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1. Transfer the ink through the screen to the substrate.
2. Scrape excess ink on the screen.
3. Keep the screen in contact with the substrate line.
4. Can print different shapes of substrates.
Only the above four features of the squeegee are well used to print high quality prints. The physical properties of the scraper play a decisive role in the above functions. (For example, a high-hardness squeegee can very well scrape off excess ink, but it does not meet the requirements of various shapes of the substrate well.) Therefore, when selecting the squeegee, it is necessary to fully consider the influence of the squeegee performance factors on the above functions, so as to avoid adverse effects on the printing effect. When choosing a suitable performance squeegee, consider the following four factors:
1. Hardness: The squeegee is usually made of polyurethane and the hardness of the squeegee is measured with a durometer. The hardness, size, and shape of the squeegee determine the bendability, flexibility, and pressure of the squeegee. Hardness ranges from 55 degrees to 90 degrees (Shore A). The hardness value was measured with a Shore A hardness meter. 55A-65A is a low hardness squeegee, 66A-75A is a medium hard, more than 75A is a high hardness.
The high hardness squeegee is very advantageous for the first three functions of the squeegee. The ink is pressed into the screen and the ink is transferred from the fine stencil to the substrate, and the stencil is in line contact with the substrate. The only defect of high hardness squeegee is that it can not satisfy the printing of substrates with different shapes. When printing rough surfaces and uneven surfaces, the quality of squeegee is also very high.
2. Effective Width: refers to the width of the squeegee extending from the aluminum squeegee into the aluminum scraper handle. This width is important and determines the curvature of the squeegee under pressure. Bend is the cubic value of the effective width. If twice the effective width results in a curvature greater than 23=8.
The squeegee bend causes two changes: the angle between the squeegee and the screen changes, and the printing pressure transmitted to the substrate decreases. For example, the squeegee is likened to a set of springs. When the spring is forced at an angle, the spring begins to bend, and the transmitted force is getting smaller and smaller. Squeegee printing angle is reduced, printing pressure is insufficient, and the printing effect is not ideal. The printing angle is small, the printing pressure is reduced, the amount of ink is large, and the ink layer is thickened. (In this case, the printing operator will increase the printing pressure, the curvature of the squeegee increases, and the resulting ink layer is still not ideal. The solution is to increase the hardness of the squeegee and increase the angle of the squeegee.) This is the effectiveness of the squeegee. The effect of width on the four functions of the squeegee.
The effective width of the squeegee is usually between 20 MM and 30 MM. The choice of the best effective width is based on the flatness of the substrate, the screen image resolution, and other printing parameters such as squeegee angle, speed, and ink type. When printing high resolution images on flat/smooth substrates, the effective width is small (less than 20mm), high hardness, and fast printing with suitable ink. On rough, rough substrates, the effective width should be increased (sometimes more than 30mm), the hardness should be reduced, and the low hardness squeegee should have poor adaptability and should not be excessively bent. You can also use the middle hard and soft three-layer scraping or double layer. scratch. In general, the effective width increases, the printing speed decreases, and the printing angle is increased.
How to use the squeegee in silk screen printing
Squeegee seems simple, but scratching is a very complex part of screen printing. In other methods of printing, tools for ink transfer include squeegees, ink rams, pressure rams, and plastic heads, each of which has its own unique function. In screen printing, the functions of the squeegee mainly include the following four aspects: