Flexo Printing Solutions 14 Questions (1-6)

1 how to give flexo printing machine with anilox roller

Most prints have both solid, line, and continuous tone images. In order to meet the needs of various types of printed products, users must not take the practice of using several anilox rollers with several printing units on the flexo press. Taking the narrow-width unit type flexo press as an example, the current domestic introduction is mostly 6+1 type, that is, 6 color groups are exclusively for multi-color printing, and the last unit can be printed and can be UV-coated.

We suggest that for prints up to 150 lines, this 6+1 flexo press should be equipped with 9 anilox rollers. Four 700 lines with an ink layer thickness of 2.3 BCM (1 billion cubic microns per inch) and an anilox roller of 60° are used for printing on the gradation; three 360 ​​to 400 lines, a BCM of 6.0, and a 60° screen Rollers are used for field printing; two 200-line, BCM15, and 60° anilox rolls are used for printing and polishing. If water-based bright oil is used, 360-line anilox roller should be used, so that the oil layer is slightly thinner and will not affect the printing speed due to the problem of drying of the bright oil. Water-based gloss oils do not have the special smell of UV bright oil. The position of the anilox roller during printing can be determined through testing and comparison. The thickness of the ink layer that can be observed by the operator during the test depends mainly on the number of lines and the BCM value of the anilox roller.

2 Anilox roller should pay attention to what issues during use

Here, we refer to the anilox rollers which refer to laser-engraved ceramic anilox rollers. They are used in aerospace and aerospace high-temperature, abrasion-resistant coating materials, and are used at a certain density, depth, and certain angles and shapes. Laser engraving. This anilox roller is characterized by its high cost and wear resistance. If it is used properly, its life can be as long as several years; if it is used improperly, not only the service life will be shortened, but also the anilox roller will be scrapped.

In the process of use, the position of an anilox roll on the printing press depends on the specific print, different prints, and the position of the anilox roll is different. Therefore, the wire roll is often replaced during printing. At present, narrow-width machines use mostly solid steel anilox rollers, which are very heavy. When mounting the anilox roller, care must be taken to avoid touching the surface of the anilox roller against other metal objects. Because the ceramic coating is very thin, permanent damage can be easily caused by a collision. During the printing and cleaning process, the ink should be prevented from drying on the anilox roller. The special detergent recommended by the water-based ink manufacturer should be used. The steel brush should be used for brushing, and the cleaning should be clean and thorough. And develop a habit of using high-power magnifying glass to observe the anilox roller nets. Once ink is deposited on the bottom of the net and gradually increase, it should be promptly cleaned. If the above method does not work, ultrasonic or sandblasting treatment can be used, but it must be done under the guidance of the anilox roller manufacturer.

Under normal use and maintenance conditions, there is no need to worry about the problem of anilox roller wear. The main component of the ink-transfer system that is subject to wear is a squeegee. Compared to this, the wear of the anilox roller ceramic coating can be described as negligible. When the anilox roller slightly wears, the ink layer becomes thinner.

3 What is the miniature version?

As we all know, flexographic printing has a phenomenon of unidirectional elongation along the direction of printing. The ratio of elongation depends on two factors. One is the diameter of the platen (including double-sided tape), and the other is the printing. Version body thickness. The larger the plate cylinder diameter, the smaller the plate thickness and the smaller the elongation. A concept that needs clarification here is that the elongation phenomenon is not caused by pressure in the printing. In fact, the flexographic plate has already undergone elongation deformation when the double-sided adhesive is stuck to the plate cylinder. Therefore, when designing the ink map, it is necessary to make a miniature version. The proportion is based on the thickness of the actual material used and the actual printing length. If you use computer-based printing, you only need to give a unidirectional reduction instruction before designing the ink color separation. If you use hand-made film, you need to use a deformation machine, you can also get a scaled-down version of the film.

4 What is the relationship between the number of printing screens and the number of anilox roller screens?

In many articles introducing flexographic printing technology, the ratio of the number of printing screen lines to the number of anilox roller screen lines is set to 1:3.5 or 1:4. Based on practical experience and analysis of award-winning products reviewed by the American Flexographic Printing Technology Association (FTA) in recent years, the author believes that this figure should be higher, about 1:4.5 or 1:5, for individual fine prints. Maybe this ratio is even higher. The reason is that the most difficult problem to solve when printing a gradation plate with a flexographic printing press is to enlarge the dot, and use an anilox roller with a higher number of screen lines, the ink layer is thinner, and the dot enlargement and deformation is relatively easy to be controlled. If it is found that the ink color is not strong enough during printing, a water-based ink with a higher color concentration may be used to ensure the quality of the printed product.

5 How to Design a Flexographic Ink Image for Easy Overprinting

In the printing process, one of the key pointers people often pay attention to is overprinting, because the waste generated due to overprinting is often a large proportion of the total waste. Although flexo printer manufacturers have provided a good basis for accurate overprinting during design and processing, automatic monitoring systems also provide protection for accurate overprinting, but the operator's skill level and skill level also have a great influence on overlay accuracy. . If you are designing ink maps, you can make some adjustments for overprinting, which can greatly reduce the difficulty of printing and reduce the scrap rate. The easiest way is to design the original ink as far as possible to use anti-white characters, or to hollow out between the two colors to form a reverse white outline, you can also cover the edge of the two colors over the third thicker Dark outlines, for printing of finer prints, trapping technology can be used. The amount of trapping depends on the accuracy of the press, the quality of the paper used for the print, and the level of the operator. Trapping processing is easy to implement on calculators. If you do not have a calculator, only ready-made color separations, you can use a special trapping processor (Trapping Modifier), enter the value of the trapping amount, the machine will automatically generate a trapping Imprinted film. If there is no trapping processor, a transparent spacer can be placed between the color separation film and the copy film, and exposure can be performed with a single point light source copying machine. Similarly, a film with similar effect can be obtained.

6 What are the requirements for the production of flexographic film types?

When the flexographic plate is exposed on the front of the plate making machine, to ensure the quality of the film and the flexographic printing surface, the plate making machine is equipped with a vacuum pump to vacuum the film. At the same time, the film must be rough (matte) on the side close to the flexographic plate. This prevents the presence of air bubbles between the film and the flexo plate and affects the quality of the flexographic printing surface. The pressure strip used for the press roll and the flexographic plate edge is also a type with an indentation and lateral air conduction. In addition, there are specific requirements for the blackness and transparency of the film.

(to be continued)