Discussion on Flexo Printing Technology of Corrugated Board
With the development of social economy and the improvement of national living standard, people pay more attention to the perfection of commodity packaging. Corrugated carton packaging with its unique function in the whole goods packaging industry accounts for a growing proportion, and the key technology of corrugated carton is ink printing. This article will discuss how to improve the quality of ink printing by improving the equipment.
1.The Treatment of Printing “Unprinted Patches”
Unprinted patches in the corrugated carton production is the most common problem that is difficult to be eliminated, the reasons are:
(1)poor ink absorption performance ;
(2)printing plate dirty;
(3)scraps of paper, dust on the cardboard.
The conservative way to deal with these problems is to change the box manually or increase the frequency of manuale rasing. These methods will play an objective role to some extent, however, the improvement effect after the box changed is not obvious, and easy to cause efficiency decline; Erasing can also cause water, electricity, artificial waste.
In the process of equipment installation, maintenance and management, through long-term observation and analysis, the author believes that the key to solve the problem of printing unprinted patches lies in dust removal, and the main source of dust is generated by single-blade paper separation.
Based on this situation, two years ago, the author has respectively installed electrostatic suction dust absorption device after the computer crosscutting knife and printing machine feeding. Use a hair dryer in front ofthe computer crosscutting knife, to blow out the paper scraps hidden in pits when the single blade cutter is divided into paper, and then use the electrostatic air suction and dust absorption device to suck away the paper scraps at the paper receiving frame after the computer crosscutting knife. At the gap between the feed apron and the feed wheel in the feed section of the printing machine, electrostatic dust is used to absorb the dust on the board, so as to keep the printing surface clean and dust-free. In this way, when the product enters the printing roller, there is no obstacle to ink loading and ink absorption is even.
After such improvement, the printing effect of the product has been greatly improved, and the phenomenon of unprinted patches caused by dust has been fundamentally overcome.
2.The Treatment of Overprinting Location Moving
Now commodity packaging pays more attention to the artistic quality and three-dimensional sense of patterns, so that consumers can feel the perfection of commodities purchased from the outer packaging. To achieve this purpose, multi-colored printing must be adopted in packaging printing, that is, multi-colored overprinting.
In the overprinting process, often appears overlapping between the latter color and the former color or position dislocation, resulting in printing patterns can not reflect the product packaging designeffect, or even widely divergent, completely destroyed the image of the product.
In view of this special problem, our factory after a period of in-depth investigation and research on the spot, from electronic control reaction speed to mechanical tolerance accuracy, carried out a detailed calculation, improved the existing equipment, and set up relevant equipment maintenance measures.
(1) Improve the Precision of Printing DrumPhase Positioning
The phase positioning of the printing drumis controlled by encoder and counter. If the accuracy of counter is too low, the position of encoder will be inaccurate. When printing, the position will be dislocated, generally, counter reaction speed is 3K, but the positioning error is plus or minus 1mm. After discussion with Taiwan electronic control company, 5K counter was produced, which reduced the positioning error of printing drumto ±0.4mm.
(2) Regularly Lubricate and Inspect theTransmission Machinery
In the process of paper feeding, if the transmission machinery can not maintain a good and smooth operation, each time the position of the cardboard will change, resulting in printing and overprinting dislocation. Therefore, it is very important to maintain and test the equipment correctly. We have developed a daily pre-startup test running checklist, which includes lubrication maintenance, and the wear limit of the paper feeding wheel, paper feeding ring , those unqualified must turn overgrinding, change the feeding roll or replacement, so as to overcome the dislocation, oblique position and other phenomena of cardboard in the processof transport.
(3) Adopt Suction Feeding System
The traditional printing machine uses the upper printing, which can only use the paper wheel to transfer the cardboard, butthe new printing machine uses advanced technology of the lower printing, the upper suction to transfer cardboard. Suction feeding paper uses wind power to adsorb the cardboard on the transmission wheel, its suction is even, not dislocation, and oblique position, and it will suck the curved board to flat, enabling an accurate target on printing, making ink more even and flat.
3.The Problem of Ink Feeding
In addition to paper and offset problems, there is also the technical problem of the ink roller.
The inking rollers are all anilox rollers. In high-standard carton printing, anilox rollers used above 250lpi, its meshholes are most likely to be blocked by ink residue, resulting in uneven inking, insufficient ink quantity and shallow ink. The traditional method is to use water to clean the ink roller, but no matter water scrubbing the ink roller or detergent scrubbing method, the effect is not ideal. A new ink roller used less than a month, the effect is not as good as before.
After a long period of trial , we find that the following methods can effectively solve the problem of poor ink printing:
①Add filter net in the ink bucket to prevent ink particles from entering the ink roller.
②Regular (generally half a month) use anilox deep cleaning agent, cycle cleaning.
③Wash the ink roller with dripping water in circulation every day after work, and dialyze the mesh hole of the ink roller with 60-100 times magnifying glass. No ink residue is allowed. If part of residual ink exists, immediately scrub it with deep cleaning agent.
Through the above methods, the ink effecton the ink roller can always maintain good.
The above printing technical problems are crucial to the quality of carton products in actual production. Through the understanding and improvement of equipment, as well as good maintenance, we can produce products that satisfy customers and improve the comprehensive benefits of the enterprise.