JPS6380876A - Method for adjusting thickness of coating film in curtain flow painting - Google Patents

Abstract

PURPOSE:To easily control the thickness of a film, by detecting the thickness of a wet paint film by the non-contact type film thickness detector opposed to a blade and adjusting a roll gap, a plate passing speed and the peripheral speed of each roll on the basis of the detected value. CONSTITUTION:A painting rubber roll 11 expands by the thinner in paint with the advance of painting work and the gap (g) between the rubber roll 11 and a doctor roll 21 becomes small and the thickness (tw) of a wet paint film changes. Since the relation between the roll gap and the thickness of the paint film can be preset, the roll gap (g) is automatically corrected to a predetermined value by displacing the doctor roll 21 corresponding to the thickness (tw) of the wet paint film detected by a film thickness sensor 37. When at least one of a coil-shaped plate passing speed Vs, the peripheral speed Vc of the painting rubber roll 11 and the peripheral speed Vd of the doctor roll is adjusted along with the roll gap (g), the thickness of the paint film is adjusted with higher accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This IJI relates to a method for adjusting the coating film thickness in curtain flow coating, particularly a method for adjusting the coating film thickness iA in roller one-type curtain flow coating. This emitting device 1 is applied to coating steel plates and other cut plates or coiled plates.

(Prior Art) A slit method and an overflow method are already known as curtain flow coating techniques. For example, the slit method is disclosed in Japanese Patent Laid-Open No. 58-142870, in which paint is supplied to a head (container) and discharged from the slit gap to form a curtain shape. In this method, a predetermined coating film thickness is obtained by adjusting the coating viscosity and the slit gap.

The overflow method changes the surface tension, viscosity, and other properties of the paint while diluting it with a solvent. The paint thus adjusted to a suitable coating viscosity is allowed to overflow from the container into a curtain shape. In this method, a predetermined coating film thickness is obtained by adjusting the coating viscosity and the like. However, it is difficult to freely change these conditions, and the actual situation is that the coating film thickness is generally adjusted by changing the threading speed. Therefore, curtain coating is usually used only for coating cut plates, where the threading speed can be freely changed.

Furthermore, a curtain coater using one roller type has been developed in recent years. This invention is directed to a one-roller type.
A schematic diagram of the curtain coater is shown in FIG.

As shown in the drawing, a paint P whose viscosity has been adjusted in advance is supplied to a roll gap between a painted rubber roll 11 and a metal doctor roll 21, discharged, and scraped off with a blade 35 brought into contact with the painted rubber roll 11. The scraped paint P flows down along the blade 35 to form a paint curtain C, and is applied to the object l (in this example, a cut steel plate) passing through the blade 351. The doctor roll 21 can move forward and backward relative to the painted rubber roll 11, and by displacing the doctor roll 21, the gap between the two rolls can be widened. A predetermined coating film thickness is obtained by adjusting the sheet passing speed through the roll gap 1 and the circumferential speeds of the coating rubber roll 11 and the doctor roll 21. The doctor knife 31 limits the paint P adhering to the doctor roll 21.

The above roll gap is manually adjusted by a gear-driven regulator (not shown) mounted on the doctor roll bearing:
A is adjusted. During adjustment, the doctor roll 21 is brought into contact with the painted rubber roll 11 once to determine the zero point, and then the doctor roll 21 is separated from the painted rubber roll 11 to set a predetermined roll gap. Further, the peripheral speed of the painted rubber roll 11 and the doctor roll 21 is detected by a speed meter, and the speed of the conveyor 9 is detected by a tachometer to detect the passing speed of the steel plate l, thereby making it possible to determine the passing speed. can be adjusted individually. That is, the coating film thickness is adjusted by setting various conditions such as the sheet passing speed, the roll gap, the peripheral speed of the pIi rubber-covered roll 11 and the doctor roll 21, and so on.
The conditions were adjusted individually or in combination of two or more while operating appropriately depending on the situation of the coating film thickness.

Then, the test coating was repeated many times until a predetermined film was obtained, and the coating thickness was adjusted.

(Problem that Problem 1!1 is intended to solve) In the conventional coating film thickness adjustment method, test coating is performed several times, which wastes a large amount of IJ1' material and a lot of time.

