Corrugated cardboard two-color flexographic printing process

1. Paper feeding

Corrugated paper has sufficient stiffness, so the flexible plate printing of corrugated cardboard adopts a single sheet input method, after the printing is physically aligned, Advanced Flexo Printer is neatly installed in a fixed position on the stacking table for manual or automatic paper feeding device material. The automatic paper feeding device adopts a fully automatic lifting table, which can automatically adjust the height of the paper stack, and the input adopts a suction method to overcome the phenomenon of cardboard jamming caused by uneven cardboard.

2. Ink supply

The flexographic printing machine uses a unique anilox ink roller short ink path ink supply system, which greatly simplifies the ink supply device. The ink used in flexographic printing, whether Flexo Printer Slotter Machine is water-based or solvent-based, should have an inking circulation system to circulate the ink during the printing process to maintain a suitable viscosity. The viscosity of corrugated paperboard water-based ink is generally 1-2Pa · s.

3. Printing

Corrugated cardboard is mostly printed with two-color flexo. Some flexographic printing presses use round flattening printing methods, replacing the impression cylinder with an impression plate table. In some corrugated cardboard printing machines, the impression cylinder is on the top and the plate cylinder is on the bottom, that is, the bottom surface of the cardboard is printed. This arrangement allows the dust and shredded paper on the printing surface to fall naturally before the cardboard enters the imprint. .

The operation process of the flexographic printing process mainly includes plate installation, adjustment of graphic registration positioning, printing pressure adjustment, trial printing, quality inspection, signing and formal printing. The operation is relatively simple.

① Install version

The flexible printing plate is fixed on the surface of the printing plate cylinder with a double-sided tape with strong adhesive force for printing.

② Position adjustment

After the printing plate is pasted, a trial printing is required to adjust the vertical and horizontal plate positions. If the position of the printing plate is skewed, or the longitudinal or horizontal deviation of the printing plate is too large to be adjusted by the adjustment mechanism, it must be corrected by moving the relative position of the printing plate and the printing plate cylinder. Flexo Printing Slotting Machine will not be officially printed until the graphic overprint is accurate.

③Adjustment of printing pressure

The printing pressure of the corrugated cardboard printing machine is determined by the contact degree of the impression cylinder to the printing plate. Printing pressure has a destructive effect on the compressive strength of corrugated cardboard. Therefore, in the printing operation, the minimum printing pressure should be used as far as possible to complete the transfer of ink, and ensure that the corrugated cardboard is evenly stressed, and the compressive strength will not decrease or decrease very little.

④Trial printing

Samples for trial printing, after verification of the graphic content of the printing plate, inspection of the printing materials and graphic specifications, verification of the color and color base, and quality analysis, confirm that each data or real sample meets the construction requirements and the technical data processed by the customer. It can be sent to the person in charge of production for verification and signed for printing.

4. Indentation and slotting of corrugated cardboard

Corrugated cardboard printing mostly uses a flexographic printing and slotting machine, which completes the printing, creasing, slotting and other processes on one machine at the same time.

①Indentation of corrugated cardboard

The main function of the indentation is to make the corrugated cardboard bend accurately according to the predetermined position, so as to achieve the precise internal dimensions of the carton.

The relationship between the direction of the indentation line and the direction of the corrugated flute, the indentation can be divided into longitudinal indentation line (indentation line parallel to the corrugated flute direction) and horizontal indentation line (indentation line perpendicular to the corrugated flute direction).

A circular indentation process is used on the printing and grooving machine, and the pair of stamping dies rotates in a disc shape, and the cardboard passes through the pair of stamping dies to leave indentation. By adjusting the gap between the female mold and the male mold, the depth of the indentation can be changed.

②Slotting

The so-called slotting refers to cutting a notch in the corrugated cardboard to facilitate folding. Its width is generally the thickness of the cardboard plus lmm (sometimes it may be considered to be twice the thickness of the cardboard).

There is a close relationship between the slot of the carton and the indentation, and it has a direct impact on the dimensional accuracy of the carton and the appearance of the carton. The centerline of the groove should be aligned with the centerline of the indentation as much as possible, and the deviation between the front, back, left and right should be as small as possible.