Principles and New Trends of Flexo Printing Technology (Part 2)

Third, flexo design considerations

At present, China's flexo products are at a very low level. Print quality is mainly low, thick, and simple. Fine multi-color printing is not easy; at the same time, the scope of application is small. The main lines and field of printed text are printed on the spot. a lot of. Restricting the application and development of flexo printing in China, in addition to equipment and technical issues, another major reason is that designers do not understand the characteristics of flexographic technology, resulting in a lack of communication between design and printing, and can not fully play the flexo Advantage.

Due to the differences between Oriental culture and European and American cultures, their product packaging has a distinct difference in design style, which also makes the flexo printing industry in the short term have a certain impact on China's development. Europe and the United States emphasizes that the use of concise color blocks and lines gives people a strong visual impact. Such products are easy to use flexo printing. China's packaging industry has long been subjected to gravure and offset printing, and it has been focusing on realism and using a large number of realistic layers. Therefore, it is necessary to use flexographic printing to pursue offset printing and gravure printing. The end users are bound to accept it. Therefore, the degree of flexo printing accepted in our country is lower than that of offset printing and gravure printing.

When designing a flexo print, you should avoid the following:

1. To avoid the design of too small text and too thin lines;
2. Avoid double or multicolor lines and text overprinting;
3. Avoid designing small anti-white characters and lines;
4. Avoid photo highlights or 1% of small outlets;
5. Avoid designing text or lines in photoshop and other bitmap software;
6. Avoid designing wide and long solids and gradients along the horizontal direction of the printing cylinder;
7. Unless you have special requirements, avoid the use of large areas on the same page as the outlets and small texts.
8. Avoid the inconsistency of operating software.

Fourth, the future development trend of flexography

1.UV technology is widely used in flexo printing

At the Flexo Summit of China Print 2005, companies such as Nilpeter in Denmark have emphasized the application and development of UV technology in flexo printing. At present, flexographic printing machines equipped with UV ink curing systems are increasing in foreign countries, and the existing flexographic printing machines are constantly being modified by UV ink curing systems. Replacing water-based inks and solvent-based inks with UV flexo inks has become a development trend and has been widely applied to both wide-width and narrow-width flexographic printers. It can be said that after the success of the water-based ink, UV ink once again promoted the development of flexo.

The UV ink has good printability, does not change the physical properties during printing, and can be used for printing with higher viscosity. Therefore, the dot enlargement in color printing is greatly reduced, thereby improving the flexographic printing quality, which improves the quality of flexographic printing in China. Photo-realistic packaging and decorating print quality is very important. From a print quality point of view, flexo printing with UV inks is superior to flexo printing with solvent inks and water-based inks. In addition, the new choice for flexographic printing is general-purpose UV inks (inks that can be applied from paper to film), and this ink has entered a practical stage in Europe and the United States.

The reason why UV flexo printing inks are widely valued and favored at home and abroad is summarized as flexographic UV inks have the following advantages:

(1) UV flexo ink is safe and reliable.
Solvent-free, non-flammable, non-polluting environment, suitable for printing foods, beverages, tobacco, alcohol, pharmaceuticals and other sanitary requirements of high packaging requirements.

(2) greatly improve the quality of flexographic printing.
UV flexo printing has good adaptability, high printing quality, no change in physical properties during the printing process, no volatile solvent, stable temperature, not easy to paste plate, stack plate, can use higher viscosity printing, strong ink, reduce the dot expansion, make up for flexo Existence of dot enlargement, high definition of dots, reproducibility of gradation, bright and bright ink, and firm attachment are suitable for printing of fine products.

(3) High production efficiency and wide adaptability.
UV flexo printing inks can be instantaneously dried and have good adhesion on different printing carriers such as paper, aluminum foil, and plastics. Products can be stacked immediately after printing, and adhesion will not occur.

