Corrugated cardboard two-color flexographic printing process
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1. Paper feeding
Corrugated paper has sufficient stiffness, so the flexographic printing of corrugated cardboard adopts a single sheet of paper input method, and the physical printing is finished, and it is neatly installed in the fixed position of the stacking table for manual or automatic paper feeding device to be taken one by one. material. The automatic paper feeding device adopts a fully automatic lifting platform, which can automatically adjust the height of the paper stack, and the input adopts the suction method to overcome the jamming of the cardboard caused by the unevenness of the cardboard.
2. Ink supply
The flexographic printing press uses a unique anilox roller short ink path ink supply system, which greatly simplifies the ink supply device. The ink used in flexographic printing, whether water-based or solvent-based, should have an inking circulation system that allows the ink to be recycled during the printing process to maintain a suitable viscosity. The viscosity of the water-based ink of corrugated board is generally 1-2 Pa·s.
3. Printing
Corrugated cardboard is mostly printed in two-color flexo. Some flexographic printing presses use a circular flattening method to replace the impression cylinder with an embossing plate. There are also some corrugated printing presses on which the impression cylinder is on, and the plate cylinder is on the bottom, that is, the bottom surface of the cardboard is printed, so that the arrangement can make the dust and shredded paper on the printing surface fall naturally before entering the imprint. .
The operation process of the flexographic printing process mainly includes the loading plate, the adjustment of the graphic registration, the printing pressure adjustment, the test printing, the quality inspection, the signing, and the official printing. The operation is relatively simple.
1 installed version
The flexible printing plate is fixed on the surface of the plate cylinder with a double-sided tape having strong adhesion for printing.
2 position adjustment
After the plate is pasted, a trial print is performed to adjust the position in the vertical and horizontal directions. If the position of the plate image is skewed, or if the plate is too far or horizontal to be adjusted by the adjustment mechanism, it must be corrected by moving the plate relative to the plate cylinder. It is not until the graphic printing is accurate that it can be officially printed.
3 printing pressure adjustment
The printing pressure of a corrugated board press is determined by the degree of contact of the impression cylinder with the printing plate. Printing pressure has a destructive effect on the compressive strength of corrugated board. Therefore, in the printing operation, the minimum printing pressure should be used to complete the transfer of the ink, and the corrugated board should be evenly stressed, and the compressive strength will not decrease or decrease little.
4 trial print
Samples of the trial printing, after the check of the printed graphic content, the inspection of the printing materials and graphic specifications, the check of the color and color, and the quality analysis, confirm that each data or sample meets the construction requirements and meets the technical data processed by the customer. It can be sent to the production manager for verification and signed for printing.
4. Indentation and slotting of corrugated board
Corrugated board printing mostly uses a flexographic printing slotting machine to perform printing, indentation, and grooving on one machine at the same time.
1 crepe cardboard indentation
The main function of the indentation is to accurately bend the corrugated board at a predetermined position to achieve an accurate inner dimensions of the carton.
The different relationship between the direction of the line of the pressing line and the orientation of the corrugation can be divided into a longitudinal pressing line (indentation line parallel to the corrugation direction) and a transverse pressing line (indentation line perpendicular to the corrugation direction).
The printing and grooving machine adopts a circular indentation process, and the pair of stampers rotate in a disk shape, and the cardboard passes between the pair of stampers to leave an indentation. The depth of the indentation can be changed by adjusting the gap between the die and the punch.
2 slotted
The so-called grooving refers to cutting a corrugated cardboard to make a gap that is easy to fold. The width is generally 1 mm for the thickness of the cardboard (sometimes considered to be twice the thickness of the cardboard).
There is a close relationship between the slotting of the carton and the indentation, and it has a direct impact on the size accuracy of the carton and the appearance of the carton. The center line of the slot should be aligned with the center line of the indentation as much as possible, and the deviation of the front, rear, left and right should be as small as possible.