Printing pressure
The flexo pressure is generally 1-3 kg/cm2, and the corrugated box printing pressure is generally 1-2 kg/cm2. Because of the pressure of the printing plate and the reaction force of the impression cylinder, the phenomenon of light color and color cast tends to appear during the printing operation. When the amount of ink is “not enough”, the printing pressure of the printing plate tends to increase in an attempt. To achieve the ink requirements, the result is a serious edge effect, such as: dot expansion, text blurring, pushing the limited amount of ink to unwanted parts. When printing on corrugated paper, the high part of the corrugation appears to have a washboard-like groove due to the pressure. Fortunately, it is filled with a resilient liner and can be avoided a little. When printing at the level, the dot gain value is serious, which will cause the full-page dot to develop to a high profile, and the dark tone part will become a serious color cast on the field, resulting in the entire picture layer being unclear, three-dimensional and not strong, and edge effects in the field, lines, and text. It doesn't look full, it's not solid, it's typeface stencil, so it's critical to use the right amount of embossing. The poor printing quality of corrugated cartons is now due to the improper printing pressure. In actual operation, in addition to the use of elastic cushioning force, more attention should be paid to the adjustment and balance of the pressure of the printing press. Generally, the pressure should be adjusted to extend the dot and the edge effect is not obvious.
Corrugated cardboard quality
It is necessary to ensure that the weight of the corrugated paperboard is stable, uniform in thickness, and the water content is reasonable and uniform to ensure good ink absorption and rapid drying. High quality cardboard is a prerequisite for high print quality.
Finally, to ensure consistent color printing between cartons, it is equally important to record and maintain the same printing parameters (printer speed, pressure level, ink viscosity, and ambient temperature, etc.).
How to maintain accurate placement
First of all, when making the plate, ensure that the position and the relative size of the plate are accurate, and that the overprint is accurate when the plate is overlapped. When the plate is mounted, the center line should be used as the reference. The pad and the plate must be installed flatly. If necessary, use the positioning. system. For most carton manufacturers, whether it is a rubber plate or a resin plate, the imposition method is used to save the production cost when making a printing plate. This imposes a high requirement on the plate-making and pasting, so it is necessary to ensure the position of the plate. accurate. The production, assembly, and correction of printing plates should be serious and careful, and the position of each plate must be accurate.
The accuracy of the print layout is closely related to the delivery of paper. If the paper feed is skewed, it will definitely result in incorrect printing position. The paper feed deflection may be due to warpage of the paperboard. In this case, warp paperboard should be handled properly. When the paperboard is produced, it can be pressed several times to make the paperboard flat, or it can be folded along the paperboard transverse pressure line. To properly reduce the printing speed. When paperboard is manually fed, it is necessary to ensure that the stacking code is neat, and that the side and rear clevisors are in proper positions, so that the cardboard can be neatly arranged, and the height of the rear lift frame is appropriate, and the suction amount is controlled reasonably. The warped cardboard printing adopts single-sheet feeding, low-speed operation, and appropriate adjustment of the amount of suction, adjusting the slot position of the printing product in time according to the layout and slotting, and correcting it in reverse. The cardboard with serious warpage is selected, and the 3-5 sheets of positive and negative stacking are flattened and reprinted with a heavy object next time, or folded in the opposite direction of the warp along the indentation line.
The adjustment of the middle pull roller is equally important. There are generally two methods for the transport of printing unit paperboard: Pull-paper-feeding paperboard and vacuum suction-roller-rolling paperboard. In the pull-paper-feeding mode, it is necessary to ensure that the position of the paper-pulling wheel of each printing unit is properly adjusted and the gap size is appropriate. In this way, it is possible to ensure that the position of the cardboard during the transfer process is accurate and that the printing position is accurate.
In addition, to ensure the accuracy of the printing layout, the design, processing level, and machine performance of the printing press are also very important. The hardness and accuracy of the transmission gears are high to ensure low wear after long-term use. And in the design, it is necessary to consider the long-term use of wear, can be fine-tuned through the center of the gear, so that the old machine to ensure the smallest gear clearance.
Author: Sun Xuefu
Source: Export Goods Packaging
