Discussion on the indentation of packaging carton

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With the development of society and the continuous improvement of people's living standards, consumers not only require the internal quality of goods, but also put forward higher requirements for the packaging of goods. This includes not only the requirements of commodity packaging and decoration design, but also the requirements of packaging post press processing quality. The part of the printing material is compacted to produce traces, which makes it have a certain concave convex feeling in space, which is called indentation

indentation processing technology was initially only used for the molding of paper packaging boxes, and then gradually applied to the surface processing of all kinds of printed materials, especially the surface finishing processing of high-grade cartons, cartons, trademarks, works of art and other surfaces. Now, indentation technology has been one of the important means to realize packaging design. It not only plays an important role in the final quality and effect of packaging, but also improves the artistic effect of printing to a great extent, endows printing with new functions, and has become an important means of printing value-added and promotion. Therefore, the indentation technology has been paid more and more attention by the industry in recent years, and the scope of use is becoming wider and wider. However, in the die-cutting and indentation process, the maintenance principle of a fatigue testing machine often appears, which is worth making. This paper introduces a series of problems, which affect the smooth progress of production. Therefore, this paper takes the common problems of the horizontal flat die-cutting machine in the die-cutting and indentation production as an example to analyze, hoping to be helpful to the actual production

I. common indentation problems

the paper feeding and receiving principle of the full-automatic horizontal flat die-cutting machine is similar to that of the offset press. The faults are not analyzed here, but the common problems of the die-cutting part are analyzed below

uneven pressure

my fatigue testing machine is characterized by high load, high frequency and low consumption. We know that indentation is a line mark caused by folding, extrusion or wrinkle. The whole process of indentation is: design proofing, typesetting, plate mounting, pad plate, start and finish the finished product. In the manufacturing process of folding carton, the line mark is a controlled deformation on the cardboard. The principle of indentation is that the cardboard is pressed between two fixed surfaces (concave mold and convex mold), and the internal fiber structure of the paper is damaged, resulting in partial delamination of the paper and the formation of concave and convex line marks on the outside. When the pressboard connected by the indentation is folded at 90 degrees or 180 degrees, the internal fiber bonding (cohesion) of the paper will be completely separated

there are generally two cases of uneven pressure in the process of indentation: one is slightly uneven. If the pressure is slightly uneven, it may be due to the uneven distribution of die-cutting knives and lines (steel knives and steel wires), which causes the force deflection of the moving platform during die-cutting. At this time, a balanced knife line should be added to the die-cutting plate to make the force on the platform uniform. It may also be affected by the fiber direction of the paper. When the paper is transverse and perpendicular to the knife line, the indentation effect is ideal. The other is serious unevenness. If there is serious uneven pressure at the four corners in front of and behind the platform, it is mainly caused by the inconsistent height of the four connecting rod swing rods supporting the moving platform. At this time, open the shield of the die-cutting base and check whether the swing rods are worn. If the wear is serious, replace them. Otherwise, adjust the four pressure adjustment inclined irons until the pressure is consistent

wire burst (color burst)

when the steel wire of the indentation die (punch) is pressed into the groove, the cardboard is subjected to three forces: pressure, tension and surface tension. These three forces not only cause permanent deformation of the paperboard, but also reduce the cohesion between the fibers in each layer of the paperboard. When folding, the surface of the paper is under tension and the inner layer is under pressure. If the pressure exceeds the cohesion between the paper fibers, the fibers inside the paperboard will break, and the paper will become soft and easy to bend at the folding position. But the pressure should not be too great. When the tension of the cardboard is exceeded, the outer monster will break (the cigarette box will burst when packed). In the process of die cutting, the surface tension of paperboard will increase with the increase of the number of indentation on the paperboard. Burst refers to the paper cracking at the indentation when the product is die-cutting or the finished product is folded. This is a common problem in indentation, especially in dry weather. It should be analyzed according to the specific situation:

1. The paper is brittle and has low water content, especially the paper polished at high temperature, and the explosive line during die cutting. At this time, wet the paper before die-cutting, and use a water filter to water the back of the paper, increase its water content, make it slightly flexible, and then put it on the die-cutting machine. After die-cutting, if the line bursts when pasting the box, you can wipe water at the crease to alleviate the line burst condition

2. There are large areas of dark colors such as blue or black on the surface of the printed matter, and explosive colors and lines after die cutting. When printing, add no or less ink additives to the dark ink to strengthen the adhesion of the ink on the paper and reduce the phenomenon of Color Explosion and line explosion

3. When the thickness of paper (board) is too large, it is easy to produce wire burst. At this time, the height of die-cutting steel wire should be selected reasonably

4. It is easy to cause wire burst after the steel plate is padded with paper. At this time, the paper should be thinned

5. When the pressure of the die-cutting machine is too high, it is easy to cause wire burst. At this time, reduce the pressure to make the waste edge just separate

6. The indentation die or bottom paper is too thick and the indentation is narrow, which is easy to lead to wire burst. The indentation die with appropriate thickness should be selected, and the indentation width should be moderate

