Function and Usage of Squeegee in Screen Printing(Part 1)

Squeegee may seem simple, but in fact, squeegee is a very complicated part of screen printing. In other printing methods, the tools for ink transfer include Squeegee, ink wheel, pressure wheel and glue wheel. Each tool has its own unique function.

In screen printing, the function of squeegee mainly has the following four aspects:

1. Transfer the ink to the substrate through the screen;

2. Scrape off the excess ink on the screen;

3. Keep the screen in contact with the substrate line;

4. It can print different shapes of substrates.

Only when the above four functions of the squeegee are brought into play well, can high-quality printed matter be printed.

The physical properties of the scraper play a decisive role in the above functions. (For example: a squeegee with high hardness can scrape off excess ink well, but it cannot meet the requirements of various substrate shapes). Therefore, when choosing a squeegee, it is necessary to fully consider the influence of squeegee performance factors on the above functions to avoid adverse effects on the printing effect. The following four factors need to be considered when choosing a squeegee with suitable performance:

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. The hardness ranges from 55 degrees to 90 degrees (Shore A). The hardness value is measured with a Shore A hardness tester.

55A-65A is low-hardness squeegee, 66A-75A is medium-hardness, and more than 75A is high-hardness.

High-hardness squeegee is very beneficial to the first three functions of squeegee. It presses the ink into the screen and transfers the ink from the fine screen to the substrate, and maintains the line contact between the screen and the substrate.

The only defect of high-hardness squeegee is that it can not meet the printing of different shapes of substrates, and the quality of squeegee is also very high when printing on rough and uneven surfaces.

2. Effective width: refers to the width of the squeegee that the squeegee is installed in the aluminum squeegee handle and extends from the aluminum squeegee handle. This width is very important and determines the curvature of the squeegee under pressure. The curvature is the cube of the effective width. If twice the effective width obtains a curvature greater than 23, the squeegee bending will cause two changes: the angle between the squeegee and the screen changes: the printing pressure transferred to the substrate is reduced.

For example, compare the squeegee to a set of springs. When the spring is stressed at a fixed angle, the spring begins to bend, and the transmitted force becomes smaller and smaller. The squeegee printing angle is reduced, the printing pressure is insufficient, and the printing effect is not ideal. The printing angle is small, the printing pressure is reduced, the ink volume is large, and the ink layer is thickened. (In this case, the printing operator will increase the printing pressure, the curvature of the squeegee will increase, and the resulting ink layer is still not ideal. The solution is to increase the hardness of the squeegee and the angle of the squeegee.)

This is the effect of the effective width of the squeegee on the four major functions of the squeegee.

The above information is provided by squeegee supplier.