Corrugated carton printing method overview (on)

Nowadays, the color of corrugated carton packs is becoming more and more eye-catching. This is because corrugated carton packaging has a new task - displaying goods and promoting sales. In large-scale supermarkets, beautifully printed color cartons can attract customers' attention, raise customer interest, and stimulate purchase desires. This requires that corrugated boxes not only have the function of transport packaging, but also have excellent surface printing quality. In order to safely transport items packed in folding carton packs or plastic bags (such as liquid milk) to point-of-sales, they are usually packaged in corrugated cartons. The reason is that corrugated cartons are used in the same weight. Compared to cardboard, corrugated board is more impact resistant and can better protect the contents from impact damage. However, you may notice a considerable contradiction, that is, a finely-printed, sales-friendly folding carton or liquid milk package is wrapped in a box that is not printed or only printed with some simple text, if not Opening the box and leaving it at the point of sale, no matter how attractive the folding cartons or liquid milk bags are designed, how beautifully printed and unappealing it is. In this case, the pattern design of corrugated carton packaging is extremely important. This is why more and more corrugated cartons are now printed with patterns. At present, the printing of corrugated paperboard in China is divided into: offset printing, bonding of cardboard into cardboard, direct printing of flexographic printing, pre-printing, and several special printing methods.

1. Current main methods and characteristics of carton making at home and abroad

1.1 Offset Printing Indirect Corrugated Boxes

The process flow of offset printing indirect printing carton is: single-sided corrugated cardboard (single) ten-offset color printing printing paper (single-sheet) gluing into paperboard die-cutting grooved adhesive nail box This method uses offset printing corrugated paper Box paper, then use a single machine to rehearse the corrugated board. It can print well-designed cartons and improve the printing quality of cartons. At present, most of the high-grade corrugated boxes used for sales and packaging in China are offset printing products.

a. Offset printing corrugated box has the following advantages: 1 The printing product is very fine, and the number of screens can reach 200 lines/inch. 2 Plate making is easy. For the PS plate, the conventional plate making 3 can be surface-refined, such as laminating and polishing. The printing quality is relatively stable.

b. Offset printing corrugated boxes have the following deficiencies: 1 It is not suitable for the cardboard linkage production line. It is only suitable for single-faced corrugating machines and the production efficiency is low. 2 The production process is complicated and the production cycle is long. 3 The carton has low strength, high rejection rate and high production cost. 4 The production site is large and the labor intensity is high. 5 The printing format is limited; delivery time is not flexible enough. From the above analysis, it can be seen that offset printing indirect printing cartons is not economically cost-effective for a company. Especially for the production of bulk cartons and the production of export cartons, due to high production costs, low efficiency, long cycle times, and inability to meet production needs.

1.2 Flexo printing corrugated carton

The process flow for production of flexo-printed cartons is: Corrugated cardboard production board direct printing (flexible version) Die-cutting slotted adhesive nail box Conventional flexographic printing corrugated box process is directly printed on corrugated board, using water-based ink, Currently widely used in China's carton factory.

a. Flexographic direct printing has the following advantages: 1 The maximum width of a large-format, wide-format flexographic printing press can reach up to 2.5-2.8m. 2 The price is low, the flexographic printing plate is very resistant to printing force, and can be reused; the ink price is also low. 3 can be linked to the production, such as printing, slotting, indentation, set (sticky) box, bundling and other machines can be completed. 4 Carton strength decreases less. Since flexo printing is light press printing, it has little effect on the strength of corrugated cardboard.

b. Flexographic printing of corrugated board directly, although the printing quality is higher and the efficiency is higher, but there are three difficulties in printing the pattern comparable to offset printing: 1 The corrugated board is difficult to maintain stable during the high-speed printing process. , resulting in four-color or more excellent overlay accuracy is difficult to achieve. In multi-color printing, when the carton printer cannot guarantee sufficient multi-color overlay accuracy, carton printing cannot meet higher requirements. 2 printing pressure control. Unlike other printing methods, flexographic printing transfers ink to paper by means of flexible dots. Due to the rough surface characteristics of the corrugated board, it is difficult for the printing machine to maintain the stability of the board, so that the fine mesh dots are attached to the rough corrugated paper surface with the best printing pressure, so as to achieve the smallest dot diffusion, then it is not necessary to print fine patterns. possible. This makes most of the current flexo-printed carton printing quality in the middle and low state, can only deal with the field, lines and simple patterns of printing, which greatly reduces the carton printing quality. 3 The printing accuracy is not high, the number of conventional offset printing screens is 175 lines/inch, while the conventional screen printing lines of flexo-printing boxes are only 35 to 75 lines/inch, which is a low-precision printing method, and is most suitable for printing text lines and four-color image printing. Although the quality has improved in recent years, there are still limitations.

