Folding Drawer Paper Boxe concave to soft, what should I pay attention to before printing?

Folding Drawer Paper Boxes"concave to soft", what should I pay attention to before printing?

At present, gravure Folding Drawer Paper Boxesproducts generally use a screen line count of more than 150 lines/inch, while flexo printing Folding Drawer Paper Boxesproducts mostly use a screen line count of 100 to 120 lines/inch. If the printing method of a Folding Drawer Paper Boxesproduct is changed from gravure printing to flexo printing, the printing effect of color blocks, lines, text, graphics and other information can be basically the same, but in terms of mesh image adjustment, gradient to absolute screen, etc. Flexo printing needs to do some special processing in order to achieve a similar effect to gravure printing to meet customer requirements.

Pre-press design considerations

1. Size deformation processing of imposition files

"Concave-to-flex" PE film Folding Drawer Paper Boxesjobs do not need to worry about the registration problem, as long as the size of the job and the requirement of equal distribution in the circumferential direction of the printing plate cylinder, determine the appropriate imposition method and matching plate cylinder size, and do The tensile deformation treatment of the imposition file in the circumferential and axial directions (usually, the circumferential dimension is elongated by 0.5% to 2%, and the axial dimension is reduced by 0.3% to 1.2%).

2. Processing of small characters, thin lines and barcodes

Special attention should be paid to the handling of small characters, thin lines and barcodes for Folding Drawer Paper Boxesproducts that are "concave to soft". Under normal circumstances, the small positive characters of gravure Folding Drawer Paper Boxesshould be thickened by 0.01mm, the individual small negative characters should be thinned by strokes, and the barcode should be thinned by 0.02~0.03mm. If it is converted into a flexo printing process, the processing method is opposite to that of gravure printing, to prevent the thin yang line and the small yang character from expanding and thickening, and the thin yin line and the small yin character merging.

In order to ensure the reading level of the barcode, the best processing data under the flexo printing process can be determined by testing the barcodes of different colors, fineness and proportions, combined with anilox rollers with different lines. The following data is for reference: the scaling ratio of the barcode is 90%~110%, the left and right safety clearances are 4mm left and 3mm right, and the narrowing is 0.07~0.1mm. It is suitable for anilox roller printing with 500~800 lines/inch. Colors are mainly black and dark blue. In terms of thin lines, if you use an anilox roll of 1016 lines/inch (BCM value of 2.0) to print, you can get a positive line with a width of 0.018mm and a negative line with a width of 0.053mm, but this is close to the limit value.

3. Trap and Registration

The registration accuracy of the satellite flexo printing machine is high, and the Folding Drawer Paper Boxesproducts of "concave to soft" should give full play to this advantage. Usually, the trapping value of flexographic Folding Drawer Paper Boxesproducts is 0.1 to 0.3 mm, and the specific value depends on the product. For example, the size of the trapping value can be determined in combination with the distribution law of the layout graphics and the situation of the imposition.

It should be noted that the circumferential registration is the key point of consideration. If the products with multi-splicing in the axial direction can be dislocated on the layout, it is conducive to registration and can alleviate the problem of bars.

4. Processing of field and dot gradient

Gravure printing has no worries about dot increase, while flexo printing has to face the problem of dot increase, so when the solid and dot gradient appear on the same layout, special attention must be paid. The following is a comparative analysis of the gravure and flexo printing processes by taking the gradient of monochrome dots as an example.

Gravure printing process: using a printing plate of 150 lines/inch, the minimum dot is 1%, the solid and dot gradient can be printed on the same version, and the required solid density can be achieved by controlling the depth of the printing plate (35-50 μm), and from The effect of on-site gradual change to absolute net is also guaranteed, and stable mass production can be achieved.

Flexo printing process: CDI plate-making is adopted, the number of screen lines of the printing plate is 150 lines/inch, and the minimum dot is 1%. The solid density of the printed product is mainly determined by the ink storage capacity (BCM value) of the anilox roller, and the plate tape, plate and ink also have a certain influence on the solid density. In terms of dot gradation, flexo printing has to face the problem of dot increase. After the minimum dot is increased by 1%, it reaches 5% to 8%. If it jumps directly to 0, a visual fracture will occur. At the same time, the line number of the anilox roller that can match the high screen line number and small dot printing plate must be high, and its ink storage capacity is bound to decrease, and the solid density in the gradient pattern on the printed product will also be limited. Therefore, 150 lines/inch of screen lines and 1% minimum dots are generally not used in Folding Drawer Paper Boxesflexo production at present.

The above is a comparative analysis of monochromatic flexo printing and gravure printing from gradient to perfect screen. This problem also exists in the flexo printing of multi-color overprinting from gradient to perfect screen printing. It can be said that the current weakness of flexo printing Folding Drawer Paper Boxesis "gradation to no screen, control of dot increase, and the use of low-screen line number printing plates". The author has tested the flexo printing sanitary packaging bag products, using 120 lines/inch and 150 lines/inch printing plates respectively, with a minimum dot of 3%, and using an anilox roller of 1016 lines/inch to match the flexo printing samples with 175 lines/inch. Compared with the gravure proofs of lines/inch, the overall effect of the 150 lines/inch flexo proofs is very close to the gravure proofs, but the defect is that the ink supply of CMYK four colors is limited, and the overall printed image is light.

If Folding Drawer Paper Boxesflexo printing companies want to improve the above situation, in addition to flexibly handling color separation according to the specific conditions of the product (for example, spot colors participate in image overprinting, shallow screen overlays, small dots and quasi-solid merging + multi-color overprinting) in addition to , you can also try to start from the following aspects: when the process conditions allow, strive to use a printing plate of 120 to 150 lines/inch; configure at least 4 anilox rollers of 1000 lines/inch or more, and the more ink storage capacity The bigger the better; the application of HD Flexo technology (the author's preliminary test thinks that the effect is good, and whether it can be used well needs to be further verified in practice). In addition, the color density of the solvent-based four-color original ink currently used in flexo printing is higher than that of gravure ink. If the color density can continue to be greatly improved on the existing basis and the overprint can be stably printed, it is specially used for the halftone image printing of fine products. , will also play a role in promoting the improvement of flexo printing Folding Drawer Paper Boxestechnology.

Precautions for plate making

The CDI plate-making process has been applied in the domestic flexographic Folding Drawer Paper Boxesfield for 10 years, with mature technology and stable plate-making quality. Flexo printing Folding Drawer Paper Boxesneeds to use a thin plate with a thickness of less than 1.7mm. At present, the 1.14mm thick laser plate is the first choice in the industry. It can produce a printing plate with 175 lines/inch and 1% minimum dots, but currently few Folding Drawer Paper Boxescompanies dare to The main reason is that the hardware is insufficient, and the actual printing effect and process control are difficult to guarantee.

The general requirements for the printing plate are a flat layout, no residual solvent, moderate viscosity and relief height, sufficient exposure, and sharp and stable dots. In addition, the durability of the printing plate is also worthy of attention. In the next few years, flexo printing will adopt high-screening printing plates and new screening technologies, which will put forward higher requirements on the service life of the printing plates. It is recommended that plate material suppliers can consider Introduce thinner plates from abroad to do some preliminary tests.

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