Paper printing shrinkage common sense

General Knowledge of Thin Paper Printing Shrinkage Problems In order to increase production efficiency, flexographic printing presses nowadays are focused on increasing the drying capacity. Generally used natural wind, hot air and infrared and other drying methods. Some combined mechanical devices have two sets of UV curing systems. In this way, a phenomenon will be found in proofing or production, that is, a set of plates made of the same set of films will have deviations in the lateral dimension, and the error hour is less than 1 mm; when the error is large, there are 2 mm to 3 mm. In actual production, if there is no problem with the film or plate, the deviation in the lateral dimension is caused by the two opposing processes of printing and drying.

About 50% of the components in water-based inks are water. So, for thin paper, if a large area of ​​water-based ink is printed, the surface of the paper will become swollen and widen. The larger the printing area, the lower the number of anilox roller lines. The more pronounced the phenomenon of widening. When drying is performed after printing, the paper is narrowed due to shrinkage, and the larger the amount of heating, the more water is volatilized, and the narrower the width of the paper becomes. Most of the flexo printers' heating and drying systems (including UV curing systems) have a minimum speed startup operating point, such as 20 meters/minute. For safety reasons, below this speed, the IR and UV drying devices are not open; reaching or exceeding this value will open. If the starting speed is slightly higher than this speed value, the heating amount of the paper is large and the shrinkage is obvious.

The farther away from the unit, the greater the horizontal overprint error. Therefore, in the printing production process, the speed of the printing press should be increased as much as possible, and unnecessary hot air and infrared drying should be minimized so as to avoid the lateral overprint error. In addition, overprinting errors can also occur when the speed of the machine is appropriately increased during a single printing process. Tension, mechanical speed, and temperature have a constant value, often 1:1.2 (1.3):1.

Source: Ke Yin Network