In addition, since painted rubber rolls are made of polyurethane, natural rubber, synthetic natural rubber, neoprene butyl rubber, silicone rubber, or fluorine rubber, they swell due to the thinner in the paint, and the gap between the painted rubber roll and doctor roll increases over time. It was changing with. Therefore, there is a drawback that the coating film thickness, which is initially set, fluctuates over time.

In the case of cut plate painting, the painted steel plate manufacturing line (pretreatment - painting - baking) is connected by a separate conveyor.
Each process can be run independently for intermittent operation. Therefore, even if the coating operation was stopped, only a few defective products were produced, without significantly impairing productivity, and even if the coating film thickness was adjusted each time, there was no significant inconvenience. However, in a coil coating line, the above processes are continuously connected by steel plate coils, so if the coating operation stops, it will directly affect the surrounding area, resulting in several hundred meters of defective products. As a result, a large amount of work loss time occurs in the pre-processing and baking processes before and after the coil coating line, and production is hindered.

(Means for Solving the Problems) The present inventors have discovered that the film thickness of the paint flowing down along the blade surface (
(hereinafter referred to as wet 1 coating thickness) tw, circumferential speed of the coating rubber roll. , peripheral speed of doctor roll 1, threading speed ma,
The relationship between the roll gap and the roll gap g was investigated. As a result, as shown in Fig. 2, there is a direct proportional relationship between the roll gap g and the wet paint film thickness t, and the roll peripheral speed ma
It has been found that the wet paint film thickness tw and, in turn, the coating film thickness t can be controlled by adjusting the plate passing speed ma$ and the roll gap g. Also,
The wet a material film thickness tw was measured using a metal blade 1. It was also found that measuring with

Therefore, the method for adjusting the coating film thickness tA of the first invention is to detect the wet coating thickness tw using the non-contact JJ1 film thickness detector facing the blade in the coating method using the roller one-way curtain flow. Based on the detected value of tw, p! Adjust the roll gap g between the rubber-covered roll and the doctor roll.

The film thickness detector is preferably a capacitance type that can be measured with a non-contact type that is commercially available or a magnetic type 1 magnet 1, which is generally available on the market.The measurement distance is such that the accuracy of the wet paint film thickness Lm is about 1 μm. Therefore, it is recommended that the surface roughness be within 5 degrees.In order to improve the accuracy of desorption detection, the blade surface should have a smooth polished finish (for example, 1 surface roughness R@aX is 6.3Z).
(below) or plating is preferable.

The roll gap g is adjusted by displacing the doctor roll. Displacement of the doctor roll is performed by moving a bearing stand that supports the doctor roll back and forth using a drive device including a motor and a screw mechanism. The motor is driven by the detected film. Automatically controlled based on thickness.

Further, in the second invention, in addition to adjusting the L roll gap g, at least one of the sheet passing speed ma 5, the coated rubber roll circumferential speed ma C, and the doctor roll circumferential speed ma d is adjusted to a1.
g Adjust.

The sheet passing speed fS is adjusted by the drive motor of the tension reel or the conveyor, the circumferential speed MCC of the coated rubber roll, and the circumferential speed MAD of the doctor roll are adjusted the power supply circuits of the drive motors of these rolls.

(Function) As the painting process progresses, the paint rubber roll expands due to the thinner in the paint. As a result, the roll gap g between the coated rubber roll and the doctor roll becomes smaller. Since the rA relationship between the roll gap g and the wet I material thickness tw can be known in advance through experiments, the detected wet I material film thickness 1. By displacing the doctor roll accordingly, the roll gap g is automatically corrected to a predetermined gap. As a result, the coiled plate material is coated with a constant film over its entire length.

In addition, the film thickness can be further increased by adjusting the roll gap g to 31 and adjusting at least one of the sheet passing speed M, the circumferential speed M of the coated rubber roll, and the circumferential speed M of the doctor roll. Adjusted by accuracy. This results in
Rubber roll machine that coats the coating film thickness t that corresponds to the sheet threading speed without having to pass the sheet at the beginning of painting.

