JP6939156B2 - Coating film inspection equipment - Google Patents

Description

The present invention relates to a coating film inspection device for inspecting the presence or absence of a coating film on a coated metal plate.

In the production of a metal plate, a paint corresponding to the function required for the metal plate is applied to the surface. The paint is applied to the required film thickness for the function to be exhibited, and then dried to form a coating film.
There are various coating methods in the coating process, but for the strip-shaped metal plate, a contact type roll coater method, a non-contact type curtain coater method, or the like is used. In either method, the coating film is continuously formed on the surface of the strip-shaped metal plate.

In the production of strip-shaped metal plates, especially strip-shaped steel plates, the leading coil and the trailing coil are welded on the entrance side of the factory to perform continuous manufacturing. When painting such a strip-shaped steel sheet, there is a case where the painting is temporarily suspended at the time of welding the leading coil and the trailing coil, and the painting is restarted after the welding is completed. At this time, if the painting is stopped and restarted manually due to welding, there is a possibility that an unpainted part may be generated in a part of the transport direction (longitudinal direction) of the strip-shaped steel sheet due to the delay in the operation of restarting the painting or the forgetting to operate. ..
Therefore, the unpainted portion is confirmed before the coated steel sheet is shipped, and the unpainted portion can be confirmed by the film thickness measuring device provided on the exit side of the coating line. As an example of the film thickness measuring device, those described in Patent Documents 1 to 3 are known, and when the film thickness of the coating film of the coated steel plate is measured by the film thickness measuring device, the film thickness of the unpainted portion becomes zero. , Unpainted parts can be confirmed.

Japanese Unexamined Patent Publication No. 8-21719 Jikkenhei 3-63811 Japanese Unexamined Patent Publication No. 58-115306

However, the strip metal plate immediately after being carried out from the coating apparatus is in a wet state in which the paint coated on the surface thereof is not dried. In such a state, since the coating film is not stable, it is difficult to stably detect the film thickness by the film thickness measuring device. For this reason, in the conventional film thickness measuring device, the film thickness must be measured after a certain period of time until the paint dries and the coating film stabilizes, and the film thickness measuring device is inevitably placed on the side of the coating line. It will be placed away from the painting equipment. Further, in some cases, a drying device is provided on the downstream side of the coating device in order to dry the paint. In this case as well, since the drying device is provided between the coating device and the film thickness measuring device, the film thickness measuring device is provided accordingly. It will be placed away from the painting equipment.
When the film thickness measuring device is placed away from the coating device in this way, when the unpainted part is detected by the film thickness measuring device (when the part with zero film thickness is detected), the film thickness is measured from the coating device. Since there is a possibility that at least a part of the strip-shaped metal plate corresponding to the distance to the device has an unpainted portion, the steel plate corresponding to this distance is cut down, which causes a decrease in yield.
In order to reduce the amount of devaluation of the metal plate and prevent the yield from decreasing, the film thickness measuring device may be brought closer to the coating device, but as described above, the film thickness is measured to dry the paint and stabilize the coating film. It is difficult to bring the film thickness measuring device close to the coating device because the film thickness measuring device must be waited for a certain period of time.

The amount of devaluation of the steel sheet can be reduced by inspecting the presence or absence of the paint film on the painted metal plate immediately after being carried out from the painting device. Since it is in a wet state that is not dry, a non-contact inspection is required to detect the coating film in such a state.
Therefore, the present inventor thinks that the presence or absence of a coating film can be detected from the reflected light reflected by projecting a laser beam onto the surface of a coated metal plate, more specifically, the surface of a coated steel sheet, as follows. Experiment was conducted.

That is, first, laser light was projected onto a painted steel sheet coated with paint (painted steel sheet in a wet state) and an unpainted steel sheet, and the reflected light was captured by a sensor, and the amount of received light was investigated. As the sensor, a general-purpose type digital laser sensor (head: LN-NH42 type, amplifier: LV-N11N type) manufactured by KEYENCE Corporation was used. As the steel sheet, 60k steel and 45k steel were prepared, and a coating film was formed with different paints and film thicknesses. The amount of light received was investigated by changing the relative angle between the steel plate and the sensor from 0 ° to 7 ° in 1 ° increments. The relative angle refers to an angle formed by a line segment orthogonal to the surface of the steel plate and a line segment connecting the sensor and the intersection of the surface of the steel plate with the line segment.