1.3 Pre-printed corrugated carton

Pre-printing includes two printing methods: gravure preprinting, flexo preprinting. The gravure preprinting method for producing colored corrugated cardboard boxes is: using a gravure printing machine to print on a web, after printing, the material is still received into a roll paper, and the printed web is used as a corrugated paper production line on a cardboard surface paper. Into the corrugated cardboard box, and then cut into a box with a die cutter. The method of flexo-printing pre-printed color corrugated cartons is to use a flexo printing machine to print on a web, and after printing, the web is still received as a web, and the printed web is used as a corrugated paper production line on cardboard boxes. Made of corrugated cardboard boxes, and then cut into boxes with a die cutter. The carton produced by these two methods has relatively high printing quality and molding quality, and is suitable for high quality and mass production. The process flow for the production of flexo cartons is: Web pre-printed face paper (gravure, flexo) Ten line production of corrugated composite adhesive computer slitting computer cross-cut die-cutting slotted adhesive nail box

(1) Pre-printing conditions already available

a. Pre-printing requirements for paper and ink Pre-printing has special requirements for paper, and the printed surface of coated white paper has good color expression. However, in the process of bonding through corrugated high-temperature drying tunnels, the paint will have different degrees of Changes, directly affect the color surface pattern effect, not the most suitable paper; hanging pulp whiteboard, although it can meet the requirements of the corrugated high temperature drying tunnel bonding process, but because of its rough surface, resulting in the printing pattern lost dot, false, appear Poor pressure and high ink consumption are also not ideal for preprinted paper. Practice has proved that good preprinted paper should be white cardboard, which can not only fully express the color of printed patterns, but also withstand the test of corrugated high temperature drying tunnel bonding process. Printing is inseparable from printing ink. Preprinting has special requirements on the heat resistance and friction resistance of inks. When the preprinted tissue paper is pressed flat on a corrugated paper production line and passed through a drying section, the required ink and ink is resistant to high temperature and resistance. Grinding is good, otherwise the colored surface will be pulled and the ink will be rejected. The pre-printing ink has mature experience abroad, but it was still blank in China in recent years. In recent years, Tianjin Toyo Ink Co., Ltd. has developed a pre-printed water-based gravure ink and a pre-printed water-based flexographic printing plate that can meet the use of corrugated paper production lines. Ink and Varnish. It can be used for gravure preprinting and flexographic preprinting respectively. The cost of ink is similar to that of offset printing. The preprinting ink is mainly based on aqueous ink. Water-based inks are favored by people because of their characteristics such as non-toxic, odorless, easy operation, and environmental protection. With the appearance of "green food and green products", it will inevitably require "green packaging and green printed materials" to correspond. The water-based ink of Tianjin Toyo Ink Co., Ltd. is a non-toxic ink approved by the American Food and Drug Association. This ink can be used to print green box products such as drink boxes, food boxes, medicine boxes, export packaging boxes, etc.

b. Equipment required for pre-printing Gravure Pre-printing The equipment currently in use is mainly a web gravure printing machine. This type of machine is classified according to the arrangement of the cylinder parts. There are mainly two types of machines: satellite gravure printing presses, machine-type Gravure printing machine. Among the two types of machine, the gravure printing machine has a more reasonable layout and a higher level of technology. It is the standard type of web gravure printing machine. There are also many domestic manufacturers of such equipment, such as Zhongshan Jiangnan Packaging Machinery Factory and Xi'an Aerospace Huayang Printing and Packaging Company. Flexographic preprinting The equipment currently used is mainly a roll-to-roll flexographic printing press. There are mainly three types of machines: satellite flexographic printing presses, flexographic printing presses, and laminated flexographic printing presses. Among the three models, the satellite flexographic printing machine can meet the requirement of the width and repeat length, and the constant temperature of the central impression cylinder can ensure the stability of the printing material, which is more reasonable. The domestic roll-to-roll flexographic printing equipment currently used mainly depends on imports.

c. The pre-printing of the ancillary equipment required for pre-printing must first print a pattern, and then corrugated composite bonding on the upper corrugated paper production line, and then cut off, this time we must consider the factors of the pattern, the previous computer corrugated paper production line cutting mostly only fixed length Cross-cutting, so it must be installed on the cross-cutting knife photoelectric tracking cross-cutting control system, its main control mechanism is to identify the corrugated board printing pattern on the cross-cutting logo, the cross-cut logo to the photoelectric eye moment To the control computer, the control computer controls the cutting time of the cross cutter so as to accurately cut the corrugated cardboard at the boundary of the pattern.

At present, cross-cutting machine manufacturers at home and abroad can easily add this function. Cross-cutting accuracy can be controlled within 1mm. The same principle applies to computer slitting and computer crosscutting. The gravure printing product has the characteristics of bright colors and high gloss. In the printing of high quality packaging, gravure has a unique advantage. This kind of preprinting method is increasingly favored by people.