7. The paper powder falling from the cut accumulates in the groove, which is easy to cause wire burst. The operator should clean the paper and foreign matters in time

the indentation line is irregular (not smooth)

the indentation line is a process that uses steel wire to press out traces on the substrate by stamping, leaving grooves conducive to bending. The main reason for the irregular indentation line is that the indentation groove on the steel wire pad is too wide, and the position of the cardboard indentation is not fixed; The thickness of steel wire pad is insufficient, and the groove angle is not standardized, resulting in redundant rounded corners; The tightness of knife arrangement and fixing is not appropriate, the steel money is too tight, and the bottom cannot achieve ideal contact with the plane of the pressing plate, so it is easy to twist during indentation; The steel coin is too loose, and it is easy to move left and right when indenting. The elimination method is to replace the steel wire pad paper, and the width of the indentation groove is appropriate; Increase the thickness of steel wire pad and trim the groove angle; Adjust the position of the formwork; When arranging and fixing knives, the tightness of the knife should be felt by hand for many times

II. The process of embossing printing and indentation is completed at one time

in some parts printing and decoration printing processes, it is often necessary to add some indentation effects, such as notes, letters, book covers, invitation products and some decoration printing products (with indentation). According to the traditional printing process, the printing process is completed first, and then the indentation process. In this way, the production efficiency and product overprint quality of printing are not satisfactory. Through production practice and exploration, the author's team has innovated and improved the process of printing with indentation process, so as to realize the production process of one-time printing for products that originally needed to be completed in two processes, which greatly improved the printing efficiency and product quality. The operation process of the process is roughly as follows:

1. Improve the lining process. In order to quickly and conveniently realize the one-time completion process of printing and indentation, the traditional embossing lining process must be improved, that is, the inner lining must be reduced to 0.7mm, the padding inside the lining layer must be reduced to an appropriate amount, and the outer lining layer must be increased accordingly. In this way, after the thickness of the outer lining is increased by 0.7mm, the local increase and decrease adjustment can be carried out very conveniently, which is convenient to quickly realize the process transition of one-time printing. Therefore, the increase and decrease adjustment of the outsourcing liner is to comply with the requirements of the characteristics of the embossing light and dark one-time printing process, and is an important measure to improve the printing efficiency and quality

2. Selection and correct adjustment of inking roller. Set printing and indentation in one machine to complete the embossing at the same time. Its main principle is to adjust the printing layout to a slight difference between the height of the dark mark line layout and the lining surface, so that the printing layout can get uniform ink brushing and printing pressure. The dark mark or dotted line knife layout can't get ink because it is lower than the printing layout, which is the basic requirement to realize the light and dark embossing at the same time and ensure the print quality. To meet the above printing conditions, the accuracy of the equipment and the quality of the inking roller play a decisive role. In order to obtain a more uniform inking of the printing plate, the dark mark plate will not be stained with the slightest ink; The ink roller shaft hole on the printing machine should maintain the center degree, so as to avoid uneven rolling of the ink roller affecting the uniformity of the ink. The eccentric and enlarged shaft hole caused by wear and tear should be repaired in time and rounded to eliminate the phenomenon of rubber jumping and slipping and ensure normal inking

in addition, the colloid of the inking roller and the shaft head should also maintain a good center degree to prevent the existence of eccentricity from affecting the normal ink receiving and uniform inking. At the same time, it is required that the hardness of the ink roller colloid should be appropriate, and it is easy to cause glue slip and uneven ink distribution; If it is too soft, it is easy to deform due to rotating friction and thermal expansion, which will cause the dark mark layout to be stained with ink and affect the product quality

3. Adjustment of layout height. For printed notepaper products, as long as the letterhead layout is padded 0.7mm higher, it can form a height difference with the dark mark layout, which is convenient for the surface printing layout to receive ink, and the dark printing layout can't get ink because it is lower than the surface printing layout. As the surface printing layout increases, the corresponding outer lining will be thinned accordingly. For this reason, a 70g kraft paper should be used as the outer lining, but a piece of white paper with moderate width and thickness of 0.7mmm should be pasted on the back of this kraft paper where it corresponds to the dark mark plate, so that the pressure of the light and dark plate of the print can be uniform and the printing quality can be guaranteed. For products that need to be creased for printing, such as books and periodicals cover and spine, as long as the bottom of the indentation steel blade is ground down to about 0.7mm lower than the surface printing plate with a grinding machine, and then the indentation blade is directly combined with the surface printing plate to form a plate, so that the steel blade is slightly lower than the surface of the surface printing plate without inking during printing. However, it is padded with hard padding with an appropriate thickness with the lining part, such as white board and paper strips, so as to meet the indentation conditions and realize the one-time printing process

to sum up, the use of one-time printing indentation process not only greatly improves the printing efficiency, but also significantly improves the overprint quality of the product. At the same time, it also reduces the loss of raw materials and improves economic benefits. For many years, in the production practice of temporary machine, the author has adopted one-time processing technology for the products with dark marks, so that the products that originally needed to be completed by two processes can be completed at one time. The implementation effect of this process has also been well evaluated by peers and customers, and it is a technical improvement with popularization and use value

III. The latest development of indentation technology

1. Indentation technology is more widely used. Thick paper folding, invitations, tickets, greeting cards, color laser prints, thick media inkjet prints, coupons, tickets, receipts and other traditional applications are more in-depth, and they are widely involved in new fields such as wine boxes, advertisements, half fold business cards and so on

2. Bump and indentation tend to be completed at one time. Die cutting and indentation technology also plays a very important role in the packaging and molding of cigarette labels, because it is directly related to the packaging quality of cigarette labels and whether it can meet the requirements of cigarette packaging machines in cigarette factories. The production of cigarette label, wine label and other ultra large packaging boxes is often mass and repetitive production. On the premise of ensuring product quality and greatly improving mechanical properties, the combination of concave convex and die-cutting indentation process can complete the production of cigarette label at one time, which can not only save the investment of machinery and equipment for the company, but also

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