At present, there are four methods for printing equipment using water-based ink in the corrugated box industry, and their characteristics are different. The first is a single-chain printing method. This printing method can only be printed without slotting and die cutting. The second is the commonly used printing slotting and round press die cutting production methods, this method uses the ink on the printing, after slotting or die cutting, just glue (pin box) can be formed. The third is the use of automatic printing slot, folding adhesive (stitch box) production method, this machine is used for folding forming under the ink printing system, is a one-time molding machine. The fourth type is the more advanced printing and round press die cutting method. Its feature is multi-color printing, high precision equipment, and printed products can achieve color printing effects, especially for the sale of color paper boxes. package. In the above methods, the common feature is the use of ink printing, the printing principle and equipment structure are basically the same, but the number of printing colors, the number of screen lines, and the process equipment are different. The printing process is affected and constrained by many aspects and factors. Many problems cannot be solved simply by the operator. Only through cooperation from all parties can we minimize and avoid unnecessary problems that arise in production.

Knives and the longitudinal slot opening size allowed pressure line, producing the print position is incorrect

Analysis of the reasons: Due to the sizing and pressure lines not being adjusted according to the requirements of the technical drawings, the length or width of the cardboard manufacturing dimensions is deviated, which ultimately affects the printing position.

solution. First of all, according to the manufacturing dimensions of the drawing, the dimensions of the slot or the press line should be adjusted. The exact position is required. Then, the position of the plate is re-adjusted according to the exact size and position, and the deviation caused by the wear of the slot or the press roller is checked.

The layout of the printing plate is inaccurate, causing the plate to be readjusted

Reason analysis; due to the unclear location of the trapping and local printing plate position, the error in typesetting is large, and the printing position is obviously biased in actual production. The current printing equipment is basically a drum type printing, and the typesetting is on the plane, and it will inevitably produce a vertical position error, and it also causes shrinkage problems due to the size of the printing pressure.

The solution first draws a normal percentage shrinkage when making a 1:1 ink map. When printing typesetting, the print version is strictly adjusted according to the ink map position. When the color registration accuracy is very high, the "crosshair" typesetting method should be used, and the crosshairs of the printing plate and the ink map should be aligned. If necessary, a magnifying glass can be used to check the deviation.

Print ghosting and leaking problems

The original group analysis; these two problems often occur in the production process. Ghosting around the printed pattern or text is caused by the excessive pressure of the anilox roller and the printing plate; ghosting occurs at the front edge of the printing because of excessive pressure between the printing roller and the platen roller. The printing of the large area through the bottom and the leakage of white are caused by the insufficient pressure of the printing roller and the embossing roller. These two problems are caused by the opposite pressure.

Solution: Printing ghosting problems should adjust the gaps and pressures between the texture, rollers, and plate rollers, commonly known as pressure. The ghosting is due to the excessive pressure, and the anilox roller squeezes the printing plate (referring to the flexographic plate) to deform. Therefore, the gap between the two rollers must be increased to reduce the pressure. Printing leakage problems should be adjusted between the gap between the roller and the impression roller and pressure, commonly known as downforce. Since the gap between the plate roller and the embossing roller is too large, the printing in a large area may be untrue, which requires an increase in downforce. In addition, the unevenness of the printing plate, the quality of the plate lining, the hardness of the plate, etc. will all affect the above-mentioned problems, and local adjustments should be made.

Multi-color printing is not allowed

Analysis of reasons: Overprinting problems are common in the printing industry. Because it is a multi-factorial component, it is not easy to solve problems. First of all, the accuracy of position and accuracy of the multi-color printing slot machine itself is a direct factor. Followed by the adjustment of the feed roller, the pull roller, the use of the traction belt, the arrangement of the printing plate, the accuracy of the printing plate, and the problem of the warping of the cardboard, all of which will result in overprinting problems.