Table 1 shows the amount of reflected light received (count number) at each relative angle.
From Table 1, it was found that the amount of light received by the coated steel sheet was larger than the amount of light received by the unpainted steel sheet at any relative angle.

Further, FIG. 5 shows the difference in the amount of light received between the painted steel sheet and the unpainted steel sheet with respect to the relative angle. From FIG. 5, the difference in the amount of light received is large when the relative angle is 4 ° or less, and the presence or absence of the coating film can be easily determined by installing the sensor so that the relative angle is 4 ° or less with respect to the steel sheet and setting an appropriate threshold value.

The present invention has been made in view of the above circumstances, and a coating film inspection capable of easily inspecting the presence or absence of a coating film on a coated metal plate before drying the coating film, thereby reducing the amount of devaluation of an unpainted steel sheet. The purpose is to provide the device.

In order to achieve the above object, the coating film inspection device of the present invention is a coating film inspection device for inspecting the presence or absence of a coating film on a coated metal plate.
A coating device for applying paint to the surface of the metal plate and a drying device for drying the paint coated on the surface of the metal plate by the coating device are provided, and laser light is applied to the surface of the coated metal plate. It is characterized by being provided with a coating film sensor that inspects the presence or absence of the coating film from the reflected light that is projected and reflected.

In the present invention, a coating film inspection device provided between the coating device and the drying device is provided with a coating film sensor that inspects the presence or absence of the coating film from the reflected light reflected by projecting a laser beam onto the surface of the coated metal plate. Is provided, so that the presence or absence of a coating film can be easily inspected before the paint dries. Therefore, the coating film inspection device can be brought closer to the coating device than the conventional film thickness measuring device. Therefore, even if there is an unpainted part on the painted metal plate, this unpainted part corresponds to the distance from the painting device to the coating film inspection device at the maximum, so that the unpainted metal plate is compared with the conventional one. It is possible to reduce the amount of devaluation, and thus it is possible to prevent a decrease in the yield of the painted metal plate.

By the way, if the coated metal plate warps in the width direction (C warp occurs at the inspection position), the reflected light of the laser beam may not be sufficiently received by the coating film sensor. That is, when a laser beam is projected onto the surface of a coated metal plate that is curved due to warping, at least a part of the reflected light is removed from the coating film sensor, and the reflected light cannot be sufficiently received by the coating film sensor. May

Therefore, in the configuration of the present invention, a plurality of the coating film sensors are provided.
A plurality of the coating film sensors may be arranged in a fan shape in the plate width direction of the coated metal plate.

According to such a configuration, since a plurality of coating sensors are arranged in a fan shape in the width direction of the coated metal plate, even if the coated metal plate is warped in the width direction, the reflected light of the laser beam is transmitted to the coating sensor. It is possible to reliably inspect the presence or absence of the coating film by receiving sufficient light.

According to the present invention, the presence or absence of the coating film on the painted metal plate can be easily inspected before the paint is dried, so that the amount of devaluation of the unpainted metal plate can be reduced.

It is a figure which shows typically the schematic structure of the coating line front part part of the coating metal plate provided with the coating film inspection apparatus which concerns on this embodiment. It is a figure which shows typically the schematic structure of the latter part of the coating line of the coating metal plate provided with the coating film inspection apparatus which concerns on this embodiment. It is a figure which shows typically the schematic structure of the coating film inspection apparatus which concerns on this embodiment. It is a graph which shows the change of the light receiving amount by the coating film sensor of the coating film inspection apparatus which concerns on this embodiment. It is a graph which shows the change of the average light receiving amount by the coating film sensor of the coating film inspection apparatus which concerns on this embodiment. It is a graph which shows the light-receiving amount difference of the coated steel sheet and the unpainted steel sheet with respect to the relative angle of the coating film sensor.

Hereinafter, embodiments of the coating film inspection apparatus according to the present invention, more specifically, embodiments of the coating film inspection apparatus for steel sheets will be described with reference to the drawings.
FIG. 1A is a diagram schematically showing a schematic configuration of a front stage portion of a coated steel sheet coating line provided with a coating film inspection device according to the present embodiment. Further, FIG. 1B is a diagram schematically showing a schematic configuration of a rear stage portion of a coated steel sheet coating line provided with the coating film inspection device according to the present embodiment.

