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1. Transfer the ink screen to the substrate.
2. Scrape excess ink on the screen.
3. Keep the screen in contact with the substrate.
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 hardened squeegee can scratch off excess ink very well, 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 factor on the above function, so as to avoid adverse effects on the printing effect. When choosing the right 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 hardness meter. 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 is measured by a Shore A hardness meter. 55A-65A is a low-hardness squeegee, 66A-75A is medium hard, more than 75A is high hardness.
A high hardness squeegee is very advantageous for the first three functions of the squeegee. Pressing the ink into the screen and transferring the ink from the fine to the substrate will keep the stencil in line 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, the effective width: refers to the scraper into the aluminum scraper handle, sticking out from the aluminum scraper handle width. This plan adjustment is very important and determines the curvature of the squeegee under pressure. Bend is the cubic value of the effective width. If twice the effective width is greater than 23 is equal to 8 degrees of curvature. The squeegee bend causes two changes: the angle between the squeegee and the screen changes: the printing pressure on the kinder 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 will increase, and the resulting ink layer will remain unsatisfactory. The solution is to increase the hardness of the squeegee and increase the angle of the squeegee.) This is the squeegee Effective width affects the four functions of the squeegee.
The effective width of the squeegee is usually between 20mm and 30mm. 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 a high resolution image on a flat/smooth substrate, the effective width is small (less than 20mm), high hardness, and fast printing with a suitable ink. In uneven and rough printing, 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 curved. 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.
Squeegee shape:
The squeegee shape refers to the cross section of the squeegee. Most squeegee shapes are simple square squeegees, and other shapes of squeegee are used for specific printing conditions. For example: hard squeegee performance is better than soft squeegee, but the ability to adapt to the substrate is poor. With diagonal scraping, the printing edge is easily deformed (like a soft-squeegee).
There are three types of squeegee options for printing workers: square scraping (or right-angle scraping), various sloping and round scraping (horn scraping). The wide application of the square scraper can provide the maximum printing pressure, and the printing angle is determined according to the effective width. Diagonal scraping provides maximum flexibility, printing pressure is reduced, and the printing angle is smaller than the set angle. The round scraper is the least adaptable and provides the least printing pressure. The printing angle can be freely set (often the smallest angle). The above reasons will affect the amount of ink.
blade
The knife edge is an important part of completing the four functions of the squeegee. The sharpness of the squeegee is a factor in the initial control of the amount of ink. The sharp blade provides the smallest amount of ink and the finest image. A blunt and round knife edge increases the amount of ink underneath, and at the same time affects the color and line fineness.
When printing a large area and a simple pattern with transparent oil, the fine variations in color and lines are insignificant. When printing fine lines and four-color dots, with translucent (UV) and transparent ink, you will soon find out the deformation of the knife edge, and compare the first and last prints to determine when the squeegee should be Polished.
Since the selection of the type of squeegee is an important part of the print quality control, the maintenance of the squeegee is also an important link to ensure the normal use of the squeegee. The best way to ensure the quality of the squeegee is to have a clear process that clearly defines the maintenance of the squeegee before and after printing, and how to grind the squeegee.
1. When storing the squeegee, place it flat and do not roll into a circle. Rolling into a circle may cause permanent bending.
2. The aluminum handle should be placed facing down. Do not place the knife edge down.
3. Clean the squeegee immediately after the printing is finished. It is very easy to wash off the ink at this time. Otherwise, the dry ink will damage the knife edge.
4. Do not soak the squeegee in the solvent. Although the squeegee is resistant to solvents, the squeegee can become brittle due to the absorption of the solvent.
5. The squeegee that has just been washed is still soft, the solvent is not completely evaporated, and it cannot be immediately ground. After 12 hours to 24 hours of rest, it can be used again. This will not only polish the effect but also increase the printing efficiency.
6. According to the specific printing quality requirements, it is necessary to sharpen the squeegee. When cleaning and grinding, it is necessary to reduce the loss of the squeegee as much as possible.
The function of scratching in screen printing and how to use it
The squeegee seems to be relatively simple. In fact, the squeegee is a very complicated part of the screen printing. In other methods of printing, the tools for ink transfer are squeegee, ink squeegee, and plastic head. Each tool has its unique function. . In the screen printing, the function of the squeegee mainly has the following four functions: