JPH02284042A - Controlling method for pulverization of electrostatic coater - Google Patents

Abstract

PURPOSE:To easily and periodically control uniform pulverization of an electrostatic coater by performing spray in the same environment as an actual line and performing both measurement of particle diameter and reference setting by a laser irradiator and a photodetector which are oppositely provided and similarly measuring the particle diameter at a time of the actual coating line and comparing the measured value with the preset reference value. CONSTITUTION:A detector 35 for diameter of sprayed particles is placed on a truck 7. The coating gun 17 of a coating robot 9 is faced between a laser irradiator 36 of gaseous He - Ne and a photodetector 37 provided to the detector 35 in the same environment as an actual line. The distribution of particle diameter in a spraying pattern is measured while performing spray and the reference of the range of uniform pulverization is preset. The same method is performed at a time of actual coating and the measured value is processed in a controlling part. When this result exists in a range within the previously preset reference value, it is decided that coating unevenness does not exist and actual coating is performed. When this result exists in the outside of the range within the preset reference value, the actual line is stopped and work for solving nonconformity is performed. Thereby control of uniform pulverization is performed before principal coating and generation of coating failure is prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling atomization of an electrostatic coating machine, and particularly to a method for controlling uniform atomization of paint sprayed by a paint gun of an electrostatic coating machine. Related to atomization control method for electric coating machine.

[Conventional technology]

Electrostatic painting is a coating method used on actual automobile painting lines. The principle of electrostatic painting is that atomized and charged paint is attracted to the surface to be painted using electrostatic attraction.

When carrying out such electrostatic painting, it is well known that the uniform atomization of the paint sprayed by the paint gun has a major impact on the smoothness and gloss of the finished paint film and the paint transfer efficiency. It is being

By the way, the following items can be considered as factors for uniformly atomizing the spray paint (making the particle size uniform in any part of the pattern of the spray paint).

In other words, in the case of an airless paint gun or an air spray type paint gun, factors such as atomizing air pressure, pattern air pressure, paint discharge amount, static voltage, and paint viscosity are considered as factors for atomization. It will be done. In the case of a bell-shaped paint gun, factors such as the bell rotation speed, shaving air pressure, paint discharge amount, electrostatic voltage, and paint viscosity are considered to be factors for atomization.

However, even if the above items are properly controlled, paint may adhere to the nozzle tip or bell when spraying paint from the nozzle tip or bell at the tip of the paint gun, and this may cause the paint to adhere to the nozzle tip or bell. Uniform atomization is inhibited. Particularly when painting bumpers of automobiles in different colors depending on the user's preference, uniform atomization is often inhibited by the adhesion of residual paint.

Therefore, conventionally, when starting painting or changing colors, when cleaning the area from the manifold to the nozzle tip or bell using a mixture of thinner and air, mixing air is jetted out from the nozzle tip or bell to remove the nozzle tip. The paint remaining on the bell was removed.

[Problem to be solved by the invention] However, in the past, the paint adhering to the nozzle tip or bell at the tip of the paint gun was removed by mixing air, and a method was used to check whether the paint spray particles were uniformly atomized. There was no. As a result, problems such as uneven coating occur, and it is only after the problem occurs that it becomes clear that the nozzle tips and bells have not been cleaned sufficiently (the paint is not evenly atomized). there were.

Also, among the factors mentioned above for uniform atomization of paint, controlling paint viscosity is extremely difficult, and even when changing colors, the viscosity changes slightly due to slight temperature changes in the morning and afternoon. There is a problem in that it tends to prevent uniformity of the diameter.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for controlling atomization of an electrostatic coating machine that can regularly control uniform atomization of sprayed paint using a simple device. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the method for controlling atomization of an electrostatic coating machine according to the present invention is to apply paint in the same environment as when painting a workpiece in an actual painting line. The size of the sprayed particles is measured using a spray particle size detection device that has a laser irradiator and a photodetector placed facing each other, and based on this measurement value, the size of the spray particles that can be coated well is determined. a step of setting a range standard for uniform atomization, and measuring the distribution of paint spray particles using the spray particle size detection device before painting a workpiece on the actual line, and using this measurement value as the uniform atomization range standard. and determining whether the spray particle size is acceptable or not based on the range criteria.

[Effect]

Before painting the workpiece W with the electrostatic coating machine (painting robot 9, see Fig. 2) on the actual line, the spray particle size detection device 35
The distribution of the paint spray particles is measured using a 3D system, and this measured value is compared with a preset range standard for uniform atomization to control whether the spray particle size is uniformly atomized.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment of the atomization control method for an electrostatic coating machine according to the present invention will be described based on the drawings.

First, the structure of an apparatus for carrying out the atomization control method for an electrostatic coating machine according to the present invention will be explained.

FIG. 1 is a partial front view of an apparatus for carrying out the atomization control method for an electrostatic coating machine of the present invention, and FIG. 2 is a side view of the entire apparatus.