As shown in FIG. 1A, in the front stage portion of the line, the strip-shaped steel plate K before the paint is applied is set in a state of being wound around the payoff reel 1. The strip-shaped steel plate K is unwound from the payoff reel 1, cut linearly in the plate width direction by the inlet shear 3, and then painted in sequence. A spot welder 4 is arranged after the inlet shear 3, and when the preceding strip-shaped steel plate K is interrupted, the spot welder 4 causes the tail end of the preceding strip-shaped steel plate K and the tip of the trailing strip-shaped steel plate K. Are joined by welding, and manufacturing is performed while maintaining continuity.
Then, after the necessary surface treatment, base coating, etc. are performed, as shown in FIG. 1B, the coated steel plate K1 carried out from the coating apparatus 13 is dried by the drying apparatus 14 and the surface is dried by the oiler 15 at the rear stage portion of the line. After being painted with oil, it is wound up on the tension reel 2.

In the present embodiment, the coating film inspection device 20 is located between the coating device 13 that coats the surface of the strip-shaped steel plate K with paint and the drying device 14 that dries the paint coated on the surface of the strip-shaped steel plate K by the coating device 13. Is provided. The coating film inspection device 20 is attached to, for example, the front wall portion on the inlet side of the drying device 14 via a bracket or the like.
The coating film inspection device 20 includes a plurality of coating film sensors CH1 to CH4 that inspect the presence or absence of a coating film from the reflected light that is reflected by projecting laser light onto the surface of the coated steel sheet K1.
That is, as shown in FIG. 2, in the present embodiment, the coating film inspection device 20 includes four coating film sensors CH1 to CH4, and these coating film sensors CH1 to CH4 are fan-shaped in the width direction of the coated steel sheet K1. Have been placed. Specifically, when the coated steel sheet K1 is along the upward convex in the width direction (that is, when C warpage occurs at the inspection position), it is orthogonal to the surface of the virtual coated steel sheet K2 in which no warpage occurs. Assuming that the intersection of the line segment L and the surface of the coated steel sheet K2 of the line segment L is O, four coating film sensors CH1 to CH4 are arranged in a fan shape around the intersection O.

Assuming that the angle formed by the line segment L and the line segment connecting each coating film sensor CH1 to CH4 and the intersection O is the relative angle of the coating film sensors CH1 to CH4 with respect to the coated steel plate K1, the relative angle of the coating film sensor CH2 is The relative angle of the coating sensor CH3 is 4 ° counterclockwise, the relative angle of the coating sensor CH3 is 4 ° clockwise, the relative angle of the coating sensor CH1 is 8 ° counterclockwise, and the relative angle of the coating sensor CH4 is 8 ° clockwise. Become. Further, the linear distances between the intersection O and the coating film sensors CH1 to CH4 are all equal.
In FIG. 2, in order to clearly show the coating film sensors CH1 to CH4, the above-mentioned relative angle is shown to be about twice as large as the actual one.
Further, when the coated steel plate K1 is along the downward convex in the width direction, the coating film sensors CH1 to CH4 are arranged in a fan shape in the same manner.

The coating film sensors CH1 to CH4 are reflection type laser sensors, respectively, and the light emitting element that emits the laser light and the laser light emitted from the light emitting element are reflected and returned on the surface of the coated steel plate K1 that is the detection object. It is equipped with a light receiving element that receives the reflected light.
Since the coating film sensors CH1 to CH4 are arranged at the relative angles described above, the tangent line at the intersection of the laser beam emitted from each coating film sensor CH1 to CH4 and the surface of the coated steel sheet K1 is the coating film sensor CH1. ~ It is substantially orthogonal to the traveling direction of the laser beam emitted from CH4. Therefore, most of the laser light emitted from the coating film sensors CH1 to CH4 is reflected by the surface of the coated steel sheet K1 and returned, and is received by the coating film sensors CH1 to CH4, respectively.
The relative angles of the coating film sensors CH1 to CH4 are appropriately set according to the degree of warpage of the coated steel sheet K1. When the degree of warpage is large, that is, the larger the curvature of the coated steel sheet K1, the larger the relative angle of the coating film sensors CH1 to CH4 is set, and the smaller the curvature, the smaller the relative angle of the coating film sensors CH1 to CH4 is set. When the coated steel sheet K1 is not warped, the coating film sensor may be arranged on the line segment L described above.
Further, since the coating film sensors CH1 to CH4 of the coating film inspection device 20 may exceed the guaranteed operation temperature in the vicinity of the drying device 14 (see FIG. 1), the drying device 14 and the coating film sensors CH1 to CH4 A shielding plate (not shown) for blocking hot air is installed between them to take measures against temperature.

