The influence of the squeegee on the color difference of the Cosmetic Boxes is all in these details

The influence of the squeegee on the color difference of the Cosmetic Boxes is all in these details

The position, angle and pressure of the squeegee contacting the printing plate have a great influence on the ink color of the Cosmetic Boxes, especially the ink color of the light screen part. The ideal state is that the squeegee is in the same position from beginning to end, but due to some reasons, the position, angle, and pressure of the squeegee have to be adjusted during the printing process. Therefore, it is necessary to understand the influence of its changes on the color of the Cosmetic Boxes, so that the range of color changes is acceptable.

The influence of the squeegee on the color of the Cosmetic Boxes

1. Printing distance

The contact position of the squeegee and the plate cylinder determines the distance between the contact point of the squeegee plate and the imprinting point. Generally speaking, the longer the distance is, the easier the ink in the cells dries, the lower the transfer rate of the ink, and the printing effect is equivalent to the partial reduction of the ink. On the contrary, when the distance is short, the transfer rate of the ink is relatively high, but at the same time, some small lines on the layout will be reflected on the substrate.

The length of the printing distance should be adjusted according to the printing speed, ink viscosity, cell depth and layout quality. Most squeegees are installed on the upper 1/4 or so of the plate cylinder.

2. The pressure and angle of the squeegee

The contact angle of the scraper refers to the angle between the tangent at the contact point between the scraper and the plate cylinder and the scraper. When the squeegee scrapes the ink, it actually scrapes off part of the ink in the cells. When the squeegee pressure is high or the squeegee angle is steep, the ink in the cell is scraped off more, the transfer amount of the ink is also reduced, and the color density is reduced. The smaller the blade pressure and the flatter the angle, the less ink in the cells is scraped off, the ink transfer amount is relatively larger, and the color density is larger, but the edges and corners of the image and text are prone to blurring.

When the squeegee is assembled, it must be ensured that its cutting edge line is parallel to the busbar of the printing plate, otherwise the pattern color at both ends of the printing plate will be inconsistent due to the difference in the printing distance, angle and pressure at both ends.

(1) Squeegee angle. According to experience, the contact angle of the scraper is generally 55°. The scraper is properly installed and the blade should bend around 5° under load, therefore, the installed contact angle is 60°. However, in the actual production process, it should not stick to the rules, and the angle can be adjusted according to the actual situation to ensure the quality of the Cosmetic Boxes.

(2) Squeegee pressure. The pressure of the scraper on the plate cylinder is set according to the actual needs. Generally, the pressure of the scraper is set at 20~25kg/m, so that the scraper can maintain a certain elasticity when moving on the plate, which is beneficial to the scraper operation. Under the premise of effectively scraping ink and controlling the amount of ink in the printing process, the contact pressure between the squeegee and the surface of the gravure cylinder should be as light as possible to reduce the unnecessary wear of the squeegee on the printing plate.

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