Bar code plastic gravure and its common failure analysis (2)

(b) Plate Making

In addition to the basic requirements, the following two points should also be taken into account when making bar code printing:

1. Select the original film with extremely high precision and should be compatible with the gravure printing process (the correction of the strip width of the film is compatible with the gravure printing process).

2. The lines of the parts are relatively deep and the cables are relatively dense. This is because the lightness of the network cable is light, and it cannot guarantee sufficient hiding power. Part of the light is transmitted and the reflectance is reduced. If the network cable is too thin, the network cable is easily deformed, and the edges of the printed bar are not neat, which may easily lead to difficulties in reading and writing.

(III) Printing

Bar code printing is relatively higher than ordinary plastic packaging printing requirements. The following issues should be noted during the printing process:

1. The bar code and other patterns are printed at the same time. Sometimes, the hue adjustment is required by means of ink bleed and blade position adjustment. In this case, priority should be given to the reading of the bar code. If you can't balance it, you must remake the plate.

2. The firmness and abrasion resistance of the plastic film should be given sufficient attention, especially for surface-printed packaging. If the firmness and abrasion resistance of the printing ink are not good, the ink may be detached and the barcode may be damaged during the circulation of the product. Such as failure, resulting in no reading.

Polyethylene, polypropylene, etc. are all non-polar materials. Special attention should be paid.

3. The ink should maintain a certain viscosity, the viscosity should not be too small. If the viscosity is small, the hiding power of the ink is low and the reflectance is low. In particular, the contents are dark-colored products such as watermelon seeds, pickles, soy sauce, and soy sauce. If the empty hiding power is low, the color of the contents will darken the empty color and make the empty color closer to the brown color, resulting in lower contrast. Therefore, Increase the viscosity of white ink (or other background ink) and ensure sufficient hiding power.

4. Select high-quality ink to avoid the appearance of ink and other phenomena. The ink should have a high transfer rate to ensure the density of the ink. In addition, the ink should also have sufficient high temperature stability to prevent the barcode from changing color during compounding and post-processing.

5. Strictly control the printing tension, drying temperature and other process conditions, try to avoid shrinkage changes in size.

(d) Compound

Two points should be paid attention to in the compounding process;

1. Stretching. In the compounding process, if the temperature of the drying oven is too high or the tension is too high, film stretching will occur, resulting in deformation of the barcode. Therefore, the drying oven temperature and various tensions must be strictly controlled to avoid stretching.

2. If adhesives are added during the compounding process, the film must be protected from creases at the place where the AC agent is applied. Although wrinkles can be removed in front of the composite head, due to the solvent containing ethyl acetate, wrinkles under the pressure of the coating roller and the pressure roller may cause the ink in the bar code portion to be dissolved and cause breakage. Affect the reading effect.

(v) Packaging methods

Inflatable packaging has the same appearance as ordinary packaging, so it has no other influence on barcode printing and reading, and vacuum packaging and shrink packaging should be given some attention.

1. Vacuum packaging, because the contents of the package are mostly irregular shape, vacuum packaging bag tightly attached to the surface of the contents, an irregular three-dimensional shape, the surface is not smooth, so that the bar code deformation can not be read. Therefore, the vacuum packaging inner bag should not be directly printed bar code, an additional bag printing bar code and other graphics.

2. Heat-shrinking packaging: For the heat-shrinkable packaging film used in beverages, fruit and milk bottles, when printing barcodes, consider the position of the barcode after the film shrinks; secondly, calculate the vertical and horizontal shrinkage times, and make a bar code when making a plate. The size is adjusted in advance; thirdly, a high shrinkage film with uniform shrinkage is selected. At the same time, ensure that the strips are in the same plane after heat shrinking.

(to be continued)