Flexo unit for online finishing and sheetfed offset
In the packaging and printing industry, most sheetfed offset presses are equipped with a flex-plate glazing unit. This is also the case in the area of ​​part printing. The offset printing plant began to use flexographic printing technology in this way. With a chambered doctor blade and an anilox roller, it can be glazed, and it can also accurately cover light locally. The flexo unit is located behind the offset printing unit and is usually used for on-line glazing of prints or for partial glossing. When the flexographic printing unit is located before the offset printing unit, the surface of the printing material can be pre-treated, for example, white metal varnish is applied on the metal paper or transparent plastic, and the flash effect is printed in the subsequent process using the color offset printing method.
The advantages of offset printing are the high quality of the print and the low cost of prepress and plate. The feature of flexographic printing is that thicker coatings can be formed with simpler processes that can accommodate printing of larger pigment particles. Flexographic printing inks are similar in viscosity to thin gravure inks, and can form thicker and more uniform ink ink layers than offset printing. Different anilox rollers are used to change the ink film thickness. The particle size of the metallic pigment for offset printing is 3.5 [mu]m, and the metallic pigment particle size for gravure and flexographic printing is 8 to 9 [mu]m. These flexographic printing units are commonly used to coat opaque white coatings, milky white coatings, metal coatings, foam printing and scattering applications, and UV coating.
Sheet-fed flexo printing machine for offline finishing
Sheet-fed flexographic printing presses are often used as coaters in corrugated board printing. The new sheet-fed flexo printing presses for packaging printing and finishing are equipped with a carious tooth transfer system to ensure precise transfer between the printing unit and the printing unit. Printing materials range from thin paper to cardboard with a thickness of 1.25 mm.
The design of the sheet-fed flexographic press is the same as that of the sheet-fed offset press. There are two flexographic printing units in the offset printing unit and can be used as a glazing machine for coating UV coating or effect coating. Some special coating methods require thick coatings such as foam printing, fragrance printing, barrier coatings, gum coating, iridescent printing, and thick pigment coatings for metallic effects. This model can accurately control the amount of coating.
High-quality packaging requires advanced finishing and requires multiple coating units/flexo printing units. If five or six printers with an on-board optical unit are used for coating or multiple coating, they will soon become a bottleneck in production. Off-line sheet-fed flexo printing presses can also enter the high-quality packaging finishing field.
Sheet-fed offset press and multi-finishing UV technology
Printing business using UV technology has increased nearly 3 times. UV technology represents the highest level of quality, and it has high efficiency and good consistency when coating. Of particular interest is the UV coating, which has a high gloss value and excellent scratch resistance. Under UV radiation from the printing press, the UV ink and coating film cure within a fraction of a second, and the printed sheet can be directly processed. The problem of printing dusting and solvent evaporation naturally goes away.
However, it is not simply to buy the equipment to master the UV printing and finishing process. Printers using UV technology need to accumulate experience to digest the increased investment costs, materials, and energy costs. In factories where traditional printing is mixed with UV technology, it is also necessary to plan the conversion time and adjust the printing parameters. UV prints also have odors, which also needs further improvement. However, the advantages of UV are far more than disadvantages. A wide variety of non-absorbent printed materials is a real challenge for parts printing, packaging, and label printing.
Introduce mixed operations
UV printers need to be adjusted according to the special requirements of the printing factory and its products. Even for small-format offset printing, the powerful UV technology is equivalent in all respects to the UV technology used in medium and large format offset printing. Manufacturers who are new to UV are best to start with UV and traditional printing mixing operations. The original finishing coating will be used as a UV printer. In the future, the waterless UV sheet-fed offset presses will also exhibit the advantages of finishing in non-absorbent printing materials. This printing method can image CTP waterless offset printing plates and CTP traditional offset printing plates on the same plate-making machine. No chemical development.
The demand for plastic films is also increasing. In the past, screen printing dominated this market share, and today's offset printing companies have also entered this high-sales market because of UV technology. However, screen printing now also uses UV technology to compete fiercely with its strong competitors. Due to the problem of dimensional stability caused by the high temperature generated by the UV beam generator that jeopardizes printing and finishing processes that require precise overprinting, the UV system requires a significant reduction in the amount of radiation and curing in a nitrogen-filled inert gas chamber.
Online double coating
Double coater is a kind of machine that replaces pure UV machine. The double coater can be coated on a machine with a much cheaper conventional ink using a UV coating device. It is also possible to use some special color inks that have been tested. However, the prerequisite is that there are two coating units on the press and the drying section is located between the two coating units.
Hybrid technology worthy of careful consideration of the finishing process
The use of a sheet-fed offset press can use either traditional mineral oil based inks or mixed inks, but the printing press must be modified accordingly. Since the surface chemistry of the mixed ink is ultimately the same as that of the UV ink, the disadvantages of poor coating adhesion and impurities in the bright layer must be avoided.
High gloss and matt effects can be achieved in one press run. The first printing unit was printed with the mixed colors, and then the ink was dried on a UV intermediate dryer. Individual elements are then coated with conventional inks and conventional printing overlays, followed by final UV coating and hardening. In all graphic elements printed with mixed inks/varnishes, normal inks interact with UV coatings. A matt, glossy, structured surface is formed that resembles a plastic coating that is both visible and touchable, exhibiting an interesting design feature. From this point of view, the options for different combinations of effects are still varied and varied.
It can be said that the hybrid technology is a way of UV technology, but also a system. Manufacturers who cannot fully use UV machines in part printing use hybrid technology.
Source newmaker
