Effect of Electrostatic Spraying on the Quality of Steel Barrel Products
Effect of Electrostatic Spraying on the Quality of Steel Barrel Products
Xin Qiaojuan
First, the question is raised
Since the 200-liter steel drum is painted by electrostatic spray paint, when the steel drum is suspended, the corner portion of the top end of the bucket that is gripped by the hanger often has a phenomenon that the paint film is too thin or even exposed. When producing full-open steel drums, in order to facilitate the painting of the barrel hoop, the barrel hoop is placed on the three claws, and the paint is sprayed at the same time as the full-open steel drum, and the bottoming phenomenon is more serious. This is a common problem in the steel drum industry in the process of using electrostatic spraying, and it is also the main factor affecting the appearance quality of steel drums. To this end, we have studied the problem of the upper surface of the electrostatic spray as a subject.
Second, the process requirements and status
The process requirement of the 200-liter steel drum is “the paint film should be bright and full, and no sag, pitting or leaking spray is allowedâ€; “the thickness of the paint film should be uniform, the thinnest should not be lower than 0.02 mmâ€; Not less than the level 2 of the national standard."
According to the process quality requirements of the 200-liter steel drum appearance paint film, the current situation of several large steel drum enterprises in our country has been investigated. It is found from the investigation report that the thickness of the paint film at the top of the spray booth is higher than that of other parts. It is thin and extremely uneven, and sometimes there is a bottom pitting at the corner of the bottom of the barrel. This is not the case at the top of the bucket at the lower part of the spray booth.
Third, the analysis of the reasons affecting the quality of the film
In response to the above problems, we conducted a careful observation and analysis and found that during the process of moving the cup up and down, the movement and the amount of paint are basically the same, but the final effect is quite different. What is the reason? The only difference between the upper and lower parts of the barrel is that there are three-claw hangers on the upper part. It seems that the problem must be on the hanger. To this end, I consulted the technical information about electrostatic spraying and found the root of the problem.
Electrostatic spraying is a negative high-voltage electricity generated by a high-voltage electrostatic generator. It is applied to a high-voltage electrostatic spray cup to release high-voltage static electricity to the coating space where the steel drum is grounded as an anode, forming a high-voltage electrostatic field between the two poles. The "avalanche" phenomenon caused by ionization and corona discharge, and the paint is sprayed into the high-voltage electrostatic field by a high-speed rotating spray cup, and the atomized paint is further atomized and negatively charged. Under the action of the electric field force, the sprayed particles with atomization and negative charge are flying along the direction of the electric field force along the direction of the electric field force of the spray cup, and are uniformly adsorbed on the surface of the steel drum. .
In general, since the paint mist flying to the surface of the steel drum is uniform, it is uniformly adsorbed on the steel drum. Because the round steel drum rotates along the Ω-shaped track, the spray cup is at the same distance from the barrel, and there is no barrier in the middle, so the coating film on the barrel is uniform. In the case of the rotation of the steel drum, the upper and lower bottoms also have uniform spray conditions. However, the upper part of the steel drum is different from the lower part, because there is a hanger on the upper part, which makes a difference.
The steel drum hanger is the same as the steel drum and has the same negatively charged neutralization performance. When the paint mist is applied to the top of the bucket by the gravitational force of the anode and the anode, the paint mist particles are attracted by the hanger when the hanger is first encountered, and the particles near the three claws of the hanger are also changed in direction due to the attraction of the hanger. Thus, the paint film attached to the upper portion of the steel drum is uneven. Moreover, due to the influence of the two sides of the steel barrel on the corners of the flying paint, the paint fog reaching the corner is very small, so there is often a bottom phenomenon at the corner.
The situation of the full-open steel drum is because the barrel hoop placed on the upper part of the three-claw of the hanger has a great effect on the adsorption and direction change of the paint mist, so the coating film on the upper part of the barrel is more affected. The bottoming phenomenon is especially serious than usual.
Fourth, ways and recommendations to solve quality problems
According to the above analysis, the uneven coating film on the upper part of the steel drum is mainly caused by the influence of the painting hanger, which is a problem caused by the structure of the equipment itself. It is not easy to solve this problem. According to analysis and research, there are about the following ways:
1. Change the material of the hanger. Make the hangers have relative antistatic properties. The hanger of the steel drum is actually the wire of the anode of the steel drum. If it is not electrostatically charged, the special exposed anti-static material should be used in the exposed part of the hanger to make the hanger not static. In this way, its attraction to the paint mist will be greatly reduced. However, the function of the hanger as the grounding conductor of the steel drum is to be retained.
2. Use the method of refilling. On the steel drum conveying line after electrostatic spraying, another refilling point is set up, which is manually operated or automatically refilled, thus solving the problem that the paint film on the upper part of the steel drum is thin. Of course, it is better not to use electrostatic spraying.
3. Renovate the hanging structure. The three-jaw hanger can be changed to a single-jaw hanger. For example, the steel bucket is placed upside down, the small opening of the steel drum is opened, and the hanger hook is hooked on the small opening. In this way, the impact of the hanger on the paint mist will be greatly reduced. However, the hook design will have certain characteristics, because the small mouth is on the edge of the top of the bucket, and the vertical state of the steel drum is still maintained after the single hook is hung.
According to the above analysis, in order to solve the problem of uneven film film during the spraying process in a simple and long-term effective manner, it is recommended that the hanging conveyor equipment factory adopt a new structure of the hanging device when producing the equipment. Manufacturers who have already used the equipment can change the design of the new racks themselves, or contact the manufacturer to update the racks to ensure the appearance quality of the 200-liter steel drum.
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