JP2671503B2 - Painting method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for coating an object to be continuously conveyed by a conveyor with a coating machine equipped with a reciprocator.

[Conventional technology]

Conventionally, when painting an automobile body or the like, since the articles to be coated continuously conveyed by a conveyor have a certain width, a plurality of coating machines are used and the reciprocating movements (reciprocating movements) are performed by a reciprocator. It is common to paint while doing. In the case of the above-mentioned coating, if the reciprocating movement is widely performed with only one coating machine, the conveyor traveling speed must be slowed down, resulting in a significant reduction in coating efficiency. Therefore, when painting a surface of a hood surface or roof surface of an automobile that has a large area to be coated, arrange two to four coating machines at right angles to the traveling direction of the conveyor, and apply them appropriately. I am painting while doing a reciprocating exercise. In addition, in this type of coating, a bell-type electrostatic coating machine suitable for forming a wide and uniform coating film is widely used.

By the way, the reciprocator attached to the above-mentioned coating machine has a drawback in that, due to its mechanism, the traveling speed becomes slow at the turning end portion, that is, the end portion of the reciprocating stroke. Therefore, if the discharge amount condition of the paint is always constant, the coating amount per unit area is inevitably large at the folded end of the reciprocating stroke. Therefore, when coating with multiple coating machines as described above, the folding end of each reciprocating stroke will come on the coating surface, so it will not be possible to coat the coating film thickness evenly over the entire surface. Become. In the case of solid and clear type paints where the film thickness is not a serious problem in terms of appearance quality, there is no problem, but with metallic paints, uneven coating appears clearly. Therefore, in the past, when metallic paint with a large film thickness dependence was used, the number of revolutions of the atomizing head (bell) of the bell-type electrostatic coating machine was significantly increased to widen the spray spray range of the paint. I was trying to fix the above problems.

Separately from this, the paint discharge amount is automatically controlled according to the change of the coated area, and the bell rotation speed and / or the shaving air pressure is changed according to the change of the paint discharge amount to obtain a desired value. Japanese Patent Laid-Open No. 234970/1986 proposes a coating method in which the coating pattern is controlled so as to obtain the coating pattern.

[Problems to be solved by the invention]

The conventional method of increasing the number of bell revolutions to widen the discharge pattern is to finely adjust the discharge amount for each bell. (The amount does not change), but since it is not the adjustment of the discharge amount at the folded end of the reciprocating stroke, there is a limit to the elimination of the unevenness of the film thickness. Moreover, in that case, there is a problem that the metal pieces in the paint are crushed by the high rotation of the bell.

On the other hand, in the method proposed in JP-A-61-234970, as a practical problem, it is very difficult to adjust how to set the discharge amount and the condition of the shaving air pressure at the turning end of the reciprocating stroke. It takes a lot of time and effort to control the spray pattern, and the work is often required due to changes in the coating conditions, so it cannot be easily adopted.

The present invention has been made for the purpose of solving the above problems, and the problem to be solved is to provide a plurality of level type electrostatics in which the folded end of the reciprocating stroke must be set on the painted surface. It is an object of the present invention to provide a coating method capable of performing coating with a uniform film thickness by a simple means in reciprocating coating with a coating machine.

[Means for solving the problem]

The coating method of the present invention capable of solving the above problems is a method of coating an object to be continuously conveyed on a conveyor with a plurality of coating machines that perform reciprocating motion in a direction perpendicular to the conveyor traveling direction. It is characterized in that the paint discharge cut-off is performed at the folded end of the upper reciprocating stroke.

The cut-off range is preferably selected so that the thickness of the coating film is as uniform as possible over the entire coated surface. This selection can be easily made by calculation from the discharge time per unit area or by a preliminary test. The coating machine that performs the discharge cutoff of the coating material may be both or only one of the neighboring coating machines.

The type of coating machine is preferably a bell-type electrostatic coating machine, but is not limited to this. The discharge conditions of the paint during coating should be constantly constant, but the discharge conditions for each coating machine, such as discharge speed (discharge amount / time), bell rotation speed,
The air pressure etc. may be different.

It is optional to operate all coating machines with one reciprocator or each coating machine with its own reciprocator, and the reciprocal stroke and cutoff range may be different for each coating machine for convenience. .

It should be noted that when the coating machine comes off the coating surface due to the shape of the article to be coated, it is preferable to perform the discharge cutoff of the coating material even in the area outside the coating surface because the coating material is not wasted.

[Action]

When the paint discharge cutoff is performed at the folded end of the reciprocating stroke on the painted surface,
The film thickness decreases near the folded end of the reciprocating stroke on the painted surface. In the vicinity of the folded end of the reciprocating stroke, the amount of coating material discharged per unit area is increased due to the slower moving speed of the coating machine, and the film thickness is increased. Is blocked.

〔Example〕

The following discloses one embodiment of the coating method of the present invention, and the gist of the present invention is not limited thereby.