(4)UV flexo printing inks have excellent physical and chemical properties.
The process of UV curing and drying is a process in which the photochemical reaction of the UV ink changes from a linear structure to a network structure. Therefore, it has many excellent physical and chemical properties such as water resistance, abrasion resistance, and aging resistance, which is unmatched by other types of inks.

(5) UV flexo ink consumption.
Because there is no solvent volatilization, the active ingredient is high, it can be almost 100% converted into ink film, its amount is less than half of the ink or solvent ink, and can greatly reduce the cleaning times of the printing plate and anilox roller, so the overall cost is relatively low.

2. Sleeve technology

The original flexo plate was to be plated on the platen cylinder after plate making, and then it could be printed. Now there is a more advanced flexo plate making technology, which can directly plate on the sleeve, and then put the sleeve on the plate cylinder. Can be printed on the work efficiency. This technology is sleeve direct plate making technology.

The sleeve carved in the laser engraved sleeve technology is a printing plate, which is pre-printed by a pre-press system and the efficiency is greatly improved. At present, sleeveless technology is commonly used for anilox rollers and laser-engraved seamless rubber rollers. The purpose is quick replacement and easy operation. For wide-width machines such as the use of cantilever shaft cores, it is easier to handle. The key to sleeve technology is durability, accuracy, weight, and in addition to price and service. These are all considerations for flexo printers.

3. Platform replacement and combined printing

In flexo printing technology, combination printing has always been a bright spot. It can easily realize the seamless joining of offset printing, gravure printing, silk printing, and flexo printing, and can add die cutting, coating, and cold/hot stamping, etc. as required. After processing. Platform replacement technology can make the above functions easier to implement, greatly save costs and space, and also meet the needs of customers.

The so-called platform replacement, as a simple example, is to replace the offset printing unit with a gravure printing unit or other similar conversion. Many parts of the original unit do not need to be moved, and only the different parts of the two printing methods need to be changed. The operation is also relatively simple and easy.

4. Servo drive solution

At the China Print 2005 exhibition, many manufacturers demonstrated the use of various non-shaft-driven servo motors on flexo presses, greatly enhancing the accuracy of the registration and color reproduction of flexographic prints.

Servo motor is directly driven. There is no spindle and differential gear system connection between each unit of the flexo printing machine, which reduces the drive link, improves overlay accuracy, and greatly improves the printing plate dot reduction rate. At the same time, the increase in errors due to long-term mechanical wear is also avoided.

At present, some wide-width flexo presses have successfully adopted this technology. The independent printing unit is driven by a separate motor to ensure the relative position of the plate cylinder of the unit is accurate, and the tension of the whole machine is ensured. The overprint accuracy of multi-color printing is improved, and there is no "black bar" phenomenon caused by vibration. The scope of machine printing and paper feeding will be further expanded, from thin film to thick cardboard. Servo drive technology can also be extended for other flexographic applications such as repeated print lengths. The first unit can print the first 400 mm with a repeat length of 800 mm, while the second unit can print the remaining 400 mm.

5. Computer Intelligence Control and Network Technology

With the development and application of computer technology, the degree of automation of flexographic printing presses has also been continuously improved. At present, there are many models with a convenient man-machine interface, using menu-based instructions to make control more efficient and faster. Once the machine fails, the system displays the error message in time, instructs the operator or maintenance personnel to find the fault point as soon as possible, and can eliminate the fault at the fastest speed and reduce the downtime.

In addition, with the development of flexographic technology, people began to study the use of Internet technology for the management and control of data and materials, such as job management, material management, substrate production length monitoring and waste recycling, and even through the network Remote monitoring: For serious faults, operators can use remote diagnostic services to consult with machine manufacturers so that they can provide timely services and solutions.

The above-mentioned new technologies and new processes will further reduce flexographic production costs, improve the quality of flexo printing, reduce downtime, and increase production efficiency. Flexographic printing will be continuously developed and applied more widely. ※

Author: Liu Jinfang Source: Wuhan University School of Journalism and Communication