Corrugated boxes are logistics packaging containers that integrate transportation and sales functions. Consumers continue to put forward new requirements for the appearance, environmental protection and function of commodity packaging, making the carton industry continue to use technological innovation to meet the comprehensive requirements of the external packaging quality and cost of the terminal market.
Only from the perspective of printing and processing to explore the carton packaging industry, the domestic market can obtain perfect but not beautiful, moderate but not excessive high-quality outer packaging. China’s printing industry has a large number of manroland, Heidelberg, and KBA offset presses, including a new generation of presses that directly print high basis weight (above 400g/m2) and micro-corrugation, which can meet the printing of high-quality, short- and medium-sized cartons/boxes; It has nearly 600 unit-type flexo printing machines, which can meet the printing of medium and long versions of cartons/boxes; it has many flexographic pre-printing/gravure printing machines, the printing quality is close to offset printing, and it can also meet the printing of large-scale color boxes/boxes.
In addition to direct offset printing for micro corrugated boxes, general corrugated boxes need to use offset printing and mounting box making method. This method has simple equipment, complex procedures, and long drying waiting time between printing and mounting processing (usually about 48 Hours); the printing process is not environmentally friendly, and the processing process consumes a lot of energy. The basic process flow is: single-sided corrugated cardboard production + offset printing surface paper → laminated synthetic cardboard → die-cutting slotting → bonding nail box, the exquisite effect obtained by offset printing veneer carton is at the expense of carton strength, because When the facing paper and single-faced corrugated board are pasted on the veneer, the corrugation is deformed under compression, which will reduce the compressive strength of the carton by 10%, and the automatic corrugated production line can not fully utilize its advantages and can only play a semi-automatic role. In order to make up for the loss of strength, the paperboard has a high basis weight, which is inconsistent with the “low basis weight and high strength” process advocated by the industry for many years.
Only considering the printing effect, offset printing is still at the apex of the pyramid, and the number of screen lines up to 250 lines/inch is far ahead of flexo printing. This is also the fundamental reason why businesses have always adhered to offset printing. But in fact, some domestic flexographic pre-printing production lines have reached 150 lines/inch, and the visual effect is comparable to offset printing. The carton is mainly used for transportation. Usually the product display function is reflected at a distance of 1m from the consumer. At this time, the effect of flexo printing is completely acceptable. From the perspective of carton processing technology, carton manufacturers are more optimistic about flexographic direct printing.
Flexo direct printing
The production process is corrugated cardboard production → cardboard direct flexo printing → die cutting and slotting → glued nail box.
Foreign countries have always admired flexo printing for two reasons: one is that flexo printing uses water-based inks, which is more environmentally friendly; the other is the flexibility of subsequent printing processing, the speed of plate change is fast, and the scrap rate is very low. Flexographic post-printing is not only suitable for large-volume and long-order printing, such as corrugated box printing for beer, beverages, and food, but also for small-volume short-order printing, especially for expensive large-size computers and home appliances. The biggest advantage of post-printing is that it can be in-line production, that is, printing, glazing, die-cutting, slotting, gluing, and strapping can be completed on one machine. The newly built corrugated box factory only needs to be equipped with a corrugated board production line and a flexo printing machine to be put into production, while the use of offset printing and pre-printing methods requires multiple equipment.
There is a certain degree of excessive packaging problem in my country’s packaging market, which hinders the promotion of flexo printing technology. However, there are still many factors that will promote the continuous promotion of flexo printing technology in the corrugated box industry.
(1) Frequent product revisions or increased versions, such as holiday promotions, small package packaging, etc., to miniaturize printing batches. The flexographic method of printing directly on corrugated cardboard has the advantages of fast speed, low cost, and good quality.
(2) Brand recognition, corporate image and group design are becoming more and more popular. Many multinational companies not only require their printing quality in China to be consistent with the parent company, but also have requirements for printing methods, which will undoubtedly promote the flexo printing of the packaging market.
(3) The market is developing towards intensive and large-scale development, and customer inventories are decreasing. Increasingly, packaging materials can be used directly after delivery. Flexo printing has a faster customer response speed.
Pre-printing is to first print the face paper roll to roll, and then send the printed face paper to the face paper station of the corrugated paper machine to produce corrugated cardboard, and then process it into a carton through the subsequent process. The pre-printing method can produce medium and high-grade cartons, which can not only meet the requirements of exquisite printing, but also reduce the strength of corrugated cardboard as little as possible. Pre-printing is divided into gravure pre-printing and flexo-printing pre-printing. Due to the expensive printing plates and fast printing speed, the print volume of pre-printed cartons generally cannot be less than 500,000 boxes, which is not suitable for small and medium customers and short-run jobs. European and American flexographic corrugated boxes account for more than 80%-90%, but flexographic pre-printing only accounts for 30% or less, and the development speed is slowing down. Pre-printing is a new technology in our country and has a certain development space.
As an advanced printing process, pre-printing requires the use of advanced equipment and technology. At the same time, higher requirements are put forward for the corresponding materials, which not only require the corrugated cardboard to have high edge pressure strength and burst resistance, but also require the smoothness of the paper to achieve good printability. After comparison and testing, Budweiser finally chose 185g/m2 coated cattle cardboard from Finland M-Real. This low-weight, high-strength paper has greatly reduced the cost of cartons.
The protective performance of the pre-printed corrugated box is more prominent, which not only can better protect the corrugation from damage, but also increases the compressive strength of the corrugated box by 10% compared with the previous one, which can better guarantee the quality of the product during transportation. In addition, the pre-printed corrugated carton has high printing accuracy, clear and exquisite pictures and texts, and rich and saturated colors. After pre-printing and laminating, the effect of laminating can be equivalent to that of offset printing, and it can still be maintained after long-distance transportation, storage, and handling. Good printing quality. The pre-printing process is especially suitable for the printing of outer packaging boxes of milk, beer and high-end beverages.