Then, with respect to the strip-shaped steel plate K1 in which the above-mentioned warp is generated, two layers (lower layer: aiming at 4.5 g / m ²⁾ are managed by a coating device (not shown) and a coating device 13 provided on the downstream side of the coating device. A coating film in the range of 2.0 to 7.0 g / m ² , upper layer: aiming at 3.5 g / m ² , and a control range of 1.5 to 5.5 ^{g / m 2} ) is formed, and the coating device 13 forms the upper layer coating film. After applying the paint for forming the above, the amount of received light was investigated by the coating film sensors CH1 to CH4.
When the amount of light received was actually measured, it was found that the coated steel sheet K1 fluttered (vibrated) up and down and the amount of light received fluctuated, as shown in FIG. Note that FIG. 3 shows fluctuations in the amount of light received by the coating film sensor CH3.
In this case, since it is difficult to discriminate the threshold value between the unpainted portion having a low light receiving amount and the painted portion having a high light receiving amount, the light receiving amount is continuously measured by the coating film sensors CH1 to CH4 at 2-second intervals. The moving average value for 30 seconds (2 seconds × 15 data) was used as the light receiving amount, and the influence of the fluttering of the coated steel sheet K1 was eliminated. The result is shown in FIG. Note that FIG. 4 shows fluctuations in the average amount of light received by the coating film sensor CH3.

As shown in FIG. 4, the light receiving amount (relative value) of the unpainted portion is about 1000 to 1500, while the light receiving amount (relative value) of the painted portion is the coating film sensors CH1 and CH2 and the coating film sensor CH4. 2000-3000, and the coating film sensor CH3 3000-5000. By setting a threshold value as appropriate, it is possible to discriminate between painted and unpainted. In particular, if the judgment is made using the result of the coating film sensor CH3 having the highest sensitivity (among the plurality of coating film sensors CH1 to CH4, the coating film sensor CH3 having the highest light receiving amount is used to discriminate between painted / unpainted (painting). If the presence or absence of the film is determined), it is possible to determine whether the coating is painted or unpainted (determining the presence or absence of the coating film) without malfunction.

As described above, according to the present embodiment, a coating film that inspects the presence or absence of a coating film from the reflected light that is reflected by projecting a laser beam onto the surface of the coated steel plate K1 between the coating device 13 and the drying device 14. Since the coating film inspection device 20 provided with the sensors CH1 to CH4 is provided, the presence or absence of the coating film can be easily inspected before the coating film dries. Therefore, the coating film inspection device 20 can be brought closer to the coating device 13 than the conventional film thickness measuring device. Therefore, even if an unpainted portion is generated on the coated steel sheet K1, the unpainted portion corresponds to a maximum distance from the coating device 13 to the coating film inspection device 20, so that the unpainted portion is unpainted as compared with the conventional case. The amount of devaluation of the steel sheet can be reduced, and thus a decrease in the yield of the coated steel sheet K1 can be prevented.
Further, since a plurality of (4) coating film sensors CH1 to CH4 are arranged in a fan shape in the plate width direction of the coated steel plate K1, even if the coated steel plate K1 is warped in the width direction, the reflected light of the laser beam is emitted. The coating film sensors CH1 to CH4 can sufficiently receive light, and the presence or absence of the coating film can be reliably inspected.

13 Coating device 14 Drying device 20 Coating film inspection device CH1 to CH4 Coating film sensor K Strip-shaped steel plate (metal plate)
K1 painted steel plate (painted metal plate)

Claims (2)

A coating film inspection device that inspects the presence or absence of a coating film on a coated metal plate.
A coating device for applying paint to the surface of a metal plate flowing on a coating line and a drying device for drying the paint coated on the surface of the metal plate by this coating device are provided and laser light is applied to the coating. It is equipped with a coating sensor that inspects the presence or absence of the coating from the reflected light that is projected and reflected on the surface of the metal plate .
The coating film sensor inspects the presence or absence of a coating film based on the amount of reflected light received by the unpainted portion of the coated metal plate and the amount of reflected light reflected by the coated portion of the coated metal plate. A coating film inspection device characterized by this. A plurality of the coating film sensors are provided.
The coating film inspection apparatus according to claim 1, wherein a plurality of the coating film sensors are arranged in a fan shape in the plate width direction of the coated metal plate.

Images