Carton paper printing some failure phenomenon (on)

At present, small and medium-sized packaging containers, such as beer cartons, beverages, fruit and other food cartons, have more and more products that use white paper for color printing. This is a commodity economy development trend. The preprinting process of the carton has a greater improvement than printing directly with corrugated cardboard, and the layout printing structure and printing adaptability are also broader. However, as with other printing processes, the use of offset presses or letterpress printers to print various cartons of paper or cartons, tape products, will inevitably encounter some problems, affecting the quality of the product's printing. Therefore, correct understanding and understanding of some of the fault phenomena in the printing process, and the good printing operation and process technology, in order to better improve production efficiency and product quality.

I. The phenomenon of ink stick caused by uncomfortable printing pressure

When there is a serious situation in the circumference of the blanket cylinder, due to excessive roller separation, the surface of the cylinder is caused to slide and rub against the ink marks. This is a situation; the second situation is due to the use of a hard package. The lining and embossing are so large that the backlash of the gear is too large, so that the gears vibrate after the roller is pressed, and the sliding friction occurs on the surface of the roller to cause the ink bars. In the fourth case, the plate roller and the blanket roller The pressure between the two is too great, so that the blanket is squeezed to form a large frictional slippage, which causes the longitudinal deformation of the screen mesh to expand and cause ink bars. The above situation should be replaced by roller bearings; adjust the packing material characteristics; reduce the center distance of the roller, so that the gear meshing backlash is less than 0.1mm; according to the specifications of the equipment, set the pad thickness, to avoid excessive pressure conditions Appear to prevent the phenomenon of ink sticks.

Second, roller bad teeth caused by overprinting failure

When the tooth surface of the roller crushes is worn and deformed, the pressure of the clenching teeth is uneven and insufficient. When the printed sheet enters the clenched teeth, slippage is likely to occur in the printing, resulting in inaccurate overprinting of the product, and in particular, the printing plate surface is affected by ink. When the ink viscosity is also large, overprinting is more likely to occur. In this regard, the solution is to remove the severely worn teeth and replace them with new ones. The uneven pressure on the teeth and insufficient teeth will be adjusted so that the entire tooth surface will be tightly pressed against the edges of the paper; Too large, moderate dilution adjustment with additives to reduce the viscosity of the ink; for printing spot color inks, the ink hue can be appropriately deepened to make the printing ink layer thinner, which can reduce the viscosity of the ink, Meet the printing hue requirements. In addition, the printing pressure can be appropriately reduced to prevent overprinting of the printed sheet due to slippage during imprinting.

Third, the printing pressure caused by excessive dirty version and paste phenomenon

When the pressure of offset printing is too high, the frictional force of the blanket facing the surface of the printing plate will inevitably increase, causing the abrasion and destruction of the plateau grain, the hydrophilicity of the blank area mutates, and the ink is easily attached and transferred to the ink. On the product, this situation is a dirty version. In addition, the printing pressure is too large, the expansion and contraction deformation value of the blanket when the pressure is also large, the transfer of the imprint is also easy to produce deformation, especially the printing of dots and small text, there are often paste the ills. If it is a letterpress process to print small Yin Yin, Yin Zi, Yin Tu page, the performance of such cases is more obvious. Therefore, to prevent the occurrence of dirty plates and stencils, it is necessary to accurately adjust the printing pressure. It is necessary to control the thickness of the pad and the center distance of the rollers according to the specifications of the equipment.

Fourth, ghost pressure caused by printing pressure does not cause discomfort

When the pressure between the blanket cylinder and the embossing cylinder is too large, the displacement of the blanket is increased correspondingly. Therefore, the ink layer cannot be restored to the original state immediately after the transfer of the ink layer, and thus the printing roll When the cartridge is imprinted, it is easy to generate a slight difference in position, resulting in ghosting. In this regard, it is appropriate to reduce the pressure of the roller and reduce the expansion and contraction coefficient of the blanket during imprinting to prevent ghosting failure. In addition, for the use of aging blankets, should be replaced with a new blanket for printing to eliminate print ghosting failures.

Fifth, the printing ink pressure caused by discomfort caused by printing

When the pad is uneven and the pressure is uneven or insufficient, bad contact occurs between the plate and the rubber, between the rubber roller and the platen, or between the plate and the pad (the relief process), which affects the layout. The uniform and full transfer of the ink layer can easily cause the ink on the layout to be light and fade. In order to avoid this unfavorable situation, it is necessary to turn off the printing technology of "Sanping", and to protect the surface of the embossing roller to prevent it from losing its flatness due to damage and deformation, and to maintain uniform and sufficient printing pressure. Efficient measures to eliminate ink coloring of printed products.