Solution: Since overprinting is composed of multi-color printing, it is inevitable that the position of the printing roller on the various printing slot machines is relatively small; indeed, this requires the equipment department to adjust the printing position to ensure that the error is at the minimum limit. First of all, since the initial printing has an effect on the thickness of the board, the roll portion of each color should be slightly larger than the previous one so that the pressure exerted on all the colors is equal. Secondly, there are feed rollers and draw rollers at the front and rear of each printing. The adjustment of these two rollers is very important, especially when the width of the paperboard is too narrow, attention should be paid to adjusting the gap and position. In case of local color registration, two traction belts should be added at the edge of each printing plate to ensure that the cardboard is steadily over-printed. Furthermore, due to the different degree of warpage of corrugated cardboard, it has absolute influence on overprinting. If necessary, cardboard should be replaced again, but it must be flat.

Inconsistent print colors

Reason analysis: Inconsistent printing color means that the board is not evenly printed along the longitudinal or transverse direction of the machine after printing. The reason for this problem is mainly due to the different colors at the two ends of the horizontal printing. One side is lighter and the other side is darker. There is an unfavorable circulation of the ink system, insufficient ink flow, and uneven transfer of the ink transfer roller.

Solution: The uneven horizontal color is caused by the difference between the gap between the rubber roller and the anilox roller, the anilox roller, and the plate roller. Therefore, to adjust the gap between these three rollers, both ends must be kept parallel. Because the printing slotting machine is centered, such as the production of narrower cardboard, the roller and the anilox roller will wear faster, and the two ends wear less, the result after printing is not the same, if the two ends of the color Obvious inconsistency, you need to repair or replace a roller. The non-uniform color in the longitudinal direction is caused by the insufficient ink flow and insufficient ink supply. Therefore, it is necessary to add a small amount of ink to the machine to run idle to allow the ink volume to be fully recycled before production. This will reduce the occurrence of problems in this area.

Corrugated crushes when feeding or printing

Analysis of the reasons: This is caused by two aspects. One is that the gap of the feed roller (printing slot machine) is too small, lower than the thickness of the original paperboard, and the corrugated file is crushed before printing; the second is the printing roller during the printing process. Excessive pressure caused significant crushing of the corrugated area.

The solution; the gap of the feed roller should be determined according to the thickness of the corrugated board, which is basically 0.5mm lower than the thickness of the original board. If the gap is too small, the corrugated fiber is destroyed, and the physical strength of the corrugated box will be affected. After the gap is too large, the cardboard will not be able to travel at a constant speed, resulting in the printing position being not. Pay attention to adjusting the gap between the printing roller and the embossing roller during printing. At present, most of the corrugated cartons use flexographic printing, and the printing methods use light pressure and kiss-type printing. The pressure must not be too great. If the pressure is too high, the corrugations in the printing area will be crushed and the carton performance will be affected. Therefore, the adjustment of the gap between the printing roller and the embossing roller is very important, and there is no significant depression in the printed part of the hand.

Corrugated box manufacturing process should not damage the corrugated, it is different from the general sales of carton packaging, because the corrugated force is a multi-faceted, once the destruction of UV-type corrugated, this corrugated is meaningless.

In summary, these printing problems are only the most common problems. Others, such as the indistinct writing, distortion, excess printed traces after printing (commonly known as “printing”), streaking of printed marks, and the inability of ink colors to achieve desired results, have also been analyzed. However, in addition to objective factors, such as plate material, plate liners, inks, and even the quality of corrugated board, have a direct impact on the printing effect of corrugated boxes. Therefore, we must use high quality raw materials to ensure the high quality of printing. In order to solve various problems in the printing process, operators who have practical experience are also required. First of all, they must have a certain level of theoretical knowledge. For example, they must understand the principles of printing equipment and manufacturing processes and the process specifications to fully understand the printing process. The relationship between the four parts of the rubber roller, the transfer roller (anilox roller), the plate roller and the embossing roller in the system, how to be proficient when there is a problem, and the correct adjustment of the corresponding part can be quickly resolved. Secondly, we must also be good at summarizing the actual operations. Under what circumstances should we adjust which parts and requirements; and indeed, it is not easy for general operators to do so. As a good stop worker, we must be good at finding problems and solving problems in time so that production efficiency can be improved. All in all, the printing problem cannot be separated from the various conditions mentioned above. As long as we fully understand the principle of printing, the printing problem will be solved.

Corrugated Boxes June 2005 issue

(Special Author / Wu Cunsheng)