Gravure Cartons: New Fashion for Packaging (Part 2)

Performance ratio better than offset printing

Gravure printing is direct imprinting, that is, the printing plate roll and the substrate are rolled under pressure, and image transfer occurs rapidly. The gravure printing ink layer is thick, the dot is clear, and the exquisite degree is almost equal to the offset printing. The gravure preprinting does not have to bear, and the CEI3 product will have quality problems. However, the gravure preprinting process is absolutely superior to the offset printing in the strength of the carton. Experiments have proved that the strength of the equal weight of the paper distribution structure and the preprinted carton of the web are higher by 10%. The offset sheet is printed on the corrugated board and the corrugated board is affixed. The gluing machine uses cold glue. When the pressure roller presses the board, it will press down the corrugation peak when the pressure is applied to the board to reduce the compressive strength and stacking strength of the corrugated box. The loss of offset strength can reduce the weight of the corresponding paper while maintaining the required strength for the gravure preprinted configuration. The base paper generally accounts for 60% of the total cost of the carton, reducing the weight can reduce the cost by 10%. The method of reducing the grammage is limited in the offset printing machine. The whiteboard paper less than 200 g uses the offset veneer, and after the box is formed, there is an obvious “cooking board” stripe. Cardboard Roll-to-roll Making of corrugated cardboard uses starch-based hot glue. The steam is used to preheat the cardboard quickly. The hot-end hot-plate applies pressure to the paperboard plane. It does not damage the corrugations, nor does it form "sawboard" stripes. If the efficiency of gravure preprinting is included in the cost, the total cost of the carton will also drop.

The domestic gravure printing carton was actually developed by the inspiration of foreign flexographic preprinting technology. Today, with the rapid changes in new technologies, there are many advanced packaging concepts worth learning from. ADALISCORP Corporation of the United States is committed to the optimization of corrugated cartons and has introduced a carton reinforcing belt called Sesame, which is suitable for the preprinted cardboard process. A filamentous PVC precoated with a hot melt on the cardboard line is stuck to the corrugated carton layer on the cardboard line at a high temperature, increasing the strength of the carton by 20%. North American dairy product packaging companies have started to adopt it.

Speaking of advantages

As with flexographic preprints, gravure preprinted cartons have the following advantages:
Get high-quality, high-sense color box;
Accurate barcode replication capabilities;
Better embossing effect, corrugated will not form imprinting damage, the carton will eventually get higher strength;
It can improve the production efficiency of corrugated cartons' automatic lines, satisfy long orders with short construction period and large output, and can maintain constant color and print quality:
The process is simple and convenient for production management.

Compared with imported flexographic preprinting machines, domestic gravure preprinting machines do not have sufficient machining accuracy, and some common problems are exposed in the production process of carton factories. With the help of the printer factory, the corresponding solution was found:

Wrinkling: Pre-printed paper rolls with a high basis weight have a tension of about 50kg, which is more difficult to control than films (10kg) and tissue (25kg). When the moisture is uneven or the thickness is not uniform, a greater tension change will cause the paperboard to swing laterally and form a wrinkle on the surface of the printed product. The preheating device for the paper concave machine can help reduce the tension change caused by water loss (when the water content is too low, the humidifier needs to be installed); if the offset smoothing roller is added, it will help the paper roll to go as far as possible Flatten, reduce the swing.

Ink draw: In addition to taking the previously mentioned temperature resistant inks and varnish, the latest air-cushioned heat plate heat transfer control system reduces the thermal temperature and strength of the paperboard as it passes through the hot end. The process is that the air spray channel is arranged at the gap between the heating plate and the paper board, and the air can be sprayed in an instant to form a gas film to hold the paper board, so as to avoid the defects such as scratches, inks and the like caused by excessive pressure on the paper board. This system has been developed by the United States Magui company and has been practically applied.

Lubai: Mainly due to dust on the surface of the paper roll and blocked by ink. In the field printing group, dust and explosion-proof electrostatic ink-absorbing devices are separately installed to blow air and dust to improve the ink-in effect and reduce the dot-loss phenomenon.

Spiral winding: Because the winding tension of the paper machine is inconsistent with the unwinding tension of the printing press, pre-printed paper rolls will form a rewind effect that is tight, tight, and tightly closed inside the front, which is the cauliflower phenomenon. When the paper roll was moved, the outer cardboards scattered and affected the material transportation. The unwinding crosscut on the cardboard line is also inaccurate. The use of PLC computer corrective device can be used to control the tape tension taper. It can measure the paper tension immediately after unwinding, and adjust the winding tension accordingly.

Incomplete edges: The edges of the cross section are not uniform, and the backup roller (receiving rubber roller) can be added to remove air from the paper roll and eliminate static electricity on the surface. When the paper roll receives the material, the roller device is tightened to reduce the edge swing. The installation of a PLC-based correction device also helps to alleviate uneven edges. Another method is to rewind offline.

Roll overlap: If the roll is improperly overlapped during printing, it will cause downtime and affect the consistency of the printed product. Zero-butt connection can be used to pick up the paper without interrupting the printing process.