In actual fact, affecting the accuracy of overprinting is often tension discomfort. If you can carefully adjust the tension, under normal circumstances, overprinting can be solved.
Ink pH and viscosity adjustment
The effective control of the ink's pH and viscosity during the printing process is the main operation step to ensure the quality of the print.
Water-based ink PH value of about 8.5, at this value, the ink is relatively stable, but in actual production with the temperature rise and the volatilization of ammonia in the ink, PH value will change, affect the printability of the ink. A small amount of stabilizing agent can be added to control the PH value. In normal printing, it is usually required to add 5 ml of stabilizer every half hour, and stir it evenly. Basically oil black can ensure more stable printability. Add stabilizers, otherwise it will be counterproductive and various printing defects will follow.
The viscosity of the ink is the main factor that determines the ink transfer performance, printing firmness, penetration and gloss. Ink viscosity is too high, the darker the color, the ink loss, the degree of drying is slow, the viscosity is too low, the color changes, and the dot expansion causes product quality to decline.
Water-based inks have different viscosities when printed at full-scale and full-print. The general level ink viscosity should be slightly lower. When printing, the speed of the machine also has an effect on the viscosity of the ink. When the printing speed is high, the viscosity of the water-based ink is lower, and the ink viscosity is higher when the printing speed is low.
Die cutting station
In order to discuss the flexo printing technology more comprehensively, besides the above-mentioned operation of the corrugated carton flexo printing process, the problem of a die cutting station for a narrow-width flexographic printing press is also wanted here. The narrow-width flexographic printing presses are generally prepared with three die-cutting stations. After the printing, the wires are indented and die-cut to obtain the desired printed products. The products can be used for the processing of finished products such as stickers, forms, and drug packages. Circular pressure indentation roller, external knife roller die cutting, such as the use of magnetic tools must be prepared with a variety of product specifications of the magnetic roller, composed of serialized specifications, can meet the majority of different specifications size of the product die cutting Processing requirements.
Another type of die-cutting roll is a single-cut roll. It is a knife roller set into a die-cutting blade. It can open one, two, four or more sipes as required. It is mainly used for cutting single-finished products. The cut-off single-roller can be used with the size of the plate roller. Or double use.
The knife roller must be used before the use of the knife roller to ensure the cutting accuracy and avoid the damage of the knife edge. The pressure is adjusted to just cut off the printing material to be the best pressure.
In addition, we must pay attention to post-printing, glazing, lamination, bronzing, and punching.
This article briefly describes some theoretical and practical operations of flexo printing. Hopefully it can become a reference for flexographic printing. The ever-changing packaging and flexo printing operations do not have a fixed model for reference. It is hoped that printing workers will practice more in production and accumulate experience.