The peripheral speed of the doctor roll, the peripheral speed of the doctor roll, and the roll? ! I
It can be obtained by adjusting the t gap g.

Note that the wet paint film thickness is detected at the position of a smooth and fixed metal blade. Therefore, compared to the conventional case where the film thickness is detected on the hill of the object to be painted, it is possible to detect changes in the thickness of the object to be painted, changes in the measurement distance from the film thickness sensor due to vibrations during traveling, and the surface roughness of the surface of the object. No measurement errors occur due to influences.

(Example) FIG. 1 schematically shows an apparatus for carrying out the invention.

A steel plate coil 1 is unwound from a payoff reel 2 and wound up by a tension reel 3 which is rotationally driven by a DC motor 4. By adjusting the rotational speed of the DC motor 4 in the power supply circuit 5, the sheet passing speed is adjusted. The rotation speed of the DC motor 4 is determined by a digital counting type rotation speed sensor 7.
Detected by

A painted rubber roll 11 having a smooth surface with a straightness of 1/100 mm or less is arranged on the E side of the steel plate coil 1. The gutter-equipped rubber roll L] is rotationally driven by a DC motor 12, and by adjusting the rotation speed of the DC motor 12 in a power supply circuit 13, the roll peripheral speed C is adjusted.The rotation speed of the DC motor 12 is a digital counting type rotation. Speed sensor 1
Detected by 5.

A doctor roll 21 is arranged with a required roll gap g between the coated rubber roll 11. The doctor roll 21 is a metal roll having a smooth surface with a straightness of 5/1000 or less. The doctor roll 21 is a driving wave 2i2
It is rotatably supported by a bearing stand 22 which is moved forward and backward by a shaft 3. The drive wave 223 includes a screw shaft 24 rotated by a stepping motor, and the screw shaft 24 is rotated by a nut of the bearing stand 22.
(not shown). The displacement of the bearing stand 22 is detected by a magnetic scale type sensor 26. Further, the doctor roll 21 is rotationally driven by a DC motor 27, and the rotational speed of the DC motor 27 is set to j in the power supply circuit 2 days.
A! As a result, the roll peripheral speed d is adjusted to tA. The rotation speed of the DC motor 27 is detected by a digital counting type rotation speed sensor 29.

A blade 35 for scraping off the paint P is arranged at the lowest end of the painted rubber roll 11, and is fixed in a vertical position. The blade 35 extends along the width direction of the roll, and its knife-shaped L end is in contact with the roll surface.

A non-contact electrostatic old dipping type film thickness sensor 37 is arranged opposite the blade 35. Film thickness sensor 37
is the wet paint film thickness t of the paint flowing down on the blade 35
Detect w.

In the coating film configured as shown in L, when the paint P is supplied to the gap between the coating rubber roll 11 that is rotating (in the direction of the arrow) and the doctor roll 21 that is rotating in the opposite direction, the roll It is continuously discharged from the gap.

The discharged paint P is scraped off by the blade 35 and flows down along the blade surface to form a paint curtain C. The paint that fell onto the steel plate coil IL: becomes a coating film F.

Next, a method for adjusting the coating film thickness will be described.

FIG. 2 is a diagram showing the relationship between the wet paint film thickness tw and the roll gap g using the circumferential speed ma of the coating rubber roll and the circumferential speed ma of the doctor roll as parameters. This FIG. 2 shows that the wet paint film thickness tw and the roll gap g are in a directly proportional relationship. Also, Figure 3 shows the sheet threading speed using the wet paint film thickness tw as a parameter! FIG. 3 is a diagram showing the relationship between S and dry coating film thickness t. These relationships have been determined in advance through experiments and are input into the control computer 41.

First, before starting the coating work, the roll gap g, the threading speed M, the circumferential speed M of the coating rubber roll, and the circumference of the doctor roll are determined based on the coating conditions and the relationships shown in Figures 2 and 3 below. Set speed magnification d. By utilizing the relationships shown in FIGS. 2 and 3, a predetermined coating film thickness can be obtained without actually passing the plate at the start of the coating operation.