In FIGS. 1 and 2, l is a drainboard, 2 is a punched metal, 3 is a static pressure chamber, 4 is a bit, and 5 is a paint booth. The painting booth 5 is designed to collect unpainted paint mist, and its structure is made up of two tiers of drainboards 1 (lower tier 1a, upper tier lb) on the floor surface. A punched metal 2 is arranged above the drainboard 1.

There is a static pressure chamber 3 further above the punched metal 2, and air flows down from the static pressure chamber 3 to collect uncoated paint mist into a pit 4 below the drainboard 1. In addition, in this painting booth 5, the lower slat 1a
A conveyor conveyor 6 is disposed below. moreover,
A truck 7 and a rail 8 for transporting the truck 7 are disposed above the lower drainboard la.

On the other hand, a painting robot 9 (see FIG. 2) is arranged above the upper drainboard 1b. At the tip of the second arm 10 of this painting robot 9, there are so-called three hand axes 11.12.1.
3 are arranged. Also, the three hand axes 11.12.
Thirteen drive sources 14, 15, 16 are arranged alternately as shown in FIG. A coating gun 17 is rotatably supported at the tip of a shaft 13 of the three hand shafts. In addition, in the figure, 28 is a nozzle tip at the tip of the coating gun.

The first arm 18 is located on a base 19 and is pivotally supported on a rotary table 20 that is rotatably supported by a drive source.

Further, the first arm 18 of the painting robot 9 is connected to the second arm 1.
Connected to 0. The swinging of the first arm 1 and the second arm 10 is performed by the first cylinder 21 and the second cylinder 22. In addition, 27 is a manifold, 42
43 is a thinner supply port, and 43 is an air supply port.

Further, a perch john 23 is erected on the lower slat la between the rail 8 and the upper slat 1b.

Reference numeral 29 on the trolley 7 is a board, and a servo motor 30 is disposed on the bottom surface of the board 29. Also, the board 2
There is a protruding bar screw 31 on the top surface of the bar 9, which is screwed into a screw hole 33 provided in a lifting table 32 above the bar screw 31.

Further, guide rods 34 are inserted from the four corners of the board 29 to the four corners of the lifting table 32 to prevent the lifting table 32 from wobbling.

A spray particle size detection device 35 is disposed on the top surface of the lifting platform 32, and a He-Ne gas laser irradiator 36 (see FIG. 1) and a photodetector 37 are installed on the spray particle size detection device 35, which are separated from each other. are placed facing each other.

Note that, as explained with reference to FIG. 5, the laser beam irradiated by the He--Ne gas laser irradiator 36 is expanded to a diameter of 6 mm, for example, by the beam expander 38. The atomized particles 50 through which this expanded laser beam crosses the optical path
The diffracted light C from the atomized particles 50 passes through the lens 39, and then the particle size is determined by the photodetector 40 arranged in a concentric ring at a distance of the focal length of the lens 39. be measured.

This measurement principle is based on the Fraunhofer diffraction phenomenon (Fraunhofer's diffraction phenomenon).
unhofer's diffraction phe
According to the Fraunhofer diffraction phenomenon, the diffracted light C that is conically deflected by the spray droplets 50 is focused around the optical axis 41 after passing through the lens 39. Furthermore, the deviation from the optical axis 41 is determined by the size of the particle.

That is, the large particles 50a are focused near the center, and the small particles 50b are focused far from the center. Also, if the particles are the same, their positions do not matter (they focus on the same place).

FIG. 3 is a partial front view of the apparatus showing a state in which a workpiece is coated, and FIG. 4 is a side view of the entire apparatus shown in FIG. 3.

In the figure, 24 on the trolley 7 is a board, 25 is a base shaft, 2
Reference numeral 6 denotes a support for supporting the workpiece W, and the support 26
is erected on the substrate 24 and the base shaft 25. The workpiece W is placed on a cart 7 transported by a transport conveyor 6 in a direction facing the painting robot 9. The coating robot 9 sprays paint from the coating gun 17 onto the workpiece W thus placed.

Next, the operation of the atomization control method for an electrostatic coating machine according to the present invention will be explained in detail.

In the same environment as when painting the work W on the actual painting line, the painting gun 17 of the painting robot 9 is connected to the HeNe gas laser irradiator 36 and photodetector 37 of the spray particle size detection device 35 installed on the trolley 7. (See Figure 5)
. Then, the paint is sprayed in this state, and the spray particle size detection device 35 is used to measure the particle size distribution at the center of the spray pattern a due to the Fraunhofer diffraction phenomenon.

In addition, when measuring the particle size distribution, the servo motor 3
0, the coating is repeatedly sprayed, and the particle size distribution at every position of the radially sprayed spray pattern a is measured.

The particle size distribution of the light intensity detected by the photodetector 40 of the spray particle size detection device 35 in this manner is the spray particle size detection data shown in FIG.

Also, among the spray particle size detection data in Fig. 6, for example, N0
The data of No. 09 was processed by computer, and the particle size-incidence rate distribution was plotted on the horizontal axis and the incidence rate was plotted on the vertical axis, resulting in a graph showing the particle size - It is an incidence distribution map.

