JPH0435763A - Electrostatic coating method - Google Patents

Abstract

PURPOSE:To obtain a uniform thickness distribution of a coating film and fine finished appearance by fixing a body to be coated on the front side of a capturing plate kept at the same electric potential as the body to be coated and coating the body. CONSTITUTION:A body 1 to be coated is fixed on the front side of a capturing plate 5, this plate 5 is put on a conveying truck 2 conveyed by a conveyor and the body 1 is coated with a spray gun 4 moved up and down by a reciprocator 3. Paint is sprayed so as to uniformly coat the entire surface of the body 1 and paint is oversprayed on the obliquely lined part. Since this oversprayed paint is captured by the plate 5, the concentration of the paint on the periphery of the body and the suspension of the paint in the air are prevented. Coating ensuring a uniform thickness of a film and fine finished appearance can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an electrostatic coating method for obtaining a uniform coating thickness distribution and a good finished appearance.

(Prior art) In industrial painting of automobile bodies, etc., the object to be coated is placed on a transport device such as a transport trolley, and the object is being transported while a spray gun or the like attached to a reciprocator that moves perpendicularly to the object is used for painting. A coating method in which a flat surface is coated using a device is often used, but in this method, it is necessary that the spray range of the paint matches the dimensions of the object to be coated as much as possible, both in the transport direction and in the direction perpendicular thereto. Hereinafter, the dimension of the object to be coated along the transport direction will be referred to as length, and the dimension perpendicular to it will be referred to as width.

(Problem to be Solved by the Invention) Normally, the stroke of the reciprocator is constant, so if a narrow object to be coated or an object with a varying width flows onto the painting line, the paint will Sometimes it is sprayed beyond the width of the object, this is called overspray. In industrial painting, it is necessary to minimize overspray to prevent wasteful consumption of paint, but expensive control equipment is required to discharge and stop paint depending on the width of the object to be coated. . Moreover, even in that case, overspray of at least about 1/2 of the spray pattern occurs. The same applies to the length direction of the object to be coated.

In addition to the economic problem of wasted paint consumption, oversprayed paint also causes the following problems: In other words, oversprayed paint may be adsorbed to the outer edge of the object being coated, causing a so-called picture frame phenomenon in which the film thickness distribution becomes thicker only at the outer edge of the object being coated, or floating in the air and then adhering to other painted surfaces. This causes a problem of deteriorating the finished appearance of the surface. This phenomenon is particularly remarkable in the case of electrostatic coating. Furthermore,
When painting a vertical surface, paint that is oversprayed from above is concentrated above the object to be coated due to the downward flow of air in the coating booth, causing large unevenness in film thickness distribution in the vertical direction of the object to be coated. There was a problem.

(Means for Solving the Problems) The present invention provides a collection plate such as a flat plate or a curved plate having an equipotential with the object to be coated around the object to collect the oversprayed paint. Concentration of paint on the outer edge or top of the painted object,
Alternatively, the above problem is solved by preventing floating in the air.

That is, the electrostatic coating method of the present invention is an electrostatic coating method in which various objects of different sizes are loaded onto a conveyance device, and the objects are coated by a coating device attached to a reciprocator that moves in a direction perpendicular to the conveyance direction. In the painting method, a collection plate that is kept at the same potential as the object to be coated is placed around the object to be coated, the object to be coated is fixed, and at the same time the object to be coated is oversprayed over its length and/or width. It is characterized by the ability to collect paint.

The collection plate used in the present invention is preferably a flat plate or a curved plate having a width around the object to be coated in the longitudinal direction or perpendicular direction of the object to be coated, which is at least 172 mm or more than the spray pattern of the coating device.

(Example) Hereinafter, the present invention will be described by way of examples with reference to the drawings.

The right front fender of an automobile was electrostatically coated as shown in FIG. 1 as an object to be coated in flames.

As shown in the figure, the object to be coated 1 is fixed to the front surface of the collection plate 5,
This was loaded onto a carrier 2 that was transported by a conveyor in the direction of the arrow, and was painted by a spray gun 4 that was moved vertically by a reciprocator 3.

In FIG. 1, the paint is sprayed in the area surrounded by dotted lines so that the entire surface of the object to be coated is coated uniformly, and the shaded areas are oversprayed. Since this oversprayed paint is collected by the collection plate 5, the paint is prevented from concentrating on the outer edge and floating in the air. In the case of electrostatic painting as in this example, the oversprayed paint is attracted to areas close to the object to be coated, which tends to cause uneven film thickness, but the collection plate is kept at the same potential as the object to be coated. This can be prevented by doing so.

A collection plate maintained at an equal potential was fixed above the outer door panel of a car with a length of about 1000 mm and a width of about 800 m + a, and this was attached to a transport cart, and a rotary bell attached to a reciprocator with a stroke of 1500 mm. It was electrostatically painted using a mold coater. For comparison, the door outer panel alone was attached to a transport vehicle using electrostatic painting without using a collection plate.

The coating thickness of each of the obtained coating films was measured at the measurement points shown in FIG. 2a, and the film thickness distribution is shown in FIG.

The circle mark in Figure 2 shows the film thickness distribution without the collection plate, but this device has a large reciprocating stroke compared to the width of the door plate, and has an overspray area of about 700 mm at the top, so electrostatic As a result, the oversprayed paint is concentrated at the top due to the airflow inside the booth, resulting in a significantly thicker and uneven film thickness. On the other hand, the mark Δ indicates the film thickness distribution when the collection plate is attached above the door outer panel, and is almost uniform over the entire surface.

(Effects of the Invention) As described above, according to the present invention, when an object to be coated placed on a conveyance device is coated with a coating device attached to a reciprocator, oversprayed paint is spread around the object to be coated. It is collected by a collection plate that is kept at the same potential as the object to be coated, and is prevented from adhering to the object to be coated, resulting in a uniform film thickness.
The effect of being able to perform coating with a good finished appearance can be obtained.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the electrostatic coating method of Example 1, Figure 2a is a perspective view of the object to be coated showing the coating thickness measurement points of Example 2, and Figure 2 is an example. 2 is a film thickness distribution graph of the coated object. 1...Object to be painted (or front fender)2...
Transport vehicle 3...Reciprocator 4...Spray gun Fig. 2

Claims (1)

[Claims] 1. Load various objects to be coated of different sizes onto a conveying device,
In the electrostatic coating method, in which the object to be coated is coated using a coating device attached to a reciprocator that moves in a direction perpendicular to the conveyance direction, a collection plate that is kept at the same potential as the object to be coated is placed around the object to be coated. An electrostatic coating method characterized by fixing the object to be coated and collecting paint oversprayed over the length and/or width of the object at the same time as painting the object.