VI. Out of powder, lint, blistering and peeling caused by poor surface strength of white paperboard

When the surface strength of the whiteboard paper is poor, it is likely to cause powder fall off during printing, hair loss, blistering, and peeling failure. Falling powder refers to the fact that the paper surface falls off the powdery material, such as paint, fillers, pigments, etc., from the paper surface. Lint off means that the fibers on the paper are peeled off from the surface of the paper during the printing process. Paper blistering and peeling means that during the printing process, the outer surface of the paper, under the action of external forces such as the peeling force of the printing and the adhesive force of the ink, causes the coating, the surface layer and the low pulp fiber structure of the paper to split and cause blistering or peeling. phenomenon. From a print quality point of view, the use of high surface strength, good quality paper, to avoid paper off, pulling, blistering and peeling quality problems, improve product printing the best choice. But what kind of paper is used for printing is not always what the printing factory can determine. Some common products, customers only require the use of low-end white paper to print. This requires that some necessary measures be taken from the printing process in order to prevent the occurrence of printing quality failures. According to the experience of the printing production process, the paper with poor paper surface strength can take some measures to reduce or avoid the occurrence of paper powder falling, hair pulling, blistering and peeling quality failures.

1. Adjust the viscosity of the appropriate ink. Papers with poor surface strength on paper, if printed with high-viscosity inks, are most prone to powder failures, naps, blisters, and peeling quality problems. In this regard, additives suitable for the printing process conditions may be selected to adjust the flowability and viscosity of the ink in order to reduce the adhesion and stripping tension of the ink layer to the paper surface during the printing process. In the past, when the authors reprinted the whiteboard paper (field layout) in the production process of the machine, severe powder falling, blistering, and peeling failures were encountered. First, the detackifier was used to adjust the viscosity and flowability of the ink. The problems of powder dropping, blistering and peeling were solved, but the printing ink effect was very unsatisfactory, the layout was very obvious, and the drying speed was also slow. Later, the use of bright oil to adjust the flow of ink, not only play a role in reducing the viscosity of the ink, and the printed product is full of ink, high brightness, good visual effects, drying speed is also fast. Therefore, the selection of suitable additives according to the printing characteristics is a very important technological measure.

2. Adjust the proper printing pressure. If the printing pressure is too light or uneven, the ink layer on the plate cannot be completely and evenly transferred to the surface of the paper, and the printing defects of the printing are likely to occur. However, if the printing pressure is too heavy, the coating layer and the fiber structure on the paper surface are easily destroyed, and powder falling, linting, blistering, and peeling quality defects easily occur. Therefore, the use of uniform and appropriate printing pressure is an important condition for achieving good ink transfer, and it is also one of the technical measures to prevent the occurrence of undesirable problems.

3. Adjust the appropriate printing speed. In the daily production, if the cardboard with poor surface strength is printed at a higher speed, the phenomena of falling powder, pulling hair, blistering, and peeling quality will obviously increase. On the contrary, if the speed of the machine is lowered for printing, this failure phenomenon will be significantly reduced. This is because the printing speed is high and the peeling tension during the printing process is also large, so that the ink layer with a sticky layer on the printing surface is not quickly, evenly, and completely absorbed by the paper surface when pressed or separated, but it is easy to speak on the paper surface. The partial coating or fiber pulls off. Therefore, paper with poor printing surface strength should be printed at a lower speed, which is beneficial to reduce or avoid the occurrence of powder failure, nap, blistering, and peeling quality failures.

4. Select the appropriate machine for printing. What type of printer is used for printing on paper with poor surface strength has a great influence on the printing quality. For example, the letterpress process is used as an example. If a flat and flattened machine is used to print, the ink layer on the print sheet and the plate surface are in contact with and separated from each other at the same time. Thus, the greater the separation area, the greater the tension when peeling. The coated layer or fiber on the surface is easily pulled off. In a circular press or circular press structure, the contact between the printed sheet and the ink layer on the plate is linear, and the tension when the printed sheet is peeled off after absorbing the ink is also small, and it is not easy to destroy the paper surface. Therefore, for the paper with poor surface strength, printing with a circular press structure will help improve the printing quality of the product.

5. Reasonably arrange the printing sequence. The reasonable arrangement of the printing color sequence is an important part of preventing the paper from falling or pulling. Therefore, for the paper with poor surface strength, a small layout should be printed before the large printing surface; Ink (non-color overlay printing plate product). If a multi-color machine is used to print an extra color group, the front color group may not be used, so that the paper can be left empty past the preceding color group or the front color group can be used to imprint or “overwater” the printed sheet once. Significantly reduced when the print off or pulling hair phenomenon.

6. Adjust the paper with poor surface strength for printing small products. For some paperboards with poor surface strength, despite various methods, they still cannot solve the problem of powder and paper blistering. This is because the adjustment of the ink viscosity and peeling tension is after all limited, and there is no certain sticky ink, and it is difficult to achieve normal printing. For example, when we once printed a full batch of white paper (breast box paper) that absorbs ink, the viscosity of the ink has been adjusted to the minimum limit. However, there are still blisters on the surface of the printing paper, which seriously affects the quality of the product. Later, we adjusted this kind of paperboard to print products with less ink absorption, and no paper blisters appeared. Therefore, according to the characteristics of printing products, choosing the right cardboard for printing is also one of the important measures to prevent quality problems.