When the coating work is started, the film thickness sensor 37 detects the wet paint film thickness t11, and the plate passing speed master s,
Peripheral speed ma of painted rubber roll, peripheral speed ma of doctor roll
is detected by the respective rotational speed sensors 15 and 29. Each detection result is then input to the control computer 41.

The control computer 41 detects the detected wet paint film thickness tw.
From the relationship shown in FIG. 2, the deviation between the set value and the measured value of the roll gap g is calculated. The calculation result is output to the stepping motor drive circuit 25, and the drive device 23 drives the bearing stand 2.
2 is displaced. Further, the displacement of the bearing stand 22 is detected by the magnetic scale type sensor 26, and the displacement of the bearing stand 22 is detected by the control computer 4I.
, and the displacement of the bearing stand 22 is controlled by feedback control J.
It will be done. Than this.

The roll gap g between the coating rubber roll 11 and the doctor roll 21 is corrected and maintained at a predetermined set value. As a result, fluctuation errors in the discharge H,1 due to expansion of the coating rubber roll 11 are eliminated.

Further, the control computer 41 records the detected plate passing speed and the circumferential speed of the coated rubber roll. , the deviation between the circumferential speed Mad of the doctor roll and each set value is calculated, and the calculation result is output to the power supply circuit 5° 13.28 of each DC motor 4, 12.27. As a result, the output voltage from the power supply circuit is controlled, and the sheet passing speed V and the roll circumferential speeds C and Md are maintained at set values. Further, the sheet passing speed ma, and the roll circumferential speeds maC and mad are feedback binned based on the detected values of the rotational speed sensor 7.15.29.

(Effect of RJl) As described above, in the present invention, changes in the roll gap between the coated rubber roll and the doctor roll due to expansion of the coated rubber roll can be automatically corrected. This makes it possible to obtain a product with a constant coating film thickness over the entire length of the coil. In addition, since the roll gap is quickly and accurately corrected, it has a significant effect in continuous sheet curtain coating. Furthermore, the conventional test coating for obtaining a predetermined film thickness can be omitted, and the predetermined film thickness can be reliably obtained without passing the plate.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of the coating film thickness and adjustment device of the present invention, and Fig. 2 shows the roll r I gap g and the wet paint film J on the grade! FIG. 3 is a diagram showing the relationship between sheet passing speed M$ and dry coating film thickness t, and FIG. 4 is a schematic diagram of a coating apparatus using one-roller curtain flow. l: Steel plate coil or cut plate, 2: Payoff reel, 3
: Tension reel, 4: Motor, 5: Power supply circuit, 7:
Speed sensor, 11: Painted rubber roll, 12: Motor, 1
3: 'ili source circuit, 15: Speed If sensor, 21: Doctor roll, 22: Bearing stand, 23: Drive device, 24: Screw shaft, 25: Drive circuit, 26: Magnetic scale displacement sensor, 27: Motor, 28: power supply circuit, 29: speed sensor, 31: doctor knife, 35 knife blade, 37: film thickness sensor, 41: fTJJ control computer.

Claims (4)

[Claims] (1) In a method of painting a board by discharging paint from a gap between a coating rubber roll and a doctor roll, scraping off the paint on the paint roll with a metal blade, and letting it flow down in a curtain-like manner, the blade faces the blade. The film thickness of the paint flowing down along the blade surface is detected by a non-contact film thickness detector, and the roll gap between the coated rubber roll and the doctor roll is adjusted based on the detected value of the film thickness. How to adjust paint film thickness in curtain flow painting. (2) The coating film thickness adjusting method according to claim 1, wherein the plate material is a continuous coiled plate material. (3) In a method of painting a board by discharging paint from a gap between a coating rubber roll and a doctor roll, scraping off the paint on the paint roll with a metal blade, and letting it flow down like a curtain, the blade faces the blade. A non-contact type film thickness detector detects the film thickness of the paint flowing down along the blade surface, and based on the detected value of the film thickness, the roll gap between the painted rubber roll and the doctor roll is adjusted. A method for adjusting a coating film thickness in curtain flow coating, the method comprising adjusting at least one of a circumferential speed, a doctor roll circumferential speed, and a sheet passing speed. (4) The coating film thickness adjusting method according to claim 3, wherein the plate material is a continuous coiled plate material.