Roller coating is divided into manual roller brushing and mechanical roller coating. They are all methods of rolling a roller dipped in paint on the surface of the object to be coated to apply the paint.
(1) roller brush coating
Also known as manual roller coating, it is a construction method suitable for general protective coating. It relies on a cylindrical roller brush to pick up the paint, and coats the surface of the object to be coated with the help of rolling action. This method has the advantages of simple tools, small investment, convenient operation, high coating efficiency (about 10 times higher than brush coating efficiency), and better coating quality. This method is suitable for coating higher viscosity coatings. , so solvent (thinner) can be saved.
Roller brushing is very suitable for painting large areas of flat surfaces (such as painting ships, bridges, and building exterior walls). Generally, it is often combined with brushing to complete the coating project, but it is not suitable for coating objects with complex shapes and high decorative requirements.
1. Tools used for roller brushing
The tool used for roller brushing is a roller brush. The roller brush is generally cylindrical. In order to adapt to the roller brushing on the outer surface of the pipe, the edge and corners of the workpiece, it can also be made into a special cylindrical shape with irregular and curved lines. The roller brush is composed of a brush roller and a bracket. The brush roller is composed of a roller core and a paint-containing layer. The roller core plays the role of supporting the paint-containing layer. Surface for dipping paint. When performing roller brushing, the appropriate roller brush should be selected according to the characteristics of the paint and the condition of the surface to be coated. After the construction is completed, the roller brush should be cleaned in time, dried and stored properly.
2. Operation skills of roller brush coating
Before the start of roller brushing, dip the roller brush into the pan containing the paint, and roll it to pick up the paint. Roll it several times to make the roller brush absorb the paint evenly. When painting with a roller brush, press the roller brush on the surface of the object to be coated and roll it. In order to prevent the paint from dripping, the pressure should be light at the beginning, and then gradually increase the pressure, so that the paint on the roller brush can evenly adhere to the workpiece. surface. Roller brushing generally runs on the surface of the workpiece according to a W-shaped trajectory so that the paint is roughly distributed on the surface to be coated, then the roller brushes are criss-crossed and parallel to each other to make the thickness of the coating uniform, and finally use the roller brush to press a certain amount. Roll in the order of directions to modify the flattened surface; for places that are not easy to roll with a roller brush, use a brush to repaint.
When painting by roller brushing, the viscosity of the paint and the number of times of roller brushing should be adjusted according to the thickness requirements of the coating film.
(2) Mechanical roller coating
Mechanical roller coating (also known as mechanical roller coating) is a coating construction method using a special roller coating machine.
1. Advantages and disadvantages of mechanical roller coating
(1) Advantages
①Mechanical roller coating is suitable for automatic production lines with high efficiency. Although its construction efficiency is lower than that of spraying, it is 2~3 times higher than that of brushing. And it can meet the construction requirements of thick coatings.
②Because high-viscosity coatings can be used, solvents can be saved during deployment, thereby reducing the emission of volatile organic compounds and improving the construction environment.
③Since the thickness of the coating film is easy to control, the quality is guaranteed.
Therefore, mechanical roller coating has been widely used in the surface coating of various plate materials. (including metal plate, cardboard, leather, plastic plate). Moreover, the coating production line for steel coils is an integral body connected with the rolling production line for steel plates. The degree of continuous automation has been greatly improved.
(2) Disadvantages
① The one-time investment of mechanical roller coating equipment is large and the cost is high.
②During the construction, the section of the plate may sometimes be damaged. Subsequent repair work is required.
③It is not suitable for coating complex and uneven surfaces.
④The surface smoothness of the coating film formed after coating is poor, so it is not suitable for coating the surface with high decorative requirements.
2. Equipment and process of mechanical roller coating
The main equipment used in mechanical roller coating is a roller coater. The structure of the roller coating machine is very similar to the roller printing machine used in the printing industry, and it is composed of rollers with different numbers. According to different functions, they are called idler rollers and paint rollers respectively. The supporting roller mainly plays the role of supporting and transmitting power, and most of them are made of steel, while the paint roller plays the role of painting and is made of rubber. For example, a four-roller paint machine is composed of four rollers: a belt roller, a transfer roller, a paint roller, and an embossing roller. The rotation directions of the adjacent two rollers are opposite. By adjusting the gap between the paint roller and the adjacent roller, , can achieve the purpose of controlling the thickness of the coating film. During construction, the paint is poured into the paint container of the roller coater. When the roller rotates, the paint will stick to the roller and be sent to the paint roller through the belt roller and the transfer roller. When the paint roller rotates at a speed of 20~30r/min, the paint will be applied to the surface of the flat workpiece between the delivery rollers. The roller coater can be used to coat the plate on one side, and can also finish the double-sided coating on the workpiece at the same time.