Embodiment 1 As shown in FIG. 3, a hood surface 3 and a roof surface 4 of an automobile body 2 continuously advancing by a conveyor 1 are attached to two coating machines 5, 5 of a bell-type spray electrostatic coating device. Paint with.
Both of these coating machines 5 and 5 are attached to a support arm 7 that reciprocates to the left and right of the electric reciprocator 6. The arrow () in the figure indicates a reciprocating stroke. The reciprocator 6 is attached to a hydraulic lifting cylinder 8 and can move up and down in accordance with changes in height of the hood surface 3 and the roof surface 4. The operation of the cylinder 8 is automatically performed by a limit switch (not shown) provided along the conveyor track.

The coating here is a top coating using a general metallic paint. Distance between both coating machines 5,5: 500 mm, reciprocating stroke: 500 mm, reciprocating cycle: 30 times / min, conveyor speed: 4.5 m / min Paint under the conditions, but perform a paint discharge cutoff for 0.5 seconds near the folded end of the reciprocating stroke. There are various cut-off control methods. In this case, a limit switch is installed on a rotating body that is synchronized with the motor in the reciprocator 6 and is synchronized with the reciprocating motion.

Fig. 1 shows the roof surface 4 when painted as above.
The loci of the two coating machines 5, 5 moving above are shown. In the figure, A and C indicate the center of the reciprocating stroke of the coating machines 5 and 5, B indicates the folded end of the reciprocating stroke on the painted surface, and D and D indicate the folded end of the reciprocating stroke that is not on the painted surface. . The black dots are plots of the positions of the coating machines 5 and 5 at fixed time intervals. The solid line represents the paint discharge, and the dotted line represents the discharge cutoff.

From the figure, it can be seen that the moving speed of the coating machines 5, 5 is slow at the folded end of the reciprocating stroke, and that the paint discharge cutoff is performed at the slower speed. FIG. 2 shows the film thickness distribution of the coating film thus formed in the reciprocating stroke direction. D, A, B, C, D in the figure are the first
Corresponds to that in the figure. It can be seen from FIG. 2 that there is no problem in the film thickness distribution.

Although the present embodiment is a horizontal surface coating method, it goes without saying that the coating method of the present invention is not limited to horizontal surfaces and can be applied to vertical surfaces.

Comparative Example Coating is carried out by the conventional coating method, that is, by the same method as in Example 1 except that the coating material is constantly discharged without being cut off. The locus of the coating machine at that time is shown in FIG. 5, and the film thickness distribution is shown in FIG. The symbols in these figures have the same meanings as described above.

In this coating method, as is clear from FIG. 4, the film thickness becomes large at the folded end portion 8 of the reciprocating stroke, and the film thickness distribution becomes non-uniform.

Example 2 As shown in FIG. 4, coating is performed in the same manner as in Example 1 except that three coating machines are used, and only the central coating machine performs the discharge cutoff of the coating material at the folded end of the reciprocating stroke. . Even in this case, the film thickness can be made uniform.

〔The invention's effect〕

As described above, according to the coating method of the present invention,
The discharge amount of paint per unit area was inevitably increased.The paint discharge cut-off was performed at the folded end of the reciprocating stroke, so the film thickness was made uniform over the entire coating surface, and the coating quality on the exterior was significantly improved. Improve to. In particular, it is possible to eliminate appearance defects such as coating unevenness that are likely to appear with metallic paint.

In addition, since the film thickness is uniform, no extra paint is needed to form a coating film having a thickness satisfying a certain standard, and the paint can be saved.

Moreover, since the method of the present invention is not a method of coating while controlling the discharge amount, it does not require a troublesome control pattern search and can be carried out by a simple means using conventional coating equipment.

[Brief description of the drawings]

FIG. 1 is a diagram showing a locus of a coating machine moving on a coating surface and a discharge cutoff of paint according to an embodiment of the method of the present invention, and FIG. 2 is a film of a coating film formed by the embodiment. Fig. 3 is a diagram showing a thickness distribution, Fig. 3 is a front view schematically showing a coating facility, Fig. 4 is a diagram relating to another embodiment, and Fig. 5 is a trajectory of a coating machine in a comparative example (conventional method). FIG. 6 and FIG. 6 are views showing the film thickness distribution of the coating film formed by the comparative example. In the figure: 1 ... Conveyor, 3 ... Hood surface (painted surface) 4 ... Roof surface (painted surface), 5 ... Painter 6 ... Reciprocator B ... Fold end of reciprocating stroke on paint surface S: Reciprocating stroke

Claims (1)

(57) [Claims] 1. A method of coating an object to be continuously conveyed on a conveyor with a plurality of coating machines that perform reciprocating motion in a direction perpendicular to the traveling direction of the conveyor. A coating method characterized in that the discharge cutoff of paint is performed at the folded end.