Analysis of Flexo Printing Quality Control of Soft Labels

The control link of printing quality of flexo cigarettes With the improvement of people's awareness of environmental protection, flexo printing technology has become more and more sophisticated, and due to the intensified competition in the packing and decorating of the tobacco industry, the new printing method of flexo printing is widely used in cigarette marking.

Flexo printing is favored by many printing factories because of its high speed, low production cost, and consistent color consistency of batch products. However, the standard requirements of cigarette printing are relatively high, which puts high requirements on the quality control of cigarette marking.

The quality control of cigarette label printing includes three steps: the detection of raw and auxiliary materials, the control of production process, and post-press processing. This article focuses on the quality control of soft-printed soft-label cigarette packs.

l. Inspection of raw and auxiliary materials

Testing of raw and auxiliary materials is a prerequisite for printing. Without qualified raw and auxiliary materials, it is difficult to produce high-quality prints. The printed raw and auxiliary materials mainly include paper and ink.

1) Detection of paper

(1) Whiteness: The whiteness of the paper should be more than 85%. If the paper is yellow during dyeing, bluing will affect the hue of the finished product.

(2) Tension: The tension of the paper must be stable, and the paper with unstable tension will be misprinted during the printing process.

(3) Tearing degree The tearing degree of the paper must be qualified. Too low a tearing degree is liable to cause a paper break under a large printing tension.

(4) The paper with low stiffness is difficult to be collected when it is cut off after printing, which may cause flying paper.

(5) Moisture content The water content of the web is generally about 6%. The paper with high water content will be deformed too much after printing and drying, which will affect the overprinting; the paper with low water content will easily cause after the printing is cut. Static electricity.

2) Ink detection

(1) Saturation It is advisable to use a little ink for scratching test, and then measure the colorimetric value with a colorimeter to judge whether or not it is acceptable.

(2) Viscosity The flexographic ink viscosity determines a lot of printability of the ink. If the viscosity is too high, ink transfer difficulties may occur. If the viscosity is too small, the ink layer may not be thick enough.

(3) Drying speed: The ink with fast drying speed will dry out when the printing plate is still in contact with the paper in the future, causing stencil of the cable and the dirty version in the field; the ink that dries slowly will remain after the paper passes through the oven. The undried ink, when it passes through the paper guide roller again, becomes dirty.

2, the production process control content

The control content of the production process should include the following aspects:

1) Overprint. The overprint requirements for smoke labels are relatively stringent. Printing should meet the requirements of higher standards than the national standards. The main parts are less than 0.15 ram, and the minor parts are less than 0.25 mm. Because the design of cigarettes is beautiful, overprinting errors will affect the appearance.

2) The ink bar. Flexo printers tend to produce ink sticks when printing cigarette labels. The ink sticks not only affect the printing quality, but also affect the aesthetic appearance of cigarette packaging. The production of ink bars may be caused by the following reasons: a. Gear engagement is not good; b. Machine vibration; c. Improper pressure adjustment; d. Improper use of media. The operator can start from these four aspects, carefully investigate and find out the reasons. A high-strength plate material of about 2era can be widened at both ends of the plate to reduce the above-mentioned factors and eventually eliminate the ink bars.

3) Hue of spot color inks. Whether the color of the printed matter of the smoke label and the color of the proof is attached depends largely on the hue value of the spot ink, and is represented by L, a, b, E. L represents the brightness of the spot color ink, and L is a positive value indicating that the color is brighter than the sample, and a negative value indicates that the color is darker than the sample. a represents red, a positive value indicates that the color is redder than the proof, and negative indicates greenish. b stands for yellow. A positive b indicates that the color is yellowisher than the sample, and a negative value indicates bluish. E represents the total color difference value, and E is required to be less than or equal to 3.5.

4) Barcode. If the bar code is very different from the proofs, the reader of the mall cannot recognize the type and price of the product. The bar code must be printed with light pressure, insisted on frequent detection, and often contrasted. If the value is outside the plus or minus 24, change the plate immediately.

5) The layout is neat. Smoke label printing requires a clean layout, no dirty spots, ink spots, printing pressure size is appropriate, real. The Lg version has no eyelid phenomenon. The network cable is rich in layers and can't drop points. Small, clear text, clear lines, no distortion.

6) Wear resistance. The cigarette label prints are packed at a high speed on the packaging machine. If it is not to be scratched, it requires a certain degree of wear resistance on the surface. It is advisable to take a soft label and tear it into two sections, stacking and rubbing each other. If scratches do not occur after 2O rubs, the wear resistance is very good.

3, finishing after printing

1) Cutting. After finishing the printing on the printing machine, the papers should be sorted and arranged according to the size of the rules and regulations, and the papers with the same rules should be picked up and put together. Each piece of 1,000 pieces of paper should be cut. In the cutting process need to pay attention to a. The knife is sharp. If the working time is too long, the knife edge is worn bluntly, and the edges of the product cut out are hairy. The new knife should be replaced or the raw edges should be ground with sandpaper. b. Whether the blade has a wound. The edge of the product cut out with a cutter of "I95" has a scribe, not only the shadow D is packed in cigarettes but also the appearance of the product D.

2) Organize. The cut tobacco labels should be placed separately with or without defects. No faulty cigarettes should be directly over-weighed to check whether their number is accurate: faulty cigarettes should be individually provoked to pick out unqualified products.

3) Packing or packing. If there is residual odor remaining after finishing the printed matter, it must be left for a period of time before the odor disappears and then it is packaged or boxed. For slightly odorous products, apply a breathable kraft paper instead of a plastic bag to seal the package.

In short, in order to produce exquisite printed matters, quality control work must be conducted at all levels, and all specific tasks must be coordinated and coordinated. As long as every aspect of the process is done, it will be able to produce qualified prints.

Reprinted from: the world of print: Huang Guangwei