated by the sprocket 33 that meshes with the chain 34, since the chain 34 is immovable. The rotation of the rotation shaft 32 is controlled by the rotation shaft 5 of the front jig IF.
The transmission mechanism 35 for transmitting the signal is configured as follows. That is, the transmission mechanism 35 includes a casing 36 fixed to the rear surface of the inn-plane front strut 24, a rotating shaft 37 that is rotatably supported by the casing 36 while extending in the lateral direction (front-back direction), and this rotating shaft 37. a pair of bevel gears 38 and 39 that interlock the rotary shaft 32 with the rotation axis 32;
The connecting shaft 4o is rotatably held relative to the intermediate support 25 and slidably in the front-rear direction. This connecting shaft 40 is spline-coupled to the rotating shaft 37 (this engaging portion is indicated by the number 41 in FIG. 7), so that when the rotating shaft 32 is rotated, the connecting shaft 40 is also rotated. It turns out. Of course, the rotating shaft 37 and the connecting shaft 40 are connected to the rotating axis 2.
It is located at the second position. The connecting shaft 40 is connected to the rotating shaft 5 of the front jig IF.
be disengaged. That is, as shown in FIGS. 10 to 12, a cross-shaped connecting portion 5b is formed at the tip of the front jig IF rotating shaft 5, while a cross-shaped connecting portion 5b is formed at the end of the connecting shaft 40. 1
As shown in FIG. 0 and FIG.
a is formed. Therefore, for example, by sliding the connecting shaft 40 via the rod 43 by a pneumatic cylinder 42, the box portion 40a (engaging recess 40c) and the connecting portion 5b are engaged and disengaged, and when they are engaged, they are connected. The shaft 40 and the rotating shaft 5 are allowed to rotate together. In addition,
The rod 43 is connected to a connecting shaft 40 as shown in FIG.
The box part 40a is fitted into an annular groove 40b formed on the outer periphery of the box part 40a so as not to hinder the rotation of the box part 40a. With the above configuration, by lowering the body W relative to the trolley while the connecting shaft 40 is displaced to the right in FIG.
is rotatably supported by the intermediate struts 26 and 27 in a fixed manner in the front-rear direction. After this, the connecting shaft 40 (latching distance 1vT40c) is connected to the rotating shaft 5 (
is engaged with the connecting portion 5b). As a result, when the trolley is pulled via the wire 30, the body W is rotated about the predetermined horizontal axis 2. In addition, the removal of the body W from the trolley may be performed in the reverse order to the above-described procedure. The present invention has been described in detail above, but when spraying paint on the side surfaces and on the vertical surfaces as in the case of an automobile body W, so-called overspray occurs on the side surfaces near the vertical surfaces. The present invention can also be applied to the problem of partial build-up of the paint film at the boundary between The magnitude may also be determined. (Effects of the Invention) As is clear from the above description, the present invention can obtain a high-quality coated surface with high smoothness by utilizing the fluidity and rotation of the paint. In addition, it is possible to make the swelling phenomenon of the paint at the end of the object to be coated, which is caused by applying the paint more than the sag limit, less noticeable.

[Brief explanation of the drawing]

