Three Factors Affecting the Printing Quality of Corrugated Boxes

Corrugated carton packaging has developed rapidly in recent years, and printing quality is a major technical problem during carton processing. How to print out high-quality carton products with ordinary printing presses mainly depends on the following three aspects.

Plate selection

Corrugated box printing plates, mainly flexographic, rubber plate, screen plate, etc., of which the use of flexographic and rubber plates is the most widely used. The flexo plate is made of plastic soft material, which has the advantages of soft texture, high printability, clear text, and poor destructiveness to corrugated cardboard. Compared to flexographic plates, flexographic plates have high hardness and low imprint resistance. However, their low cost, economical price, convenience in hand or machine engraving, and their high occupancy rate in ordinary carton fields. Therefore, after receiving the order printing, according to the actual situation, we should use the flexo printing for the products with high requirements for patterns and characters, large field printing area, and large batch quantities; the requirements for pattern and text are not high, and the batch size is small. Ordinary carton, generally use offset printing, to achieve economical and practical purposes.

Clearance adjustment

The adjustment of the size and pressure of each roller gap in the printing press is a key issue in ensuring the quality of printed products. Due to the misadjustment of gaps in guide plates, imprints, etc., some quality problems that are difficult to avoid occur, such as the appearance of thick lines, dots, writing blur, edge ghosts, dirty edges, white spots, overprint deviations, etc. defect. This requires the operator to adjust the size of each gap based on the actual thickness of the plate.

The first is the adjustment of the ink roller and the anilox roller. There should be no gaps in the adjustment here, and the pressure adjustment is difficult to determine. The pressure can be put into a 80mm x 200g ox cardboard strip, which is suitable for pulling. If you pull easily, the pressure is small; if you do not move, the pressure is too great. When the printing area in the field is large or the cardboard paper is thick and not smooth, the pressure can be appropriately reduced, so that the ink layer of the anilox roller can be thickened to meet the large area of ​​ink supply; when the writing is small, the network cable Fine prints should be slightly increased pressure, reduce the amount of ink supply, to achieve clear printing purposes.

Secondly, the adjustment of the gap between the anilox roller and the plate roller, where the size of the pressure directly affects the printing quality of the printing product. The gap pressure should be adjusted according to different plates. Offsets are more stressful than flexo. The adjustment of this pressure gap must be the same at both ends of the anilox roller and the plate roller, otherwise it will affect the printing quality and damage the printing plate. The specific method of operation: for the pressure type or spiral hand type printing machine, should pay great attention to, can be used 6mm-8mm rule to debug, first open the printer run, ink, slowly pressurizing, with the entire layout completely It is based on ink. The pressure of the flexo plate is light, and in the ink transfer process, the plate material is not deformed under pressure as much as possible. For those who don’t know how to put ink on the surface, do not use more pressure to solve the problem. Instead, apply double-sided tape to the bottom pad to achieve the required thickness. This will reduce the pressure on the entire printing plate and improve the printing rate. Excessive pressure is prone to defects such as ghosting, blurred writing, ink deposits, burrs, and uneven brightness. Therefore, in actual operation, it is difficult to achieve high definition and good quality prints without good technical quality and operating experience.

Again, it is the adjustment of the gap between the printing plate and the embossing roller. While ensuring the printing effect, it is necessary to increase the adjustment of the gap as much as possible. Because the pressure is too high, the strength of the cardboard will be damaged, and the quality defects such as imprinting, blurring, and the like will occur. In actual operation, since the flatness of the corrugated cardboard and the smoothness of the paper are inconsistent, it is difficult to do this during the printing process. Therefore, it is required that the flatness of the cardboard be controlled as much as possible during the production process of the cardboard board to meet the printing requirements. For more than two-color overprint products, the requirements are even higher. If the printing pressure of the preceding color is too large and the color is dark, problems such as unclear printing and incomplete graphics will occur. Printing pressure, adjusted to the best effect.

Use of guide bars

Offset strips or die-cutting elastic strips play a very important role in printing, especially in the use of print products with small specifications and small print area. It is an effective way to solve overprinting; The length of the guide bar is equal to or greater than the width of the cardboard. It is advisable to stick the guide bar on both sides of the printing plate and print it on the cardboard cutting edges to enable the cardboard to be fully controlled during the printing process, effectively avoiding overprinting, printing and cutting. Do not wait for the issue to occur.

(Author: Dai Hualiang door Long Tong Shandong Huayu Group)

Corrugated Boxes June 2005 issue