By the way, as a result of repeated experiments with the coating gun 17 of this embodiment, the conditions for uniform atomization of the spray droplets that provide a good painted surface without uneven coating are as follows: Referring to FIG. 7, the average diameter of the spray droplets is 14 It was found that there is a correlation between coating unevenness and the standard value for uniform atomization of spray particles, which is the case where the particle size falls within the range of 3μ to 24.6μ and the maximum diameter does not exceed 112.8μ. .

Therefore, in this embodiment, it is assumed that the range reference value for uniform atomization of the spray particles is recorded in advance in the memory of the control unit (not shown).

Next, the actual line painting booth 5 as shown in Fig.
In the following, we will explain the operation when starting painting for the first time using the painting gun 17 or when starting painting after changing the paint color. In addition, when starting painting after changing the paint color,
As shown by the two-dot chain line in FIG. 2, the tip of the painting robot 9 is sandwiched between the drainboard 1 and the verchion 23, and the space between the manifold 27 and the nozzle tip 28 is mixed with air and thinner. shall be washed.

First, place the spray particle size detection device 35 on the top! 3! The placed cart 7 is transported into the painting booth 5, and the painting gun 17 of the painting robot 9 is connected to the He-Ne gas laser irradiator 36 and the photodetector 3.
It is positioned and stopped at a position where it faces directly between 7 and 7.

Then, in this positioned state, paint is repeatedly sprayed by the paint gun 17. At this time, while operating the servo motor 30, the particle size distribution of the radially sprayed spray pattern a is measured using the spray particle size detection device 35 over the particle diameters at all positions of the spray pattern a.

This measured value is processed in the control unit, and if the processed result of the measured value is within the range standard value for uniform atomization of spray droplets recorded in the memory, there is no coating unevenness (spray droplets are uniform). It is determined that the material is atomized into fine particles. on the other hand,
If it is outside the standard value range, it is determined that uneven coating has occurred (spray particles are not uniformly atomized), and the actual coating line is stopped.

In addition, the scope of uniform atomization of spray particles! If it is within the $ value range, move on to the next painting job. That is, as shown in FIGS. 3 and 4, the cart 7 on which the workpiece W is placed directly facing the coating gun 17 is conveyed into the coating mousse 5, positioned and stopped at a predetermined position, and the workpiece W is Paint is sprayed onto the paint from the paint gun 17 of the painting robot 9.

On the other hand, if it is outside the standard value range, for example, an alarm is displayed, the actual painting line is stopped, and then the painting gun 1 is
Confirm the state of paint adhesion around the periphery of step 7. and,
After solving the problem, move on to the next painting job.

〔Effect of the invention〕

As described above, according to the present invention, paint is sprayed in the same environment as when painting workpieces on an actual line, and the particle size range standard of the spray particles is set based on the correlation between the particle size distribution of the spray particles and coating unevenness,
The structure is designed to measure the distribution of spray particle size of paint from an electrostatic atomizer during actual painting, and to judge the quality of the spray particle size by comparing this measured value with the above-mentioned particle size range standard. The atomization of the sprayed N2 material can be controlled periodically by the device.

Further, according to the present invention, uniform atomization of the paint, which causes uneven coating, can be controlled before the main coating on the workpiece, so it is possible to prevent coating defects and improve the quality of the painted surface.

[Brief explanation of drawings]

FIG. 1 is a partial front view of a device that implements the atomization control method for an electrostatic coating machine of the present invention, and FIG. 2 is a side view of the entire device.
Fig. 3 is a partial front view of the same apparatus showing the situation when painting a workpiece, Fig. 4 is a side view of the entire apparatus shown in Fig. 3,
FIG. 5 is a schematic explanatory diagram of the atomization detection device of the present invention, and FIG.
The figure shows measurement data showing the particle size distribution of atomized particles, and FIG. 7 is a particle size-incidence distribution diagram of atomized particles. ...Painting booth, ...Dolly, 7.Painting gun, 6.He-N e 7.Photodetector, 6.Transfer conveyor, 9.Painting robot, 35. ...Atomized particle size detection device, gas laser irradiator, 40...Photodetector. Figure 1 Figure 3 Figure 4

Claims (1)

[Scope of Claim] In an electrostatic coating machine atomization control method for controlling whether spray particles of paint sprayed by a paint gun of an electrostatic coating machine are uniformly atomized, The paint is sprayed in the same environment as when painting the surface, and the distribution of the sprayed particle size is measured using a spray particle size detection device with a laser irradiator and a photodetector placed facing each other. Based on this measured value, we set a range standard for uniform atomization of the spray particles that allows for good coating, and before painting the workpiece on the actual line, we use the spray particle size detection device to determine the spray particle size of the paint. A method for controlling atomization of an electrostatic coating machine, comprising measuring the distribution and comparing the measured value with the uniform atomization range standard to determine whether or not the spray particle size is acceptable.