FIG. 1 is an overall process diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing a state in which the posture of an automobile body as an object to be coated changes as it rotates. Figures 3 and 4 are graphs showing the relationship between paint thickness, blurring, smoothness of the painted surface, and rotation. FIGS. 5 and 6 are perspective views showing examples of jigs used to rotate the body. FIG. 7 is a side view showing an example of a body transport trolley in which the body can be rotated. FIG. 8 is a partially cutaway plan view showing the state below the running path of the bogie. FIG. 9 is a sectional view taken along the line X9-X9 in FIG. FIG. 10 is a side cross-sectional view showing the joint portion between the rotating jig and the truck. FIG. 11 is a sectional view taken along the line X1l-X11 in FIG. 10. FIG. 12 is a plan view of FIG. 11. FIG. 13 is a sectional view taken along the line X13-X13 in FIG. 10 (7). FIG. 14 is a sectional view taken along the line X14-X14 in FIG. 10. FIG. 15 is a plan view of FIG. 14. FIG. 16 is a plan view of a bonnet, which is an outer panel member of an automobile. FIG. 17 shows an enlarged view of the window washer mounting hole formed in the bonnet,
Line sectional view. FIG. 18 is a cross-sectional view taken along the line X18-X18 in FIG. 16, showing an enlarged view of the ornament attachment hole formed in the bonnet. FIG. 19 is a sectional view showing a coating film formed in the first stage of coating. FIG. 20 is a sectional view showing the state of the coating film immediately after the completion of the second stage of painting. Figure 21 is after the second stage of painting is completed. FIG. 3 is a cross-sectional view showing a state after edge accumulation occurs. FIG. 22 is a cross-sectional view showing an example of masking applied during intermediate coating. FIG. 23A is a sectional view showing another example of masking. FIG. 23B is a sectional view showing a state in which a coating film is formed on the coating film obtained by the masking process of FIG. 23A to a thickness exceeding the sag limit. Figures 24A and 24B are cross-sectional views showing an example of thinning the edge portion with sandpaper. Figures 25 and 26 each show a case in which a coating film is formed to a thickness exceeding the sag limit by spraying twice. Fig. 27 is a sectional view showing the dimensional positions shown in the data in Tables 4 to 6. Fig. 28 to 30 show the conventional problems, and Explanatory diagram showing the generation mechanism. PI-P4: Process W: Body (object to be coated) T: End of object I2: Rotation axis 100: Edge pool of paint 101: Window washer mounting hole 101a + stepped portion 102: Ornament Attachment hole 102a: Stepped portion 105.110.201.211.222): Paint 1 layer III with thinned edge portion, 202: Masking ＼ ＼ ＼ ＼ ＼ Fig. 16 Fig. 117 Fig. 19 Fig. 20 Fig. 21 Figure 28 Figure 29

Claims (13)

[Claims] (1) It comprises a painting process in which the paint is spray-coated onto the object to be coated to a thickness above the sag limit, and a drying process in which the coating film with a thickness above the sag limit is dried. The object to be coated is rotated around a substantially horizontal axis until the coating film, which is thicker than the limit, is cured to the point where it no longer sag, and before the paint is sprayed to a thickness exceeding the sag limit in the painting process. 1. A coating method characterized in that the surface of the object to be coated in the condition described above is lowered at a portion corresponding to an edge portion of the object than other portions. (2) In claim 1, a stepped portion is formed in advance on the object to be coated, which has not been coated at all, so that a portion corresponding to the edge portion thereof is lower than other portions, This stepped portion makes the portion corresponding to the edge portion lower than other portions before the paint is spray coated to a thickness exceeding the sag limit. (3) In claim 1, the object to be coated is coated in advance, that is, a coating film is formed, before the painting step, and the object to be coated is coated before the painting step. Among the coating films formed, the portions corresponding to the edges of the object to be coated are lower than other portions. (4) In claim 3, the coating film applied to the object to be coated before the coating step is
Formed by spray painting. (5) In claim 4, the spray coating performed before the painting step is such that the coating thickness on the edge portion of the object to be coated is thinner than the coating thickness on other portions. what is done. (6) According to claim 5, the spray coating performed before the painting step is performed so that only the film thickness on the edge portion of the object to be coated becomes zero. (7) In claim 3, the spray coating performed before the painting step has a film thickness at a portion corresponding to the edge portion of the object to be coated that is equal to or greater than the film thickness at other portions. After the paint film formed by the spray coating performed before the above painting process has dried, and before the above painting process, the coating of the part corresponding to the edge part of the object to be coated is applied. Something that is scraped to make the membrane thinner. (8) In claim 3, after the paint film formed by spray painting performed before the painting process is dried, the spray painting is performed in the painting process so that the film thickness is greater than the sag limit. What is done. (9) In claim 8, the paint used in the spray painting performed before the painting step is an intermediate coat, and the paint on which the paint is sprayed to a thickness greater than the sag limit is a top coat. What is said to be. (10) In claim 1, the painting step is performed by two spraying steps, a first spraying step and a second spraying step after the first spraying step, and at least After the two spraying steps 1 and 2, the coating thickness is greater than the sag limit. (11) In claim 10, the thickness of the coating film formed in the first spraying step is within a sag limit, and the thickness of the coating film formed in the second spraying step The thickness is considered to be above the sag limit. (12) In claim 10, the thickness of the coating film formed in the first spraying step is within a sag limit, and the thickness of the coating film formed in the second spraying step The thickness is within the sag limit, and the thickness of the coating film formed in the first spraying step and the second spraying step are
The total thickness of the coating film formed in the spraying process is greater than the sag limit. (13) In any one of claims 11 and 12, the spray coating performed in the first spraying step is such that the coating thickness on the edge portion of the object to be coated is greater than that on other portions. This is done so that the coating is thinner than the coating thickness.