About painting ①

What is painting

Painting is applied to everything related to our lives, such as automobiles, home appliances, furniture, buildings, bridges, ships, etc., and is essential to protect the materials and make them look beautiful.

Painting is not simply an operation of spreading paint, but the finished coating must adhere to the object to be coated and perform its expected function. Even if the paint is good, you can’t get a good finish if there is a problem with the painting process.

For that purpose, it is important to adopt an appropriate coating method in consideration of the shape and workability of the object to be coated, the viscosity and drying characteristics of the paint.

 

Purpose of painting

protection

Metals such as iron and aluminum, concrete, plastic, and wood are rusted by ultraviolet rays and rain winds, become fragile, or are damaged by friction and heat cooling.The paint protects against these by creating a thin film.

Beauty effect

By giving color, luster and patterns, the appearance is made beautiful and the world is colored.
Many things that are commonplace in town, such as buildings, houses, airplanes, trains, cars, etc., are also necessary for our daily necessities such as home appliances and furniture.

Special effects

The paint is given functions such as mold, insect, antiseptic and anti-condensation, and fluorescent and photoconductive functions are added to increase the value of the product.

What is being painted

• Automobile, train, motorcycle, bicycle, airplane, ship
• Refrigerator, washing machine, microwave oven, vacuum cleaner, personal computer
• Buildings, buildings such as bridges, houses, shrines and temples, road signs, signboards
• Furniture, lockers
• Musical instruments

 

Types of painting methods

Spray coating

The spraying method for applying paint in a mist is roughly divided into air, airless, and electrostatic spray methods, and the coating efficiency improves with air <airless <electrostatic spray. The “air spray method” is a device that collides liquid with high-speed air flow. The liquid paint and the pressurized air supplied by the air compressor (air compressor) mix, and the larger the volume ratio of air to the paint, the smaller the fog particles and the better the finished appearance. The “Airless spray method” applies high pressure to the paint itself, so it is possible to spray highly viscous paint. The paint particles ejected like bullets collide with the outside air, atomize, and adhere to the object to be painted. Compared to air spray, fewer particles are scattered and thick film coating is possible, so long-term rust and corrosion protection can be expected.

Brush coating / roller coating

Brush coating is a painting method that has been used for a long time, and paints that dry slowly are suitable for brush painting. When the paint is spread, it can be easily penetrated into the gap and flattened (leveled). The basic method is to apply paint, apply, smooth, and evenly cut off. “Roller coating” is different in brush and tool, but the basics of coating are the same. Since it can be applied more widely than brushes in one operation, you can save the leveling operation.

High speed coating (roll coater / curtain flow coater)

High-speed coating is a coating method that processes liquid films with uniform thickness. The “roll method” is a coating method in which the paint is rolled up and processed into a uniform liquid film, and the paint is applied with a roll. The “curtain flow method” is a coating method in which paint is applied when an object to be coated placed on a conveyor moving at a constant speed passes through the curtain liquid film. As a feature, it has high work efficiency and is suitable for continuous painting of lithographic plates such as plywood and slate board. Disadvantages are that it cannot be applied thinly or on curved objects.

Immersion coating

The soaking method is roughly divided into the “dipping method” in which the object to be coated is dipped in a paint tank, pulled up and dried, and “squeeze coating” in which the paint is pushed in and the excess paint is scrubbed with a rubber plate or sealant. Will be. Ironing is an ancient technique of painting thinly over and over, and is suitable for evenly applying stick-like objects such as pencils and electric wires. However, there is a drawback that the number of coatings increases because the coating amount is small and the film thickness is insufficient.

Electrodeposition coating

A painting method based on electrochemistry. To allow electricity to flow, place an electrolyte and water-based paint in water and connect the platinum electrode and the conductive object to be coated to a DC power supply. Electrochemical reaction takes place near the object to be coated, where the paint particles become electrodes, and the paint deposits and adheres step by step and is applied over the entire surface.

When the current is turned off, washed with water to remove excess paint, dried and baked, the porous coating becomes a continuous phase and exhibits anti-corrosive power.

Electrodeposition coating can be transferred to every corner of the object to be coated, and it is easy to manage the film thickness and coating, and it is environmentally friendly because it uses almost no solvent. Excellent transparency, chemical resistance, and weather resistance. Because the coating film is smooth and uniform, it is excellent in quality and productivity, so it is used in products that are mass-produced. However, because the equipment and cost are high, there are disadvantages such as high cost for small lots and inability to freely change colors.

Electrostatic coating

It is an electrostatic spray method, and it is used as a continuous coating method in factories with a method of improving coating efficiency. This is a method in which an electrostatically charged electric field is applied to the object to be charged and the paint charged to the terminal is electrically adsorbed to the object.

Corona pin method, bell type method (disk / cylindrical cup rotation method), and construction methods differ depending on the atomization method. There is also a powder electrostatic system using powder paint. “”Corona pin method”” is applied with spray particles atomized by air or airless spray. The “bell type method” does not use air to atomize the paint, it rotates at high speed in the cup, and the paint is thinly stretched and released from the edges to atomize the paint.

This method has been put into practical use in car painting lines. In the “electrostatic powder method”, powder particles flow when mixed with air, and the paint particles are charged while colliding and rubbing against the cylindrical wall surface inside the coating machine. After adhering, melt and fix at high temperature.

Electrostatic coating can be applied to the target substance efficiently, and can also be applied to the encircled area. However, since high voltage is used, it is necessary to be careful about electric shocks and fires.

 

What is a jig?

What fixes, energizes, and supports parts is called a jig or rack.

It is easy to process and the finished dimensions are unified, improving work efficiency and often used in mass production.

How to hang jigs and places greatly affects product quality.